Software cognitive radios and Internet of Things (IoT) are recent interest areas that need low loss and low power consumption hardware. More specifically, the area of software cognitive radios requires that hardware be frequency agile and highly selective. Meanwhile, IoT relies on multiple low power sensor networks. By combining Complementary Metal Oxide Semiconductors (CMOS) technology with piezoelectric Micro-Electro-Mechanical Systems (MEMS), we can fabricate Systems-on-Chip (SoC) that can be used as filters or references (oscillators) and highly selective sensors. In this work we developed a die-level compatible process for the monolithic integration of Bulk Acoustic Resonators (BAWs) on CMOS for low power, reduced area and high-quality passives for radio frequency applications. Using CMOS as a fabrication substrate some stringent requirements were added to maintain the dies and the technology’s integrity. A few of these limitations were the need for a low thermal budget fabrication process, die handling and electro-static discharge (ESD) protection. The devices were first fabricated on glass for modeling extraction that was later used for the design of the integrated circuits (IC). Three integrated circuits were designed as substrates for the integration using IBM’s 180nm and TSMC’s 65nm technology. A monolithic BAW oscillator with a resonance frequency of 1.8GHz was demonstrated with an FOM ~186dBc/Hz, comparable to other academia work. Using the developed process, a membrane BAW structure (FBAR) was integrated as well. Using a susceptor coating and zinc oxide’s (ZnO) high temperature coefficient of frequency (TCF) the device was studied as an alternative uncooled infrared sensor. Finally, a reprogrammable IC and an RF PCB were designed for volatile organic compound (VOC) testing using self-assembled monolayers (SAMs) as the absorber layer.

Microssistemas eletromecânicos ou Micro-Electro-Mechanical Systems (MEMS), representam uma classe de dispositivos que combinam funções mecânicas e eletrônicas em escala micrométrica. Através do uso de técnicas de microfabricação, adaptadas da indústria de semicondutores, é realizada a integração entre estruturas móveis, sensores, atuadores e eletrônica, tornando possível a implementação de sistemas completos miniaturizados. Acelerômetros eletrostáticos estão entre os dispositivos MEMS mais comercializados hoje em dia, com venda anual em todo o mundo superior a 100 milhões de unidades e crescente a cada ano. Eles são geralmente fabricados utilizando-se três lâminas de silício espessas, coladas uma sobre a outra. A camada intermediária é obtida por processos de corrosão e consiste de uma grande massa de prova suspensa por uma ou mais vigas. Ela é separada das lâminas superior e inferior por um pequeno espaço vazio (gap), dando origem a dois conjuntos de capacitores de placas paralelas. A flexibilidade das vigas permite que a massa se mova proporcionalmente à aceleração externa e o seu deslocamento é estimado pela variação da capacitância do conjunto. O projeto destes sensores é uma tarefa complexa, já que os seus diversos requisitos de desempenho são, na maioria das vezes, conflitantes, isto é, se o projeto é modificado para melhorar uma característica, as demais são inevitavelmente afetadas e por isso técnicas de otimização devem ser utilizadas na etapa de projeto. Com o intuito de melhorar o desempenho de micro-acelerômetros capacitivos, são então propostas e avaliadas no atual trabalho duas técnicas de otimização distintas, sendo uma delas baseada em Otimização Paramétrica (OP) e a outra no Método da Otimização Topológica (MOT). A OP parte de uma topologia previamente definida e adota algumas de suas características geométricas como variáveis de projeto. Para levar em consideração incertezas nas dimensões e propriedades dos materiais, que é um elemento-chave na concepção e fabricação de dispositivos MEMS, neste trabalho a OP é combinada com o método da Otimização de Projeto Baseado em Confiabilidade ou Reliability-based Design Optimization (RBDO). Análises de confiabilidade de primeira ordem através do Método de Confiabilidade de Primeira Ordem, ou First-Order Reliability Method (FORM), são utilizadas para o cálculo das probabilidades envolvidas nesta formulação. Já o MOT combina o Método dos Elementos Finitos (MEF) e um modelo de material com algoritmos de otimização para encontrar a distribuição ótima de material em um domínio de projeto pré-estabelecido. As variáveis de projeto são as pseudo-densidades que descrevem a quantidade de material em cada ponto do domínio. Na modelagem pelo MEF utiliza-se elementos de placa estrutural