Bio-inspired polydimethylsiloxane-functionalized silica particles - epoxy bilayer as a robust superhydrophobic surface coating

A robust superhydrophobic bilayer coating is developed containing polydimethylsiloxane (PDMS)-functionalized silica particles on top and an epoxy bonding layer at the base. It is fabricated with a facile dip-coating process that embeds micron-scale PDMS-functionalized silica particles with nano-scale roughness into an epoxy layer spin-coated onto a substrate. The dip-coating process uses multiple cycles to generate a repeatable and consistent coating onto a glass substrate. The resulting bilayer coating is able to be applied to multiple surfaces where the conventional epoxy coating is used. The concentration of silica particles was systematically varied, showing minimal influence on hydrophobicity and mechanical properties. The robustness of the coating is characterized by observing the wear properties and integrity of the rough surface as it is scratched with a stainless steel probe, while adhesive tape was applied repeatedly to the surface to observe any modification to the hydrophobicity. Additionally, a different substrate material, a transparent flexible polymer, has been successfully coated. This work demonstrates a facile dip-coating process using commercially available silica micro/nanoparticles to generate a robust superhydrophobic coating with the potential for a larger scale application to improve on the performance of conventional epoxy coatings.