THE ACOUSTIC WAVE SENSOR AND SOFT LITHOGRAPHY TECHNOLOGIES FOR CELL BIOLOGICAL STUDIES

Recently, cell-based biosensors have attracted many attentions because of their potential applications in fundamental biological research, drug development, and other fields. Acoustic wave biosensors offer powerful tools to probe cell behaviors and properties in a non-invasive, simple, and quantitative manner. Current studies on cell-based acoustic wave sensors are focused on experimental investigation of thickness shear mode (TSM) sensors for monitoring cell attachment and spreading. There are no theoretical models for cell-based TSM biosensors. No studies on other cell biological applications of TSM sensors or on surface acoustic wave cell-based biosensors have been performed. The reliability and sensitivity of current cell-based biosensors are low. Improving them requires studies on engineering cells and understanding the effects of cell morphology on cell function.The overall objective of this dissertation is to develop acoustic wave sensor systems for cell biological studies and to determine the effects of cell shape on cell function. Our study includes three parts: (1) Development of cell-based TSM sensor system; (2) Studies of Love mode devices as cell-based biosensors; (3) Studies of the effects of cell shape on cell function. In the first part, a theoretical model was developed, changes in cell adhesion were monitored and cell viscoelasticity was characterized by TSM sensor systems. The TSM sensor systems were demonstrated to provide a non-invasive, simple, and reliable method to monitor cell adhesion and characterize cell viscoelasticity. In the second part, a theoretical model was developed to determine signal changes in Love mode sensors due to cells attaching on their surface. Experimental results validated the model. In the third part, cell shape was patterned to different aspect ratios. Elongated tendon cells were found to express higher collagen type I than shorter cells. Changes in cell shape induced alterations in cytoskeleton, focal adhesions, and traction forces in cells, which may collectively prompt the observed differential collagen type I expression in cells with different shapes. Overall, our research expanded the applications of acoustic wave cell-based biosensors. Studies on cell shape control and the effects of cell shape on cell function will be useful for increasing the sensitivity of cell-based biosensors in future research

Thin-film piezoelectric-on-substrate resonators and narrowband filters

A new class of micromachined devices called thin-film piezoelectric-on-substrate (TPoS) resonators is introduced, and the performance of these devices in RF and sensor applications is studied. TPoS resonators benefit from high electromechanical coupling of piezoelectric transduction mechanism and superior acoustic properties of a substrate such as single crystal silicon. Therefore, the motional impedance of these resonators are significantly smaller compared to typical capacitively-transduced counterparts while they exhibit relatively high quality factor and power handling and can be operated in air. The combination of all these features suggests TPoS resonators as a viable alternative for current acoustic devices. In this thesis, design and fabrication methods to realize dispersed-frequency lateral-extensional TPoS resonators are discussed. TPoS devices are fabricated on both silicon-on-insulator and thin-film nanocrystalline diamond substrates. The performance of these resonators in simple and low-power oscillators is measured and compared. Furthermore, a unique coupling technique for implementation of high frequency filters is introduced in which dual resonance modes of a single resonant structure are coupled. The measured results of this work show that these filters are suitable candidates for single-chip implementation of multiple-frequency narrow-band filters with high out-of-band rejection in a small footprint.Ph.D.Committee Chair: Farrokh Ayazi; Committee Member: James D. Meindl; Committee Member: John D. Cressler; Committee Member: Nazanin Bassiri-Gharb; Committee Member: Oliver Bran

