Master of Science in Engineering (MSEgr), Wright State University, 2008, Mechanical Engineering

Vibrations at a resonant frequency lead to catastrophic failure or at the very least, shorten the life span of the structure due to fatigue. These problems force engineers to implement damping techniques. Smart materials have been used over two decades to reduced vibration amplitudes. Recently, there has been much research and development on smart materials and structures.This work introduces an innovative approach for vibration suppression using passively shunted piezolectric materials. Initially linear circuit elements such as resistors, capacitors, and inductances, or building a non-linear circuit with different impedance designs were used. Instead of such elements, a switched electromechanical shunt has been proposed as a method to suppress vibrations of mechanical structures. In this state switching technique, bonded piezoelectric elements are switched from open circuit to closed circuit depending on the voltage produced from the piezoelectric patch. This new shunt circuit utilizes diodes. Diodes are nonlinear circuit elements and vibration amplitude is reduced due to introduction of nonlinearity into the system. A physics-based electro-mechanical model is developed and validated against experimental results. The smart plate consists of a rectangular aluminum plate modeled in cantilever configuration with surface bonded piezoelectric patches. Basic equations for piezoelectric sensors and actuators are presented. The equation of motion for the plate structure with bonded piezoelectric patch is depicted. The implementation of the circuit is demonstrated analytically and experimentally. The concept is demonstrated on two different modes and vibration peaks are lowered using the above mentioned circuit. Then a numerical model of the plate with the piezoelectric patch and the circuit is built in Simulink after designing a finite element model in ABAQUS. The data shows the effect of damping in Frequency Response Functions (FRFs) and in the response plots. A state-s (open full item for complete abstract)

Committee: Joseph Slater PhD (Advisor); Nathan Klingbeil PhD (Committee Member); Tommy George PhD (Committee Member) Subjects: Acoustics

Master of Science, The Ohio State University, 2007, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 2007, Graduate School

Committee: Not Provided (Other) Subjects:

Doctor of Philosophy, The Ohio State University, 2024, Nuclear Engineering

The nuclear industry continues evolving towards more reliable and powerful operations, and instrumentation technology must keep pace to ensure safety and consistency throughout the next generation of nuclear reactor designs. Sensor technology in extreme environments continues developing to meet these and other developing needs. These devices must tolerate very high temperatures, high irradiation dose, and related microstructural transformation. Piezoelectric surface acoustic wave (SAW) resonators are a class of microelectromechanical systems (MEMS) that utilize the modulation of surface acoustic waves as a physical sensing mechanism. A distributed network of small, lightweight, inexpensive sensors would allow improved characterization of reactor operating conditions and assist in the development and benchmarking of related models. Irradiation response of SAW devices must be thoroughly characterized. Device response is a result of competing mechanisms including defect generation, diffusion, recombination, and absorption. These mechanisms impact material properties including elastic constant, piezoelectric constant, and dielectric constant. This research utilizes in-situ observation of SAW resonators to characterize material behavior in a high-temperature neutron irradiation. Lithium niobate (LiNbO3), bulk aluminum nitride (AlN), and thin-film aluminum nitride (AlN/Al2O3) devices were tested up to 500oC temperature and 1.9 x 1012 n/cm2s neutron flux. Device resonant frequency, which is related to ultrasonic wave velocity, shifts in response to temperature and neutron flux. The dominant mechanism responsible for the altered wave velocity is determined by applying analytical models and identifying the best fit via correlation coefficient. Trends of the fitted parameters with temperature and neutron flux describe the characterization captured in this analysis. In SAW devices, elastic constants have been shown to be the primary mechanis (open full item for complete abstract)

Committee: Marat Khafizov (Advisor); Nathan Webb (Committee Member); Lei Cao (Committee Member); Thomas Blue (Committee Member) Subjects: Engineering; Experiments; Materials Science; Nuclear Engineering; Radiation

Master of Science in Electrical Engineering (MSEE), Wright State University, 2023, Electrical Engineering

