Bio-inspired membrane with adaptable wettability for smart oil/water separation

Adaptable wettability is an intriguing property found in nature yet rare in synthetic materials. Separation membranes bearing this adaptable wettability would be of great significance for practical applications because they can achieve on-demand oil/water separation according to the intrinsic properties of the targeting oil/water mixtures other than external stimuli. Herein, we report one novel type of such smart separation membranes by functionalizing steel mesh membrane with polydopamine (PDA) and an amphiphilic synthetic copolymer via a feasible mussel-inspired dip-coating method. The resulting membrane possesses excellent adaptable wettability and can switch their special oil/water wettability to selectively activate "water-removing" or "oil-removing" modes for on-demand collection of the desired component (water or oil) from the oily water, i.e., upon pre-wetting the surfaces with water or oil. It exhibits outstanding performance in separating various immiscible oil/water mixtures and miscible surfactant-stabilized emulsions under ambient pressure. Moreover, the bio-inspired membrane can be regenerated and reused facilely through simple washing and drying process without loss in performance. The facile surface functionalization approach developed in this work is universal and substrate-independent, which can be extended to a variety of materials and membrane systems. Such universal surface modification method and the novel membrane developed have great application potential in various engineering and environmental areas including oil spill cleanup and industrial wastewater treatment.