“Fluid plug” microfluidic valve for low Reynolds number fluid flow selector units

A novel no-moving-part valve was developed mainly for applications in microchemistry, where Reynolds numbers tend to be extremely low. The valve of very small size and working with viscous biological fluids was designed for operating at Re values between 10 and 100. In this range, the inertial jet flow effects used in standard fluidics could not be relied upon and a qualitatively new operating principle was introduced: the control fluid forms a “plug” at the entrance of the collector, precluding an entry of the main fluid flow. In particular, an array of new valves was used in a selector unit to allow a single reagent flow into a reactor from several available sources. The flow visualization validated the assumptions on which the design is based and compared well with numerical flowfield computations.