Untethered Micro-actuators for autonomous Micro-robot locomotion: Design, fabrication, control, and performance

Abstract

This paper presents a micro-actuator that operates free of any physically restraining tethers. We show how capacitive coupling can be used to deliver power to untethered MEMS (micro-electromechanical systems) devices, independently of their position and orientation. Our novel power delivery and actuation mechanisms are designed for use in autonomous mobile robots whose dimensions can be measured in tens to hundreds of micrometers. Test devices utilizing these mechanisms have been fabricated at scale using MEMS technology, and have been shown capable of untethered locomotion at speeds exceeding 1.5 mm/sec. The corresponding speed, scaled to a car-sized robot would be over 100 km/hr. The possibility of autonomous (untethered) microactuators and microrobots less than 80 μm in length opens the door to novel applications in distributed and parallel robotics Scratch-drive actuators (SDAs) [1,2] are capable of both high speed and nanometer-scale precision, making them a promising choice for the actuators of mobile microrobots. We developed a novel kind of SDA that walks without the physically-restraining electrical tethers, rails, stators, or springs required in previous work. Our power delivery mechanism operates through a capacitive coupling with a silicon substrate that underlies the mobile device. This allows the device actuation mechanism to use electrostatic forces without requiring any physical connection or wire that would restrain the motion of the device. Through appropriate design of the substrate wiring and actuator geometries, the power delivered to the device can be shown to be independent of the device's position and orientation. For this reason, this power delivery mechanism is appropriate for fully two-dimensional (x, y) and (x, y, θ) mobile microrobots. © Springer-Verlag Berlin Heidelberg 2005.