Henkel Christopher, Snoeijer Jacco H, Thiele Uwe
Institut für Theoretische Physik, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Str. 9, 48149 Münster, Germany.
Physics of Fluids Group and J. M. Burgers Centre for Fluid Dynamics, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands.
Soft Matter. 2021 Nov 24;17(45):10359-10375. doi: 10.1039/d1sm01032h.
The wetting of soft elastic substrates exhibits many features that have no counterpart on rigid surfaces. Modelling the detailed elastocapillary interactions is challenging, and has so far been limited to single contact lines or single drops. Here we propose a reduced long-wave model that captures the main qualitative features of statics and dynamics of soft wetting, but which can be applied to ensembles of droplets. The model has the form of a gradient dynamics on an underlying free energy that reflects capillarity, wettability and compressional elasticity. With the model we first recover the double transition in the equilibrium contact angles that occurs when increasing substrate softness from ideally rigid towards very soft (, liquid). Second, the spreading of single drops of partially and completely wetting liquids is considered showing that known dependencies of the dynamic contact angle on contact line velocity are well reproduced. Finally, we go beyond the single droplet picture and consider the coarsening for a two-drop system as well as for a large ensemble of drops. It is shown that the dominant coarsening mode changes with substrate softness in a nontrivial way.
软弹性基底的润湿表现出许多在刚性表面上不存在的特征。对详细的弹性毛细相互作用进行建模具有挑战性，并且迄今为止仅限于单个接触线或单个液滴。在这里，我们提出了一个简化的长波模型，该模型捕捉了软润湿静态和动态的主要定性特征，但可以应用于液滴集合。该模型具有基于反映毛细作用、润湿性和压缩弹性的自由能的梯度动力学形式。利用该模型，我们首先恢复了在将基底柔软度从理想刚性增加到非常柔软（，液体）时平衡接触角的双转变。其次，考虑了部分和完全润湿液体的单个液滴的铺展，结果表明动态接触角对接触线速度的已知依赖性得到了很好的再现。最后，我们超越了单个液滴的情况，考虑了双液滴系统以及大量液滴集合的粗化。结果表明，主导的粗化模式以一种非平凡的方式随基底柔软度而变化。
