The focus of this research is the isolation of waterborne pathogens which are one of the grand challenges to human health, costing the lives of about 2.5 million people worldwide each year. The aim was to develop new microfluidic techniques for selectively concentrating and detecting waterborne pathogens. Detection of microbes in water can greatly help reduce deaths; however, analytical instruments cannot readily detect them due to the extreme dilution of these microbes, and hence, require significant sample concentration. Current methods are expensive and either require days to process or are not sufficiently robust for water monitoring. Microfluidic chips based on insulator-based dielectrophoresis (iDEP) provide a promising solution to these problems and have been previously used to selectively concentrate biological particle such as bacteria. The microfluidic devices in this work were created with a 3D mircofabrication technique, which we also developed as part of this project. The core process of the technique is the etching of 3D structures in silicon with a single plasma etch utilizing an effect known as reactive ion etch lag (RIE lag). Using this unique process, 3D devices are fabricated in both silicon and the polymer polydimenthylsiloxane (PDMS). Using both numerical modeling and experimental results, we show how these 3D structures enhance the performance of the dielectrophoretic devices. The main findings indicate that 3D structures can help reduce Joule heating in the devices and lower the applied voltage necessary to operate the devices. Additionally, within this work, we develop a new dielectrophoresis technique called off-chip passivated-electrode, insulator-based dielectrophoresis microchip (O"DEP). This technique combines the sensitivity of electrode-based dielectrophoresis (eDEP) with the high-throughput and inexpensive device characteristics of insulator-based dielectrophoresis. The result is a cartridge based system which is accessible, economical, high-performance, and high-throughput technologies allowing timely detection of pathogenic bacteria. / Ph. D.

This work was focused on the characterization of microparticles with particular emphasis on waterborne pathogens which pose a great health risk to human lives. The goal of this study was to develop microfluidic systems for enhanced characterization and isolation of bioparticles. Insulator-based dielectrophoresis (iDEP) is a promising technique for analyzing, characterizing and isolation of microparticles based on their electrical properties. By employing insulator-based constrictions within the microchannel in combination with microelectrodes within the vicinity of the electrodes, dielectrophoretic performance is enhanced. In this study, three dimensional insulator-based dielectrophoresis devices are fabricated using our in-house developed 3D micromachining technique. This technology combines the benefits of electrode-based DEP, insulator-based DEP, and three dimensional insulating features with the goal of improving trapping efficiency of biological species at low applied signals and fostering wide frequency range operation of the microfluidic device. The dielectric properties of bacteria as well as submicron polystyrene beads are discussed and the impact of these results on the future development of iDEP microfluidic systems is explored. / Master of Science

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The objective of this research is to introduce two state-of-the-art wireless biomedical systems: (1) a multiband transcutaneous communication system for implantable microelectronic devices (IMDs) and (2) a new wireless power delivery system, called the “EnerCage,” for experiments involving freely-behaving animals. The wireless multiband link for IMDs achieves power transmission via a pair of coils designed for maximum coupling efficiency. The data link is able to handle large communication bandwidth with minimum interference from the power-carrier thanks to its optimized geometry. Wireless data and power links have promising prospects for use in biomedical devices such as biosensors, neural recording, and neural stimulation devices. The EnerCage system includes a stationary unit with an array of coils for inductive power transmission and three-dimensional magnetic sensors for non-line-of-sight tracking of animal subjects. It aims to energize novel biological data-acquisition and stimulation instruments for long-term experiments, without interruption, on freely behaving small animal subjects in large experimental arenas. The EnerCage system has been tested in one-hour in vivo experiment for wireless power and data communication, and the results show the feasibility of this system. The contributions from this research work are summarized as follows: 1. Development of an inductive link model. 2. Development of an accurate PSC models, with parasitic effects for implantable devices. 3. Proposing the design procedure for the inductive link with optimal physical geometry to maximize the PTE. 4. Design of novel antenna and coil geometry for wireless multiband link: power carrier, forward data link, and back telemetry. 5. Development of a model of overlapping PSCs, which can create a homogenous magnetic in a large experimental area for wireless power transmission at a certain coupling distance. 6. Design and optimization for multi-coil link, which can provide optimal load matching for maximum PTE. 7. Design of the wireless power and data communication system for long-term animal experiments, without interruption, on freely behaving small animal subjects in any shape of experimental arenas.

