Review: Recent Advances in Micromotors

Micromotors are of great interest not only for the miniaturization of current products but also for the realization of future micromachines that can explore challenging environments. The speed of downsizing actuators is slower than that of semiconductor components, but developments over the last two decades have overcome several difficulties and enabled engineers to start designing applications. In this article, we review the existing micromotors ranging from famous articles to state-of-the-art, in particular recent developments and their applications. We deal with three representative principles for rotary and linear micromotors: electromagnetics, electrostatics, and piezoelectricity. Another purpose of this article is to suggest design criteria and physical limitations on these principles for engineers who design millimeter-scale automation devices. Incorporating micromotors can permit space saving and improve design flexibility in application designs, such as smartphones and medical devices.