The exploration of Microelectromechanical systems (MEMS) represents a crucial aspect in the advancement of modern science and technology. They offer low-cost solutions to miniaturize numerous devices. The increasing use of MEMS applications in biological research has created a pressing need for reliable micromanipulation tools. In this context, microgrippers have emerged as promising tools for the precise handling and characterization of biological samples. This thesis presents a novel biocompatible microgripper that utilizes electrothermal actuation integrated with a rotary capacitive position sensor. To overcome the limited displacement possibilities associated with electrothermal actuators, this microgripper incorporates conjugate surface flexure hinges (CSFH). These hinges enhance the desired tweezers output displacement. The designed microgripper can in principle manipulate biological samples ranging in size from 15 to 120 μm. Based on the sensitivity calculation of the rotary capacitive position sensors, the sensitivity of the displacement measurement is 102 fF/μm. By employing a kinematics modeling approach based on the pseudo-rigid-body method (PRBM), an equation for the displacement amplification factor is developed, and this equation is subsequently verified through FEM-based simulations. By comparing the amplification ratio value obtained from the analytical modeling and simulations, there is an excellent match, with a relative difference of only ~1%, thus demonstrating the effectiveness of the PRBM approach in modeling the kinematics of the structure under investigation. In addition to this, by using analytical modeling based on finite elements method (FEM), the design of the electrothermal actuator and the heat dissipation mechanism is optimized. FEM-based simulations are used to validate the theoretical modeling, demonstrating good agreement between the displacements derived from analytical modeling and simulations. The temperature difference (∆T) across a range from room temperature to 278°C exhibits a relative difference of ~2.8%. Moreover, underpass technology is implemented to ensure that electrical signals or disturbances from other parts of the device, such as the electrothermal actuation system, do not interfere with the operation and integrity of the gripping mechanism. Ultimately, the microgripper is fabricated using conventional MEMS technology from a silicon-on-insulator (SOI) wafer through the deep reactive ion etching (DRIE) technique. The integration of theoretical modeling, simulations, and practical fabrication highlights a compelling approach that has the potential for transformative applications in the field of micromanipulation and biological sample handling. Furthermore, we propose a C-shaped structure with a curved beam mechanism to improve the movement provided by the thermal actuators. The design of experiment (DOE) method is used to optimize the geometrical parameters of our proposed device. Analytical modeling based on Castigliano's second theorem and finite element method (FEM) simulations are used to predict the behavior of the symmetrical C-shaped structure; the results are in good agreement. The MEMS-based rotational structures are fabricated on silicon-on-insulator (SOI) wafers using bulk micromachining and deep reactive ion etching (DRIE). The fabricated devices are tested; our findings reveal that our proposed MEMS rotational structure outperforms the symmetrical lancet structure by 28% in terms of delivered displacement. Furthermore, the experimental results agree well with those obtained through numerical analysis.

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.

