Janus copper mesh with asymmetric wettability for on-demand oil/water separation and direction-independent fog collection

Traditional preparation methods of Janus membranes are either too complicated or cannot accurately control their characters such as surface wettability , layer thickness, and pore structure. Herein, asymmetric wettability and layer thickness on the copper mesh were successfully regulated by an interface-confined surface engineering strategy and applied for liquid manipulation. Water droplets can spontaneously infiltrate from the superhydrophobic side to the superhydrophilic side of the as-prepared Janus copper mesh (JCM), achieving unidirectional transportation. Besides, the separation efficiency of the JCM exceeds 99.2%, whether it is a combination of light or heavy oil-water mixtures. Moreover, compared to the corresponding superhydrophilic and superhydrophobic meshes, the JCM showed a 200% increase in fog collection. A fog collector with a sandwich structure was further developed, making up of a superhydrophilic inner layer and double-deck superhydrophobic external layers that always play a role of a Janus collector to allow a continuous and high-performance fog harvesting regardless of the direction of the fog flow. Overall, this work provides a new idea in the fabrication of Janus membranes, which could be extended to the transport of directional water, switchable oil/water separation, fog collection, and other fields.