Probing effective slippage on superhydrophobic stripes by atomic force microscopy

• Published in: Soft matter 2016-08, Vol.12 (33), p.691-6917
• Main Authors: Nizkaya, Tatiana V, Dubov, Alexander L, Mourran, Ahmed, Vinogradova, Olga I
• Format: Article
• Language: English
• Subjects: Computational fluid dynamics; Mathematical analysis; Mathematical models; Planes; Slip; Slippage; Surface layer; Texture
• ISSN: 1744-683X; 1744-6848
• DOI: 10.1039/c6sm01074a

While the effective slippage of water past superhydrophobic surfaces has been studied over a decade, theoretical predictions have never been properly confirmed by experiments. Here we measure a drag force on a sphere approaching a plane decorated by superhydrophobic grooves and compare the results with the predictions of semi-analytical theory developed here, which employs the gas cushion model to calculate the local slip length at the gas sectors. We demonstrate that at intermediate and large (compared to a texture period) separations the half-sum of longitudinal and transverse effective slip lengths can be deduced from the forcedistance curve by using the known analytical theory of hydrodynamic interaction of a sphere with a homogeneous slipping plane. This half-sum is shown to depend on the fraction of gas sectors and its value is in excellent agreement with theoretical predictions. At small distances the half-sum of effective longitudinal and transverse slip lengths becomes separation-dependent, and is in quantitative agreement with the predictions of our semi-analytical theory. We measure a drag force on a sphere approaching a plane decorated by superhydrophobic grooves and deduce the half-sum of longitudinal and transverse effective slip lengths of the surface, which is found to be in agreement with our theoretical predictions.