Preparation and hydrophobicity of solid-liquid bulk composite using porous glass and fluorinated oil

摘要

Hydrophobic porous glass plates were prepared by coating a fluorosilane (FAS17) onto a commercial porous glass (average pore size, approx. 1 mu m) with surface modification by colloidal silica (approx. 100 nm). Then porous glass-fluorinated oil composites were prepared by subsequent impregnation of two fluorinated oils with similar surface energy but differing viscosity. Both the sliding angle (similar to 5A degrees A -> A similar to 0A degrees) and contact angle (similar to 150A degrees A -> A similar to 115A degrees) were decreased by impregnating fluorinated oil into the porous glass. The composites possessed excellent sustainability of their small sliding angle under exposure in turbulent water flow. The composite exhibited higher sliding velocity than that of a normal hydrophobic coating. The composite with high-viscosity oil exhibited a lower sliding velocity for a water droplet than that with low-viscosity oil. Particle image velocimetry revealed that the dominant sliding mode for water droplets on the composites was slipping. Results suggest that viscous dissipation at the wetting ridge (oil meniscus at the three-phase contact line) plays an important role in the moving behavior of water droplet on the composites. The superiority in dynamic hydrophobicity for the composites was retained even when the droplet was sandwiched between two parallel samples.