Modeling, fabrication and demonstration of an electrostatic actuator with a coplanar pre-charged electrode

Abstract

We present the modeling, fabrication and measurement results of a novel electrostatic actuator with a coplanar pre-charged electrode. Different from the conventional electrostatic actuator, the pull-in voltage of the proposed actuator can be freely controlled even after fabrication by inducing charges prior to use in the auxiliary electrode right next to the actuation electrode. To investigate the static and dynamic characteristics of the proposed actuator, analytical models were first developed on the basis of a parallel-plate capacitor model. We then successfully designed, fabricated, and evaluated a micro-switch with a fixed-fixed beam and a coplanar pre-charged electrode. By properly introducing a dimple structure, the pull-in voltage of the fabricated micro-switch was reduced from 71.2 V to 6.8 V when pre-charged by 58.8 V. The resonant frequency of the fabricated micro-switch was 84.8% of the initial resonant frequency when the reduced pull-in voltage of the device was half of the original pull-in voltage. These measurement results were compared with those from the analytical models and FEM simulation, showing deviations of less than 12%. This work can favorably be adapted and used in designing an electrostatic micro-switch since the proposed switch can remarkably reduce the pull-in voltage as desired without notable performance degradation.