Fabrication of bunny ear cactus- mimicking superhydrophobic silica coatings on marble to protect architectural heritage

Abstract The TEOS–PDMS-based superhydrophobic silica coatings for Carrara marble presented in this work is intended to improve the protection of historic buildings against water and pollution-induced damage. This method effectively preserves marble-built cultural heritage by optimizing TEOS:PDMS ratios and processing conditions to provide superhydrophobicity and durability. In this study, a marble was coated with a homogeneous mixture of polystyrene and polydimethylsiloxane-modified silica particles through spray coating. Surface analysis of the coated marble demonstrated a uniform layer of coatings, resulting in a hierarchical surface structure that mimics the Bunny Ear Cactus leaf surface. The coated marble exhibited a water contact angle (WCA) of 168.5 ± 2.5°, underscoring its exceptional water repellency, alongside a water sliding angle (WSA) of 4 ± 1°, which indicates quick droplet runoff. In investigating the mechanical durability, the as-prepared superhydrophobic coating has demonstrated high robustness when subjected to rigorous tests such as adhesive tape tests, sandpaper abrasion, water droplet impact, and sand grain impact. Moreover, the developed superhydrophobic coating exhibited chemical resistance and thermal stability in harsh conditions. The potential applications of such formulation could effectively enhance conservation efforts aimed at preserving the integrity and aesthetic value of architectural heritage.