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.

Today, glaucoma is the leading cause of irreversible blindness in the world. Its highest risk factor is related to an elevated intraocular pressure (IOP) within the eye that can cause stress on the optic nerve and deteriorate the visual field in patients. Regular IOP monitoring can be crucial in detecting early onset of glaucoma, especially since surgical cures might not exist in the later stages. To improve the prospect of self-examining ophthalmic devices, we have developed a handheld 3-in-1 device consisting of 3 commonly used glaucoma screening instruments. This includes a compact slit lamp biomicroscope, visual acuity tester, and a non-contact tonometer. The aim of this device is to enable easy self-examination of the eye more frequently, especially for patients physically unable to travel to in-person clinic appointments to perform them.

To validate the tonometer measurement principle, this thesis investigates the development of an artificial cornea using silicone materials to study corneal deflection as a function of the IOP. Samples were fabricated using 2-part 3D-printed molds that accurately capture the geometry of the human cornea. Young’s moduli for a range of selected silicones were evaluated and compared with that of human cornea as well. Eye pressure was simulated using a water-filled manometer channel and readings were obtained from both a commercial and the 3-in-1 device’s tonometer to test the designed artificial corneas. Results from both devices validate the use of such a phantom eye apparatus to test similar ophthalmic instrumentation before clinical testing on humans.

Cardiac ablation is a common procedure performed by cardiac electrophysiologists. The clinician will use a device, such as a radiofrequency ablation catheter, to thermally ablate or burn off defective heart tissue (myocardium). During the procedure, the esophagus can be in close proximity to the heart tissue. As heat transfers through the myocardium, it can also transfer to the esophagus, potentially damaging the esophagus tissue. The damage results in thermal lesions and, in worst-case scenarios, atrioesophageal fistulae. The work reported in this thesis was performed to devise a tool and method to protect the esophagus during the ablation procedure. The Esophageal Deflection Device (EDD) was designed and manufactured to move the esophagus away from the ablation location. The device comprises of a straight rod and a precurved overtube. If the rod is inserted into the overtube, the overtube is straightened out by the rod. If the assembled device is inserted into the esophagus, and the rod is retracted, the elastic memory effect will cause the tube to reassume its original curved shape, thereby moving the esophagus safely away from its close position to the heart. In this dissertation, the medical problem along with the design tools needed to address the above problem of moving the esophagus are investigated. The materials used for the Esophageal Deflection Device are reviewed, and the testing of 3D printed hyperelastic photopolymers used during preliminary designs is performed. Theoretical, experimental, and numerical methods were used to characterize the bending behavior of the Esophageal Deflection Device, and the Mooney-Rivlin materials properties for the hyperelastic tube material are determined. Thereafter, a temperature sensing Esophageal Deflection Device is described and tested. The temperature distribution during ablation is simulated using finite element analysis. Experimental and numerical results are discussed and compared. Finally, a summary and future direction of this work and our research is provided.

Recent advances in cutting-edge computer-assisted surgical navigation systems resolve thecritical need for safer and more efficient surgical procedures. State-of-the-art navigation systems incorporate invasive retro-reflective markers that can be detected with the help of infrared cameras, providing real-time guidance to clinicians about patient anatomy and instrument trajectory. While these systems have revolutionized computer assisted surgeries, the cost ranges from $250,000 to 500,000, making it prohibitively expensive for small healthcare centers. Optical tracking, an alternative to infrared tracking, is explored in this paper. It relies on visible light to be able to track specific objects or markers. Using two low-cost web cameras, a stereoscopic camera was calibrated and programmed to detect the 3D position of moving fiducial ArUco markers, non-invasive tags that store positional information. First, using a positioning platform, the markers were moved in the X and Y directions with the objective of tracking minor movements of patients during surgery. Next, a marker attached to a surgical needle was moved in 5DOF using the Arduino Tinkerkit Braccio Robotic Arm to mimic the handling of surgical instruments. Movements were recorded and the videos were processed in 3 color spaces, red- green-blue (RGB), hue-saturation-lightness (HSL) and hue-saturation-value (HSV) on OpenCV to calculate the tracking accuracy of the cameras. On the positioning platform, differently colored markers (white, pink, orange and yellow) were tested for the highest accuracy of detection. Using various post-processing techniques, it was found that an accuracy of 5.5 mm could be achieved in the RGB color space using a white colored marker. When the marker was moved using the robot, it was possible to obtain 2.27 mm accuracy in the RGB color space with a white colored marker.