do tipo Mixed Interpolation of Tensorial Components (MITC). Exemplos práticos utilizando ambas as abordagens são apresentados e os seus resultados discutidos com o intuito de se avaliar o potencial de cada técnica para o projeto de micro-acelerômetros capacitivos. / Micro-Electro-Mechanical Systems (MEMS) are a class of devices that combine mechanical and electronic functions on a micrometric scale. Through the use of microfabrication techniques, adapted from the semiconductor industry, the integration of mobile structures, sensors, actuators and electronics is performed, allowing the implementation of fully miniaturized systems. Electrostatic accelerometers are among the highest volume MEMS products nowadays, with worldwide annual sales topping 100 million units and growing steadily. Bulk-type accelerometers are generally manufactured using three thick silicon wafers, bonded together one on top of the other. The intermediate layer is obtained by etching processes and consists of a big proof mass suspended by one or more beams. It is separated from the upper and lower wafers by a small gap, resulting in two sets of parallel plate capacitors. The flexibility of the beams allows the mass to move proportionally to the external acceleration and its displacement is estimated by the change in capacitance of the set. The design of such sensors is a complex task, since they depend on many performance requirements, which are most often conflicting. If a design is modified to improve one characteristic, others are inevitably affected. Therefore, optimization techniques are regularly used in the design stage of MEMS sensors. Aiming to improve the performance of capacitive micro-accelerometers, in the present work two optimization techniques are presented, the first is based on Parametric Optimization (PO) and the other is the Topology Optimization Method (TOM). The PO starts from a predefined topology and uses some of its geometric characteristics as design variables. In order to account for uncertainties in the dimensions and material properties, which is a key element in the design and fabrication of MEMS devices, in this work the PO is combined with the Reliability-based Design Optimization (RBDO) method. The First-Order Reliability Method (FORM) is applied to calculate the probabilities involved in the RBDO formulation. The TOM combines the Finite Element Method (FEM) and a material model with optimization techniques to find the best constrained material distribution in a fixed design domain. The design variables are the pseudo-densities that describe the amount of material at each point of the domain. The FE model is discretized using the Reissner-Mindlin plate element with the Mixed Interpolation of Tensorial Components (MITC) formulation. Practical examples using both approaches are presented and discussed in order to evaluate the potential of each technique to the design of capacitive micro-accelerometers.

Um novo processo de fabricação de dispositivos de emissão de campo (FE) em silício (Si) é apresentado nesta tese, baseado na potencialidade de utilização da técnica de microusinagem denominada HI-PS (Hydrogen Ion Porous Silicon), que trata da combinação entre processos de implantação de hidrogênio e silício poroso. Por meio do procedimento proposto, foram obtidos dispositivos com 2500 emissores (micropontas de Si) integrados e não integrados ao anodo e contidos em uma área de 2,8 x 2,8 mm² (3,2.10\'POT.4\' pontas/cm²). As micropontas de Si fabricadas apresentaram altura de 10 µm, com diâmetro do ápice em torno de 150 nm. A separação entre os emissores (50 µm), na configuração não integrada dos dispositivos, foi limitada pela resolução da máscara litográfica utilizada. Foram propostas etapas de otimização estrutural das micropontas após sua formação, e aplicadas tanto na configuração do sistema anodo-catodo integrado como não integrado. Como resultado destas etapas, constatou-se a redução do ápice das microestruturas para dimensões inferiores a 100 nm. Os dispositivos FE integrados foram obtidos com uma distância de separação entre o anodo e o catodo de aproximadamente 12 µm, distância definida pelas dimensões da máscara litográfica, porém não limitada pelo processo aplicado. Destacam-se, entre as vantagens da utilização da técnica HI-PS em relação às tecnologias usuais de manufatura dos dispositivos FE, a baixa complexidade do processo proposto e a utilização de apenas uma etapa litográfica para obtenção do sistema anodo-catodo integrado e auto alinhado. Para efetuar as caracterizações dos dispositivos, foram implementados uma câmara de vácuo específica, que permite alterar