External load cell (a) (b) (c) Figure 11 Experimental setup to measure the force of the actuator. ‐10 0 10 20 30 40 50 60 70 80 ‐200 ‐100 0 100 200 300 Displacement, um Force, mN 8V 7V 6V 5V 4V 3V 2V (a) (b) Figure 12 (a) Load-displacement curves of the actuator at various level of actuation; (b) snap-thru. Figure 12(a) shows a series of load-displacement (F-d) curves of the actuator. In general, the curve of higher excitation voltage has a stiffer slope and a higher snap-thru load. Data show that for most cases the shuttle ends up the same position after snap-thru. The reason is that two actuator beams are rest against fixed walls as shown in Figure 12(b). SUMMARY The basic mechanical and thermal behaviors of a thermal actuator were characterized. The power, temperature, in-plane and out-of-plane components of displacement, and load-displacement curves as functions of the actuation voltages were obtained under quasi-static loading at the ambient condition. The relations are all nonlinear. The frequency response of the actuator was also investigated. When the operating frequency is greater than 1 Hz, the range of stroke starts to decrease and becomes negligible at about 50 Hz. ACKNOWLEDGEMENT Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under contract DE-AC04-94-AL85000. REFERENCES [1] J.R. Torczynski, M.A. Gallis, E.S. Piekos, J.R. Serrano, L.M. Phinney, and A.D. Gorby, “Validation of Thermal Models for a Prototypical MEMS Thermal Actuator,” SAND2008-5749, September 2008. [2] L.L. Chu, L. Que, A.D. Oliver, and Y.B. Gianchandani, “Lifetime Studies of Electrothermal Bent-Beam Actuators in Single-Crystal Silicon and Polysilicon” Journal Of Microelectromechanical Systems, Vol. 15, No. 3, June 2006. 208
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