“Sesame Cake-like” Polymer-Inorganic Nanocomposite Coating with Dual Hydration Barriers for Robust Anti-Crude-Oil-Fouling and Long-Term Anti-Fogging

Transparent superhydrophilic coatings exhibiting underwater superoleophobic behavior have garnered significant interest for their promising functionality in fogging resistance and oil repellent applications. However, the development of such coatings with effective anticrude-oil-fouling properties presents a formidable challenge, as conventional approaches to mitigate high-viscosity crude oil adhesion often compromise optical transparency. Herein, we report a bioinspired "double-defense" strategy that integrates a polydopamine/polyethylenimine-dextran (PDA/PEI-D) hydrogel layer with a biomimetic mineralized magnesium phosphate (MP) layer to construct a hierarchical "sesame cake-like" superhydrophilic coating. This unique architecture demonstrates exceptional crude-oil-repellency and long-term antifogging performance. With the "double-defense" design strategy, the synergistic effect of the second defense hydrogel layer (cake layer) and the first defense MP layer (sesame layer) enhances the hydration capacity of the PDA/PEI-D/MP coating, ensuring superior crude-oil-repellent and antifogging properties. Moreover, the uniformly distributed discrete MP nanoparticles on the PDA/PEI-D/MP coating surface minimize light scattering while maintaining the coating's optical transparency (>90% transmittance). The "sesame cake-like" PDA/PEI-D/MP coating maintains high transparency and crude-oil-repellent and fogging resistance even after a series of durability tests and can be widely used in underwater optics, microfluidic systems, and oily wastewater treatment.