Improving superamphiphobicity by mimicking tree-branch topography

when a droplet impacts on a superhydrophobic structured surface below a certain impact velocity, the droplet can bounce off completely from the surface. However, above such velocity a fraction of the droplet will pin on the surface. Surfaces capable of repelling water droplets are ubiquitous in nature or have been artificially fabricated. However, as the surface tension of the liquid is reduced, the capability of the surface to remain non-wetting gets hindered. Despite progress in previous research, the understanding and development of superamphiphobic surface to impacting low surface tension droplets remains elusive. It is proposed that multi-layer re-entrant like roughness can further enhance the anti- wetting properties also for low surface tension fluids. In this work, we produce patterned conical micro-structures with lateral nano-sized roughness. Furthermore, the droplet impact experiments are conducted on various surfaces with variable surface tensions (27 mN/m - 72 mN/m) by using droplets with different Weber numbers (2-170). We show that conical microstructures with lateral roughness mimicking tree-branches provides a surface topology capable of absorbing the force exerted by the droplet during the impact which prevents the droplet from pinning on the surface at higher impact velocity even for low surface tension droplets. Our study has significance for understanding the liquid interaction mechanism with the surface during the impact process and for the associated surface design considerations. (C) 2021 The Authors. Published by Elsevier Inc.

Automated summary

This study investigates the phenomenon of droplet impact on superhydrophobic structured surfaces, where droplets can either bounce off or pin on the surface depending on the impact velocity. The researchers propose that multi-layer re-entrant like roughness can enhance the anti-wetting properties of the surface, even for low surface tension droplets. Experimental results demonstrate that conical microstructures with lateral roughness mimicking tree-branches prevent droplets from pinning on the surface at higher impact velocities. This study contributes to the understanding of liquid interaction mechanisms during the impact process and provides insights for surface design considerations.