Extending the traveling range with a cascade electrostatic comb-drive actuator

Electrostatic comb-drive actuators have been developed and employed for many applications. However, side stability (side pull-in) limits the actuator stroke constraining its applications. Hence, extending the stable traveling range is an important issue for designing electrostatic comb-drive actuators. This study presents a novel cascade electrostatic comb-drive actuator. Instead of shifting the spring constant of the suspended springs, the proposed actuator extends the stable traveling range using a multi-stage cascade configuration. To demonstrate the performance of the cascade configuration, simulation using the finite element method is utilized to model the proposed cascade actuator. To implement the cascade electrostatic comb-drive actuator, the Taiwan Semiconductor Manufacturing Company (TSMC) 0.35 μm two-polysilicon and four-metal layer (2p4m) CMOS processes and post-CMOS micromachining steps are employed to fabricate the device. Experimental results demonstrate that the proposed design extends the stable traveling range to 200% as compared with that of a comb-drive actuator without this cascade configuration. (Some figures in this article are in colour only in the electronic version)