A Supraparticle-Based Approach to Robust Biomimetic Superhydrophobic Coatings

Repellent surfaces provide resistance to biofouling, ice formation, bacteria adhesion, or corrosion. Inspired by the hierarchical structure of the lotus leaf, such surfaces minimize water adhesion through micro- and nanostructuring. Conventional fabrication methods to mimic the lotus leaf often involve problematic fluorinated compounds, sophisticated preparation conditions, or lack mechanical robustness. This study presents a fluorine-free, scalable approach for fabricating durable superhydrophobic coatings using supraparticles. Supraparticles are structured aggregates of colloidal primary particles and serve as intermediate building blocks that provide hierarchical surface roughness. These supraparticles are fabricated by spray drying and introduce hydrophobic surface properties via alkyl-silanes. These preassembled structures are then simply spray coated onto a polymeric primer layer to create a coating with hierarchical roughness features, mimicking the surface of the lotus leaf. The performance of the coatings is assessed by water contact angles, contact angle hystereses, roll-off angles, and water droplet pinning fraction, and shows how the robustness can be enhanced by the addition of binder and choice of primer layer. The method offers an experimentally simple, scalable, and versatile process strategy for robust superhydrophobic coatings.