A microfabricated electrochemical actuator for large displacements

A large-displacement electrochemical actuator was designed, fabricated, and tested. The large displacement is obtained by using a corrugated membrane made by physical vapor deposition of Parylene sandwiched with an intermedia te layer of sputtered platinum. The layered structure is approximately 8-mu m thick, with 26 grooves approximately 120-mu m deep, and with a radial pe riod of 350 mu m. The electrochemical cell consists of platinum electrodes with a 1 M H2SO4 solution. Hydrogen and oxygen gas is generated to displace the membrane. Although the actuator can operate at a voltage as low as 1.2 3 V, the experimentally determined efficiency of converting electrical ener gy to mechanical work is only 0.37%. The governing equations for the conser vation of mass, momentum (equilibrium), energy, and the entropy generation rate were formulated assuming that the gas bubbles either nucleate without growth or grow without nucleation. For the nucleation case, simulations wer e performed for constant pressure isothermal actuation, and the average exp erimental efficiency was bounded by simulations with gas bubble radii betwe en 1 x 10(-5) m and 1 x 10(-6) m. The predicted ratio of the power dissipat ed to the electrical power supplied is 1.37 for isothermal actuation.