A novel microelectrostatic torsional actuator

Presently, the torsional actuator has gained a lot of attention in the area of microactuators. Because the torsional actuator cannot carry a substantial mechanical load in the out-of-plane direction, it is frequently used in some optical or electrical applications such as light modulators and spatial scanner devices. However, the performance of the torsional actuator is limited to the fabrication process and operating conditions. For instance, it is difficult to fabricate a torsional actuator with both a large rotating angle and large size moving plate. A novel electrostatically driven torsional actuator is proposed in this paper. The torsional actuator is fabricated through the integration of surface and bulk micromachining processes. Thus, the goal of fabricating a torsional actuator with a cavity right beneath the edge of the moving plate is reached. In addition, the thin film residual stress is exploited to modify the shape of the torsional actuator. The advantage of the proposed design is to increase the traveling distance of the actuator as well as to increase the area of the moving plate. In short, the proposed design provides the possibility of increasing the size of a moving plate without reducing its rotating angle. Therefore, the applications for the torsional actuator, such as image scanner and positioner, are increased.