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{{Short description|Material composed of nanosized cellulose fibrils}}
{{Short description | Material composed of nanosized cellulose fibrils}}
{{Use mdy dates|date=August 2024}}
[[File:Nanocellulose.JPG|thumb|Nanocellulose]]
{{Nanomaterials}}
{{Nanomaterials}}


{{cs1 config|name-list-style=vanc|display-authors=6}}
'''Nanocellulose''' is a term referring to nano-structured cellulose. This may be either '''cellulose nanocrystal''' (CNC or NCC), '''cellulose nanofibers''' (CNF) also called '''nanofibrillated cellulose''' (NFC), or '''bacterial nanocellulose''', which refers to nano-structured cellulose produced by bacteria.


'''Nanocellulose''' is a term referring to a family of [[Cellulose|cellulosic]] materials that have at least one of their dimensions in the [[nanotechnology|nanoscale]]. Examples of nanocellulosic materials are '''microfibrilated cellulose''', '''cellulose nanofibers''' or '''cellulose nanocrystals'''. Nanocellulose may be obtained from natural cellulose fibers through a variety of production processes. This family of materials possesses interesting properties suitable for a wide range of potential applications.
CNF is a material composed of [[nanotechnology|nanosized]] [[cellulose]] fibrils with a high aspect ratio (length to width ratio). Typical fibril widths are 5–20 [[nanometers]] with a wide range of lengths, typically several [[micrometers]]. It is pseudo-plastic and exhibits [[thixotropy]], the property of certain [[gel]]s or [[fluid]]s that are thick (viscous) under normal conditions, but become less viscous when shaken or agitated. When the shearing forces are removed the gel regains much of its original state. The fibrils are isolated from any cellulose containing source including wood-based fibers ([[Pulp (paper)|pulp fibers]]) through high-pressure, high temperature and high velocity impact [[Homogenization (chemistry)|homogenization]], grinding or microfluidization (see manufacture below).<ref name="Wood-Derived Materials for Green El">{{cite journal|doi=10.1021/acs.chemrev.6b00225|pmid=27459699|title=Wood-Derived Materials for Green Electronics, Biological Devices, and Energy Applications|journal=Chemical Reviews|volume=116|issue=16|pages=9305–9374|year=2016|last1=Zhu|first1=Hongli|last2=Luo|first2=Wei|last3=Ciesielski|first3=Peter N.|last4=Fang|first4=Zhiqiang|last5=Zhu|first5=J. Y.|last6=Henriksson|first6=Gunnar|last7=Himmel|first7=Michael E.|last8=Hu|first8=Liangbing}}</ref><ref>{{cite journal|doi=10.1002/anie.201001273|pmid=21598362|title=Nanocelluloses: A New Family of Nature-Based Materials|journal=Angewandte Chemie International Edition|volume=50|issue=24|pages=5438–5466|year=2011|last1=Klemm|first1 =Dieter|last2=Kramer|first2=Friederike|last3=Moritz|first3=Sebastian|last4=Lindström|first4=Tom|last5=Ankerfors|first5=Mikael|last6=Gray|first6=Derek|last7=Dorris|first7=Annie}}</ref><ref>{{cite journal|doi=10.1039/C3CS60204D|pmid=24316693|title=Key advances in the chemical modification of nanocelluloses|journal=Chemical Society Reviews|volume=43|issue=5|pages=1519–1542|year=2014|last1=Habibi|first1=Youssef}}</ref>


== Terminology ==
Nanocellulose can also be obtained from native fibers by an acid hydrolysis, giving rise to highly crystalline and rigid nanoparticles which are shorter (100s to 1000 nanometers) than the '''cellulose nanofibrils''' (CNF) obtained through homogenization, microfluiodization or grinding routes. The resulting material is known as '''cellulose nanocrystal''' (CNC).<ref>{{cite journal|vauthors=Peng BL, Dhar N, Liu HL, Tam KC|year=2011|title=Chemistry and applications of nanocrystalline cellulose and its derivatives: A nanotechnology perspective|journal=The Canadian Journal of Chemical Engineering|volume=89|issue=5|pages=1191–1206|url=http://www.arboranano.ca/pdfs/Chemistry%20and%20applications%20of%20nanocrystalline%20cellulose%20and%20its%20derivatives%20A%20nanotechnology%20perspective-2011.pdf|doi=10.1002/cjce.20554|access-date=2012-08-28|archive-url=https://web.archive.org/web/20161024021059/http://www.arboranano.ca/pdfs/Chemistry%20and%20applications%20of%20nanocrystalline%20cellulose%20and%20its%20derivatives%20A%20nanotechnology%20perspective-2011.pdf|archive-date=2016-10-24|url-status=dead}}</ref>


=== Microfibrilated cellulose ===
Nano[[chitin]] is similar in its nanostructure to nanocellulose.


Micro cellulose (MFC) is a type of nanocellulose that is more heterogeneous than cellulose nanofibers or nanocrystals as it contains a mixture of nano- and micron-scale particles. The term is sometimes misused to refer to cellulose nanofibers instead.<ref>{{Cite journal | vauthors = Osong SH, Norgren S, Engstrand P |date=February 2016 |title=Processing of wood-based microfibrillated cellulose and nanofibrillated cellulose, and applications relating to papermaking: a review |url=http://link.springer.com/10.1007/s10570-015-0798-5 |journal=Cellulose |language=en |volume=23 |issue=1 |pages=93–123 |doi=10.1007/s10570-015-0798-5 |issn=0969-0239}}</ref><ref name=":0" />
==History and terminology==
The terminology [[microfibrillated]]/nanocellulose or (MFC) was first used by Turbak, Snyder and Sandberg in the late 1970s at the ITT [[Rayonier]] labs in [[Whippany, New Jersey]], to describe a product prepared as a gel type material by passing wood pulp through a Gaulin type milk homogenizer at high temperatures and high pressures followed by ejection impact against a hard surface.<ref>{{cite book | url=https://link.springer.com/book/10.1007/978-3-642-17370-7 | doi=10.1007/978-3-642-17370-7 | title=Cellulose Fibers: Bio- and Nano-Polymer Composites | year=2011 | isbn=978-3-642-17369-1 | editor-last1=Kalia | editor-last2=Kaith | editor-last3=Kaur | editor-first1=Susheel | editor-first2=B. S | editor-first3=Inderjeet }}</ref>


=== Cellulose nanofibers ===
The terminology first appeared publicly in the early 1980s when a number of patents and publications were issued to ITT Rayonier on a new nanocellulose composition of matter.<ref name="Turbak1983"/> In later work, F. W. Herrick at ITT Rayonier Eastern Research Division (ERD) Lab in Whippany also published work on making a dry powder form of the gel.<ref name="Herrick1983"/> Rayonier has produced purified pulps.<ref name="Turbak, A, F., Snyder, F.W. and Sandberg, K.R."/><ref>{{cite journal | url=https://www.osti.gov/biblio/5039044-microfibrillated-cellulose-morphology-accessibility | osti=5039044 | title=Microfibrillated cellulose: Morphology and accessibility | journal=J. Appl. Polym. Sci.: Appl. Polym. Symp.; (United States) | date=January 1983 | volume=37 | last1=Herrick | first1=F. W. | last2=Casebier | first2=R. L. | last3=Hamilton | first3=J. K. | last4=Sandberg | first4=K. R. }}</ref><ref>{{cite web | url=http://www.naylornetwork.com/PPI-OTW/articles/?aid=150993&issueID=22333 | title=Birth of Nanocellulose }}</ref> Rayonier gave free license to whoever wanted to pursue this new use for cellulose. Rayonier, as a company, never pursued scale-up. Rather, Turbak et al. pursued 1) finding new uses for the MFC/nanocellulose. These included using MFC as a thickener and binder in foods, cosmetics, paper formation, textiles, nonwovens, etc. and 2) evaluate swelling and other techniques for lowering the energy requirements for MFC/Nanocellulose production.<ref name = "Turbak, A.F.">Turbak, A.F., Snyder, F.W. and Sandberg, K.R. (1984) "Microfibrillated Cellulose—A New Composition of Commercial Significance," 1984 Nonwovens Symposium, Myrtle Beach, SC, Apr. 16–19. TAPPI Press, Atlanta, GA. pp 115–124.</ref> After ITT closed the Rayonier Whippany Labs in 1983–84, Herric worked on making a dry powder form of MFC at the Rayonier labs in [[Shelton, Washington]].<ref name="Herrick1983"/>


Cellulose nanofibers (CNF), also called '''nanofibrillated cellulose''' (NFC), are nanosized cellulose fibrils with a high aspect ratio (length to width ratio). Typical fibril widths are 5–20 [[nanometers]] with a wide range of lengths, typically several [[micrometers]].
In the mid-1990s, the group of Taniguchi and co-workers and later Yano and co-workers pursued the effort in Japan.<ref name="Berglund2005"/>

The fibrils can be isolated from natural cellulose, generally wood [[Pulp (paper)|pulp]], through high-pressure, high temperature and high velocity impact [[Homogenization (chemistry)|homogenization]], grinding or microfluidization (see manufacture below).<ref>{{cite journal | vauthors = Zhu H, Luo W, Ciesielski PN, Fang Z, Zhu JY, Henriksson G, Himmel ME, Hu L | title = Wood-Derived Materials for Green Electronics, Biological Devices, and Energy Applications | journal = Chemical Reviews | volume = 116 | issue = 16 | pages = 9305–9374 | date = August 2016 | pmid = 27459699 | doi = 10.1021/acs.chemrev.6b00225}}</ref><ref>{{cite journal | vauthors = Klemm D, Kramer F, Moritz S, Lindström T, Ankerfors M, Gray D, Dorris A | title = Nanocelluloses: a new family of nature-based materials | journal = Angewandte Chemie | volume = 50 | issue = 24 | pages = 5438–5466 | date = June 2011 | pmid = 21598362 | doi = 10.1002/anie.201001273}}</ref><ref>{{cite journal | vauthors = Habibi Y | title = Key advances in the chemical modification of nanocelluloses | journal = Chemical Society Reviews | volume = 43 | issue = 5 | pages = 1519–1542 | date = March 2014 | pmid = 24316693 | doi = 10.1039/C3CS60204D}}</ref>
[[File:Cotton CNCs.jpg|thumb|TEM image of CNCs made from cotton cellulose]]

=== Cellulose nanocrystals ===
'''Cellulose nanocrystals''' (CNCs), or '''nanocrystalline cellulose''' (NCC), are highly [[crystal]]line, rod-like nanoparticles.<ref>{{cite journal | vauthors = Habibi Y, Lucia LA, Rojas OJ | title = Cellulose nanocrystals: chemistry, self-assembly, and applications | journal = Chemical Reviews | volume = 110 | issue = 6 | pages = 3479–3500 | date = June 2010 | pmid = 20201500 | doi = 10.1021/cr900339w}}</ref><ref>{{cite journal | vauthors = George J, Sabapathi SN | title = Cellulose nanocrystals: synthesis, functional properties, and applications | language = English | journal = Nanotechnology, Science and Applications | volume = 8 | pages = 45–54 | date = 2015-11-04 | pmid = 26604715 | pmc = 4639556 | doi = 10.2147/NSA.S64386 | doi-access = free}}</ref> They are usually covered by negatively charged groups that render them [[colloid]]ally stable in water. They are typically shorter than CNFs, with a typical length of 100 to 1000 nanometers.<ref>{{cite journal |vauthors=Peng BL, Dhar N, Liu HL, Tam KC |year=2011 |title=Chemistry and applications of nanocrystalline cellulose and its derivatives: A nanotechnology perspective |url=http://www.arboranano.ca/pdfs/Chemistry%20and%20applications%20of%20nanocrystalline%20cellulose%20and%20its%20derivatives%20A%20nanotechnology%20perspective-2011.pdf |url-status=dead |journal=The Canadian Journal of Chemical Engineering |volume=89 |issue=5 |pages=1191–1206 |doi=10.1002/cjce.20554 |archive-url=https://web.archive.org/web/20161024021059/http://www.arboranano.ca/pdfs/Chemistry%20and%20applications%20of%20nanocrystalline%20cellulose%20and%20its%20derivatives%20A%20nanotechnology%20perspective-2011.pdf |archive-date=2016-10-24 |access-date=2012-08-28}}</ref>

=== Bacterial nanocellulose ===
Some cellulose producing bacteria have also been used to produce nanocellulosic materials that are then referred to as '''bacterial nanocellulose'''.<ref name=":4" /> The most common examples being ''Medusomyces gisevii'' (the bacteria involved in the making of [[Kombucha]]) and ''[[Komagataeibacter xylinus]]'' (involve in the fabrication of [[Nata de coco]]), see [[bacterial cellulose]] for more details. This naming distinction might arise from the very peculiar morphology of these materials compared to the more traditional ones made of wood or cotton cellulose. In practice, bacterial nanocellulosic materials are often larger than their wood or cotton counterparts.

==History ==

The discovery of nanocellulosic materials can be traced back to late 1940s studies on the [[hydrolysis]] of cellulose fibers.<ref name=":0" /> Eventually it was noticed that cellulose hydrolysis seemed to occur preferentially at some disordered intercrystalline portions of the fibers.<ref>{{Cite journal | vauthors = Nickerson RF, Habrle JA |date=November 1947 |title=Cellulose Intercrystalline Structure |url=https://pubs.acs.org/doi/abs/10.1021/ie50455a024 |journal=Industrial & Engineering Chemistry |language=en |volume=39 |issue=11 |pages=1507–1512 |doi=10.1021/ie50455a024 |issn=0019-7866}}</ref> This led to the obtention of [[colloid]]ally stable and highly crystalline nanorods particles.<ref>{{Cite journal | vauthors = Rånby BG |date=1949 |title=Aqueous Colloidal Solutions of Cellulose Micelles |url=http://actachemscand.org/pdf/acta_vol_03_p0649-0650.pdf |journal=Acta Chemica Scandinavica |volume=3 |pages=649–650|doi=10.3891/acta.chem.scand.03-0649}}</ref><ref>{{Cite journal | vauthors = Morehead FF |date=August 1950 |title=Ultrasonic Disintegration of Cellulose Fibers Before and After Acid Hydrolysis |url=http://journals.sagepub.com/doi/10.1177/004051755002000803 |journal=Textile Research Journal |language=en |volume=20 |issue=8 |pages=549–553 |doi=10.1177/004051755002000803 |issn=0040-5175}}</ref><ref>{{cite journal | vauthors = Mukherjee SM, Woods HJ | title = X-ray and electron microscope studies of the degradation of cellulose by sulphuric acid | journal = Biochimica et Biophysica Acta | volume = 10 | issue = 4 | pages = 499–511 | date = April 1953 | pmid = 13059015 | doi = 10.1016/0006-3002(53)90295-9}}</ref> These particles were first referred to as micelles, before being given multiple names including '''cellulose nanocrystals''' (CNCs), '''nanocrystalline cellulose''' (NCC), or '''cellulose (nano)whiskers''', though this last term is less used today.<ref name=":0" /> Later studies by [[Orlando Aloysius Battista|O. A. Battista]] showed that in milder hydrolysis conditions, the crystalline nanorods stay aggregated as micron size objects.<ref>{{cite patent | country = US | number = 2,978,446 | inventor = | invent1 = Battista | invent2 = Hill | invent3 = Smith | title = Level-off D.P cellulose products | pubdate = 1961-04-04 | assign1 = American Viscose Corporation | url = https://patentimages.storage.googleapis.com/31/17/12/49f0cccadd417a/US2978446.pdf}}</ref><ref>{{cite patent | country = US | number = 3,141,875 | inventor = | invent1 = Battista | invent2 = Hill | invent3 = Smith | title = Crystallite aggregates disintegrated in acid medium | pubdate = 1964-07-21 | assign1 = FMC Corporation | url = https://patentimages.storage.googleapis.com/31/17/12/49f0cccadd417a/US2978446.pdf}}</ref> This material was later referred to as '''[[microcrystalline cellulose]]''' (MCC) and commercialised under the name Avicel by [[FMC Corporation]].<ref>{{cite web | url=https://www.fmc.com/en/company/our-history | title=Our History &#124; FMC Corp }}</ref>

[[File:Nanocellulose.JPG|thumb|Nanocellulose gel (probably MFC of NFC)]]

Microfibrillated cellulose (MFC) was discovered later, in the 1980s, by Turbak, Snyder and Sandberg at the ITT [[Rayonier]] labs in [[Shelton, Washington|Shelton]], Washington.<ref>{{Cite journal |vauthors=Turbak AF, Snyder FW, Sandberg KR |date=1983 |title=Microfibrillated Cellulose, a New Cellulose Product: Properties, Uses, and Commercial Potential |url=http://www.nogimasaya.com/uploads/Turback-1983.pdf |journal=Journal of Applied Polymer Science: Applied Polymer Symposium |volume=37 |pages=815–827}}</ref><ref>{{cite web |title=Birth of Nanocellulose |url=http://www.naylornetwork.com/PPI-OTW/articles/?aid=150993&issueID=22333}}</ref><ref name=":3" /> This terminology was used to describe a gel-like material prepared by passing wood pulp through a Gaulin type milk homogenizer at high temperatures and high pressures followed by ejection impact against a hard surface. In later work, F. W. Herrick at ITT Rayonier Eastern Research Division (ERD) Lab in Whippany also published work on making a dry powder form of the gel.<ref>{{cite journal | url=https://www.osti.gov/biblio/5039044-microfibrillated-cellulose-morphology-accessibility | osti=5039044 | title=Microfibrillated cellulose: Morphology and accessibility | journal=J. Appl. Polym. Sci.: Appl. Polym. Symp.; (United States) | date=January 1983 | volume=37 | vauthors = Herrick FW, Casebier RL, Hamilton JK, Sandberg KR}}</ref><ref name=":3" /> Rayonier, as a company, never pursued scale-up and gave free license to whoever wanted to pursue this new use for cellulose.{{citation needed|date=March 2017}} Rather, Turbak et al. pursued 1) finding new uses for the MFC, including using as a thickener and binder in foods, cosmetics, paper formation, textiles, nonwovens, etc. and 2) evaluate swelling and other techniques for lowering the energy requirements for MFC production.<ref>Turbak, A.F., Snyder, F.W. and Sandberg, K.R. (1984) "Microfibrillated Cellulose—A New Composition of Commercial Significance," 1984 Nonwovens Symposium, Myrtle Beach, SC, Apr. 16–19. TAPPI Press, Atlanta, GA. pp 115–124.</ref> The first MFC pilot production plant of MFC was established in 2010 by Innventia AB (Sweden).<ref>{{cite thesis |vauthors=Ankerfors M |title=Microfibrillated cellulose: Energy-efficient preparation techniques and key properties |degree=Licentiate |publisher=Royal Institute of Technology |location=Sweden |year=2012 |isbn=978-91-7501-464-7 |url=https://www.diva-portal.org/smash/get/diva2:557668/FULLTEXT01.pdf}}</ref>


==Manufacture==
==Manufacture==


=== Cellulose sources ===
Nanocellulose, which is also called cellulose nanofibers (CNF), microfibrillated cellulose (MFC) or cellulose nanocrystal (CNC), can be prepared from any cellulose source material including agricultural waste including rice husks, cotton, coconut husk and algae; but [[woodpulp]] is normally used<ref>{{Cite journal |last=El Achaby |first=Mounir |last2=Kassab |first2=Zineb |last3=Aboulkas |first3=Adil |last4=Gaillard |first4=Cédric |last5=Barakat |first5=Abdellatif |date=2018-01-01 |title=Reuse of red algae waste for the production of cellulose nanocrystals and its application in polymer nanocomposites |url=https://www.sciencedirect.com/science/article/pii/S014181301732490X |journal=International Journal of Biological Macromolecules |volume=106 |pages=681–691 |doi=10.1016/j.ijbiomac.2017.08.067 |issn=0141-8130}}</ref><ref>{{Cite journal |last=Abbasi |first=Alireza |last2=Makhtoumi |first2=Yashar |last3=Wu |first3=Yudi |last4=Chen |first4=Gang |date=2024-06-01 |title=Characterization of cellulose nanocrystal extracted from household waste and its application for seed germination |url=https://www.sciencedirect.com/science/article/pii/S2666893923001299 |journal=Carbohydrate Polymer Technologies and Applications |volume=7 |pages=100409 |doi=10.1016/j.carpta.2023.100409 |issn=2666-8939}}</ref>.
Nanocellulose materials can be prepared from any natural cellulose source including [[wood]], [[cotton]], agricultural<ref>{{cite journal | vauthors = Almashhadani AQ, Leh CP, Chan SY, Lee CY, Goh CF | title = Nanocrystalline cellulose isolation via acid hydrolysis from non-woody biomass: Importance of hydrolysis parameters | journal = Carbohydrate Polymers | volume = 286 | pages = 119285 | date = June 2022 | pmid = 35337507 | doi = 10.1016/j.carbpol.2022.119285}}</ref> or household wastes,<ref>{{Cite journal | vauthors = Abbasi A, Makhtoumi Y, Wu Y, Chen G |date=2024-06-01 |title=Characterization of cellulose nanocrystal extracted from household waste and its application for seed germination |url= |journal=Carbohydrate Polymer Technologies and Applications |volume=7 |pages=100409 |doi=10.1016/j.carpta.2023.100409 |issn=2666-8939 |doi-access=free}}</ref> [[algae]],<ref>{{cite journal | vauthors = El Achaby M, Kassab Z, Aboulkas A, Gaillard C, Barakat A | title = Reuse of red algae waste for the production of cellulose nanocrystals and its application in polymer nanocomposites | journal = International Journal of Biological Macromolecules | volume = 106 | pages = 681–691 | date = January 2018 | pmid = 28823511 | doi = 10.1016/j.ijbiomac.2017.08.067 | url = https://hal.archives-ouvertes.fr/hal-01602653/file/El%20Achaby-BM-2017-manuscript-IATE_1.pdf}}</ref> [[bacteria]] or [[tunicate]]. [[Wood]], in the form of [[woodpulp|wood pulp]] is currently the most commonly used starting material for the industrial production of nanocellulosic materials.

