A MEMS electret generator with electrostatic levitation for vibration-driven energy-harvesting applications

Abstract

In this paper, we propose a passive gap-spacing control method in order to avoid stiction between top and bottom structures in in-plane sensor/actuator/generator applications. A patterned electret using a high-performance perfluoro polymer material is employed to induce a repulsive electrostatic force. An out-of-plane repulsive force is successfully demonstrated with our early prototype, in both air and liquid. By using the present electret-based levitation method to keep the air gap, a MEMS electret generator has been developed for energy-harvesting applications. A dual-phase electrode arrangement is adopted in order to reduce the horizontal electrostatic damping force. With the present prototype, about 0.5 μW is obtained for both phases of the generator, resulting in a total power output of 1.0 μW at an acceleration of 2 g with 63 Hz. With our electromechanical model of the generator, we have confirmed that the model can mimic the response of the generator prototype.

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“…Electrostatic conversion requires initial charges on the electrodes. Electret-based harvesters [25] provide a solution, in which the material is only charged once during fabrication with a high voltage, but the capacity of harvesting energy is still limited by the magnitude of capacitance that can be achieved and by the charge density of electrets. Electromagnetic transduction uses the relative motion between coils and magnets.…”

New DRIE-Patterned Electrets for Vibration Energy Harvesting

“…While it is quite easy to pattern organic electrets [4,9], the same action on inorganic materials is much more difficult …”

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“…[1][2][3][4] The main transduction mechanisms can be divided in three groups: electromagnetic, 5 electrostatic, 6 and piezoelectric. [7][8][9] Among these transduction mechanisms, the piezoelectric transduction has attracted the most interest due to its high power density and simple structure.…”