Underwater self-cleaning scaly fabric membrane for oily water separation

Oily wastewater is always a threat to biological and human safety, and it is a worldwide challenge to solve the problem of disposing of it. The development of interface science brings hope of solving this serious problem, however. Inspired by the capacity for capturing water of natural fabrics and by the underwater superoleophobic self-cleaning property of fish scales, a strategy is proposed to design and fabricate micro/nanoscale hierarchical-structured fabric membranes with superhydrophilicity and underwater superoleophobicity, by coating scaly titanium oxide nanostructures onto fabric microstructures, which can separate oil/water mixtures efficiently. The microstructures of the fabrics are beneficial for achieving high water-holding capacity of the membranes. More importantly, the special scaly titanium oxide nanostructures are critical for achieving the desired superwetting property toward water of the membranes, which means that air bubbles cannot exist on them in water and there is ultralow underwater-oil adhesion. The cooperative effects of the microscale and nanoscale structures result in the formation of a stable oil/water/solid triphase interface with a robust underwater superoleophobic self-cleaning property. Furthermore, the fabrics are common, commercially cheap, and environmentally friendly materials with flexible but robust mechanical properties, which make the fabric membranes a good candidate for oil/water separation even under strong water flow. This work would also be helpful for developing new underwater superoleophobic self-cleaning materials and related devices.