Fabrics with Novel Air–Oil Amphibious, Spontaneous One-Way Water-Transport Capability for Oil/Water Separation

Porous media with directional water-transport capability have great applications in oil-water separation, moisture-harvesting, microfluidics, and moisture-management textiles. However, the previous directional water-transport materials chiefly work in the air. The materials with directional water-transport capability in the oil phase have been less reported. Here, we fabricated a novel Janus fabric with amphibious directional water-transport capability that can work both in the air and oil phases. It was prepared using dip coating and spraying to develop an oleophobic-hydrophobic to oleophobic-hydrophilic gradient across the thickness of the fabric substrate. The fabric allowed water droplets to rapidly transport from the hydrophobic to the hydrophilic side when the fabric was either in the air environment or fully immersed in oil. However, it hindered water transport in the opposite direction. More importantly, the fabric can overcome gravity to capture water from oil. Such an air-oil amphibious water-transport fabric showed excellent water collecting capability. In oil, it does not require any prewetting or extra pressure to perform directional water transport, which is vital for water-oil separation and microfluidics. Such amphibious directional water-transport function may be useful for the development of smart membranes and directional liquid delivery.