Extending and Tuning the Travel Range of Microelectromechanical Actuators Using Electrically Reconfigurable Nano-Structured Electrodes

The travel range of a microelectromechanical actuator is defined as the maximum distance traveled by the movable electrode before it is pulled-in. In this letter, we ask 1) whether the travel range of voltage controlled microactuators be extended beyond the limit of one-third of the initial air-gap for parallel-plate actuators and 2) if the travel range be tuned once the structure is fabricated, both without using any external feedback circuit, series capacitor, and/or modifying the actuation mechanism. Our results show that microactuators with nano-structured electrodes and non-linear spring can achieve a travel range of [p/(n+p)] of the initial air-gap, where n (=2 for parallel-plate actuators) is a constant that depends on the electrode geometry and p (=1 for linear spring) is the order of nonlinearity of the spring. Therefore, an electrical tuning of the geometry parameter n using reconfigurable nano-structured electrodes enable versatile, on-demand, post-fabrication control of the travel range.