A chemo-mechanical switchable valve on microfluidic chip based on a thermally responsive block copolymer

Microfluidic devices have become a powerful tool for chemical and biologic applications. To control different functional parts on the microchip, valve plays a key role in the device. In conventional methods, physio-mechanical valves are usually used on microfluidic chip. Herein, we reported a chemo-mechanical switchable valve on microfluidic chip by using a thermally responsive block copolymer. The wettability changes of capillary with copolymer modification on inner surface were investigated to verify the function as a valve. Capillaries with modification of poly-(N-isopropylacrylamide-co-hexafluoroisopropyl acrylate) (P(NIPAAm-co-HFIPA)) with a 20% HFIPA was demonstrated capable of control aqueous solution stop or go through. Then short capillaries with copolymer modification were integrated in microchannels as valves. With the temperature changing around lower critical solution temperature (LCST), the integrated chemo-mechanical switchable valve exhibited excellent “OPEN–CLOSE’’ behavior for microflow control. After optimization of the block copolymer sequences and molar ratio, a switching time as low as 20 s was achieved. The developed micro valve was demonstrated effective for flow control on microchip.