Design And Modeling Of An Electrostatic Ally Actuated Mems Micromirror For Light Detection And Ranging

A Light Detection and Ranging (LIDAR) system, which is one of the promising technologies for autonomous vehicles, contains many miniature micromachined devices. The micromirror is one of the key components inside the LIDAR system that contributes to the performance of LIDAR. The “stroke” level of the micromirror affects the performance of the micromirror and hence the LIDAR. Therefore, this research focuses on a new approach to increase the level of stroke of the micromirror in an effort to enhance the device properties. In this thesis, four different design configurations of micromirrors are proposed and developed. The proposed micromirrors are based on dynamically-moving capacitor concepts that are actuated using electrostatic actuation. Unlike traditional micromirrors, the developed micromirrors employ three bottom electrodes, which enforces an upward deflection and, therefore, reduces the pull-in instability effect and improves the stroke of the micromirror. Critical design parameters of the micromirror that affect the stroke are studied to develop the four proposed designs. The PolyMUMPs fabrication technique is chosen to fabricate all four proposed micromirror designs. When the micromirror is fabricated using the PolyMUMPs fabrication technique, without any modification in the fabrication steps, the maximum achievable air cavity between the parallel plates is 2.0µm. However, in this thesis, in an unconventional way, the air cavity is increased from 2.0µm to 2.75µm. This is achieved by combining two oxide layers in the fabrication process. In this new design, a high stroke level of 5.07µm is achieved that, in return, will further enhance the performance of the LIDAR. COMSOL Multiphysics software and the MEMS module are used to investigate and analyze the performance of the proposed micromirrors and compare them with conventional MEMS micromirrors

Tilting micromirror platform based on liquid dielectrophoresis

This study presents an electrically actuated tilting micro platform based on liquid dielectrophoresis with three axes movement using three droplets situated 120° apart from each other. The interdigitated electrodes produce a non-uniform electric field that generates a body force. The dielectrophoretic mechanism is responsive within at least 30 ms, and it eliminates the solid-solid contact. The tilting platform enabled an angular coverage up to 0.9° (±0.02°), with a maximum displacement of 120 µm. The tilting micromirror platform has beam steering characteristics suitable for various optical applications. The actuating platform sensor is a cost-effective and simple alternative method to study liquid dielectrophoresis without measuring the droplet contact angle. Furthermore, the unique configuration without any solid-solid contact offers a potential improvement for applications in optics, actuators, and other conventional microelectromechanical systems

Optical MEMS

Optical microelectromechanical systems (MEMS), microoptoelectromechanical systems (MOEMS), or optical microsystems are devices or systems that interact with light through actuation or sensing at a micro- or millimeter scale. Optical MEMS have had enormous commercial success in projectors, displays, and fiberoptic communications. The best-known example is Texas Instruments’ digital micromirror devices (DMDs). The development of optical MEMS was impeded seriously by the Telecom Bubble in 2000. Fortunately, DMDs grew their market size even in that economy downturn. Meanwhile, in the last one and half decade, the optical MEMS market has been slowly but steadily recovering. During this time, the major technological change was the shift of thin-film polysilicon microstructures to single-crystal–silicon microsructures. Especially in the last few years, cloud data centers are demanding large-port optical cross connects (OXCs) and autonomous driving looks for miniature LiDAR, and virtual reality/augmented reality (VR/AR) demands tiny optical scanners. This is a new wave of opportunities for optical MEMS. Furthermore, several research institutes around the world have been developing MOEMS devices for extreme applications (very fine tailoring of light beam in terms of phase, intensity, or wavelength) and/or extreme environments (vacuum, cryogenic temperatures) for many years. Accordingly, this Special Issue seeks to showcase research papers, short communications, and review articles that focus on (1) novel design, fabrication, control, and modeling of optical MEMS devices based on all kinds of actuation/sensing mechanisms; and (2) new developments of applying optical MEMS devices of any kind in consumer electronics, optical communications, industry, biology, medicine, agriculture, physics, astronomy, space, or defense

