Adhesion-Dependent Receding Contact Line Dynamics of Water Droplets and Residual Droplet Deposition on Inclined Grooved Hydrophobic Surfaces

Surface adhesion is a key design parameter in applications of grooved hydrophobic surfaces, such as liquid transport and selective deposition of solid particles. Despite its importance, a systematic understanding of how surface adhesion governs receding contact line dynamics and residual droplet formation remains limited. In this study, the receding contact line dynamics of water droplets were investigated by varying the surface inclination angle, surface adhesion, and the groove-top width. At low inclination angles, droplets on more adhesive surfaces exhibited stronger contact-line pinning and slower retraction, leading to the accumulation of larger droplets on the groove tops. As the inclination angle increased, gravity-driven forcing reduced the overall solid-liquid contact area at the droplet tail; however, larger deposited droplets were still observed due to locally reduced retraction. Increasing the groove-top width further enhanced residual droplet growth in conjunction with surface adhesion. A scaling law derived from dimensional analysis provides a predictive framework for deposited droplet size. Incorporating the nonlinear relationship between surface adhesion and mixing ratio enabled all experimental data to collapse onto a single master curve, offering guidance for the design of grooved hydrophobic surfaces with controlled droplet retention.