Control of microfluidic flow in amphiphilic fabrics.

Woven textile fabrics were designed and constructed from hydrophilic and hydrophobic spun yarns to give planar substrates containing amphiphilic microchannels with defined orientations and locations. Polypropylene fibers were spun to give hydrophobic yarns, and the hydrophilic yarns were spun from a poly(ethylene terephthalate) copolyester. Water wicking rates into the fabrics were measured by video microscopy from single drops, relevant for point-of-care microfluidic diagnostic devices, and from reservoirs. intra-yarn microchannels in the hydrophilic polyester yarns were shown to selectively transport aqueous fluids, with the flow path governed by the placement of the hydrophilic yarns in the fabric. By comparing fluid transport in fabric constructions with systematic variations in the numbers of adjacent parallel and orthogonal hydrophilic yarns, it was found that inter-yarn microchannels significantly increased wicking rates. Simultaneous wicking of an aqueous and hydrocarbon fluid into the hydrophilic and hydrophobic microchannels of an amphiphilic fabric was successfully demonstrated. The high degree of interfacial contact and micrometer-scale diffusion lengths of such coflowing immiscible fluid streams inside amphiphilic fabrics suggest potential applications as highly scalable and affordable microcontactors for liquid-liquid extractions.