A micromachined silicon valve driven by a miniature bi-stable electro-magnetic actuator

In this paper a novel combination of a micromachined silicon valve with low dead volume and a bi-stable electromagnetic actuator produced by conventional machining is presented. The silicon valve part, 7×7×1 mm3 in dimensions, is a sandwich construction of two KOH etched silicon wafers with a layer of chemical resistant silicone rubber bonded in between. This middle layer provides the flexibility needed to move the valve boss positioned in the top wafer during valve operation, but also results in improved sealing if the valve is closed. In order to drive the valve, a dedicated bi-stable electromagnetic actuator has been designed by applying a finite element software package. The resulting actuator consists of a spring-biased armature that can move 0.2 mm up and down in a magnetically soft iron housing, incorporating a permanent magnet and a coil. This large stroke makes the valve particle tolerant. A major advantage of the bi-stable design is that only electrical energy is needed to switch the valve between the open and closed state. The actuator has been manufactured by conventional machining and was attached to the individual silicon valve parts resulting in a valve with a footprint of 7×7 mm2 and a height of 21 mm. The valve showed an open/closed ratio of more than 100 at 0.1 bar.