Theses and Dissertations from UMD
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New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
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Item Functionalized Thin-Film Shape Memory Alloys for Novel MEMS Applications(2023) Curtis , Sabrina M.; Takeuchi, Ichiro; Quandt, Eckhard; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Nickel-titanium (NiTi) shape memory alloy (SMA) films are already implemented into microelectromechanical system (MEMS) devices such as sensors, actuators, and implantable medical devices. In this thesis, I used DC magnetron sputter deposition to study the influence of film composition, microstructure, and annealing conditions on the stability of the phase transformation for the NiTi-based SMA thin films TiNiCu, TiNiCuCo, and TiNiHf. SMAs are a type of smart material that can undergo stress or temperature-induced solid-to-solid phase transformation between two different crystalline phases. In NiTi-based SMAs, the two phases are known as martensite with a monoclinic crystalline structure and austenite with a cubic crystal structure. The temperature-induced phase transformations can be used to switch between the martensite and austenite phases, and thus switch between two sets of material properties in the SMA. For example, in NiTi-based SMAs the Young’s modulus, electrical resistivity, and coefficient of thermal expansion of the austenite phase are typically 2X larger than that of the martensite phase. The transformation temperatures, recovery strains, enthalpy of transformation, and fatigue properties of NiTi SMAs can be tuned by alloying NiTi with other elements like copper (Cu), cobalt (Co), and hafnium (Hf). For example, certain compositions of sputtered TiNiCu and TiNiCuCo are known to be ultra-low fatigue SMAs, able to reversibly undergo the phase transformation for 10+ million cycles without degradation in the mechanical or thermal properties. The primary focus of this thesis was the integration of these sputtered NiTi-based SMA thin-films into the following four novel MEMS devices: 1) TiNiCu for magneoelectric sensors, 2) TiNiHf for bistable actuators, 3) TiNiCuCo for stretchable electronics and 4) thin-film SMA stretchable auxetic structures for wearable and implantable medical devices. The shape memory effect was observed in TiNiCu and TiNiHf films when the film thickness and lateral dimensions are downscaled to micro and nano dimensions. In the research publication “Integration of AlN piezoelectric thin films on ultralow fatigue TiNiCu shape memory alloys.”, I showed the reproducibility of the thermal-induced phase transformation of Ti50Ni35Cu15 is attractive for integration into MEMS devices that require a high cycle lifetime. I showed how the SMA’s phase transformation can be used to tune the resonant of bending cantilever-type sensors like magnetoelectric sensors. I also demonstrated excellent thin-film piezoelectric and shape memory alloy properties for 2 μm AlN/ 5 μm TiNiCu films composites deposited onto silicon substrates. The large work densities and high strength-to-weight ratio offered by SMAs are attractive for the development of micro and nano actuators. The thermal induced phase transformation between martensite and austenite is also used to develop bi-directional micro-actuators with TiNiHf/Si and TiNiHf/SiO2/Si composites. In another research publication, “TiNiHf/SiO2/Si shape memory film composites for bi-directional micro actuation”, I demonstrated the influence of film thickness and substrate on the phase transformation properties of TiNiHf thin-films. Ti40.4Ni48Hf11.6 films with thicknesses as low as 220 nm on SiO2/Si substrates can undergo the phase transformation with high transformation temperatures (As > 100 °C) and a wide thermal hysteresis (ΔT > 50 °C). In this publication, we explain how the wide hysteresis and high transformation temperature obtained in TiNiHf films can be used to develop micro and nano-scale bistable actuators based on PMMA/TiNiHf/Si composites. Even though thin-film NiTi-based SMAs are known to reversibly recover superelastic strains of up to 8%, surprisingly, they have not yet been exploited in the growing field of stretchable electronics. In the technical article “Thin-Film Superelastic Alloys for Stretchable Electronics” I demonstrate the first experimental and numerical studies of freestanding thin-film superelastic TiNiCuCo structured into a serpentine geometry for use as stretchable electrical interconnects. Fabricated electropolished serpentine structures were demonstrated to have low fatigue after cycling external strains between 30% - 50% for 100,000 cycles. The electrical resistivity of the austenite phase of a Ti53.3Ni30.9Cu12.9Co2.9 thin-film at room temperature was measured to be 5.43 × 10-7 Ω m, which is larger than reported measurements for copper thin-films (1.87 × 10-8 Ω m). Expanding upon this work, in the conference proceedings paper “Auxetic Superelastic TiNiCuCo Sputtered Thin-Films for Stretchable Electronics”, I present a new platform for functionalized wearable electronics and implantable medical devices based on superelastic thin-film SMA substrates structured into novel stretchable auxetic geometries. Since thin-film SMAs are conductive, the structured substrate itself could serve as the current collector for such stretchable and flexible devices, or a more conductive electrode can be deposited on top of the stretchable auxetic SMA substrate. Overall, the results discussed in this doctoral thesis look to the future of harnessing the functional properties of thin-film sputtered SMAs for novel uses in next-generation MEMS devices.Item INTEGRATED MICROSYSTEM-BASED APPROACH FOR DETECTION AND TREATMENT OF