Orientador: João Antonio Pereira / Banca: Luiz de Paula do Nascimento / Banca: Roberto Gil Annes da Silva / Resumo: Esse trabalho discute o uso dos materiais piezelétricos, mais especificamente, o Polyvinylidene Fluoride (PVDF) e o Lead Zirconate Titatane (PZT) na análise modal experimental (AME) de estruturas mecânicas. Materiais piezelétricos, também chamados de materiais inteligentes, têm se consolidado como uma nova tecnologia que mostra um grande potencial de aplicação em diferentes áreas da engenharia. Esse tipo de material exibe um acoplamento entre multi-domínios físicos, como por exemplo o acoplamento eletro-mecânico, o térmo-magnético, etc. O acoplamento eletro-mecânico produz um deslocamento elétrico quando o material é sujeito a uma tensão mecânica (efeito direto) e um deformação mecânica quando esse material é submetido a um campo elétrico (efeito inverso). Assim, principalmente por conta desses efeitos, seu uso no campo da análise modal experimental torna-se uma interessante questão a ser investigada. A incorporação de novas tecnologias nos testes estruturais pode agregar novos conhecimentos e avanços tanto na análise modal baseada na relação entrada-saída da estrutura, quanto na mais recente técnica, a análise modal baseada apenas na resposta das mesmas. Os conceitos teóricos para o desenvolvimento são apresentados e discutidos neste trabalho, onde é mostrada a análise modal de uma viga utilizando tanto sensores e atuadores convencionais quanto os produzidos com materiais inteligentes. Os testes de análise modal da viga foram feitos utilizando diferentes combinações de sensores e atuadores e isso pode mostrar as diferenças da estimativa de modos utilizando materiais piezelétricos. Também é apresentada a formulação da relação entre os modos em deslocamento e os modos com diferença de inclinação obtidos com materiais piezelétricos e, finalmente, uma comparação dos resultados obtidos pelas diferentes técnicas. Os testes apresentados mostram... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This work discusses the use of piezoelectric materials, more specifically, Polyvinylidene Fluoride (PVDF) and Lead Zirconate Titanate (PZT) for experimental modal analysis (EMA) of mechanical structures. Piezoelectric materials also called smart materials have becoming a consolidated new technology that shows a large potential of application for different engineering areas. These materials exhibit a multi physics domain field coupling like mechanical and electrical coupling domains, thermal and magnetic coupling and etc. The electro-mechanical coupling domains of the material produces an electric displacement when the material is subject to a mechanical stress (direct-effect) and a mechanical strain when the material is submitted to an electric field (inverse effect). So, mainly due to these effects, the use in the experimental modal analysis field appears to be an interesting issue to be investigated. The incorporation of this new technology in the structural tests might aggregate new acknowledgments and advances in the well consolidated input-output based modal analysis techniques as well as in the more recent output only-based modal analysis. This work aims to present some contribution in this area by using piezoelectric sensors, instead of the conventional ones like accelerometers for modal analysis of mechanical structures. The theoretical concepts and background for the developing of the work are presented and discussed, it is also presented the modal analysis of a beam like structure using conventional sensors/actuators and piezoelectric materials. The modal analysis tests of the beam are conducted using different kinds of sensors/actuator and they give some insight of the difference of the estimated modes shapes by using piezoelectric materials. It is also presented a formulation that shows the relation between... (Complete abstract click electronic access below) / Mestre

Os objetivos deste trabalho foram estudar, desenvolver e avaliar filmes para a captação de vapores de benzeno e amônia, tornando possível a detecção e quantificação destas substâncias no ar atmosférico, utilizando sensores piezelétricos de quartzo. Dispositivos piezelétricos destes cristais são hoje de grande importância em Química Analítica, possuindo inúmeras aplicações (meio gasoso e em solução), uma vez que se encontram muitos trabalhos no campo da eletroanalítica, enzimologia, imunoquímica, análise de alimentos, análises clínicas e em análises ambientais. O princípio do método baseia-se no fato de que o cristal de quartzo, sob um campo elétrico alternado, vibra com uma freqüência bem definida. Ao se depositar uma pequena massa de material na superfície do cristal (eletrodo), ocorre uma queda proporcional da freqüência de vibração. Depositando-se um filme (coating) que tenha afinidade pela substância que se quer detectar e quantificar, tem-se uma microbalança. À medida que o poluente passa pelo cristal ocorre a sorção do mesmo. Com o aumento da massa, a freqüência de vibração do cristal diminui proporcionalmente, sendo possível a construção de uma curva analítica, o que