Master of Sciences, Case Western Reserve University, 2018, EECS - Electrical Engineering

Control of doping levels during chemical vapor deposition (CVD) growth has propelled diamond to the forefront of high frequency switching devices and emergent quantum applications. This thesis presents a robust exploration of hot- filament CVD growth of a 6 µm thick polycrystalline diamond, nitrogen-vacancy (NV) center optical characterization, microelectromechanical systems (MEMS) fabrication, and the subsequent resonance analysis. The grown diamond films employed in our study are traditionally used for electrochemical devices, thus being heavily boron doped, and not necessarily optimized for surface roughness or NV defects. We characterize our film via Raman spectroscopy and also compare its photoluminescence results against commercial grade diamond for NV defect signatures. Our film shows more pronounced signatures for the 575 nm and 637 nm zero-phonon lines (ZPL) of the NV0 and NV- centers, respectively

Committee: Philip Feng (Advisor); Christian Zorman (Committee Member); Heidi Martin (Committee Member) Subjects: Chemical Engineering; Condensed Matter Physics; Electrical Engineering; Engineering; Materials Science; Nanoscience; Nanotechnology; Optics; Physics

PhD, University of Cincinnati, 2001, Engineering : Electrical Engineering

The objective of this research is to develop magnetically driven microvalves and micropumps for surface mountable microfluidic systems. Several magnetically actuated new microvalves and pumps have been designed, fabricated and successfully characterized for microfluidic control in this work. Two versions of normally-closed membrane microvalves have been realized: one with a flat membrane and the other with a mesa membrane. Steady-state leakage flow rate of nitrogen gas for the flat membrane was 20 mL/min and for mesa membrane 9.4 mL/min, respectively, at an input pressure of 1.0 psi and 1.1 psi. Both microvalves leaked intrinsically due to stress on the silicone membrane, but the second version leaked less. In addition, a new bi-directional normally-closed ball microvalve using the magnetic actuator has been explored for improving the leakage problem and minimizing dead volume. By using biomedical grade silicone rubber tubing, good sealing has been achieved, and by adding an electromagnet ring or a permanent magnet ring around the outlet position, much better sealing has been attained. However, the microvalve showed that its leakage is still dependent on the operating input pressures. To address the relevant issues to both the leakage and the dead volume, a new compact and reliable pinch microvalve has been designed, assembled, and tested. This pinch microvalve consisted of a solenoid magnetic microactuator with a pinch plunger and a biomedical grade silicone tubing to be pinched. This pinch microvalve has shown excellent characteristics of zero leakage up to 30 psi and zero dead volume, keeping surface mountable capability over the microfluidic motherboards. Furthermore, a new peristaltic micropump has been realized by connecting three pinch microvalves in series. The valve has self-priming and bi-directional pumping capabilities. The maximum pump rate obtained was 1 mL/min at 100 Hz. Back-pressure was 280 cm of water pressure, which corresponded to 4 psi at 20 Hz. (open full item for complete abstract)

Committee: Dr. Chong Ahn (Advisor) Subjects:

PhD, University of Cincinnati, 2005, Engineering : Electrical Engineering

This dissertation describes the development of mini and micro packaging strategies for projects: (1) bio compatible collapsible reservoir for a pre-prototype lab-on-a-chip and (2) the complete development of a very novel micro loop heat pipe. In the latter case (LHP) a small 1x1 cm. MEMS (micro electro mechanical systems) based silicon LHP cell was developed and tested, which is intended as a pre-prototype for arbitrary lateral planar expansion in multiple cells for cooling electronic chips and other systems, in terrestrial and space applications (e.g. solar cell farms for energy beaming back to earth). The author as a member of a team of MEMS researchers and thermal science researchers, concentrated mainly on packaging research and development, and measurement issues. The micro loop heat pipe is unique in that the wick is planar, is made of semiconductor grade silicon and is fabricated by the unique application of a photon enhanced micro-patterned anisotropic electrochemical process (developed elsewhere for other applications but refined in this lab), locally referred to as “coherent porous silicon”. The resulting micro-capillary arrays were in the low micron range, with up to several million such through-capillaries per square centimeter. Also “quartz wool” has been demonstrated to serve well as a secondary or even primary wick with multi-micron effective pore size and porosity in the range of 95 percent. In the packaging works, several unique processes have been developed, or applied, including new bonding techniques, new instrumentation approaches and new application of ultrasonic impact grinding to form otherwise unattainable MEMS packaging systems. Cooling has been demonstrated up to about 60Watts/cm2, while maintaining top cap temperatures well bellow military specifications for microelectronics. Calculated cooling of over 300°C has been achieved in this passive device which requires no pumps or external power. However it is believed that improvements are pos (open full item for complete abstract)

