Polysilicon micro vibromotors

Two types of polysilicon microvibromotors have been designed, fabricated, and successfully operated in air and in vacuum. Each of these two types utilizes an electrostatically driven vibrating structure (the converter) to actuate a circular microrotor by means of oblique mechanical impact. Oscillatory linear motion is consequently converted into continuous angular motion. The microrotors are fabricated both 60 and 100 mu m in diameter and are restrained at the center by a polysilicon hub. The converter tips are retracted by electrostatic comb drives and are propelled forward toward the rotor by elastic forces generated by folded beam flexures at frequencies ranging from 10 kHz to 20 kHz. A coupled, three-degree-of-freedom dynamic model successfully predicts both the two mode shapes and the frequency ranges of the bimodal converter observed in the experiment. An impact dynamics model of the vibromotor system is constructed to understand and estimate the dynamics between converter and rotor.<
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