``Nanonails'' -- a Simple Geometrical Approach to ``Superlyophobic'' Surfaces

Modern nanofabrication techniques allow creation of a wide range of sophisticated surface topographies that strongly enhance wetting properties of solids. Such surfaces serve as a basis for so-called superhydrophilic and superhydrophobic materials that demonstrate a range of remarkable properties. In both of these cases the topography acts to ``amplify'' the type of wetting behavior, which is already determined by the surface energies of the liquids and solids involved. In this work we propose and experimentally demonstrate a unique three-dimensional nano-scale geometry that dramatically extends the influence of topography on the wetting properties of the substrate. Using this approach we are able to transform ordinary Teflon-like fluoropolymer surfaces, which are readily wetted by the majority of common low-surface tension liquids into nanostructured substrates with profound superlyophobic behavior. The resulting surfaces are essentially non-wetting and support highly mobile liquid droplets with contact angles close to 150\r{ } for a wide variety of liquids with surface tensions ranging from 72.0 mN/m (water) to 21.8 mN/m (ethanol). The proposed approach provides a simple, material-independent method for creating practically useful superlyophobic surfaces.