Fish-Scale-Inspired\nUnderwater Superoleophobic Nanosurface\nfor Efficient Oil–Water Separation and Manipulation

The spontaneous extraction of organic\nimmiscible liquids using\noil-repellent membranes holds substantial research significance, particularly\nin the domain of oil–water mixture separation. However, the\ndevelopment of such membranes is inherently challenging due to the\ntraditionally complex and multistep fabrication processes. This work\nintroduces a single-step hydrothermal approach to engineer a surface\nwith exceptional underwater–oil-repellent properties. Through\na hydrothermal reaction, nanoneedles are deposited onto porous hydrophobic\nnickel foam, imparting it with superhydrophilicity in air and underwater\nsuperoleophobicity. The resultant membrane demonstrates gravity-driven\nseparation of immiscible organic liquid mixtures, achieving an impressive\nseparation efficiency of up to 99.6% and an extraordinary flux of\n33,839 L m<sup>–2</sup> h<sup>–1</sup>. The nanoneedles\nexhibit negligible oil droplet adhesion and an exceptionally low underwater–oil\nsliding angle. The unique low oil adhesion properties of the membrane\npermit seamless underwater manipulation and the transport of immiscible\norganic microdroplets without any loss. Utilizing its antioil adhesiveness,\nthe membrane facilitates oil transportation in a drop-to-drop configuration,\nshowcasing its potential for sophisticated applications in oil-based\nmicroreactors. Furthermore, the membrane exhibits admirable reusability,\nchemical and thermal stability, and robust resistance to salinity\nand temperature fluctuations. The simplified fabrication process offers\na promising method for producing oil-repellent membranes with profound\nimplications for applications in diverse and demanding underwater\nenvironments. Potential applications include oil spill remediation,\nunderwater–oil transport, precise reagent transfer, and the\ndevelopment of droplet-based reactors.