Stochastic resonance (SR) is a phenomenon that can enhance the detection or transmission of weak signals by adding random noise to a non-linear system. SR introduced into the human motor control system as a subthreshold mechanical vibration has shown promise to improve sensitivity to haptic feedback. SR can be valuable in a laparoscopic surgery application, where haptic feedback is critical. This research sought to find if applying SR to the human motor control system improves performance in a laparoscopic probing task, if the performance differs based on the location of stochastic resonance application, and if there are sustained effects from SR after its removal. Subjects were asked to perform a palpation task using a laparoscopic probe to determine whether a series of simulated tissue samples contained a tumor. Subjects in the treatment groups were presented with a series of samples under the following conditions: Pre-SR, SR applied to the forearm or elbow, and Post-SR. Subjects in the control group did not have SR applied at any point. Performance was measured through the accuracy of tissue assessment, subjects' confidence in their assessment, and assessment time. Data from 27 subjects were analyzed to investigate the application of stochastic resonance and its sustained effects to improve haptic feedback sensitivity in a simulated laparoscopic task. The forearm group was shown to have significant improvement in the accuracy of tissue identification and sensitivity to haptic feedback with the application of SR. Additionally, the forearm group showed a greater improvement in accuracy and sensitivity than the elbow group. Finally, after SR was removed, the forearm group showed sustained significant improvement in accuracy and sensitivity. Therefore, the experiment results supported the hypotheses that stochastic resonance improves subjects' performance and haptic perception, that performance improvement differs based on application location, and that subjec (open full item for complete abstract)

Committee: Luther Palmer III, Ph.D. (Advisor); Caroline Cao Ph.D. (Committee Member); Katherine Lin M.D. (Committee Member) Subjects: Biomedical Engineering; Biomedical Research; Engineering; Health; Health Care; Mechanical Engineering; Surgery

Doctor of Philosophy, Case Western Reserve University, 2023, Macromolecular Science and Engineering

Piezoelectric polymers hold great potential for various electromechanical applications but only show low performance with d31 and -d33 < 30 pC/N, as compared to ferroelectric ceramics with piezoelectric coefficients over 100 pC/N and usage temperature over 100 °C. It is known that piezoelectricity in ferroelectric polymers originates from the electrostrictive effect coupled with a remanent polarization. Based on the physics, three factors are related to the piezoelectric performance of a ferroelectric polymer: remanent polarization, dipole mobility, and dimensional effect. Correspondingly, we have practiced these three methods to enhance the piezoelectric coefficient and piezoelectric thermostability. In Chapter 2, we discuss the polarization effect on the piezoelectricity in a highly poled biaxially oriented poly(vinylidene fluoride) film (BOPVDF). A considerable amount of orientated amorphous fraction (OAF) has been found with liquid crystal-like behavior. It was later verified to enhance the piezoelectricity by increasing the overall dipole alignment or polarization. Chapter 3 discusses the dipole mobility effect on piezoelectricity. In a poly(vinylidene fluoride-co-trifluoroethylene) [P(VDF-TrFE)] copolymer with extended-chain crystal (ECC) structure, we found relaxor ferroelectric-like secondary crystals (SCs) inside the OAF region (i.e., SCOAF). From dielectric characterization, dipoles in the SCs exhibit high mobility. Further, by in-situ heating XRD experiment, the melting of SCs led to the disappearance of piezoresponse. Then, we applied high-power ultrasonication to a PVDF homopolymer to induce similar SCOAF structures. The ultrasound-treated PVDF had a high d31 (76.2 ± 1.2 pm V-1) and good piezoelectric thermostability up to 110 °C, which is comparable with BaTiO3 piezoceramics. In Chapter 4, the dimensional effect on piezoelectricity is studied. By electrospinning, P(VDF-TrFE) fiber mats were prepared with a squeezable structure to ensure (open full item for complete abstract)

