Novel passive normally closed microfluidic valve

Abstract

Microfluidic systems require numerous control valves in order to function properly. These valves form the basic unit of fluid handling within the microfluidic system. Many different valves have been designed and manufactured, both active and passive. The current paper investigates a novel passive valve that works on the principle of hydrostatic pressure. This normally closed valve can also be used in a toggle valve combination, where only one external actuation source is required to yield two valves that open and close sequentially. The first valve is an active valve, operated pneumatically. The second valve operates purely on the pressure applied by the fluid in the microfluidic channel at the valve entrance. One valve is thus always closed, while the other is open. By changing the valve entrance properties, the valve can be designed to operate at different actuation pressures. The valve mechanism, which consists of four layers of polydimethylsiloxane (PDMS), was designed and manufactured using the SU-8 lithography and replication molding processes. It was successfully implemented, and initial results show the relationship between the applied pressure and flow rate. In addition to being used as a toggle valve, this design also allows for the passive valve to be used as a stand-alone pressure valve and as a one way valve, which would restrict fluid flow to a single direction. This may give rise to the possibility of designing entirely passive microfluidic devices, which would be advantageous from a circuit complexity and energy usage perspective