=== Nanocellulose fibrils ===
Nanocellulose fibrils (MFC and CNFs) may be isolated from the cellulose fibers using mechanical methods that expose the fibers to high shear forces, delaminating them into nano-fibers. For this purpose, high-pressure homogenizers, grinders or microfluidizers can be used.{{citation needed|date=March 2017}} This process consumes very large amounts of energy and values over 30 MWh/[[tonne]] are not uncommon.{{citation needed|date=March 2017}}


To address this problem, sometimes enzymatic/mechanical pre-treatments and introduction of charged groups for example through carboxymethylation or [[TEMPO|TEMPO-mediated oxidation]] are used.<ref>{{cite web|url=http://mwp.org/2015-akira-isogai-tsuguyuki-saito-japan-and-yoshiharu-nishiyama-france/|title=Marcus Wallenberg Prize: 2015 – Akira Isogai, Tsuguyuki Saito, Japan, and Yoshiharu Nishiyama, France|website=mwp.org/|date=16 March 2015 |access-date=23 January 2018}}</ref> These pre-treatments can decrease energy consumption below 1 MWh/tonne.{{citation needed|date=March 2017}} "Nitro-oxidation" has been developed to prepare carboxycellulose nanofibers directly from raw plant biomass. Owing to fewer processing steps to extract nanocellulose, the nitro-oxidation method has been found to be a cost-effective, less-chemically oriented and efficient method to extract carboxycellulose nanofibers.<ref>{{cite journal | vauthors = Sharma PR, Joshi R, Sharma SK, Hsiao BS | title = A Simple Approach to Prepare Carboxycellulose Nanofibers from Untreated Biomass | journal = Biomacromolecules | volume = 18 | issue = 8 | pages = 2333–2342 | date = August 2017 | pmid = 28644013 | doi = 10.1021/acs.biomac.7b00544}}</ref><ref>{{cite journal| vauthors = Sharma PR, Zheng B, Sunil KS, Zhan C, Wang R, Bhatia SR, Benjamin SH| year=2018 | title=High Aspect Ratio Carboxycellulose Nanofibers Prepared by Nitro-Oxidation Method and Their Nanopaper Properties|journal= ACS Applied Nano Materials|volume=1|pages=3969–3980|doi=10.1021/acsanm.8b00744|issue=8|s2cid=139513681}}</ref> Functionalized nanofibers obtained using nitro-oxidation have been found to be an excellent substrate to remove heavy metal ion impurities such as [[lead]],<ref>{{cite journal| vauthors = Sharma PR, Chattopadhyay A, Sunil KS, Lihong GS, Benjamin SH |s2cid=103880950| year=2018 | title=Lead removal from water using carboxycellulose nanofibers prepared by nitro-oxidation method|journal=Cellulose|volume=25|pages=1961–1973|doi= 10.1007/s10570-018-1659-9|issue=3}}</ref> [[cadmium]],<ref>{{cite journal| vauthors = Sharma PR, Chattopadhyay A, Sharma SK, Geng L, Amiralian N, Martin D, Hsiao BS | year=2018 | title=Nanocellulose from Spinifex as an Effective Adsorbent to Remove Cadmium(II) from Water|journal= ACS Sustainable Chemistry & Engineering|volume=6|pages=3279–3290|doi=10.1021/acssuschemeng.7b03473 |issue=3}}</ref> and [[uranium]].<ref>{{cite journal | vauthors = Sharma PR, Chattopadhyay A, Sharma SK, Hsiao BS | year=2017 | title=Efficient Removal of UO22+ from Water Using Carboxycellulose Nanofibers Prepared by the Nitro-Oxidation Method|journal=Industrial & Engineering Chemistry Research|volume=56|pages=13885–13893|doi=10.1021/acs.iecr.7b03659 |issue=46}}</ref>
The nanocellulose fibrils may be isolated from the wood-based fibers using mechanical methods which expose the pulp to high shear forces, ripping the larger wood-fibres apart into nanofibers. For this purpose, high-pressure homogenizers, grinders or microfluidizers can be used.{{citation needed|date=March 2017}} The homogenizers are used to delaminate the cell walls of the fibers and liberate the nanosized fibrils. This process consumes very large amounts of energy and values over 30 MWh/[[tonne]] are not uncommon.{{citation needed|date=March 2017}}


A chemo-mechanical process for production of nanocellulose from cotton linters has been demonstrated with a capacity of 10&nbsp;kg per day.<ref>{{cite web |title=Nanocellulose - NaNo Research GROUP @ ICAR-CIRCOT, Mumbai |url=http://www.nanocellulose.in}}</ref>
To address this problem, sometimes enzymatic/mechanical pre-treatments<ref name="Paakko2007"/> and introduction of charged groups for example through carboxymethylation<ref name="Wagberg2008"/> or [[TEMPO|TEMPO-mediated oxidation]] are used.<ref>{{cite web|url=http://mwp.org/2015-akira-isogai-tsuguyuki-saito-japan-and-yoshiharu-nishiyama-france/|title=Marcus Wallenberg Prize: 2015 – Akira Isogai, Tsuguyuki Saito, Japan, and Yoshiharu Nishiyama, France|website=mwp.org/|access-date=23 January 2018}}</ref> These pre-treatments can decrease energy consumption below 1 MWh/tonne.<ref name="Lindstrom2009"/> "Nitro-oxidation" has been developed to prepare carboxycellulose nanofibers directly from raw plant biomass. Owing to fewer processing steps to extract nanocellulose, the nitro-oxidation method has been found to be a cost-effective, less-chemically oriented and efficient method to extract carboxycellulose nanofibers.<ref name="Sharma2017b">{{Cite journal |doi = 10.1021/acs.biomac.7b00544|pmid = 28644013|title = A Simple Approach to Prepare Carboxycellulose Nanofibers from Untreated Biomass|journal = Biomacromolecules|volume = 18|issue = 8|pages = 2333–2342|year = 2017|last1 = Sharma|first1 = Priyanka R.|last2 = Joshi|first2 = Ritika|last3 = Sharma|first3 = Sunil K.|last4 = Hsiao|first4 = Benjamin S.}}</ref><ref name="Sharma2018c">{{cite journal|last=Sharma|first=P.R.|author2=Zheng,B.|author3=Sunil K.,S.|author4=Zhan C.|author5=Wang R.|author6=Bhatia S.,R.|author7=Benjamin S.,H.| year=2018 | title=High Aspect Ratio Carboxycellulose Nanofibers Prepared by Nitro-Oxidation Method and Their Nanopaper Properties|journal= ACS Applied Nano Materials|volume=1|pages=3969–3980|doi=10.1021/acsanm.8b00744|issue=8|s2cid=139513681 }}</ref> Functionalized nanofibers obtained using nitro-oxidation have been found to be an excellent substrate to remove heavy metal ion impurities such as [[lead]],<ref name="Sharma2018a">{{cite journal|last=Sharma|first=P.R.|author2=Chattopadhyay,A.|author3=Sunil K., S.|author4=Lihong G.,S.|author5=Benjamin S.,H.|s2cid=103880950| year=2018 | title=Lead removal from water using carboxycellulose nanofibers prepared by nitro-oxidation method|journal=Cellulose|volume=25|pages=1961–1973|doi= 10.1007/s10570-018-1659-9|issue=3}}</ref> [[cadmium]],<ref name="Sharma2018b">{{cite journal|last=Sharma|first=P.R.|author2=Chattopadhyay, A.|author3=Sunil K., S.|author4=Lihong G., S.|author5=Nasim A.|author6=Darren M.|author7=Benjamin S., H.| year=2018 | title=Nanocellulose from Spinifex as an Effective Adsorbent to Remove Cadmium(II) from Water|journal= ACS Sustainable Chemistry & Engineering|volume=6|pages=3279–3290|doi=10.1021/acssuschemeng.7b03473 |issue=3}}</ref> and [[uranium]].<ref name="Sharma2017a">{{cite journal|last=Sharma|first=P.R.|author2=Chattopadhyay, A.|author3=Sunil K., S.|author4=Benjamin S., H.| year=2017 | title=Efficient Removal of UO22+ from Water Using Carboxycellulose Nanofibers Prepared by the Nitro-Oxidation Method|journal=Industrial & Engineering Chemistry Research|volume=56|pages=13885–13893|doi=10.1021/acs.iecr.7b03659 |issue=46}}</ref>


=== '''Cellulose nanocrystals''' ===
CNCs are rodlike highly crystalline particles (relative crystallinity index above 75%) with a rectangular cross section. They are formed by the acid hydrolysis of native cellulose fibers commonly using sulfuric or [[hydrochloric acid]]. Amorphous sections of native cellulose are hydrolysed and after careful timing, crystalline sections can be retrieved from the acid solution by centrifugation and washing. Their dimensions depend on the native cellulose source material, and hydrolysis time and temperature.<ref>{{cite web | url=https://www.sciencedirect.com/topics/chemical-engineering/nanowhiskers | title=Nanowhiskers - an overview &#124; ScienceDirect Topics }}</ref>
Cellulose nanocrystals (CNC) are formed by the acid hydrolysis of native cellulose fibers, most commonly using [[Sulfuric acid|sulfuric]] or [[hydrochloric acid]]. Disordered sections of native cellulose are hydrolysed and after careful timing, the remaining crystalline sections can be retrieved from the acid solution by centrifugation and dialysis against water. Their final dimensions depend on the cellulose source, its history, the hydrolysis conditions and the purification procedures.<ref>{{Cite web|url=https://www.sciencedirect.com/topics/chemical-engineering/nanowhiskers|title=Nanowhiskers - an overview &#124; ScienceDirect Topics}}</ref> CNCs are commercialised by various companies that use different sources and processes, leading to a range of available products.<ref>{{Cite journal |last1=Reid |first1=Michael S. |last2=Villalobos |first2=Marco |last3=Cranston |first3=Emily D. |date=2017-02-21 |title=Benchmarking Cellulose Nanocrystals: From the Laboratory to Industrial Production |url=https://pubs.acs.org/doi/10.1021/acs.langmuir.6b03765 |journal=Langmuir |language=en |volume=33 |issue=7 |pages=1583–1598 |doi=10.1021/acs.langmuir.6b03765 |pmid=27959566 |issn=0743-7463|hdl=11375/21951 |hdl-access=free }}</ref><ref>{{Cite journal |last1=Delepierre |first1=Gwendoline |last2=Vanderfleet |first2=Oriana M. |last3=Niinivaara |first3=Elina |last4=Zakani |first4=Behzad |last5=Cranston |first5=Emily D. |date=2021-07-20 |title=Benchmarking Cellulose Nanocrystals Part II: New Industrially Produced Materials |url=https://pubs.acs.org/doi/10.1021/acs.langmuir.1c00550 |journal=Langmuir |language=en |volume=37 |issue=28 |pages=8393–8409 |doi=10.1021/acs.langmuir.1c00550 |pmid=34250804 |issn=0743-7463}}</ref>
Spherical shaped carboxycellulose nanoparticles prepared by [[nitric acid]]-[[phosphoric acid]] treatment are stable in dispersion in its non-ionic form.<ref name="Sharma2017">{{cite journal|last=Sharma|first=P.R.|author2=Verma, A.J.| year=2013 | title=Functional nanoparticles obtained from cellulose: engineering the shape and size of 6-carboxycellulose|journal=Chemical Communications|volume=49|pages=13885–13893|doi=10.1039/c3cc44551h|pmid=23959448|issue=78}}</ref> In April 2013 breakthroughs in nanocellulose production, by algae, were announced at an American Chemical Society conference, by speaker R. Malcolm Brown, Jr., Ph.D, who has pioneered research in the field for more than 40 years, spoke at the First International Symposium on Nanocellulose, part of the American Chemical Society meeting. Genes from the family of bacteria that produce vinegar, Kombucha tea and nata de coco have become stars in a project — which scientists said has reached an advanced stage - that would turn algae into solar-powered factories for producing the “wonder material” nanocellulose.<ref>{{cite web|url=http://www.newswise.com/articles/engineering-algae-to-make-the-wonder-material-nanocellulose-for-biofuels-and-more|title=Engineering Algae to Make the 'Wonder Material' Nanocellulose for Biofuels and More|website=newswise.com}}</ref>


=== Other cellulose based nanoparticles ===
A chemo-mechanical process for production of nanocellulose from cotton linters has been demonstrated with a capacity of 10&nbsp;kg per day.<ref>{{cite web|url=http://www.nanocellulose.in|title=Nanocellulose - NaNo Research GROUP @ ICAR-CIRCOT, Mumbai}}</ref>
Spherical shaped carboxycellulose nanoparticles prepared by [[nitric acid]]-[[phosphoric acid]] treatment are stable in dispersion in its non-ionic form.<ref>{{cite journal |vauthors=Sharma PR, Varma AJ |date=October 2013 |title=Functional nanoparticles obtained from cellulose: engineering the shape and size of 6-carboxycellulose |journal=Chemical Communications |volume=49 |issue=78 |pages=8818–8820 |doi=10.1039/c3cc44551h |pmid=23959448}}</ref>


==Structure and properties==
==Structure and properties==
[[File:AFM Innventia nanocellulose.JPG|right|thumb|AFM height image of carboxymethylated nanocellulose adsorbed on a silica surface. The scanned surface area is 1 µm<sup>2</sup>.]]
[[File:AFM Innventia nanocellulose.JPG|right|thumb|AFM height image of carboxymethylated nanocellulose adsorbed on a silica surface. The scanned surface area is 1 μm<sup>2</sup>.]]


===Dimensions and crystallinity===
===Dimensions and crystallinity===
The ultrastructure of nanocellulose derived from various sources has been extensively studied. Techniques such as [[transmission electron microscopy]] (TEM), [[scanning electron microscopy]] (SEM), [[atomic force microscopy]] (AFM), [[wide angle X-ray scattering]] (WAXS), small incidence angle X-ray diffraction and solid state <sup>13</sup>C cross-polarization [[magic angle spinning]] (CP/MAS), [[nuclear magnetic resonance]] (NMR) and [[spectroscopy]] have been used to characterize typically dried nanocellulose morphology.<ref name="Siro2010"/>
The ultrastructure of nanocellulose derived from various sources has been extensively studied. Techniques such as [[transmission electron microscopy]] (TEM), [[scanning electron microscopy]] (SEM), [[atomic force microscopy]] (AFM), [[wide angle X-ray scattering]] (WAXS), small incidence angle X-ray diffraction and solid state <sup>13</sup>C cross-polarization [[magic angle spinning]] (CP/MAS), [[nuclear magnetic resonance]] (NMR) and [[spectroscopy]] have been used to characterize typically dried nanocellulose morphology.{{citation needed|date=March 2017}}


A combination of microscopic techniques with image analysis can provide information on fibril widths, it is more difficult to determine fibril lengths, because of entanglements and difficulties in identifying both ends of individual nanofibrils.<ref name=Chinga-Carrasco2011a>{{cite journal|last=Chinga-Carrasco|first=G.|author2=Yu, Y. |author3=Diserud, O. |title=Quantitative Electron Microscopy of Cellulose Nanofibril Structures from Eucalyptus and Pinus radiata Kraft Pulp Fibers|journal=Microscopy and Microanalysis|date=21 July 2011|volume=17|issue=4|pages=563–571|bibcode = 2011MiMic..17..563C |doi = 10.1017/S1431927611000444 |pmid=21740618|s2cid=2010930}}</ref><ref name=Chinga-Carrasco2011c>{{cite book|vauthors = Chinga-Carrasco G, Miettinen A, Luengo Hendriks CL, Gamstedt EK, Kataja M|title=Structural Characterisation of Kraft Pulp Fibres and Their Nanofibrillated Materials for Biodegradable Composite Applications| year=2011| publisher=InTech| isbn=978-953-307-352-1}}</ref>{{page needed|date=March 2017}} Also, nanocellulose suspensions may not be homogeneous and can consist of various structural components, including cellulose nanofibrils and nanofibril bundles.<ref name=Chinga-Carrasco2011b>{{cite journal|last=Chinga-Carrasco|first=G.|title=Cellulose fibres, nanofibrils and microfibrils: The morphological sequence of MFC components from a plant physiology and fibre technology point of view|journal=Nanoscale Research Letters|date=13 June 2011|volume=6|page=417|bibcode = 2011NRL.....6..417C |doi = 10.1186/1556-276X-6-417|pmid=21711944|pmc=3211513|issue=1 |doi-access=free }}</ref>
A combination of microscopic techniques with image analysis can provide information on fibril widths, it is more difficult to determine fibril lengths, because of entanglements and difficulties in identifying both ends of individual nanofibrils.<ref>{{cite journal | vauthors = Chinga-Carrasco G, Yu Y, Diserud O | title = Quantitative electron microscopy of cellulose nanofibril structures from Eucalyptus and Pinus radiata kraft pulp fibers | journal = Microscopy and Microanalysis | volume = 17 | issue = 4 | pages = 563–571 | date = August 2011 | pmid = 21740618 | doi = 10.1017/S1431927611000444 | bibcode = 2011MiMic..17..563C | s2cid = 2010930}}</ref><ref>{{cite book|vauthors = Chinga-Carrasco G, Miettinen A, Luengo Hendriks CL, Gamstedt EK, Kataja M|title=Structural Characterisation of Kraft Pulp Fibres and Their Nanofibrillated Materials for Biodegradable Composite Applications| year=2011| publisher=InTech| isbn=978-953-307-352-1}}</ref>{{page needed|date=March 2017}} Also, nanocellulose suspensions may not be homogeneous and can consist of various structural components, including cellulose nanofibrils and nanofibril bundles.<ref>{{cite journal | vauthors = Chinga-Carrasco G | title = Cellulose fibres, nanofibrils and microfibrils: The morphological sequence of MFC components from a plant physiology and fibre technology point of view | journal = Nanoscale Research Letters | volume = 6 | issue = 1 | pages = 417 | date = June 2011 | pmid = 21711944 | pmc = 3211513 | doi = 10.1186/1556-276X-6-417 | bibcode = 2011NRL.....6..417C | doi-access = free}}</ref>


In a study of enzymatically pre-treated nanocellulose fibrils in a suspension the size and size-distribution were established using cryo-TEM. The fibrils were found to be rather mono-dispersed mostly with a diameter of ca. 5&nbsp;nm although occasionally thicker fibril bundles were present.<ref name="Paakko2007"/> By combining ultrasonication with an "oxidation pretreatment", cellulose microfibrils with a lateral dimension below 1&nbsp;nm has been observed by AFM. The lower end of the thickness dimension is around 0.4&nbsp;nm, which is related to the thickness of a cellulose monolayer sheet.<ref>{{cite journal|last=Li|first=Qingqing|author2=Scott Renneckar|title=Supramolecular Structure Characterization of Molecularly Thin Cellulose I Nanoparticles|journal=Biomacromolecules|date=6 January 2011| volume=12| issue=3| pages=650–659| doi=10.1021/bm101315y| pmid=21210665}}</ref>
In a study of enzymatically pre-treated nanocellulose fibrils in a suspension the size and size-distribution were established using cryo-TEM. The fibrils were found to be rather mono-dispersed mostly with a diameter of ca. 5&nbsp;nm although occasionally thicker fibril bundles were present.<ref name="Paakko2007" /> By combining ultrasonication with an "oxidation pretreatment", cellulose microfibrils with a lateral dimension below 1&nbsp;nm has been observed by AFM. The lower end of the thickness dimension is around 0.4&nbsp;nm, which is related to the thickness of a cellulose monolayer sheet.<ref>{{cite journal | vauthors = Li Q, Renneckar S | title = Supramolecular structure characterization of molecularly thin cellulose I nanoparticles | journal = Biomacromolecules | volume = 12 | issue = 3 | pages = 650–659 | date = March 2011 | pmid = 21210665 | doi = 10.1021/bm101315y}}</ref>


Aggregate widths can be determined by CP/MAS NMR developed by [[Innventia|Innventia AB]], Sweden, which also has been demonstrated to work for nanocellulose (enzymatic pre-treatment). An average width of 17&nbsp;nm has been measured with the NMR-method, which corresponds well with SEM and TEM. Using TEM, values of 15&nbsp;nm have been reported for nanocellulose from carboxymethylated pulp. However, thinner fibrils can also be detected. Wågberg et al. reported fibril widths of 5–15&nbsp;nm for a nanocellulose with a charge density of about 0.5 meq./g.<ref name="Wagberg2008"/> The group of Isogai reported fibril widths of 3–5&nbsp;nm for TEMPO-oxidized cellulose having a charge density of 1.5 meq./g.<ref name="Fukuzumi2009"/>
Aggregate widths can be determined by CP/MAS NMR developed by [[Innventia|Innventia AB]], Sweden, which also has been demonstrated to work for nanocellulose (enzymatic pre-treatment). An average width of 17&nbsp;nm has been measured with the NMR-method, which corresponds well with SEM and TEM. Using TEM, values of 15&nbsp;nm have been reported for nanocellulose from carboxymethylated pulp. However, thinner fibrils can also be detected. Wågberg et al. reported fibril widths of 5–15&nbsp;nm for a nanocellulose with a charge density of about 0.5 meq./g.<ref name="Wagberg2008" /> The group of Isogai reported fibril widths of 3–5&nbsp;nm for TEMPO-oxidized cellulose having a charge density of 1.5 meq./g.<ref name="Fukuzumi2009" />


Pulp chemistry has a significant influence on nanocellulose microstructure. Carboxymethylation increases the numbers of charged groups on the fibril surfaces, making the fibrils easier to liberate and results in smaller and more uniform fibril widths (5–15&nbsp;nm) compared to enzymatically pre-treated nanocellulose, where the fibril widths were 10–30&nbsp;nm.<ref name="Aulin2009"/> The degree of crystallinity and crystal structure of nanocellulose. Nanocellulose exhibits cellulose crystal I organization and the degree of crystallinity is unchanged by the preparation of the nanocellulose. Typical values for the degree of crystallinity were around 63%.<ref name="Aulin2009"/>
Pulp chemistry has a significant influence on nanocellulose microstructure. Carboxymethylation increases the numbers of charged groups on the fibril surfaces, making the fibrils easier to liberate and results in smaller and more uniform fibril widths (5–15&nbsp;nm) compared to enzymatically pre-treated nanocellulose, where the fibril widths were 10–30&nbsp;nm.<ref name="Aulin2009" /> The degree of crystallinity and crystal structure of nanocellulose. Nanocellulose exhibits cellulose crystal I organization and the degree of crystallinity is unchanged by the preparation of the nanocellulose. Typical values for the degree of crystallinity were around 63%.<ref name="Aulin2009" />


===Viscosity===
===Viscosity===
The [[rheology]] of nanocellulose dispersions has been investigated.<ref name="tatsumi2002"/><ref name="Paakko2007"/> and revealed that the storage and loss modulus were independent of the angular frequency at all nanocellulose concentrations between 0.125% to 5.9%. The storage modulus values are particularly high (104 Pa at 3% concentration)<ref name="Paakko2007"/> compared to results for CNCs (102 Pa at 3% concentration).<ref name="tatsumi2002"/> There is also a strong concentration dependence as the storage modulus increases 5 orders of magnitude if the concentration is increased from 0.125% to 5.9%. Nanocellulose gels are also highly shear thinning (the viscosity is lost upon introduction of the shear forces). The shear-thinning behaviour is particularly useful in a range of different coating applications.<ref name="Paakko2007"/>
The [[rheology]] of nanocellulose dispersions has been investigated.<ref name="tatsumi2002" /><ref name="Paakko2007" /> and revealed that the storage and loss modulus were independent of the angular frequency at all nanocellulose concentrations between 0.125% to 5.9%. The storage modulus values are particularly high (104 Pa at 3% concentration)<ref name="Paakko2007" /> compared to results for CNCs (102 Pa at 3% concentration).<ref name="tatsumi2002" /> There is also a strong concentration dependence as the storage modulus increases 5 orders of magnitude if the concentration is increased from 0.125% to 5.9%. Nanocellulose gels are also highly shear thinning (the viscosity is lost upon introduction of the shear forces). The shear-thinning behaviour is particularly useful in a range of different coating applications.<ref name="Paakko2007" />

It is pseudo-plastic and exhibits [[thixotropy]], the property of certain [[gel]]s or [[fluid]]s that are thick (viscous) under normal conditions, but become less viscous when shaken or agitated. When the shearing forces are removed the gel regains much of its original state.