permite a quantificação do poluente em níveis da ordem de parte por milhão (ppm) ou mesmo parte por bilhão (ppb). No início dos estudos, várias substâncias (individualmente ou misturadas) foram investigadas como possíveis substratos captores (filmes) para detecção de benzeno e amônia. Entre elas, diferentes fases estacionárias viscosas utilizadas em cromatografia gasosa, além de alguns silicones, glicóis, ácidos orgânicos, zeólitas, complexos de metais de transição e até porfirinas. Para a detecção e quantificação de benzeno, em níveis da ordem de 10 ppm (32 mg m-3), dentre as muitas substâncias investigadas, até o presente momento, nenhuma apresentou resultados satisfatórios para a montagem de método analítico. Para a detecção e quantificação de amônia, encontrou-se que uma mistura de 50 ?L de solução de ácido glicólico em THEED (3:4 m/m) com 25 ?L de solução saturada de ácido tânico em acetona, mostrou-se a mais promissora. Nas etapas seguintes, passou-se às investigações para otimização das condições experimentais. Foram estudados, então, a melhor vazão de trabalho, os efeitos da quantidade de filme depositado sobre o cristal, efeito da temperatura, reversibilidade, entre outros. Todas as medidas foram realizadas para quatro tempos diferentes de exposição do cristal ao poluente (30 segundos, 1, 2 e 3 minutos). A quantidade de filme considerada ideal foi de 133 g, correspondendo a uma variação de freqüência de aproximadamente 67 KHz. Valores maiores, além de diminuírem a sensibilidade, geralmente causam parada das oscilações enquanto o poluente passa pelo cristal (aumento excessivo de massa), sendo que valores menores de massa provocam diminuição de sensibilidade. A melhor vazão de trabalho encontrada está na faixa de 80 a 100 mL min-1. Temperaturas entre 15ºC e 35ºC não apresentaram efeitos significativos sobre a sensibilidade do detector, ocorrendo uma diminuição da mesma em temperaturas acima deste limite. O sensor apresentou queda de freqüência linear (r = 0,999 para tempos de exposição de 30 segundos e 1 minuto, e r = 0,988 para tempos de exposição de 2 e 3 minutos) no intervalo de concentração estudado (2 à 10 ppm). Alguns possíveis interferentes foram investigados, entre eles CO, CO2, H2S, NO2 e ar atmosférico, sendo que, apenas o NO2 interferiu nas análises. Portanto, deve estar ausente do ar analisado ou deve ser retirado por algum captor específico estrategicamente inserido na linha de entrada. Estudos sobre o \"envelhecimento\"da película após preparo, mostraram que nenhum efeito considerável foi observado quanto à captação do poluente, após dois meses . Nos estudos de reversibilidade, o sensor mostrou-se irreversível, o que nos impediu de verificar o tempo de vida de uma mesma película para vários ciclos consecutivos. Contudo, este fato é compensado pela elevada sensibilidade e pelo curto tempo gasto na análise, ficando demonstrado sua grande potencialidade na detecção e quantificação de amônia no ar. / The objective of this work was to study, develop and evaluate coatings for detecting benzene and ammonia in atmospheric air, by using a piezoelectric quartz sensor. Nowadays, piezoelectric quartz sensors are very important in Analytical Chemistry due to their numerous aplications (in gaseous fase or in solution). This method is based on the fact that the quartz crystal when placed under an alternated electric field, vibrates with a well known frequency. When a very low mass of substance is deposited on the crystal surface (electrode) a proportional decrease in the vibrational frequency occurs. This coating must have affinity for the substance we wish to detect and quantify. The sorption of the pollutant occurs as it is passes through the crystal. Increased mass leads to decreased vibrational frequency in a proportional way, so it is possible to build an analytical curve and quantify the pollutant in levels of part per million (ppm) and part per billion (ppb). Many substances (individually or mixed) were investigated as possible coatings for detection of benzene and ammonia detection, such as different chromatography viscous stationary phases, glycols, some organic acids, zeolites, transition metal complexes and porphyrins. For benzene detection and quantification at the level of 10 ppm (32 mg m-3), none of the investigated substances presented satisfactory results. For ammonia detection and quantification a mixture of 50 ?L of Glycolic Acid in THEED solution (3:4 w/w) and 25 ?L of Tannic Acid in acetone solution was the most promising one. The optimization of the experimental conditions found 133 ?g as the ideal coating mass to be deposited on the crystal surface. A working flow of ix 80 to 100 mL min-1and a working temperature in the 15ºC to 35ºC range (59ºF to 95ºF) were found to be ideal. In the studied concentration range, the sensor presented linear decrease in frequency. Some possible interfering substances were investigated (CO, CO2, H2S, NO2 and atmospheric air) and only NO2 showed some interference. Although the sensor showed to be irreversible, it is also very sensitive and can therefore be used to detect and quantify ammonia.

