Characterization and modeling of a liquid-vapor phase change membrane actuator with an integrated SU-8 micro capillary wicking structure

A liquid-vapor phase-change membrane actuator is demonstrated which integrates an open groove wicking structure to continuously pump liquid into the heat addition region of the pressure cavity. Integration of the wick yields a higher efficiency and operating speed compared with existing thermal phase-change actuators. This improvement results from control of the liquid thickness, volume, and fill rate. An experimentally validated numerical model is presented which determines the energy budget within the actuator and investigates factors controlling efficiency such as wick thickness, thermal mass, thermal conductivity, and membrane compliance. Work to date for this class of actuators has focused primarily on steady state behavior with detailed transient analyses receiving little attention. This investigation focuses strictly on characterization of transient operation and provides a benchmark for this class of dynamic thermal actuators. The actuator presented in this work develops pressure and deflection excursions of 148 kPa and 70 μm at 10 Hz while consuming 150 mW. A peak force of 1.4 N is generated during each cycle and the thermal to mechanical efficiency is 0.11%.