Committee: H Henderson (Advisor) Subjects:

Doctor of Philosophy (Ph.D.), University of Dayton, 2022, Electrical and Computer Engineering

Autonomous vehicles make use of an Inertial Navigation System (INS) as part of vehicular sensor fusion in many situations including Global Navigation Satellite System (GNSS)- denied environments such as dense urban places, multi-level parking structures, and areas with thick tree-coverage. The INS unit incorporates an Inertial Measurement Unit (IMU) to process the linear acceleration and angular velocity data to obtain orientation, position and velocity information using mechanization equations. In this work, we developed a novel deep learning-based methodology, using Convolutional Neural Networks (CNN) to reduce errors from MEMS IMU sensors. We developed a methodology of using CNN algorithms that can learn from the responses of a particular inertial sensor while subject to inherent noise errors and provide a near real-time error correction. We implemented a time-division method to divide the IMU output data into small step sizes. By using this method, we make the IMU outputs fit the input format of the CNN. We optimized the CNN algorithm for higher performance and lower complexity that would allow its implementation on ultra-low power hardware such as microcontrollers. We examined the performance of our CNN algorithm under various situations with IMUs of various performance grades, IMUs of the same type but different manufactured batch, and controlled, fixed and un-controlled vehicle motion paths.

Committee: Vamsy Chodavarapu (Committee Chair); Manish Kumar (Committee Member); Guru Subramanyam (Committee Member); Tarek Taha (Committee Member) Subjects: Electrical Engineering

Doctor of Philosophy (PhD), Ohio University, 2022, Electrical Engineering & Computer Science (Engineering and Technology)

Integrating highly directional optical radios into next generation wireless systems is increasingly gaining traction due to the potential benefits to be derived from the several terahertz (THz) of spatially reusable spectrum available. In this dissertation, we explore three main research problems within the domain of laser-based free space optical networks and which fall under the broader areas of optimal multicast, neighbor discovery and link quality indication. For the optimal multicast problem, we show that the static version of this problem is an abstraction of the minimum weight set cover problem which is known to be NP-hard. A computationally cheap greedy local optimum heuristic is then proposed which has a time complexity of O(N) compared to the O(N^2) time complexity of the well known O(log N) approximation algorithm to the set cover problem. We then proceed to the version of the optimal multicast problem in mobile scenarios, and show that it is an abstraction of the time dependent prize collecting traveling salesman problem which is NP-hard. In formulating our problem, we develop a novel prize assignment strategy that guarantees the selection of mutually disjoint multicast sets. Due to the problem being NP-hard, we provide several potential heuristics for multicast in mobile scenarios. We evaluate the performance of these multicast algorithms in delay tolerant networking conditions, and in a typical 5G backhaul network. For the multicast problem, we assumed that nodes knew the transceiver orientations of recipients via the dissemination of coordinates obtained via the global positioning system (GPS) over a low rate omnidirectional radio frequency (RF) channel. However, in delay averse and high throughput self configuring networks, nodes might not possess GPS capabilities. In addition, they might not have a control channel. Agile neighbor discovery in such situations is then of critical importance. Given an optical wireless network with MicroElectroMechan (open full item for complete abstract)

Committee: Harsha Chenji (Advisor) Subjects: Computer Engineering; Computer Science; Electrical Engineering

MS, University of Cincinnati, 2021, Engineering and Applied Science: Electrical Engineering

Respiratory rate (RR) serves as a vital sign for health care and disease monitoring to provide important indications of physiological conditions; its measurement and analysis can address a wide range of health applications to assist in the early detection of abnormal respiration issues. For example, in recent years millions of people around the world have suffered from undiagnosed respiration issues such as chronic obstructive pulmonary disease (COPD) and asthma; continuous monitoring of RR may help early detection of such issues to prevent its aggravation into chronic conditions and allow more effective treatment and improved quality of life. Many approaches have been explored to monitor the breathing pattern and measuring RR. However, a wearable monitoring system is still lacking for continuous accurate real-time RR measurements without interfering everyday life. This thesis work aims to develop a real-time low-power wireless microsystem based on a miniature microphone and a microcontroller unit (MCU) to continuously monitor respiration for accurate RR measurements. The system has a small footprint and is intended to be wearable with unrestricted mobility and flexibility for the user to participate in daily life. This system consists of two parts: a hardware platform for recording breathing sound and an algorithm for analyzing respiratory activity and extracting RR. For the hardware platform, a commercial microphone based on microelectromechanical systems (MEMS) technology and a customized acoustic chamber are used to enable the sensor platform to collect breathing sound from target sites on the upper chest or neck. The MCU is ARM Cortex M4 based and has a library of relevant functions for digital signal processing (DSP) to allow basic on-chip data processing. The dimension of the fabricated printed circuit board for initial tests of the hardware platform is 38.42 ×38.65 mm2. An efficient algorithm was developed and optimized (open full item for complete abstract)