Kytketyt MEMS-resonaattoriverkot

Micromechanical resonance frequencies are in a standard manner a few tens of MHz and can even cover the requency range up to a few GHz. When using high quality material such as quartz of silicon, also internal losses are very low. By physical coupling of resonators into a network, one can realize various mechanical signal processing, filtering or for example neural network type behavior. Since coupling between resonators are realized by some kind of bridge, which can be either rather linear or alternatively intentionally very nonlinear, the overall behavior of the whole network is very complex. Of general interest are effects that originate from multiple inputs and outputs and which could lead to a rather unexpected spectral or transient behavior of the signals, which can be found by computer modelling.Mikromekaaniset resonanssitaajuudet ovat tyypillisesti muutamia kymmeniä megahertsejä mutta voivat kattaa taajuuskaistan aina muutamiin gigahertseihin asti. Käytettäessä korkealaatuisia materiaaleja kuten kvartsia tai piitä myös signaalin häviöt ovat erittäin pieniä. Kytkemällä resonaattoreita fyysiseksi verkoksi voidaan mekaanisilla rakenteilla suorittaa signaalinkäsittelyä, realisoida suodattimia ja jopa neuroverkkoja. Koska yksittäisten resonaattorien välinen kytkentä on jonkinlainen silta, joka voi olla joko melko lineaarinen tai vaihtoehtoisesti tarkoituksellisesti erittäin epälineaarinen, on koko verkon käyttäytyminen erittäin monimutkaista. Yleisesti kiinnostavia ovat useista sisäänmenoista ja ulostuloista johtuvat ilmiöt, jotka voivat johtaa signaalien spektrin tai transienttivasteen melko odottamattomaan tai epäintuitiiviseen käyttäytymiseen, jonka voi löytää ja tulkita tietokonesimulaatioilla

Résonateurs à haut Q en mode d'extension 2D pour possibles applications temps-fréquence

International audienceThis paper presents recent advances on two dimensional length-extension mode (2D-LEM) quartz resonators providing high quality (Q) factor on resonances at a few MHz. The resonators have been collectively manufactured using one or two steps quartz deep reactive-ion etching (DRIE) processes. These resonators combine the intrinsic qualities of quartz in comparison to silicon (i.e. high Q factor, low temperature sensitivity and piezoelectricity) and the advantages of microelectromechanical systems (MEMS) resonators: small dimensions, low power consumption and collective processes. Samples vibrating at frequencies f of 2.2, 3 and 4.5 MHz have shown promising results with very high Q factor. Q factor as high as 180,000 for fundamental mode vibrating at 2.2 MHz and 89,000 for harmonic mode at 8.9 MHz were measured which lead to quality factor and resonance frequency products (Q·f) figure of merit near 10^12 Hz at the state of the art for 2D-LEM quartz resonators and the higher Q factor measured for DRIE made quartz resonators. Two designs, several dimensions and two processes have been investigated. Two main limiting damping mechanisms were identified and one of them is strongly linked to the technological limits of the etching process.Ce document présente les avancées récentes sur les résonateurs à quartz en mode d'extension bidimensionnelle de la longueur (2D-LEM) qui fournissent facteur de haute qualité (Q) sur les résonances à quelques MHz. Les résonateurs ont été fabriqués collectivement en utilisant un ou deux étapes des processus de gravure profonde par ions réactifs du quartz (DRIE). Ces résonateurs combinent les qualités intrinsèques du quartz dans par rapport au silicium (facteur Q élevé, faible sensibilité à la température et piézoélectricité) et les avantages de la microélectromécanique les résonateurs des systèmes MEMS : petites dimensions, faible consommation d'énergie et processus collectifs.Des échantillons vibrant à des fréquences f de 2,2, 3 et 4,5 MHz ont donné des résultats prometteurs avec un facteur Q très élevé. Le facteur Q comme jusqu'à 180 000 pour le mode fondamental vibrant à 2,2 MHz et 89 000 pour le mode harmonique à 8,9 MHz ont été mesurés qui conduisent à un facteur de qualité et à des produits de fréquence de résonance (Qxf) d'un mérite proche de 10^12 Hz à l'état de l'art pourLes résonateurs à quartz 2D-LEM et le facteur Q plus élevé mesuré pour le MEIR ont fait des résonateurs à quartz. Deux modèles, plusieurs et deux processus ont été étudiés. Deux principaux mécanismes d'amortissement limitatifs ont été identifiés et l'un des est fortement liée aux limites technologiques du processus de gravure

