Controlling flow in microfluidic channels with a manually actuated pin valve.

There is a need for a simple method to control fluid flow within microfluidic channels. To meet this need, a simple push pin with a polydimethylsiloxane (PDMS) tip has been integrated into microfluidic networks to be placed within the microchannel to obstruct flow. This new valve design can attain on/off control of fluid flow without an external power source using readily-available, low-cost materials. The valve consists of a 14 gauge (1.6 mm) one inch piece of metal tubing with a PDMS pad at the tip to achieve a fluidic seal when pressed against a microfluidic channel's substrate. The metal tubing or pin is then either manually pushed down to block or pulled up to allow fluid flow. The valve was validated using a pressure transducer and fluorescent dye to determine the breakthrough pressure the valve can withstand over multiple cycles. In the first cycle, the median value for pressure withstood by the valve was 8.8 psi with a range of 17.5-2.7 psi. The pressure the valves were able to withstand during each successive trial was lower suggesting they may be most valuable as a method to control the initial introduction of fluids into a microfluidic device. These valves can achieve flow regulation within microfluidic devices, have a small dead volume, and are simple to fabricate and use, making this technique widely suitable for a range of applications.