This paper presents an investigation on the dynamic characteristics of a compliant bistable micromechanism. The analyzed bistable micromechanism has two stationary positions at the two extremes of the motion range, where the strain energies are local minimum. A bistable mechanism is a nonlinear system with a special stiffness. In this study, the compliant bistable micromechanism adopted was a well-known configuration. The central mass of the micromechanism was treated as a carriage to carry switching components, such as a mirror or an electrical contact. The dynamic characteristics of the bistable micromechanism would be significant in the application of switching devices. In order to verify the correctness of theoretical prediction on the dynamic characteristics, the designed micromechanisms were fabricated by MEMSCAP's PolyMUMPs<sup>(R)</sup>. In addition, a test rig incorporating the required instruments was then constructed for measuring the performance of the bistable micromechanism. From the experimental study, it revealed that good agreement between analytical and experimental results were obtained.
A bistable compliant micro-mechanism possesses the distinguish characteristics of both the bistable mechanism and the compliant one. It can be suitably employed in various MEMS devices, such as a micro-relay, an impact sensor, etc. Currently, preventing fracture and enhancing reliability are the most important issues in the application of bistable compliant micro-mechanisms. Through a systematic design methodology, including tuning the parameters of geometric shapes, adding a stopper at the proper position, etc., one can obtain a more appropriate micro-mechanism for designated applications. This paper proposes a systematic methodology for the design of bistable compliant micro-mechanisms.
This paper proposes a design of a bistable micromechanism for the application of switching devices. The topology of a fully compliant four-bar mechanism is adopted herein. The central mass of the mechanism is employed as a carriage to carry switching components, such as mirror, electrical contact, etc. The equations that predict the existence of bistable states, the extreme positions of the motion range and the maximum stress states of members were derived. MUMPs provided by Cronos Integrated Microsystems fabricated the proposed micromechanisms for the purpose of verifying the theoretical predictions. Finally, an experimental rig was established. The bistable mechanisms were switched either by the probe or actuators to push the central mass. The experimental results demonstrated that the motions observed approximately met the predicted values.