An Electrostatically-Driven Phase Change Actuator for Vibration Control

Abstract

Abstract Many motion control applications rely on piezoelectric and magnetostrictive type actuation devices to achieve active control or micro-manipulation. These devices have an important drawback. They are limited in their ability to simultaneously provide large force and large displacement. A new concept electrostatically driven phase-change actuator (EDPA) has been theoretically studied to investigate if the drawbacks inherent to these devices might be overcome. This actuator concept relies upon changes in vapor pressure to expand a pliant membrane enclosing a vapor cavity. Changes in the vapor pressure are achieved by applying an electric field across a dielectric liquid film beneath the vapor space. The field polarizes the liquid molecules reducing the liquid pressure. A reduced liquid pressure produces an associated decrease in the equilibrium vapor pressure at the liquid-vapor interface. The surrounding vapor subsequently condenses causing a reduction in the vapor pressure. As a result, the membrane retracts. When the field is removed, the equilibrium vapor pressure increases above the pressure of the surrounding vapor, causing liquid to evaporate. The evaporation increases the vapor pressure, expanding the membrane. Simulations of the device performance have shown it capable of producing forces of over 300 N with displacements of up to millimeters and sub-millisecond response time, while maintaining a much smaller package (lengthwise) than possible using stacked magnetostrictive or piezoelectric actuators. However, the transverse dimensions required to produce this force were found to be substantial (20 mm).