To achieve an areal density of 1 terabit per square inch (1 Tb/in2) in hard disk drives, the mechanical spacing between the flying slider and the rotating disk has decreased to approximately 1 nm. With this decrease in spacing, the head-disk interface has become increasingly more susceptible to slider-disk contacts, wear, and lubricant transfer from the disk to the slider. Contamination at the head-disk interface can cause “flying stiction”, flying instability, and read/write errors, leading ultimately to failure of the disk drive. It is essential to understand perfluoropolyether lubricant transfer and hydrocarbon contamination at the head-disk interface to improve the tribological performance and the reliability of hard disk drives.

In this dissertation, perfluoropolyether lubricant transfer and lubricant fragmentation at the head-disk interface are investigated numerically as a function of temperature, local pressure change, and disk velocity. Molecular dynamics is used to study the effect of laser pulse peak power, pulse duration, and repetition rate on lubricant depletion. Hydrocarbon contamination at the head-disk interface is modeled experimentally by assuming a three-step mechanism for hydrocarbon contamination, consisting of evaporation, transfer, and condensation. In addition, a numerical investigation of hydrocarbon contamination at the head-disk interface is performed using molecular dynamics simulations.

The results of this dissertation provide guidance in the design of perfluoropolyether and hydrocarbon lubricants to improve the tribological performance and reliability of the head-disk interface in hard disk drives.

A common and serious complication of radiation treatment for cervical cancer is vaginal stenosis, defined as the narrowing or shortening of the vaginal canal. Prior studies have found that vaginal dilators can be an effective early treatment for vaginal stenosis but suffer from low patient adherence due to pain and discomfort. Inflatable silicone balloon dilators have recently been designed and implemented in the Talke lab to address low patient adherence of traditional dilators. By taking advantage of the high flexibility of silicone and the continuously adjustable size of an inflatable balloon, the new dilator design reduces pain and discomfort for the patient.

To simulate a stenosed vaginal canal and evaluate the efficacy of the inflatable dilator, we have built a vaginal model using a specially designed composite material consisting of silicone and thermoplastic polyurethane. This material can create a vaginal phantom with stiffness variation. The two-material composite allows us to tune the stiffness of our vaginal tissue analog, a critical symptom of vaginal stenosis.

This thesis investigates this newly designed composite material of silicone and thermoplastic polyurethane to help in the understanding of the treatment of vaginal stenosis. Investigating how stenosed vaginal tissue reacts to an inflatable dilator will be a guide to clinical applications and the assessment of vaginal stenosis. Tensile coupons were manufactured and tested with a uniaxial tensile tester and a digital image correlation setup. The constitutive equations for the silicone-polyurethane composite were determined and analyzed in terms of Mooney-Rivlin coefficients for hyperelastic materials.

Back pain is one of the leading causes of disability in the world. Interventional pain management therapies often include epidural steroid injections or radiofrequency ablations to alleviate back pain. However, current techniques use fluoroscopy, which exposes both the patient and physician to radiation and require an experienced physician to accurately translate the 2D x-ray images to a 3D mental image. An augmented reality navigation system is proposed as a solution to eliminate radiation exposure and offer a low-cost method to overlay a 3D MRI model of the patient’s anatomy on top of the patient to increase the speed and safety of spinal surgical procedures. Non-invasive skin markers with ArUco codes will be used to register the MRI model on top of the patient’s body during the procedure. Experiments involving an XYZ platform were run to determine the tracking accuracy of the ArUco codes and which variables potentially present in an operating room could affect that tracking accuracy. It was determined that the ArUco codes had submillimeter error, thus showing their feasibility in pain management navigation systems.