Um micromecanismo é, essencialmente, um dispositivo de dimensões milimétricas ou até micrométricas que executa uma tarefa específica como atuar como garra, pinça, grampo, etc. Quando acoplados a um sistema eletrônico, são chamados de sistemas microeletromecânicos ou \"Micro-Electro-Mechanical Systems\" (MEMS). Esses dispositivos são quase todos constituídos por mecanismos flexíveis, onde o movimento é dado pela flexibilidade de sua estrutura, sem juntas e pinos. Uma das formas de atuação de micromecanismos é a eletrotermomecânica, onde uma atuação elétrica sobre o próprio mecanismo é convertida em calor, por efeito Joule, que gera tensões térmicas responsáveis pela deformação estrutural desejada. Recentemente, vários grupos de pesquisa no mundo estão desenvolvendo micromecanismos fabricados com dois (ou até mais) materiais, o que permite obter maiores deformações sem que seja excedido o limite de resistência do material e mais flexibilidade no projeto de micromecanismos que realizem diferentes tarefas quando sujeito a diversas atuações (multiflexíveis). As técnicas de processo de fabricação de micromecanismos atingiram um alto nível de maturidade. No entanto, a modelagem e, em particular, o desenvolvimento de métodos computacionais sistemáticos para o projeto estão ainda no seu estágio inicial. Atualmente, o projeto de micromecanismos com vários materiais vem sendo realizado por métodos de tentativa e erro, dependendo da intuição e experiência do projetista. Além disso, o projeto genérico de um MEMS eletrotermomecânico é uma tarefa complexa, que leva em conta conhecimentos multidisciplinares. Dessa forma, o objetivo desse trabalho de mestrado foi desenvolver um software para o projeto de MEMS multifásicos, atuados eletrotermicamente, usando um método de projeto genérico e sistemático, como o Método de Otimização Topológica (MOT). Utilizando um modelo de interpolação de material de função de pico, qualquer número de materiais pode ser considerado sem que haja aumento na quantidade de variáveis de projeto se comparado à otimização com apenas um material e vazio. Visando maximizar o deslocamento de saída contra uma peça de rigidez conhecida, foram projetados mecanismos atuados por tensão elétrica, alguns considerando multiflexibilidade. Um estudo da influência dos parâmetros da otimização foi realizado. Como uma alternativa à atuação eletrotermomecânica, foram projetados mecanismos atuados por fluxo de calor. / A micromechanism is essentially a device of milimetric, or even micrometric, dimensions that can actuate as a gripper, tweezers, clamp, etc. When coupled to an electronic system, they are called \"Micro-Electro-Mechanical Systems\" (MEMS). Almost all of these devices are constituted by compliant mechanisms, where the motion is allowed by the compliance of its own structure, rather than the presence of joint and pins. One of the forms of micromechanisms actuation is the electrothermomechanical, where an electric actuation applied to the mechanism is converted in heat, by Joule effect, that generates the thermal stress responsible for the desired structural deformation. Recently, many research groups around the world are developing micromechanisms manufactured with two (or even more) materials, what allows larger displacements without exceeding the materials ultimate tensile strength, and gives more flexibility in the design of micromechanisms that accomplish different tasks when under different actuations (multiflexible mechanisms). The manufacturing process techniques of micromechanisms reached a high level of maturity, however, the modelling and, particularly, the development of systematic computational methods for design are still in early stages. Nowadays, micromechanism design with many materials is being carried on by \"try and error\" methods, depending on designer intuition and experience. Also, a generic design of an electrothermomechanical MEMS is a complex task that needs multidisciplinary knowledge. Thus, the objective of this work is to develop a software for the design of multi-phase MEMS, electrothermomechanically actuated, using a method for systematic and generic design, such as Topology Optimization Method (TOM). Using a peak function material interpolation model, any number of materials can be considered without increasing the amount of design variables if compared to an optimization with only one material and void. Mechanisms actuated by electric tension were designed considering the maximization of output displacement against a work piece with known stiffness. The design of microactuators considering multiflexibility was also performed. A study of optimization parameters influence is presented. As an alternative to electrothermomechanical actuation, some mechanisms actuated by heat flow were designed.

