Bi-Directional Electrostatic Actuators Based on Al2O3-Sio2 Electrets

P. Pai, F.K. Chowdhury, M. Tabib-Azar
University of Utah, US

Keywords: electrets, MEMS/NEMS-actuators

Summary:

Electrostatic actuators are unidirectional due to the nature of the excitation force that is always attractive. This work presents the first MEMS/NEMS-scale bi-directional electrostatic actuator using electrets that is capable of producing large displacements (up to 20µm) with small excitation voltages (~6Vpp). A 20x reduction in the actuation voltage was observed to produce the same displacement. The actuator was made of a bi-layer electret material (Al2O3-SiO2) that required no external charging unlike regular electrets. Charge retention in these electrets was increased from a couple of days to 5 weeks when placed in vacuum using a new technique similar to remote doping in quantum wells. This technique was used to realize a 3-to-1 multiplexer that used only one switching element in the form of a diaphragm for operation, as opposed to multiple transistors used in CMOS.