Committee: Tao Li Ph.D. (Committee Chair); Xuefu Zhou (Committee Member); Chong Ahn Ph.D. (Committee Member) Subjects: Electrical Engineering

Doctor of Philosophy, The Ohio State University, 2021, Mechanical Engineering

With the advantages of high bandwidth and abilities to see through opaque materials, millimeter wave (mmW) band (30 to 300 GHz) has been intensively explored in recent years. Although there are increasing demands for reconfigurable mmW systems for their potential applications in defense, switching, imaging, and sensing, overcoming the limitations such as high losses and large power consumption in mmW systems is still a challenge. Phase change materials (PCM) like vanadium dioxide (VO2), which have novel and tunable physical properties such as electrical resistivity and optical transmittance, are appealing choices for mmW reconfiguration to provide faster operation speed and lower loss microsystems. One aspect of VO2 thin film that is not fully exploited is the metal-insulator transition (MIT) region, where the electrical resistivity changes about four orders of magnitude with external stimuli. In this work, we present a highly sensitive antenna-coupled VO2 microbolometer for mmW imaging. The proposed microbolometer takes advantage of the large thermal coefficient of resistance (TCR) of VO2 at the non-linear region. The thermal resistance of the device is significantly improved by micro-electro-mechanical systems (MEMS) techniques to suspend the device above the substrate, compared with non-suspended microbolometers. The finite element method is employed to analyze the electrothermal and electromagnetic performance of the device. The frequency range of operation is 65 to 85 GHz, and the realized gain at broadside is > 1.0 dB. Simulation results indicate a high responsivity of 1.72x10^3 V/W and a low noise equivalent power (NEP) of 33 pW/√Hz. Targeting for broader applications, it is highly desired to deposit VO2 thin films on silicon (Si) substrate. Here, we employ the annealed alumina (Al2O3) buffer layers to obtain high-contrast VO2 thin films. The fabrication details for the Al2O3 buffer layers using atomic layer deposition (ALD) and VO2 thin films using DC sput (open full item for complete abstract)

Committee: Nima Ghalichechian (Advisor); Hanna Cho (Committee Member); Renee Zhao (Committee Member) Subjects: Electrical Engineering; Materials Science; Mechanical Engineering; Nanotechnology

Master of Science, University of Toledo, 2020, Mechanical Engineering

Thin-film pressure sensors have received widespread attention in recent times due to its ease of manufacture, characterization, and fatigue strength. Commercial fabrication of these sensors is inexpensive and compatible with the current manufacturing technologies. It has been found that the sensitivity of the flexible pressure sensor depends on the sensing pressure, the microstructural dispersion of nanoparticles, and the compatibility of the binder and the nanoparticles. The binder/particle dispersion should be such that it facilitates the formation of a greater number of conduction paths with a slight change in sensing pressure. The objective of this thesis includes the fabrication and characterization of a thin-film pressure sensor using different novel materials. The first material to be investigated was ZnO. ZnO thin-film materials that have received a great deal of attention due to its unique properties of being a semiconductor with wide bandgap and piezoelectric effect. The sensor characteristic of ZnO was compared with barium-titanate (BaTiO3) Gallium arsenic (GaAs) and Polyvinylidene fluoride (PVDF). The second material to be investigated was aluminum-doped zinc oxide (AZO). AZO has attracted a great deal of attention in many applications because of its nontoxicity, abundancy, and lower cost than other materials such as indium tin oxide (ITO). The AZO films were deposited on polyethylene (PE) substrates by a radiofrequency (rf) magnetron sputtering method. The piezoresistive sensor was tested for different pressures in vacuum and gage pressure conditions. The response characteristics indicated that resistance increased with the bending of the AZO layer in both compressive and tensile operation modes. The sensor characteristics exhibited that the AZO piezoresistive sensor can be used to measure ambient pressure quantitatively. This investigation indicated that AZO can be used as an alternative material for the fabrication of pressure sensors. Lastly (open full item for complete abstract)

