Electrostatic batch assembly of surface MEMS using ultrasonic triboelectricity

In this paper we present a novel method for batch assembly of polysilicon hinged structures. The method uses ultrasonic vibrations generated with an attached piezoelectric actuator to vibrate polysilicon plates on silicon nitride or polysilicon surfaces. We believe that the rubbing between the substrate and the structures creates contact electrification charge that results in hinged flaps to be stabilized vertically on the substrate at elevated temperatures. Furthermore, the ultrasonic triboelectricity is shown to be the most likely explanation due to the observed "memory effect" in which assembly occurs even without further ultrasonic actuation after the initial ultrasonic assembly. This method has been used to batch assemble an array of hinged flaps, retroreflectors, and plates with retaining springs.