MEM Resonators for RF Applications and Chemical Sensing

In this thesis modelling, design, fabrication and characterization of MEM (MicroElectroMechanical) resonators for RF applications and chemical sensing are discussed. MEM resonators allow to obtain integrated highly selective filters and low phase noise oscillators for RF applications, as well as sensors of chemical and biological species, which can be used to obtain a sensor array on a chip, leading to the possibility of very complex analysis in a very small space. Specifically, a novel RF device, namely a free-free resonator on the third mode, is presented and its basic working is demonstrated. Effect of temperature and axial stress on this device and on other flexural resonators is discussed and an equivalent circuit for free-free resonator is proposed. Furthermore, the optimized design of a bulk-mode disk resonator is presented. The goal of this optimization is the achievement of the maximum quality factor (i.e. maximizing selectivity in filter architecture or minimizing the phase noise in resonator-based oscillators) at a target resonance frequency. The maximization is based on an original strategy of estimation of the quality factor of the device through FEM simulations. Finally, the design of an innovative microbalance is presented. The main features of this device are the actuation and the sensing, which are both magnetic. The device has been fabricated with a CMOS-compatible process. The frequency response of the device was measured, showing the basic working of the device

High-Performance Reconfigurable Piezoelectric Resonators and Filters for RF Frontend Applications

A conventional RF frontend module consists of many filters where each filter is allocated for a specific frequency band. These filters are connected through multiplexing switch networks to support multi-band wireless standards. Using an individual filter for each frequency band increases the module size, power consumption and cost. Therefore, implementation of reconfigurable filters that can operate at different frequency bands while maintaining key RF performance requirements such as low insertion loss, good linearity and power handling is necessary for manufacturing of future RF frontends. Acoustic wave resonators based on piezoelectric devices such as Surface Acoustic Wave (SAW) and Bulk Acoustic Wave (BAW) are the most commonly used technologies to manufacture filters for RF applications. The objective of the research described in this thesis is to investigate the feasibility of tunable filter solutions using piezoelectric SAW resonators. A tunable SAW technology which can maintain required performance parameters and can be commercially manufactured will constitute a technological breakthrough in wireless communications. Thin-Film Piezoelectric on Substrate (TPoS) resonators, based on Aluminum Nitride (AlN) piezoelectric material which are fabricated using commercially available Silicon on Insulator (SOI) PiezoMUMPs process, have been demonstrated. By combining the superior acoustic properties of AlN and single crystalline silicon substrate, this class of resonators achieves ultra-high quality factor (Q) values in excess of 3600. A 3-pole bandpass filter using direct electrical coupling between the resonators has been presented and we have studied the performance of the fabricated filter over a temperature range from -196ºC up to +120ºC and under high power. For the first time, we have demonstrated the integration of switching elements, based on Vanadium Dioxide (VO2) phase change material, with Incredible-High-Performance SAW (IHP-SAW) technology which allows us to design and implement switchable and reconfigurable SAW resonators and filters for wireless applications. Switchable multi-band filters using VO2 switches strategically imbedded within the resonators of the filter have been demonstrated. A switchable dual-band filter with four switching states and two channels was presented using hybrid integration approach where discrete VO2 switches were fabricated separately and then integrated with the SAW resonators and filters using wire bonds. The fabricated 5-pole dual-band filter demonstrated good insertion loss in both transmission states but had inadequate performance in terms of isolation between the channels due to the limitations of the hybrid integration approach. Moreover, hybrid integration does not allow us to use more than a few switching elements and cannot be used for the implementation of higher order filters. To address these issues, we have demonstrated the monolithic integration of VO2 switches using an in-house fabrication process that allows us to fabricate VO2 switches and SAW resonators and filters on a single chip. A dual-band switchable higher order 7-pole filter with six monolithically integrated VO2 switches, three for each channel, was demonstrated. The monolithic integration allows the single-chip implementation of the proposed switchable dual-band filter with improved performance along with significant size reduction and ease of manufacturing, paving the path for commercialization of this technology. Novel reconfigurable SAW resonators and filters with tunable center frequency were also presented for the first time. Tuning of the center frequency between two different states was achieved by changing the configuration of interdigitated electrodes within the SAW resonator and by using a set of tuning electrodes and VO2 switches. In the first implementation, the VO2 switches were integrated over the electrodes and inside the active area of the SAW resonator. Each resonator consists of hundreds of tuning electrodes and for a reliable switching each resonator requires a number of heater elements which results in increased DC power consumption and total size. A second reconfigurable resonator with a modified structure and using a modified in-house fabrication process to include a second electrode layer was proposed to reduce the number of required VO2 switching elements for an even more compact implementation and ten times reduction in the required DC power consumption. Design, implementation, and measurement results for a 3-pole tunable SAW filter based on the proposed reconfigurable resonators have been presented. The filter’s center frequency is tuned from 733 MHz to 713 MHz while the insertion loss was maintained below 2.5 dB. The fabricated SAW resonators and filters also showed acceptable linear and high-power performance characteristics. This is the first time a single-chip implementation of a reconfigurable SAW filter with center frequency tuning and acceptable RF performance using monolithically integrated VO2 switches is ever reported. The single-chip implementation of the proposed SAW resonators and filters enables the development of future low-cost RF multi-band transceivers with improved performance and functionality

