Left ventricular assist devices (LVADs) are an increasingly utilized therapy for end-stage heart failure. Thrombosis within the graft from the pump to the aorta has been documented, but is poorly researched. This study examines the effect of graft geometry, as measured by radius of curvature, bend angle, and diameter, on thrombogenic flow patterns within the graft for a range of flow conditions. It also examines the effect blood properties, including viscosity and density, on these flow patterns. The results indicated that radius of curvature had a powerful effect on thrombogenic flow patterns. Flowrate and bend angle were also influential. The results of this study offer insight on how graft geometry may interact with flow conditions and blood properties to produce regions of stagnation or recirculation within the outflow graft, which may precipitate thrombogenesis and pose a risk to patients.

Despite significant preventative efforts, falls continue to be a major source of morbidity and mortality among the elderly. Additionally, the fear of falling can be a major obstacle to independent living for otherwise self-sufficient individuals. This fear is significantly heightened in individuals who have sustained a fall and often results in self-imposed restrictions on mobility and exercise, causing weakening in these individuals and further exacerbating the danger. Much time has been spent developing alert systems in an attempt to mitigate these problems. Unfortunately these systems typically involve dedicated monitoring centers and therefore often come with substantial upfront and recurring costs. This thesis proposes a solution to these problems by implementing fall detection and alert capabilities on a smartphone, devices that are quickly becoming ubiquitous in today’s society. This solution has the potential to quell the fears of many elderly people and their families, while allowing them to maintain their independence at little expense. Detailed herein is the process of designing, developing, and validating this fall detection application. The final application was written in Objective-C for iOS and tested on an iPhone.

Chronic dehydration is an endemic problem for many population groups. Current methods of monitoring hydration status are invasive, time consuming, cannot be performed while exercising, and require lab resources. A proposed solution is a wearable, continuous, and non-invasive device that uses harm-free ultrasonic pulses to detect changes in tissue hydration status over time. Customer and engineering requirements were defined and used to guide the design process. Literature reviews were performed to identify essential information on dehydration, assess current methods, discover state of the art devices, and describe ultrasonic theory. Market research was performed to identify athletes as the target population group. An adjustable elastic nylon bicep band prototype was manufactured and the integration of more advanced components was proposed. The theoretical signal processing method used to detect hydration status was validated through initial tests with a prototype electrical system composed of a Teensy 3.1 board, two 18 kHz piezoceramic disc elements, and an Arduino/LabVIEW interface. Tests with aluminum, rubber, and sponge materials were performed to compare the signal response to propagation through materials with different acoustic properties and water contents. Finally, tests performed with dehydrated bovine muscle tissue revealed a statistically significant difference between hydrated and dehydrated tissue, a promising indication for future device refinement.

Recent advances in the complexity of in vitro biological systems have enabled new possibilities for "Organ-on-a-Chip" systems with greater physiological relevancy. Microphysiological Systems (MPS) represent one such advance which incorporates a sophisticated biological construct with a custom designed biological sensor. As the world grapples with grand challenges such as the Opioid Crisis, novel neural MPS offer a means to address both the safety and efficacy of alternative therapeutics, while potentially accelerating the bench-to-market timeframe for lifesaving addiction treatments. Investigations into custom microfabrication processes for such in vitro combinatorial biosensors are thus warranted. This Dissertation addresses the development of a 3D microelectrode array (MEA) biosensor, designed for integration with a custom peripheral-central nervous system, nociceptive circuit. For such Biological MicroElectroMechanical Systems (BioMEMS) sensors, the dielectric layer is crucial as an insulator and part of the cellular microenvironment. Nanoporous silicon dioxide (SiO2) represents an excellent material for this application, however, can be difficult to incorporate on polymer-based BioMEMS platforms. After development of the baseline 3D MEA platform that can integrate several sensing modalities on a single chip, the work presented in this Dissertation further establishes a novel polydopamine (PDA) mediated chemistry for nanoporous SiO2 / Polyethylene Glycol / Matrigel microenvironment definition. Dorsal Root Ganglion (DRG)/nociceptor and Dorsal Horn (DH) neural spheroids were then matured atop this 3D MEA platform, and spontaneous / evoked compound action potentials (CAPs) were successfully recorded during and at the 6-month timepoints. Lastly, inhibitory drug trials enabled confirmation of multi-part biological activity, indicative of the neural coculture that enables a novel 3D MEA-integrated neural 3D MPS, demonstrated for the first time to our knowledge, for long-term electrophysiological applications.

