Design of Electrostatic Actuators for MOEMS Applications

We propose a novel method for pull-in analysis in electrostatic actuation. In this method, pull-in angle can be found once the capacitance of electrodes is calculated as a function of rotation angle. This is based on our theory, which is that the pull-in angle only depends on the capacitance but not on spring constants or applied voltage. The theory is derived analytically and its limit of application is described as well. These theory and method can be applied to the translational motion case in the similar fashion. With the proposed method, the computation time can be reduced considerably since it deals with only one domain rather than executing coupled-domain analysis. This method can be used more effectively where the complexity of electrode structures or spring shape is more severe. By way of example, it is applied to the design of three different types of actuators: parallel-plate torsion mirrors, staggered vertical comb-drives, and scanning micromirror with hidden vertical comb-drives. The theoretical results are compared with experimental data as well.