Hard disk drives (HDDs) are the most important information storage devices for computers. Positioning precision is crucial to today's increasingly high-speed, high-capacity, high data density, and miniaturized HDDs. Therefore, the demand for higher bandwidth servo systems that can quickly and precisely position the read/write head on a high track density becomes more pressing. Recently, the idea of applying dual-stage actuators to track servo systems has been studied. The push-pull piezoelectrically actuated devices have been developed as micro actuators for fine and fast positioning, while the voice coil motor functions as a large but coarse seeking. However, the current dual-stage actuator design uses piezoelectric patches only without passive damping. In this thesis, a dual-stage servo system using enhanced active-passive hybrid piezoelectric actuators is proposed. The actuators improve the existing dual-stage actuators for higher positioning precision and better shock resistance, due to the incorporation of passive damping in the design. The main aim is to develop this hybrid servo system not only to increase the speed of track seeking but also to improve precision of track following servos in HDDs. A new piezoelectrically actuated suspension with passive damping is designed and fabricated for precision positioning of the head while reducing undesirable vibrations. In order to evaluate positioning and track following performances for the dual-stage track servo systems, tasks carried out in the thesis are: (1) to investigate the damping abilities and transmissibilities of the active-passive hybrid micro actuators; (2) to investigate the shock resistance of the dual-stage piezoelectric actuators with passive damping; (3) to implement the synthesized active-passive suspension with enhanced piezoelectric actuators using a composite nonlinear feedback controller. / Chan, Kwong Wah. / "December 2006." / Source: Dissertation Abstracts International, Volume: 68-08, Section: B, page: 5512. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (p. 84-90). / 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.

Background: Current research, surrounding motor laterality at a population level in horses, indicates that in order to stand with the left forelimb in advance of the other, it is achieved by taking a greater amount of steps with the left foreleg than the right foreleg (McGreevy & Thomson 2006; McGreevy et al. 2007); suggesting that pedometers could effectively estimate asymmetry of forelimb locomotion in grazing horses. This novel method of detecting forelimb preference also reduces the likelihood of operator influence and provides an inexpensive objective measure of vertical movement which has the advantage of scoring large sample sizes, avoids single-day anomalies by recording over multiple days and overcomes logistical challenges (Vincent & Sidman 2003; Chan et al. 2005; Silva et al. 2010; Warren-Smith & McGreevy 2010). However in order to determine the reliability and validity of this novel measure the relationship between pedometer data and those derived from direct observation will first need to be assessed (Warren-Smith and McGreevy 2010). Objectives: To determine: (1) if pedometers accurately record equine steps at walk and trot, when compared to video analysis, (2) if alternative positioning of these pedometers affected the accuracy of step detection when compared to video analysis. Method: Five horses each wearing a Yamax Digiwalk SW-200 (spring lever arm pedometer) and a Yamax Power Walker PW-610/611 (piezoelectric pedometer) positioned on the left foreleg (LF), left scapular (LS), chest (C), right scapular (RS) and right foreleg (RF) walked and trotted on a 20m circle 10 times on each rein to yield 100 results for each gait. Video recorded by GoPro Hero 3 Black edition camera positioned on the girth facing the forefeet using the following settings: 180 degree field of view, 720p, 120fps. Both visual and audio data were captured and recorded. Results: Kruskal-Wallis Test on the deviation from actual number of steps per unit for each type of pedometer and the position of the pedometer compared to the actual number of steps taken by both forelegs determined that there is a significant difference (H1= 340.31; P < 0.0001) between readings in walk and also in trot (H1 = 483.49; P < 0.0001). A further Kruskal-Wallis Test on the deviation from actual number of steps per unit for each type of pedometer and the position of the pedometer compared to the actual number of steps taken by individual forelegs determined that there is a significant difference (H = 403.36; p < 0.0001) at walk and also at trot (H = 477.10; p < 0.0001). Conclusion: In summary, the analysis of the pedometer data compared to video analysis indicate that pedometers are not useful for scoring forelimb movements in horses at walk and trot, regardless of positioning.