===Mechanical properties===
===Mechanical properties===
Crystalline cellulose has a stiffness about 140–220&nbsp;GPa, comparable with that of [[Kevlar]] and better than that of glass fiber, both of which are used commercially to reinforce plastics. Films made from nanocellulose have high strength (over 200&nbsp;[[MPa]]), high stiffness (around 20&nbsp;[[GPa]])<ref name="Henriksson2008"/> but lack of high strain{{clarify|date=May 2013}} (12%). Its strength/weight ratio is 8 times that of stainless steel.<ref name=ns>{{cite web|url=https://www.newscientist.com/article/mg21528786.100-why-wood-pulp-is-worlds-new-wonder-material.html |title=Why wood pulp is world's new wonder material – tech – 23 August 2012 |publisher=New Scientist |access-date=2012-08-30}}</ref> Fibers made from nanocellulose have high strength (up to 1.57 GPa) and stiffness (up to 86 GPa).<ref name="Mittal2018"/>
Crystalline cellulose has a stiffness about 140–220&nbsp;GPa, comparable with that of [[Kevlar]] and better than that of glass fiber, both of which are used commercially to reinforce plastics. Films made from nanocellulose have high strength (over 200&nbsp;[[MPa]]), high stiffness (around 20&nbsp;[[GPa]])<ref name="Henriksson2008" /> but lack of high strain{{clarify|date=May 2013}} (12%). Its strength/weight ratio is 8 times that of stainless steel.<ref name="ns" /> Fibers made from nanocellulose have high strength (up to 1.57 GPa) and stiffness (up to 86 GPa).<ref name="Mittal_2018" />


===Barrier properties===
===Barrier properties===
In semi-crystalline polymers, the crystalline regions are considered to be gas impermeable. Due to relatively high crystallinity,<ref name="Aulin2009"/> in combination with the ability of the nanofibers to form a dense network held together by strong inter-fibrillar bonds (high cohesive energy density), it has been suggested that nanocellulose might act as a barrier material.<ref name="Fukuzumi2009"/><ref name="Aulin2010a"/><ref name="Syverud2009"/> Although the number of reported oxygen permeability values are limited, reports attribute high oxygen barrier properties to nanocellulose films. One study reported an oxygen permeability of 0.0006 (cm<sup>3</sup>&nbsp;µm)/(m<sup>2</sup>&nbsp;day&nbsp;kPa) for a ca. 5&nbsp;µm thin nanocellulose film at 23&nbsp;°C and 0% RH.<ref name="Aulin2010a"/> In a related study, a more than 700-fold decrease in oxygen permeability of a polylactide (PLA) film when a nanocellulose layer was added to the PLA surface was reported.<ref name="Fukuzumi2009"/>
In semi-crystalline polymers, the crystalline regions are considered to be gas impermeable. Due to relatively high crystallinity,<ref name="Aulin2009" /> in combination with the ability of the nanofibers to form a dense network held together by strong inter-fibrillar bonds (high cohesive energy density), it has been suggested that nanocellulose might act as a barrier material.<ref name="Fukuzumi2009" /><ref name="Aulin_2010a" /><ref name="Syverud2009" /> Although the number of reported oxygen permeability values are limited, reports attribute high oxygen barrier properties to nanocellulose films. One study reported an oxygen permeability of 0.0006 (cm<sup>3</sup>&nbsp;μm)/(m<sup>2</sup>&nbsp;day&nbsp;kPa) for a ca. 5&nbsp;μm thin nanocellulose film at 23&nbsp;°C and 0% RH.<ref name="Aulin_2010a" /> In a related study, a more than 700-fold decrease in oxygen permeability of a polylactide (PLA) film when a nanocellulose layer was added to the PLA surface was reported.<ref name="Fukuzumi2009" />


The influence of nanocellulose film density and porosity on film oxygen permeability has been explored.<ref name=Chinga-Carrasco2012>{{cite journal|last=Chinga-Carrasco|first=G.|author2=Syverud K.|title=On the structure and oxygen transmission rate of biodegradable cellulose nanobarriers|journal=Nanoscale Research Letters|date=19 March 2012|volume=7|page=192|bibcode = 2012NRL.....7..192C |doi = 10.1186/1556-276X-7-192|pmid=22429336|pmc=3324384|issue=1 |doi-access=free }}</ref> Some authors have reported significant porosity in nanocellulose films,<ref name="Henriksson2007"/><ref name="Henriksson2008"/><ref name="Svagan2007"/> which seems to be in contradiction with high oxygen barrier properties, whereas Aulin et al.<ref name="Aulin2010a"/> measured a nanocellulose film density close to density of crystalline cellulose (cellulose Iß crystal structure, 1.63&nbsp;g/cm<sup>3</sup>)<ref name="Diddens2008"/> indicating a very dense film with a porosity close to zero.
The influence of nanocellulose film density and porosity on film oxygen permeability has been explored.<ref>{{cite journal | vauthors = Chinga-Carrasco G, Syverud K | title = On the structure and oxygen transmission rate of biodegradable cellulose nanobarriers | journal = Nanoscale Research Letters | volume = 7 | issue = 1 | pages = 192 | date = March 2012 | pmid = 22429336 | pmc = 3324384 | doi = 10.1186/1556-276X-7-192 | bibcode = 2012NRL.....7..192C | doi-access = free}}</ref> Some authors have reported significant porosity in nanocellulose films,<ref name="Henriksson2007" /><ref name="Henriksson2008" /><ref name="Svagan2007" /> which seems to be in contradiction with high oxygen barrier properties, whereas Aulin et al.<ref name="Aulin_2010a" /> measured a nanocellulose film density close to density of crystalline cellulose (cellulose Iß crystal structure, 1.63&nbsp;g/cm<sup>3</sup>)<ref name="Diddens2008" /> indicating a very dense film with a porosity close to zero.


Changing the surface functionality of the cellulose nanoparticle can also affect the permeability of nanocellulose films. Films constituted of negatively charged CNCs could effectively reduce permeation of negatively charged ions, while leaving neutral ions virtually unaffected. Positively charged ions were found to accumulate in the membrane.<ref name="permselective2009"/>
Changing the surface functionality of the cellulose nanoparticle can also affect the permeability of nanocellulose films. Films constituted of negatively charged CNCs could effectively reduce permeation of negatively charged ions, while leaving neutral ions virtually unaffected. Positively charged ions were found to accumulate in the membrane.<ref name="permselective2009" />


[[Multi-Parametric Surface Plasmon Resonance|Multi-parametric surface plasmon resonance]] is one of the methods to study barrier properties of natural, modified or coated nanocellulose. The different antifouling, moisture, solvent, antimicrobial barrier formulation quality can be measured on the nanoscale. The adsorption kinetics as well as the degree of swelling can be measured in real-time and label-free.<ref>{{cite journal|last1=Mohan|first1=Tamilselvan|last2=Niegelhell|first2=Katrin|last3=Zarth|first3=Cíntia Salomão Pinto|last4=Kargl|first4=Rupert|last5=Köstler|first5=Stefan|last6=Ribitsch|first6=Volker|last7=Heinze|first7=Thomas|last8=Spirk|first8=Stefan|last9=Stana-Kleinschek|first9=Karin|title=Triggering Protein Adsorption on Tailored Cationic Cellulose Surfaces|journal=Biomacromolecules|date=10 November 2014|volume=15|issue=11|pages=3931–3941|doi=10.1021/bm500997s|pmid=25233035}}</ref><ref>{{cite journal|title=Effect of Molecular Architecture of PDMAEMA–POEGMA Random and Block Copolymers on Their Adsorption on Regenerated and Anionic Nanocelluloses and Evidence of Interfacial Water Expulsion |last1 = Vuoriluoto |first1 = Maija | last2 = Orelma | first2=Hannes | last3 = Johansson | first3 = Leena-Sisko | last4 = Zhu | first4 = Baolei | last5 = Poutanen | first5 = Mikko | last6 = Walther | first6 = Andreas | last7 = Laine | first7 = Janne | last8 = Rojas | first8 = Orlando J. | doi=10.1021/acs.jpcb.5b07628 |pmid = 26560798 | journal= The Journal of Physical Chemistry B | volume= 119|issue=49 |pages= 5275–15286|year = 2015 }}</ref>
[[Multi-Parametric Surface Plasmon Resonance|Multi-parametric surface plasmon resonance]] is one of the methods to study barrier properties of natural, modified or coated nanocellulose. The different antifouling, moisture, solvent, antimicrobial barrier formulation quality can be measured on the nanoscale. The adsorption kinetics as well as the degree of swelling can be measured in real-time and label-free.<ref>{{cite journal | vauthors = Mohan T, Niegelhell K, Zarth CS, Kargl R, Köstler S, Ribitsch V, Heinze T, Spirk S, Stana-Kleinschek K | title = Triggering protein adsorption on tailored cationic cellulose surfaces | journal = Biomacromolecules | volume = 15 | issue = 11 | pages = 3931–3941 | date = November 2014 | pmid = 25233035 | doi = 10.1021/bm500997s}}</ref><ref>{{cite journal | vauthors = Vuoriluoto M, Orelma H, Johansson LS, Zhu B, Poutanen M, Walther A, Laine J, Rojas OJ | title = Effect of Molecular Architecture of PDMAEMA-POEGMA Random and Block Copolymers on Their Adsorption on Regenerated and Anionic Nanocelluloses and Evidence of Interfacial Water Expulsion | journal = The Journal of Physical Chemistry B | volume = 119 | issue = 49 | pages = 15275–15286 | date = December 2015 | pmid = 26560798 | doi = 10.1021/acs.jpcb.5b07628}}</ref>


===Liquid crystals, colloidal glasses, and hydrogels===
===Liquid crystals, colloidal glasses, and hydrogels===
Owed to their anisotropic shape and surface charge, nanocelluloses (mostly rigid CNCs) have a high [[excluded volume]] and self-assemble into cholesteric [[liquid crystals]] beyond a critical volume fraction.<ref>{{cite journal |last1=Revol |first1=J.-F. |last2=Bradford |first2=H. |last3=Giasson |first3=J. |last4=Marchessault |first4=R.H. |last5=Gray |first5=D.G. |title=Helicoidal self-ordering of cellulose microfibrils in aqueous suspension |journal=International Journal of Biological Macromolecules |date=June 1992 |volume=14 |issue=3 |pages=170–172 |doi=10.1016/S0141-8130(05)80008-X |pmid=1390450 |url=https://www.sciencedirect.com/science/article/pii/S014181300580008X}}</ref> Nanocellulose liquid crystals are left-handed due to the right-handed twist on particle level.<ref>{{cite journal |last1=Nyström |first1=Gustav |last2=Arcari |first2=Mario |last3=Adamcik |first3=Jozef |last4=Usov |first4=Ivan |last5=Mezzenga |first5=Raffaele |title=Nanocellulose Fragmentation Mechanisms and Inversion of Chirality from the Single Particle to the Cholesteric Phase |journal=ACS Nano |date=26 June 2018 |volume=12 |issue=6 |pages=5141–5148 |doi=10.1021/acsnano.8b00512 |pmid=29758157 |url=https://pubs.acs.org/doi/abs/10.1021/acsnano.8b00512|arxiv=1705.06620 |s2cid=29165853 }}</ref> Nanocellulose phase behavior is susceptible to ionic [[charge screening]]. An increase in [[ionic strength]] induces the arrest of nanocellulose dispersions into attractive glasses.<ref>{{cite journal |last1=Nordenström |first1=Malin |last2=Fall |first2=Andreas |last3=Nyström |first3=Gustav |last4=Wågberg |first4=Lars |title=Formation of Colloidal Nanocellulose Glasses and Gels |journal=Langmuir |date=26 September 2017 |volume=33 |issue=38 |pages=9772–9780 |doi=10.1021/acs.langmuir.7b01832 |pmid=28853581 |url=https://pubs.acs.org/doi/10.1021/acs.langmuir.7b01832}}</ref> At further increasing ionic strength, nanocelluloses aggregate into [[hydrogels]].<ref>{{cite journal |last1=Bertsch |first1=Pascal |last2=Isabettini |first2=Stéphane |last3=Fischer |first3=Peter |title=Ion-Induced Hydrogel Formation and Nematic Ordering of Nanocrystalline Cellulose Suspensions |journal=Biomacromolecules |date=11 December 2017 |volume=18 |issue=12 |pages=4060–4066 |doi=10.1021/acs.biomac.7b01119 |pmid=29028331 |url=https://pubs.acs.org/doi/abs/10.1021/acs.biomac.7b01119}}</ref> The interactions within nanocelluloses are weak and reversible, wherefore nanocellulose suspensions and hydrogels are [[Self-healing material|self-healing]] and may be applied as injectable materials<ref>{{cite journal |last1=Bertsch |first1=Pascal |last2=Schneider |first2=Livia |last3=Bovone |first3=Giovanni |last4=Tibbitt |first4=Mark W. |last5=Fischer |first5=Peter |last6=Gstöhl |first6=Stefan |title=Injectable Biocompatible Hydrogels from Cellulose Nanocrystals for Locally Targeted Sustained Drug Release |journal=ACS Applied Materials & Interfaces |date=23 October 2019 |volume=11 |issue=42 |pages=38578–38585 |doi=10.1021/acsami.9b15896|pmid=31573787 |s2cid=203638916 }}</ref> or [[3D printing]] inks.<ref>{{cite journal |last1=Siqueira |first1=Gilberto |last2=Kokkinis |first2=Dimitri |last3=Libanori |first3=Rafael |last4=Hausmann |first4=Michael K. |last5=Gladman |first5=Amelia Sydney |last6=Neels |first6=Antonia |last7=Tingaut |first7=Philippe |last8=Zimmermann |first8=Tanja |last9=Lewis |first9=Jennifer A. |last10=Studart |first10=André R. |title=Cellulose Nanocrystal Inks for 3D Printing of Textured Cellular Architectures |journal=Advanced Functional Materials |date=March 2017 |volume=27 |issue=12 |pages=1604619 |doi=10.1002/adfm.201604619|s2cid=33952694 |url=https://www.dora.lib4ri.ch/empa/islandora/object/empa%3A13555 }}</ref>
Owed to their anisotropic shape and surface charge, nanocelluloses (mostly rigid CNCs) have a high [[excluded volume]] and self-assemble into cholesteric [[liquid crystals]] beyond a critical volume fraction.<ref>{{cite journal | vauthors = Revol JF, Bradford H, Giasson J, Marchessault RH, Gray DG | title = Helicoidal self-ordering of cellulose microfibrils in aqueous suspension | journal = International Journal of Biological Macromolecules | volume = 14 | issue = 3 | pages = 170–172 | date = June 1992 | pmid = 1390450 | doi = 10.1016/S0141-8130(05)80008-X}}</ref> Nanocellulose liquid crystals are left-handed due to the right-handed twist on particle level.<ref>{{cite journal | vauthors = Nyström G, Arcari M, Adamcik J, Usov I, Mezzenga R | title = Nanocellulose Fragmentation Mechanisms and Inversion of Chirality from the Single Particle to the Cholesteric Phase | journal = ACS Nano | volume = 12 | issue = 6 | pages = 5141–5148 | date = June 2018 | pmid = 29758157 | doi = 10.1021/acsnano.8b00512 | arxiv = 1705.06620 | s2cid = 29165853}}</ref> Nanocellulose phase behavior is susceptible to ionic [[charge screening]]. An increase in [[ionic strength]] induces the arrest of nanocellulose dispersions into attractive glasses.<ref>{{cite journal | vauthors = Nordenström M, Fall A, Nyström G, Wågberg L | title = Formation of Colloidal Nanocellulose Glasses and Gels | journal = Langmuir | volume = 33 | issue = 38 | pages = 9772–9780 | date = September 2017 | pmid = 28853581 | doi = 10.1021/acs.langmuir.7b01832}}</ref> At further increasing ionic strength, nanocelluloses aggregate into [[hydrogels]].<ref>{{cite journal | vauthors = Bertsch P, Isabettini S, Fischer P | title = Ion-Induced Hydrogel Formation and Nematic Ordering of Nanocrystalline Cellulose Suspensions | journal = Biomacromolecules | volume = 18 | issue = 12 | pages = 4060–4066 | date = December 2017 | pmid = 29028331 | doi = 10.1021/acs.biomac.7b01119}}</ref> The interactions within nanocelluloses are weak and reversible, wherefore nanocellulose suspensions and hydrogels are [[Self-healing material|self-healing]] and may be applied as injectable materials<ref>{{cite journal | vauthors = Bertsch P, Schneider L, Bovone G, Tibbitt MW, Fischer P, Gstöhl S | title = Injectable Biocompatible Hydrogels from Cellulose Nanocrystals for Locally Targeted Sustained Drug Release | journal = ACS Applied Materials & Interfaces | volume = 11 | issue = 42 | pages = 38578–38585 | date = October 2019 | pmid = 31573787 | doi = 10.1021/acsami.9b15896 | s2cid = 203638916}}</ref> or [[3D printing]] inks.<ref>{{cite journal | vauthors = Siqueira G, Kokkinis D, Libanori R, Hausmann MK, Gladman AS, Neels A, Tingaut P, Zimmermann T, Lewis JA, Studart AR |title=Cellulose Nanocrystal Inks for 3D Printing of Textured Cellular Architectures |journal=Advanced Functional Materials |date=March 2017 |volume=27 |issue=12 |pages=1604619 |doi=10.1002/adfm.201604619|s2cid=33952694 |url=https://www.dora.lib4ri.ch/empa/islandora/object/empa%3A13555}}</ref>


===Bulk foams and aerogels===
===Bulk foams and aerogels===
Nanocellulose can also be used to make [[aerogels]]/foams, either homogeneously or in composite formulations. Nanocellulose-based foams are being studied for packaging applications in order to replace [[polystyrene]]-based foams. Svagan et al. showed that nanocellulose has the ability to reinforce [[starch]] foams by using a freeze-drying technique.<ref name="Svagan2008"/> The advantage of using nanocellulose instead of [[wood pulp|wood-based pulp fibers]] is that the nanofibrils can reinforce the thin cells in the starch foam. Moreover, it is possible to prepare pure nanocellulose aerogels applying various freeze-drying and super critical {{chem|CO|2}} drying techniques. Aerogels and foams can be used as porous templates.<ref name="Paako2008"/><ref name="Heath2010"/> Tough ultra-high porosity foams prepared from cellulose I nanofibril suspensions were studied by Sehaqui et al. a wide range of mechanical properties including compression was obtained by controlling density and nanofibril interaction in the foams.<ref name="Sehaqui2010"/> CNCs could also be made to gel in water under low power sonication giving rise to aerogels with the highest reported surface area (>600m2/g) and lowest shrinkage during drying (6.5%) of cellulose aerogels.<ref name="Heath2010"/> In another study by Aulin et al.,<ref name="Aulin2010b"/> the formation of structured porous aerogels of nanocellulose by freeze-drying was demonstrated. The density and surface texture of the aerogels was tuned by selecting the concentration of the nanocellulose dispersions before freeze-drying. [[Chemical vapour deposition]] of a fluorinated [[silane]] was used to uniformly coat the aerogel to tune their wetting properties towards non-polar liquids/oils. The authors demonstrated that it is possible to switch the wettability behaviour of the cellulose surfaces between super-wetting and super-repellent, using different scales of roughness and porosity created by the freeze-drying technique and change of concentration of the nanocellulose dispersion. Structured porous cellulose foams can however also be obtained by utilizing the freeze-drying technique on cellulose generated by [[Gluconobacter]] strains of bacteria, which bio-synthesize open porous networks of cellulose fibers with relatively large amounts of nanofibrils dispersed inside. Olsson et al.<ref>{{cite journal|last1=Olsson|first1=R. T.|last2=Azizi Samir|first2=M. A. S.|last3=Salazar-Alvarez|first3=G.|last4=Belova|first4=L.|last5=Ström|first5=V.|last6=Berglund|first6=L. A.|last7=Ikkala|first7=O.|last8=Nogués|first8=J.|last9=Gedde|first9=U. W.|title=Making flexible magnetic aerogels and stiff magnetic nanopaper using cellulose nanofibrils as templates|journal=Nature Nanotechnology|volume=5|pages=584–8|year=2010|doi=10.1038/nnano.2010.155|bibcode = 2010NatNa...5..584O|issue=8|pmid=20676090}}</ref> demonstrated that these networks can be further impregnated with metalhydroxide/oxide precursors, which can readily be transformed into grafted magnetic nanoparticles along the cellulose nanofibers. The magnetic cellulose foam may allow for a number of novel applications of nanocellulose and the first remotely actuated magnetic super sponges absorbing 1&nbsp;gram of water within a 60&nbsp;mg cellulose aerogel foam were reported. Notably, these highly porous foams (>98% air) can be compressed into strong magnetic nanopapers, which may find use as functional membranes in various applications.
Nanocellulose can also be used to make [[aerogels]]/foams, either homogeneously or in composite formulations. Nanocellulose-based foams are being studied for packaging applications in order to replace [[polystyrene]]-based foams. Svagan et al. showed that nanocellulose has the ability to reinforce [[starch]] foams by using a freeze-drying technique.<ref name="Svagan2008" /> The advantage of using nanocellulose instead of [[wood pulp|wood-based pulp fibers]] is that the nanofibrils can reinforce the thin cells in the starch foam. Moreover, it is possible to prepare pure nanocellulose aerogels applying various freeze-drying and super critical {{chem|CO|2}} drying techniques. Aerogels and foams can be used as porous templates.<ref name="Paako2008" /><ref name="Heath2010" /> Tough ultra-high porosity foams prepared from cellulose I nanofibril suspensions were studied by Sehaqui et al. a wide range of mechanical properties including compression was obtained by controlling density and nanofibril interaction in the foams.<ref name="Sehaqui2010" /> CNCs could also be made to gel in water under low power sonication giving rise to aerogels with the highest reported surface area (>600m2/g) and lowest shrinkage during drying (6.5%) of cellulose aerogels.<ref name="Heath2010" /> In another study by Aulin et al.,<ref name="Aulin_2010b" /> the formation of structured porous aerogels of nanocellulose by freeze-drying was demonstrated. The density and surface texture of the aerogels was tuned by selecting the concentration of the nanocellulose dispersions before freeze-drying. [[Chemical vapour deposition]] of a fluorinated [[silane]] was used to uniformly coat the aerogel to tune their wetting properties towards non-polar liquids/oils. The authors demonstrated that it is possible to switch the wettability behaviour of the cellulose surfaces between super-wetting and super-repellent, using different scales of roughness and porosity created by the freeze-drying technique and change of concentration of the nanocellulose dispersion. Structured porous cellulose foams can however also be obtained by utilizing the freeze-drying technique on cellulose generated by [[Gluconobacter]] strains of bacteria, which bio-synthesize open porous networks of cellulose fibers with relatively large amounts of nanofibrils dispersed inside. Olsson et al.<ref>{{cite journal | vauthors = Olsson RT, Azizi Samir MA, Salazar-Alvarez G, Belova L, Ström V, Berglund LA, Ikkala O, Nogués J, Gedde UW | title = Making flexible magnetic aerogels and stiff magnetic nanopaper using cellulose nanofibrils as templates | journal = Nature Nanotechnology | volume = 5 | issue = 8 | pages = 584–588 | date = August 2010 | pmid = 20676090 | doi = 10.1038/nnano.2010.155 | bibcode = 2010NatNa...5..584O}}</ref> demonstrated that these networks can be further impregnated with metalhydroxide/oxide precursors, which can readily be transformed into grafted magnetic nanoparticles along the cellulose nanofibers. The magnetic cellulose foam may allow for a number of novel applications of nanocellulose and the first remotely actuated magnetic super sponges absorbing 1&nbsp;gram of water within a 60&nbsp;mg cellulose aerogel foam were reported. Notably, these highly porous foams (>98% air) can be compressed into strong magnetic nanopapers, which may find use as functional membranes in various applications.


