Liquid Drops Impacting Superamphiphobic Coatings
Liquid Drops Impacting Superamphiphobic Coatings
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DOI：
10.1021/la401120j
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发表时间：
2013-06-25
期刊：
影响因子：
3.9
通讯作者：
Butt, Hans-Juergen
中科院分区：
文献类型：
--
作者：
Deng, Xu;Schellenberger, Frank;Butt, Hans-Juergen
利用高速视频显微镜研究了液滴撞击超双疏涂层的动力学过程。超双疏涂层排斥水和油。该涂层由分形状疏水化二氧化硅网络组成。以乙醇-水和甘油-水混合体系为研究对象，考察了界面张力和粘度对铺展和回缩动力学的影响。液滴扩展主要由惯性决定。在低冲击速度下，液滴完全回弹。然而，接触时间增加的冲击速度，而恢复系数减小。我们认为，下降暂时刺穿超双疏涂层，虽然下降完全反弹。根据对压力的估计，可以得出结论，刺穿主要是由去钉扎而不是下垂。随着速度的增加，液滴部分地钉扎，并且越来越多的液体保留在涂层上。的收缩动力学的时间分辨的研究揭示了两个分离的阶段：一个快速的惯性为主的阶段，其次是缓慢减少的接触直径的下降。当缩回的液滴的直径与撞击前的液滴直径匹配时，发生交叉。我们认为，穿刺的深度增加与冲击速度，穿刺被限制在初始的影响区的下降。如果液滴部分地钉在涂层上，则刺穿的深度超过深度，从而防止整个液滴在回缩阶段期间被移除。
The dynamics of liquid drops impacting superamphiphobic coatings is studied by high-speed video microscopy. Superamphiphobic coatings repel water and oils. The coating consists of a fractal-like hydrophobized silica network. Mixtures of ethanol water and glycerin water are chosen to investigate the influence of interfacial tension and viscosity on spreading and retraction dynamics. Drop spreading is dominated by inertia. At low impact velocity, the drops completely rebound. However, the contact time increases with impact velocity, whereas the restitution coefficient decreases. We suggest that the drop temporarily impales the superamphiphobic coating, although the drop completely rebounds. From an estimate of the pressure, it can be concluded that impalement is dominated by depinning rather than sagging. With increasing velocity, the drops partially pin, and an increasing amount of liquid remains on the coating. A time-resolved study of the retraction dynamics reveals two well-separated phases: a fast inertia-dominated phase followed by a slow decrease of the contact diameter of the drop. The crossover occurs when the diameter of the retracting drop matches the diameter of the drop before impact. We suggest that the depth of impalement increases with impact velocity, where impalement is confined to the initial impact zone of the drop. If the drop partially pins on the coating, the depth of impalement exceeds a depth, preventing the whole drop from being removed during the retraction phase.