Characterization of silicon parallel-plate electrostatic actuator in partially conducting aqueous solution

In this paper we present experimental results on the behavior of a silicon parallel-plate electrostatic actuator operated in a partially conducting aqueous solution. First, an experimental setup based on a laser position sensor is described for dynamic measurement of out-of-plate motion of MEMS structures in liquids. This set up is used to characterize motion of a surface-micromachined, polysilicon piston actuator operated in water using high- frequency drive signals to avoid charge migration that screens actuation potential. Results show that besides actuator design and fluid properties, voltage-displacement characteristics and pull-in phenomenon of parallel-plate actuators also depend on drive frequency.