Design optimization of a fully-compliant bistable micro-mechanism

Manufactured bistable MEMS shown in the two stable positions.

Bistable behavior is desirable for a variety of applications because power is applied only during switching, and the mechanism state remains the same regardless of any power interruptions. The low variability in the stable positions also makes accurate open-loop control of many systems possible, and the precise switching characteristics make them valuable in sensing arrays. In this paper, fully-compliant bistable micromechanisms were modeled using finite elements. This model was then coupled with an optimization program, allowing extensive exploration of the design space. Three designs within this space were generated by minimizing the layout size of the devices subject to force constraints. These designs were subsequently manufactured and tested to verify bistability, with each mechanism snapping as expected between the two stable positions. The design space was then further explored to determine the behavior of the device as the maximum force output increased. This study revealed that the minimum layout size increases with the maximum force output.