Drops can bounce from perfectly hydrophilic surfaces
Drops can bounce from perfectly hydrophilic surfaces
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DOI：
10.1209/0295-5075/108/24001
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发表时间：
2014-10-01
期刊：
影响因子：
1.8
通讯作者：
Rubinstein, S. M.
中科院分区：
文献类型：
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作者：
Kolinski, J. M.;Mahadevan, L.;Rubinstein, S. M.
众所周知，液滴会从超疏水表面和液体表面反弹。在这里，我们表明液滴也可以从超亲水固体表面（例如原子级光滑的云母片）反弹。然而，与该过程相关的恢复系数C-R显著低于与从超疏水表面回弹相关的恢复系数C-R。直接成像方法使我们能够表征在进入表面附近的液滴的变形的动力学。我们发现，液滴反弹发生时，没有液滴接触固体，有一个纳米级的空气膜分离的液体和固体，这表明空气膜中的剪切是反弹过程中耗散的主要来源。此外，我们看到，在其他亲水表面（如处理过的玻璃）上的任何离散的纳米高度缺陷完全抑制了液滴的反弹，导致液体润湿表面。我们的研究为液滴冲击动力学增加了一个新的方面，强调空气薄膜不仅可以在飞溅的背景下发挥作用，还可以在弹跳中发挥作用，同时突出了罕见的表面缺陷在抑制这种反应中的作用。版权所有（C）2014 EPLA
Drops are well known to rebound from superhydrophobic surfaces and from liquid surfaces. Here, we show that drops can also rebound from a superhydrophilic solid surface such as an atomically smooth mica sheet. However, the coefficient of restitution C-R associated with this process is significantly lower than that associated with rebound from superhydrophobic surfaces. A direct imaging method allows us to characterize the dynamics of the deformation of the drop in entering the vicinity of the surface. We find that drop bouncing occurs without the drop ever touching the solid and there is a nanometer-scale film of air that separates the liquid and solid, suggesting that shear in the air film is the dominant source of dissipation during rebound. Furthermore, we see that any discrete nanometer-height defects on an otherwise hydrophilic surface, such as treated glass, completely inhibits the bouncing of the drop, causing the liquid to wet the surface. Our study adds a new facet to the dynamics of droplet impact by emphasizing that the thin film of air can play a role not just in the context of splashing but also bouncing, while highlighting the role of rare surface defects in inhibiting this response. Copyright (C) EPLA, 2014