Saw-tooth vernier ratchets for electrostatic inchworm actuators

Abstract

MEMS ratchets are used for positioning applications. The precision of positioning is related to the size of the ratchet and the minimum feature size of the microfabrication process. A new, saw-tooth shape, vernier ratchet topology to overcome minimum feature dependency is realized. A microfabricated test vehicle proves that this new topology can achieve an improved latching property under low forces. These ratchets are also implemented in low-voltage electrostatic inchworm actuators to improve the actuator force–displacement performance. The actuator has an average step size of 160 nm which indicates that the ratchets can be used for grid independent latching. It operates only at 18 V, and provides ±12 μm displacements with ±15 μN output force. We expect that the force–displacement characteristics will be further improved with sharper teeth design.