An out-of-plane electrostatic actuator based on the lever principle

Abstract

A MEMS electrostatic actuator based on the lever principle, which aims to obtain a large out-of-plane displacement and has a simple structure and fabrication process is presented in this paper. The two-layer lever actuator consists of four individual levers, each of which is actuated by electrostatic attractive force to produce a downward displacement on the short arm of the lever. This displacement is amplified by the lever to achieve a larger upward displacement on the end of the long arm. A theoretical model of the lever actuator is brought forward, based on the energy method, and is verified by finite-element analysis. The discussions about the key factors related to the characteristics of the structure are also included, from which we acquired the structure parameters for fabrication. Compared with previous studies, the theoretical model and the detailed discussions make the analysis of the out-of-plane actuator based on the lever principle more general. An electrostatic actuator 503 × 503 µm with a central mass of 40 × 40 µm is fabricated using a two-layer surface fabrication process. The measured out-of-plane displacement is about 1.45 µm at a voltage of 47 V; more than double the displacement of a conventional electrostatic attractive parallel plate actuator by the same fabrication process. The possible applications of this actuator are micro-switches, micro-capacitors and micro-mirrors in optical communication and adaptive optics systems.