Biotemplated hierarchical surfaces and the role of dual length scales on the repellency of impacting droplets

We fabricated biomimetic hierarchical superhydrophobic surfaces using the Tobacco mosaic virus and investigated the role of each length scale during droplet impact by decomposing the micro and nanoscale components. We found that 10 mu l water droplets rebounded at impact velocities greater than 4.3 m/s on the hierarchical surfaces, outperforming the nanostructured surfaces, which underwent an observable wetting transition at an impact velocity of 2.7 m/s. This finding demonstrates that each length scale plays a distinct, but complementary, role in maximizing water repellency during droplet impact and, thus, provides insight into the evolutionary development of highly water-repellant hierarchical plant leaves. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4729935]