Effect of Heat Transfer on Materials Selection for Bimaterial Electrothermal Actuators

Bimaterial electrothermal actuation is a commonly employed actuation method in microsystems. This paper focuses on optimal materials selection for bimaterial structures to maximize the thermomechanical response based on electrothermal heat-transfer analysis. Competition between different modes of heat transfer in electrothermally actuated cantilever bimaterial is analyzed for structures at the microscale (10 mum les L les1 mm) using a lumped heat-capacity formulation. The choice of materials has a strong influence on the functional effectiveness and the actuation frequency even though the electromechanical efficiency is inherently small (~10^-5). Frequencies on the order of ~100 Hz to 15 kHz can be obtained for bimaterial structures at small scales by varying either the operating temperature range or the rate of heat dissipation. It is found that engineering alloys/metals perform better than other classes of materials for high-work high-frequency (~10 kHz) actuation within achievable temperature limits.