Committee: Ahalapitiya Jayatissa (Committee Chair); Anju Gupta (Committee Member); Adam Schroeder (Committee Member); Raghav Khanna (Committee Member) Subjects: Engineering; Mechanical Engineering

Doctor of Philosophy (Ph.D.), University of Dayton, 2020, Electro-Optics

In this dissertation a fabrication process is developed to reliably create suspended waveguides with optical grating features. Two potential applications for suspended waveguides with optical gratings are described, evanescent field sensors and stimulated Brillouin scattering lasers, along with procedures for design and fabrication of the devices. Development the of fabrication process is described in detail, to explain each choice of material and fabrication method. The optimized fabrication process is presented along with the full parameters and fabrication techniques used. Suspended optical gratings are fabricated successfully using this method, reliably creating suspensions of up to 1mm in length, ranging from 1μm to 5μm in width, and 400-450nm thick. The waveguides are optically characterized, revealing significant spectral features as a result of optically induced defects on the waveguides. These defects and their effects are thoroughly characterized through numerical modeling. Two methods to bypass the issues caused by these defects are presented: increased lithography resolution to create single mode or defect free waveguides, or the use of a high index cladding layer to force even large scale waveguides into single mode operation. Time resolved transmission measurements, using the defects to create stochastic spectral features, are completed as a proof of concept for these structures use as evanescent field sensors.

Committee: Andrew Sarangan Ph.D. (Committee Chair); Imad Agha Ph.D. (Committee Member); Augustine Urbas Ph.D. (Committee Member); Jay Mathews Ph.D. (Committee Member) Subjects: Engineering; Materials Science; Nanotechnology; Optics

Doctor of Philosophy, Case Western Reserve University, 2020, EECS - Electrical Engineering

The pervasive Internet of Thing (IoT) revolution is driving the need for fundamental innovations in sensing, electronics, and ubiquitous computing that enable scalable, miniaturized, secure, and energy-efficient devices and networks. Due to some exceptional properties (such as small form factors, low phase noise thanks to ultra-high quality factor (Q), low power consumption, robustness to shock and vibration, amenability to monolithic integration with standard CMOS technology, compatibility with batch manufacturing, and wide operating temperature range), stable and self-sustained oscillators enabled by micro- and nano-electromechanical systems (MEMS and NEMS) devices have a myriad of applications including Internet of Things/Everything (IoTs/E) sensor nodes, next-generation wireless transceivers, RF signal processors, precision sensors, and navigation systems (e.g., GNSS). This dissertation focuses on ultra-stable MEMS-referenced oscillators for such applications. It describes the design, simulation, and experimental verification of three generations of digitally-programmable single-chip application-specific-integrated-circuits (ASICs) that can be integrated with MEMS and NEMS resonators to generate stable reference oscillators in the 10 kHz–16 MHz frequency range. We have also shown various functionalities of these amplifiers, including adaptive control of input impedance, automatic level control (ALC), automatic cancellation of parasitic electrical feedthrough in order to increase the signal to background ratio (SBR), optimizing the trade-off between tunability and stability, parametric pumping, frequency-locked loop (FLL) to stabilize the output frequency, and phase-controlled-closed-loop (PCCL) operation to find the optimal operating point. The chips have been used to realize i) 7 MHz ultra-stable (-105 dBc/Hz @ Δf = 10 Hz) single and quadrature oscillators based on an ultra-high-Q ( 3.2 × 10^6 at Vp = 35V) wafer-level vacuum-encapsulated single-cryst (open full item for complete abstract)

Committee: Soumyajit Mandal PhD (Committee Chair); Christian Zorman PhD (Committee Member); Hossein Lavasani PhD (Committee Member); Xiong (Bill) Yu PhD (Committee Member) Subjects: Electrical Engineering

Doctor of Philosophy, The Ohio State University, 2020, Electrical and Computer Engineering

