Enhanced Efficiency of Electrostatically Actuated Bistable Microswitches Using Bow-Like Operation

To induce snap-through (ST) switching in an electrostatically actuated bistable latchable curved microbeam, a close gap electrode facing the concave surface of the beam is commonly used. In the framework of an alternative architecture considered here, the electrode is placed in front of the convex (backward), rather than concave (forward) side of a beam. The initially curved stress free beam is activated by an electrostatic force pulling it quasistatically in the backward direction, away from the desired buckled configuration. Once the voltage is turned off, the accumulated strain energy is released, and the beam is catapulted toward the buckled state, similarly to an arrow fired by a bow. In the case where the beam exhibits latching, the device may remain in its buckled state indefinitely under zero voltage. The beam can also be snapped back (released), by applying a voltage to the same electrode. In this article, the efficiency of this bow-like actuation is estimated. By means of a reduced order model, it is shown that due to the nonlinearity of the electrostatic force, the suggested operation scenario may lead to a 54% reduction in the ST switching voltage, when compared to the traditional forward actuation. As a result, the device allows bidirectional switching by using a single electrode, and can be viewed as a micromechanical realization of a toggle flip-flop element.