Integrated Janus membrane for smart “dual fluid diode’’ with multifunctional applications

A facile “plug-and-go” strategy for the fabrication of Janus membranes (JMs) is proposed that uses different combinational substrates with opposite wettability, and some suitable substrates are tightly integrated through a certain pressure. The excellent compactness and controllability of the optimal JMs using foam Ni and superhydrophilic Cu mesh are demonstrated in multifunctional applications, including unidirectional liquid transportation in air–water systems, on-demand immiscible oil–water separation, droplet collection in liquid–liquid systems, and on–off switch control. The dual function of the resulting JMs as water and oil diodes is attributed to the interpenetrating structure and similar thicknesses of the formed hydrophobic and hydrophilic layers, which minimize the penetration distance of the Janus membrane in both directions. This strategy provides a common route for the fabrication of novel composite materials with greater diversity and composability regarding membrane pore size and thickness. Graphic abstract