2,588 research outputs found

    Casimir forces on a silicon micromechanical chip

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    Quantum fluctuations give rise to van der Waals and Casimir forces that dominate the interaction between electrically neutral objects at sub-micron separations. Under the trend of miniaturization, such quantum electrodynamical effects are expected to play an important role in micro- and nano-mechanical devices. Nevertheless, utilization of Casimir forces on the chip level remains a major challenge because all experiments so far require an external object to be manually positioned close to the mechanical element. Here, by integrating a force-sensing micromechanical beam and an electrostatic actuator on a single chip, we demonstrate the Casimir effect between two micromachined silicon components on the same substrate. A high degree of parallelism between the two near-planar interacting surfaces can be achieved because they are defined in a single lithographic step. Apart from providing a compact platform for Casimir force measurements, this scheme also opens the possibility of tailoring the Casimir force using lithographically defined components of non-conventional shapes

    EXTREME VERTICAL DISPLACEMENT, HIGH FORCE, SILICON MICROSTAGE ZIPPER ACTUATORS

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    Large vertical deflection, high force microactuators are desired in MEMS for a variety of applications. This thesis details a novel large-displacement electrostatic "zipper" microactuator capable of achieving hundreds of microns of out-of-plane deflection and delivering high forces, fabricated entirely from SOI (silicon-on-insulator). This technology is novel in its use of SiO2 as both a high quality dielectric and the stressed layer of the bimorph. Geometries are explored analytically, numerically and experimentally to provide the greatest electromechanical output while constraining the device footprint to 1mm2. Device performance was benchmarked against previously established out-of-plane microactuators. We report the first instance of zipper-inspired electrostatic "microstage" actuators whose flat center stage and vertical actuation mode is ideal for carrying and moving a load. Fabricated microstages are capable of achieving out-of-plane deflections up to 1.2 mm, force outputs up to 1 mN, pull-in voltage as low as 20 V, and switching times of 1 ms

    Toward a Flying MEMS Robot

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    The work in this thesis includes the design, modeling, and testing of motors and rotor blades to be used on a millimeter-scale helicopter style flying micro air vehicle (MAV). Three different types of motor designs were developed and tested, which included circular scratch drives, electrostatic motors, and comb drive resonators. Six different rotor designs were tested; five used residual stress while one design used photoresist to act as a hinge to achieve rotor blade deflection. Two key parameters of performance were used to evaluate the motor and rotor blade designs: the frequency of motor rotation and the angle of deflection achieved in the rotor blades. One successful design utilized a scratch drive motor with four attached rotor blades to try to achieve lift. While the device rotated successfully, the rotational frequency was insufficient to achieve lift-off. The electrostatic motor designs proved to be a challenge, only briefly moving before shorting out; nonetheless, lessons were learned. Comb drive designs operated over a wide range of high frequencies, lending them to be a promising method of turning a rotary MAV. None of the fabricated devices were able to achieve lift, due to insufficient rotational rates and low angles of attack on the rotor blades. With slight modifications to the current designs, the required rotational rates and rotor blade deflections would yield a viable MAV. The ultimate objective of this effort was to create an autonomous MAV on the millimeter scale, able to sense and act upon targets in its environment. Such a craft would be virtually undetectable, stealthily maneuvering and capable of precision engagement

    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

    Electrostatic curved electrode actuators

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    This paper presents the design and performance of an electrostatic actuator consisting of a laterally compliant cantilever beam and a fixed curved electrode, both suspended above a ground plane. A theoretical description of the static behavior of the cantilever as it is pulled into contact with the rigid fixed-electrode structure is given. Two models are presented: a simplified semi-analytical model based on energy methods, and fully three-dimensional (3-D) coupled electromechanical numerical simulations using CoSolve-EM. The two models are in qualitative agreement with each other, and predict stable actuator behavior when the beam deflection becomes constrained by the curved electrode geometry before electrostatic pull-in can occur. The pull-in behavior depends on the shape of the curved electrode. Test devices have been fabricated by polysilicon surface micromachining techniques. Experimental results confirm the basic theoretical results. Stable behavior with relatively large displacements and forces can be generated by these curved electrode actuators. Depending on the design, or as a result of geometrical imperfections, regions of unstable (pull-in) deflection behavior are also observe

