The Anti-Lotus Leaf Effect in Nanohydrodynamic Bump Arrays

In this paper, we address the hydraulic flow of fluids on and within nanofabricated hydrophilic (as opposed to hydrophobic) surfaces, and the influence of an extended precursor film on the wetting dynamics of water penetrating a nano-textured array of posts that has no sealing surface (open-top). The width of the precursor film in front of the wetting edge delta is extraordinarily large, approximately 2 mm for our device, and it drives the wetting penetration film in the open- top array. We discuss the way this thin precursor film controls the movement of the macroscopic wetting front L-w and its dynamics in the nanofabricated array of posts. Rapid and controllable transport of nanoparticles in such an open top array of posts, as controlled by the precursor film, is demonstrated using a bump array textured morphology.