Dynamics of polysilicon parallel-plate electrostatic actuators

The response of a polysilicon parallel-plate electrostatic actuator to a.c. signals at different bias voltages has been measured with a laser interferometer. Using microhinges, large plates (with areas from 100 mu m(2) to approximate to 0.1 mm(2)) with long thin support beams (such as 600 mu m X 3 mu m X 1.5 mu m) are rotated off the surface of the substrate to form a parallel-plate capacitor. Fabricated structures having 100 mu m gaps can be closed electrostatically with voltages as low as 50 V. This new actuator is estimated to output a force of up to 50 mu N. With the exception of the resonant Q-value, the experimental results are in good agreement with simulations based on a simple nonlinear model for the actuator.