Capillary flow as the cause of ring stains from dried liquid drops
Capillary flow as the cause of ring stains from dried liquid drops
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DOI：
10.1038/39827
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发表时间：
1997-10-23
期刊：
影响因子：
64.8
通讯作者：
Witten, TA
中科院分区：
文献类型：
--
作者：
Deegan, RD;Bakajin, O;Witten, TA
当一滴洒出的咖啡在固体表面上变干时，它会沿着周围沿着致密的环状存款（图1a）。咖啡最初分散在整滴咖啡中，后来浓缩成一小部分。这种环状沉积物在含有分散固体的咖啡滴蒸发到表面上时很常见，它们影响印刷、洗涤和涂层等过程（1-5）。环形沉积物还提供了在表面上写入或存款精细图案的潜在手段。在这里，我们将沉积的特征图案归因于毛细流动的形式，其中干燥液滴的接触线的钉扎确保从边缘蒸发的液体由来自内部的液体补充，所产生的向外流动可以将几乎所有分散的材料带到边缘。这种机制预测了一个独特的幂律增长的环质量随时间的法律独立于特定的基板，载液或沉积的固体。我们已经通过对胶体流体的显微观察证实了这一定律。
When a spilled drop of coffee dries on a solid surface, it leaves a dense, ring-like deposit along the perimeter (Fig. 1a). The coffee-initially dispersed over the entire drop-becomes concentrated into a tiny fraction of it. Such ring deposits are common wherever drops containing dispersed solids evaporate on a surface, and they influence processes such as printing, washing and coating(1-5). Ring deposits also provide a potential means to write or deposit a fine pattern onto a surface. Here we ascribe the characteristic pattern of the deposition to a form of capillary flow in which pinning of the contact line of the drying drop ensures that liquid evaporating from the edge is replenished by liquid from the interior, The resulting outward flow can carry virtually all the dispersed material to the edge. This mechanism predicts a distinctive power-law growth of the ring mass with time-a law independent of the particular substrate, carrier fluid or deposited solids. We have verified this law by microscopic observations of colloidal fluids.