BACTERIAL BIOFILMS ON URINARY CATHETERS(2020) Huiszoon, Ryan Cornelis; Ghodssi, Reza; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Biofilms are a ubiquitous mode of growth for bacteria and present a significant challenge in healthcare due to their resistant nature towards traditional antibiotic therapy. Particularly, biofilms can form on indwelling urinary catheters, leading to catheter-associated urinary tract infections, which are one of the most prevalent healthcare-acquired infections. In recent years, microsystems-based approaches have been developed to measure and study bacterial biofilms. In this dissertation, microsystems are adapted for the catheterized urinary tract environment to address biofilm infections in situ. Specifically, a proof-of-concept device comprised of gold interdigitated electrodes on a flexible polyimide substrate is fabricated and characterized in vitro. This substrate allows the device to conform seamlessly with the cylindrical surface of a catheter. Real-time impedance sensing is demonstrated, showing an average decrease in impedance of 30.3% following 24 hours of biofilm growth. The device also applies the bioelectric effect, which yields an increase in impedance of 12% and the lowest biomass relative to control treatments. Furthermore, 3D-printed molds and commercial modeling software show that the cylindrical conformation does not have an appreciable impact on performance. This device is integrated with a commercially available Foley catheter using two disparate approaches: (1) integration of the flexible proof-of-concept device using a 3D-printed catheter insert and (2) electroless plating directly onto the catheter lumen. In addition to electrode integration, miniaturized electronic systems are developed to control sensing and treatment wirelessly with a minimal form factor. A smartphone mobile application is developed in conjunction with this effort, to provide a user-friendly interface for the system. Several functions are verified with the integrated system, including biofilm sensing, wireless signal transmission, bladder drainage, and balloon inflation. To decrease the risk associated with this system for future research in vivo and in a clinical setting, sensing and treatment are evaluated under realistic conditions. The biochemical aspect of the catheterized environment is recreated using artificial urine, and the physical aspect is recreated using a silicone model of a human bladder and a programmable pump. A 13.0% decrease in impedance is associated with bacterial growth; this decreased magnitude relative to the proof-of-concept device is due to the reduced degree of growth in artificial urine. The bioelectric effect is demonstrated as well, showing a reduction in planktonic bacteria of 1.50×107 CFU/ml and adhered biomass equivalent to OD590nm = 0.072 relative to untreated samples. This work provides a framework for developing microsystem-based tools for biofilm infection management and research from proof-of-concept to integrated system, particularly for CAUTI. The results demonstrate that the cylindrical conformation does not interfere with device sensing or treatment performance and that the system maintains functionality under realistic conditions, laying the groundwork for future in vivo and clinical testing. The system will provide in situ and real-time data regarding catheter biofilm colonization in a way that is not possible with existing techniques. Finally, the system can serve to reduce reliance on antibiotics and reduce the spread of antibiotic resistance in CAUTI and other vulnerable areas.Item Indoor Routes and Locations Inference using Smartphone IMU sensors(2020) Zhou, Xinyu; Franklin, Manoj; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In this paper, we devise a framework to infer a smartphone user's location and walking routes in an indoor environment, using only the information from inertial measurement unit (IMU) sensors like gyroscope and accelerometer. To overcome the shortcoming of estimation drift over time in common PDR (pedestrian dead reckoning)-IMU systems, we propose a map-aided system which uses the map elements to help correct the user's position. We generate a map based on the environment parameters and a map matching algorithm is applied to find the most likely location of the user. The reading from the IMU sensors contains amounts of noise when user is walking, therefore we propose an edge detection algorithm based on the PELT model to smooth the piece-wise signals and identify the time frame when the user is making a turn. We evaluate our system when the smartphone is held either in the user's hand or in the backpack, and the system is able to give the correct walking path in both cases.Item Sensor-Augmented Lightning Mitigation; Implications for Risk at Hydraulic Fracturing Storage Facilities(2015) Rooke, Sterling; Skibniewski, Miroslaw J.; Fuhr, Peter L.; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Hydraulic Fracturing (hydro fracking) has revolutionized oil and gas production in the United States. Controversy has been widespread and plenty of uncertainty remains commonplace in the public. The topic of hazardous chemicals and pollution associated with hydro fracking will be presented in some detail. However, the key focus will be on sensors and lightning mitigation at produced hydrocarbon storage batteries. Unmitigated fires and explosions will be shown to cause $10 million per direct strike in some lightning risk zones. Lightning has stood as an unresolved threat to hydrocarbon storage facilities for over 100 years. Literature research has shown that 33% of all modern hydrocarbon tank accidents are due to lightning (Chang and Lin, 2006); in addition, cloud-ground