Instrument miniaturization is led by the desire to perform rapid diagnosis in remote areas with high throughput and low cost. In addition, miniaturized instruments hold the promise of consuming small sample volumes and are thus less prone to cross-contamination. Gas chromatography (GC) is the leading analytical instrument for the analysis of volatile organic compounds (VOCs). Due to its wide-ranging applications, it has received great attention both from industrial sectors and scientific communities. Recently, numerous research efforts have benefited from the advancements in micro-electromechanical system (MEMS) and nanotechnology based solutions to miniaturize the key components of GC instrument (pre-concentrator/injector, separation column, valves, pumps, and the detector). The purpose of this dissertation is to address the critical need of developing a micro GC system for various field- applications. The uniqueness of this work is to emphasize on the importance of integrating the basic components of μGC (including sampling/injection, separation and detection) on a single platform. This integration leads to overall improved performance as well as reducing the manufacturing cost of this technology. In this regard, the implementation of micro helium discharge photoionization detector (μDPID) in silicon-glass architecture served as a major accomplishment enabling its monolithic integration with the micro separation column (μSC). For the first time, the operation of a monolithic integrated module under temperature and flow programming conditions has been demonstrated to achieve rapid chromatographic analysis of a complex sample. Furthermore, an innovative sample injection mechanism has been incorporated in the integrated module to present the idea of a chip-scale μGC system. The possibility of using μGC technology in practical applications such as breath analysis and water monitoring is also demonstrated. Moreover, a nanotechnology based scheme for enhancing the adsorption capacity of the microfabricated pre-concentrator is also described. / 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

Microelectromechanical Systems are ubiquitous in modern technology, with applications ranging from accelerometers in smartphones to ultra-high precision motion stages used for atomically-precise positioning. With the appropriate selection of materials and device design, MEMS resonators with ultra-high quality factors can be fabricated at minimal cost. As the sizes of such resonators decrease, however, their mechanical, electrical, and material properties can no longer be treated as linear, as can be done for larger-scale devices. Unfortunately, adding nonlinear effects to a system changes its dynamics from exactly-solvable to only solvable in specific cases, if at all. Despite (and because of) these added complications, nonlinear effects open up an entirely new world of behaviors that can be measured or taken advantage of to create even more advanced technologies. In our resonators, oscillations are induced and measured using aluminum nitride transducers. I used this mechanism for several separate highly-sensitive experiments. In the first, I demonstrate the incredible sensitivity of these resonators by actuating a mechanical resonant mode using only the force generated by the radiation pressure of a laser at room temperature. In the following three experiments, which use similar mechanisms, I demonstrate information transfer and force measurements by taking advantage of the nonlinear behavior of the resonators. When nonlinear resonators are strongly driven, they exhibit sum and difference frequency generation, in which a large carrier signal can be mixed with a much smaller modulation to produce signals at sum and difference frequencies of the two signals. These sum and difference signals are used to detect information encoded in the modulation signal using optical radiation pressure and acoustic pressure waves. Finally, in my experiments, I probe the nonlinear nature of the piezoelectric material rather than take advantage of the nonlinear resonator behavior. The relative sizes of the linear and nonlinear portions of the piezoelectric constant can be determined because the force applied to the resonator by a transducer is independent of the dielectric constant. This method allowed me to quantify the nonlinear constants.

The field of microfluidics has the potential to provide a number of products to better everyday life, but is still not well understood. In previous research performed in the field, microfluidics has been shown to exhibit behavior different from what would be expected through normal pipe flow theory. While some research has shown that fluid flow through microchannels does conform to the theoretical flow mechanics, and thus can be predicted and understood through use of well-known relations; other research performed has indicated that fluid flow through microchannels experiences higher or lower pressure losses than would be expected with macro scale theory. This work strives to further explore and explain this anomaly by focusing on simple straight rectangular channels of varying hydraulic diameters from 24 