Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States.
Langmuir. 2012 Mar 20;28(11):4984-8. doi: 10.1021/la204928m. Epub 2012 Mar 8.
The influence of the small ionic surfactant sodium dodecyl sulfate (SDS) on the evaporation of drying colloidal droplets is quantitatively investigated. The addition of SDS leads to a significantly more uniform deposition of colloidal particles after evaporation (i.e., the so-called "coffee-ring effect" is dramatically altered). We understand this phenomenon in the context of circulating radial Marangoni flows induced by the variation of SDS concentration along the air-water interface. Video microscopy permits the direct visualization of the colloidal particles involved in these flows, revealing a surprisingly stable "Marangoni eddy" that prevents particle deposition at the drop perimeter.
定量研究了小离子表面活性剂十二烷基硫酸钠（SDS）对干燥胶体液滴蒸发的影响。添加 SDS 后，蒸发后胶体颗粒的沉积更加均匀（即所谓的“咖啡环效应”显著改变）。我们在 SDS 浓度沿气-液界面变化引起的循环径向马兰戈尼流的背景下理解这一现象。视频显微镜允许直接观察这些流中涉及的胶体颗粒，揭示了一种令人惊讶的稳定的“马兰戈尼涡”，防止颗粒在液滴周边沉积。
