Design, modeling and testing of a unidirectional MEMS ring thermal actuator

This paper describes a novel design for polysilicon micro ring thermal actuators (RTA) fabricated using the multi-user-MEMS-process (MUMPs). A RTA is comprised of a ring supported by 12 thin spokes. The spokes are 2 × 2 μm in cross section and 155 μm long. The inner diameter of the ring is 390 μm, and its outer diameter is 440 μm. The spokes are placed almost radially with an offset distance r of 3 μm measured from the ring center to the spoke axes. The actuator design can generate linear motion of 6 μm measured at the end of a spoke. A theoretical model and a finite element model have been developed in this paper. The actuator has been tested and these results agreed with the simulation results. In order to study the behavior of the RTA at its natural resonant frequencies, modal analysis has also been conducted.