µm to 88 µm, in order to form a more basic understanding for fluid flow in microchannels. Water was pumped through each of these channels at a number of different flow rates, and the static pressure was measured in two locations, a set length apart. The measured pressure loss over this length for each flow rate was then recorded and analyzed to provide relations between pressure loss and hydraulic diameter. Through the data obtained in this study, microfluidic flow of Reynolds numbers greater than 40 and in channels as small as 48 µm in diameter experienced pressure losses predicted from macroscale theory. Below these values, the data was more random, but still showed some conformance to theory. A clear relationship between measured pressure loss and hydraulic diameters over the entire range of channels was also found for two different flow rates. It is hoped that the data obtained will provide a better understanding of microfluidics and pave the way for potential applications to be realized.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第25280号 / 工博第5239号 / 新制||工||1998(附属図書館) / 京都大学大学院工学研究科マイクロエンジニアリング専攻 / (主査)教授 土屋 智由, 教授 蓮尾 昌裕, 教授 平方 寛之 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

The recent years have witnessed an unprecedented growth in the number of connected devices and amount of bandwidth required by the multiple services offered by wireless devices. The current 5G standard addresses such issues by adopting higher carrier frequencies and antennas with a large number of radiating elements. The former solution enables to exploit larger bandwidths in the millimeter-wave (mmWave) portion of the spectrum, while the latter one allows access points to serve an increasingly higher number of users. Both find realization in the Multiple-Input-Multiple-Output (MIMO) antenna systems with their enhanced beamforming capabilities. While the adoption of the hybrid digital-analog beamforming architecture lightens the overall system complexity, the need of miniaturized, high-performance and broadband hardware components is still an open issue. Passive Radio Frequency (RF) components in MicroElectroMechanical-Systems technology (RF-MEMS) offer notable and broadband electrical performances, while maintaining the marked miniaturization required for the hardware to be employed in the MIMO antennas, characterizing the current and future telecommunications scenario. Whilst numerous examples of single RF-MEMS switches, attenuators and phase shifters are available in the literature since about two decades, still limited attention is dedicated to the development of MEMS-based multi-device monolithic networks embedding such devices. High-performance RF-MEMS networks of this kind could represent the base of future MIMO beamforming architectures. Given such a context, the fundamental core of this thesis is the design and the realization of ad hoc RF-MEMS devices to be integrated in a reconfigurable monolithic module, operating in the realistic scenario of the mm-Wave portion of the spectrum allocated to 5G in Europe (24.25–27.5 GHz). The resulting devices consist in a 3-bit attenuator, three 1-bit phase-shifting cells and a Single-Pole-Double-Throw (SPDT) switch, each relying on membranes featuring a reduced actuation voltage, in the 5–9 V range, for an easier interfacing with electronics based on Complementary Metal–Oxide–Semiconductor (CMOS). To this purpose, the ad hoc designed MEMS switching membranes, along with prototypes of the building blocks to be embedded in the final module, are designed, optimized and fabricated. The experimental measurements performed on the prototypes of membranes (i.e. micro-switches), attenuation cells, optimized resistors and a phase shifter are compared to FEM-based (Finite Element Method) simulated results. Such comparison validates the simulation approach, in both the electromagnetic and the electro-mechanical domains, by which the proposed module is then designed and optimized in its final layout. To the best of our knowledge, this project is among the first to investigate the development of a monolithic module, entirely based on RF-MEMS passives, implementing both the attenuation and the phase shifting functionalities that can be employed in hybrid beamforming architectures at each antenna element. More in detail, the module features at least 25 attenuation and phase shifting states, from -5.39 dB to -13.51 dB by variable steps, and from 10.59° to 158.46°, respectively. Concerning the SPDT switch, satisfying electrical performances have been demonstrated in terms of return loss (<-10 dB), insertion loss (<-1.2 dB) and isolation (<-25 dB) over the 0–30 GHz interval. Despite their increased complexity, appealing results have marked the proposed attenuator and the phase-shifting cells, whose return and insertion losses are always better than -10 dB and -3 dB, respectively, along the frequency interval of interest. With an overall footprint not exceeding 9.51x3.35 mm2, the designed module effectively combines the miniaturization, broadband, and linear electrical behavior of RF-MEMS, making it a suitable candidate for the MIMO antennas of the current and future telecommunications scenario.

