A Low Voltage Electrostatic Micro Actuator for Large Out-of-Plane Displacement

Towfighian, Shahrzad; He, Siyuan; Mrad, Ridha

doi:10.1115/detc2014-34283

Cited by 8 publications

(4 citation statements)

References 13 publications

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“…Because of recent advances in ASIC designs, high DC voltages can be easily produced. In applications where high voltages are of concern, however, the required actuating voltage can be reduced by reducing the width of the beam and lateral spacing of the fixed electrodes [18]. Multiple beams can be used in conjunction with each other, similar to a comb-drive, to further reduce the driving voltage.…”

Section: Introductionmentioning

confidence: 99%

A Tunable Electrostatic MEMS Pressure Switch

Pallay

Miles

Towfighian

2020

IEEE Trans. Ind. Electron.

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We demonstrate a tunable air pressure switch. The switch detects when the ambient pressure drops below a threshold value and automatically triggers without the need for any computational overhead to read the pressure or trigger the switch. The switch exploits the significant fluid interaction of a MEMS beam undergoing a large oscillation from electrostatic levitation to detect changes in ambient pressure. If the oscillation amplitude near the resonant frequency is above a threshold level, dynamic pullin is triggered and the switch is closed. The pressure at which the switch closes can be tuned by adjusting the voltage applied to the switch. The use of electrostatic levitation allows the device to be released from their pulledin position and reused many times without mechanical failure. A theoretical model is derived and validated with experimental data. It is experimentally demonstrated that the pressure switching mechanism is feasible.

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Section: Introductionmentioning

confidence: 99%

A Tunable Electrostatic MEMS Pressure Switch

Pallay

Miles

Towfighian

2020

IEEE Trans. Ind. Electron.

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“…The force is induced by the asymmetric electrostatic field of the moving and fixed fingers. A MEMS actuator using repulsive force is a widely studied subject in literature [35][36][37][38]. However, it has been used for only actuation mechanisms.…”

Section: Model Description and Operation Principle Electrostatic Actumentioning

confidence: 99%

A MEMS Microphone Using Repulsive Force Sensors

Ozdogan

Towfighian

2016

Volume 4: 21st Design for Manufacturing and the Life Cycle Conference; 10th International Conference on Micro- And Nanosystems

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We present a MEMS microphone that converts the mechanical motion of a diaphragm, generated by acoustic waves, to an electrical output voltage by capacitive fingers. The sensitivity of a microphone is one of the most important properties of its design. The sensitivity is proportional to the applied bias voltage. However, it is limited by the pull-in voltage, which causes the parallel plates to collapse and prevents the device from functioning properly. The presented MEMS microphone is biased by repulsive force instead of attractive force to avoid pull-in instability. A unit module of the repulsive force sensor consists of a grounded moving finger directly above a grounded fixed finger placed between two horizontally seperated voltage fixed fingers. The moving finger experiences an asymmetric electrostatic field that generates repulsive force that pushes it away from the substrate. Because of the repulsive nature of the force, the applied voltage can be increased for better sensitivity without the risk of pull-in failure. To date, the repulsive force has been used to engage a MEMS actuator such as a micro-mirror, but we now apply it for a capacitive sensor. Using the repulsive force can revolutionize capacitive sensors in many applications because they will achieve better sensitivity. Our simulations show that the repulsive force allows us to improve the sensitivity by increasing the bias voltage. The applied voltage and the back volume of a standard microphone have stiffening effects that significantly reduce its sensitivity. We find that proper design of the back volume and capacitive fingers yield promising results without pull-in instability.

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“…The nature of the electrostatic levitation force is completely different from the electrostatic force in parallel-plate capacitors, where the moving electrode is pulled toward the bottom electrode [13]. The levitation electrode configuration allows for a large vibration of the moving electrode [14] and does not suffer from the pullin instability between the moving and bottom electrodes [15][16][17]. Furthermore, it provides the flexibility to increase the bias voltage to increase sensitivity in sensing applications [18].…”

Section: Introductionmentioning

confidence: 99%

“…For some applications such as instrumentation devices, the use of high bias voltage is not of concern. In applications where the use of high bias voltages is of concern, the dimensions of the electrodes could be changed to make the use of low bias voltages feasible [14].…”

Section: Introductionmentioning

confidence: 99%

Feasibility study of a micro-electro-mechanical-systems threshold-pressure sensor based on parametric resonance: experimental and theoretical investigations

Pallay¹,

Daeichin²,

Towfighian³

2020

J. Micromech. Microeng.

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A tunable threshold pressure sensor based on parametric resonance of a microbeam subjected to electrostatic levitation is proposed. Parametric excitation can trigger a large amplitude vibration at twice the natural frequency if the magnitude of the driving force is large enough to overcome energy loss mechanisms in the system such as squeeze film damping. This causes a temporarily unstable response with a significant gain in oscillation amplitude over time until it is eventually capped by nonlinearities in the force or material or geometric properties. The instability divides the frequency region into two regions: distinct responses bounded by the system non-linearity, and trivial responses with very low oscillation amplitudes. It is shown experimentally that the appearance of parametric resonance depends on the pressure, which influences the amount of energy loss from squeeze film damping. Therefore, the distinct difference in the vibration amplitude can be used to detect when the pressure passes a threshold level. The activation of parametric resonance also depends on the amplitude of the driving force ( V ac ). This voltage amplitude can be set to trigger parametric resonance when the pressure drops below a predetermined threshold. A reduced-order model is developed using the Euler–Bernoulli beam theory to elucidate the non-linear dynamics of the system. The simulation results from the mathematical model are in good agreement with the experimental data. The advantages of the proposed sensor over pull-in based sensors are its reliability and improved resolution from a large signal-to-noise ratio.

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A Low Voltage Electrostatic Micro Actuator for Large Out-of-Plane Displacement

Cited by 8 publications

References 13 publications

A Tunable Electrostatic MEMS Pressure Switch

A Tunable Electrostatic MEMS Pressure Switch

A MEMS Microphone Using Repulsive Force Sensors

Feasibility study of a micro-electro-mechanical-systems threshold-pressure sensor based on parametric resonance: experimental and theoretical investigations

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