A bistable shape memory microvalve for three-way control

This paper reports on the design, fabrication and performance of a novel bistable three-way shape memory microvalve for diverting and mixing applications. A symmetric arrangement of two counteracting shape memory alloy (SMA) microbridges is used for switching. Magnetic microstructures provide magneto-static contact forces in power-off condition allowing for stable open and closed states. A detailed design study on the geometry of magnetic microstructures and of spacer layers is performed to meet the requirements of large pressure range and identical flow performance in the outlet ports. The overall dimensions of first demonstrators are 11×6×4 mm³. Bistable operation is shown for a differential pressure up to 300 kPa at flow rates of 2200 sccm (N₂).