Collapse of the superhydrophobic state on nanostructured surfaces

Orateur : Dr. Antonio CHECCO (Condensed Matter Physics and Materials Science Department Brookhaven National Laboratory Upton, NY 11973 - USA)

Coatings with extreme water-repellency or “superhydrophobic” feature elaborate surface textures designed to repel liquids by trapping air. However, these materials fail when the liquid is forced inside the texture by an external pressure. Textures with nanometer-size features may exhibit more robust superhydrophobicity owing to the large capillary pressure required to infiltrate small features. We study the collapse of superhydrophobic state in densely-packed cylindrical, conical, and linear grating silicon nanostructures with characteristic dimensions smaller than 20 nanometers, all defined by block copolymer self-assembly and plasma etching. In situ measurements of pressure-induced water infiltration into the hydrophobic nanotextures using transmission small angle X-ray scattering show that superhydrophobicity breaks down irreversibly above a critical pressure defined by the texture feature size and shape. However, upon liquid depressurization, the gas phase spontaneously nucleates into the texture to an extent depending on the nanotexture geometry and the kinetics of gas-liquid exchange. These results are relevant to the design of thermodynamically robust superhydrophobic coatings.

Télécharger dans mon agenda