Directional liquid gating by hydrophilic/hydrophobic janus membranes

Controlling droplet and fluid transport in a directional manner represents an important form of liquid manipulation and has tremendous application potential in fields involving intelligent liquid management. We have shown theoretically that a hydrophilic/hydrophobic Janus membranes with a transmembrane chemical gradient can induce directional liquid gating due to its anisotropic liquid critical breakthrough pressure. We further experimentally prepare hydrophilic/hydrophobic Janus membranes by facile vapor diffusion method. The resultant Janus membrane evidences directional water droplet gating behavior in air-water systems. Moreover, membrane-based directional gating of continuous water flow is demonstrated, enabling Janus membranes to act as facile fluid diodes for one-way flow regulation Additionally, in oil-water systems, the Janus membranes show directional gating of droplets with integrated selectivity for either oil or water. The remarkable gating properties of the Janus membranes open new perspectives for fluid rectifying, advanced separation, biomedical materials and smart textiles.