A pulse-operating electrostatic microactuator for bi-stable latching

We propose a novel microactuator with spade comb fingers designed for pulse-operating bi-stability. When the broad parts of the movable comb fingers are positioned facing the broad parts of the fixed comb fingers, the direction of electrostatic force is inward, like a conventional comb actuator. However, the spade comb fingers generate outward electrostatic force when the broad end part of each movable comb finger is positioned facing the narrow part of the fixed comb fingers. The proposed spade comb is combined with chevron-type springs to effectively operate the actuator in a bi-stable latching. For a driving input, a fast electrical pulse was applied to one driving electrode, and its operability was investigated in terms of voltage magnitude and duty time. Through an FEA (finite element analysis) and a numerical analysis, the dynamic characteristics were theoretically investigated including transient time response and operable bi-stability, which were compared with the experimental values. The bi-stable actuator was fabricated using a silicon-on-insulator (SOI) wafer, and successfully operated by a pulse voltage input of 55 V with a duty time of 0.32 ms.