Design and Driving Methodology of Out-of-Plane Electrostatic Microactuator With Extended Stable Motion Range

We present design and driving methodology of out-of-plane electro-static microactuator to extend stable motion range without any closed loop control system. The microactuator employed in this study is a curved cantilever microactuator, which consists of a curved cantilever moving electrode and a taper-shaped substrate electrode. A curved cantilever brings large deflection in the out-of-plane direction. Electrostatic and mechanical model of the device is derived. The equilibrium position and the stability of the cantilever are considered by calculating the stored electrostatic energy, the stored elastic energy and the lost energy from a power source due to the transfer of charges. The design methodology of the electrode shapes using the model is described and a prototype device is designed. The substrate electrode has tapered shape according to a function of distance from the anchor. The prototype is fabricated and its driving characteristics are examined. Stable motion range is extended to 65% of its full stroke by applying DC voltage and to 77% by square-wave AC voltage having a 2-kHz frequency. The calculated driving characteristics by a modified model that includes the existence of particles on insulator surface coincide with the measured one.