Electrostatic levitation: an elegant method to control MEMS switching operation

This paper investigates the characteristics of a micro-switch that uses two side electrodes to open a normally closed switch. The side electrodes surround the fixed electrode in the well-known gap-closing electrode configuration. The side electrodes can open a closed switch and be tuned to respond appropriately to outside forces. The combined electrode system dramatically improves the control of a standard gap-closing electrode configuration. In conventional switches, a DC voltage above a certain value closes the switch. To reopen the switch, the voltage difference is reduced to peel off the moving electrode. Currently, the contact area is carefully designed to avoid stiction, but the degradation over time and stiction forces can cause a permanent failure. In this work, opening occurs by feeding the side electrodes a voltage beyond a certain value that results in a levitation force. Even if the degradation in the surfaces happens, the switch can open by increasing the side voltages. The characteristics of the combined actuation system are thoroughly analyzed and include the static pull-in, static displacement, release voltage, dynamic pull-in, frequency response, and basins of attraction. The results are validated by the experimental tests. The levitation-based micro-switch improves the system tunability as the sensitivity and switching thresholds can be adjusted.