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. Nature's design of a superhydrophobic surface relies on a combination of surface chemistry and hierarchical roughness at micro- and nano-scales. The growing interest in artificial superhydrophobic surfaces is driven by their unique properties and additional functionalities, such as anti-icing, corrosion prevention, and anti-biofouling properties. While many studies show the antibacterial properties of superhydrophobic surfaces, only a handful focus on fungi. However, fungal infections are becoming increasingly prevalent, driven by global warming and the growing resistance of fungi to conventional fungicides. Notably, among novel superhydrophobic surfaces, those made with natural, non-toxic, and environmentally friendly compounds via facile manufacturing methods, offer significant advantages and align with sustainable engineering practices. In this study, we developed an easy-to-apply, sprayable bi-modal coatings. These superhydrophobic antifungal coatings, made of long-chain fatty acid, can be combined with medium-chain fatty acids to enhance the antifungal activity against the model phytopathogen Botrytis cinerea. We investigate the effect of incorporating sorbic and caprylic fatty acids in various concentrations on the structure, physical properties, stability, and applicability of stearic acid-based coatings. We show that depending on the composition, the antifungal activity of the coatings can be tuned, ranging from complete passive antibiofouling to a dominant fungicidal action against Botrytis cinerea. This is made possible by the combination of the superhydrophobic coating's hierarchical structure and the incorporation of potent medium-chain fatty acids. We believe these coatings offer a sustainable solution for protecting various surfaces from fungal infections and represent a promising alternative to conventional fungicides.