Topology and Size Optimization of MEMS Electrothermal U-Shaped Actuator

To improve the overloading resistibility of the electrothermal U-shaped actuator, this article employs size and topology optimization to realize the multiobjective optimization of the U-shaped actuator. The micro-electromechanical system (MEMS) pin puller based on the U-shaped actuator is optimized to verify its effectiveness. The pin of the MEMS pin puller was lightweighted first, and the finite element method (FEM) simulation was used to compare the strength and function of MEMS pin puller before and after the pin optimization. After pin optimization, the optimization combining multiphysics field-coupled FEM, impact FEM, and NSGA-II is established to realize the multiobjective optimization of U-shaped actuator. The radius of the flexure round corner and the mass distribution of the cold arm are used as design variables, and the optimization objectives are the displacement of the pin, the maximum stress of the flexure, and the maximum temperature of actuator. The impact experiment and function experiment of the MEMS pin puller are carried out to verify its overloading resistibility under impact load and output displacement under driving voltage. The results show that the overloading resistibility of the optimized MEMS pin puller increased from 9000 to 16100 g, with a 78% improvement. The overloading resistibility of the U-shaped actuator is increased from 9000 to 20300 g, with a 125% improvement. Meanwhile, the output displacement is reduced from 186 to $90~\mu $ m, with a 52% reduction. The response time is not affected. Therefore, the method in this article is suitable for the optimization of U-shaped actuators under complex conditions. It can provide guidance for improving the overloading resistibility of U-shaped actuators.