===Pickering emulsions and foams===
===Pickering emulsions and foams===
Nanocelluloses can stabilize [[emulsions]] and [[foams]] by a [[Pickering emulsion|Pickering]] mechanism, i.e. they adsorb at the oil-water or air-water interface and prevent their energetic unfavorable contact. Nanocelluloses form oil-in-water emulsions with a droplet size in the range of 4-10 μm that are stable for months and can resist high temperatures and changes in pH.<ref name="Kalashnikova2011">{{cite journal |last1=Kalashnikova |first1=Irina |last2=Bizot |first2=Hervé |last3=Cathala |first3=Bernard |last4=Capron |first4=Isabelle |title=New Pickering Emulsions Stabilized by Bacterial Cellulose Nanocrystals |journal=Langmuir |date=21 June 2011 |volume=27 |issue=12 |pages=7471–7479 |doi=10.1021/la200971f |pmid=21604688 }}</ref><ref name="Kalashnikova2013">{{cite journal |last1=Kalashnikova |first1=Irina |last2=Bizot |first2=Herve |last3=Bertoncini |first3=Patricia |last4=Cathala |first4=Bernard |last5=Capron |first5=Isabelle |title=Cellulosic nanorods of various aspect ratios for oil in water Pickering emulsions |journal=Soft Matter |date=2013 |volume=9 |issue=3 |pages=952–959 |doi=10.1039/C2SM26472B |bibcode=2013SMat....9..952K }}</ref> Nanocelluloses decrease the oil-water [[interface tension]]<ref name="Bergfreund2019">{{cite journal |last1=Bergfreund |first1=Jotam |last2=Sun |first2=Qiyao |last3=Fischer |first3=Peter |last4=Bertsch |first4=Pascal |title=Adsorption of charged anisotropic nanoparticles at oil–water interfaces |journal=Nanoscale Advances |date=2019 |volume=1 |issue=11 |pages=4308–4312 |doi=10.1039/C9NA00506D |pmid=36134395 |pmc=9419606 |bibcode=2019NanoA...1.4308B |doi-access=free }}</ref> and their surface charge induces electrostatic repulsion within emulsion droplets. Upon salt-induced charge screening the droplets aggregate but do not undergo [[coalescence (chemistry)|coalescence]], indicating strong steric stabilization.<ref name="Bai2019">{{cite journal |last1=Bai |first1=Long |last2=Lv |first2=Shanshan |last3=Xiang |first3=Wenchao |last4=Huan |first4=Siqi |last5=McClements |first5=David Julian |last6=Rojas |first6=Orlando J. |title=Oil-in-water Pickering emulsions via microfluidization with cellulose nanocrystals: 1. Formation and stability |journal=Food Hydrocolloids |date=November 2019 |volume=96 |pages=699–708 |doi=10.1016/j.foodhyd.2019.04.038 |doi-access=free }}</ref> The emulsion droplets even remain stable in the human stomach and resist gastric [[lipolysis]], thereby delaying [[lipid]] absorption and satiation.<ref>{{cite journal |last1=Scheuble |first1=Nathalie |last2=Schaffner |first2=Joschka |last3=Schumacher |first3=Manuel |last4=Windhab |first4=Erich J. |last5=Liu |first5=Dian |last6=Parker |first6=Helen |last7=Steingoetter |first7=Andreas |last8=Fischer |first8=Peter |title=Tailoring Emulsions for Controlled Lipid Release: Establishing in vitro–in Vivo Correlation for Digestion of Lipids |journal=ACS Applied Materials & Interfaces |date=30 May 2018 |volume=10 |issue=21 |pages=17571–17581 |doi=10.1021/acsami.8b02637 |url=https://pubs.acs.org/doi/full/10.1021/acsami.8b02637}}</ref><ref>{{cite journal |last1=Bertsch |first1=Pascal |last2=Steingoetter |first2=Andreas |last3=Arnold |first3=Myrtha |last4=Scheuble |first4=Nathalie |last5=Bergfreund |first5=Jotam |last6=Fedele |first6=Shahana |last7=Liu |first7=Dian |last8=Parker |first8=Helen L. |last9=Langhans |first9=Wolfgang |last10=Rehfeld |first10=Jens F. |last11=Fischer |first11=Peter |title=Lipid emulsion interfacial design modulates human in vivo digestion and satiation hormone response |journal=Food & Function |date=2022 |volume=13 |issue=17 |pages=9010–9020 |doi=10.1039/D2FO01247B |doi-access=free }}</ref> In contrast to emulsions, native nanocelluloses are generally not suitable for the Pickering stabilization of foams, which is attributed to their primarily [[hydrophilic]] surface properties that results in an unfavorable [[contact angle]] below 90° (they are preferably wetted by the aqueous phase).<ref name="Bertsch2019">{{cite journal |last1=Bertsch |first1=Pascal |last2=Arcari |first2=Mario |last3=Geue |first3=Thomas |last4=Mezzenga |first4=Raffaele |last5=Nyström |first5=Gustav |last6=Fischer |first6=Peter |title=Designing Cellulose Nanofibrils for Stabilization of Fluid Interfaces |journal=Biomacromolecules |date=12 November 2019 |volume=20 |issue=12 |pages=4574–4580 |doi=10.1021/acs.biomac.9b01384 |pmid=31714073 |s2cid=207943524 }}</ref> Using [[hydrophobic]] surface modifications or polymer grafting, the surface hydrophobicity and contact angle of nanocelluloses can be increased, allowing also the Pickering stabilization of foams.<ref name="Jin2012">{{cite journal |last1=Jin |first1=Huajin |last2=Zhou |first2=Weizheng |last3=Cao |first3=Jian |last4=Stoyanov |first4=Simeon D. |last5=Blijdenstein |first5=Theodorus B. J. |last6=de Groot |first6=Peter W. N. |last7=Arnaudov |first7=Luben N. |last8=Pelan |first8=Edward G. |title=Super stable foams stabilized by colloidal ethyl cellulose particles |journal=Soft Matter |date=2012 |volume=8 |issue=7 |pages=2194–2205 |doi=10.1039/c1sm06518a |bibcode=2012SMat....8.2194J }}</ref> By further increasing the surface hydrophobicity, inverse water-in-oil emulsions can be obtained, which denotes a contact angle higher than 90°.<ref name="Lee2014">{{cite journal |last1=Lee |first1=Koon-Yang |last2=Blaker |first2=Jonny J. |last3=Murakami |first3=Ryo |last4=Heng |first4=Jerry Y. Y. |last5=Bismarck |first5=Alexander |title=Phase Behavior of Medium and High Internal Phase Water-in-Oil Emulsions Stabilized Solely by Hydrophobized Bacterial Cellulose Nanofibrils |journal=Langmuir |date=8 January 2014 |volume=30 |issue=2 |pages=452–460 |doi=10.1021/la4032514 |pmid=24400918 |doi-access=free }}</ref><ref>{{cite journal |last1=Saidane |first1=Dorra |last2=Perrin |first2=Emilie |last3=Cherhal |first3=Fanch |last4=Guellec |first4=Florian |last5=Capron |first5=Isabelle |title=Some modification of cellulose nanocrystals for functional Pickering emulsions |journal=Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences |date=28 July 2016 |volume=374 |issue=2072 |page=20150139 |doi=10.1098/rsta.2015.0139 |pmid=27298429 |pmc=4920285 |bibcode=2016RSPTA.37450139S }}</ref> It was further demonstrated that nanocelluloses can stabilize water-in-water emulsions in presence of two incompatible water-soluble polymers.<ref>{{cite journal |last1=Peddireddy |first1=Karthik R. |last2=Nicolai |first2=Taco |last3=Benyahia |first3=Lazhar |last4=Capron |first4=Isabelle |title=Stabilization of Water-in-Water Emulsions by Nanorods |journal=ACS Macro Letters |date=9 February 2016 |volume=5 |issue=3 |pages=283–286 |doi=10.1021/acsmacrolett.5b00953 |pmid=35614722 }}</ref>
Nanocelluloses can stabilize [[emulsions]] and [[foams]] by a [[Pickering emulsion|Pickering]] mechanism, i.e. they adsorb at the oil-water or air-water interface and prevent their energetic unfavorable contact. Nanocelluloses form oil-in-water emulsions with a droplet size in the range of 4-10 μm that are stable for months and can resist high temperatures and changes in pH.<ref>{{cite journal | vauthors = Kalashnikova I, Bizot H, Cathala B, Capron I | title = New Pickering emulsions stabilized by bacterial cellulose nanocrystals | journal = Langmuir | volume = 27 | issue = 12 | pages = 7471–7479 | date = June 2011 | pmid = 21604688 | doi = 10.1021/la200971f}}</ref><ref>{{cite journal | vauthors = Kalashnikova I, Bizot H, Bertoncini P, Cathala B, Capron I |title=Cellulosic nanorods of various aspect ratios for oil in water Pickering emulsions |journal=Soft Matter |date=2013 |volume=9 |issue=3 |pages=952–959 |doi=10.1039/C2SM26472B |bibcode=2013SMat....9..952K}}</ref> Nanocelluloses decrease the oil-water [[interface tension]]<ref>{{cite journal | vauthors = Bergfreund J, Sun Q, Fischer P, Bertsch P | title = Adsorption of charged anisotropic nanoparticles at oil-water interfaces | journal = Nanoscale Advances | volume = 1 | issue = 11 | pages = 4308–4312 | date = November 2019 | pmid = 36134395 | pmc = 9419606 | doi = 10.1039/C9NA00506D | doi-access = free | bibcode = 2019NanoA...1.4308B}}</ref> and their surface charge induces electrostatic repulsion within emulsion droplets. Upon salt-induced charge screening the droplets aggregate but do not undergo [[coalescence (chemistry)|coalescence]], indicating strong steric stabilization.<ref>{{cite journal | vauthors = Bai L, Lv S, Xiang W, Huan S, McClements DJ, Rojas OJ |title=Oil-in-water Pickering emulsions via microfluidization with cellulose nanocrystals: 1. Formation and stability |journal=Food Hydrocolloids |date=November 2019 |volume=96 |pages=699–708 |doi=10.1016/j.foodhyd.2019.04.038 |doi-access=free}}</ref> The emulsion droplets even remain stable in the human stomach and resist gastric [[lipolysis]], thereby delaying [[lipid]] absorption and satiation.<ref>{{cite journal | vauthors = Scheuble N, Schaffner J, Schumacher M, Windhab EJ, Liu D, Parker H, Steingoetter A, Fischer P | title = Tailoring Emulsions for Controlled Lipid Release: Establishing in vitro-in Vivo Correlation for Digestion of Lipids | journal = ACS Applied Materials & Interfaces | volume = 10 | issue = 21 | pages = 17571–17581 | date = May 2018 | pmid = 29708724 | doi = 10.1021/acsami.8b02637}}</ref><ref>{{cite journal | vauthors = Bertsch P, Steingoetter A, Arnold M, Scheuble N, Bergfreund J, Fedele S, Liu D, Parker HL, Langhans W, Rehfeld JF, Fischer P | title = Lipid emulsion interfacial design modulates human ''in vivo'' digestion and satiation hormone response | journal = Food & Function | volume = 13 | issue = 17 | pages = 9010–9020 | date = August 2022 | pmid = 35942900 | pmc = 9426722 | doi = 10.1039/D2FO01247B | hdl-access = free | doi-access = free | hdl = 20.500.11850/564599}}</ref> In contrast to emulsions, native nanocelluloses are generally not suitable for the Pickering stabilization of foams, which is attributed to their primarily [[hydrophilic]] surface properties that results in an unfavorable [[contact angle]] below 90° (they are preferably wetted by the aqueous phase).<ref>{{cite journal | vauthors = Bertsch P, Arcari M, Geue T, Mezzenga R, Nyström G, Fischer P | title = Designing Cellulose Nanofibrils for Stabilization of Fluid Interfaces | journal = Biomacromolecules | volume = 20 | issue = 12 | pages = 4574–4580 | date = December 2019 | pmid = 31714073 | doi = 10.1021/acs.biomac.9b01384 | s2cid = 207943524}}</ref> Using [[hydrophobic]] surface modifications or polymer grafting, the surface hydrophobicity and contact angle of nanocelluloses can be increased, allowing also the Pickering stabilization of foams.<ref>{{cite journal | vauthors = Jin H, Zhou W, Cao J, Stoyanov SD, Blijdenstein TB, De Groot PW, Arnaudov LN, Pelan EG |title=Super stable foams stabilized by colloidal ethyl cellulose particles |journal=Soft Matter |date=2012 |volume=8 |issue=7 |pages=2194–2205 |doi=10.1039/c1sm06518a |bibcode=2012SMat....8.2194J}}</ref> By further increasing the surface hydrophobicity, inverse water-in-oil emulsions can be obtained, which denotes a contact angle higher than 90°.<ref>{{cite journal | vauthors = Lee KY, Blaker JJ, Murakami R, Heng JY, Bismarck A | title = Phase behavior of medium and high internal phase water-in-oil emulsions stabilized solely by hydrophobized bacterial cellulose nanofibrils | journal = Langmuir | volume = 30 | issue = 2 | pages = 452–460 | date = January 2014 | pmid = 24400918 | doi = 10.1021/la4032514 | doi-access = free}}</ref><ref>{{cite journal | vauthors = Saidane D, Perrin E, Cherhal F, Guellec F, Capron I | title = Some modification of cellulose nanocrystals for functional Pickering emulsions | journal = Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences | volume = 374 | issue = 2072 | page = 20150139 | date = July 2016 | pmid = 27298429 | pmc = 4920285 | doi = 10.1098/rsta.2015.0139 | bibcode = 2016RSPTA.37450139S}}</ref> It was further demonstrated that nanocelluloses can stabilize water-in-water emulsions in presence of two incompatible water-soluble polymers.<ref>{{cite journal | vauthors = Peddireddy KR, Nicolai T, Benyahia L, Capron I | title = Stabilization of Water-in-Water Emulsions by Nanorods | journal = ACS Macro Letters | volume = 5 | issue = 3 | pages = 283–286 | date = March 2016 | pmid = 35614722 | doi = 10.1021/acsmacrolett.5b00953}}</ref>


===Cellulose nanofiber plate (CNFP)===
===Cellulose nanofiber plate===
A bottom up approach can be used to create a high-performance bulk material with low density, high strength and toughness, and great thermal dimensional stability. Cellulose nanofiber hydrogel is created by biosynthesis. The hydrogels can then be treated with a polymer solution or by surface modification and then are hot-pressed at 80&nbsp;°C. The result is bulk material with excellent machinability. “The ultrafine nanofiber network structure in CNFP results in more extensive hydrogen bonding, the high in-plane orientation, and “three way branching points” of the microfibril networks”.<ref name="Lightweight, Tough, and Sustainable">{{cite journal |last1=Guan |first1=Qing-Fang |title=Lightweight, Tough, and Sustainable Cellulose Nanofiber-Derived Bulk Structural Materials with Low Thermal Expansion Coefficient |url= |journal=Science Advances |year=2020 |volume=6 |issue=18 |pages=eaaz1114 |publisher=American Association for the Advancement of Science|doi=10.1126/sciadv.aaz1114 |pmid=32494670 |pmc=7195169 |bibcode=2020SciA....6.1114G }}</ref> This structure gives CNFP its high strength by distributing stress and adding barriers to crack formation and propagation. The weak link in this structure is bond between the pressed layers which can lead to delamination. To reduce delamination, the hydrogel can be treated with silicic acid, which creates strong covalent cross-links between layers during hot pressing.<ref name="Lightweight, Tough, and Sustainable"/>
A bottom up approach can be used to create a high-performance bulk material with low density, high strength and toughness, and great thermal dimensional stability: cellulose nanofiber plate (CNFP). Cellulose nanofiber hydrogel is created by biosynthesis. The hydrogels can then be treated with a polymer solution or by surface modification and then are hot-pressed at 80&nbsp;°C. The result is bulk material with excellent machinability. “The ultrafine nanofiber network structure in CNFP results in more extensive hydrogen bonding, the high in-plane orientation, and “three way branching points” of the microfibril networks”.<ref name="Lightweight, Tough, and Sustainable" /> This structure gives CNFP its high strength by distributing stress and adding barriers to crack formation and propagation. The weak link in this structure is bond between the pressed layers which can lead to delamination. To reduce delamination, the hydrogel can be treated with [[silicic acid]], which creates strong covalent cross-links between layers during hot pressing.<ref name="Lightweight, Tough, and Sustainable" />


===Surface modification===
===Surface modification===
The surface modification of nanocellulose is currently receiving a large amount of attention.<ref name="Eichhorn review 2010"/> Nanocellulose displays a high concentration of hydroxyl groups at the surface which can be reacted. However, hydrogen bonding strongly affects the reactivity of the surface hydroxyl groups. In addition, impurities at the surface of nanocellulose such as glucosidic and lignin fragments need to be removed before surface modification to obtain acceptable reproducibility between different batches.<ref name="Labet2011"/>
The surface modification of nanocellulose is currently receiving a large amount of attention.<ref name="Eichhorn review 2010" /> Nanocellulose displays a high concentration of hydroxyl groups at the surface which can be reacted. However, hydrogen bonding strongly affects the reactivity of the surface hydroxyl groups. In addition, impurities at the surface of nanocellulose such as glucosidic and lignin fragments need to be removed before surface modification to obtain acceptable reproducibility between different batches.<ref name="Labet2011" />


===Safety aspects===
===Safety aspects===
Processing of nanocellulose does not cause significant exposure to fine particles during friction grinding or spray drying. No evidence of inflammatory effects or cytotoxicity on mouse or human macrophages can be observed after exposure to nanocellulose. The results of toxicity studies suggest that nanocellulose is not cytotoxic and does not cause any effects on inflammatory system in macrophages. In addition, nanocellulose is not acutely toxic to [[Aliivibrio fischeri|''Vibrio fischeri'']] in environmentally relevant concentrations.<ref name="Vartiainen2011"/>
Processing of nanocellulose does not cause significant exposure to fine particles during friction grinding or spray drying. No evidence of inflammatory effects or cytotoxicity on mouse or human macrophages can be observed after exposure to nanocellulose. The results of toxicity studies suggest that nanocellulose is not cytotoxic and does not cause any effects on inflammatory system in macrophages. In addition, nanocellulose is not acutely toxic to [[Aliivibrio fischeri|''Vibrio fischeri'']] in environmentally relevant concentrations.<ref name="Vartiainen2011" />

