Deposition of micro/macroscale water droplets on grooved hydrophobic surfaces

Abstract

Hydrophobic surfaces containing groove structures are frequently found in nature. Understanding the contact line dynamics of water droplets on such surfaces is important for analyzing the droplet motion and utilizing it for directional droplet transport. Although the visualization technique has been significantly improved, less attention has been paid to the contact line dynamics of droplets on grooved hydrophobic surfaces. Here, we fabricated hydrophobic surfaces containing grooves using a facile laser technique and visualized the advancing and receding contact line dynamics on the surfaces through high-speed imaging. In addition, the geometry of the groove structure, the droplet volume, and the inclination angle of the surface were systematically varied, and their effects on the sizes and shapes of the residual droplets deposited on the groove structures because of the sliding droplet were studied. Minute and uniform water droplets were deposited on the grooved surfaces when the structures were perpendicular to the droplet's moving path. As the droplet volume, surface inclination angle, and solid fraction of the grooved surfaces increased, the sizes of the residual droplets deposited on the grooves increased. A simple dimensionless analysis indicated that the size of the residual droplet could be predicted using the parameters tested in this study.