Computational study of variations in gap size for the electrostatic levitating force of MEMS device using dual BEM

For MEMS combdrive performance, the calculation of levitating force due to electrostatic field is very important, and an accurate electrostatic analysis is essential. Because the gap size between combdrive fingers and ground plane or movable finger and fixed finger, plays a very important role for levitation, a study of the effect of gap size variation is indispensable. For diverse gaps of MEMS comdrive design, the dual BEM (DBEM) has become a better method than the domain-type FEM because DBEM can provide a complete solution in terms of boundary values only, with substantial saving in modeling effort, hence the DBEM was used to simulate the fringing of field around the edges of the fixed finger and movable finger of MEMS combdrive for diverse gap size. Results show that the less the gaps between combdrive fingers and ground plane are, the larger the levitating force acting on the movable finger is. In addition, the levitating force becomes more predominant as the gaps between movable finger and fixed finger decrease. By way of DBEM presented in this article, an accurate electrostatic field can be obtained, and the follow-up control method of levitation force for MEMS combdrive can be implemented more precisely.