Hydrophobic surfaces with tunable dynamic wetting properties via colloidal assembly of silica microspheres and gold nanoparticles

Hierarchically structured surfaces have been fabricated using a simple colloidal bottom-up approach. The substrates exhibit a wide range of wettability properties, expressed by water contact angles ranging from 110 ∘ to 166 ∘ . The liquid–solid adhesive characteristics vary from very sticky to non-sticky, exhibited by very large and negligible sliding angles, respectively. Silica spheres with diameters in the range 130–850 nm comprise the larger length scale entities in the hierarchical superstructures, while gold nanoparticles with diameters 13–45 nm are included as the smaller length scale features. Surfaces are derivatized with suitable chemical agents to render them (super)hydrophobic. Dynamic wetting properties in terms of contact angle hysteresis and sliding angles are discussed in relation to the surface morphology.