Inertial sensors became wearable with the advances in sensing and computing technologies in the last two decades. Captured motion data can be used to build a pedestrian inertial navigation system (INS); however, time-variant bias and noise characteristics of low-cost sensors cause severe errors in positioning. To overcome the quickly growing errors of so-called dead-reckoning (DR) solution, this research adopts a pedestrian INS based on a Kalman Filter (KF) with zero-velocity update (ZUPT) aid. Despite accurate traveled distance estimates, obtained trajectories diverge from actual paths because of the heading estimation errors. In the absence of external corrections (e.g., GPS, UWB), map information is commonly employed to eliminate position drift; therefore, INS solution is fed into a higher level map-matching filter for further corrections. Unlike common Particle Filter (PF) map-matching, map constraints are implicitly modeled by generating rasterized maps that function as a constant spatial prior in the designed filter, which makes the Bayesian estimation cycle non-recursive. Eventually, proposed map-matching algorithm does not require computationally expensive Monte Carlo simulation and wall crossing check steps of PF. Second major usage of the rasterized maps is to provide probabilities for a self-initialization method referred to as the Multiple Hypothesis Testing (MHT). Extracted scores update hypothesis probabilities in a dynamic manner and the hypothesis with the maximum probability gives the correct initial position and heading. Realistic pedestrian walks include room visits where map-matching is de-activated (as rasterized maps do not model the rooms) and consequently excessive positioning drifts occur. Another MHT approach exploiting the introduced maps further is designed to re-activate the map filter at strides that the pedestrian returns the hallways after room traversals. Subsequently, trajectories left behind inside the rooms are heuristically adjus (open full item for complete abstract)

Committee: Alper Yilmaz Prof (Advisor); Keith Redmill Prof (Committee Member); Charles Toth Prof (Committee Member); Janet Best Prof (Other) Subjects: Electrical Engineering; Engineering

Doctor of Philosophy, The Ohio State University, 2020, Electrical and Computer Engineering

With an increasing demand for high-speed wireless communication, current wire- less infrastructure cannot provide the bandwidth required for high-speed data transfer for multiple users. The next generation of millimeter-wave (mmW) communication systems operate in the frequency range of 30–300 GHz and can provide orders of magnitude greater bandwidth. In addition, these systems rely on adaptive strategies to achieve high data-rate communication which requires reconfigurable elements. In our research, we introduce a new class of reconfigurable radio frequency (RF) microsystems using paraffin phase-change material (PCM) that enables low-loss recon- figuration for mmW components. Paraffin (alkane) is a low-loss nonpolar dielectric that undergoes a 15% reversible volume change through its solid to liquid phase transition. Using this unique combination of loss characteristics and mechanical properties, we have developed continuously variable capacitors. These electro-thermally actuated variable capacitors are low loss with series resistance of less than 0.7 Ω at the mmW band and can be monolithically integrated with antennas and RF components to introduce reconfiguration. In this work, we present a frequency reconfigurable slot antenna which covers the 94 GHz–102 GHz band. In order to achieve reconfiguration, the slot antenna is loaded with two paraffin PCM capacitors. The capacitors are actuated using joule heaters and with the increase in temperature, paraffin goes through a solid to liquid transition. As the volume of the paraffin increases, the capacitance decreases continuously by approximately 15%, which results in increasing the resonance frequency. The realized gain of the antenna at 100 GHz is 3 dBi and it is approximately constant over the reconfiguration range. The Efficiency of the antenna is >72% for the entire reconfiguration range thanks to the low dielectric loss of the paraffin. To evaluate the performance gains of the reconfigurable antennas, new p (open full item for complete abstract)

Committee: Nima Ghalichechian Professor (Advisor); Khalil Waleed Professor (Committee Member); Kubilay Sertel Professor (Committee Member); Kisha Radliff Professor (Committee Member) Subjects: Electrical Engineering; Electromagnetics