Committee: Lei Zhu (Committee Chair); Ica Manas-Zloczower (Committee Member); Michael Hore (Committee Member); Kenneth Singer (Committee Member) Subjects: Materials Science; Plastics

Master of Sciences (Engineering), Case Western Reserve University, 0, EECS - Electrical Engineering

Atrial fibrillation (Afib), the most common type of cardiac arrhythmia, affects an estimated 2.7-6.1 million people in the United States and often leads to hospitalization, stroke, sudden cardiac death, and heart failure. Of the available treatments for Afib, catheter ablations are the most effective with success rates of around 75%. Inter-operator variability associated with operator experience influences success rates. Current standard practices use x-ray fluoroscopy imaging to guide the procedure. This imaging technique exposes the patient and medical personnel to harmful radiation and has limitations in image quality. The implementation of a real-time MRI-guided robotic-assisted catheter ablation system can eliminate radiation exposure, provide superior guidance, reduce inter-operator variability, and could result in increased success rates in the treatment of Afib. Such a system is being developed at the Case Western Reserve University Medical Robotics and Computer Integrated Surgery (CWRU MeRCIS) laboratory. This thesis discusses the development of the electronics, software, and mechanical designs of the insertion mechanism for the main catheter and transseptal needle for this system. The system has been designed and tested for safe and reliable operation in an MRI environment, and in-vitro testing of the mechanism to puncture the fossa ovalis into the left atrium has been completed. This project and the results associated, show a proof of concept for the design and operation of the insertion mechanism of a real-time MRI-guided robotic-assisted cardiac ablation catheter system.

Committee: Cenk Çavuşoğlu (Committee Chair); Christian Zorman (Committee Member); Francis Merat (Committee Member) Subjects: Biomedical Engineering; Biomedical Research; Electrical Engineering

Master of Science (M.S.), University of Dayton, 2022, Electro-Optics

Large electro-optic crystals can suffer from an undesired piezo-electric ringing effect, which can significantly reduce the on-off contrast ratio for the modulator. First, the applied voltage across the electro-optic crystal excites acoustic modes of the crystal through the elasto-optic effect. The shape and frequency of these stress waves are related to the geometry of the crystal. The complex stress patterns, in turn, affect the optical response of the EO crystal due to the piezo-electric effect, making the performance of electro-optic modulators difficult to simulate and model. This work proposes a way to model these complex couplings using common finite element analysis and beam propagation techniques. The piezo-electric ringing of a deuterated potassium dihydrogen phosphate crystal is simulated and the results are compared to experimental observations. Finally, this work simulates a scenario which mitigates this undesirable elasto-optic effect in this material, and proposes methods of mitigating this effect for other electro-optic crystals.

Committee: Partha Banerjee (Advisor); Swapnajit Chakravarty (Committee Member); Rudra Gnawali (Committee Member) Subjects: Optics

MS, University of Cincinnati, 2022, Engineering and Applied Science: Electrical Engineering

Severe peripheral nerve injuries are currently limited in their available treatment approaches. Standard clinical therapies include the use of nerve grafts or nerve conduits to guide axons across the injury gap, however many of these approaches show variable outcomes in functional recovery, possibly due to a lack of cues directing the nerve regeneration. Polyvinylidene flouride triflouroethylene (PVDF-TrFE) is a piezoelectric polymer that generates electric charge in response to mechanical deformation, and can provide a suitable regenerative microenvironment by imparting electrical stimulation to direct peripheral nervous system cells and function. In this thesis, PVDF-TrFE nanofibrous scaffolds are fabricated through electrospinning and are extensively characterized for their material and electrical properties. Further, the PVDF-TrFE scaffolds are functionalized with decellularized extracellular matrix (dECM), presenting a promising outlook for a piezoelectric biomaterial for tissue engineering.

