In this paper, we propose the use of Si/Ge nanocomposite materials to improve the performance of microthermal actuators. Nanocomposites with a high electrical to thermal conductivity ratio can facilitate a rapid temperature change within a short distance, enabling a high temperature increase in a large region of the actuator beams. The total structural thermal expansion and, consequently, the actuation distance can be increased significantly. A top-down quasi-continuum multiscale model is presented for the computational analysis of nanocomposite based thermal actuators. In the multiscale model, the thermo-mechanical response of the actuator due to Joule heating is modeled using classical continuum theories, while the thermal and electrical properties of doped Si and Si/Ge nanocomposite materials are obtained from atomistic level descriptions. An iterative procedure is carried out between the calculations at the two length scales until a self-consistent solution is obtained. Numerical results indicate that incorporating Si/Ge nanocomposites in thermal actuators can significantly increase their energy efficiency and mechanical performance. In addition, parametric studies show that the size of the nanocomposite region and atomic percentage of the material components have significant effects on the overall performance of the actuators.
Issue Section:
Micro/Nanoscale Heat Transfer
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