Design and characterisation of an inertial microswitch with electrophoretic polymer-metal composite fixed electrode for extending contact time

Based on non-silicon surface micromachining, a single sensitive direction (z-axis) inertial microswitch with electrophoretic polymer-metal composite fixed electrode has been designed and characterised in the present work. The microswitch mainly consists of two parts: a suspended proof mass as movable electrode and maple leaf-like top as vertical electrode. When an acceleration (threshold level or over) is applied to the switch along its sensitive direction, the mass electrode will rapidly move towards and touch the vertical fixed electrode, switching on the external circuit. The vertical composite fixed electrode of the microswitch can realise a flexible contact, decrease bounce and extend the contact time between the electrodes. The fabricated microswitches have been characterised by a standard dropping test. The threshold acceleration of the prototype is about 70 g while the contact time is about 110 ms, longer than that (about 65 ms) without a polymer.