A thermoresponsive valve to control fluid flow in microfluidic paper-based devices

Abstract Microfluidic paper-based analytical devices (μPADs) have recently attracted the attention of researchers and industry owing to their various advantages. However, µPADs lack a way control fluid flow; therefore, it is difficult perform complex immunoassays that use multiple reagents replace from area. We developed controllable thermoresponsive valve for μPADs by functionalizing polyvinylidene difluoride porous membrane with plasma-induced graft polymerization poly( N -isopropylacrylamide) (PNIPAAm), which polymer changes its hydrophilic properties near lower critical solution temperature (LCST; 32 °C). Surface analysis attenuated total reflectance Fourier transform infrared spectroscopy confirmed fabricated valves coated PNIPAAm. The performance was evaluated sandwiching between two paper microchannels stacked in T-shaped microfluidic device. monomer concentration ranging 2.3 3.0 wt% time 5 h or 2.0 20–22 showed good performances. These were able stop flow at room temperature, allow opening within 20 s after heating initiated using Peltier element located just under valve. successfully closed, thereby stopping flow, opened heating. Although detailed evaluation behavior necessary, we demonstrated our can be closed reversibly control. believe this could potentially used µPADs.