PASTEUR, Department of Chemistry, Ecole Normale Supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France.
PASTEUR, Department of Chemistry, Ecole Normale Supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France.
J Colloid Interface Sci. 2020 Aug 1;573:370-375. doi: 10.1016/j.jcis.2020.03.094. Epub 2020 Mar 27.
The so-called coffee-ring effect (CRE) is extraordinarily common, problematic in industry and attractively puzzling for researchers, with the accepted rule that it requires two key-ingredients: solvent evaporation and contact line pinning. Here, we demonstrate that the CRE also occurs when the solvent of a pinned sessile drop transfers into another liquid, without involving any evaporation. We show that it shares all characteristic features of the evaporative CRE: solvent transfer-driven transport of solutes to the contact line, ring-shaped deposit, closely-packed particle organization at the contact line, and size-dependent particle sorting. We thus suggest expanding the definition of the coffee-ring effect to any pinned drop having its solvent transferring to an outer medium where the drop compounds cannot be dissolved.
所谓的咖啡环效应（CRE）非常常见，在工业上存在问题，同时也吸引了研究人员的兴趣，人们普遍认为它需要两个关键因素：溶剂蒸发和接触线钉扎。在这里，我们证明了当被钉住的不流动液滴中的溶剂转移到另一种液体中时，即使没有涉及任何蒸发，CRE 也会发生。我们表明，它具有蒸发 CRE 的所有特征：溶剂传输驱动溶质向接触线的运输、环状沉积物、接触线处紧密排列的颗粒组织以及尺寸相关的颗粒分类。因此，我们建议将咖啡环效应的定义扩展到任何其溶剂转移到化合物无法溶解的外部介质中的被钉住的液滴。