Nesta dissertação, os principais conceitos de MEMS, suas aplicações, processos de fabricação, componentes e sistemas são abordados. O objetivo desta dissertação é o estudo detalhado de chaves MEMS para aplicações em RF, que apresentam bom comportamento em altas freqüências e com potencial de melhoria em sua banda de operação. Em particular, aprofundou-se o estudo para o caso de uma chave MEMS de membrana capacitiva paralela sobre um guia de onda coplanar ou CPW - Coplanar Waveguide. O objetivo foi o de ampliar sua banda de operação, mantendo-se outras especificações inalteradas. Partindo-se de uma chave com banda de operação nula para critérios de perda de retorno e isolação mínimas iguais a 20 dB, com alteração na geometria da chave foi possível obter-se uma banda de 28 GHz e posteriormente ampliá-la para 31 GHz, praticamente sem alteração nas demais características elétricas. / In this thesis, the main concepts of MEMS, their application, fabrication processes, components and systems are addressed. The objective of the thesis is a detailed study of MEMS switches for RF applications, that present good performance at high frequencies and with a potential for bandwidth improvement. More specifically, the study was deeply conducted for shunt capacitive membrane MEMS switches over CPW - Coplanar Waveguide. In this case, the objective was to enlarge the operation bandwidth, keeping the other specifications unchanged. Starting with a switch with null operational bandwidth for criteria of minimum return loss and isolation of 20 dB, after a modification in the switch geometry, it was possible to obtain an operational bandwidth of 28 GHz and then to enlarge it to 31 GHz, keeping almost unchanged the other electric characteristics.

Message Authentication Codes (MACs) are valuable tools for ensuring the integrity of messages. MACs may be built around a keyed hash function. Our main motivation was to prove that universal hash functions can be employed as underlying primitives of MACs in order to provide provable security in ultra-low-power applications such as the next generation self-powered sensor networks. The idea of using a universal hash function (NH) was explored in the construction of UMAC. This work presents three variations on NH, namely PH, PR and WH. The first hash function we propose, PH, produces a hash of length 2w and is shown to be 2^(-w)-almost universal. The other two hash functions, i.e. PR and WH, reach optimality and are proven to be universal hash functions with half the hash length of w. In addition, these schemes are simple enough to allow for efficient constructions. To the best of our knowledge the proposed hash functions are the first ones specifically designed for low-power hardware implementations. We achieve drastic power savings of up to 59% and speedup of up to 7.4 times over NH. Note that the speed improvement and the power reduction are accomplished simultaneously. Moreover, we show how the technique of multi- hashing and the Toeplitz approach can be combined to reduce the power and energy consumption even further while maintaining the same security level with a very slight increase in the amount of key material. At low frequencies the power and energy reductions are achieved simultaneously while keeping the hashing time constant. We develope formulae for estimation of leakage and dynamic power consumptions as well as energy consumption based on the frequency and the Toeplitz parameter t. We introduce a powerful method for scaling WH according to specific energy and power consumption requirements. This enables us to optimize the hash function implementation for use in ultra-low-power applications such as "Smart Dust" motes, RFIDs, and Piconet nodes. Our simulation results indicate that the implementation of WH-16 consumes only 2.95 ìW 500 kHz. It can therefore be integrated into a self- powered device. By virtue of their security and implementation features mentioned above, we believe that the proposed universal hash functions fill an important gap in cryptographic hardware applications.

Globally increasing levels of bandwidth and capacity requirements force the optical communications industry to produce new products that are faster, more powerful, and more efficient. In particular, optical-electronic-optical (O-E-O) conversions in Wavelength Division Multiplexing (WDM) mechanisms prevent higher data transfer speeds and create a serious bottleneck for optical communications. These O-E-O transitions are mostly encountered in the Wavelength converters of WDMs, and as a result, all-optical wavelength conversion methods have become extremely important. The main discussion in this thesis will concentrate on a specific all-optical wavelength conversion mechanism. In this mechanism, photonic crystal structures are integrated with moving MEMS/NEMS structures to create a state-of-the-art all-optical wavelength converter prototype. A wavelength conversion of 20% is achieved using this structure. Since the interaction of light with moving MEMS/NEMS structures plays an important role in the proposed wavelength conversion mechanism, modeling and simulation of electromagnetic waves becomes a very crucial step in the design process. Consequently, a subsection of this thesis will focus on a proposed enhancement to the finite-difference time-domain (FDTD) to model moving structures more efficiently and more realistically. This technique is named "Linear Dielectric Interpolation" and will be applied to more realistically and efficiently model the proposed photonic crystal MEMS/NEMS wavelength conversion mechanism.