Despite intensified research on oral food or pharmaceutical formulations containing nanocelluloses they are not [[generally recognized as safe]]. Nanocelluloses were demonstrated to exhibit limited [[toxicity]] and [[oxidative stress]] in ''in vitro'' intestinal [[epithelium]]<ref>{{cite journal | vauthors = Cao X, Zhang T, DeLoid GM, Gaffrey MJ, Weitz KK, Thrall BD, Qian WJ, Demokritou P |title=Cytotoxicity and cellular proteome impact of cellulose nanocrystals using simulated digestion and an in vitro small intestinal epithelium cellular model |journal=NanoImpact |date=October 2020 |volume=20 |pages=100269 |doi=10.1016/j.impact.2020.100269 |url=|doi-access=free |bibcode=2020NanoI..2000269C}}</ref><ref>{{cite journal | vauthors = Mortensen NP, Moreno Caffaro M, Davis K, Aravamudhan S, Sumner SJ, Fennell TR | title = Investigation of eight cellulose nanomaterials' impact on Differentiated Caco-2 monolayer integrity and cytotoxicity | journal = Food and Chemical Toxicology | volume = 166 | pages = 113204 | date = August 2022 | pmid = 35679974 | doi = 10.1016/j.fct.2022.113204 | doi-access = free}}</ref><ref>{{cite journal | vauthors = Lin YJ, Qin Z, Paton CM, Fox DM, Kong F | title = Influence of cellulose nanocrystals (CNC) on permeation through intestinal monolayer and mucus model in vitro | journal = Carbohydrate Polymers | volume = 263 | pages = 117984 | date = July 2021 | pmid = 33858577 | doi = 10.1016/j.carbpol.2021.117984 | doi-access = free}}</ref> or animal models.<ref>{{cite journal | vauthors = DeLoid GM, Cao X, Molina RM, Silva DI, Bhattacharya K, Ng KW, Loo SC, Brain JD, Demokritou P | title = Toxicological effects of ingested nanocellulose in in vitro intestinal epithelium and in vivo rat models | journal = Environmental Science: Nano | volume = 6 | issue = 7 | pages = 2105–2115 | date = July 2019 | pmid = 32133146 | pmc = 7055654 | doi = 10.1039/c9en00184k | hdl-access = free | hdl = 10356/150824}}</ref><ref>{{cite journal | vauthors = Ede JD, Ong KJ, Mulenos MR, Pradhan S, Gibb M, Sayes CM, Shatkin JA | title = Physical, chemical, and toxicological characterization of sulfated cellulose nanocrystals for food-related applications using ''in vivo'' and ''in vitro'' strategies | journal = Toxicology Research | volume = 9 | issue = 6 | pages = 808–822 | date = December 2020 | pmid = 33447365 | pmc = 7786165 | doi = 10.1093/TOXRES/TFAA082}}</ref><ref>{{cite journal | vauthors = Khare S, DeLoid GM, Molina RM, Gokulan K, Couvillion SP, Bloodsworth KJ, Eder EK, Wong AR, Hoyt DW, Bramer LM, Metz TO, Thrall BD, Brain JD, Demokritou P | title = Effects of ingested nanocellulose on intestinal microbiota and homeostasis in Wistar Han rats | journal = NanoImpact | volume = 18 | pages = 100216 | date = April 2020 | pmid = 32190784 | pmc = 7080203 | doi = 10.1016/j.impact.2020.100216 | bibcode = 2020NanoI..1800216K}}</ref>


==Potential applications==
==Potential applications==
[[File:Elissa Brunato Bio Iridescent Sequin IMG07.jpg|thumb|Cellulose nanocrystals [[Self-organization|self-organized]] into Bio Iridescent Sequin. ]]
[[File:Elissa Brunato Bio Iridescent Sequin IMG07.jpg|thumb|Cellulose nanocrystals [[Self-organization|self-organized]] into Bio Iridescent Sequin. ]]
The properties of nanocellulose (e.g. mechanical properties, film-forming properties, viscosity etc.) makes it an interesting material for many applications.<ref>{{cite journal |doi=10.1021/bm3019467 |pmid=23421631 |title=Potential of Nanocrystalline Cellulose–Fibrin Nanocomposites for Artificial Vascular Graft Applications |journal=Biomacromolecules |volume=14 |issue=4 |pages=1063–71 |year=2013 |last1=Brown |first1=Elvie E. |last2=Hu |first2=Dehong |last3=Abu Lail |first3=Nehal |last4=Zhang |first4=Xiao }}</ref>
The properties of nanocellulose (e.g. mechanical properties, film-forming properties, viscosity etc.) makes it an interesting material for many applications.<ref>{{cite journal | vauthors = Brown EE, Hu D, Abu Lail N, Zhang X | title = Potential of nanocrystalline cellulose-fibrin nanocomposites for artificial vascular graft applications | journal = Biomacromolecules | volume = 14 | issue = 4 | pages = 1063–1071 | date = April 2013 | pmid = 23421631 | doi = 10.1021/bm3019467}}</ref>


[[File:RGB cellulose pigments and glitter - Droguet Benjamin, University of Cambridge.jpg|thumb|Cellulose nanocrystals [[Self-organization|self-organized]] into RGB glittery pigment particles.]]
[[File:RGB cellulose pigments and glitter - Droguet Benjamin, University of Cambridge.jpg|thumb|Cellulose nanocrystals [[Self-organization|self-organized]] into RGB glittery pigment particles.]]


[[File:Nanocellulose recycling 2.jpg|thumb|upright=1.75|Nanocellulose recycling chart<ref>{{cite journal|doi=10.1080/14686996.2017.1364976|pmid=28970870|pmc=5613913|title=Development and applications of transparent conductive nanocellulose paper|journal=Science and Technology of Advanced Materials|volume=18|issue=1|pages=620–633|year=2017|last1=Li|first1=Shaohui|last2=Lee|first2=Pooi See|bibcode=2017STAdM..18..620L}}</ref>]]
[[File:Nanocellulose recycling 2.jpg|thumb|upright=1.75|Nanocellulose recycling chart<ref>{{cite journal | vauthors = Li S, Lee PS | title = Development and applications of transparent conductive nanocellulose paper | journal = Science and Technology of Advanced Materials | volume = 18 | issue = 1 | pages = 620–633 | year = 2017 | pmid = 28970870 | pmc = 5613913 | doi = 10.1080/14686996.2017.1364976 | bibcode = 2017STAdM..18..620L}}</ref>]]
[[File:GaAs electronics on nanocellulose.jpg|thumb|[[GaAs]] electronics on nanocellulose substrate<ref name="bio" />]]
[[File:GaAs electronics on nanocellulose.jpg|thumb|[[GaAs]] electronics on nanocellulose substrate<ref name=bio>{{cite journal|doi=10.1038/ncomms8170|pmid=26006731|pmc=4455139|title=High-performance green flexible electronics based on biodegradable cellulose nanofibril paper|journal=Nature Communications|volume=6|page=7170|year=2015|last1=Jung|first1=Yei Hwan|last2=Chang|first2=Tzu-Hsuan|last3=Zhang|first3=Huilong|last4=Yao|first4=Chunhua|last5=Zheng|first5=Qifeng|last6=Yang|first6=Vina W.|last7=Mi|first7=Hongyi|last8=Kim|first8=Munho|last9=Cho|first9=Sang June|last10=Park|first10=Dong-Wook|last11=Jiang|first11=Hao|last12=Lee|first12=Juhwan|last13=Qiu|first13=Yijie|last14=Zhou|first14=Weidong|last15=Cai|first15=Zhiyong|last16=Gong|first16=Shaoqin|last17=Ma|first17=Zhenqiang|bibcode=2015NatCo...6.7170J}}</ref>]]


===Paper and paperboard===
===Paper and paperboard===
[[File:Nanocellulose solar cell.jpg|thumb|Bendable solar cell on nanocellulose substrate]]
[[File:Nanocellulose solar cell.jpg|thumb|Bendable solar cell on nanocellulose substrate]]
In the area of paper and paperboard manufacture, nanocelluloses are expected to enhance the fiber-fiber bond strength and, hence, have a strong reinforcement effect on paper materials.<ref>{{cite journal | last1 = Taipale | first1 = T. | last2 = Österberg | first2 = M. | last3 = Nykänen | first3 = A. | last4 = Ruokolainen | first4 = J. | last5 = Laine | first5 = J. | s2cid = 137591806 | year = 2010 | title = Effect of microfibrillated cellulose and fines on the drainage of kraft pulp suspension and paper strength | journal = Cellulose | volume = 17 | issue = 5| pages = 1005–1020 | doi=10.1007/s10570-010-9431-9}}</ref><ref>{{cite journal | last1 = Eriksen | first1 = Ø. | last2 = Syverud | first2 = K. | last3 = Gregersen | first3 = Ø. W. | s2cid = 139009497 | year = 2008 | title = The use of microfibrillated cellulose produced from kraft pulp as strength enhancer in TMP paper | journal = Nordic Pulp & Paper Research Journal| volume = 23 | issue = 3| pages = 299–304 | doi=10.3183/npprj-2008-23-03-p299-304}}</ref><ref>{{cite journal | last1 = Ahola | first1 = S. | last2 = Österberg | first2 = M. | last3 = Laine | first3 = J. | s2cid = 136939100 | year = 2007 | title = Cellulose nanofibrils—adsorption with poly(amideamine) epichlorohydrin studied by QCM-D and application as a paper strength additive | journal = Cellulose | volume = 15 | issue = 2| pages = 303–314 | doi=10.1007/s10570-007-9167-3}}</ref> Nanocellulose may be useful as a barrier in grease-proof type of papers and as a wet-end additive to enhance retention, dry and wet strength in commodity type of paper and board products.<ref>{{cite journal | last1 = Syverud | first1 = K. | last2 = Stenius | first2 = P. | s2cid = 136647719 | year = 2008 | title = Strength and barrier properties of MFC films | journal = Cellulose | volume = 16 | pages = 75–85 | doi=10.1007/s10570-008-9244-2}}</ref><ref>{{cite journal | last1 = Aulin | first1 = C. | last2 = Gällstedt | first2 = M. | last3 = Lindström | first3 = T. | s2cid = 137623000 | year = 2010 | title = Oxygen and oil barrier properties of microfibrillated cellulose films and coatings | journal = Cellulose | volume = 17 | issue = 3| pages = 559–574 | doi=10.1007/s10570-009-9393-y}}</ref><ref>{{cite journal | last1 = Lavoine | first1 = N. | last2 = Desloges | first2 = I. | last3 = Dufresne | first3 = A. | last4 = Bras | first4 = J. | year = 2012 | title = Microfibrillated cellulose - its barrier properties and applications in cellulosic materials: a review | journal = Carbohydrate Polymers| volume = 90 | issue = 2| pages = 735–64 | doi=10.1016/j.carbpol.2012.05.026| pmid = 22839998 }}</ref><ref>{{cite journal | last1 = Missoum | first1 = K. | last2 = Martoïa | first2 = F. | last3 = Belgacem | first3 = M. N. | last4 = Bras | first4 = J. | year = 2013 | title = Effect of chemically modified nanofibrillated cellulose addition on the properties of fiber-based materials | journal = Industrial Crops and Products| volume = 48 | pages = 98–105 | doi=10.1016/j.indcrop.2013.04.013}}</ref> It has been shown that applying CNF as a coating material on the surface of paper and paperboard improves the barrier properties, especially air resistance<ref name="Kumar 3603–3613">{{Cite journal|last1=Kumar|first1=Vinay|last2=Elfving|first2=Axel|last3=Koivula|first3=Hanna|last4=Bousfield|first4=Douglas|last5=Toivakka|first5=Martti|date=2016-03-30|title=Roll-to-Roll Processed Cellulose Nanofiber Coatings|journal=Industrial & Engineering Chemistry Research|language=en|volume=55|issue=12|pages=3603–3613|doi=10.1021/acs.iecr.6b00417|issn=0888-5885}}</ref> and grease/oil resistance.<ref name="Kumar 3603–3613"/><ref name="Lavoine 2879–2893">{{Cite journal|last1=Lavoine|first1=Nathalie|last2=Desloges|first2=Isabelle|last3=Khelifi|first3=Bertine|last4=Bras|first4=Julien|s2cid=137327179|date=April 2014|title=Impact of different coating processes of microfibrillated cellulose on the mechanical and barrier properties of paper|journal=Journal of Materials Science|language=en|volume=49|issue=7|pages=2879–2893|doi=10.1007/s10853-013-7995-0|bibcode=2014JMatS..49.2879L|issn=0022-2461}}</ref><ref name="Aulin 559–574">{{Cite journal|last1=Aulin|first1=Christian|last2=Gällstedt|first2=Mikael|last3=Lindström|first3=Tom|s2cid=137623000|date=June 2010|title=Oxygen and oil barrier properties of microfibrillated cellulose films and coatings|journal=Cellulose|language=en|volume=17|issue=3|pages=559–574|doi=10.1007/s10570-009-9393-y|issn=0969-0239}}</ref> It also enhances the structure properties of paperboards (smoother surface).<ref>{{Cite journal|last=Mazhari Mousavi|first=Seyyed Mohammad|display-authors=etal|year=2016|title=Cellulose nanofibers with higher solid content as a coating material to improve structure and barrier properties of paperboard|journal=TAPPI Conference Proceedings|pages=1–7}}</ref> Very high viscosity of MFC/CNF suspensions at low solids content limits the type of coating techniques that can be utilized to apply these suspensions onto paper/paperboard. Some of the coating methods utilized for MFC surface application onto paper/paperboard have been rod coating,<ref name="Aulin 559–574"/> size press,<ref name="Lavoine 2879–2893"/> spray coating,<ref>{{Cite journal|last1=Beneventi|first1=Davide|last2=Chaussy|first2=Didier|last3=Curtil|first3=Denis|last4=Zolin|first4=Lorenzo|last5=Gerbaldi|first5=Claudio|last6=Penazzi|first6=Nerino|date=2014-07-09|title=Highly Porous Paper Loading with Microfibrillated Cellulose by Spray Coating on Wet Substrates|journal=Industrial & Engineering Chemistry Research|language=en|volume=53|issue=27|pages=10982–10989|doi=10.1021/ie500955x|issn=0888-5885|doi-access=free}}</ref> foam coating <ref>{{Cite journal|last=Kinnunen-Raudaskoski|first=K.|title=Thin coatings for paper by foam coating|journal=TAPPI Journal|year=2014|volume=13|issue=7|pages=9–19|doi=10.32964/TJ13.7.9|doi-access=free}}</ref> and slot-die coating.<ref name="Kumar 3603–3613"/> Wet-end surface application of mineral pigments and MFC mixture to improve barrier, mechanical and printing properties of paperboard are also being explored.<ref>{{cite web|url=https://fiberlean.com/microfibrillated-cellulose-in-barrier-coating-applications/|title=Microfibrillated Cellulose in Barrier Coating Applications|date=October 2019|access-date=27 January 2020}}</ref>
In the area of paper and paperboard manufacture, nanocelluloses are expected to enhance the fiber-fiber bond strength and, hence, have a strong reinforcement effect on paper materials.<ref>{{cite journal | vauthors = Taipale T, Österberg M, Nykänen A, Ruokolainen J, Laine J | s2cid = 137591806 | year = 2010 | title = Effect of microfibrillated cellulose and fines on the drainage of kraft pulp suspension and paper strength | journal = Cellulose | volume = 17 | issue = 5| pages = 1005–1020 | doi=10.1007/s10570-010-9431-9}}</ref><ref>{{cite journal | vauthors = Eriksen Ø, Syverud K, Gregersen ØW | s2cid = 139009497 | year = 2008 | title = The use of microfibrillated cellulose produced from kraft pulp as strength enhancer in TMP paper | journal = Nordic Pulp & Paper Research Journal| volume = 23 | issue = 3| pages = 299–304 | doi=10.3183/npprj-2008-23-03-p299-304}}</ref><ref>{{cite journal | vauthors = Ahola S, Österberg M, Laine J | s2cid = 136939100 | year = 2007 | title = Cellulose nanofibrils—adsorption with poly(amideamine) epichlorohydrin studied by QCM-D and application as a paper strength additive | journal = Cellulose | volume = 15 | issue = 2| pages = 303–314 | doi=10.1007/s10570-007-9167-3}}</ref> Nanocellulose may be useful as a barrier in grease-proof type of papers and as a wet-end additive to enhance retention, dry and wet strength in commodity type of paper and board products.<ref name="Syverud_2008" /><ref name="Aulin_2010" /><ref>{{cite journal | vauthors = Lavoine N, Desloges I, Dufresne A, Bras J | title = Microfibrillated cellulose - its barrier properties and applications in cellulosic materials: a review | journal = Carbohydrate Polymers | volume = 90 | issue = 2 | pages = 735–764 | date = October 2012 | pmid = 22839998 | doi = 10.1016/j.carbpol.2012.05.026}}</ref><ref>{{cite journal | vauthors = Missoum K, Martoïa F, Belgacem MN, Bras J | year = 2013 | title = Effect of chemically modified nanofibrillated cellulose addition on the properties of fiber-based materials | journal = Industrial Crops and Products| volume = 48 | pages = 98–105 | doi=10.1016/j.indcrop.2013.04.013}}</ref> It has been shown that applying CNF as a coating material on the surface of paper and paperboard improves the barrier properties, especially air resistance<ref name="Kumar 3603–3613" /> and grease/oil resistance.<ref name="Kumar 3603–3613" /><ref name="Lavoine 2879–2893" /><ref name="Syverud_2008" /> It also enhances the structure properties of paperboards (smoother surface).<ref>{{Cite journal| vauthors = Mousavi SM, Bousfield D |year=2016|title=Cellulose nanofibers with higher solid content as a coating material to improve structure and barrier properties of paperboard|journal=TAPPI Conference Proceedings|pages=1–7}}</ref> Very high viscosity of MFC/CNF suspensions at low solids content limits the type of coating techniques that can be utilized to apply these suspensions onto paper/paperboard. Some of the coating methods utilized for MFC surface application onto paper/paperboard have been rod coating,<ref name="Aulin_2010" /> size press,<ref name="Lavoine 2879–2893" /> spray coating,<ref>{{Cite journal| vauthors = Beneventi D, Chaussy D, Curtil D, Zolin L, Gerbaldi C, Penazzi N |date=2014-07-09|title=Highly Porous Paper Loading with Microfibrillated Cellulose by Spray Coating on Wet Substrates|journal=Industrial & Engineering Chemistry Research|language=en|volume=53|issue=27|pages=10982–10989|doi=10.1021/ie500955x|issn=0888-5885|doi-access=free}}</ref> foam coating <ref>{{Cite journal| vauthors = Kinnunen-Raudaskoski K|title=Thin coatings for paper by foam coating|journal=TAPPI Journal|year=2014|volume=13|issue=7|pages=9–19|doi=10.32964/TJ13.7.9|doi-access=free}}</ref> and slot-die coating.<ref name="Kumar 3603–3613" /> Wet-end surface application of mineral pigments and MFC mixture to improve barrier, mechanical and printing properties of paperboard are also being explored.<ref>{{cite web|url=https://fiberlean.com/microfibrillated-cellulose-in-barrier-coating-applications/|title=Microfibrillated Cellulose in Barrier Coating Applications|date=October 2019|access-date=27 January 2020}}</ref>


Nanocellulose can be used to prepare flexible and optically transparent paper. Such paper is an attractive substrate for electronic devices because it is recyclable, compatible with biological objects, and easily [[biodegradation|biodegrades]].<ref name=bio/>
Nanocellulose can be used to prepare flexible and optically transparent paper. Such paper is an attractive substrate for electronic devices because it is recyclable, compatible with biological objects, and easily [[biodegradation|biodegrades]].<ref name="bio" />


===Composite===
===Composite===
As described above the properties of the nanocellulose makes an interesting material for reinforcing plastics. Nanocellulose can be spun into filaments that are stronger and stiffer than spider silk.<ref>{{Cite journal|last1=Mittal|first1=Nitesh|last2=Ansari|first2=Farhan|last3=Gowda.V|first3=Krishne|last4=Brouzet|first4=Christophe|last5=Chen|first5=Pan|last6=Larsson|first6=Per Tomas|last7=Roth|first7=Stephan V.|last8=Lundell|first8=Fredrik|last9=Wågberg|first9=Lars|last10=Kotov|first10=Nicholas A.|last11=Söderberg|first11=L. Daniel|date=2018-07-24|title=Multiscale Control of Nanocellulose Assembly: Transferring Remarkable Nanoscale Fibril Mechanics to Macroscale Fibers|journal=ACS Nano|volume=12|issue=7|pages=6378–6388|doi=10.1021/acsnano.8b01084|pmid=29741364|issn=1936-0851|doi-access=free}}</ref><ref>{{Cite news|date=17 October 2018|title=Threads of nanocellulose stronger than spider silk|url=https://news.cision.com/rise/r/threads-of-nanocellulose-stronger-than-spider-silk,c2646561|access-date=29 June 2020}}</ref> Nanocellulose has been reported to improve the mechanical properties of thermosetting resins, [[starch]]-based matrixes, [[soy protein]], [[rubber latex]], [[Polylactic acid|poly(lactide)]]. Hybrid cellulose nanofibrils-clay minerals composites present interesting mechanical, gas barrier and fire retardancy properties.<ref>{{Cite journal|last1=Alves|first1=L.|last2=Ferraz|first2=E.|last3=Gamelas|first3=J. A. F.|date=2019-10-01|title=Composites of nanofibrillated cellulose with clay minerals: A review|journal=Advances in Colloid and Interface Science|volume=272|page=101994|doi=10.1016/j.cis.2019.101994|pmid=31394436|s2cid=199507603|issn=0001-8686}}</ref> The composite applications may be for use as coatings and films,<ref>{{Cite journal|last1=Gamelas|first1=José António Ferreira|last2=Ferraz|first2=Eduardo|date=2015-08-05|title=Composite Films Based on Nanocellulose and Nanoclay Minerals as High Strength Materials with Gas Barrier Capabilities: Key Points and Challenges|url=http://ojs.cnr.ncsu.edu/index.php/BioRes/article/view/BioRes_10_4_6310_Gamelas_Editorial_Composite_Films_Nanocellulose_Nanoclay|journal=BioResources|language=en|volume=10|issue=4|pages=6310–6313|doi=10.15376/biores.10.4.6310-6313|issn=1930-2126|doi-access=free}}</ref> paints, foams, packaging.
As described above the properties of the nanocellulose makes an interesting material for reinforcing plastics. Nanocellulose can be spun into filaments that are stronger and stiffer than spider silk.<ref name="Mittal_2018" /><ref>{{Cite news|date=17 October 2018|title=Threads of nanocellulose stronger than spider silk|url=https://news.cision.com/rise/r/threads-of-nanocellulose-stronger-than-spider-silk,c2646561|access-date=29 June 2020}}</ref> Nanocellulose has been reported to improve the mechanical properties of thermosetting resins, [[starch]]-based matrixes, [[soy protein]], [[rubber latex]], [[Polylactic acid|poly(lactide)]]. Hybrid cellulose nanofibrils-clay minerals composites present interesting mechanical, gas barrier and fire retardancy properties.<ref>{{cite journal | vauthors = Alves L, Ferraz E, Gamelas JA | title = Composites of nanofibrillated cellulose with clay minerals: A review | journal = Advances in Colloid and Interface Science | volume = 272 | pages = 101994 | date = October 2019 | pmid = 31394436 | doi = 10.1016/j.cis.2019.101994 | s2cid = 199507603}}</ref> The composite applications may be for use as coatings and films,<ref>{{Cite journal| vauthors = Alves L, Ferraz E, Gamelas JA |date=2015-08-05|title=Composite Films Based on Nanocellulose and Nanoclay Minerals as High Strength Materials with Gas Barrier Capabilities: Key Points and Challenges|url=http://ojs.cnr.ncsu.edu/index.php/BioRes/article/view/BioRes_10_4_6310_Gamelas_Editorial_Composite_Films_Nanocellulose_Nanoclay|journal=BioResources|language=en|volume=10|issue=4|pages=6310–6313|doi=10.15376/biores.10.4.6310-6313|issn=1930-2126|doi-access=free|hdl=10400.26/38419|hdl-access=free}}</ref> paints, foams, packaging.


