A Tristable Mechanism Configuration Employing Orthogonal Compliant Mechanisms

Tristable mechanisms, or devices with three distinct stable equilibrium positions, have promise for future applications, but the complexities of the tristable behavior have made it difficult to identify configurations that can achieve tristable behavior while meeting practical stress and fabrication constraints. This paper describes a new tristable configuration that employs orthogonally oriented compliant mechanisms that result in tristable mechanics that are readily visualized. The functional principles are described and design models are derived. Feasibility is conclusively demonstrated by the successful operation of four embodiments covering a range of size regimes, materials, and fabrication processes. Tested devices include an in-plane tristable macroscale mechanism, a tristable lamina emergent mechanism, a tristable micromechanism made using a carbon nanotube-based fabrication process, and a polycrystalline silicon micromechanism.