Theoretical and experimental study of linear motors using surface acoustic waves

This paper presents the theory, simulation results and experimental study of the slider displacement at nanometer scale in linear ultrasonic motors using surface acoustic waves that can be used as microconveyors. To our knowledge, this is the first attempt to describe the energy transfer from the acoustic wave to the slider in these motors. The model shows that the mechanism is sequential with alternative phases of levitation and contact with step-like behavior of the slider velocity. To validate the model, several microconveyors using Lamb and Rayleigh waves are fabricated. These waves are generated from interdigital transducers with, respectively, 10 and 20 MHz frequencies, which are the highest in ultrasonic micromotors. The control of motion is obtained by varying the duration of the driving signal applied across interdigital transducers. The measured displacement varies from several nanometers to several centimeters. Comparison between experimental and theoretical results shows a good agreement. This model gives a quantitative description of slider motion. In another way, it allows the deduction of key parameters for energy transfer. As an example, a study of slider contact shape is performed. (C) 1998 Elsevier Science S.A. All rights reserved.