Micro actuators are needed for numerous applications, ranging from mobile and wearable devices, to minimally invasive medical devices. However, the limitations associated with their fabrication have restricted their deployment at the one-millimeter scale.

Assistant Professor Tomoaki Mashimo, developer of the micro ultrasonic motor.

Piezoelectric ultrasonic motors are expected to become high-performance micro motors because of their high torque density and simple components. The smallest existing ultrasonic motor reported to date has a metallic component with a diameter of 0.25 mm and a length of 1 mm. However, its total size, including the preload mechanism, amounts to 2-3 mm.

A researcher at the Toyohashi University of Technology has been developing a micro ultrasonic motor with a one-cubic-millimeter stator. The stator, which comprises a metallic cube with a through-hole and plate-piezoelectric elements adhered to its sides, can be scaled down without requiring any special machining or assembly methods.