There is a critical need for inspection and condition monitoring of high temperature critical components such as pipelines and welds in electrical power generation and other plants operating at temperatures as high as 580°C. The high temperatures and pressures experienced in these pipelines, particularly for ageing plants lead to creep, fatigue and corrosion type defects. Safety of these plants is of paramount importance, and regular maintenance is carried out during planned outages at ambient temperatures. Ultrasonic non-destructive testing can be used to detect defects in the weld at ambient temperatures. However, at high operational temperatures, this technique cannot be applied due to the lack of high temperature transducers. This research has achieved significant advances towards enabling ultrasonic inspection and condition monitoring of high temperature critical points, by developing an ultrasonic transducer around an advanced piezoelectric single crystal material, called Gallium Orthophosphate (GaPO4), which can operate at the required temperature of 580°C. Based on its reported piezoelectric and other properties, and its commercial availability, GaPO4 was chosen as a candidate active material for application in a prototype high temperature transducer. In a series of confidence building tests with the selected piezoelectric material (electrical characterisation via the impedance method), it has been demonstrated that the GaPO4 piezoelectric elements are stable when subjected to 580°C for more than 600 hours. Ultrasonic thickness gauging has shown that GaPO4 works as a functional transducer generating and receiving ultrasound waves at 580°C for at least 360 hours. Furthermore, the sensitivity of the GaPO4 transducer to detect defects with simple geometry was successfully tested through measurements on steel blocks containing artificial defects (side-drilled holes) up to the same high temperatures. Based on the characterisation results from the impedance and ultrasonic measurements, a prototype ultrasonic transducer for operation at high temperatures has been designed and manufactured. The new ultrasonic transducer was tested in a laboratory environment using a steel calibration block, high temperature couplant, SONO 1100, and an electric furnace. In the range from ambient temperatures up to the target of 580°C, the ultrasonic transducer kept a signal-to-noise (SNR) level sufficiently high, above the threshold of 6 dB, which is high enough for practical non-destructive testing and condition monitoring.

Este trabalho visa o desenvolvimento de um processo de fabricação para a produção de pequenos lotes de transdutores piezelétricos de ultrassom. O comportamento destes transdutores é estudado através de modelos matemáticos e verificações experimentais, com o objetivo de obter especificações de projeto para seleção de cerâmicas piezelétricas, dimensionamento da camada de retaguarda e da camada de casamento de impedância acústica. Utilizando as equações constitutivas dos materiais piezelétricos e a solução da equação de onda, o transdutor é modelado como um produto de matrizes, sendo cada matriz correspondente a uma camada do transdutor. As relações entre os parâmetros de entrada e saída das camadas analisadas do modelo são utilizadas para determinar as funções características de interesse no projeto de transdutores específicos. O processo de fabricação foi desenvolvido visando diminuir o tempo de montagem e aumentar a confiabilidade de funcionamento, melhorando a qualidade de soldagem das conexões elétricas, da colagem e da vedação, e aumentando a precisão de posicionamento dos componentes do transdutor. Assim objetiva-se obter lotes homogêneos em relação às especificações de projeto, com repetitividade no comportamento dos transdutores produzidos. Utilizando o processo de fabricação desenvolvido, um lote de 133 transdutores de 5 MHz foi produzido, com cerâmicas piezelétricas de 10 mm de diâmetro para suportar pressões de até 500 atm. Os transdutores foram testados individualmente e os resultados mostram uma grande repetitividade do processo desenvolvido. / This work aims the development of a manufacturing process for the production of small batches of piezoelectric ultrasonic transducers. The behavior of these transducers is studied by means of mathematical models and experimental tests, in order to get the design specifications for the piezoelectric ceramics selection, scaling the backing and matching layers. Using the constitutive equations of piezoelectric materials and the wave equation solution, the transducer is modeled as a product of matrices, each matrix corresponding to a layer of the transducer. The relationship between input and output parameters of transducer layers is used to determine the characteristic functions of specific transducers. The manufacturing process was developed for small production batches of transducers and aim decrease assembly time and increase reliability operation, improving the quality of welding of electrical connections, bond and seal, and increasing the positioning accuracy of the transducer components. So the objective is to obtain homogeneous batches regarding to design specifications, with repeatability in the behavior of the manufactured transducers. Using the process manufacturing developed, a 133-transducers batch of 5 MHz was produced, with 10 mm diameter piezoelectric ceramics, to withstand pressures up to 500 atm. The transducers are individually tested and the results show a high repeatability of the manufacturing process.