a distância entre as estruturas do anodo e do catodo não integradas, sem a necessidade de se retirar a amostra da câmara, e três sistemas para ensaios elétricos, sendo um destes sistemas desenvolvido especificamente para caracterização elétrica de dispositivos FE. As caracterizações elétricas foram efetuadas por meio de curvas I-V, I-t e V-d, sendo esta última utilizada para extrair o campo elétrico macroscópico E, que foi utilizado como parâmetro de comparação entre amostras submetidas a diferentes processos de otimização estrutural e de recobrimento superficial dos emissores por Al. Todas as amostras caracterizadas apresentaram variação de corrente exponencial com o potencial aplicado, de acordo com o esperado pela teoria proposta por Fowler-Nordheim (F-N). Dispositivos com otimização estrutural ou deposição de Al apresentaram melhores características de emissão (menor valor de E), de acordo com o aprimoramento do modelo de F-N sugerido na literatura para superfícies otimizadas. Constatou-se, pelos gráficos de F-N, o comportamento diferenciado dos emissores de Si tipo p em comparação com outros materiais, estabelecendo uma relação entre as variações da inclinação da curva traçada às distintas fontes de elétrons do Si. Frente aos resultados obtidos, conclui-se que a técnica Hi-PS é altamente promissora para fabricação de emissores microusinados em Si para aplicações em dispositivos FE. / This thesis presents a new silicon (Si) field emission devices (FE) fabrication process based on the potential of the HI-PS (Hydrogen Ion Porous Silicon) micromachining technique, which is a combination of hydrogen implantation and porous silicon. Devices with 2500 emitters (Si microtips), integrated and non-integrated to the anode, enclosed in an area of 2.8 x 2.8 mm² (3.2 x 10\'POT.4\' tips/cm²), were obtained from the proposed technique. The fabricated Si microtips show 10 µm in height, with apex diameter of about 150 nm. The separation distance between emitters (50 µm), considering the non-integrated devices design, was limited by the resolution of the lithographic mask applied. Microtips structural improvement process steps were proposed and applied in both anode-cathode design (integrated and non-integrated). As a result, a reduction in tip apex diameter to dimensions lower than 100 nm was verified. The integrated FE devices were obtained with an anode-cathode separation of about 12 µm, which distance was defined by lithographic mask dimensions, but not limited by the process applied. The outstanding advantages of the HI-PS technique in comparison with usual technologies for FE devices fabrication are the low complexity of the process proposed and the use of a single lithographic step to obtain a selfaligned and integrated anode-cathode system. A dedicated vacuum chamber, which allows the changing of the separation distance between non-integrated anodecathode structures without the need of removing the sample out the chamber, and three systems for electrical test, being one of them developed specifically for FE devices electrical characterization, were implemented. The electrical characterizations were performed by means of I-V, I-t and V-d curves, being the last one used to extract the macroscopic electrical field E, which was applied as comparison parameter between samples obtained from distinct structural improvement process and samples with emitters surface coated with Al. All samples characterized showed exponential-like behavior of current with the potential applied, as expected from theory proposed by Fowler-Nordheim (F-N). Devices with structural improvement or Al coating showed better emission characteristics (lower E value), according with the modified F-N model suggested in the literature for optimized surfaces. From the F-N plots, the distinct behavior of p type Si emitters was verified in comparison with different materials, establishing a relationship between the slope variations of the curve obtained and the electrons source of the Si. Based on the results obtained, the HI-PS technique is very promising to fabricate Si micromachined emitters for use in FE devices.

