Spreading of a water droplet on a vertically aligned Si nanorod array surface.

The dynamics of spreading of a water drop on a vertically aligned Si nanorod array surface is studied with a fast charge coupled device camera. Four dynamic spreading regimes are identified, with a precursor rim advancing ahead of the contact line. The diameters of the precursor rim Dp, the precursor length δ, and the contact line Dc obey dynamic scaling laws, Dc,p∝tnc,p/2, with nc≈0.216 and np≈0.272, and δ≈t1/2. The exponents do not vary significantly with the nanorod height and are consistent with the dynamic spreading behavior on a rough or porous surface. [ABSTRACT FROM AUTHOR]