An Analytical Model for Repulsive Electrostatic Microactuator Using a Conformal Mapping Technique

Document Type : Original Article

Authors

Faculty of Engineering, Alexandria University, Egypt.

Abstract

Electrostatic microactuators are able to produce a repulsive force in the out-ofplane direction. The electrostatic microactuators use an asymmetric electric field surrounding the top and bottom surfaces of the moving fingers to produce a repulsive force. The displacement of moving finger is not limited by the “pull-in” effect. In addition, the usage of a repulsive force leads to the elimination of the sticking problem. In this paper, an analytical model for the repulsive-force, and the fringe capacitance of a microactuator is developed putting the moving plate thickness in consideration using conformal mapping techniques. With this technique, electric field lines are geometrically approximated to separately model the different capacitive components. These components are finally combined to obtain the equivalent fringe capacitance. The model reveals the maximum out-of-plane displacement. Rules are derived based on the analytical model for tuning and optimization of the microactuator performance. Simulations are conducted to verify the analytical model. In addition, the mechanism for generating the repulsive force is explained.

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