Fabrication of mechanically durable superhydrophobic wood surfaces using polydimethylsiloxane and silica nanoparticles

Abstract

The excellent properties of wood utilized as an engineering material are detracted by the complex wood–water interactions and the resulting dimensional instability and low durability against biological degradation. Inspired by the lotus effect, mechanically durable superhydrophobic coatings were successfully fabricated on intrinsically heterogeneous wood substrates by simply dip-coating in suspensions of hydrophobic silica (SiO₂) nanoparticles dispersed in polydimethylsiloxane (PDMS) solution. Subsequent low-surface-energy treatment with some expensive reagents is not necessary owing to the hydrophobic nature of PDMS and the modified silica particles. The surface microstructure, roughness and wetting behavior of the PDMS–silica hybrid coatings on wood surfaces were investigated in relation to the loadings of the silica particles in the PDMS matrix. When the silica particle loading reached a critical level, desirable hierarchical micro/nanostructures were formed on the wood substrate, allowing for the generation of superhydrophobicity with a contact angle of 152° and a sliding angle of less than 10°. The fabricated PDMS–silica hybrid coating exhibited desirable durability against mechanical abrasion and high-frequency ultrasonic washing in water whilst basically retaining its microstructure and superhydrophobicity. Such mechanically durable superhydrophobic wood surfaces with self-cleaning properties offer an interesting alternative for wood modification, and could improve the performance of wood as an engineering material.