Superhydrophobic Fatty Acid-Based Spray Coatings with Dual-Mode Antifungal Activity

Superhydrophobicity, a natural phenomenon commonly observed in plants and insects, imparts diverse functionalities, including self-cleaning capabilities and antibiofouling properties. Nature's design of a superhydrophobic surface relies on a combination of surface chemistry and hierarchical roughness at micro- and nanoscales, inspiring the design of artificial superhydrophobic coatings. These multifunctional coatings offer a promising approach for combating fungal infections that are becoming increasingly prevalent due to global warming and increased resistance to conventional fungicides. Notably, among emerging superhydrophobic surfaces, those made with natural, nontoxic, and environmentally friendly compounds via facile manufacturing methods offer key advantages and support sustainable engineering practices. In this study, we developed easy-to-apply, sprayable bimodal superhydrophobic coatings. The antifungal activity of these coatings, based on long-chain fatty acids, can be further enhanced by incorporating medium-chain fatty acids, as demonstrated against the model phytopathogen Botrytis cinerea. Specifically, we investigate the effect of incorporating sorbic or caprylic medium-chain fatty acids at various concentrations on the structure, physical properties, stability, and applicability of stearic acid-based coatings. Our results show that, depending on the composition, the antifungal activity of the coatings can be tuned, ranging from complete passive antibiofouling to dominant fungicidal action against Botrytis cinerea. Enabled by the synergistic effect of the hierarchical superhydrophobic structure and the incorporation of potent medium-chain fatty acids, these coatings offer a sustainable solution for surface protection against fungal infections and represent a promising alternative to conventional antifungal strategies.