Sensorless Position Control of Piezoelectric Ultrasonic Motors:a Mechatronic Design Approach

This dissertation considers mechatronic systems driven by piezoelectric ultrasonic motors (PUM). The focus is set on optimal system design and sensorless position control. Mechatronic industry faces the challenge to deliver ever more efficient and reliable products while being confronted to increasingly short time to market demands and economic constraints driven by competition. Although optimal design strategies are applied to master this challenge, they do not entirely respond to the given circumstances, as often only local criteria are optimised. In order to obtain a globally optimal solution, the many subfunctions of a mechatronic system and their models must be interrelated and evaluated concurrently from the very beginning of the design process. In this context PUM have been used increasingly during the last decade for various positioning applications in the field of mechatronic systems, laboratory equipment, and consumer electronics where their performances are superior to conventional electromechanical drive systems based on DC or BLDC motors. The position of the mobile component must be controlled. In some cases open-loop control is a solution, but more often than not sensors are used as feedback device in closed-loop control. Sensors are expensive, large in size and add fragile hardware to the device that compromises its reliability. Thus, not only the superior performance is not fully exploited but also the economical feasibility of the PUM drive system is jeopardised. Replacing sensors by advanced control techniques is an approach to these problems that is well established in the field of BLDC motors. Those sensorless control strategies are not directly transferrable, because of the fundamentally different working principles of PUM. Hence, the research of sensorless closed-loop position control techniques applicable to PUM and their validation with digitally controlled functional models is the very topic of this thesis. We propose a dedicated design methodology to this statement of the problem. A core model of the mechatronic system is conceived as general and simple as possible. It then develops for the different interrelated views reflecting the mechanical, electromechanical, drive electronic, sensorial and digital control functions of the global system. Each one becoming more specific and detailed in this process, the different views still enable mutual constraint adjustments and the dynamic integration of results from the other views during the design process. Starting with the stator of the PUM, a view describes the mechanical displacement. An electric equivalent model is written such that power input from the drive electronics is related to the mechanical energy transmitted to the mechanics. The resulting differential equations are solved by the finite element method (FEM). Position feedback configurations in the mobile part of the PUM are modelled analytically in order to be implemented in digital control and their electrical implications are updated to the stator model. In this way, sensors do not necessarily materialise physically any more, but are distributed among the mechanical configuration, the drive electronics and the digital controller. With respect to the sensor data, the controller is not simply receiving finalised data on the measured system parameter, but rather implements the sensor itself in software. Finally, the position detection performance obtained with the aforementioned design methodology was evaluated with the example of mechatronic locking devices actuated by custom-made as well as OEM motors. Functional models of motors, electronics and digital controllers were used to identify the limits of the proposed methods, and suggestions for further research were deduced. These results contribute to the development of robust sensorless position controllers for PUM