===Food===
===Food===
Nanocellulose can be used as a low calorie replacement for carbohydrate additives used as thickeners, flavour carriers, and suspension stabilizers in a wide variety of food products.<ref>{{Cite journal |last1=Gómez H. |first1=C. |last2=Serpa |first2=A. |last3=Velásquez-Cock |first3=J. |last4=Gañán |first4=P. |last5=Castro |first5=C. |last6=Vélez |first6=L. |last7=Zuluaga |first7=R. |date=2016-06-01 |title=Vegetable nanocellulose in food science: A review |url=https://www.sciencedirect.com/science/article/pii/S0268005X16300236 |journal=Food Hydrocolloids |language=en |volume=57 |pages=178–186 |doi=10.1016/j.foodhyd.2016.01.023 |issn=0268-005X}}</ref> It is useful for producing fillings, crushes, chips, wafers, soups, gravies, puddings etc. The food applications arise from the rheological behaviour of the nanocellulose gel.
Nanocellulose can be used as a low calorie replacement for carbohydrate additives used as thickeners, flavour carriers, and suspension stabilizers in a wide variety of food products.<ref>{{Cite journal | vauthors = Gómez HC, Serpa A, Velásquez-Cock J, Gañán P, Castro C, Vélez L, Zuluaga R |date=2016-06-01 |title=Vegetable nanocellulose in food science: A review |url= |journal=Food Hydrocolloids |language=en |volume=57 |pages=178–186 |doi=10.1016/j.foodhyd.2016.01.023 |issn=0268-005X}}</ref> It is useful for producing fillings, crushes, chips, wafers, soups, gravies, puddings etc. The food applications arise from the rheological behaviour of the nanocellulose gel.


===Hygiene and absorbent products===
===Hygiene and absorbent products===
Applications in this field include: super water absorbent material (e.g. for incontinence pads material), nanocellulose used together with super absorbent polymers, nanocellulose in tissue, non-woven products or absorbent structures and as antimicrobial films. {{citation needed|date=March 2017}}
Applications in this field include: super water absorbent material (e.g. for incontinence pads material), nanocellulose used together with super absorbent polymers, nanocellulose in tissue, non-woven products or absorbent structures and as antimicrobial films.{{citation needed|date=March 2017}}


===Emulsion and dispersion===
===Emulsion and dispersion===
Nanocellulose has potential applications in the general area of emulsion and dispersion applications in other fields.<ref name=Xhanari2011>{{cite journal|last=Xhanari|first=K.|author2=Syverud, K. |author3=Stenius, P. |s2cid=98317845|title=Emulsions stabilized by microfibrillated cellulose: the effect of hydrophobization, concentration and o/w ratio|journal=Dispersion Science and Technology|year=2011|volume=32|issue=3|pages=447–452|doi=10.1080/01932691003658942}}</ref><ref>{{cite journal|last=Lif|first=A. |author2=Stenstad, P. |author3=Syverud, K. |author4=Nydén, M. |author5=Holmberg, K.|title=Fischer-Tropsch diesel emulsions stabilised by microfibrillated cellulose|journal=Colloid and Interface Science|volume=352|issue=2|pages=585–592|doi=10.1016/j.jcis.2010.08.052|pmid=20864117 |year=2010 |bibcode=2010JCIS..352..585L}}</ref>
Nanocellulose has potential applications in the general area of emulsion and dispersion applications in other fields.<ref>{{cite journal| vauthors = Xhanari K, Syverud K, Stenius P |s2cid=98317845|title=Emulsions stabilized by microfibrillated cellulose: the effect of hydrophobization, concentration and o/w ratio|journal=Dispersion Science and Technology|year=2011|volume=32|issue=3|pages=447–452|doi=10.1080/01932691003658942}}</ref><ref>{{cite journal | vauthors = Lif A, Stenstad P, Syverud K, Nydén M, Holmberg K | title = Fischer-Tropsch diesel emulsions stabilised by microfibrillated cellulose and nonionic surfactants | journal = Journal of Colloid and Interface Science | volume = 352 | issue = 2 | pages = 585–592 | date = December 2010 | pmid = 20864117 | doi = 10.1016/j.jcis.2010.08.052 | bibcode = 2010JCIS..352..585L}}</ref>


===Medical, cosmetic and pharmaceutical===
===Medical, cosmetic and pharmaceutical===
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* Powdered nanocellulose has also been suggested as an excipient in pharmaceutical compositions
* Powdered nanocellulose has also been suggested as an excipient in pharmaceutical compositions
* Nanocellulose in compositions of a photoreactive noxious substance purging agent
* Nanocellulose in compositions of a photoreactive noxious substance purging agent
* Elastic cryo-structured gels for potential biomedical and biotechnological application<ref name=Syverud2011>{{cite journal|last=Syverud|first=K.|author2=Kirsebom, H. |author3=Hajizadeh, S. |author4=Chinga-Carrasco, G. |title=Cross-linking cellulose nanofibrils for potential elastic cryo-structured gels|journal=Nanoscale Research Letters|date=12 December 2011|volume=6|page=626|bibcode = 2011NRL.....6..626S |doi = 10.1186/1556-276X-6-626 |pmid=22152032|pmc=3260332|issue=1 |doi-access=free }}</ref>
* Elastic cryo-structured gels for potential biomedical and biotechnological application<ref>{{cite journal | vauthors = Syverud K, Kirsebom H, Hajizadeh S, Chinga-Carrasco G | title = Cross-linking cellulose nanofibrils for potential elastic cryo-structured gels | journal = Nanoscale Research Letters | volume = 6 | issue = 1 | pages = 626 | date = December 2011 | pmid = 22152032 | pmc = 3260332 | doi = 10.1186/1556-276X-6-626 | bibcode = 2011NRL.....6..626S | doi-access = free}}</ref>
* [[3D cell culture in wood-based nanocellulose hydrogel|Matrix for 3D cell culture]]
* [[3D cell culture in wood-based nanocellulose hydrogel|Matrix for 3D cell culture]]


=== Bio-based electronics and energy storage ===
=== Bio-based electronics and energy storage ===
Nanocellulose can pave the way for a new type of "bio-based electronics" where interactive materials are mixed with nanocellulose to enable the creation of new interactive fibers, films, aerogels, hydrogels and papers.<ref>{{Cite book|last1=Granberg|first1=Hjalmar|title=Electroactive papers, films, filaments, aerogels and hydrogels to realize the future of bio-based electronics|last2=Håkansson|first2=Karl|last3=Fall|first3=Andreas|last4=Wågberg|first4=Pia|publisher=PaperCon 2019, Indianapolis, USA: proceedings, TAPPI Press|date=5–8 May 2019|location=artikel-id PF4.1}}</ref> E.g. nanocellulose mixed with conducting polymers such as [[PEDOT:PSS]] show synergetic effects resulting in [https://onlinelibrary.wiley.com/doi/full/10.1002/advs.201500305 extraordinary]<ref>{{Cite journal|last1=Malti|first1=Abdellah|last2=Edberg|first2=Jesper|last3=Granberg|first3=Hjalmar|last4=Khan|first4=Zia Ullah|last5=Andreasen|first5=Jens W.|last6=Liu|first6=Xianjie|last7=Zhao|first7=Dan|last8=Zhang|first8=Hao|last9=Yao|first9=Yulong|last10=Brill|first10=Joseph W.|last11=Engquist|first11=Isak|date=2015-12-02|title=An Organic Mixed Ion–Electron Conductor for Power Electronics|journal=Advanced Science|volume=3|issue=2|doi=10.1002/advs.201500305|issn=2198-3844|pmc=5063141|pmid=27774392}}</ref> mixed [[Electrical resistivity and conductivity|electronic]] and [[Conductivity (electrolytic)|ionic]] conductivity, which is important for [[energy storage]] applications. Filaments spun from a mix of nanocellulose and [[carbon nanotube]]s show good conductivity and mechanical properties.<ref>{{Cite journal|last1=Hamedi|first1=Mahiar M.|last2=Hajian|first2=Alireza|last3=Fall|first3=Andreas B.|last4=Håkansson|first4=Karl|last5=Salajkova|first5=Michaela|last6=Lundell|first6=Fredrik|last7=Wågberg|first7=Lars|last8=Berglund|first8=Lars A.|date=2014-03-25|title=Highly Conducting, Strong Nanocomposites Based on Nanocellulose-Assisted Aqueous Dispersions of Single-Wall Carbon Nanotubes|url=https://doi.org/10.1021/nn4060368|journal=ACS Nano|volume=8|issue=3|pages=2467–2476|doi=10.1021/nn4060368|pmid=24512093|issn=1936-0851}}</ref> Nanocellulose aerogels decorated with carbon nanotubes can be constructed into robust compressible 3D [[supercapacitor]] devices.<ref>{{Cite journal|last1=Erlandsson|first1=Johan|last2=López Durán|first2=Verónica|last3=Granberg|first3=Hjalmar|last4=Sandberg|first4=Mats|last5=Larsson|first5=Per A.|last6=Wågberg|first6=Lars|date=2016-12-01|title=Macro- and mesoporous nanocellulose beads for use in energy storage devices|url=http://www.sciencedirect.com/science/article/pii/S2352940716301433|journal=Applied Materials Today|language=en|volume=5|pages=246–254|doi=10.1016/j.apmt.2016.09.008|issn=2352-9407}}</ref><ref name="NyströmMarais2015" /> Structures from nanocellulose can be turned into [[Bio-based material|bio-based]] [[Triboelectric effect|triboelectric]] [[Electric generator|generators]]<ref>{{Cite journal|last1=Wu|first1=Changsheng|last2=Wang|first2=Aurelia C.|last3=Ding|first3=Wenbo|last4=Guo|first4=Hengyu|last5=Wang|first5=Zhong Lin|date=2019|title=Triboelectric Nanogenerator: A Foundation of the Energy for the New Era|journal=Advanced Energy Materials|language=en|volume=9|issue=1|pages=1802906|doi=10.1002/aenm.201802906|issn=1614-6840|doi-access=free}}</ref> and [[sensors]].
Nanocellulose can pave the way for a new type of "bio-based electronics" where interactive materials are mixed with nanocellulose to enable the creation of new interactive fibers, films, aerogels, hydrogels and papers.<ref>{{Cite book| vauthors = Granberg H, Håkansson K, Fall A, Wågberg P |title=Electroactive papers, films, filaments, aerogels and hydrogels to realize the future of bio-based electronics| location = Indianapolis, USA | publisher = TAPPI Press|date=5–8 May 2019| page = artikel-id PF4.1}}</ref> E.g. nanocellulose mixed with conducting polymers such as [[PEDOT:PSS]] show synergetic effects resulting in [https://onlinelibrary.wiley.com/doi/full/10.1002/advs.201500305 extraordinary]<ref>{{cite journal | vauthors = Malti A, Edberg J, Granberg H, Khan ZU, Andreasen JW, Liu X, Zhao D, Zhang H, Yao Y, Brill JW, Engquist I, Fahlman M, Wågberg L, Crispin X, Berggren M | title = An Organic Mixed Ion-Electron Conductor for Power Electronics | journal = Advanced Science | volume = 3 | issue = 2 | pages = 1500305 | date = February 2016 | pmid = 27774392 | pmc = 5063141 | doi = 10.1002/advs.201500305}}</ref> mixed [[Electrical resistivity and conductivity|electronic]] and [[Conductivity (electrolytic)|ionic]] conductivity, which is important for [[energy storage]] applications. Filaments spun from a mix of nanocellulose and [[carbon nanotube]]s show good conductivity and mechanical properties.<ref>{{cite journal | vauthors = Hamedi MM, Hajian A, Fall AB, Håkansson K, Salajkova M, Lundell F, Wågberg L, Berglund LA | title = Highly conducting, strong nanocomposites based on nanocellulose-assisted aqueous dispersions of single-wall carbon nanotubes | journal = ACS Nano | volume = 8 | issue = 3 | pages = 2467–2476 | date = March 2014 | pmid = 24512093 | doi = 10.1021/nn4060368}}</ref> Nanocellulose aerogels decorated with carbon nanotubes can be constructed into robust compressible 3D [[supercapacitor]] devices.<ref>{{Cite journal| vauthors = Erlandsson J, López Durán V, Granberg H, Sandberg M, Larsson PA, Wågberg L |date=2016-12-01|title=Macro- and mesoporous nanocellulose beads for use in energy storage devices|url=|journal=Applied Materials Today|language=en|volume=5|pages=246–254|doi=10.1016/j.apmt.2016.09.008|issn=2352-9407}}</ref><ref name="NyströmMarais2015" /> Structures from nanocellulose can be turned into [[Bio-based material|bio-based]] [[Triboelectric effect|triboelectric]] [[Electric generator|generators]]<ref>{{Cite journal| vauthors = Wu C, Wang AC, Ding W, Guo H, Wang ZL |date=2019|title=Triboelectric Nanogenerator: A Foundation of the Energy for the New Era|journal=Advanced Energy Materials|language=en|volume=9|issue=1|pages=1802906|doi=10.1002/aenm.201802906|issn=1614-6840|doi-access=free|bibcode=2019AdEnM...902906W}}</ref> and [[sensors]].

In April 2013 breakthroughs in nanocellulose production, by algae, were announced at an American Chemical Society conference, by speaker R. Malcolm Brown, Jr., Ph.D, who has pioneered research in the field for more than 40 years, spoke at the First International Symposium on Nanocellulose, part of the American Chemical Society meeting. Genes from the family of bacteria that produce vinegar, Kombucha tea and nata de coco have become stars in a project — which scientists said has reached an advanced stage - that would turn algae into solar-powered factories for producing the “wonder material” nanocellulose.<ref name=":4" />


=== Bio-based coloured materials ===
=== Bio-based coloured materials ===
Cellulose nanocrystals have shown the possibility to [[Self-organization|self organize]] into chiral nematic structures<ref>{{Cite journal|last1=Gray|first1=Derek G.|last2=Mu|first2=Xiaoyue|date=2015-11-18|title=Chiral Nematic Structure of Cellulose Nanocrystal Suspensions and Films; Polarized Light and Atomic Force Microscopy|journal= Materials|volume=8|issue=11|pages=7873–7888|doi=10.3390/ma8115427|issn=1996-1944|pmc=5458898|pmid=28793684|bibcode=2015Mate....8.7873G|doi-access=free}}</ref> with angle-dependent [[Iridescence|iridescent]] colours. It is thus possible to manufacture totally bio-based [https://www.wired.com/story/all-that-glitters-isnt-litter/ pigments and glitters], [https://www.nature.com/articles/s41563-021-01135-8 films] including [https://www.materialsource.co.uk/bio-iridescent-sequin-is-a-material-research-and-design-project-that-harnesses-the-potential-of-bio-technologies-to-create-colourful-shimmering-sequins-from-wood-that-are-compostable-and-made-with-a-waste-free-process/ sequins] having a metallic glare and a small footprint compared to fossil-based alternatives.
Cellulose nanocrystals have shown the possibility to [[Self-organization|self organize]] into chiral nematic structures<ref>{{cite journal | vauthors = Gray DG, Mu X | title = Chiral Nematic Structure of Cellulose Nanocrystal Suspensions and Films; Polarized Light and Atomic Force Microscopy | journal = Materials | volume = 8 | issue = 11 | pages = 7873–7888 | date = November 2015 | pmid = 28793684 | pmc = 5458898 | doi = 10.3390/ma8115427 | doi-access = free | bibcode = 2015Mate....8.7873G}}</ref> with angle-dependent [[Iridescence|iridescent]] colours. It is thus possible to manufacture totally bio-based [https://www.wired.com/story/all-that-glitters-isnt-litter/ pigments and glitters], [https://www.nature.com/articles/s41563-021-01135-8 films] including [https://www.materialsource.co.uk/bio-iridescent-sequin-is-a-material-research-and-design-project-that-harnesses-the-potential-of-bio-technologies-to-create-colourful-shimmering-sequins-from-wood-that-are-compostable-and-made-with-a-waste-free-process/ sequins] having a metallic glare and a small footprint compared to fossil-based alternatives.


===Other potential applications===
===Other potential applications===
* As a highly scattering material for ultra-white coatings<ref>{{cite journal |last1=Toivonen |first1=Matti S.|last2=Onelli |first2=Olimpia D. |last3=Jacucci |first3= Gianni |last4=Lovikka|first4=Ville |last5=Rojas |first5=Orlando J. |last6=Ikkala |first6=Olli|last7=Vignolini |first7=Silvia |date=13 March 2018 |title=Anomalous-Diffusion-Assisted Brightness in White Cellulose Nanofibril Membranes
* As a highly scattering material for ultra-white coatings<ref>{{cite journal | vauthors = Toivonen MS, Onelli OD, Jacucci G, Lovikka V, Rojas OJ, Ikkala O, Vignolini S | title = Anomalous-Diffusion-Assisted Brightness in White Cellulose Nanofibril Membranes | journal = Advanced Materials | volume = 30 | issue = 16 | pages = e1704050 | date = April 2018 | pmid = 29532967 | doi = 10.1002/adma.201704050 | doi-access = free | bibcode = 2018AdM....3004050T}}</ref>
|journal=Advanced Materials |volume= 30|issue= 16|page= 1704050|doi=10.1002/adma.201704050 |pmid=29532967|doi-access=free }}</ref>
* Activate the dissolution of cellulose in different solvents
* Activate the dissolution of cellulose in different solvents
* Regenerated cellulose products, such as fibers films, cellulose derivatives
* Regenerated cellulose products, such as fibers films, cellulose derivatives
Line 135: Line 160:
* Loud-speaker [[Acoustic membrane|membranes]]
* Loud-speaker [[Acoustic membrane|membranes]]
* High-flux [[Artificial membrane|membranes]]
* High-flux [[Artificial membrane|membranes]]
* Computer components<ref name=ns/><ref name="Dandekar2016">{{cite patent | country = WO | number = 2016174104 A1 | status = application | title = Modified bacterial nanocellulose and its uses in chip cards and medicine | pubdate = 2016-11-03 | fdate = 2016-04-27 | pridate = 2015-04-27 | invent1 = Thomas Dandekar | assign1 = Julius-Maximilians-Universität Würzburg}}</ref>
* Computer components<ref name="ns" /><ref>{{cite patent | country = WO | number = 2016174104 A1 | status = application | title = Modified bacterial nanocellulose and its uses in chip cards and medicine | pubdate = 2016-11-03 | fdate = 2016-04-27 | pridate = 2015-04-27 | invent1 = Dandekar T | assign1 = Julius-Maximilians-Universität Würzburg | url = https://patents.google.com/patent/WO2016174104A1}}</ref>
* Capacitors<ref name="NyströmMarais2015" />
* Capacitors<ref name="NyströmMarais2015">{{cite journal|last1=Nyström|first1=Gustav|last2=Marais|first2=Andrew|last3=Karabulut|first3=Erdem|last4=Wågberg|first4=Lars|last5=Cui|first5=Yi|last6=Hamedi|first6=Mahiar M.|title=Self-assembled three-dimensional and compressible interdigitated thin-film supercapacitors and batteries|journal=Nature Communications|volume=6|year=2015|page=7259|issn=2041-1723|doi=10.1038/ncomms8259|bibcode = 2015NatCo...6.7259N|pmid=26021485|pmc=4458871}}</ref>
* Lightweight body armour and ballistic glass<ref name=ns/>
* Lightweight body armour and ballistic glass<ref name="ns" />
* Corrosion inhibitors<ref>Garner, A. (2015-2016) {{US Patent|9222174}} "Corrosion inhibitor comprising cellulose nanocrystals and cellulose nanocrystals in combination with a corrosion inhibitor" and {{US Patent|9359678}} "Use of charged cellulose nanocrystals for corrosion inhibition and a corrosion inhibiting composition comprising the same".</ref>
* Corrosion inhibitors<ref>{{cite patent | inventor = Garner A | country = US | number = 9222174 | title = Corrosion inhibitor comprising cellulose nanocrystals and cellulose nanocrystals in combination with a corrosion inhibitor | url = https://patents.google.com/patent/US9222174B2 | gdate = 29 December 2015 | assign = Nanohibitor Technology Inc.}}</ref><ref>{{cite patent | inventor = Garner A | country = US | number = 9359678 | title = Use of charged cellulose nanocrystals for corrosion inhibition and a corrosion inhibiting composition comprising the same | assign = Nanohibitor Technology Inc. | gdate = 7 June 2016}}</ref>
* Radio lenses <ref>{{cite journal |last1=Kokkonen |first1=Mikko |last2=Nelo |first2=Mikko |last3=Liimatainen |first3=Henrikki |last4=Ukkola |first4=Jonne |last5=Tervo |first5=Nuutti |last6=Myllymäki |first6=Sami |last7=Juuti |first7=Jari |last8=Jantunen |first8=Heli |title=Wood-based composite materials for ultralight lens antennas in 6G systems |journal=Materials Advances |date=7 February 2022 |volume=3 |issue=3 |pages=1687–1694 |doi=10.1039/D1MA00644D|s2cid=245723621 |doi-access=free }}</ref>
* Radio lenses <ref>{{cite journal | vauthors = Kokkonen M, Nelo M, Liimatainen H, Ukkola J, Tervo N, Myllymäki S, Juuti J, Jantunen H |title=Wood-based composite materials for ultralight lens antennas in 6G systems |journal=Materials Advances |date=7 February 2022 |volume=3 |issue=3 |pages=1687–1694 |doi=10.1039/D1MA00644D|s2cid=245723621 |doi-access=free}}</ref>


