Response surface based optimization of translational electro-thermal microactuators

Qikai Xie

Microactuators, the most notable functional elements of mircroelectromechanical systems (MEMS), have been under vast research and rapid development in past decades. A variety of microactuators based on different driving mechanisms have demonstrated their capability in many areas. Among them, electrothermal microactuators are proved advantageous in providing large actuating force, requiring low voltage, and generating large displacement but companied by high power consumption. This thesis aims at optimizing the performance of two recently proposed translational electrothermal microactuators by virtue of coupled electro-thermal-mechanical finite element method and response surface method, side effects taken in to consideration. The first microactuator is designed to work in out-of-plane direction. Static, transient and dynamic characteristics of the microactuator device are analyzed using coupled electro-thermal-mechanical finite element models. The modeling results reveal that the performance of the original design is undesirable as the central mirror platform is undergoing a lateral shift and is bent concave down when the microactuator is activated. In order to maintain the relative flatness of the mirror surface, a new design with a folded-arm structure is proposed. The design is further optimized using experimental design and response surface method to achieve large actuation displacement and improved resonant frequency response. Overall, the results show that the optimized design outperforms the original design in achieving large displacement, fairly small lateral shift and mirror flatness under the same actuating voltage, while maintaining a compact size and supporting the high bandwidth servo control. The other microactuator aims at producing in-plane motion. This device, mainly comprising a moving stage and two polymeric composite benders, is characterized and optimized both statically and transiently. The coupled multi-field finite element analysis suggests that original design is experiencing an undesirable in-plane rotation. Both geometric and parametrical optimizations are then performed to overcome the problem. The results indicate that, compared with the original design, the new design can generate larger lateral shift under a smaller actuating voltage, while keeping a lower temperature.

Response surface based optimization of translational electro-thermal microactuators

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