Pull-in instability of parallel-plate electrostatic microactuators under a combined variable charge and voltage configuration

In this letter, we present a theoretical analysis of pull-in instability of parallel-plate electrostatic microactuators under a combined variable charge and voltage configuration. This occurs in parallel plate capacitors partially filled with a charged dielectric (electret) where the plates are connected together through an impedance. Our results demonstrate the possibility of achieving full range motion under certain conditions. For Teflon® electrets much thinner than the air gap; the maximum traveling distance is similar to the voltage controlled electrostatic actuators (gap/3), whereas for electrets four times thicker than the initial gap the maximum traveling distance can approach 100% of the gap.