Open-channel, water-in-oil emulsification in paper-based microfluidic devices.

Open-channel microfluidic devices have shown great potential in achieving a high degree of fluid control, at relatively low-cost, while enabling the opportunity for rapid fabrication. However, thus far, work in open channel microfluidics has largely focused on controlling the flow of water or other aqueous solutions. In this work we present new open channel microfluidic devices based on surfaces with patterned wettabilty that are capable of controlling the flow of virtually all high and low surface tension liquids. The fabricated open channel devices are capable of constraining a variety of low surface tension oils at high enough flow rates to enable, for the first time, water-in-oil microfluidic emulsification in an open channel device. By changing the flow rates for both the aqueous (dispersed) and organic (continuous) phases, we show that it is possible to vary the size of the emulsified droplets produced in the open channel device. Finally, we utilized the fabricated devices to synthesize relatively monodisperse, hydrogel microparticles that could incorporate a drug molecule. We also investigated the drug release characteristics of the fabricated particles.