A MEMS Inertial Switch with Large Scale Bi-Directional Adjustable Threshold Function

An inertial switch with bi-directional adjustable threshold function is designed, and the adjustable threshold is achieved by electrostatic force. Based on Micro-Electro-Mechanical System (MEMS) technology, an all-metal structure inertial switch is fabricated, and the core structure is composed of three-layer parallel plates. Besides, an insulating layer of polyimide is utilized on the top and bottom plates so as to avoid electrostatic breakdown. Typically, the proof-mass as a movable structure also serves as an intermediate plate. Electrostatic forces in different directions are generated by applying voltage on the bottom or top parallel plate electrodes. Through theoretical model and finite element simulation, the force state of the proof-mass during the operating inertial micro-switch is surveyed, and the influence of electrostatic force on the threshold acceleration is also analyzed. The experimental results show that the initial acceleration of the inertial micro-switch is 79 g without bias voltage. When a bias voltage with the range of 0-100 V is applied to the bottom plate, the threshold acceleration varies within the range of 79 g-13 g, and the relationship between voltage and threshold acceleration is negatively correlated. Furthermore, when a bias voltage with the range of 65-100 V is applied to the top plate, the threshold acceleration varies within the range of 170 g-240 g, and threshold acceleration is positively correlated. The experiment is well matched with the theoretical analysis.