Fish-Scale-Inspired Underwater Superoleophobic Nanosurface for Efficient Oil–Water Separation and Manipulation

The spontaneous extraction of organic immiscible liquids using oil-repellent membranes holds substantial research significance, particularly in the domain of oil–water mixture separation. However, the development of such membranes is inherently challenging due to the traditionally complex and multistep fabrication processes. This work introduces a single-step hydrothermal approach to engineer a surface with exceptional underwater–oil-repellent properties. Through a hydrothermal reaction, nanoneedles are deposited onto porous hydrophobic nickel foam, imparting it with superhydrophilicity in air and underwater superoleophobicity. The resultant membrane demonstrates gravity-driven separation of immiscible organic liquid mixtures, achieving an impressive separation efficiency of up to 99.6% and an extraordinary flux of 33,839 L m^–2 h^–1. The nanoneedles exhibit negligible oil droplet adhesion and an exceptionally low underwater–oil sliding angle. The unique low oil adhesion properties of the membrane permit seamless underwater manipulation and the transport of immiscible organic microdroplets without any loss. Utilizing its antioil adhesiveness, the membrane facilitates oil transportation in a drop-to-drop configuration, showcasing its potential for sophisticated applications in oil-based microreactors. Furthermore, the membrane exhibits admirable reusability, chemical and thermal stability, and robust resistance to salinity and temperature fluctuations. The simplified fabrication process offers a promising method for producing oil-repellent membranes with profound implications for applications in diverse and demanding underwater environments. Potential applications include oil spill remediation, underwater–oil transport, precise reagent transfer, and the development of droplet-based reactors.