Simulation and optical measurement of MEMS thermal actuator sub-micron displacements in air and water

The aim of this study is to simulate and measure sub-micron motion of a chevron type MEMS thermal actuator in air and water. Finite element analysis (FEA) of the physical system provided predictions of the actuator temperature increase and displacement in both media. Simulations indicate that for 6V the maximum temperature on the chevron actuator arm is 335 °C in air and 35 °C in water. In water the temperature increase is confined to the vicinity of the heat source: 30 μm from the actuator center the temperature increase is smaller than 0.5 °C. FEA predicts a chevron displacement of 0.98 μm in air and 49 nm in water at 6 V. Experimental measurements of displacements were performed using an FFT image analysis algorithm with sub-micron precision. Experimental results show a displacement of 1.11 ± 0.01 μm in air and 67 ± 17 nm in water for 6V. The agreement between simulated and measured results validates the accuracy of the computational model used in this study. From the experimental data, the performance of the thermal actuator in water is about 6% of its performance in air. The study indicates the feasibility of using thermal actuators to perform cell tests in aqueous media.