Sliding of water-glycerol mixture droplets on hydrophobic solid-liquid bulk composites using Ti plates with a fibrous TiO2 layer

摘要

Fibrous TiO2 layer was formed on a metal Ti plate by soaking it in a KOH solution and subsequently firing it in air at 600 A degrees C for 2 h. Hydrophobic solid-liquid bulk composite (SLBC) was prepared by impregnation of a commercial silicone-based oil into the fibrous TiO2 layer after coating with fluoroalkylsilane. Based on the spreading coefficients from interface energies, the topmost solid surface of the SLBC was covered by the oil film when a water-glycerin mixture droplet was placed on the surface. The mixture droplets slid down the SLBC with acceleration. Particle image velocimetry (PIV) analysis revealed rolling and slipping modes in the sliding of the mixture droplets on the SLBC surface. During sliding, the coefficient of the viscous drag force was correlated with the velocity ratio (U (total)/U (slip)). Results suggest that the estimation of the internal fluidity of the liquid droplet was feasible to some degree by evaluating the coefficient during droplet sliding with constant acceleration on the SLBC surface.