The dynamic spreading of a liquid droplet on micropillar-arrayed surfaces is experimentally investigated. A theoretical model is proposed to include energy dissipations raised from both the viscous resistance at mesoscale and the molecular friction at microscale in the triple-phase region. The scaling laws and spreading shape of the droplet change with the variation of the liquid viscosity because of the competition between these two mechanisms of energy dissipations at the moving contact line. The Laplace pressures at the interior corner and at the wavy contact line are the answers to the excess driving energy and the superwetting on pillar-arrayed surfaces. The formation and evolution of the bulk and the fringe are also analyzed in detail. Our results may help to understand the wetting dynamics on microtextured surfaces and assist the future design of engineered surfaces in practical applications. (C) 2014 AIP Publishing LLC.

[http://dx.doi.org/10.1063/1.4895497]

This work was jointly supported by the National Natural Science Foundation of China (NSFC, Grant Nos. 11202213 and 11372313), the Key Research Program of the Chinese Academy of Sciences (Grant No. KJZD-EW-M01), and the Instrument Developing Project of the Chinese Academy of Sciences (Grant No. Y2010031).

The article was published as:

Yuan QZ,Huang XF,Zhao YP. Dynamic Spreading On Pillar-arrayed Surfaces: Viscous Resistance Versus Molecular Friction[J].Physics Of Fluids,2014,26(9):92104.