A LOW VOLTAGE ELECTROSTATIC MICRO ACTUATOR FOR LARGE OUT-OF-PLANE DISPLACEMENT

摘要

An electrostatic actuator is designed to move a 1 mm mirror, 58 μm out of plane at 25 volts. Large out-of-plane displacement is obtained from repulsive forces generated on four sets of comb drive fingers attached to the mirror plate in the middle. The proposed actuator is a customized design of a previous study for low voltage applications. The static modeling of the actuator was performed using a coupled-field finite element model of the actuator, including mechanical and electrical domains. Low voltage operation is achieved by decreasing the finger width and the lateral spacing, which increased the generated repulsive force at a specified voltage in a unit cell of the actuator. Decreasing the lateral spacing also enabled increasing the number of fingers, which could increase the repulsive-force, and consequently the torque and the rotation angles when the vertical gap between moving and fixed fingers is small. However, the redesigned actuator has a lower stiffness compared to the previous design. The actuator is optimized for auto-focusing applications in cellphone cameras that require voltages below 30 Volts for user safety. In the intended auto-focusing module, the actuators do not carry the lens and auto-focusing is obtained by moving the mirror attached to the actuators.