A brief review of actuation at the micro-scale using electrostatics, electromagnetics and piezoelectric ultrasonics

Abstract

Though miniaturization and mass production via integrated circuit fabrication techniques have transformed our society, the methods have yet to be successfully applied to the generation of motion, and as a consequence the many potential benefits of microrobotics has yet to be realized. The characteristics of electrostatic, electromagnetic and piezoelectric transduction for generating motion at the micro scale is considered, employing scaling laws and a reasoned consideration of the difficulties in motor fabrication and design using each method. The scaling analyses show that electrostatic, electromagnetic and piezoelectric actuators all have comparable force scaling characteristics of F α L2; if one employs permanent magnets, electromagnetic forces do not scale as F α L4. Though the torque, τ, of piezoelectric ultrasonic motors scale rather poorly with τ α L 4, they have the clear advantage of possessing torque amplitudes some two orders of magnitude larger than motors employing the other transduction schemes at the micro scale. © 2010 The Acoustical Society of Japan.