Committee: Leyla Esfandiari Ph.D. (Committee Member); Tao Li Ph.D. (Committee Member); Greg Harris Ph.D. (Committee Member) Subjects: Electrical Engineering

Doctor of Philosophy, University of Akron, 2021, Mechanical Engineering

Nowadays, the automotive industry is paying more attention to autonomous vehicles; as a result, the importance of tire safety is increased. Since tires are the only contact between the vehicle and the road, monitoring the parameters such as tire pressure and temperature, friction between tire and road, and tire wear is essential to ensure vehicle safety. These parameters are monitored with the sensors embedded in intelligent tires. These sensors need electric power for operation. To provide the electric power for the intelligent tire sensors, piezoelectric energy harvesters (PEHs) can be used to harvest a part of tire deflection waste energy to provide electric power to the sensors. Two new shapes of piezoelectric energy harvester inspired from Cymbal piezoelectric energy harvester were designed. It has been proven that the Cymbal piezoelectric energy harvester is effective in vibration energy harvesting. Two new shapes are inspired by cymbal energy harvester, and they are developed to harvest strain energy from rolling tires. It is the first time this type of energy harvester based on the Cymbal geometry is used for the intelligent tire application. To ensure that these new designs will be safely and effectively embedded on the inner surface of tires, some modification on the shape, size, and design was made. The output voltage, power, and energy of the designed PEHs were evaluated through the developed Multiphysics model and experimental analysis. In order to run the experimental analysis, a wireless measurement system is developed. The PEH will be undergoing cyclic loading in the tire application. Therefore, the fatigue failure of the piezoelectric material is also considered in the design stage. The PEH is designed to be used in autonomous vehicles tire to provide power to the tire sensors. Due to this application, the PEH is subjected to temperature change, tire inflation changes, vehicle speed changes, and tire load changes due to this application. Therefore (open full item for complete abstract)

Committee: Siamak Farhad (Committee Chair); Truyen Van Nguyen (Committee Member); Ping Yi (Committee Member); Chen Ling (Committee Member); Gopal Nadkarni (Committee Member) Subjects: Mechanical Engineering

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

Flexible sensors can be seamlessly integrated into arbitrarily curved surfaces including artificial skins, automotive structures, and wind sensing systems. Polyvinylidene fluoride (PVDF) films are excellent candidates for development of flexible devices owing to their large mechanical compliance, piezoelectric, and dielectric properties. In spite of their favorable properties, their inability to measure static loads and their large voltage response to changes in temperature (pyroelectricity) have limited them to only measurement of dynamic events and energy harvesting applications. The broad objectives of this research are to provide PVDF sensor systems with the ability to measure static loads, develop understanding of piezoelectric behavior and pyroelectric responses, and devise strategies to compensate their pyroelectric responses under non-isothermal conditions. A concurrent investigation of design and manufacturing techniques to embed PVDF sensors into metal structures for non-destructive testing applications is also presented. In order to increase resolution in wind pressure sensing applications, a PVDF-based capacitive sensing technology is found to be superior to piezoelectric PVDF pressure sensors owing to its inherent ability to measure static events and its low sensitivity to temperature changes. The performance of the flexible capacitive sensor is evaluated by integrating it with an airfoil-shaped anemometer developed for measurement of wind speed and direction. Each objective is accompanied by analytical or finite element models to aid and supplement the characterization effort. Intellectual merit: A framework for near-static strain and pressure sensing methods under varying environmental conditions using flexible PVDF films is presented using compensated charge amplification and change in capacitance techniques, backed by analytical modeling tools and practical implementation. A novel rapid fabrication process of metal structures embedded with pie (open full item for complete abstract)

Committee: Marcelo Dapino (Advisor); Hanna Cho (Committee Member); Renee Zhao (Committee Member) Subjects: Mechanical Engineering