    MEMS-enabled silicon photonic integrated devices and circuits

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    Photonic integrated circuits have seen a dramatic increase in complexity over the past decades. This development has been spurred by recent applications in datacenter communications and enabled by the availability of standardized mature technology platforms. Mechanical movement of wave-guiding structures at the micro- and nanoscale provides unique opportunities to further enhance functionality and to reduce power consumption in photonic integrated circuits. We here demonstrate integration of MEMS-enabled components in a simplified silicon photonics process based on IMEC's Standard iSiPP50G Silicon Photonics Platform and a custom release process

    Design and simulation of a direct and indirect drive electrostatically actuated resonant micro-mirrors for scanner applications

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    Laser scanners have been an integral part of MEMS research for more than three decades. The demand for electrostatically actuated scanning micro-mirrors have been growing in the last decade, mainly for pico-projection and medical applications. These type of actuation wins over others, because it provides long-term stability, size advantages and fabrication schemes which are easier to render CMOS compatibility. The growing field in softwares capable of design and simulate MEMS devices, have been a crucial help for engineers, which are limited to a few of them and still cost huge amount of time. MEMS+Âź is a software platform that provides simulation results up to 100 times faster than conventional finite element analysis tools and allows to integrate designs in MathWorksÂź. In this work two types of electrostatically actuated scanning micro-mirrors were designed and simulated using both MEMS+Âź and MathWorksÂź, one is a direct drive micro-mirror and the other an indirect drive micro-mirror. In the first the torque is imparted directly from the actuation mechanism to the frame containing the mirror, and in the second the resonance mode amplifies a small motion in a larger mass to a considerably larger motion in the smaller mirror. Regarding the direct-drive micro-mirror, the presented work mainly shows the reliability of MEMS+Âź compared to other softwares. The indirect drive one, is a state-of-art solution for high frequency electrostatically actuated micro-mirrors, and all the simulations taken on it were aimed to verify itÂŽs behaviour, and then proceed with the microfabrication step. The target microfabrication technology is SOIMUMPs

    Electrostatic repulsive out-of-plane actuator using conductive substrate

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    abstract: A pseudo-three-layer electrostatic repulsive out-of-plane actuator is proposed. It combines the advantages of two-layer and three-layer repulsive actuators, i.e., fabrication requirements and fill factor. A theoretical model for the proposed actuator is developed and solved through the numerical calculation of Schwarz-Christoffel mapping. Theoretical and simulated results show that the pseudo-three-layer actuator offers higher performance than the two-layer and three-layer actuators with regard to the two most important characteristics of actuators, namely, driving force and theoretical stroke. Given that the pseudo-three-layer actuator structure is compatible with both the parallel-plate actuators and these two types of repulsive actuators, a 19-element two-layer repulsive actuated deformable mirror is operated in pseudo-three-layer electrical connection mode. Theoretical and experimental results demonstrate that the pseudo-three-layer mode produces a larger displacement of 0–4.5 Όm for a dc driving voltage of 0–100 V, when compared with that in two-layer mode.The final version of this article, as published in Scientific Reports, can be viewed online at: https://www.nature.com/articles/srep3511

    Parametric Resonance of a Repulsive Force MEMS Electrostatic Mirror

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    We investigate the nonlinear dynamic behavior of an electrostatic MEMS mirror. The MEMS mirror is driven by repulsive force actuators, which avoid pull-in instability and enable large travel ranges. In parallel-plate actuators, the force on the structure is toward the substrate limiting the range of motion to the capacitor gap. Unlike parallel-plate, repulsive force actuators push the mirror away from the substrate not limiting the motion. The highly nonlinear nature of the repulsive force and the large motions create unique characteristics that dier from parallel-plate actuators. Repulsive force actuators show linear natural frequency hardening with increased DC voltages unlike parallel-plate ones that have frequency softening. A large parametric resonance is another attribute of repulsive force actuators as the limitations of a small gap and pull-in instability are eliminated. To simulate the system response, we use a lumped parameter model with linear and cubic stiness modulated by the excitation voltage that causes parametric resonances. Using the shooting technique, we obtained simulations that agree well with the nonlinear responses observed in our experiments. As the limitation of a small gap is overcome, the electrostatic force triggers large principal parametric resonances with amplitudes as large as the primary resonance. The parametric resonance is more pronounced at low DC excitation levels when geometric nonlinearities are not significant (axial stress is low). While the initial gap is only 2 microns, under parametric resonance, our one-millimeter diameter mirror reaches 43 m at 1.2 KHz when the excitation level is as low as VDC = 40 V; VAC = 1 V in a vacuum. The ability to achieve parametric resonances with repulsive force actuation can serve and improve the signal-to-noise ratio and speed in various applications such as confocal microscopy
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