A MEMS Pressure Sensor Using Electrostatic Levitation

Abstract

Applying electrostatic levitation force to the initially-closed gap-closing electrodes of our micro-electro-mechanical system (MEMS) creates multi actuation mechanisms, and opens a new world to the MEMS applications. Electrostatic levitation allows us to measure physical quantities, such as air pressure, by exploiting pull-in instability and releasing. The beam starts from a pulled-in position by applying a voltage difference between two gap-closing electrodes. When enough voltage is applied to the side electrodes, the cantilever beam is released. At the release instant, electrostatic forces, restoring force, and surface force are applied to the cantilever. According to the experimental results of this work, the surface interaction force varies as the pressure changes. This work shows that at the release instant, we can correlate the pressure and the interaction force. This idea is exhibited by two mechanisms in this work: a pressure sensor and a pressure switch. Having side electrodes has enabled measuring interaction forces, which was not possible with conventional gap-closing electrodes. The interaction forces are estimated using the experimental data at different pressures. The results show that the interaction force is mostly repulsive and is increased as the pressure is increased. In addition, we found that the potential voltage between the gap-closing electrodes in pulled-in position immensely influences the surface interactions.