Modelling of an Initially-retracting Electrothermal Microactuator

Abstract

Electrothermal actuators are preferred in Microelectromechanical Systems (MEMS) devices when large force and stroke at comparatively lower driving voltages are desired. A generic electrothermal microactuator moves only in one direction that depends on its geometry and is independent of the polarity of voltage applied across its terminals, unlike electric motors and actuators. There are a few applications where electrothermal actuators are required to actuate in both directions. Towards fulfilling this need, a novel actuator that initially retracts and then moves forward upon application of a rising voltage is presented. It consists of an integrated pair of V-beam or inclined beam electro-thermal actuators, which actuate in opposite directions operating as an antagonistic pair. When the voltage is applied, the actuator moves backward for some time and then moves forward to attain a steady state position, hence the name “initially-retracting actuator”. Desired degree of antagonism can be achieved by varying the geometric parameters such as length, number of inclined beams, and offset for the integrated pair of V-beam actuators. In this paper, we describe the analytical model to design the actuator for desired behavior. Results pertaining to thermal imaging and dynamic response of the actuator are presented for experimental validation of the model.