Design and characterization of a passive flow control valve dedicated to the hydrocephalus treatment

A passive valve able to deliver a constant flow rate independently of inlet pressure changes is proposed. The valve, which comprises a hollow cylinder, a piston engraved with a helical groove, a spring and two fluidic connectors, is adapted by design to high pressures and high flow rates. However, it has been shown that this technology is also suitable for the drainage of cerebrospinal fluid at 20 mL/h from the brain ventricles to the peritoneal cavity. To that end, a valve in titanium has been machined and tested at very low pressure using water. Despite small mismatches between theoretical and measured spring stiffness, the experiments confirm the valve's ability to deliver a substantially constant flow rate in the range from +10 to +35 mbar. To balance the effect of gravity, a hollow piston in PEEK that exhibits an overall density equal to that of the fluid has been tested with success. The effect of friction between the piston and the cylinder is also discussed.