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

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

Calcium phosphate (CaP) compounds have been used as orthopedic, spinal and dental implants, and bone graft substitutes for several decades. Their good biocompatibility and bioactivity and most importantly their resemblance to bone and teeth mineral, make them perfect for orthopedic applications. However, the available CaPs possess a major drawback of slow bone formation rate resulting in a longer time for recovery of patients. Thus, this affects the psychological, physical and economic well-being of the patient and their family members. Electrical stimulation has been proven to enhance the osseous formation in different animal studies which in turn led towards the development of different piezoelectric devices and piezoelectric/biomaterial composites. Keeping these facts in mind, present work utilized the piezoelectric nature of Barium titanate (BT) into the different CaP compounds. The prime focus of this thesis is to enhance the electrical properties of CaP such that it helps to promote early osteogenesis. Furthermore, the minimally invasive surgery demands for the injectable self-setting CaP formulations whereas dense CaP scaffolds are most for the load-bearing applications. To address these applications, we carried out two different projects, first being injectable monetite based piezoelectric bone cement and second sintered HA-BT piezobiocomposites. Interestingly, as far as our knowledge, no literature is available on the CaP bone cement with piezoelectric properties. Thus, the development of piezo- CaP bone cement is the first of its kind and signifies the novelty of this thesis. Here, BT particles act as a source of electrical energy during normal physical loading conditions. The incorporation of BT into CaPs results in three major advantages. First, it improves the electrical properties (dielectric constant, piezoelectric coefficient) of the CaPs. Second, considering CaPs as a preferable cell-growing scaffold, BT incorporation enhances osteoblast cell activ (open full item for complete abstract)

Committee: Sarit B. Bhaduri Ph.D. (Committee Chair); Mehdi Pourazady Ph.D. (Committee Member); Matthew Franchetti Ph.D. (Committee Member) Subjects: Mechanical Engineering

Doctor of Philosophy, Case Western Reserve University, 2017, Materials Science and Engineering

Bi(B'B")O3 - PbTiO3 type solid solutions in the morphotropic phase boundary region (MPB) are currently the most promising systems for high temperature piezoelectric applications. Bi-based systems have been shown to have enhanced Curie temperatures (Tc), which is an intrinsic limit for piezoelectricity, coupled with excellent piezoelectric properties at temperatures greater than the highest operating temperature for state-of-the-art Pb(Zr,Ti)O3 systems. However, as the Tc increases, thermal depoling becomes a key aspect in the characterization of the operating range of these systems targeted for high temperature applications. In this thesis, a multifaceted approach is pursued to elucidate the thermal effects on structure-property relationships through the use of impedance spectroscopy, X-ray diffraction (XRD) and high field measurements. A new ternary MPB system with the formulation BiScO3-Bi(Zn0.5Zr0.5)O3-PbTiO3 has been developed which improved upon the base BiScO3-PbTiO3 by reducing the loss tangent as a function of temperature while maintaining both a high Curie temperature (420°C) and stable properties up to the depoling temperature (380°C). The loss characteristics were improved further through the introduction of aliovalent dopants that affect the domain wall mobility. It was also observed that the phase ratio, which has a large effect on the dielectric and electromechanical properties, could be controlled through sintering temperature. The temperature stability of the newly developed piezoelectrics were investigated though thermal cycling in impedance spectroscopy. It was discovered that there is actually a range of temperature over which these materials depole, rather than at a single point, which can limit the operation even further. This work provides a guideline for studying high temperature piezoelectrics and emphasizes application limiting factors beyond the typical motivation to increase Tc. Hence, characterizing and improving the thermal depoling and (open full item for complete abstract)

Committee: Alp Sehirlioglu (Advisor); Mark De Guire (Committee Chair); Peter Lagerlof (Committee Chair); Christian Zorman (Committee Chair) Subjects: Materials Science

Master of Science, The Ohio State University, 2016, Electrical and Computer Engineering

