Planar micro-check valves exploiting large polymer compliance

This paper presents three types of microfabricated planar check valves that exploit the large compliance of elastomeric polymers such as polydimethylsiloxane (PDMS). The micro-check valves consist of a thin compliant flap and a rigid stopper embedded in close proximity in a microchannel. The flap is perpendicular to the flow and lies near the stopper, forming a restricted fluid path inside the channel. The shape and size of the gap between the flap and stopper vary with the applied pressure, resulting in large flow resistance for forward flow and small resistance for reverse flow. The microfabricated valves have either two- or three-dimensional arrangement of valving elements. In particular, a interesting normally closed check valve was designed and fabricated using a special technique, in which the flap and stopper are, as fabricated, in intimate contact and form a zero-gap between them. Testing results show that the check valves can achieve a diodicity up to 105. The check valves can be fabricated using the standard replica molding technique from PDMS, and thus are highly amenable to integration with other PDMS-based microfluidic systems. The planar check valves can potentially used in lab-on-a-chip systems due to its high diodicity, planar configuration and use of inexpensive polymeric materials.