Development of polymer micro check valve for cerebrospinal fluid shunt system

We developed the micro cerebrospinal fluid (CSF) shunt valve with surface and bulk micromachining technology of MEMS. This micro CSF shunt valve was formed with four micro check valves to have a membrane connected to the anchor with the four bridges. The up and down movement of the membrane made the CSF shunt operation, and the valve characteristics such as open pressure was controlled by the thickness and shape of the bridge and the membrane. The membrane, anchor and bridge layer were made of the O₂ RIE (reactive ion etching) patterned Parylene thin film to be about 5-10 microns in thickness on the silicon wafer. The dimension of the rectangular nozzle is 0.2 ^* 0.2 mm² and the membrane 0.45 mm in diameter. The bridge width is designed variously from 0.04 mm to 0.12 mm to control the valve characteristics. To protect the membrane and bridge in the CSF flow, we developed the packaging system for the CSF micro shunt valve with the deep RIE of the silicon wafer. Using this package, we can control the gap size between the membrane and the nozzle, and protect the bridge not to be broken in the flow. The total dimension of the assembled system is 2.5 ^* 2.5 mm² in square, 0.8 mm in height. We could precisely control the burst pressure and flow rate of the valve varing the design parameters, and develop the CSF shunt system using micro valve fabricated with MEMS technology.