RFID (Radio Frequency Identification) technology finds application in different sectors ranging from item level identification & handling to smart tracking in the healthcare industry. One very useful application is placing passive RFID tags inside tires to obtain critical information about tire condition which will ultimately result in improved road safety and vehicular performance. The challenge is that passive RFID technology capable of smart sensing and data logging while being self-powered from local energy harvesting sources is non-existent. This research presents the design of a reliable, in-tire passive UHF RFID tag structure capable of smart sensing, processing and data logging over time. A proof-of-concept application for counting tire revolutions using a prototype RFID tag is demonstrated and one possible approach to self-powering the tag is presented. In this thesis, the existing RFID IC technology is first reviewed and tested for in tire data sensing and logging using multiple sensors. After coming to the conclusion that existing RFID ICs lack efficient data processing and logging abilities, a novel tag circuit is developed by integrating a commercial RFID IC with an onboard microcontroller. A prototype battery operated tag board, is then developed and tested to demonstrate a proof of concept for in-tire data sensing and logging by counting tire revolutions. This achievement is followed by miniaturizing the tag circuit and improving its sensing and logging functionality. Finally, an approach to self-power the tag using piezo sensors has been presented.

Committee: Robert Burkholder (Advisor); John Volakis (Committee Member) Subjects: Electrical Engineering

Master of Science (M.S.), University of Dayton, 2015, Mechanical Engineering

An active, feedback vibration control strategy with the goal of abating gear whine noise in rear-wheel and all-wheel drive vehicles is developed. The control strategy was implemented using two small inertial (proof mass) actuators, mounted on the rear subframe of a luxury all-wheel drive sedan with independent rear suspension, as the active elements in this application. Acceleration information measured by accelerometers nearly-collocated with the actuators was used as the feedback signal. The effectiveness of active vibration control was successfully demonstrated by examining the extent of reduction in the shaker induced vibration of the rear subframe as well as the sound pressure inside the vehicle. The evaluation of the active control scheme was extended to rolling dynamometer tests, during which effective reduction of vibration of rear subframe and the pressure inside the vehicle were demonstrated.

Committee: Reza Kashani Ph.D. (Committee Chair); Dave Myszka Ph.D. (Committee Member); David Perkins Ph.D. (Committee Member) Subjects: Mechanical Engineering

Master of Dental Hygiene, The Ohio State University, 2015, Dentistry

There are two types of ultrasonic devices used by dental hygienists; magnetostrictive (M) and piezoelectric (P). Research supports using these devices during prophylaxes/periodontal debridement but there is little evidence determining which is superior. The purpose of this study was to determine if any differences between the magnetostrictive and piezoelectric scaling devices existed in calculus removal, patient preference and practitioner preference. Subjects included senior dental hygiene students and patients of The Ohio State University College of Dentistry. This double-blinded study employed a quantitative experimental randomized split mouth design on contra-lateral quadrants for the evaluation of calculus removed by each device. Five calibrated examiners recorded the presence of calculus on the quadrants assigned prior to and post treatment. Upon completion of each device, patients completed a visual analog scale (VAS) to gauge patient preference and each student completed a five point Likert survey to measure practitioner preference. Twenty-three subjects completed the study. Data reveals the M device removed more calculus than the P device (70.5% vs 66.1% respectively). Results from the student survey reveal the M device was significantly more user friendly than the P device. Device M scored an average total likert score of 21.0 vs. 18.7 for device P. Results from the patient VAS reveal M is preferred for discomfort, vibration and noise factors. This data provides strong evidence that device M is preferred for this group of hygiene students. However, all other differences in the data were not significant. This significant difference in student practitioner preference is likely due to a major limitation of the previous experience imbalance between the two devices. This reveals a need for required experiences with both ultrasonic devices throughout the dental hygiene students' clinical education.