== Related materials ==
==Commercial production==
Nano[[chitin]] is similar in its nanostructure to cellulose nanocrystals but extracted from chitin.
Although wood-driven nanocellulose was first produced in 1983 by Herrick<ref name="Herrick1983" /> and Turbak,<ref name="Turbak1983" /> its commercial production postponed till 2010, mainly due to the high production energy consumption and high production cost. Innventia AB (Sweden) established the first nanocellulose pilot production plant 2010.<ref>{{Cite book|last=Ankerfors|first=Mikael|title=Microfibrillated cellulose: Energy-efficient preparation techniques and key properties|publisher=Licentiate Thesis, Royal Institute of Technology (Sweden)|year=2012|isbn=978-91-7501-464-7|url=https://www.diva-portal.org/smash/get/diva2:557668/FULLTEXT01.pdf}}</ref> Companies and research institutes actively producing micro and nano fibrillated cellulose include: American Process (US), Borregaard (Norway), CelluComp (UK), Chuetsu Pulp and Paper (Japan), CTP/FCBA (France), Daicel (Japan), Dai-ichi Kyogo (Japan), Empa (Switzerland), FiberLean Technologies (UK), InoFib (France), Nano Novin Polymer Co. (Iran), Nippon Paper (Japan), Norske Skog (Norway), Oji Paper (Japan), RISE (Sweden), SAPPI (Netherlands), Seiko PMC (Japan), Stora Enso (Finland), Sugino Machine (Japan), Suzano (Brazil), Tianjin Haojia Cellulose Co. Ltd (China), University of Maine (US), UPM (Finland), US Forest Products Lab (US), VTT (Finland), and Weidmann Fiber Technology (Switzerland).<ref name=":0">{{Cite web|last=Miller|first=Jack|date=Summer 2018|title=2018- Cellulose Nanomaterials Production Update|url=https://www.tappinano.org/media/1266/2018-cellulose-nanomaterials-production-update.pdf|access-date=22 February 2021|website=Tappi Nano}}</ref> Companies and research institutes actively producing cellulose nanocrystals include: Alberta Innovates (Canada), American Process (US), Blue Goose Biorefineries (Canada), CelluForce (Canada), FPInnovations (Canada), Hangzhou Yeuha Technology Co. (China), Melodea (Israel/Sweden), Sweetwater Energy (US), Tianjin Haojia Cellulose Co. Ltd (China), and US Forest Products Lab (US).<ref name=":0" /> Companies and research institutes actively producing cellulose filaments include: Kruger (Canada), Performance BioFilaments (Canada), and Tianjin Haojia Cellulose Co. Ltd (China).<ref name=":0" /> Cellucomp (Scotland) produces [[Curran (material)|Curran]], a root-vegetable based nanocellulose.<ref>{{Cite web |last1=Magazine |first1=Smithsonian |last2=Hansman |first2=Heather |title=Coming Soon: Helmets Made From Carrots |url=https://www.smithsonianmag.com/innovation/coming-soon-helmets-made-from-carrots-180956322/ |access-date=2023-01-10 |website=Smithsonian Magazine |language=en}}</ref>


==See also==
== See also ==
* [[Cellulose]]
* [[Cellulose]]
* [[Cellulose fiber]]
* [[Cellulose fiber]]
Line 150: Line 175:
* [[Composite material]]
* [[Composite material]]


==References==
== References ==
{{Reflist|colwidth=30em|refs=
{{reflist|colwidth=30em|refs=
<ref name="Paakko2007">{{cite journal | vauthors = Pääkkö M, Ankerfors M, Kosonen H, Nykänen A, Ahola S, Osterberg M, Ruokolainen J, Laine J, Larsson PT, Ikkala O, Lindström T | title = Enzymatic hydrolysis combined with mechanical shearing and high-pressure homogenization for nanoscale cellulose fibrils and strong gels | journal = Biomacromolecules | volume = 8 | issue = 6 | pages = 1934–1941 | date = June 2007 | pmid = 17474776 | doi = 10.1021/bm061215p}}</ref>

<ref name="Wagberg2008">{{cite journal | vauthors = Wågberg L, Decher G, Norgren M, Lindström T, Ankerfors M, Axnäs K | title = The build-up of polyelectrolyte multilayers of microfibrillated cellulose and cationic polyelectrolytes | journal = Langmuir | volume = 24 | issue = 3 | pages = 784–795 | date = February 2008 | pmid = 18186655 | doi = 10.1021/la702481v}}</ref>

<ref name="Aulin2009">{{cite journal | vauthors = Aulin C, Ahola S, Josefsson P, Nishino T, Hirose Y, Osterberg M, Wågberg L | title = Nanoscale cellulose films with different crystallinities and mesostructures--their surface properties and interaction with water | journal = Langmuir | volume = 25 | issue = 13 | pages = 7675–7685 | date = July 2009 | pmid = 19348478 | doi = 10.1021/la900323n}}</ref>

<ref name="tatsumi2002">{{cite journal | vauthors = Tatsumi D, Ishioka S, Matsumoto T |year=2002 |title=Effect of Fiber Concentration and Axial Ratio on the Rheological Properties of Cellulose Fiber Suspensions |journal=Journal of the Society of Rheology (Japan) |volume=30 |issue=1 |pages=27–32 |doi=10.1678/rheology.30.27 |doi-access=free}}</ref>

<ref name="Fukuzumi2009">{{cite journal | vauthors = Fukuzumi H, Saito T, Iwata T, Kumamoto Y, Isogai A | title = Transparent and high gas barrier films of cellulose nanofibers prepared by TEMPO-mediated oxidation | journal = Biomacromolecules | volume = 10 | issue = 1 | pages = 162–165 | date = January 2009 | pmid = 19055320 | doi = 10.1021/bm801065u}}</ref>


<ref name="Aulin_2010a">{{cite journal | vauthors = Aulin C, Gällstedt M, Lindström T |s2cid=137623000 |year=2010 |title=Oxygen and oil barrier properties of microfibrillated cellulose films and coatings |journal=Cellulose |volume=17 |issue=3 |pages=559–574 |doi=10.1007/s10570-009-9393-y}}</ref>
<ref name="Turbak1983">{{cite conference|last= Turbak |first=A.F. |author2=F.W. Snyder |author3=K.R. Sandberg|year=1983| editor= A. Sarko|title=Microfibrillated cellulose, a new cellulose product: Properties, uses and commercial potential|book-title=Proceedings of the Ninth Cellulose Conference |location= New York City |publisher=Wiley |series=Applied Polymer Symposia, '''37'''|pages=815–827|isbn= 0-471-88132-5}}</ref>


<ref name="Eichhorn review 2010">{{cite journal| vauthors = Eichhorn SJ, Dufresne A, Aranguren M, Marcovich NE, Capadona JR, Rowan SJ, Weder C, Thielemans W, Roman M, Renneckar S, Gindl W, Veigel A, Keckes J, Yano H, Abe AN, Nakagaito A, Mangalam J, Simonsen AS, Benight AS, Bismarck LA, Berglund T |s2cid=137519458|title=Review: current international research into cellulose nanofibres and nanocomposites|journal=Journal of Materials Science|year=2010|volume=45|issue=1|pages=1–33|doi=10.1007/s10853-009-3874-0|bibcode = 2010JMatS..45....1E |url=http://doc.rero.ch/record/17566/files/wed_rci.pdf}}</ref>
<ref name="Turbak, A, F., Snyder, F.W. and Sandberg, K.R.">Turbak, A.F., F.W. Snyder, and K.R. Sandberg {{US Patent|4341807}}; {{US Patent|4374702}}; {{US Patent|4378381}}; {{US Patent|4452721}}; {{US Patent|4452722}}; {{US Patent|4464287}}; {{US Patent|4483743}}; {{US Patent|4487634}}; {{US Patent|4500546}}</ref>


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<ref name="Herrick1983">{{cite conference|last= Herrick |first=F.W. |author2=R.L. Casebier |author3=J.K. Hamilton |author4=K.R. Sandberg|year=1983| editor= A. Sarko|title=Microfibrillated cellulose: morphology and accessibility|book-title=Proceedings of the Ninth Cellulose Conference |location= New York City |publisher=Wiley |series=Applied Polymer Symposia, '''37'''|pages=797–813|isbn= 0-471-88132-5}}</ref>


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<ref name="Siro2010">{{cite journal |last=Siró |first=István |author2=David Plackett |s2cid=14319488 |year=2010 |title=Microfibrillated cellulose and new nanocomposite materials: a review |journal=Cellulose |volume=17 |issue=3 |pages=459–494 |doi=10.1007/s10570-010-9405-y}}</ref>
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<ref name="Henriksson2008">{{cite journal | vauthors = Henriksson M, Berglund LA, Isaksson P, Lindström T, Nishino T | title = Cellulose nanopaper structures of high toughness | journal = Biomacromolecules | volume = 9 | issue = 6 | pages = 1579–1585 | date = June 2008 | pmid = 18498189 | doi = 10.1021/bm800038n | doi-access = free}}</ref>
<ref name="Paakko2007">{{cite journal |last=Pääkkö |first= M. |author2=M. Ankerfors |author3=H. Kosonen |author4=A. Nykänen |author5=S. Ahola |author6=M. Österberg |author7=J. Ruokolainen |author8=J. Laine |author9=P.T. Larsson |author10=O. Ikkala |author11=T. Lindström |year=2007 |title=Enzymatic hydrolysis combined with mechanical shearing and high-pressure homogenization for nanoscale cellulose fibrils and strong gels |journal=Biomacromolecules |volume=8 |issue= 6|pages=1934–1941 |doi=10.1021/bm061215p |pmid=17474776}}</ref>


<ref name="Wagberg2008">{{cite journal |last=Wågberg |first=Lars |author2=Gero Decher |author3=Magnus Norgren |author4=Tom Lindström |author5=Mikael Ankerfors |author6=Karl Axnäs |year=2008 |title=The build-up of polyelectrolyte multilayers of microfibrillated cellulose and cationic polyelectrolytes |journal=Langmuir |volume=24 |issue=3 |pages=784–795 |doi=10.1021/la702481v |pmid=18186655}}</ref>
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<ref name="Fukuzumi2009">{{cite journal |last=Fukuzumi |first=Hayaka |author2=Tsuguyuki Saito |author3=Tadahisa Iwata |author4=Yoshiaki Kumamoto |author5=Akira Isogai |year=2009 |title=Transparent and high gas barrier films of cellulose nanofibers prepared by TEMPO-mediated oxidation |journal= Biomacromolecules |volume=10 |issue=1 |pages=162–165 |doi=10.1021/bm801065u |pmid=19055320}}</ref>
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<ref name="Aulin2010a">{{cite journal |last=Aulin |first=Christian |author2=Mikael Gällstedt |author3=Tom Lindström |s2cid=137623000 |year=2010 |title=Oxygen and oil barrier properties of microfibrillated cellulose films and coatings |journal=Cellulose |volume=17 |issue=3 |pages=559–574 |doi=10.1007/s10570-009-9393-y}}</ref>
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<ref name="Syverud2009">{{cite journal |last=Syverud |first=Kristin |author2=Per Stenius |s2cid=136647719 |year= 2009|title=Strength and barrier properties of MFC films |journal=Cellulose |volume=16 |issue=1 |pages=75–85 |doi=10.1007/s10570-008-9244-2}}</ref>
<ref name="Heath2010">{{cite journal| vauthors = Heath L, Thielemans W |title=Cellulose nanowhisker aerogels|journal=Green Chemistry|year=2010|volume=12|pages=1448–1453|doi=10.1039/c0gc00035c|issue=8}}</ref>


<ref name="Labet2011">{{cite journal| vauthors = Labet M, Thielemans W |s2cid=93187820| year=2011 | title=Improving the reproducibility of chemical reactions on the surface of cellulose nanocrystals: ROP of e-caprolactone as a case study|journal=Cellulose|volume=18|pages=607–617|doi=10.1007/s10570-011-9527-x|issue=3}}</ref>
<ref name="Henriksson2007">{{cite journal |last=Henriksson |first=Marielle |author2=Lars Berglund |year=2007 |title=Structure and properties of cellulose nanocomposite films containing melamine formaldehyde |journal=Journal of Applied Polymer Science |volume=106 |issue=4 |pages=2817–2824 |doi=10.1002/app.26946 |url=http://intra.kth.se/polopoly_fs/1.23850!SAPOC_MH.pdf }}{{Dead link|date=April 2020 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>


<ref name="Svagan2007">{{cite journal |vauthors = Svagan AJ, Samir MA, Berglund LA |year=2007 |title=Biomimetic polysaccharide nanocomposites of high cellulose content and high toughness |journal=Biomacromolecules |volume=8 |issue=8 |pages=2556–2563 |doi=10.1021/bm0703160 |pmid=17655354}}</ref>
<ref name="Vartiainen2011">{{cite journal| vauthors = Vartiainen J, Pöhler T, Sirola K, Pylkkänen L, Alenius H, Hokkinen J, Tapper U, Lahtinen P, Kapanen A, Putkisto K, Hiekkataipale P |s2cid=137455453 | year=2011 |title=Health and environmental safety aspects of friction grinding and spray drying of microfibrillated cellulose|journal=Cellulose|volume=18|pages=775–786|doi=10.1007/s10570-011-9501-7|issue=3}}</ref>


<ref name="Henriksson2008">{{cite journal |last=Henriksson |first=Marielle |author2=Lars A. Berglund |author3=Per Isaksson |author4=Tom Lindström |author5=Takashi Nishino |year=2008 |title=Cellulose nanopaper structures of high toughness |journal=Biomacromolecules |volume=9 |issue=6 |pages=1579–1585 |doi=10.1021/bm800038n |pmid=18498189|doi-access=free }}</ref>
<ref name="Mittal_2018">{{cite journal | vauthors = Mittal N, Ansari F, Gowda VK, Brouzet C, Chen P, Larsson PT, Roth SV, Lundell F, Wågberg L, Kotov NA, Söderberg LD | title = Multiscale Control of Nanocellulose Assembly: Transferring Remarkable Nanoscale Fibril Mechanics to Macroscale Fibers | journal = ACS Nano | volume = 12 | issue = 7 | pages = 6378–6388 | date = July 2018 | pmid = 29741364 | doi = 10.1021/acsnano.8b01084 | doi-access = free}}</ref>


<ref name=":0">{{Cite journal |last1=Charreau |first1=Hernan |last2=L. Foresti |first2=Maria |last3=Vazquez |first3=Analia |date=2013-01-01 |title=Nanocellulose Patents Trends: A Comprehensive Review on Patents on Cellulose Nanocrystals, Microfibrillated and Bacterial Cellulose |url=https://www.ingentaconnect.com/content/ben/nanotec/2013/00000007/00000001/art00006;jsessionid=2i1ihw27ek77e.x-ic-live-02 |journal=Recent Patents on Nanotechnology |volume=7 |issue=1 |pages=56–80 |doi=10.2174/187221013804484854|pmid=22747719 |hdl=11336/14848 |hdl-access=free }}</ref>
<ref name=Diddens2008>{{cite journal |last=Diddens |first=Imke |author2=Bridget Murphy |author3=Michael Krisch |author4=Martin Müller |year=2008 |title=Anisotropic elastic properties of cellulose measured using inelastic x-ray scattering |journal=Macromolecules |volume=41 |issue=24 |pages=9755–9759 |doi=10.1021/ma801796u|bibcode = 2008MaMol..41.9755D }}</ref>


<ref name=":4">{{cite web |title=Engineering Algae to Make the 'Wonder Material' Nanocellulose for Biofuels and More |url=http://www.newswise.com/articles/engineering-algae-to-make-the-wonder-material-nanocellulose-for-biofuels-and-more |website=newswise.com}}</ref>
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<ref name=":3">{{cite patent |country=US |number=4,374,702 |inventor= |invent1=Turbak |invent2=Snyder |invent3=Sandberg|title=Microfibrillated cellulose |pubdate=1983-02-23 | assign1=International Telephone and Telegraph Corporation, New York, N.Y |url=https://patentimages.storage.googleapis.com/f7/6f/9f/391f0430aa4ebc/US4374702.pdf}}</ref>
<ref name="Paako2008">{{cite journal |last=Pääkkö |first=Marjo |author2=Jaana Vapaavuori |author3=Riitta Silvennoinen |author4=Harri Kosonen |author5=Mikael Ankerfors |author6=Tom Lindström |author7=Lars A. Berglund |author8=Olli Ikkala |year=2008 |title=Long and entangled nantive cellulose I nanofibers allow flexible aerogels and hierarchically templates for functionalities |journal=Soft Matter |volume=4 |pages=2492–2499 |doi=10.1039/b810371b |issue=12|bibcode = 2008SMat....4.2492P }}</ref>


<ref name="ns">{{cite web|url=https://www.newscientist.com/article/mg21528786.100-why-wood-pulp-is-worlds-new-wonder-material.html |title=Why wood pulp is world's new wonder material – tech – 23 August 2012 |publisher=New Scientist |access-date=2012-08-30}}</ref>
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<ref name="Lightweight, Tough, and Sustainable">{{cite journal | vauthors = Guan QF, Yang HB, Han ZM, Zhou LC, Zhu YB, Ling ZC, Jiang HB, Wang PF, Ma T, Wu HA, Yu SH | title = Lightweight, tough, and sustainable cellulose nanofiber-derived bulk structural materials with low thermal expansion coefficient | journal = Science Advances | volume = 6 | issue = 18 | pages = eaaz1114 | date = May 2020 | pmid = 32494670 | pmc = 7195169 | doi = 10.1126/sciadv.aaz1114 | publisher = American Association for the Advancement of Science | bibcode = 2020SciA....6.1114G}}</ref>
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<ref name="bio">{{cite journal | vauthors = Jung YH, Chang TH, Zhang H, Yao C, Zheng Q, Yang VW, Mi H, Kim M, Cho SJ, Park DW, Jiang H, Lee J, Qiu Y, Zhou W, Cai Z, Gong S, Ma Z | title = High-performance green flexible electronics based on biodegradable cellulose nanofibril paper | journal = Nature Communications | volume = 6 | pages = 7170 | date = May 2015 | pmid = 26006731 | pmc = 4455139 | doi = 10.1038/ncomms8170 | bibcode = 2015NatCo...6.7170J}}</ref>
<ref name="Lindstrom2009">{{cite conference |last=Lindström |first=Tom |author2=Mikael Ankerfors |year=2009 |book-title=7th International Paper and Coating Chemistry Symposium |title=NanoCellulose Developments in Scandinavia |location=Hamilton, Ontario |publisher=McMaster University Engineering |edition=Preprint CD |isbn= 978-0-9812879-0-4}}</ref>


<ref name="permselective2009">{{cite journal|last=Thielemans|first=Wim|author2=Warbey, C.A |author3=Walsh, D.A. |title=Permselective nanostructured membranes based on cellulose nanowhiskers|journal=Green Chemistry|year=2009|volume=11|pages=531–537|doi=10.1039/b818056c|issue=4}}</ref>
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<ref name="Heath2010">{{cite journal|last=Heath|first=Lindy|author2=Thielemans, W.|title=Cellulose nanowhisker aerogels|journal=Green Chemistry|year=2010|volume=12|pages=1448–1453|doi=10.1039/c0gc00035c|issue=8}}</ref>
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<ref name="Kumar 3603–3613">{{Cite journal| vauthors = Kumar V, Elfving A, Koivula H, Bousfield D, Toivakka M |date=2016-03-30|title=Roll-to-Roll Processed Cellulose Nanofiber Coatings|journal=Industrial & Engineering Chemistry Research|language=en|volume=55|issue=12|pages=3603–3613|doi=10.1021/acs.iecr.6b00417|issn=0888-5885}}</ref>
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<ref name="NyströmMarais2015">{{cite journal | vauthors = Nyström G, Marais A, Karabulut E, Wågberg L, Cui Y, Hamedi MM | title = Self-assembled three-dimensional and compressible interdigitated thin-film supercapacitors and batteries | journal = Nature Communications | volume = 6 | pages = 7259 | date = May 2015 | pmid = 26021485 | pmc = 4458871 | doi = 10.1038/ncomms8259 | bibcode = 2015NatCo...6.7259N}}</ref>
<ref name="Mittal2018">{{cite journal|last=Mittal|first=N. |author2=Ansari, F. |author3=Gowda V., K. |author4=Brouzet, C. |author5=Chen, P. |author6=Larsson, P.T. |author7=Roth, S.V. |author8=Lundell, F. |author9=Wågberg, L. |author10=Kotov, N. |author11=Söderberg, L.D. |title=Multiscale Control of Nanocellulose Assembly: Transferring Remarkable Nanoscale Fibril Mechanics to Macroscale Fibers|journal=ACS Nano|volume=12 |issue=7 |pages=6378–6388 |doi=10.1021/acsnano.8b01084|pmid=29741364 |year=2018 |url=http://bib-pubdb1.desy.de/record/418232 |doi-access=free }}</ref>}}
}}
{{Commons category|Cellulose derivatives }}
{{Commons category|Cellulose derivatives }}
{{Wood products}}
{{Wood products}}

Latest revision as of 20:35, 27 November 2024

Nanocellulose is a term referring to a family of cellulosic materials that have at least one of their dimensions in the nanoscale. Examples of nanocellulosic materials are microfibrilated cellulose, cellulose nanofibers or cellulose nanocrystals. Nanocellulose may be obtained from natural cellulose fibers through a variety of production processes. This family of materials possesses interesting properties suitable for a wide range of potential applications.

Terminology

[edit]

Microfibrilated cellulose

[edit]

Micro cellulose (MFC) is a type of nanocellulose that is more heterogeneous than cellulose nanofibers or nanocrystals as it contains a mixture of nano- and micron-scale particles. The term is sometimes misused to refer to cellulose nanofibers instead.[1][2]

Cellulose nanofibers

[edit]

Cellulose nanofibers (CNF), also called nanofibrillated cellulose (NFC), are nanosized cellulose fibrils with a high aspect ratio (length to width ratio). Typical fibril widths are 5–20 nanometers with a wide range of lengths, typically several micrometers.

The fibrils can be isolated from natural cellulose, generally wood pulp, through high-pressure, high temperature and high velocity impact homogenization, grinding or microfluidization (see manufacture below).[3][4][5]

TEM image of CNCs made from cotton cellulose

Cellulose nanocrystals

[edit]

Cellulose nanocrystals (CNCs), or nanocrystalline cellulose (NCC), are highly crystalline, rod-like nanoparticles.[6][7] They are usually covered by negatively charged groups that render them colloidally stable in water. They are typically shorter than CNFs, with a typical length of 100 to 1000 nanometers.[8]

Bacterial nanocellulose

[edit]

Some cellulose producing bacteria have also been used to produce nanocellulosic materials that are then referred to as bacterial nanocellulose.[9] The most common examples being Medusomyces gisevii (the bacteria involved in the making of Kombucha) and Komagataeibacter xylinus (involve in the fabrication of Nata de coco), see bacterial cellulose for more details. This naming distinction might arise from the very peculiar morphology of these materials compared to the more traditional ones made of wood or cotton cellulose. In practice, bacterial nanocellulosic materials are often larger than their wood or cotton counterparts.