Despite advancements in device design and anti-coagulation treatments, there are numerous adverse events that may occur following implantation of LVADs. The most devastating involves the embolization of thrombus into the brain causing a stroke, with incidence of up to 14-47% over a 6–12-month period. This study aims to elucidate ways to reduce this risk by surgical maneuvers guided by a multi-scale computational fluid dynamics analysis wrapped around a multi-objective shape optimization scheme which optimizes the anastomosis location of the VAD outflow graft (OG) along the ascending aorta to minimize the incidence of thrombi reaching the cerebral vessels and reduce particle residence times. The computational model comprises of two coupled parts: a 50 degree of freedom 0-D lumped parameter model of the peripheral circulation that is loosely-coupled to a 3-D CFD model of the aortic circulation. Blood flow is modeled as laminar, incompressible and the non-Newtonian blood rheology is accounted for by the Carreau-Yasuda model. A Lagrangian particle tracking scheme is used to model thrombi as non-interacting particles. The results verify the hypothesis that a surgical maneuver that tailors the LVAD-OG anastomosis configuration can minimize the incidence of cerebral embolization. This is exemplified most in the case that considered particle release from the OG, as a fivefold decrease in cerebral embolization resulted from optimizing the implantation configuration. It was found that shallow orientations are most optimal in minimizing the cerebral embolization in the case where particles originate from the aortic root walls and the ventricle. In the last case, where particles were released from all three origins, the optimal implantations show a proclivity for intermediate implementations that direct the momentum of the VAD-jet towards the lumen of the aortic arch. Discrete coefficient of restitution sensitivity analysis reveals a negligible effect on cerebral embolization incidence as particle-wall collisions become less elastic.

Development of an Open Source Prosthetic Hand Platform Scott Garrett In the field of upper extremity prosthetic devices, advancements in technology drive the design of products which are becoming capable of restoring the lost functions of the native hand. While several dexterous devices have been developed to serve this purpose, they remain prohibitively expensive and thus are not a viable option for many upper extremity amputees. To address this problem a prosthetic hand platform was developed utilizing the open source Arduino microcontroller and off-the-shelf electrical components. Using these resources, a novel finger actuation mechanism was developed to show how a prosthetic hand platform could be developed which is capable of individual finger actuation, multiple actuation modes, sensing of forces at the individual fingers, providing force feedback to the user, and control of finger actuation through a variety of control inputs. After going through several iterations of hand’s mechanical components, electronics, and firmware a final prototype was built to showcase the possible capabilities of the open source prosthetic hand platform. This prototype consisted of several groups of subcomponents including an auto-flexing / extending finger design, a modular palm/ servo attachment base, and a wrist section which housed the hand’s electronic components, power supplies, force feedback system. The open source prosthetic hand platform was then verified using a series of tests to quantify several performance characteristics of the final prototype. Battery life and grip strength during continuous use were evaluated and demonstrated that the hand could provide consistent grip force during up two hours of initial continuous use. Also, the grip performance of the hand was assessed through the grasping of spherical objects with varying surface textures, diameter, and weight. Furthermore the hand was tested in various “real life” applications including manipulating and sorting small objects, opening doors, grasping moderately heavy objects such as water bottles, and sensitive objects such as an egg. Lastly, the platform was connected to a myoelectric input circuit to demonstrate compatibility with advanced electro-physical inputs. These tests demonstrated that the platform was capable of performing some of the dexterous tasks performed by prohibitively expensive available robotic upper extremity prosthetic devices. Further developments could be made to the open source prosthetic hand platform including enhancements to the platform’s finger force sensing and feedback mechanisms, consolidation of the electronics, refinement of the auto-flexing / extending fingers, and integration with a silicone covering and patients residual limb socket. These future iterations of this platform could help provide a dexterous prosthetic hand platform at lower cost to a wider patient base.

Measuring the in vivo load state of Total Knee Arthroplasty (TKA) components is required to understand the structural environment and wear characteristics of the devices. The ability to acquire this information gives tremendous insight into the mechanics of the joint replacement prosthesis. Data corresponding to normal loads, in-plane loads, shear loads, load center, contact area, and the rate of loading is needed to fully understand the kinematics and kinetics of the orthopedic implant. In this research, a novel sensing system has been developed which is capable of fully characterizing three-dimensional strain and stress at a single location. Capacitance-based sensors were chosen to avoid the power loss and drift characteristics typical of resistive elements due to resistive heating effects. A design and optimization methodology has been developed by combining conformal mapping electrostatic analysis techniques with methods from micromechanics of composite materials. Results of the design and optimization technique are used to understand the behavior of the sensing system. Simulation of these systems was performed using multiphysics finite element analysis, and novel methods for fabricating the sensors were adapted from techniques for fabricating microelectromechanical systems (MEMS) using biocompatible materials. An array of six sensors was fabricated with a critical dimension of 2.25 micrometers. This array consisted of a parallel plate capacitor for measuring normal strain, two differential elements for sensing shear strain normal to the plane of the array, and three interdigitated transducer (IDT) elements for characterizing strain in the plane of the sensor. The normal strain sensor exhibited a sensitivity of 1.54×10-3 picofarads per megapascal, and the shear sensor had a sensitivity of 4.77×10-5 picofarads per megapascal. Testing results showed that all sensors had linear response to loading and insignificant drift. Multiaxial testing results illustrated the ability of the differential sensors to determine loading direction. A multiaxial, MEMS sensor array has been developed for use in orthopedic, load-measuring conditions. This system has been optimized for use in soft materials such as ultra-high molecular weight polyethylene (UHMWPE). In the future, arrays of sensors will be embedded in orthopedic components to determine the total state of stress at local positions within the component.

