Video-based Metrology of Water Droplet Spreading on Nanostructured Surfaces

Dynamic wettability of a nanostructured surface is an important property for many liquid-related applications of nanostructures. The dynamic wettability analysis is performed by measuring the evolution of the precursor (outer rim) contour of a water droplet as it spreads on a nanostructured surface. A video-based metrological system based on the snake active contour model which is capable of precisely tracking the precursor contour of a spreading water droplet in a high frame-rate video is developed. The radius of the precursor contour is empirically observed to obey a power law with respect to time. Experiments show reasonable agreement between the results of the metrological system and those obtained via manual measurement.