Process planning for thick-film mask projection micro stereolithography

Mask Projection micro Stereolithography (MPuSLA) is an additive manufacturing process used to build physical components out of a photopolymer resin. Existing MPuSLA technology cut the CAD model of part into slices by horizontal planes and the slices are stored as bitmaps. A layer corresponding to the shape of each bitmap gets cured. This layer is coated with a fresh layer of resin by lowering the Z-stage inside a vat holding the resin and the next layer is cured on top of it. In our Thick-film MPuSLA(TfMPuSLA) system, incident radiation, patterned by a dynamic mask, passes through a fixed transparent substrate to cure photopolymer resin. The existing MPuSLA fabrication models can work only for controlling the lateral dimension, without any control over the thickness of the cured part. The proposed process plan controls both the lateral dimensions and the thickness of profile of the cured part. In this thesis, a novel process planning for TfMPuSLA method is developed, to fabricate films on fixed flat substrate. The process of curing a part using this system is analytically modeled as the column cure model. It is different from the conventional process - layer cure model. Column means that a CAD model of part is discretized into vertical columns instead of being sliced into horizontal layers, and all columns get cured simultaneously till the desired heights. The process planning system is modularized into geometrical, chemical, optical, mathematical and physical modules and validated by curing test parts on our system. The thesis formulates a feasible process planning method, providing a strong basis for continued investigation of MPuSLA technology in microfabrication, such as micro lens fabrication.M.S.Committee Chair: Rosen, David W.; Committee Member: Das, Suman; Committee Member: Grover, Martha A

MEMS Technology for Biomedical Imaging Applications

Biomedical imaging is the key technique and process to create informative images of the human body or other organic structures for clinical purposes or medical science. Micro-electro-mechanical systems (MEMS) technology has demonstrated enormous potential in biomedical imaging applications due to its outstanding advantages of, for instance, miniaturization, high speed, higher resolution, and convenience of batch fabrication. There are many advancements and breakthroughs developing in the academic community, and there are a few challenges raised accordingly upon the designs, structures, fabrication, integration, and applications of MEMS for all kinds of biomedical imaging. This Special Issue aims to collate and showcase research papers, short commutations, perspectives, and insightful review articles from esteemed colleagues that demonstrate: (1) original works on the topic of MEMS components or devices based on various kinds of mechanisms for biomedical imaging; and (2) new developments and potentials of applying MEMS technology of any kind in biomedical imaging. The objective of this special session is to provide insightful information regarding the technological advancements for the researchers in the community

Statics and dynamics of electrothermal micromirrors

Adaptive and smart systems are growing in popularity as we shift toward personalization as a culture. With progressive demands on energy efficiency, it is increasingly important to focus on the utilization of energy in a novel way. This thesis investigates a microelectromechanical system (MEMS) mirror with the express intent to provide flexibility in solid state lighting (SSL). By coupling the micromirror to an optical source, the reflected light may be reshaped and directed so as to optimize the overall illumination profile. In addition, the light may be redirected in order to provide improved signal strength in visible light communications (VLC) with negligible impact on energy demands. With flexibility and full analog control in mind, the design of a fully integrated tip-tilt-piston micromirror with an additional variable focus degree of freedom is outlined. Electrothermal actuators are used to both steer the light and tune the focal length. A detailed discussion of the underlying physics behind composite beams and thermal actuators is addressed. This leads directly into an overview of the two main mirror components, namely the segmented mirror and the deflection actuators. An in-depth characterization of the dynamics of the mirror is discussed including the linearity of the thermal response. Frequency domain analysis of such a system provides insight into tunable mechanical properties such as the resonant frequency and quality factor. The degenerate resonant modes can be separated significantly. It is shown that the frequency response may be tuned by straining specific actuators and that it follows a predictable pattern. As a result, the system can be scanned at increasingly large angles. In other words, coupled mechanical modes allow variable damping and amplification. A means to determine the level of coupling is examined and the mode shape variations are tracked as a function of the tuning parameters. Finally, the applications of such a device are explored and tested. Such applications include reliable signal-to-noise ratio (SNR) enhancements in VLC of 30 dB and color tunable steerable lights using laser diodes. A brief discussion of the implications of dynamic illumination and tunable systems is juxtaposed with an explanation behind the integration of an electrothermal micromirror and an all digital driver

