Simple Approach to Superamphiphobic Overhanging Silicon Nanostructures

Abstract

Superhydrophobic silicon nanostructures were fabricated by anisotropic etching of silicon coated with a thin hydrophobic layer. At certain etch parameters, overhanging nanostructures form at the apexes of the rod-shaped tips. This leads to superoleophobic behavior for several oily liquids with contact angles up to 152° and roll-off angle down to 8°. Such nonlithographic nanoscale overhanging structures can also be added to silicon nanograss by deposition of a thin SiO2 layer, which equips the silicon rods with 100−300 nm sized overhanging structures. This is a simple, fast, nonlithographic method for introducing amphiphobic behavior on a surface consisting of vertically aligned micro- or nanostructures.