Design of an electrostatic repulsive-force based vertical micro actuator

Micro actuators using electrostatic repulsive-force induced by asymmetric electric field have no the problem of pull-in instability existing in electrostatic attractive-force based micro actuators, and their stroke is not limited by the initial gap between electrodes. In this paper, an improved structure of micro actuator based on electrostatic repulsive-force is presented to achieve a large vertical stroke without penalties of large actuation voltage and additional insulation layer. Numerical simulations are performed to investigate the relationship between the repulsive-force and the structural parameters. Simulation results show that the repulsive-force is highly dependent on finger width, finger distance and finger thickness rather than initial gap between movable and fixed fingers. Numerical simulation predicts that the repulsive-force based vertical micro actuator can achieve a stroke of 4 μm at a driving voltage of 78 V.