Bi-functional Janus mesh membrane with selective spontaneous directional liquids transport for efficient on-demand separation of oil-in-water and water-in-oil emulsions

The Janus membranes with asymmetric wettability can gate oil or water transport spontaneously and directionally to facilitate the liquids transport for oil/water emulsions separation without extra energy consumption, which have attracted wide attention. However, this single-functioned either oil or water removal Janus membranes can only separate one type of emulsions and cannot meet the requirements in complex environments. Herein, a bi-functional Janus mesh membrane with selective directional oil- and water-transport integration induced by direction-directed dual asymmetric wettability is demonstrated for energetic-efficient on-demand separation of oil-in-water and water-in-oil emulsion. An ingenious double single-side asymmetric modification strategy is proposed to make a homogenous mesh membrane with special Janus interface, where one surface features oleophobicity and hydrophilicity while the other shows superhydrophobicity and oleophilicity. This direction-directed wettability imbalance gives rise to the selective directional both water and oil transport property, namely, one surface directionally transports oil and block water. In contrast, the other surface suspends the oil and directionally transports water across the membrane. According to this property, this multifunctional Janus mesh membrane achieves high-performance on-demand oil-in-water and water-in-oil emulsions separation without extra energy consumption.