64 research outputs found

    Optical MEMS

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    Control and Characterization of Line-Addressable Micromirror Arrays

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    This research involved the design and implementation of a complete line-addressable control system for a 32x32 electrostatic piston-actuated micromirror array device. Line addressing reduces the number of control lines from N2 to 2N making it possible to design larger arrays and arrays with smaller element sizes. The system utilizes the electromechanical bi-stability of individual elements to bold arbitrary bi-stable phase patterns. The control system applies pulse width modulated (PWM) signals to the rows and columns of the micromirror array. Three modes of operation were conceived and built into the system. The first was the traditional signal scheme which requires the array to be reset before a new pattern can be applied. The second is an original scheme that allows dynamic switching between bi-stable patterns. The third and final mode applies an effective voltage ramp across the device by operating above mechanical cutoff. Device characterization and control system testing were conducted on predesigned and prefabricated samples from two different foundry processes. Testing results showed that the control system was successfully integrated. However, bi-stable control of individual mirror elements was not successfully demonstrated on samples due to flaws in the device design. A more robust device design which corrects these flaws and increases operational yield is proposed

    FLEXIBLE LOW-COST HW/SW ARCHITECTURES FOR TEST, CALIBRATION AND CONDITIONING OF MEMS SENSOR SYSTEMS

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    During the last years smart sensors based on Micro-Electro-Mechanical systems (MEMS) are widely spreading over various fields as automotive, biomedical, optical and consumer, and nowadays they represent the outstanding state of the art. The reasons of their diffusion is related to the capability to measure physical and chemical information using miniaturized components. The developing of this kind of architectures, due to the heterogeneities of their components, requires a very complex design flow, due to the utilization of both mechanical parts typical of the MEMS sensor and electronic components for the interfacing and the conditioning. In these kind of systems testing activities gain a considerable importance, and they concern various phases of the life-cycle of a MEMS based system. Indeed, since the design phase of the sensor, the validation of the design by the extraction of characteristic parameters is important, because they are necessary to design the sensor interface circuit. Moreover, this kind of architecture requires techniques for the calibration and the evaluation of the whole system in addition to the traditional methods for the testing of the control circuitry. The first part of this research work addresses the testing optimization by the developing of different hardware/software architecture for the different testing stages of the developing flow of a MEMS based system. A flexible and low-cost platform for the characterization and the prototyping of MEMS sensors has been developed in order to provide an environment that allows also to support the design of the sensor interface. To reduce the reengineering time requested during the verification testing a universal client-server architecture has been designed to provide a unique framework to test different kind of devices, using different development environment and programming languages. Because the use of ATE during the engineering phase of the calibration algorithm is expensive in terms of ATE’s occupation time, since it requires the interruption of the production process, a flexible and easily adaptable low-cost hardware/software architecture for the calibration and the evaluation of the performance has been developed in order to allow the developing of the calibration algorithm in a user-friendly environment that permits also to realize a small and medium volume production. The second part of the research work deals with a topic that is becoming ever more important in the field of applications for MEMS sensors, and concerns the capability to combine information extracted from different typologies of sensors (typically accelerometers, gyroscopes and magnetometers) to obtain more complex information. In this context two different algorithm for the sensor fusion has been analyzed and developed: the first one is a fully software algorithm that has been used as a means to estimate how much the errors in MEMS sensor data affect the estimation of the parameter computed using a sensor fusion algorithm; the second one, instead, is a sensor fusion algorithm based on a simplified Kalman filter. Starting from this algorithm, a bit-true model in Mathworks Simulink(TM) has been created as a system study for the implementation of the algorithm on chip

