Semitransparent, durable superhydrophobic polydimethylsiloxane/SiO2 nanocomposite coatings on varnished wood

A superhydrophobic surface on wood can prevent water adhesion and absorption. However, the practical applications of such a non-wetting surface are hindered by the fragility of the microscopic roughness features that are essential for superhydrophobicity. In this study, semi-transparent, mechanically durable superhydrophobic coating was successfully deposited on varnished wood via a simple dip-coating method based on polydimethysiloxane (PDMS)/silica (SiO2) nanocomposites. The surface microstructure and roughness of the hybrid coatings on wood are governed by the mass ratio of SiO2 to PDMS. When the nano-SiO2 particle content reaches a critical level, dual-scale features with micro-scale roughness superimposed with a nanostructure can be formed in the surface coatings, resulting in excellent water-repellency with a contact angle above 150 degrees and a sliding angle below 10 degrees. The coated wood surface maintained essentially the original colour and aesthetic appearance despite slightly declined optical transparency of the hybrid coating caused by aggregation of silica nanoparticles. Sandpaper abrasion tests revealed that the superhydrophobic PDMS/SiO2 hybrid coating on wood retained its microstructure and superhydrophobicity after being repeatedly abraded.