Paper-based superhydrophobic coatings for sustainable functional interfaces: Wetting mechanisms, fabrication strategies, material design, performance evaluation, and application prospects

Paper-based materials are sustainable and lightweight alternatives to plastics, but their inherent hydrophilicity limits their use in moisture-sensitive applications. Superhydrophobic coatings provide an effective strategy for regulating liquid interactions with cellulose surfaces. This review examines paper-based superhydrophobic coatings from the perspective of substrate-specific interface engineering, with emphasis on wetting behavior, capillary wicking, coating stability, and application performance. Fabrication routes such as particle deposition, phase separation, layer-by-layer assembly, printing, and chemical grafting construct hierarchical interfaces through different mechanisms, while differing substantially in coating uniformity, scalability, interfacial adhesion, and mechanical durability. The analysis shows that stable superhydrophobicity on porous paper depends on the coordinated control of hierarchical roughness, low surface energy, coating–fiber adhesion, and pore-structure accessibility, whereas liquid wicking and Cassie-to-Wenzel transitions remain major causes of performance deterioration during mechanical deformation and wet-dry cycling. Particle-polymer composites and multifunctional hybrid architectures can improve interfacial cohesion and structural stability, while bio-based and fluorine-free systems offer a more sustainable route for food packaging but require further improvements in barrier properties, durability, and food-contact safety. For food packaging, a high water contact angle alone is not sufficient to demonstrate application suitability. Performance should instead be assessed by combining wettability with grease resistance, oxygen transmission rate, water vapor transmission rate, coating adhesion, folding and abrasion resistance, overall and specific migration, sensory effects, and preservation efficacy under the intended conditions of use. Translation from laboratory demonstrations to practical packaging therefore requires integrated optimization of liquid repellency, barrier performance, mechanical robustness, food-contact safety, scalable processing, and end-of-life compatibility.