A micro gearing system based on a ratchet mechanism and electrostatic actuation

This paper presents the design and fabrication of a silicon micro gearing system (MGS) that utilizes electrostatic comb-drive actuators to rotate a gear ring through a ratchet mechanism. The rotational comb-drive actuator is engaged with the gear ring through a spring system and ratchet teeth at one end, reciprocally rotates around an elastic point at the other end based on the electrostatic force. Rotational motion and torque from the driving gear ring are transmitted smoothly to driven gears through involute-shaped gear teeth. Smart design of anti-gap structures helps to overcome the unavoidable gap problem occurred in deep reactive ion etching (deep-RIE) process of silicon. The MGS has been fabricated and tested successfully by using SOI (silicon-on-insulator) wafer and one mask only. The angular velocity of the gear ring is proportional to the driving frequency up to 40 Hz.