Desde o final da década de 1980 até os dias atuais a utilização de materiais inteligentes em sistemas de controle de vibrações e em problemas de conversão de energia mecânica em energia elétrica tem sido amplamente investigada. Entre os materiais inteligentes destacamos os piezelétricos, apresentando acoplamento entre os domínios elétrico e mecânico. Em casos de controle passivo de vibrações utiliza-se o efeito piezelétrico direto e a energia de vibração é dissipada em um circuito elétrico passivo. Apesar de não utilizarem uma fonte externa de energia, a faixa de frequências onde o controlador passivo tem bom desempenho é limitada em relação aos controladores ativos. Em problemas de controle ativo de vibrações o efeito piezelétrico inverso é utilizado. Neste caso, uma tensão elétrica de controle é aplicada aos piezelétricos para a atenuação de vibrações. Os sistemas híbridos de controle (ativo-passivo) associam circuitos passivos e uma fonte de tensão elétrica. Nesse caso, os efeitos piezelétricos direto e inverso são utilizados simultaneamente. Espera-se que a parte ativa do sistema híbrido necessite de menor potência elétrica de atuação (se comparado com um controlador ativo) além do sistema híbrido proporcionar melhor resposta estrutural que o sistema passivo isoladamente. Entretanto, os controladores ativos e híbridos apresentam desvantagens relacionadas com complexidades de uma lei de controle, necessidade de equipamentos externos e podem exigir elevada potência de atuação. Os controladores semi-passivos surgiram como uma alternativa aos pontos negativos dos controladores passivos, ativos e híbridos. Uma técnica semi-passiva chamada SSD (synchronized switch damping) consiste no chaveamento do material piezelétrico entre a condição de circuito aberto e a condição de curto-circuito (SSDS) ou a uma indutância (SSDI), em momentos específicos da vibração da estrutura. Em geral, a conversão eletromecânica de energia é amplificada assim como o efeito shunt damping. Dessa forma, os circuitos semi-passivos, assim como os passivos, têm sido utilizados tanto como controladores de vibração quanto em problemas de coleta piezelétrica de energia. O objetivo deste trabalho é avaliar o desempenho de controladores piezelétricos passivos, semi-passivos, ativos e híbridos na atenuação de vibrações e também em problemas aeroelásticos. O modelo piezoaeroelástico é obtido com um modelo por elementos finitos (placa de Kirchhoff) eletromecanicamente acoplado que associado a um modelo aerodinâmico não-estacionário (método de malha de dipolos) resulta um modelo piezoaeroelástico. Casos de excitação harmônica de base, entrada impulsiva e também condição de flutter são estudados. / From the late 1980s until the present date, the use of smart materials as actuators in vibration control systems and as conversers of mechanical energy into electricity has been widely investigated. Among these smart materials, the piezoelectric ones stand out, presenting a coupling between the electrical and mechanical domain. In passive vibration control, the direct piezoelectric effect is used and vibration energy is dissipated (or harvested) in a passive circuit. Although no external power source is required, the frequency bandwidth in which passive controllers have good performance is limited when compared to active controllers. In active vibration control problems, the inverse piezoelectric effect is used. In this work, a voltage source is applied on the piezoceramic patches in order to attenuate vibration. Hybrid (active-passive) vibration controllers combine passive shunt circuits with the voltage source. In this case, the direct and inverse piezoelectric effects are used simultaneously. It is expected that the active part of the