Influence of applied acceleration loads on contact time and threshold in an inertial microswitch with flexible contact-enhanced structure

• An L-shape flexible cantilever as the stationary electrode to prolong contact time.
• Device is fabricated by low-cost and low temperature electroplating micromachining.
• Influence of acceleration load on contact time and threshold is evaluated.

An inertial microswitch with flexible contact-enhanced structure to prolong contact time has been designed and fabricated by surface micromachining technology. The flexible structure is an L-shaped compliant cantilever beam, which can realize elastic deformation during contact process when the movable electrode impacts to the stationary electrode. The influence of applied acceleration loads on contact time and threshold was analyzed, simulated and evaluated. The analysis results indicate that the stiffness of inertial system, amplitude and pulse width of acceleration loads are important influence factors for the contact time: the contact time will be increased along with the increase of acceleration amplitude and the decrease of inertial system stiffness. The broadening of pulse width of acceleration loads will result in a greater value of threshold acceleration and contact time. The simulated results demonstrate that the dynamic properties of designed inertial micro-switch are in agreement with the analytical ones. The fabricated microswitch has been tested by dropping hammer system, the test results indicate that the threshold acceleration is about 110g and the corresponding contact time is about 42 μs when the pulse width is about 1.7 ms. Meanwhile, the contact time increases with the broadening of pulse width. Finally, the fabricated inertial microswitch device has been also tested under applied half-sine wave acceleration with different amplitudes and pulse widths. It is indicated that the contact time does not increase after reaching to a maximum (75 μs under 259g applied acceleration load). From the analysis in the present work, the influence of applied shock loads on contact time and threshold level in an inertial microswitch with flexible contact-enhanced structure is revealed. The conclusions reached in this study provide guidance for future research into the design and fabrication of inertial microswitches.