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.