Doctor of Philosophy (PhD), Wright State University, 2019, Engineering PhD

Drop on demand (DOD) inkjet printing has been widely investigated for its low cost, noncontact, high throughput, and reproducible process advantages. This dissertation research sought to capitalize on these advantages for use in micro solid oxide fuel cells (micro SOFCs). Understanding the important variables underpinning the inkjet process, including ink formulation, jet kinematics, and process settings was essential. These variables were evaluated for their impact on drop deposition quality, resolution, microstructure, and electrochemical functionality, with the end goal of making submicron to micron scale ceramic features. Initially, the fluid kinematics of single pass printing was investigated using a dilute, solid-solvent, colloidal, ink suspension of of La0.6Sr0.4Fe0.8Co0.2O3 (LSFC) and α-terpineol. Favorable process conditions were identified that attained uniform, well-shaped, circular dots ~ 0.1 μm thick and ~ 80 μm in diameter. Multiple, sequential ink passes were employed to increase feature dimensions on the x/y/z axes. This required additional process constraints to control deposition quality and resolution of micro features including micro-dots (0-D), micro-lines (1-D) and micro-planes (2-D). Using optimal conditions, 0-D dots and 1-D lines with x/y dimensions < 100 μm and z axis dimensions < 1 μm with dense, open or networked microstructures were demonstrated; in addition 2-D planes having smooth surface and continuous intra-planar ceramic coverage with dimensions as small as ~ 100 μm by ~ 100 μm were achieved. Sintering the inkjetted submicron prototypes produced consolidated submicron films that were uniform, smooth and void of defects such as cracks or delamination. Thermal treatments resulted in grain growth from an average crystallite size of ~158 nm to ~ 356 nm. Heat treatments < 800°C were essential to avoid deleterious effects on electrochemical activity. Electrochemical characterizations of prototypes produced tolerable peak power (open full item for complete abstract)

Committee: Hong Huang Ph.D. (Advisor); Sharmila Mukhopadhyay Ph.D. (Committee Member); Jason Deibel Ph.D. (Committee Member); Lei Kerr Ph.D. (Committee Member); Thomas Reitz Ph.D. (Committee Member) Subjects: Engineering; Materials Science

Master of Sciences (Engineering), Case Western Reserve University, 2019, EECS - Electrical Engineering

AlN is in an attractive piezoelectric material for energy harvesting, as it is compatible with Integrated Circuit (IC) CMOS fabrication and MEMS (micro‐electromechanical systems). Its material compatibility permits easier industrialization and integration with SOCs (systems‐on‐a‐chip). However, due to feature size and material properties, state‐of‐theart MEMS‐scale AlN harvesters typically have natural frequencies above 200 Hz, preventing useable power output in applications with lower frequency power spectra. In this thesis, finite element analysis was used to explore whether meandering‐spring device geometry could lower the natural frequencies of MEMS‐based energy harvesters. ANSYS® Mechanical™ was used for design and modeling, and Sandia Lab's RF MEMS process provided input for process parameters. For a 5x6 mm AlN vibration harvester, this work showed that one pair of meanders was sufficient for producing a natural frequency below 200 Hz, and that by adding additional meanders, a natural frequency of 29.9 Hz was possible.

Committee: Christian Zorman Dr. (Committee Chair); Francis Merat Dr. (Committee Member); Michael Fu Dr. (Committee Member) Subjects: Electrical Engineering

Doctor of Philosophy, Case Western Reserve University, 2019, EECS - Electrical Engineering

Resonant nanoelectromechanical systems (NEMS) made from two-dimensional (2D) crystals have attracted increasing research interest owing to their promises for exceptionally high responsivities and sensitivities to external stimuli, enabled by their ultralow weight and ultrahigh surface-to-volume ratio. Although 2D crystals with bandgaps ranging from 0 eV to 2 eV have been studied in earlier explorations (such as 0 eV graphene, 0.3-1.5 eV black phosphorus, 1.2-1.9 eV MoS2, etc.), resonant NEMS utilizing ultra-wide bandgap (UWBG) 2D materials or materials with quasi-2D nanostructures have not yet been demonstrated. The adoption of UWBG materials in NEMS resonators could offer new opportunities for interactions with ultraviolet (UV) photons and for high power handling capabilities. This dissertation presents the experimental demonstrations of UWBG resonant NEMS, specifically, hexagonal boron nitride (h-BN) and beta gallium oxide (β-Ga2O3) NEMS resonators, for investigations of both fundamental device physics and engineering of device functions and performance toward the perspectives of technological applications. In this dissertation, the dry transfer techniques in accordance with the analysis in discerning the thin UWBG material flakes are first discussed, followed by the thermal annealing method to boost the resonator performance. Then, experimental demonstration of h-BN 2D nanomechanical resonators vibrating at high and very high frequencies (HF/VHF), and investigations of the elastic properties of h-BN by measuring the multimode resonant behavior of these devices are presented. Following the h-BN resonators, single-crystal β-Ga2O3 nanomechanical resonators using β-Ga2O3 nanoflakes grown via low-pressure chemical vapor deposition (LPCVD) are demonstrated experimentally. From the measurements, multimode resonances and spatial visualization of the multimode motion are resolved to extract the mechanical properties, i.e., material Young's modulus, EY = 261 GPa, (open full item for complete abstract)

