A tristable compliant micromechanism with two serially connected bistable mechanisms

• A tristable micromechanism with combination of two bistable mechanisms is developed.
• The mechanism exhibits the tristable behavior within a displacement range of 260 μm.
• This mechanism with no movable joints is suitable for applications in micro systems.

A tristable micromechanism with a bistable mechanism embedded in a surrounding bistable mechanism is developed. Three stable equilibrium positions are within the range of the linear motion of the mechanism. The proposed mechanism has no movable joints and gains its mobility from the deflection of flexible members. The tristability of the mechanism originates from the different actuation loads of the two bistable mechanisms. Finite element analyses are used to characterize the tristable behavior of the mechanism under static loading. An optimal design formulation is proposed to find the geometry parameters of the mechanism. Prototypes of the mechanism are fabricated by a simple electroforming process. The characteristics of the mechanism are verified by experiments. The force versus displacement curve of the mechanism exhibits the tristable behavior within a displacement range of 260 μm.