Shape memory alloy based controllable multi-port microvalve

This paper describes an innovative miniature multi-port valve with a thin foil of shape memory alloy (SMA) as actuator for switching and dosing gaseous and liquid media. The normally closed (NC) microvalve has two structured SMA actuators that are switched independently of each other and either two inputs and one output or one input and two outputs. In addition to switching the media in the 3/4-way arrangement, it can also be used with a flow sensor in a closed loop control for dosing. Furthermore, the valve design is layer-based so that individual components can be manufactured according to given requirements or using different manufacturing technologies depending on the batch size. The SMA multi-port microvalve showed flow rates of about 2300 ml/min (nitrogen gas) and about 45 ml/min (water) for an applied pressure difference of 200 kPa and a heating current of about 400 mA. For flow regulation a closed loop control was realized and evaluated for a pressure difference of 100 kPa and a setpoint value of 900 ml/min.