Falls and fall-induced fractures are very common among the elderly. Hip fractures account for most of the deaths and costs of all the fall-induced fractures. This dissertation presents a novel MEMS based human airbag system used as a hip protector. A Micro Inertial Measurement Unit (muIMU) which is based on MEMS accelerometers and gyro sensors is developed as the motion sensing part of the system. The result using this muIMU based on Support Vector Machine (SVM) training to recognize falling-motions are presented, where we showed that selected eigenvector sets generated from 200 experimental data can be separated into falling and other motions completely. For real-time recognition, the SVM filter should be embedded to a high speed DSP system for fast computation and complex filter analyses. After the simulations for SVM filter and FFT were performed on a computer simulator (TI DSP320 C6713), we used DSK6713 (DSP Starter Kit) as our target board and integrated FFT and SVM filter on the chip. The whole algorithm works well with exist sensor data. Demo shows that our DSP system can successfully classify fall and non-fall states. At the same time, the system can trigger our airbag inflation mechanism when a fall occurs. The system was shown to open the airbag in real-time and protected the experimenter's hip area. / by Shi, Guangyi. / "March 2008." / Adviser: Wen Jung Li. / Source: Dissertation Abstracts International, Volume: 70-03, Section: B, page: 1855. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (p. 108-111). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

Tsang, Chi Chiu. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 66-69). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgement --- p.iii / Statement of Originality --- p.v / Table of Contents --- p.vii / List of Figures --- p.x / Nomenclature --- p.xii / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Motivation --- p.1 / Chapter 1.2 --- Objectives --- p.3 / Chapter 1.3 --- Contributions --- p.3 / Chapter 1.4 --- Thesis Organization --- p.4 / Chapter 2 --- A Ubiquitous Digital Writing System --- p.5 / Chapter 2.1 --- Introduction --- p.5 / Chapter 2.2 --- MEMS Motion Sensing Technology --- p.6 / Chapter 2.2.1 --- Micro-Electro-Mechanical Systems (MEMS) --- p.6 / Chapter 2.2.2 --- Principle of a MEMS Accelerometer --- p.6 / Chapter 2.2.3 --- Principle of a MEMS Gyroscope --- p.7 / Chapter 2.3 --- Architecture of Ubiquitous Digital Writing System --- p.8 / Chapter 2.3.1 --- Micro Inertial Measurement Unit (μlMU) --- p.8 / Chapter 2.3.2 --- Data Transmission Module --- p.10 / Chapter 2.3.3 --- User Interface Software --- p.10 / Chapter 2.4 --- Summary --- p.12 / Chapter 3 --- Calibration of μ-Inertial Measurement Unit --- p.13 / Chapter 3.1 --- Introduction --- p.13 / Chapter 3.2 --- Sources of Error --- p.13 / Chapter 3.2.1 --- Deterministic Errors --- p.13 / Chapter 3.2.2 --- Stochastic Error --- p.14 / Chapter 3.3 --- Calibration of Accelerometers --- p.14 / Chapter 3.4 --- Coordinate Transformation with Gravity Compensation --- p.15 / Chapter 3.4.1 --- Coordinate Transformation --- p.16 / Chapter 3.4.2 --- Attitude Determination --- p.18 / Chapter 3.4.3 --- Gravity Compensation --- p.19 / Chapter 3.5 --- Summary --- p.20 / Chapter 4 --- Zero Velocity Compensation --- p.21 / Chapter 4.1 --- Introduction --- p.21 / Chapter 4.2 --- Algorithm Description --- p.21 / Chapter 4.2.1 --- Stroke Segmentation --- p.22 / Chapter 4.2.2 --- Zero Velocity Compensation (ZVC) --- p.22 / Chapter 4.3 --- Experimental Results and Discussion --- p.23 / Chapter 4.4 --- Summary --- p.24 / Chapter 5 --- Kalman Filtering --- p.28 / Chapter 5.1 --- Introduction --- p.28 / Chapter 5.2 --- Summary of Kalman filtering algorithm --- p.28 / Chapter 5.2.1 --- System Model --- p.28 / Chapter 5.2.2 --- Initialization --- p.29 / Chapter 5.2.3 --- Time Update --- p.32 / Chapter 5.2.4 --- Measurement Update --- p.33 / Chapter 5.2.5 --- Stroke Segmentation --- p.34 / Chapter 5.3 --- Summary --- p.34 / Chapter 6 --- Error Compensation from Position Feedback --- p.35 / Chapter 6.1 --- Introduction --- p.35 / Chapter 6.2 --- Global Positioning System (GPS) --- p.35 / Chapter 6.3 --- Zero z-axis Kalman Filtering --- p.36 / Chapter 6.3.1 --- Algorithm Implementation --- p.36 / Chapter 6.3.2 --- Experimental Results and Discussion --- p.40 / Chapter 6.4 --- Combined Electromagnetic Resonance (EMR) Position Detection Board and μlMU --- p.43 / Chapter 6.4.1 --- EMR Position Detection System --- p.43 / Chapter 6.4.2 --- A Combined Scheme --- p.44 / Chapter 6.4.3 --- Algorithm Implementation --- p.46 / Chapter 6.4.4 --- Synchronization --- p.50 / Chapter 6.4.5 --- Experimental Results and Discussion --- p.50 / Chapter 6.5 --- Summary --- p.54 / Chapter 7 --- Conclusion --- p.55 / Chapter 7.1 --- Future Work --- p.56 / Chapter 7.1.1 --- Improvement in the μlMU --- p.56 / Chapter 7.1.2 --- Combined Camera Optical Tracking and μlMU --- p.57 / Chapter 7.2 --- Concluding Remarks --- p.58 / Chapter A --- Derivation of Kalman Filtering Algorithm --- p.59 / Chapter A.1 --- Introduction --- p.59 / Chapter A.2 --- Derivation of a Priori State Estimation Equation --- p.60 / Chapter A.3 --- Derivation of a Posteriori State Estimation Equation --- p.60 / Chapter A.4 --- Derivation of a Priori Error Covariance Matrix --- p.61 / Chapter A.5 --- Derivation of the Optimal Kalman Gain --- p.62 / Chapter A.6 --- Derivation of a Posteriori Error Covariance Matrix --- p.63 / Chapter B --- Derivation of Process Noise Covariance Matrix --- p.64 / Bibliography --- p.66 / Publications --- p.69

