Droplet impact on superhydrophobic surfaces fully decorated with cylindrical macrotextures

Hypothesis: Impacting on a superhydrophobic surface, water droplet spreads to a pancake shape and then retracts and bounces off. Although the collision time is mostly in the order of couple of 10 ms for milli-metric droplets, researchers have shown recently that decorating the superhydrophobic surface with a single macrotexture or intersecting ridge reduces this contact time if the droplet hits the texture or the intersection exactly in the center. Hence, covering the surface with ridges should address this hitting point restriction. Experiments: Using an extruder-type 3D printer, we fabricated a superhydrophobic surface fully decorated with cylindrical ridges. The dynamic of water droplet impact on this surface at different impact velocities has been studied for varied droplet volumes and ridge sizes. Findings: Our data show that regardless of the location of the contact point, when the kinetic energy of the drop is sufficient to completely wet the ridges, the contact time reduces similar to 13% as the consequence of similar to 20% faster retraction. For higher impact velocity, the contact becomes shorter since the flattened drop splashes from the periphery. Moreover, the simplified, time-efficient and inexpensive method of fabricating the surfaces presented in this paper can be implemented in fabricating many versatile superhydrophobic surfaces with complex geometries. (C) 2017 Elsevier Inc. All rights reserved.