A Customer Programmable Microfluidic System

Microfluidics is both a science and a technology offering great and perhaps even revolutionary capabilities to impact the society in the future. However, due to the scaling effects there are unknown phenomena and technology barriers about fluidics in microchannel, material properties in microscale and interactions with fluids are still missing. A systematic investigation has been performed aiming to develop A Customer Programmable Microfluidic System . This innovative Polydimethylsiloxane (PDMS)-based microfluidic system provides a bio-compatible platform for bio-analysis systems such as Lab-on-a-chip, micro-total-analysis system and biosensors as well as the applications such as micromirrors. The system consists of an array of microfluidic devices and each device containing a multilayer microvalve. The microvalve uses a thermal pneumatic actuation method to switch and/or control the fluid flow in the integrated microchannels. It provides a means to isolate samples of interest and channel them from one location of the system to another based on needs of realizing the customers\u27 desired functions. Along with the fluid flow control properties, the system was developed and tested as an array of micromirrors. An aluminum layer is embedded into the PDMS membrane. The metal was patterned as a network to increase the reflectivity of the membrane, which inherits the deformation of the membrane as a mirror. The deformable mirror is a key element in the adaptive optics. The proposed system utilizes the extraordinary flexibility of PDMS and the addressable control to manipulate the phase of a propagating optical wave front, which in turn can increase the performance of the adaptive optics. Polydimethylsiloxane (PDMS) has been widely used in microfabrication for microfluidic systems. However, few attentions were paid in the past to mechanical properties of PDMS. Importantly there is no report on influences of microfabrication processes which normally involve chemical reactors and biologically reaction processes. A comprehensive study was made in this work to study fundamental issues such as scaling law effects on PDMS properties, chemical emersion and temperature effects on mechanical properties of PDMS, PDMS compositions and resultant properties, as well as bonding strength, etc. Results achieved from this work will provide foundation of future developments of microfluidics utilizing PDMS

Microfabrication of Organically Modified Ceramics for Bio-MEMS

A Bio-Micro-Electro-Mechanical-System (Bio-MEMS) is a miniaturized device that has mechanical, optical and/or electrical components for biomedical operations. High sensitivity, rapid response and integration capabilities are the main reasons for their attraction to researchers and adaptation of Bio-MEMS technology for many applications. Although the recent progress in microfabrication techniques has enabled a high degree of Bio-MEMS integration, many challenges remain. For example, extending the conventional cell monolayer cultures into 3D in vitro organ models often demands fabrication of round-cross sectional microstructures (microchannels and microwells) and integration of embedded metal-sensing elements. Owing to their low cost and the ease of the fabrication process, polymers have gained much attention in terms of biological microfluidic applications. Organically Modified Ceramics (ORMOCER) are hybrid inorganic-organic polymers, a new class of negative tone photoresist. Among polymers, ORMOCERs exhibit great potential with a view to biological microfluidic applications based on their inherent biocompatibility, transparency and mechanical stability. In this thesis, ORMOCER microfabrication methods were developed for implementation of optical, electrical and structural elements that are crucial for biological applications. A novel method, relying on controlled over-exposure of Ormocomp (a commercial formulation of ORMOCERs) was introduced for fabrication of tunable round cross-sectional microstructures, including microchannels (subprojects I-III) and microwells (subproject IV). Moreover, ORMOCER metallization was examined from the perspective of integration of embedded sensing elements (micromirrors and electrodes) into ORMOCER microfluidic channels to facilitate on-chip fluorescence (subprojects I and II) and electrochemical (subproject III) detection as well as electrical impedance spectroscopy (subproject IV). Metal adhesion, step coverage and bonding of embedded metal elements were addressed and new processes developed for various thin-film metals (subprojects III and IV). The round cross-sectional shape of the microchannel was exploited for implementation of thin-film reflective metal elements as concave micromirrors for optical detection of single cells, whereas the round shape of the microwells was applied to microfluidic three-dimensional (3D; spheroid) cell cultures. In addition to topography, the inherent surface properties of ORMOCERs were modified to allow for regulation of cell adhesion. As a result, cell monolayers (2D) and spheroids (3D) could be cultured side-by-side in a single microfluidic channel with non-invasive online impedance-based (monolayer) and optical monitoring (spheroids) of cell proliferation.Mikrovalmistustekniikat mahdollistavat sähkömekaanisten laitteiden miniatyrisoinnin biologisia ja lääketieteellisiä sovelluksia varten. Näistä laitteista käytetään yleisesti nimeä Bio-MEMS (engl. Bio-Micro-Electro-Mechanical-Systems). Bio-MEMS-laite koostuu mekaanisista, sähköjohtavista ja/tai optisista komponenteista, jotka mahdollistavat esimerkiksi soluviljelyn, lääkeaineiden kontrolloidun annostelun soluviljelmiin ja tutkittavien aineiden pitoisuuksien mittaamisen kemiallisesti mikrofluidistiikan avulla. Vaikka Bio-MEMS-laitteet ovat viime vuosina kehittyneet valtavin harppauksin, on mikrovalmistustekniikoissa ja materiaaleissa vielä paljon kehitettävää. Polymeeripohjaiset materiaalit ovat verrattain edullisia ja niiden valmistusprosessit suoraviivaisia, minkä vuoksi polymeereja käytetään paljon biologisissa mikrofluidistiikan sovelluksissa. Monet sovellukset, kuten 3D-solumallien kasvatus, edellyttävät pyöreäpohjaisia rakenteita ja mitta-antureiden yhdistämistä. Erityisesti pyöreäpohjaisten mikrorakenteiden valmistaminen on usein hidasta ja vaatii useita eri työvaiheita. Myös polymeerimateriaalien metallointi (anturien yhdistäminen) vaatii räätälöityjä mikrovalmistusmenetelmiä. Tässä työssä kehitettiin uusia mikrovalmistusmenetelmiä kaupalliselle ORMOCER-polymeerille (engl. organically modified ceramics), joka on luonnostaan bioyhteensopiva, läpinäkyvä ja mekaanisesti kestävä epäorgaaninen-orgaaninen hybridimateriaali. Työn ensimmäisessä osassa kehitettiin uusi yksivaiheinen litografinen menetelmä poikkileikkaukseltaan pyöreiden mikrorakenteiden, kuten mikrokanavien ja -kuoppien, valmistamiseen. Työn toisessa osassa kehitettiin ORMOCER-polymeerin metallointimenetelmiä, jotka mahdollistavat muun muassa mikropeilien ja sähköisten elektrodien yhdistämisen ORMOCER-polymeeristä valmistettuihin mikrokanaviin. Mikropeilien avulla on mahdollista parantaa optisen detektion herkkyyttä esimerkiksi yhden solun analytiikassa (osajulkaisu I) tai pienmolekyylien elektroforeettisessa erotuksessa (osajulkaisu II). Vastaavasti sähköisten elektrodien avulla voidaan mitata esimerkiksi pienmolekyylien pitoisuuksia amperometrisesti (osajulkaisu III) tai solujen jakautumista impedanssispektrosopiaan perustutuen (osajulkaisu IV). Lisäksi havaittiin, että ORMOCER-polymeerin pintaominaisuuksia muokkaamalla on mahdollista kontrolloida solujen polymeeripinnalle, mikä mahdollisti solujen kasvattamisen vierekkäin sekä perinteisenä viljelmänä (2D, soluyhteensopiva ja tasainen pinta) että sferoideina (3D, soluja hylkivä, pyöreäpohjainen pinta) samassa mikrofluidistisessa kanavassa

