Journal article

Silica nano-particle super-hydrophobic surfaces: the effects of surface morphology and trapped air pockets on hydrodynamic drainage forces

Derek YC Chan, Md Hemayet Uddin, Kwun L Cho, Irving I Liaw, Robert N Lamb, Geoffrey W Stevens, Franz Grieser, Raymond R Dagastine

FARADAY DISCUSSIONS | ROYAL SOC CHEMISTRY | Published : 2009

Abstract

We used atomic force microscopy to study dynamic forces between a rigid silica sphere (radius approximately 45 microm) and a silica nano-particle super-hydrophobic surface (SNP-SHS) in aqueous electrolyte, in the presence and absence of surfactant. Characterization of the SNP-SHS surface in air showed a surface roughness of up to two microns. When in contact with an aqueous phase, the SNP-SHS traps large, soft and stable air pockets in the surface interstices. The inherent roughness of the SNP-SHS together with the trapped air pockets are responsible for the superior hydrophobic properties of SNP-SHS such as high equilibrium contact angle (> 140 degrees) of water sessile drops on these surfa..

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