Luminal esophageal temperature monitoring is of high importance during catheter-based ablation procedures in the left atrium of the heart. An electrophysiologist’s ability to reliably monitor significant temperature increase created by local ablative heat transfer is crucial to preventing thermal injury of the esophagus. The work presented here describes the initial development of a device intended to accurately measure temperature of the inner esophageal wall during treatment for atrial fibrillation. An experimental setup has been developed using porcine esophageal and left atrial tissue and tests have been performed to better understand heat flow through the biomaterials in contact. To compliment ex vivo experiments, a numerical study using thermal finite element analysis has been implemented to investigate the temperature distribution across tissue layers as a function of tissue thickness, as well as heat source application time. Both the ex vivo study and finite element simulations aid in development of a practical prototype device for potential use during catheter ablation.

To achieve an areal density of 1 terabits per square inch (1.55 gigabits/mm2) in hard disk drives, the size of magnetic grains in hard disks has been reduced to approximately 7 nm and the spacing between the magnetic head and the disk has been minimized to 1 to 2 nm. At a spacing on the order of 1 to 2 nm between the head and the disk, it is likely that contacts between the magnetic head and the disk occur during reading and writing, causing erasure of data or even failure of the head/disk interface. Wear particles can be generated as a consequence of contacts between slider and disk, and if particles enter the head/disk interface, catastrophic failure of the head/disk interface can occur. To reduce the generation of wear particles and avoid failure of the head/disk interface, it is important to investigate how the tribological performance of all contact interfaces in hard disk drives can be improved.

In this dissertation, the tribological performance of the most important contact interfaces in a hard disk drive are investigated with a focus on the generation of wear particles and lubricant migration. First, fretting wear is investigated to study the effect of a diamond-like carbon (DLC) overcoat on wear of the dimple/gimbal interface. A numerical simulation model based on finite element analysis was developed to explain the experimental results. Then, lubricant migration on the air bearing surface and its effect on the head medium spacing (HMS) was investigated as a function of temperature, slider position, and “parking time” of the slider on the ramp. Thereafter, the thermal response of a thermal sensor during contact with asperities on the disk surface was analyzed. The effects of experimental and environmental conditions on the resistance change of the sensor were studied. Finally, experimental and numerical investigations were performed to analyze contact between the suspension lift tab and the ramp in hard disk drives. The voice coil motor current was used to characterize the change of the friction force and the generation of wear debris at the lift tab/ramp interface during load/unload testing. Numerical simulations were performed to analyze how to reduce contact stress between the lift-tab and the ramp.

The results of this dissertation will be helpful in improving the tribological performance of hard disk drives.

Glaucoma is a neurodegenerative disease that affects 65 million people worldwide, causing progressive optic nerve damage over time and irreversible blindness. Elevated intraocular pressure (IOP) in the eye has been considered one of the leading modifiable risk factors of the disease. Standard care relies on indirect eye pressure measurements in a physician’s office as one metric to determine therapeutic treatments. Such infrequent single-point measurements are inadequate to fully represent and characterize the patterns associated with disease. In this dissertation we investigate and develop a novel optical-based pressure sensing system capable of measuring IOP on a frequent or semi-continuous basis.

First, the IOP sensor design requirements were established with the aim of measuring pressure using a passive approach with high sensitivity and repeatability. By using the principle of interferometry and diaphragm deflection, the changes in intraocular pressure were determined through interferometric fringes and maximum diaphragm deflection. Next, studies were conducted to investigate the effects of temperature, incident angle, and substrate coating in order to characterize the behavior of the sensor. In addition, a handheld reader was developed to wirelessly obtain optical information from the sensor. Three generations of handheld readers were developed to enable measurements from live and awake rabbits once the sensor was implanted in vivo. The IOP sensor was evaluated ex vivo using rabbits in order to determine the optimal implant method and anchoring approach. Cataract surgery was performed ex vivo in rabbit eyes to replace the native lens with a modified intraocular lens (IOL) carrying the IOP sensor. Finally, the sensor was further valuated through in vivo studies using New Zealand white rabbits. Cataract surgery was performed on the rabbits to implant the sensor. The study showed that IOP measurements were obtainable in vivo. The presence of the sensor had no observable impact on the rabbits’ inflammatory response, suggesting that the system is biocompatible.

Throughout the study, various image processing algorithms were developed in MATLAB to analyze fringe images by employing mathematical models and built-in image analysis functions.

Catheter associated urinary tract infection (CAUTI) is a significant problem. Interdisciplinary teams have coordinated to address this problem, yet there is still a need for an adequate solution. Indwelling urinary catheters are at the root of prevalence of CAUTI. Urinary catheters with surfaces that are defenseless against the growth of infectious microorganisms, such as bacteria, are a risk to patients with urinary incontinence. This Master’s thesis describes the design and investigation of a passive electricidal urinary catheter surface. This entails a discussion of methods to prevent CAUTI with catheter coatings, in addition to methods used to formulate and adhere coatings. The design of composite coatings using polydimethyl siloxane (PDMS), with active materials zinc, silver, and/or silver oxide powders is disclosed, thereafter. These coatings are designed so that the active materials are well adhered and allowed to react in the presence of bodily fluids. The oxidation reduction reactions that occur between the dissimilar metals in solution has the capability to create an environment at the catheter surface that includes electric fields, microcurrents, changes in pH, and generation of heavy metal ions and hydrogen peroxide. This environment is similar to that of a zinc-silver galvanic cell, and has been found to alter the adhesion and proliferation of bacteria on surfaces and their ability to form dangerous biofilms. The composite coatings made in the lab were tested to determine their reactivity and biocidal effects. Methods used to quantify the generation of hydrogen peroxide, electric potentials, changes in pH, and inhibition of planktonic bacteria and biofilm in synthetic urine are discussed. The results of these tests show that the coatings are able to generate potentials and hydrogen peroxide in synthetic urine. Coatings containing combinations of zinc and silver oxide or silver and silver oxide have the greatest antimicrobial effects compared to controls. These coatings also inhibited biofilm as good as, if not better than, commercially available antimicrobial specimens.