Piezoelectric ultrasonic bidirectional linear actuator for micropositioning fulfilling Feynman’s criteria

A bidirectional linear microactuator with a stator less than $400μm3$⁠, fulfilling Feynman’s original criteria for a motor less than $1∕64th$ of an inch on a side [R. Feynman, Engineering and Science Magazine (Caltech) 4, 23 (1960)], is shown to generate forces over $30mN$ in either direction at speeds of up to $40mm∕s$ using a large $28g$ polished alumina slider. Using the thickness mode of a stepped piezoelectric block in conjunction with a pair of fundamental flexural modes of a pair of slanted beams—each slightly differs in configuration—gives the ability to generate silent bidirectional motion at an excitation frequency of about $1.7MHz$⁠. In addition to offering forces at least one order of magnitude larger than those of the other methods, the system also serves as a platform for studying nonlinear frictional phenomena on the nanoscale and its manipulation through acoustic irradiation of the contact interface for propulsion.