Novel bounce drive actuator for large step displacement and low friction micromotor applications

This investigation presents an innovative bounce drive actuator (BDA) to develop a rotary micromotor with low friction and large step displacement. The BDA device has a shorter plate and wider bushing designs than the conventional scratch drive actuator (SDA), resulting in a new electrostatic bounceback driving mechanism and a larger step size of motion. The innovative bounce actuating mechanism considerably reduces the friction between the free end of the BDA-plate and the nitride insulator and effectively eliminates the sudden reverse rotation effect of SDA. Additionally, this study introduces three advanced designs (filleted supporting beam, flanged cover and ribbed/dimpled inside-ring) into the structure of a BDA-based rotary micromotor to decrease further the abrasion between the inside-ring of the rotor and the cover, anchor and inside-rail; reduce the driving voltage and increase the lifetime. The BDA- based micromotors developed in this work (with 398 mum in diameter) were fabricated using the MEMSCAPreg Poly-MUMPs process and many improvements, including the large step displacement (180-196 nm), low driving voltage (70 -95 Vo-p), long lifetime (> 72 hrs) and consistent rotary direction were demonstrated.