History

[edit]

The discovery of nanocellulosic materials can be traced back to late 1940s studies on the hydrolysis of cellulose fibers.[2] Eventually it was noticed that cellulose hydrolysis seemed to occur preferentially at some disordered intercrystalline portions of the fibers.[10] This led to the obtention of colloidally stable and highly crystalline nanorods particles.[11][12][13] These particles were first referred to as micelles, before being given multiple names including cellulose nanocrystals (CNCs), nanocrystalline cellulose (NCC), or cellulose (nano)whiskers, though this last term is less used today.[2] Later studies by O. A. Battista showed that in milder hydrolysis conditions, the crystalline nanorods stay aggregated as micron size objects.[14][15] This material was later referred to as microcrystalline cellulose (MCC) and commercialised under the name Avicel by FMC Corporation.[16]

Nanocellulose gel (probably MFC of NFC)

Microfibrillated cellulose (MFC) was discovered later, in the 1980s, by Turbak, Snyder and Sandberg at the ITT Rayonier labs in Shelton, Washington.[17][18][19] This terminology was used to describe a gel-like material prepared by passing wood pulp through a Gaulin type milk homogenizer at high temperatures and high pressures followed by ejection impact against a hard surface. In later work, F. W. Herrick at ITT Rayonier Eastern Research Division (ERD) Lab in Whippany also published work on making a dry powder form of the gel.[20][19] Rayonier, as a company, never pursued scale-up and gave free license to whoever wanted to pursue this new use for cellulose.[citation needed] Rather, Turbak et al. pursued 1) finding new uses for the MFC, including using as a thickener and binder in foods, cosmetics, paper formation, textiles, nonwovens, etc. and 2) evaluate swelling and other techniques for lowering the energy requirements for MFC production.[21] The first MFC pilot production plant of MFC was established in 2010 by Innventia AB (Sweden).[22]

Manufacture

[edit]

Cellulose sources

[edit]

Nanocellulose materials can be prepared from any natural cellulose source including wood, cotton, agricultural[23] or household wastes,[24] algae,[25] bacteria or tunicate. Wood, in the form of wood pulp is currently the most commonly used starting material for the industrial production of nanocellulosic materials.

Nanocellulose fibrils

[edit]

Nanocellulose fibrils (MFC and CNFs) may be isolated from the cellulose fibers using mechanical methods that expose the fibers to high shear forces, delaminating them into nano-fibers. For this purpose, high-pressure homogenizers, grinders or microfluidizers can be used.[citation needed] This process consumes very large amounts of energy and values over 30 MWh/tonne are not uncommon.[citation needed]

To address this problem, sometimes enzymatic/mechanical pre-treatments and introduction of charged groups for example through carboxymethylation or TEMPO-mediated oxidation are used.[26] These pre-treatments can decrease energy consumption below 1 MWh/tonne.[citation needed] "Nitro-oxidation" has been developed to prepare carboxycellulose nanofibers directly from raw plant biomass. Owing to fewer processing steps to extract nanocellulose, the nitro-oxidation method has been found to be a cost-effective, less-chemically oriented and efficient method to extract carboxycellulose nanofibers.[27][28] Functionalized nanofibers obtained using nitro-oxidation have been found to be an excellent substrate to remove heavy metal ion impurities such as lead,[29] cadmium,[30] and uranium.[31]

A chemo-mechanical process for production of nanocellulose from cotton linters has been demonstrated with a capacity of 10 kg per day.[32]

Cellulose nanocrystals

[edit]

Cellulose nanocrystals (CNC) are formed by the acid hydrolysis of native cellulose fibers, most commonly using sulfuric or hydrochloric acid. Disordered sections of native cellulose are hydrolysed and after careful timing, the remaining crystalline sections can be retrieved from the acid solution by centrifugation and dialysis against water. Their final dimensions depend on the cellulose source, its history, the hydrolysis conditions and the purification procedures.[33] CNCs are commercialised by various companies that use different sources and processes, leading to a range of available products.[34][35]

Other cellulose based nanoparticles

[edit]

Spherical shaped carboxycellulose nanoparticles prepared by nitric acid-phosphoric acid treatment are stable in dispersion in its non-ionic form.[36]

Structure and properties

[edit]
AFM height image of carboxymethylated nanocellulose adsorbed on a silica surface. The scanned surface area is 1 μm2.

Dimensions and crystallinity

[edit]

The ultrastructure of nanocellulose derived from various sources has been extensively studied. Techniques such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), wide angle X-ray scattering (WAXS), small incidence angle X-ray diffraction and solid state 13C cross-polarization magic angle spinning (CP/MAS), nuclear magnetic resonance (NMR) and spectroscopy have been used to characterize typically dried nanocellulose morphology.[citation needed]

A combination of microscopic techniques with image analysis can provide information on fibril widths, it is more difficult to determine fibril lengths, because of entanglements and difficulties in identifying both ends of individual nanofibrils.[37][38][page needed] Also, nanocellulose suspensions may not be homogeneous and can consist of various structural components, including cellulose nanofibrils and nanofibril bundles.[39]

In a study of enzymatically pre-treated nanocellulose fibrils in a suspension the size and size-distribution were established using cryo-TEM. The fibrils were found to be rather mono-dispersed mostly with a diameter of ca. 5 nm although occasionally thicker fibril bundles were present.[40] By combining ultrasonication with an "oxidation pretreatment", cellulose microfibrils with a lateral dimension below 1 nm has been observed by AFM. The lower end of the thickness dimension is around 0.4 nm, which is related to the thickness of a cellulose monolayer sheet.[41]

Aggregate widths can be determined by CP/MAS NMR developed by Innventia AB, Sweden, which also has been demonstrated to work for nanocellulose (enzymatic pre-treatment). An average width of 17 nm has been measured with the NMR-method, which corresponds well with SEM and TEM. Using TEM, values of 15 nm have been reported for nanocellulose from carboxymethylated pulp. However, thinner fibrils can also be detected. Wågberg et al. reported fibril widths of 5–15 nm for a nanocellulose with a charge density of about 0.5 meq./g.[42] The group of Isogai reported fibril widths of 3–5 nm for TEMPO-oxidized cellulose having a charge density of 1.5 meq./g.[43]

Pulp chemistry has a significant influence on nanocellulose microstructure. Carboxymethylation increases the numbers of charged groups on the fibril surfaces, making the fibrils easier to liberate and results in smaller and more uniform fibril widths (5–15 nm) compared to enzymatically pre-treated nanocellulose, where the fibril widths were 10–30 nm.[44] The degree of crystallinity and crystal structure of nanocellulose. Nanocellulose exhibits cellulose crystal I organization and the degree of crystallinity is unchanged by the preparation of the nanocellulose. Typical values for the degree of crystallinity were around 63%.[44]

Viscosity

[edit]

The rheology of nanocellulose dispersions has been investigated.[45][40] and revealed that the storage and loss modulus were independent of the angular frequency at all nanocellulose concentrations between 0.125% to 5.9%. The storage modulus values are particularly high (104 Pa at 3% concentration)[40] compared to results for CNCs (102 Pa at 3% concentration).[45] There is also a strong concentration dependence as the storage modulus increases 5 orders of magnitude if the concentration is increased from 0.125% to 5.9%. Nanocellulose gels are also highly shear thinning (the viscosity is lost upon introduction of the shear forces). The shear-thinning behaviour is particularly useful in a range of different coating applications.[40]

It is pseudo-plastic and exhibits thixotropy, the property of certain gels or fluids that are thick (viscous) under normal conditions, but become less viscous when shaken or agitated. When the shearing forces are removed the gel regains much of its original state.

Mechanical properties

[edit]

Crystalline cellulose has a stiffness about 140–220 GPa, comparable with that of Kevlar and better than that of glass fiber, both of which are used commercially to reinforce plastics. Films made from nanocellulose have high strength (over 200 MPa), high stiffness (around 20 GPa)[46] but lack of high strain[clarification needed] (12%). Its strength/weight ratio is 8 times that of stainless steel.[47] Fibers made from nanocellulose have high strength (up to 1.57 GPa) and stiffness (up to 86 GPa).[48]

Barrier properties

[edit]

In semi-crystalline polymers, the crystalline regions are considered to be gas impermeable. Due to relatively high crystallinity,[44] in combination with the ability of the nanofibers to form a dense network held together by strong inter-fibrillar bonds (high cohesive energy density), it has been suggested that nanocellulose might act as a barrier material.[43][49][50] Although the number of reported oxygen permeability values are limited, reports attribute high oxygen barrier properties to nanocellulose films. One study reported an oxygen permeability of 0.0006 (cm3 μm)/(m2 day kPa) for a ca. 5 μm thin nanocellulose film at 23 °C and 0% RH.[49] In a related study, a more than 700-fold decrease in oxygen permeability of a polylactide (PLA) film when a nanocellulose layer was added to the PLA surface was reported.[43]

The influence of nanocellulose film density and porosity on film oxygen permeability has been explored.[51] Some authors have reported significant porosity in nanocellulose films,[52][46][53] which seems to be in contradiction with high oxygen barrier properties, whereas Aulin et al.[49] measured a nanocellulose film density close to density of crystalline cellulose (cellulose Iß crystal structure, 1.63 g/cm3)[54] indicating a very dense film with a porosity close to zero.

Changing the surface functionality of the cellulose nanoparticle can also affect the permeability of nanocellulose films. Films constituted of negatively charged CNCs could effectively reduce permeation of negatively charged ions, while leaving neutral ions virtually unaffected. Positively charged ions were found to accumulate in the membrane.[55]

Multi-parametric surface plasmon resonance is one of the methods to study barrier properties of natural, modified or coated nanocellulose. The different antifouling, moisture, solvent, antimicrobial barrier formulation quality can be measured on the nanoscale. The adsorption kinetics as well as the degree of swelling can be measured in real-time and label-free.[56][57]

Liquid crystals, colloidal glasses, and hydrogels

[edit]

Owed to their anisotropic shape and surface charge, nanocelluloses (mostly rigid CNCs) have a high excluded volume and self-assemble into cholesteric liquid crystals beyond a critical volume fraction.[58] Nanocellulose liquid crystals are left-handed due to the right-handed twist on particle level.[59] Nanocellulose phase behavior is susceptible to ionic charge screening. An increase in ionic strength induces the arrest of nanocellulose dispersions into attractive glasses.[60] At further increasing ionic strength, nanocelluloses aggregate into hydrogels.[61] The interactions within nanocelluloses are weak and reversible, wherefore nanocellulose suspensions and hydrogels are self-healing and may be applied as injectable materials[62] or 3D printing inks.[63]

Bulk foams and aerogels

[edit]

Nanocellulose can also be used to make aerogels/foams, either homogeneously or in composite formulations. Nanocellulose-based foams are being studied for packaging applications in order to replace polystyrene-based foams. Svagan et al. showed that nanocellulose has the ability to reinforce starch foams by using a freeze-drying technique.[64] The advantage of using nanocellulose instead of wood-based pulp fibers is that the nanofibrils can reinforce the thin cells in the starch foam. Moreover, it is possible to prepare pure nanocellulose aerogels applying various freeze-drying and super critical CO
2
drying techniques. Aerogels and foams can be used as porous templates.[65][66] Tough ultra-high porosity foams prepared from cellulose I nanofibril suspensions were studied by Sehaqui et al. a wide range of mechanical properties including compression was obtained by controlling density and nanofibril interaction in the foams.[67] CNCs could also be made to gel in water under low power sonication giving rise to aerogels with the highest reported surface area (>600m2/g) and lowest shrinkage during drying (6.5%) of cellulose aerogels.[66] In another study by Aulin et al.,[68] the formation of structured porous aerogels of nanocellulose by freeze-drying was demonstrated. The density and surface texture of the aerogels was tuned by selecting the concentration of the nanocellulose dispersions before freeze-drying. Chemical vapour deposition of a fluorinated silane was used to uniformly coat the aerogel to tune their wetting properties towards non-polar liquids/oils. The authors demonstrated that it is possible to switch the wettability behaviour of the cellulose surfaces between super-wetting and super-repellent, using different scales of roughness and porosity created by the freeze-drying technique and change of concentration of the nanocellulose dispersion. Structured porous cellulose foams can however also be obtained by utilizing the freeze-drying technique on cellulose generated by Gluconobacter strains of bacteria, which bio-synthesize open porous networks of cellulose fibers with relatively large amounts of nanofibrils dispersed inside. Olsson et al.[69] demonstrated that these networks can be further impregnated with metalhydroxide/oxide precursors, which can readily be transformed into grafted magnetic nanoparticles along the cellulose nanofibers. The magnetic cellulose foam may allow for a number of novel applications of nanocellulose and the first remotely actuated magnetic super sponges absorbing 1 gram of water within a 60 mg cellulose aerogel foam were reported. Notably, these highly porous foams (>98% air) can be compressed into strong magnetic nanopapers, which may find use as functional membranes in various applications.

Pickering emulsions and foams

[edit]

Nanocelluloses can stabilize emulsions and foams by a Pickering mechanism, i.e. they adsorb at the oil-water or air-water interface and prevent their energetic unfavorable contact. Nanocelluloses form oil-in-water emulsions with a droplet size in the range of 4-10 μm that are stable for months and can resist high temperatures and changes in pH.[70][71] Nanocelluloses decrease the oil-water interface tension[72] and their surface charge induces electrostatic repulsion within emulsion droplets. Upon salt-induced charge screening the droplets aggregate but do not undergo coalescence, indicating strong steric stabilization.[73] The emulsion droplets even remain stable in the human stomach and resist gastric lipolysis, thereby delaying lipid absorption and satiation.[74][75] In contrast to emulsions, native nanocelluloses are generally not suitable for the Pickering stabilization of foams, which is attributed to their primarily hydrophilic surface properties that results in an unfavorable contact angle below 90° (they are preferably wetted by the aqueous phase).[76] Using hydrophobic surface modifications or polymer grafting, the surface hydrophobicity and contact angle of nanocelluloses can be increased, allowing also the Pickering stabilization of foams.[77] By further increasing the surface hydrophobicity, inverse water-in-oil emulsions can be obtained, which denotes a contact angle higher than 90°.[78][79] It was further demonstrated that nanocelluloses can stabilize water-in-water emulsions in presence of two incompatible water-soluble polymers.[80]

Cellulose nanofiber plate

[edit]

A bottom up approach can be used to create a high-performance bulk material with low density, high strength and toughness, and great thermal dimensional stability: cellulose nanofiber plate (CNFP). Cellulose nanofiber hydrogel is created by biosynthesis. The hydrogels can then be treated with a polymer solution or by surface modification and then are hot-pressed at 80 °C. The result is bulk material with excellent machinability. “The ultrafine nanofiber network structure in CNFP results in more extensive hydrogen bonding, the high in-plane orientation, and “three way branching points” of the microfibril networks”.[81] This structure gives CNFP its high strength by distributing stress and adding barriers to crack formation and propagation. The weak link in this structure is bond between the pressed layers which can lead to delamination. To reduce delamination, the hydrogel can be treated with silicic acid, which creates strong covalent cross-links between layers during hot pressing.[81]

Surface modification

[edit]

The surface modification of nanocellulose is currently receiving a large amount of attention.[82] Nanocellulose displays a high concentration of hydroxyl groups at the surface which can be reacted. However, hydrogen bonding strongly affects the reactivity of the surface hydroxyl groups. In addition, impurities at the surface of nanocellulose such as glucosidic and lignin fragments need to be removed before surface modification to obtain acceptable reproducibility between different batches.[83]

Safety aspects

[edit]

Processing of nanocellulose does not cause significant exposure to fine particles during friction grinding or spray drying. No evidence of inflammatory effects or cytotoxicity on mouse or human macrophages can be observed after exposure to nanocellulose. The results of toxicity studies suggest that nanocellulose is not cytotoxic and does not cause any effects on inflammatory system in macrophages. In addition, nanocellulose is not acutely toxic to Vibrio fischeri in environmentally relevant concentrations.[84]

Despite intensified research on oral food or pharmaceutical formulations containing nanocelluloses they are not generally recognized as safe. Nanocelluloses were demonstrated to exhibit limited toxicity and oxidative stress in in vitro intestinal epithelium[85][86][87] or animal models.[88][89][90]

Potential applications

[edit]
Cellulose nanocrystals self-organized into Bio Iridescent Sequin.

The properties of nanocellulose (e.g. mechanical properties, film-forming properties, viscosity etc.) makes it an interesting material for many applications.[91]

Cellulose nanocrystals self-organized into RGB glittery pigment particles.
Nanocellulose recycling chart[92]
GaAs electronics on nanocellulose substrate[93]

Paper and paperboard

[edit]
Bendable solar cell on nanocellulose substrate

In the area of paper and paperboard manufacture, nanocelluloses are expected to enhance the fiber-fiber bond strength and, hence, have a strong reinforcement effect on paper materials.[94][95][96] Nanocellulose may be useful as a barrier in grease-proof type of papers and as a wet-end additive to enhance retention, dry and wet strength in commodity type of paper and board products.[97][98][99][100] It has been shown that applying CNF as a coating material on the surface of paper and paperboard improves the barrier properties, especially air resistance[101] and grease/oil resistance.[101][102][97] It also enhances the structure properties of paperboards (smoother surface).[103] Very high viscosity of MFC/CNF suspensions at low solids content limits the type of coating techniques that can be utilized to apply these suspensions onto paper/paperboard. Some of the coating methods utilized for MFC surface application onto paper/paperboard have been rod coating,[98] size press,[102] spray coating,[104] foam coating [105] and slot-die coating.[101] Wet-end surface application of mineral pigments and MFC mixture to improve barrier, mechanical and printing properties of paperboard are also being explored.[106]

Nanocellulose can be used to prepare flexible and optically transparent paper. Such paper is an attractive substrate for electronic devices because it is recyclable, compatible with biological objects, and easily biodegrades.[93]

Composite

[edit]

As described above the properties of the nanocellulose makes an interesting material for reinforcing plastics. Nanocellulose can be spun into filaments that are stronger and stiffer than spider silk.[48][107] Nanocellulose has been reported to improve the mechanical properties of thermosetting resins, starch-based matrixes, soy protein, rubber latex, poly(lactide). Hybrid cellulose nanofibrils-clay minerals composites present interesting mechanical, gas barrier and fire retardancy properties.[108] The composite applications may be for use as coatings and films,[109] paints, foams, packaging.

Food

[edit]

Nanocellulose can be used as a low calorie replacement for carbohydrate additives used as thickeners, flavour carriers, and suspension stabilizers in a wide variety of food products.[110] It is useful for producing fillings, crushes, chips, wafers, soups, gravies, puddings etc. The food applications arise from the rheological behaviour of the nanocellulose gel.

Hygiene and absorbent products

[edit]

Applications in this field include: super water absorbent material (e.g. for incontinence pads material), nanocellulose used together with super absorbent polymers, nanocellulose in tissue, non-woven products or absorbent structures and as antimicrobial films.[citation needed]

Emulsion and dispersion

[edit]

Nanocellulose has potential applications in the general area of emulsion and dispersion applications in other fields.[111][112]

Medical, cosmetic and pharmaceutical

[edit]

The use of nanocellulose in cosmetics and pharmaceuticals has been suggested:

  • Freeze-dried nanocellulose aerogels used in sanitary napkins, tampons, diapers or as wound dressing
  • The use of nanocellulose as a composite coating agent in cosmetics e.g. for hair, eyelashes, eyebrows or nails
  • A dry solid nanocellulose composition in the form of tablets for treating intestinal disorders
  • Nanocellulose films for screening of biological compounds and nucleic acids encoding a biological compound
  • Filter medium partly based on nanocellulose for leukocyte free blood transfusion
  • A buccodental formulation, comprising nanocellulose and a polyhydroxylated organic compound
  • Powdered nanocellulose has also been suggested as an excipient in pharmaceutical compositions
  • Nanocellulose in compositions of a photoreactive noxious substance purging agent
  • Elastic cryo-structured gels for potential biomedical and biotechnological application[113]
  • Matrix for 3D cell culture

Bio-based electronics and energy storage

[edit]

Nanocellulose can pave the way for a new type of "bio-based electronics" where interactive materials are mixed with nanocellulose to enable the creation of new interactive fibers, films, aerogels, hydrogels and papers.[114] E.g. nanocellulose mixed with conducting polymers such as PEDOT:PSS show synergetic effects resulting in extraordinary[115] mixed electronic and ionic conductivity, which is important for energy storage applications. Filaments spun from a mix of nanocellulose and carbon nanotubes show good conductivity and mechanical properties.[116] Nanocellulose aerogels decorated with carbon nanotubes can be constructed into robust compressible 3D supercapacitor devices.[117][118] Structures from nanocellulose can be turned into bio-based triboelectric generators[119] and sensors.

In April 2013 breakthroughs in nanocellulose production, by algae, were announced at an American Chemical Society conference, by speaker R. Malcolm Brown, Jr., Ph.D, who has pioneered research in the field for more than 40 years, spoke at the First International Symposium on Nanocellulose, part of the American Chemical Society meeting. Genes from the family of bacteria that produce vinegar, Kombucha tea and nata de coco have become stars in a project — which scientists said has reached an advanced stage - that would turn algae into solar-powered factories for producing the “wonder material” nanocellulose.[9]

Bio-based coloured materials

[edit]

Cellulose nanocrystals have shown the possibility to self organize into chiral nematic structures[120] with angle-dependent iridescent colours. It is thus possible to manufacture totally bio-based pigments and glitters, films including sequins having a metallic glare and a small footprint compared to fossil-based alternatives.

Other potential applications

[edit]
  • As a highly scattering material for ultra-white coatings[121]
  • Activate the dissolution of cellulose in different solvents
  • Regenerated cellulose products, such as fibers films, cellulose derivatives
  • Tobacco filter additive
  • Organometallic modified nanocellulose in battery separators
  • Reinforcement of conductive materials
  • Loud-speaker membranes
  • High-flux membranes
  • Computer components[47][122]
  • Capacitors[118]
  • Lightweight body armour and ballistic glass[47]
  • Corrosion inhibitors[123][124]
  • Radio lenses [125]
[edit]

Nanochitin is similar in its nanostructure to cellulose nanocrystals but extracted from chitin.

See also

[edit]

References

[edit]
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