In situ investigation on dynamic suspending of microdroplet on lotus leaf and gradient of wettable micro- and nanostructure from water condensation

Dynamic suspending behavior of microdroplet on fresh lotus leaf is in situ investigated at micro- and nanolevels, by water condensation via environmental scanning electronic microscopy. The observation and analysis reveal that a gradient of wettable micro- and nanostructure is formed along the exterior surface of papilla including nanohairs during water condensation. This gradient introduces a tendency of directional movement and enables the microdroplet move out of the valley of papillae until the microdroplet is suspended on the tops of papillae. This finding is significant to understand the mechanism of self-cleaning.