Specific objectives of this study were to develop, prototype, and test a corn population sensor. Both intrusive mechanical and non-intrusive capacitive techniques have been used to develop the stalk population sensors in previous research. However, neither could generate consistent performance. The mechanical method required high maintenance and resulted in significant underestimations of stalk counts. The performance of capacitive systems was limited by inadequate sensing distance, especially at low stalk moisture levels. In this research, the sensitivity of the capacitive sensor was optimized for corn stalks. This system utilized a single-sided capacitive sensor, Wien bridge oscillator, phase-locked loop, and an operational amplifier to transform stalk presence to a change in electrical potential signal. The capacitive sensor patterns were simulated using the finite element method, which provided useful conceptual information. A number of different detection element patterns were modeled and tested. The patterns examined included single-sided two-plate, interdigital, polarized interdigital, semi-interdigital, and solid ground electrode. The key parameters affecting pattern sensitivity were investigated. The most promising pattern, the solid ground electrode, was selected for further evaluation and development. The solid ground electrode detection element was incorporated into circuitry including Wien-Bridge oscillator, a phase-locked loop used as a high-speed frequency-tovoltage converter, and an operational amplifier to provide impedance matching and maximize data acquisition resolution. The operational configuration, optimum operating parameters, and associated component sizes were determined using both modeling and laboratory testing. With an acceptable signal-sided pattern and signal-to-noise ratio, this sensing system was investigated in a realistic production environment. A preliminary field test was used to evaluate the sensor system (including a protective housing and mounting system) and data acquisition system to identify problems before conducting the final field test. Stalk moisture content and harvest speed were used as treatment blocks in the final test. The influences of environmental and mechanical noise and the noise-like influence of corn leaves and weeds were also investigated. The final field test accurately simulated realistic harvesting conditions and real-time data was collected for stalk identification analysis. Post-acquisition processing, feature extraction, and principal component analysis of the extracted features were performed on the raw field data. Three sensor signal features were selected to identify stalks. A backpropagation artificial neural network technique was used to develop the pattern classification model. Numerous neural network structures were evaluated and two-layer structure with four neurons in the first layer and one neuron in the second layer was selected based on maximum prediction precision and accuracy and minimum structure complexity. This structure was then evaluated to determine the prediction accuracy at various resolution levels. Results showed that the model can predict stalk population at 99.5% accuracy when the spatial resolution is 0.025 ha. The sensor can predict stalk population with a 95% accuracy when the resolution is a 9-meter row segment (approximately 10 seconds).

In this thesis, a prototype ECG monitor was developed that is integrated into an elastic shirt and takes a 3-lead ECG for over 5 days. The high-quality measurements can be used to identify markers indicative of various detrimental heart conditions. Measurements recorded by the device are encrypted and stored onto a micro-SD card. Current Holter monitors are expensive and have functional lives less than 48 hours; however, extended duration monitoring has been proven more useful in diagnosis. The device designed demonstrates that ECG measurements can be taken over longer durations without sacrificing quality, comfort, or device cost.

When people go to a mall, museums, or other such locations they tend to rely on maps to find their way around. However, for people who are blind or visually impaired (BVI) maps are not easily accessible and they depend on other means, such as a guide, to get around. Research has only just begun to investigate providing maps for people who are BVI on touch screen devices. Many different types of feedback have been used: audio (sound), tactile (touch), audio-tactile, and multitouch. Some research has been conducted on the benefit of using multiple fingers (multitouch) and has found conflicting results. Yet, no known research has been conducted on the comparison of using audio feedback to that of tactile feedback. In this study, we look to try and answer two questions. 1.) Is audio equal to or better than tactile? As well as: 2.) Does multiple fingers help? Participants were asked to use seven different methods (4 audio, 3 tactile) to explore an overview map and an individual map and answer questions about them. Results showed that overall, audio cues are similar or better than tactile cues which is beneficial since it requires less battery to generate audio cues than tactile cues. It was also shown that the use of multiple fingers was more beneficial in tasks that are spatially demanding. While those who have tactile experience benefited when using two fingers with each finger represented by a different instrument played to separated ears.