Le Haut-Parleur Digital Matriciel (HPDM) est un moyen de transduction électroacoustique qui reçoit comme entrée un signal numérique et qui effectue la conversion vers l'analogique directement dans l'air. Il est constitué de plusieurs éléments rayonnants disposés au sein d'une matrice. Ces éléments seront désignés par le terme «speaklet» lorsqu'ils sont de tailles réduites. Le rayonnement acoustique du HPDM est en effet très sensible à la taille de la matrice, ce qui le rend tout particulièrement adapté à la technologie MEMS. Cette thèse porte sur l'étude de HPDM MEMS piézoélectriques. Après une introduction qui débute par certaines généralités jusqu'à se focaliser sur le sujet, la thèse aborde les modélisations multiphysiques des HPDM étudiés, le dimensionnement des speaklets puis les tests expérimentaux. Des modèles analytiques ainsi que des simulations numériques et par éléments finis sont mis en place et permettent de prédire le comportement mécanique des speaklets présentés, les pressions rayonnées par les HPDM et les puissances électriques consommées. Les speaklets sont ensuite dimensionnés à partir de l'empilement technologique afin de maximiser le niveau de pression qu'ils génèrent. Des tests expérimentaux permettent alors de valider la majorité des modèles ou au contraire de revenir sur certains d'entre eux pour les optimiser ou montrer leurs limitations. Les résultats ont en effet montré l'importance de la prise en compte des contraintes résiduelles, qui provoquent une déformée initiale des speaklets et modifient leurs fréquences propres, rendant alors l'utilisation de grands rayons inefficaces. En accord avec les modèles, les speaklets possèdent un comportement dynamique linéaire, ce qui permet de les caractériser à l'aide de fonctions de transfert. La théorie et les enregistrements sonores montrent alors qu'un HPDM composé de tels speaklets permet dans le meilleur des cas de produire une pression identique à celle générée par la même matrice pilotée en analogique. Dans notre cas, des taux de distorsions supérieurs ont été obtenus lors des reconstructions digitales, à cause des réponses non uniformes des speaklets, dues à des résistances d'accès différentes. Le HPDM présenté possède cependant d'autres avantages, le plus important étant la très faible consommation électrique qu'il est théoriquement possible d'atteindre en utilisant les méthodes de charges et de décharges adiabatiques. Le HPDM piézoélectrique MEMS apparait donc comme étant une technologie prometteuse. L'optimisation de notre premier prototype à l'aide des outils développés doit en effet conduire à un HPDM capable de générer une pression équivalente à celle obtenue en mode analogique, mais avec un rendement électroacoustique beaucoup plus important. Les futurs travaux devront ensuite se concentrer sur la conception de speaklets non-linéaires et sur la forme du pulse de pression qu'ils génèrent, afin de gagner en niveau sonore. / The Digital Loudspeaker Array (DLA) is an electroacoustic transducer which receives as input a digital signal and performs the analog conversion directly into the air. It consists of a plurality of radiating elements arranged in a matrix. These elements will be designated by the term “speaklet” when they are reduced in size. The acoustic radiation of a DLA is indeed very sensitive to the size of the matrix due to differences in path length, which makes it especially suitable for MEMS technology. This thesis is on the study of a piezoelectric MEMS DLA. After an introduction that is increasingly focused on the subject, the thesis addresses the multiphysics modeling of the DLA, dimensioning of the speaklets and experimental tests. Analytical formulas, numerical simulations and finite element models are developed and used to predict the mechanical behavior of the presented speaklets, the pressure radiated by the DLA and the electrical power consumption. The speaklet are then dimensioned from the technological stack (set in advance) in order to maximize the pressure level. Experimental tests involving the use of an anechoic chamber, an optical interferometer, a vibrometer and an impedancemeter validate most of the models. Otherwise, these tests are usefull for improving some of them or for showing their limitations. The results have shown the importance of the residual stresses, which cause an initial deformation of the speaklets and modify their resonance frequencies, thus rendering ineffective the use of large radii. In accordance with the models, the static deflection of the speaklets is nonlinear but their dynamic behavior is linear. This enables characterizations using transfer functions. Theory and sound recordings show that a DLA made of such speaklets can produce in the best case the same pressure to that generated by the same matrix driven in an analog way. In our case, more distortions were obtained in digital reconstructions because of non-uniform responses of the speaklets, due to different access resistances. However, the presented DLA has other advantages, the most important being the very low power consumption it is theoretically possible to achieve using the adiabatic charge principle. The piezoelectric MEMS DLA thus appears as a promising technology. The optimization of our first prototype using the developed tools should indeed lead to a DLA able to generate an equivalent presure to that obtained with analog control, but with a far greater electroacoustic efficiency. Future work should then focus on the design of nonlinear speaklets and on the shaping of the pulse of pressure they generate, in order to increase the total pressure level.

