Two-way bistable out-of-plane actuator using Ti/SiO2 bilayer

A novel two-way bistable bimorph bridge actuator for out of plane deflection is reported in this paper. The device has a 1200μm long, 50μm wide and 4μm thick composite bimorph beam consists of PECVD SiO2 and titanium layers. The end supports of the beam consist of 2 pairs of spring and are provided by 2 pairs of long titanium 'legs’ alongside the beam. 10mW and 4mW in the beam and legs for 3ms respectively is needed for 50 micron of out-of-plane deflection travel. By applying the appropriate joule heating sequence to the device, it is possible to snap the buckled beam upward or downward between two equilibrium states. An analytical and simulation models of heat transfer and tunable snapping are developed for the system. This paper presents the working principal, analysis, simulations of the device. The actuator will be used to move a micromirror, located at the centre of beam, for optical switching. This novel mechanism can have useful application in relays, optical switching and threshold sensors.