Weierstrass Institute for Applied Analysis and Stochastics, 10117 Berlin, Germany;
Experimental Physics and Center for Biophysics, Saarland University, 66041 Saarbrücken, Germany.
Proc Natl Acad Sci U S A. 2019 May 7;116(19):9275-9284. doi: 10.1073/pnas.1820487116. Epub 2019 Apr 19.
Thin polymer films on hydrophobic substrates are susceptible to rupture and hole formation. This, in turn, initiates a complex dewetting process, which ultimately leads to characteristic droplet patterns. Experimental and theoretical studies suggest that the type of droplet pattern depends on the specific interfacial condition between the polymer and the substrate. Predicting the morphological evolution over long timescales and on the different length scales involved is a major computational challenge. In this study, a highly adaptive numerical scheme is presented, which allows for following the dewetting process deep into the nonlinear regime of the model equations and captures the complex dynamics, including the shedding of droplets. In addition, our numerical results predict the previously unknown shedding of satellite droplets during the destabilization of liquid ridges that form during the late stages of the dewetting process. While the formation of satellite droplets is well known in the context of elongating fluid filaments and jets, we show here that, for dewetting liquid ridges, this property can be dramatically altered by the interfacial condition between polymer and substrate, namely slip. This work shows how dissipative processes can be used to systematically tune the formation of patterns.
疏水基底上的薄聚合物膜容易破裂和形成孔。这反过来又引发了一个复杂的去湿过程，最终导致了具有特征性的液滴图案。实验和理论研究表明，液滴图案的类型取决于聚合物和基底之间的特定界面条件。预测长时间尺度和涉及的不同长度尺度上的形态演变是一个主要的计算挑战。在这项研究中，提出了一种高度自适应的数值方案，该方案允许深入研究模型方程的非线性区域，并捕捉到复杂的动力学，包括液滴的脱落。此外，我们的数值结果预测了在去湿过程后期形成的液流脊失稳过程中先前未知的卫星液滴的脱落。虽然卫星液滴的形成在延长的流体细丝和射流的背景下是众所周知的，但我们在这里表明，对于去湿的液流脊，这种性质可以通过聚合物和基底之间的界面条件（即滑移）显著改变。这项工作展示了耗散过程如何用于系统地调整图案的形成。
