Robust superhydrophobic surfaces fabricated by self-growth of TiO2 particles on cured silicone rubber

The sol-gel technology is an effective method for preparing inorganic superhydrophobic coatings on flexible polymer substrates. However, the interfacial bonding achieved between the polymer and inorganic particles via the conventional sol-gel method is usually poor and renders the coatings highly susceptible to damage by mechanical contact. By innovatively combining the conventional sol-gel method with the swelling characteristics of cured silicone rubber (SR), TiO2 particles were generated in the crosslinking network of SR and finally formed multiscale roughness on the surface of SR via self-growth. The ideal surface texture was controlled by synergistic effect between the swelling conditions and the sol-gel method, with contact angle and roll-off angle of 158.6 degrees and 6.5 degrees, respectively. The self-growth of the TiO2 particles in the crosslinking network of SR ensured that the TiO2 particles were 'embedded', and not 'coated', on the surface of SR, which led to improved adhesive performance and resultant mechanical durability. Superhydrophobicity was maintained even after 3200 cycles of linear abrasion. After 4000 cycles of abrasion, the TiO2 particles were partly damaged yet firmly bonded with the SR substrate. Furthermore, the 'embedding' of the TiO2 particles effectively solved the problem of detachment of nanoparticle coatings from substrates under repeated deformation. High mechanical stability and simple fabrication facilitate the use of these superhydrophobic surfaces in real-world applications.