Drop impact on superhydrophobic surface with protrusions

The phenomenon of drop impact is of significant importance to many engineering applications. In this work, water drops impact on superhydrophobic surfaces with or without protrusions were experimentally investigated under relatively low We numbers, using a high-speed camera. The focus was given to the spreading, bouncing and breakup behaviors on three different protrusions (semicircle, equilateral triangle and square). Our results show that the presence of protrusions not only alters the impact dynamics but also drastically affect the drop deformation. It was found that water drops persist the memory of the protrusions' geometry during the rebounding process and the hierarchical structure of protrusion surfaces leads drops to bounce off and break up more easily. A dimensionless analysis reveals that the protrusion with different geometries distinctly enhances the expanding process and reduces the contact time compared to the planar surface. (C) 2019 Elsevier Ltd. All rights reserved.