Dynamic behaviours of water droplet impacting antiwetting plant leaves

Abstract

Natural minute structures have been analyzed on numerous kind of surfaces like rose leaves, which are helpful for the development of biomimetic materials for self cleaning, fluidic drag reduction, bio-surface, anti-biofouling and prevention of water corrosion. We examined the micro scale structure on the leaves of Leucophyllumfrutescens (Purple sage), Lactuca virosa (Wild lettuce), Montbretia (Crocosmia) and Corymbia (Eucalyptus). Water droplet impact velocity V of 2m/s and 4m/s from the fixed distance shows rebound, oscillations and fragmentation. These are due to uneven distribution of small micro dots, three dimension waxes and tiny horizontal lines on the surfaces. At comparatively low impact velocity, partial bounce back and oscillations, and fragmentation and splashing were observed as velocity was increased. For characterization of wettability of the surface, Contact angle experiments have been performed and Cassie-Baxter and Wenzel approaches are discussed. Highest static contact angle (118.02±7.46) was observed on Leucophyllumfrutescens (Purple sage) surface due to densely covered with three dimensional waxes. However, lowest static contact angle (98.38±4.91) was observed on Eucalyptus (Corymbia) surface with small dots on the surface.