Committee: Philip Feng (Advisor); Christian Zorman (Committee Member); Xiong Yu (Committee Member); Walter Lambrecht (Committee Member) Subjects: Electrical Engineering; Engineering; Experiments; Materials Science; Mechanical Engineering; Mechanics; Nanoscience; Nanotechnology; Optics; Physics; Technology

Master of Science, University of Toledo, 2018, Electrical Engineering

Sensors are playing an ever-increasing role in our daily lives, from portable electronics to our automobiles and health care devices. Micro electro-mechanical systems (MEMS) comprise the foundation of these sensors. MEMS allow for miniaturization and integration and make use of the same batch manufacturing processes as integrated circuits (ICs). Batch manufacturing techniques allow several thousand MEMS to be manufactured at once. In recent years several MEMS manufacturers have begun offering standardized processes and allow multiple designs on one wafer, greatly reducing the cost of prototyping a MEMS design. Current MEMS design suites impose several barriers to their use; high licensing fees, high processing power requirement, and a steep learning curve. Current expert design suites are made for users with a deep understanding of manufacturing processes. Design suites geared towards non-experts typically rely on a design paradigm unfamiliar to most, such as typed netlist or schematic layouts. These paradigms limit what is capable of being designed to a library of predefined devices or building blocks, thus limiting the type of MEMS capable of being designed and stifling innovation. To fully utilize the existing MEMS standardized processes and manufacturing services new design and simulation tools must be developed. These tools must mitigate the manufacturing process knowledge requirement present in existing tools while utilizing a design paradigm that does not limit the type of MEMS capable of being designed. In this thesis a novel web-based platform for MEMS design is presented. This platform makes use of cloud-based processing power and allows for simulation of MEMS whose underlying principle of operation is thermal expansion, electrostatics, or the piezoelectric effect. The platform allows users to create parametric, three-dimensional, parts that incorporate manufacturing constraints and share those parts with other users of the platform. Manufacturing co (open full item for complete abstract)

Committee: Daniel Georgiev (Committee Chair); Vijay Devabhaktuni (Committee Co-Chair); William Evans (Committee Member); Raghav Khanna (Committee Member) Subjects: Computer Science; Electrical Engineering

Master of Science, University of Toledo, 2018, Engineering (Computer Science)

Design and modeling of Micro-Electro-Mechanical Systems (MEMS) require in-depth knowledge of multiple disciplines due to the unique manufacturing processes involved in the fabrication of MEMS devices. Over the years, several pertinent MEMS modeling techniques such as finite element and nodal analysis have emerged within this growing research field. Well-established entities such as Coventerware and Comsol Multiphysics that are known for their efficacy in modeling devices have also applied/implemented these techniques in their work. Therefore, these techniques hold prominent value for further research. Furthermore, these software suites provide various advanced features and were developed considering broader usage. These software suites require a substantial amount of computation power and offer a steep learning curve. However, the beauty of Comsol Multiphysics lies in the Comsol Server with Java application programming interface, which enables access to Comsol's modeling capabilities with customized interfaces. This thesis proposes a three-tier cloud-based web model-view-controller (MVC) architecture as a proof-of-concept, which allows a user to design and model simple MEMS devices in the web browser without having to install any simulation software. This is accomplished by developing a loosely coupled MVC architecture with a web-based, lightweight CAD website view that interacts with the controller in an asynchronous fashion. Ultimately, this allows the user to store simulation data in a SQL-based data model. With regard to the modeling capabilities of the architecture, this thesis proposes an integration layer with Comsol Server as the back-end FEA simulation engine. Web-based simulation authoring and visualization results show that this multi-tier solution significantly improves modeling simplicity and accessibility to designers. Furthermore, the proposed architecture poses cost-effective advantages by eliminating the need for installing large CAD softwares (open full item for complete abstract)

Committee: Vijayakumar Devabhaktuni (Committee Chair); Daniel Georgiev (Committee Co-Chair); Devinder Kaur (Committee Member); Henry Ledgard (Committee Member) Subjects: Computer Science; Electrical Engineering; Information Technology

Master of Science, Miami University, 2018, Mechanical and Manufacturing Engineering

