A colloidal route to fabricate hierarchical sticky and non-sticky substrates

We present a facile and inexpensive bottom-up colloidal route to prepare sticky superhydrophobic surfaces and non-sticky ones. Either spin coating to assemble silica microspheres into random multilayered arrays or irreversible adsorption of gold nanoparticles is used to manufacture substrates with a single length scale roughness. Hierarchical roughness with multiple length scales is achieved by decorating the silica spheres with gold nanoparticles. The surface chemistry of the silica surfaces is modified by the adsorption of fluoroalkylsilane self-assembled monolayers, while gold nanoparticles are hydrophobized by dodecanethiol. The wetting properties, both static and dynamic, of surfaces in relation to the morphology of the substrates are addressed. We demonstrate the role of hierarchy in the roughness in converting a sticky into a non-sticky superhydrophobic surface and discuss the results in terms of existing models describing wetting characteristics.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (399 K)Download as PowerPoint slideHighlights► We present a facile colloidal route to manufacture hierarchical superstructures. ► Hierarchical multi-length scale roughness is achieved by bottom-up colloidal assembly. ► Wetting properties are studied in direct relation to the substrate morphology. ► We confirm that at least two length scales are required to achieve superhydrophobicity.