Open-Loop, Self-Excitation In A Bistable Micromechanical Beam Actuated By A Dc Electrostatic Load

We demonstrate an open-loop self-excitation response in a curved, bistable microelectromechanical beam under a time-independent electrostatic load. The self-excitation is triggered by placing a high value resistor in series with a beam that is on the verge of bistability. The voltage-deflection curve of such a beam contains an inflection point, where the slope of the curve is approximately zero. Our results show that actuation at a voltage corresponding to the inflection point induces stable self-sustained oscillations. We further observe that implementation of the same actuation scenario in a bistable beam, with the voltage-deflection curve containing two stable branches, does not lead to self-excitation.