Committee: Michele Carr MA (Advisor); Rachel Henry MS (Committee Member); John Walters DDS, MMSc (Committee Member) Subjects: Dentistry

Master of Sciences (Engineering), Case Western Reserve University, 2015, EECS - Electrical Engineering

Among the significant advances microelectromechanical systems (MEMS) have enabled in transforming portable low-power electronic devices and integrated energy-efficient systems, piezoelectric MEMS (PiezoMEMS) technologies take an important share of the contributions, especially the ones based on lead zirconate titanate (PZT). In this work, we study the PZT-based PiezoMEMS cantilevers on their mechanical and piezoelectric properties for potential applications. We first introduce the cantilever fabrication process used to achieve optimized piezoelectric properties and designed device structures. Then, we discuss the composite stacking of the cantilevers and the modeling of bending moment and stress distribution. We extract the piezoelectric coefficient of the PZT layer, which is e31 = -5 C/m^2. Next, we evaluate multimode resonances of the cantilevers using theoretical modeling, finite element simulation, and optical and electrical measurements. Finally, we characterize the energy conversion properties of such cantilevers and achieve multimode mechanical-to-electrical energy conversion in ultrasonic frequency ranges.

Committee: Philip Feng (Advisor); Soumyajit Mandal (Committee Member); Francis Merat (Committee Member) Subjects: Electrical Engineering

Doctor of Philosophy, Case Western Reserve University, 2014, Applied Mathematics

Piezoelectricity is a property of certain materials that allows the conversion of mechanic deformation into electric voltage potential, and vice versa. The wide use of piezoelectric materials, e.g., in transducer technology and energy harvesting makes the design problem of optimizing the material parameters and geometry an important target in scientific computing. In energy harvesting in particular, the design of devices with impedance resonances in a predetermined range is of special interest: Matching the resonances with the ambient vibration frequencies may lead potentially to higher efficiency of the device. Material scientist can rely on numerical simulations in the design and production of piezoelectric devices. Numerical simulations employ numerical techniques like finite element methods to generate information about the design starting from an input of material parameters. In the context of this thesis, these material parameters include the elastic, electromagnetic and piezoelectric constants. Because the quantitative values of the material parameters are often determined from simplified experiments based on some assumptions, the reliability of the results of the simulations depends on the validity of these assumptions. Optimization based approaches to the numerical acquisition of the material parameters normally give a single set of values which, in turn, identifies one specific material as the approximation of the target. From a practical point of view this may be too restrictive, because it leaves little flexibility when trying to develop materials with a certain desired response. In this thesis we approach the inverse problem of material characterization for piezoelectric materials from a Bayesian perspective. The main question addressed in this thesis is, how to choose the elastic, electromagnetic, and piezoelectric material parameters so that a target resonance frequency is achieved, and the band-pass impedance response outside the resonance (open full item for complete abstract)

Committee: Erkki Somersalo Dr (Advisor); Daniela Calvetti Dr (Advisor) Subjects: Applied Mathematics; Materials Science; Mathematics

Master of Science in Engineering (MSEgr), Wright State University, 2013, Electrical Engineering

Hearing loss is a prevalent issue, affecting all ages in innumerable occupations. Cochlear implants are one solution to sensorineural hearing complications; and though they are commonly used, the electronic devices have limitations in power consumption and external equipment. Piezoelectric films emulate the relationship between the basilar membrane and inner hair cell structures of the human cochlear epithelium, inducing a potential difference in response to sound pressure. Through proper MEMS fabrication and material selection, an artificial cochlear can be developed utilizing piezoelectrics, which is self-sustainable and functions naturally with the mechanisms of the human ear. This research investigates the feasibility of piezoelectric films in achieving adequate voltage output and frequency selectivity to replace the human cochlea. Piezoelectric samples were manufactured for different resonant frequencies and subjected to air vibrations, after which the resulting voltage was recorded. Through both simulated and experimental data, the necessary 5-10mV to stimulate nerve bundles connected to the hearing centers of the brain was realized. The response spanned the human speech register of 500 to 8000 Hz.

Committee: Yan Zhuang Ph.D. (Advisor); Robert Goldenberg M.D. (Committee Member); Reiter Chad Ph.D. (Committee Member) Subjects: Biomedical Engineering; Electrical Engineering; Materials Science