Superhydrophobic silicon surfaces with micro–nano hierarchical structures via deep reactive ion etching and galvanic etching

An effective fabrication method combining deep reactive ion etching and galvanic etching for silicon micro–nano hierarchical structures is presented in this paper. The method can partially control the morphology of the nanostructures and enables us to investigate the effects of geometry changes on the properties of the surfaces. The forming mechanism of silicon nanostructures based on silver nanoparticle galvanic etching was illustrated and the effects of process parameters on the surface morphology were thoroughly discussed. It is found that process parameters have more impact on the height of silicon nanostructure than its diameter. Contact angle measurement and tilting/dropping test results show that as-prepared silicon surfaces with hierarchical structures were superhydrophobic. What’s more, two-scale model composed of micropillar arrays and nanopillar arrays was proposed to study the wettability of the surface with hierarchical structures. Wettability analysis results indicate that the superhydrophobic surface may demonstrate a hybrid state at which water sits on nanoscale pillars and immerses into microscale grooves partially.

Superhydrophobic silicon surfaces with micro–nano hierarchical structures were fabricated by deep reactive ion etching and galvanic etching. Wettability analysis using two-scale model composed of micropillar and nanopillar arrays indicated that superhydrophobic surface may demonstrate a hybrid wetting state.Figure optionsDownload high-quality image (129 K)Download as PowerPoint slideHighlights
► A novel fabrication method for silicon hierarchical structures is presented.
► The forming mechanism and the effects of process parameters were discussed.
► CA measurement and tilting/dropping test show the surfaces were superhydrophobic.
► Two-scale model composed of micropillar and nanopillar arrays was proposed.
► Superhydrophobic surface may demonstrate a hybrid wetting state.