Physico-Chimie Curie, Institut Curie, UMR 168, UPMC, Paris, France.
Langmuir. 2011 Aug 16;27(16):9955-60. doi: 10.1021/la201664v. Epub 2011 Jul 20.
We report on the role of a surfactant monolayer in the impact of small spheres on an air-water interface. We observe that an air cavity (splashing) is induced above a threshold impact velocity. We explore the dependence of this threshold velocity on the bath surface tension and on the bath viscosity using water-ethanol and water-glycerol mixtures, respectively. Interestingly, the threshold velocity for air entrainment is reduced by the presence of a stearic acid monolayer because the hydrophobic tails favor the forced entry of air during the sphere's impact. More generally, we show that this threshold velocity is determined by the wettability of the sphere by the bath, which can equivalently be controlled by tuning the bath properties (presence of a monolayer) or the sphere surface properties (via a surface treatment). These results provide insight into recently developed vesicle production techniques based on the impact of drops or jets on a lipid layer.
我们研究了单分子层表面活性剂在微小球体撞击气液界面过程中的作用。我们发现，当撞击速度超过某个阈值时，气腔（即喷溅）会在球体上方形成。我们分别采用水-乙醇和水-甘油混合溶液，研究了这个阈值速度与浴液表面张力和黏度的依赖关系。有趣的是，由于疏水性尾链有利于在球体撞击过程中强制进入空气，因此存在硬脂酸单分子层时，空气夹带的阈值速度会降低。更一般地说，我们表明，这个阈值速度取决于球体对浴液的润湿性，而浴液的润湿性可以通过调节浴液的性质（存在单分子层）或球体表面的性质（通过表面处理）来等效控制。这些结果为基于液滴或射流撞击脂质层的囊泡生产技术提供了新的见解。
