Ultrasonic micromotors

Initial work is presented on an ultrasonic micromotor. Small polysilicon blocks were both translated and rotated using traveling flexural waves in thin membranes. The acoustic wavelength was typically 100 μm. The interdigital transducer voltage was typically 5 V; motion was observed at as low as 1.5 V. The acoustic wave power was about 1 mW. Linear motion quickly moved the blocks off of the 3-mm by 8-mm membrane region, but rotational motion was quite stable. Three possible mechanisms for energy transfer from the acoustic wave to the blocks were examined. Preliminary results in air and in vacuum indicate that a fluid boundary layer is responsible for the energy transfer