Bipolar Driving for Displacement Accuracy Improvement of Electrostatic Microactuator

A bipolar driving technique is presented to improve the displacement accuracy of an electrostatic microactuator at the submicron scale. A lateral comb-type electrostatic actuator with a full stroke of 34 µm is fabricated. Owing to the charging inside the device, the displacement error reaches a maximum of 1 µm when a DC driving voltage is applied. The displacement error reduces when a 1 Hz bipolar square wave driving voltage with the same magnitude is applied instead of a monopolar DC signal. The maximum fluctuation is reduced to 0.25 µm. The proposed driving technique, which is simple and does not require additional components or control systems, is effective for controlling the gap in nanophotonics.