Dong, Zhuxin. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 77-80). / Abstracts in English and Chinese. / Abstract --- p.ii / 摘要 --- p.iii / Acknowledgements --- p.iv / Table of Contents --- p.v / List of Figures --- p.vii / List of Tables --- p.ix / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Architecture of UDWI --- p.3 / Chapter 1.2 --- Background of IMU Sensor Calibration --- p.5 / Chapter 1.3 --- Organization --- p.7 / Chapter Chapter 2 --- 2D Motion Calibration --- p.10 / Chapter 2.1 --- Experimental Platform --- p.10 / Chapter 2.1.1 --- Transparent Table --- p.10 / Chapter 2.2 --- Matching Algorithm --- p.13 / Chapter 2.2.1 --- Motion Analysis --- p.13 / Chapter 2.2.2 --- Core Algorithm and Matching Criterion --- p.14 / Chapter 2.3 --- Usage of High Speed Camera --- p.17 / Chapter 2.4 --- Functions Realized --- p.17 / Chapter Chapter 3 --- Usage of Camera Calibration --- p.21 / Chapter 3.1 --- Introduction to Camera Calibration --- p.21 / Chapter 3.1.1 --- Related Coordinate Frames --- p.21 / Chapter 3.1.2 --- Pin-Hole Model --- p.24 / Chapter 3.2 --- Calibration for Nonlinear Model --- p.27 / Chapter 3.3 --- Implementation of Process to Calibrate Camera --- p.28 / Chapter 3.3.1 --- Image Capture --- p.28 / Chapter 3.3.2 --- Define World Frame and Extract Corners --- p.28 / Chapter 3.3.3 --- Main Calibration --- p.30 / Chapter 3.4 --- Calibration Results of High Speed Camera --- p.33 / Chapter 3.4.1 --- Lens Selection --- p.33 / Chapter 3.4.2 --- Property of High Speed Camera --- p.34 / Chapter Chapter 4 --- 3D Attitude Calibration --- p.36 / Chapter 4.1 --- The Necessity of Attitude Calibration --- p.36 / Chapter 4.2 --- Stereo Vision and 3D Reconstruction --- p.37 / Chapter 4.2.1 --- Physical Meaning and Mathematical Model Proof --- p.37 / Chapter 4.2.2 --- 3D Point Reconstruction --- p.38 / Chapter 4.3 --- Example of 3D Point Reconstruction --- p.40 / Chapter 4.4 --- Idea of Attitude Calibration --- p.42 / Chapter Chapter 5 --- Experimental Results --- p.45 / Chapter 5.1 --- Calculation of Proportional Parameter --- p.45 / Chapter 5.2 --- Accuracy Test of Stroke Reconstruction --- p.46 / Chapter 5.3 --- Writing Experiments of 26 Letters --- p.47 / Chapter 5.3.1 --- Experimental Results of Letter b --- p.48 / Chapter 5.3.2 --- Experimental Results of Letter n with ZVC --- p.51 / Chapter 5.3.3 --- Experimental Results of Letter u --- p.54 / Chapter 5.4 --- Writing of Single Letter s - Multiple Tests --- p.56 / Chapter 5.5 --- Analysis on Resolution Property of Current Vision Algorithm --- p.58 / Chapter 5.5.1 --- Resolution of Current Algorithm --- p.58 / Chapter 5.5.2 --- Tests with Various Filters --- p.59 / Chapter 5.6 --- Calculation of Static Attitude --- p.61 / Chapter Chapter 6 --- Future Work --- p.64 / Chapter 6.1 --- Another Multiple Tests of Letter k --- p.64 / Chapter 6.2 --- Letter Recognition Based on Neural Networks Classification --- p.66 / Chapter Chapter 7 --- Conclusion --- p.69 / Chapter 7.1 --- Calibration ofMAG-μlMU Sensors --- p.69 / Chapter 7.2 --- Calibration of Accelerometers --- p.70 / Chapter 7.3 --- Calibration of Attitude --- p.70 / Chapter 7.4 --- Future Work --- p.71 / Appendix A The Experimental Results of Writing English Letters --- p.72

The high cost of experimentation and product development in the field of microelectromechanical systems (MEMS) has led to a greater emphasis on simulation-based design for increasing first-pass design success and reliability. The use of compliant or flexible mechanisms can help eliminate friction, wear, and backlash, but compliant MEMS are sensitive to variations in material properties and geometry. This dissertation proposes approaches for design stage uncertainty analysis, model validation, and robust optimization of nonlinear compliant MEMS to account for critical process uncertainties including residual stress, layer thicknesses, edge bias, and material stiffness. Methods for simulating and mitigating the effects of non-idealities such joint clearances, semi-rigid supports, non-ideal loading, and asymmetry are also presented. Approaches are demonstrated and experimentally validated using bistable micromechanisms and thermal microactuators as examples.