O desenvolvimento deste trabalho foi motivado pela alta demanda de novas aplicações para o mercado do consumidor que necessitam de sistemas de transmissão e recepção de dados sem fio trabalhando na região de ondas milimétricas (mmW - entre 30 GHz e 300 GHz). Para estes tipos de sistemas, os defasadores são cruciais por definir o custo e o tamanho do dispositivo final. A pesquisa bibliográfica mostra que a melhor opção são os defasadores passivos do tipo linha carregada que utilizam Sistemas Microeletromecânicos (MEMS) como elemento de ajuste para a mudança de fase. Por esse motivo neste trabalho foi feito o estudo de diferentes tecnologias para o desenvolvimento de defasadores baseados em MEMS distribuídos e linhas de transmissão com efeito de ondas lentas de tipo shielded-CoPlanar Stripline (S-CPS) e shielded-Coplanar Waveguide (S-CPW). Foram estudadas três diferentes tecnologias: a tecnologia CMOS; a tecnologia dedicada desenvolvida pelo Laboratoire d\'électronique des technologies de l\'information (CEA-Leti) e a tecnologia in-house desenvolvida no Laboratório de Microeletrônica da Universidade de São Paulo. Utilizando a tecnologia CMOS foram fabricadas linhas de transmissão de tipo S-CPS utilizando a tecnologia de 250 nm da IHP (Innovations for High Performance Microelectronics) e a tecnologia de 0,35 µm da AMS (Austria Micro Systems). A tecnologia de 0,35 µm da AMS foi utilizada também para o desenvolvimento de defasadores de 2-bits e 3-bits baseados em linhas de transmissão de tipo S-CPW. Para estes defasadores foi definido um processo de liberação da camada de blindagem, reprodutível, que permitiu a atuação do dispositivo. Outros defasadores baseados em S-CPW que foram desenvolvidos anteriormente com a tecnologia dedicada CEA-LETI, foram modelados eletrostaticamente utilizando o Comsol MultiPhysics e o Ansys Workbench. Os modelos desenvolvidos permitiram entender o comportamento eletromecânico do defasador e foram utilizados reprojetar o defasador com um desempenho otimizado. Finalmente, visando o desenvolvimento dos dispositivos otimizados utilizando a tecnologia in house com os materiais e métodos disponíveis no Laboratório de Microeletrônica da USP (LME-USP), foram estudadas algumas etapas críticas do processo de fabricação. / The development of this work is motivated by the high demand for new applications for the consumer market that require wireless systems for data transmission and reception working in the millimeter wave region (mmW - between 30 GHz and 300 GHz). For these kinds of systems, the phase shifter are crucial to define the cost and size of the final device. The bibliographical research shows that the best option are the passive load line-type phase shifters using Microelectromechanical Systems (MEMS) as tuning element. Therefore, in this work, the study of different technologies for the development of phase shifter based on distributed MEMS and slow-wave transmission lines. The two types of transmission lines considered were the shielded-CoPlanar Stripline (S-CPS) and shielded-Coplanar Waveguide line (S-CPW). Three different technologies were studied: CMOS technology; the dedicated technology developed by the Laboratoire d\'électronique des technologies de l\'information (CEA-Leti) and the in-house technology developed at the Microelectronics Laboratory of the University of São Paulo. Using the CMOS technology, S-CPS-type transmission lines were fabricated using IHP\'s 250 nm CMOS technology and AMS\'s 0.35 µm CMOS technology. AMS\'s 0.35 µm technology has also been used for the development of 2-bit and 3-bit phase-shifters based on S-CPW type transmission lines. For these phase shifters, a reproducible shielding layer release process was defined that allowed the device to operate. Also, another phase shifter based in S-CPW-type transmission lines that were previously developed with dedicated CEA-LETI technology was electrostatically modeled using Comsol MultiPhysics and Ansys Workbench. The developed models allowed to understand the electromechanical behavior of the phase shifter and was used for a new design of the phase shifter with an optimized performance. Finally, in order to develop the optimized devices using the in-house technology with the materials and methods available at the USP Microelectronics Laboratory (LME-USP), some critical stages of the fabrication process were studied.