Fig. 1. The MEMS mechanism design.
a The MEMS mechanism is a spring-mass system with a proof mass suspended by a curved beam and two folded beams. A slit is located in the centre of the proof mass. b The force-displacement curves of different springs are plotted. c The resonant frequency decreasing behaviour with tilt is plotted. The resonant frequency will significantly decrease from 95 Hz to 2.6 Hz (85°) when the curved beam exhibits a negative stiffness. The resonant frequency will remain at ~3.1 Hz when the mechanism is vertical. d The experimental force-displacement result is plotted along with the FEA result and the theoretical result for comparison (according to ref. 35, the gravitational acceleration of our laboratory is 979 Gal)