hybrid system will require less energy (when compared to an active controller) and a better structural response will be obtained than the purely passive system. Nevertheless, the active and hybrid controllers present disadvantages such as complexity of a control law, require external equipment and potentially require large amounts of energy. The semi-passive controllers are a recent alternative to the drawbacks of passive, active and hybrid controllers. A semi-passive technique called SSD (synchronized switch damping) consists of using an electronic switch that the piezoelectric element is briefly switched to an electrical shunt-circuit that can be a simple short-circuit (SSDS), or a small inductance (SSDI) at specific times in the structure\'s vibration cycle (Mohammadi, 2008). In general, the electromechanical energy conversion is enhanced as well as the shunt effect damping. Therefore, the switching techniques, as well as the passive circuits, have been used both in vibration control problems and in piezoelectric energy harvesting problems. The goal of this work is to assess the performance of passive, semi-passive, active and hybrid piezoelectric controllers to attenuate vibration in aeroelastic problems. The aeroelastic model is obtained by combining an electromechanically coupled finite element model (Kirchhoff\'s plate) with an unsteady aerodynamic models (the doublet-lattice method and Roger\'s model). The case studies are carried out on an elastic wing response to a base excitation, impulse force, and the flutter condition.

This thesis describes the design of a DSP based air detector system to prevent air embolism during Hemodialysis, which is a treatment option for kidney failure disease. Hemodialysis consists of removing blood from the body, filtering and treating the blood to remove toxic substances such as wastes and fluids, reestablishing proper chemical levels in the blood and returning the processed blood to the body. The functions of hemodialysis are performed through the use of a dialyzer, which is also known as an artificial kidney. During hemodialysis small air bubbles may infiltrate the tubing used during the therapy and combine to form larger air bubbles that are harmful to the patient. If an air bubble is large enough and enters the patient's circulatory system, the blood flow can be blocked and the patient can die by embolism. Most of the hemodialysis instruments in use today are equipped with air detection systems, which are based on analog design and digital microcontroll ers. This thesis presents a design method based strictly on DSP technology. The Motorola DSP 56824EVM was considered suitable for this biomedical application since its performance parameters include high-speed, multi-signal control capability, reliability and stability. These performance parameters are considered to be the most important when designing biomedical instruments dealing with human beings' life and safety. The objective of this research was the development and implementation of a DSP algorithm for the detection and measurement of the sizes of air bubbles in a fluid. In addition the algorithm had to possess the capability, when appropriate, to initiate protective and awareness measures such as triggering a tube clamp as well as activating visual and audio alarms. The air detection was accomplished by means of a commercial air detector module, which was based on piezo ceramic and ultrasound sensing. The function of the tubing clamp was to stop the fluid flow in the tubing and prevent an air bubble from entering the patient's circulatory system. A secondary goal of this research was to exploit the capability of the DSP 56824EVM and demonstrate its suitability for biomedical applications.

