Design, Modeling and Testing of Polysilicon Optothermal Actuators for Power Scavenging Wireless Microrobots

Abstract

The biggest hurdle to be solved, in order to create autonomous Micro-Electro-Mechanical Systems (MEMS) microrobots, is generating power for their actuator engines. Most present actuators require orders of magnitude more power than is presently available from micropower sources. To enable smaller microrobots, this research investigated a simplified power concept that eliminates the need for on-board power supplies and control circuitry by using actuators powered wirelessly from the environment. The use of lasers to directly power micrometer scale silicon thermal actuators was explored. Optothermal actuators, intended for use on a small wirelessly propelled autonomous MEMS microrobot, were modeled, designed, fabricated and tested, using the PolyMUMPs silicon-metal chip fabrication process. A 760 µm by 710 µm prototype MEMS polysilicon-based microrobot, using optothermal actuators, was designed, fabricated and tested. Each of its parts was demonstrated to provide actuation using energy from an external laser. The optothermal actuators provided 2 µm of deflection to the microrobot drive shaft, with 60 mW of pulsed laser power. The results of these experiments demonstrated the validity of a new class of wireless polysilicon actuators for MEMS devices, which are not directly dependant on electrical power for actuation. The experiments also demonstrated a potentially viable design that could be used to propel the world’s smallest autonomous MEMS microrobot.