The preparation of superhydrophobic surfaces of hierarchical silicon nanowire structures.

Superhydrophobic surfaces are prepared by fabricating silicon nanowires to enhance the surface roughness and then modifying the chemical nature of the surface with a self-assembled octadecyltrichlorosilane monolayer to lower the surface energy. All the processes are performed near room temperature. The dynamic contact angle data demonstrate that the water droplet on these surfaces of nanowires can exhibit a transition from the Wenzel state to the Cassie state by simply controlling the etching time. The hierarchical structure is constructed by fabricating the nanopillars (i.e. nanowires) on top of the regular pillar-like silicon wafers. As a consequence, superhydrophobicity could be achieved much more effectively by applying the hierarchical structure.