Crivoi A, Zhong X, Duan Fei
School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798.
Phys Rev E Stat Nonlin Soft Matter Phys. 2015 Sep;92(3):032302. doi: 10.1103/PhysRevE.92.032302. Epub 2015 Sep 4.
The coffee-ring effect for particle deposition near the three-phase line after drying a pinned sessile colloidal droplet has been suppressed or attenuated in many recent studies. However, there have been few attempts to simulate the mitigation of the effect in the presence of strong particle-particle attraction forces. We develop a three-dimensional stochastic model to investigate the drying process of a pinned colloidal sessile droplet by considering the sticking between particles, which was observed in the experiments. The Monte Carlo simulation results show that by solely promoting the particle-particle attraction in the model, the final deposit shape is transformed from the coffee ring to the uniform film deposition. This phenomenon is modeled using the colloidal aggregation technique and explained by the "Tetris principle," meaning that unevenly shaped or branched particle clusters rapidly build up a sparse structure spanning throughout the entire domain in the drying process. The influence of the controlled parameters is analyzed as well. The simulation is reflected by the drying patterns of the nanofluid droplets through the surfactant control in the experiments.
在许多近期研究中，干燥固定的固着胶体液滴后，三相线附近颗粒沉积的咖啡环效应已得到抑制或减弱。然而，在存在强颗粒间吸引力的情况下，很少有人尝试模拟这种效应的减轻情况。我们开发了一个三维随机模型，通过考虑实验中观察到的颗粒间黏附现象，来研究固定的胶体固着液滴的干燥过程。蒙特卡罗模拟结果表明，仅通过在模型中增强颗粒间吸引力，最终沉积物形状就会从咖啡环转变为均匀的薄膜沉积。这种现象使用胶体聚集技术进行建模，并通过“俄罗斯方块原理”进行解释，即形状不均匀或分支的颗粒团簇在干燥过程中迅速形成跨越整个区域的稀疏结构。同时也分析了控制参数的影响。实验中通过表面活性剂控制，纳米流体液滴的干燥模式反映了该模拟结果。
