Remotely adjustable check-valves with an electrochemical release mechanism for implantable biomedical microsystem

We present two remotely adjustable check-valves with an electrochemical release mechanism for implantable biomedical microsystems. Using these valves, one can vary the opening pressure set-point and flow resistance over a period of time. In the first design, an array of remotely addressable valves with a SU-8 structural polymer layer deposited on the top of a gold sacrificial layer act as the micromachined check-valve. In an alternative design, the set point is changed by varying the length of a cantilever-beam. The adjustable cantilever-beam structure is fabricated by gold thermo-compression bond of a thin silicon wafer over a glass substrate. The evaporated gold forms anchors on the silicon and strips on the glass substrate. Adjustment of both microvalves is based on electrochemical dissolution of gold using a constant DC current obtained via a telemetry link. A current density of 35mA/cm/sup 2/ is used to activate the valves. Both gravity and syringe-pump driven flow are used to characterize the valve performance. The multistage fluidic performance (e.g. flow resistance and opening pressure) is clearly demonstrated.