Microelectromechanical Systems and Devices

The advances of microelectromechanical systems (MEMS) and devices have been instrumental in the demonstration of new devices and applications, and even in the creation of new fields of research and development: bioMEMS, actuators, microfluidic devices, RF and optical MEMS. Experience indicates a need for MEMS book covering these materials as well as the most important process steps in bulk micro-machining and modeling. We are very pleased to present this book that contains 18 chapters, written by the experts in the field of MEMS. These chapters are groups into four broad sections of BioMEMS Devices, MEMS characterization and micromachining, RF and Optical MEMS, and MEMS based Actuators. The book starts with the emerging field of bioMEMS, including MEMS coil for retinal prostheses, DNA extraction by micro/bio-fluidics devices and acoustic biosensors. MEMS characterization, micromachining, macromodels, RF and Optical MEMS switches are discussed in next sections. The book concludes with the emphasis on MEMS based actuators

A new method of temporal phase shifting using principle of stroboscopy for characterizing microstructures

Temporal Phase Shifting Interferometry is the most common method for characterization of surface, profile and displacement properties of micro devices. Common methods of phase shifting require PZT based devices that have inherent errors due to non-linearity. To avoid these errors during phase shifting, a new phase shifting technique is presented in this work. A detailed analysis of the temporal phase shifting technique was performed and an optimized methodology for phase shifting was also established. This technique utilizes the advantage of stroboscopic interferometry to create phase shifted images without requiring any component for phase shifting. The feasibility of the proposed method of phase shifting was demonstrated using the developed Acoustic-Optic Modulated Stroboscopic Interferometer (AOMSI) on simple 1D and 2D micro structures designed specifically for this purpose. The proposed method was used for surface profiling and static characterization of the microstructures. Experiments were performed on microcantilevers in order to extract the curvature of the device due to residual stress on it. The same device was tested under a commercial surface profiler with 1Å resolution and the results were found to be in good agreement with the results from the proposed technique. Static characterization was performed to identify the tip deflection and profile variation of the microcantilever in response to various DC voltages. A capacitor-based cantilever was tested under varied electrostatic loads and the deflection of the cantilever was extracted using the proposed method. The deflection of the cantilever was predicted using a theoretical model based on energy method. Static characterization results from the proposed technique were found to be in good agreement with the predicted results. To extend the applicability of this technique without affecting the spatial resolution for micro devices larger than the field of view of the interferometer, stitching method was proposed and three different stitching configurations were also presented. The same device was tested in full-field of view under the commercial profiler. Good agreement between the result of presented stitching methods and commercial profiler demonstrates the reliability of the presented methods for stitching large structures