Chaudhury Manoj K, Chaudhury Ankur
Department of Chemical Engineering, Lehigh University, Bethlehem, PA 18015, USA.
Cornell University, Ithaca, NY 14853, USA.
Soft Matter. 2005 Nov 21;1(6):431-435. doi: 10.1039/b512045b.
We studied the spreading of a thin film of hexadecane oil on a hydrophobic polystyrene surface, which is partially covered with tiny water droplets. In spite of the fact that the spreading coefficient of hexadecane is slightly negative on water, the oil actually spreads faster on the droplet covered polystyrene than on the pure substrate. The observed effect is partly due to the geometric factors that lead to greater reduction of oil-substrate interfacial energy in comparison to the increase of oil-vapor surface energy. However, it is more important to consider the reduction of the resistance to fluid motion in the presence of condensed droplets. We provide an explanation of the phenomenon by drawing an analogy to the spreading on a rough surface, in which each water drop nucleates and re-initiates the spreading process. The phenomenon is therefore an approximate 2D version of liquid invasion through porous media.
我们研究了十六烷油薄膜在疏水性聚苯乙烯表面的铺展情况，该表面部分覆盖着微小的水滴。尽管十六烷在水上的铺展系数略为负值，但实际上油在覆盖有水滴的聚苯乙烯上的铺展速度比在纯基底上更快。观察到的这种效应部分归因于几何因素，与油 - 蒸汽表面能的增加相比，这些因素导致油 - 基底界面能有更大程度的降低。然而，更重要的是要考虑在存在凝结水滴的情况下流体运动阻力的降低。我们通过与在粗糙表面上的铺展进行类比来解释这一现象，在粗糙表面上每个水滴都会成核并重新启动铺展过程。因此，该现象是液体通过多孔介质侵入的近似二维版本。