On-chip vibrating MEMS resonators with high frequency-Q product on par with that of the off-chip quartz crystals have attracted lots of attention from both academia and industry for applications on sensing, signal processing, and wireless communication. Up to now, several approaches for monolithic integration of MEMS and transistors have been demonstrated. Vibrating micromechanical disk resonators which utilize electroplated nickel as the structural material along with either a solid-gap high-k dielectric capacitive transducer or a piezoelectric transducer have great potential to offer unprecedented performance and capability of seamless integration with integrated circuits. Despite the frequency drift problems encountered in early attempts to use nickel as a structural material in MEMS gyroscopes, this low temperature nickel electroplating technology is amenable to post-transistor planar integration. The nickel microstructure is formed through the photoresist molding and electroplating process which enables the microstructure to have extremely high aspect ratio while retaining the overall process temperature under 60ºC. This temperature is low enough to allow the RF MEMS devices to be fabricated directly on top of foundry IC chips, thus enabling post-transistor monolithic integration with minimum parasitics. In addition, the electroplating setup for nickel deposition can be much cheaper as compared to the other deposition facilities (e.g., PVD, CVD, etc). However, as the dimensions of the resonators are shrunk to µm range, several issues have come forth such as higher motional resistance and lower power handling ability. In order to reduce the motional resistance, high permittivity material is employed to form a solid capacitive gap instead of an air gap. As compared to the air gap, ease of the process, better stability and elimination of the particles are the additional benefits of using the solid gap. Therefore, an ultra-thin high-k dielectric layer with atomically controlled thickness down to sub-nm range can be deposited under 100ºC on the vertical sidewall of the device structure by using ALD processing technology. This enhances the efficiency of the capacitive transducer enormously, thus reducing the characteristic motional resistance of the device. This research project explored the idea of applying low temperature process of electroplated nickel and high-k solid-gap as well as partially-filled air-gap capacitive transducers. To further reduce the motional impedance, electromechanically-coupled resonator arrays have been implemented. Furthermore, the linearity of solid-gap versus partially-filled air-gap resonators has been studied through a modeling approach for RF applications. In the meanwhile, this work also investigated electroplated nickel as a structural material for piezoelectrically-transduced resonators to demonstrate piezoelectric-on-nickel resonators with low temperature process. The thin film piezoelectric resonators can achieve high resonance frequency when increasing the piezoelectric film thickness and scaling down the device size. However, the sputtered piezoelectric films have very low deposition rate which limits the thickness to a couple of microns or less. Moreover, the yield of piezoelectric resonators is restricted after the releasing process since the stress of the thin films usually causes the structural layer to buckle or fracture. Thus, the development of piezoelectric-on-substrate resonators is an alternative solution to resolve the aforementioned issues. The previous work has been done by using single crystal silicon or nano-crystalline diamond (NCD) as resonator structural materials due to their high acoustic velocity and low loss. However, the deposition temperature for thin film silicon and diamond is too high to be allowable thermal budget of ICs. Therefore, electroplated nickel is also a reasonable substitute for silicon and diamond substrates while realizing high frequency and moderate Q. Furthermore, it is observed that a localized annealing process through Joule heating can be adopted to significantly improve the effective mechanical quality factor for the ZnO-on-nickel resonators. This work successfully demonstrated the ZnO-on-nickel piezoelectrically-actuated MEMS resonators and resonator arrays with frequencies ranging from a few megahertz to 1.5 GHz by using IC compatible low temperature process.

This thesis represents the work that has been done by the author during his Master of Engineering Science candidature in the area of vibration control of flexible structures at the School of Mechanical Engineering, The University of Adelaide, between March 2003 and June 2004. The aim of this research is to further extend the application of the Spatial Control Approach for two-dimensional flexible structures for attenuating global structural vibration with the possible implication of reduction in noise radiation. The research was concentrated on a simply supported thin flexible plate, using piezoelectric ceramic materials as actuators and sensors. In this work, active controllers were designed for the purpose of controlling only the first five vibration modes (0-500Hz) of the plate. A spatial controller was designed to minimize the total energy of the spatially distributed signal, which is reflected by the spatial H2 norm of the transfer function from the disturbance signal to the vibration output at every point over the plate. This approach ensures the vibration contributed by all the in bandwidth (0-500 Hz) vibration modes is minimized, and hence is capable of minimizing vibration throughout the entire plate. Within the control framework, two cases were considered here; the case when the prior knowledge of the incoming disturbance in terms of reference signal is vailable and the case when it is not available. For the case when the reference signal is available, spatial feedforward controller was designed; whereas for the case when the reference signal is not available, spatial feedback controller was designed to attenuate the global disturbance. The effectiveness of spatial controllers was then compared with that of the standard point-wise controllers numerically and experimentally. The experimental results were found to reflect the numerical results, and the results demonstrated that spatial controllers are able to reduce the energy transfer from the disturbance to the structural output across the plate in a more uniform way than the point-wise controllers. The research work has demonstrated that spatial controller managed to minimize the global plate vibrations and noise radiation that were due to the first five modes. / Thesis (M.Eng.Sc.)--School of Mechanical Engineering, 2005.