Superhydrophobic surfaces exhibit elaborate textures designed to repel liquids and reduce adhesion by trapping air. However, they fail under conditions involving high temperature, pressure, and humidity when the air trapped in the texture is prone to escape. A current research challenge is to improve the robustness of these surfaces by delaying or preventing air escape.Here we describe a novel, block copolymer based fabrication approach for creating robust water repellent surfaces with well-defined textures at the 10 nm scale[1]. We show that tuning the nanostructure shape and aspect ratio dramatically influences the surface wetting properties, with proper control crucial for achieving robust superhydrophobicity. Further, we characterize the robustness of the various nanotextures against forced water infiltration using transmission small angle x-ray scattering under variable hydrostatic pressure up to 50 atm. In these experiments, the infiltration filling fraction (under variable applied pressure) is obtained from the intensity of the diffracted signal. In all structures, significant infiltration occurs irreversibly above a critical pressure depending on the texture size and geometry. The detailed adsorption isotherms are well modeled by accounting for the specific shape of the nanotexture's geometry. Further, the desorption isotherms provide insight in to the irreversible gas-liquid exchange in nano-confined systems.[1] Checco, A., Rahman, A. and Black, C. T. (2013), Robust Superhydrophobicity in Large-Area Nanostructured Surfaces Defined by Block-Copolymer Self Assembly. Adv. Mater.. doi: 10.1002/adma.201304006

Breakdown of superhydrophobicity of nanotextured surfaces

247th National Meeting (2014)

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