Threshold Shock Sensor Based on a Bistable Mechanism: Design, Modeling, and Measurements

We analyze and test a microelectromechanical systems (MEMS) shock sensor that switches from a first stable state to a second stable state when subjected to an acceleration exceeding a fixed value. The transition between the two states is obtained because of the bistability properties of specific elastic beams. These are fabricated with a curved initial shape and change their configuration due to the contact force transmitted by an inertial mass sensing the acceleration. No power supply is needed (the device is passive) and the state of the sensor can be detected whenever required in several ways, e.g., by inserting a weak link that is broken during the snap-through of the elastic beam and modifies the electrical resistance between two external contacts. In this paper, focusing on a specific realization with a 1000-g (where g is the acceleration of gravity) threshold, we discuss its modeling and validate it with the experimental data. Experiments are in very good agreement with the numerical simulations, and show that the detection method is stable and robust. Finally, we discuss possible sources of uncertainties and propose a novel optimized design.