Abstract: This paper introduces a type of out-of-plane microelectrothermal actuator, which is based on the principle of bimetal film thermal expansion in the fuse. A polymer SU-8 material and nickel are used as the functional and structural materials of the actuator. Through heating the resistance wire using electricity, the actuator produces out-of-plane motion in the perpendicular axial direction of the device and the bias layer contact with the substrate, completing signal output. Using Coventorware software to establish the three-dimensional model, the geometric structure is optimized and the electrothermal capabilities are determined theoretically. From electrothermal analysis, the actuator's displacement is 18 μm and the temperature rises from 300 to 440 K under a voltage of 5 V and the response time is 5 ms. The actuator's displacement is 20 μm under a 100000 m/s² acceleration in the accelerating field. In the coupled field, applying a 3 V voltage, the initial temperature is 300 K, while the acceleration is 50000 m/s², the driving displacement of the actuator is 23 μm, and temperature rises to 400 K. Finally, through checking the stress in different field sources, the maximum stress of the actuator is smaller than the allowable stress of nickel. The results show that the electrothermal actuator has high reliability.

Key words: bimetal film, electrothermal actuator, thermal expansion, SU-8, Coventorware, stress check