    DESIGN AND FABRICATION OF MEMS ELECTROSTATIC ACTUATORS

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    The research presented in this thesis is focused on the design and development of MEMS (Micro Electro Mechanical System) electrostatic actuators. Different kinds of electrostatic actuators are analyzed and presented . The study of torsional electrostatic actuator is carried out and the design of an micromirrors array for beam steering optical switching in a thick polysilicon technology is presented. The main advantage of these devices is that they are realized in a commercial surface micromachining technology (THELMA by STMicrolectronics) hence they are less expensive with respect to other solutions present in literature. For the torsional actuators, a novel semi-analytical model which allows prediction of the behaviour of the structures and takes into account the flexural deformation of the structure is presented. A very good agreement between the model, FEM simulation and experimental results has been obtained. The possibility of using another competitive surface micromachining technology (developed at IMEC) which uses poly silicon germanium as structural layer to realize the micromirrors is also investigated. Poly Silicon Germanium has the advantage that can be integrated on top of commercial CMOS. The development of optimized (low stressed) layers of poly silicon germanium has been addressed and some test micromirrors using this technology have been designed. Moreover an analysis of the levitation effect in electrostatic comb fingers atcuators is presented. The use of this actuation for vertical or torsional motion of micromachined structures is exploited. Two different levitational mechanical resonators have been designed and fabricated in THELMA. Because of the high thickness of the structural layer, classic springs shows several limitation, so specifically designed suspension springs (rotated serpentines), with better performance for high thickness, have been used. A full analysis of this kind of spring and a comparison with other springs are also presented. Finally a study of the dependence of the levitation force intensity on the geometric parameters of the actuators is performed using FEM simulations, and information about critical geometrical parameters in the design of operative levitational actuators is obtained. The devices are characterized and the obtained results are compared with FEM simulations

    New Formulation for Finite Element Modeling Electrostatically DrivenMicroelectromechanical Systems

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    The increased complexity and precision requirements of microelectromechanical systems(MEMS) have brought about the need to develop more reliable and accurate MEMS simulation tools. To better capture the physical behavior encountered, several finite elementanalysis techniques for modeling electrostatic and structural coupling in MEMS devices havebeen developed in this project. Using the principle of virtual work and an approximationfor capacitance, a new 2-D lumped transducer element for the static analysis of MEMS hasbeen developed. This new transducer element is compatible to 2-D structural and beamelements. A novel strongly coupled 3-D transducer formulation has also been developed tomodel MEMS devices with dominant fringing electrostatic fields. The transducer is compatible with both structural and electrostatic solid elements, which allows for modeling complexdevices. Through innovative internal morphing capabilities and exact element integrationthe 3-D transducer element is one of the most powerful coupled field FE analysis tools available. To verify the accuracy and effectiveness of both the 2-D and 3-D transducer elements a series of benchmark analyses were conducted. More specifically, the numerically predicted results for the misalignment of lateral combdrive fingers were compared to available analytical and modeling techniques. Electrostatic uncoupled 2-D and 3-D finite element models werealso used to perform energy computations during misalignment. Finally, a stability analysisof misaligned combdrive was performed using a coupled 2-D finite element approach. Theanalytical and numerical results were compared and found to vary due to fringing fields

    MEMS Technology for Biomedical Imaging Applications

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    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

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    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

    MEMS based catheter for endoscopic optical coherence tomography

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    Ph.DDOCTOR OF PHILOSOPH

    Micro-Resonators: The Quest for Superior Performance

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    Microelectromechanical resonators are no longer solely a subject of research in university and government labs; they have found a variety of applications at industrial scale, where their market is predicted to grow steadily. Nevertheless, many barriers to enhance their performance and further spread their application remain to be overcome. In this Special Issue, we will focus our attention to some of the persistent challenges of micro-/nano-resonators such as nonlinearity, temperature stability, acceleration sensitivity, limits of quality factor, and failure modes that require a more in-depth understanding of the physics of vibration at small scale. The goal is to seek innovative solutions that take advantage of unique material properties and original designs to push the performance of micro-resonators beyond what is conventionally achievable. Contributions from academia discussing less-known characteristics of micro-resonators and from industry depicting the challenges of large-scale implementation of resonators are encouraged with the hopes of further stimulating the growth of this field, which is rich with fascinating physics and challenging problems
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