A pinch-valve for centrifugal microfluidic platforms and its application in sequential valving operation and plasma extraction

This paper presents a new pin-type valve suitable for centrifugal microfluidic platforms. The actuator for the valving system consists of a spring plunger and a flyball governor. The valve is designed to be a “normally-closed” one by using a spring plunger to pre-stress the PDMS microchannel to an initially closed state. The flyball governor drives the spring plungers to release the compression when it spins at a particular speed to open the valve. The valve demonstrated robust performances and its burst frequency can be tuned by adjusting the parameters of the mechanical system. In this paper, we characterized the operation of one single valve and two sequential valves. As a proof of concept, a sequential valving system capable of metering and centrifugal sediment was developed for plasma extraction from whole blood. The resulting residual cell concentration was less than 0.5%. This new valve design offers some major advantages over those reported in the field: simple fabrication, robust control and easy integration. It demonstrates great potential for complex fluid handling needed in biological, chemical and medical applications in Lab-on-CD systems.