Liquid-like PDMS brush/TiO₂ interface for photocatalytic self-renewal in persistent emulsion separation

Efficient treatment of water-in-oil emulsions remains challenging, primarily due to surfactant-induced droplet stabilization and rapid membrane fouling that causes pore blockage and flux decay. In this study, we develop a light-responsive liquid-like separation surface by grafting linear polydimethylsiloxane (PDMS) chains onto TiO₂-modified stainless steel mesh. The grafted PDMS brush forms a mobile, low-adhesion interface that promotes droplet detachment and suppresses organic deposition, while the TiO₂ nanoparticles generate reactive oxidative species under UV irradiation to degrade residual contaminants. This dual-action design enables continuous gravity-driven separation of immiscible oil/water mixtures and surfactant-stabilized emulsions. The membrane maintains superoleophilicity in air and strong water repellency in oil, ensuring selective transport of the oil phase. Critically, UV illumination rapidly restores flux after fouling, and the separation efficiency remains above 85 % over repeated cycles. The synergistic integration of dynamic PDMS brush and photocatalytic self-cleaning presents a simple and scalable route for developing durable antifouling interfaces for long-term emulsion purification and potentially broader waste-oil treatment applications.