The purpose of this research is to develop MEMS based acoustic emission sensors for structural health monitoring. Acoustic emission (AE) is a well-established nondestructive testing technique that is typically used to monitor for fatigue cracks in structures, leaks in pressurized systems, damages in composite materials or impacts. This technology can offer a precise evaluation of structural conditions and allow identification of imminent failures or minor failures that can be addressed by planned maintenances routines. AE causes a burst of ultrasonic energy that is measured as high frequency surface vibrations (30 kHz to 1 MHz) generated by transient elastic waves that are typically emitted from growing cracks at the interior of the structure. The AE sensor marketplace is currently dominated by bulky and expensive piezoelectric transducers that are wired to massive multichannel data acquisition systems. These systems are complex to operate with the need of signal conditioning units and near proximity pre-amplifiers for each sensor that demands a fairly complicated wiring requirements. Furthermore, due to the high prices of conventional AE sensors and associated instrumentation, and the current requirements in sensor volumes for smart transportation infrastructure, it is undeniable that new AE technology is required for affordable structural health monitoring. The new AE technology must deliver comparable performance at one or two orders of magnitude lower cost, size and weight. MEMS acoustic emission (AE) sensors technology has the potential to resolve several of these traditional sensor’s shortcomings with the advantage of possible integration of on-chip preamplifier while allowing substantially cost reduction due to the batch processing nature of MEMS technology. This study will focus on filling some of the major existing gaps between current developments in MEMS acoustic emission sensors and commercial piezoelectric sensors, such as sensor size, signal-to-noise ratio (SNR), cost and the possibility to conform to sharply curved surfaces. Basically, it is proposed to develop a new class of micro-machined AE sensors or sensor arrays through strategic design of capacitive and piezoelectric MEMS sensors, which will focus on optimizing the following performance aspects: Creating geometric designs to manipulate the sensor resonant frequency and to optimize Q factor under atmospheric pressure and ambient environment. Developing a strategic selection of materials according to its acoustic impedance as insulator, structure and backing material. Developing strategies to improve the signal to noise ratio SNR with and without integrated amplification/signal processing. Performing a comparison between MEMS and commercial piezoelectric sensors.

No description available.

In this thesis, the development of a novel electro-thermally actuated bi-stable out-of-plane two way actuated buckled micro-bridge for a potential application in optical switching is presented. The actuator consists of a bridge supported by 'legs' and springs at its four corners. The springs and the bridge are made of a tri-layer structure comprising of 2.5??m thick low-stress PECVD oxide, 1??m thick high-stress PECVD oxide and 2??m thick heavily phosphorus doped silicon. The legs, on the other hand, are 2??m thick single layer heavily phosphorus doped silicon. Both legs and springs provide elastically constrained boundary conditions at the supporting ends, without of which important features of the micro-bridge actuator could not have been achieved. This microbridge actuator is designed, simulated using ANSYS, fabricated and tested. The results from the testing have shown a good agreement with analytical prediction and ANSYS simulation. The actuator demonstrated bi-stability, two-way actuation and 31??m out-of-plane movement between the two-states using low voltage drive. Buckled shape model, design method for bi-stability and thermo-mechanical model are developed and employed in the design of the micro-bridge. These models are compared with Finite Element (FE) based ANSYS simulation and measurements from the fabricated micro-bridge and have shown a good agreement. In order to demonstrate the potential application of this actuator to optical switching, ANSYS simulation studies have been performed on a micro-mirror integrated with the micro-bridge actuator. From these studies, the optimum micro-mirror size that is appropriate for the integration has been obtained. This optimal mirror size ensures the important features of the actuator. Mirror fabrication experiments in (110) wafer have been carried out to find out the appropriate compensation mask size for a given etch depth and the suitable wafer thickness that can be used to fabricate the integrated system.