Haptic feedback is a highly beneficial feature of touch screens. Due to the limitations of current haptic technologies, devices with large touch screens are unable to provide haptic feedback to users. This study proposes and investigates an electrostatic actuator utilizing frequency beating phenomenon with the goal of generating haptic feedback in devices with large touch screens. A prototype device was fabricated and through experimentation, two unique high intensity vibration patterns were found at each beat frequency. An analytical model of the prototype was developed to. The model produced a peak vibration intensity distribution closely resembling that of the experimental data. The possibility of three input signals was investigated. Variations in beating patterns could be seen, but this provides little benefit in application. A multiphysics model was developed to provide a more accurate representation of the operation of the actuator. This model was also used do investigate the effects of the coupling of displacement and electrostatic force. The multiphysics model was able to produce accurate results but was unstable when using certain input conditions. The displacement coupling creates changes in the computed displacement and intensity response. The model produced the same peak intensity distribution as the experimental data. Improvements can be made to both models to improve accuracy and stability. The models are intended to aid in the refinement of the design of future prototypes.

Committee: Jeong-Hoi Koo Ph. D. (Advisor); Jens Mueller Ph. D (Committee Member); Kumar Singh Ph. D. (Committee Member) Subjects: Design; Mechanical Engineering

PhD, University of Cincinnati, 2017, Engineering and Applied Science: Electrical Engineering

Pressure and temperature are parameters essential for brain monitoring. Currently, the intracranial pressure (ICP) and intracranial temperature (ICT) are measured by the separate sensors/catheters in clinic. Although integrated ICP and ICT sensors with low cost and minimal damage to brain is highly favored, the integration of the sensors involves complicate assembly and packaging process, and also increases the diameter of micro-catheters. Researches have been done to develop integrated pressure and temperature sensors on the same platform, especially on flexible substrate, to minimize the damage to brain caused by the device implantation. However, the developed sensors are either merely prove-of-concept or difficult to be manufactured due to the complicate and costly process. This work proposes and explores novel approaches to develop the integrated flexible ICP and ICT sensors with low cost and simple process. High quality polysilicon thin film was directly grown on flexible substrate as the sensing material for both ICP and ICT sensors with simple, fast, and low cost aluminum induced crystallization (AIC) process. A continuous P-type polysilicon film with the crystals' average size of 49 nm was developed and shown. Based on the polysilicon thin film, a flexible thermistor array was designed, developed and characterized. It achieved good in vitro performance with a sensitivity of -0.0031/°C, response time of 1.5 s, resolution of 0.1 °C, thermal hysteresis less than 0.1°C, and long term stability with drift less than 0.3 °C for 3 days in water. In vivo tests of the polysilicon thermistor showed a low noise level of 0.025±0.03 °C and the expected transient temperature increase associated with cortical spreading depolarization. In addition, polysilicon based flexible pressure sensor was developed for ICP measurement. The gauge factor of polysilicon thin film was characterized with a value of 10.316. The dimensions of the flexible piezoresistive pressure (open full item for complete abstract)

Committee: Chong Ahn Ph.D. (Committee Chair); Punit Boolchand Ph.D. (Committee Member); Leyla Esfandiari Ph.D. (Committee Member); Jed Hartings Ph.D. (Committee Member); Chunyan Li Ph.D. (Committee Member); Ian Papautsky Ph.D. (Committee Member) Subjects: Electrical Engineering

Master of Science (M.S.), University of Dayton, 2017, Electrical Engineering

In this Thesis, the design and analysis of a mode-matched Disk Resonator Gyroscope (DRG) characterized by high Quality factor exceeding 1 million is presented. The resonator is designed using Micro Electro Mechanical Systems (MEMS) Integrated Design for Inertial Sensors (MIDIS) process offered by Teledyne DALSA Semiconductor Incorporated (TDSI). The MIDIS process offers wafer-level vacuum encapsulation at 10 mTorr and includes Through Silicon Vias(TSVs) that allows flip chip bonding with an integrated circuit for signal detection and processing. Wafer-level encapsulation with ultra-low leak rate is achieved by using MIDIS process, with leak rate as low as 6.58E-18 atm.cm3/s. The DRG design has a circular shape of 600 µm diameter with a single crystal silicon device layer thickness of 40 µm. The designed DRG has a resonant frequency of 277.54 kHz in drive mode and 278.30 kHz in sense mode. The frequency split between drive and sense modes is 760 Hz. A Quality factor of 1.34 million is achieved for the designed DRG.

Committee: Vamsy Chodavarapu Dr. (Committee Chair); Guru Subramanyam Dr. (Committee Member); Weisong Wang Dr. (Committee Member) Subjects: Electrical Engineering; Mechanical Engineering