lightning strikes are predicted to increase by 50% this century (Romps et al., 2014). An overlay of the current National Lightning Detection Network (NLDN) risk map and the Energy Information Administration (EIA) shale play map clearly show the lightning threat only increasing with the migration of future shale activities. While planning may change, shale deposits and regional lightning threats are not changing geographically; this research quantifies the threat and outlines clear lightning mitigation strategies. Furthermore, real-time detection and the associated methodology of lightning mitigation have implications for industries far beyond hydro fracking. By leveraging industrial standards for Fire and Gas Systems (FGS) such as IEC 61511, the proposed lightning effects mitigation system has a pathway toward verification and eventual validation at a broad array of industrial sites. Some extended applications included Navy fuel storage depots and Liquefied Natural Gas (LNG) facilities.Item UTILIZING ELECTRONIC NOSE AND GC-MS TO EXAMINE CRITICAL FACTORS INFLUENCING THE FORMATION OF ODOROUS VOC’S IN BIOSOLIDS.(2016) Romero, Adrian; Torrents, Alba; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Despite the efforts to better manage biosolids field application programs, biosolids managers still lack of efficient and reliable tools to apply large quantities of material while avoiding odor complaints. Objectives of this research were to determine the capabilities of an electronic nose in supporting process monitoring of biosolids production and, to compare odor characteristics of biosolids produced through thermal-hydrolysis anaerobic digestion (TH-AD) to those of alkaline stabilization in the plant, under storage and in the field. A method to quantify key odorants was developed and full scale sampling and laboratory simulations were performed. The portable electronic nose (PEN3) was tested for its capabilities of distinguishing alkali dosages in the biosolids production process. Frequency of recognition of unknown samples was tested achieving highest accuracy of 81.1%. This work exposed the need for a different and more sensitive electronic nose to assure its applicability at full scale for this process. GC-MS results were consistent with those reported in literature and helped to elucidate the behavior of the pattern recognition of the PEN3. Odor characterization of TH-AD and alkaline stabilized biosolids was achieved using olfactometry measurements and GC-MS. Dilution-to-threshold of TH-AD biosolids increased under storage conditions but no correlation was found with the target compounds. The presence of furan and three methylated homologues in TH-AD biosolids was reported for the first time proposing that these compounds are produced during thermal hydrolysis process however, additional research is needed to fully describe the formation of these compounds and the increase in odors. Alkaline stabilized biosolids reported similar odor concentration but did not increase and the ‘fishy’ odor from trimethylamine emissions resulted in more offensive and unpleasant odors when compared to TH-AD. Alkaline stabilized biosolids showed a spike in sulfur and trimethylamine after 3 days of field application when the alkali addition was not sufficient to meet regulatory standards. Concentrations of target compounds from field application of TH-AD biosolids gradually decreased to below the odor threshold after 3 days. This work increased the scientific understanding on odor characteristics and behavior of two types of biosolids and on the application of electronic noses to the environmental engineering field.Item Low Noise Pre-amplifier/Amplifier Chain for High Capacitance Sensors(2007-08-03) Adl, Sanaz; Peckerar, Martin; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In the past two decades, imaging sensors and detectors have developed tremendously. This technology has found its way into a number of areas, such as space missions, synchrotron light sources, and medical imaging. Nowadays, detectors and custom ICs are routine in high-energy physics applications. Electronic readout circuits have become a key part of every modern detector system. Many sensing circuits in detectors depend upon accumulating charge on a capacitor. The charge uncertainty on the capacitor when it is reset causes a signal error known as reset noise. Therefore, low noise readout circuitry capable of driving high input capacitance is essential for detector systems. A low noise pre-amplifier/amplifier readout circuitry has been designed and fabricated in 0.13um IBM CMOS8RF process technology. The pre-amplifier/ amplifier chain employs correlated double sampling at the input to suppress the kTC noise without any additional circuitry. In order to increase the signal-to-noise ratio, capacitive matching is used at the amplifier input. The experimental results of the signal processing chain employing capacitive matching and correlated double sampling show more than 60 times improvement in the signal-to-noise ratio over the same circuit without these improvements. In this dissertation a novel auto-zeroing technique is introduced as well. This technique uses a nulling point other than the amplifier's input and output to perform the auto-zeroing operation. The auto-zeroing is performed by taking advantage of emitter degeneration in the input transistor pair of the differential pair. For testing purposes this technique is implemented on a telescopic cascode differential amplifier. The auto-zeroed telescopic cascode differential amplifier has also been designed and fabricated in 0.13um IBM CMOS8RF process technology. This auto-zeroing technique reduces the input referred offset noise by an order of magnitude.