Direct Observation of Water Droplet Motion on a Hydrophobic Self-assembled Monolayer Surface under Airflow

Abstract

A wind tunnel to produce a uniform air stream and a high-speed camera system assembled for this study enabled direct and simultaneous measurements of sliding droplets’shape and acceleration. Using this system,wind velocity dependence of deformation and the moving acceleration of a water droplet on an inclined octadecyltrimethoxysilane (ODS)coating were investigated. The motions of a water droplet in an air stream are classifiable into three： sliding, stopping, and climbing. In the sliding zone, the sliding acceleration decreases with increasing wind velocity. During stopping, the droplet shape changes from a forward-bent to backward-bent posture against the surface inclination. In the climbing zone under large wind velocity,water droplets have large climbing acceleration with large shape deformation. :Hydrophobicity,Wind,Droplet,