Univ Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière, F-69622, LYON, France.
Soft Matter. 2017 May 14;13(18):3341-3351. doi: 10.1039/c7sm00358g. Epub 2017 Apr 19.
Electro-osmosis (EO) is a powerful tool to manipulate liquids in micro and nanofluidic systems. While EO has been studied extensively at liquid-solid interfaces, the case of liquid-vapor interfaces, found e.g. in foam films and bubbles, remains to be explored. Here we perform molecular dynamics (MD) simulations of EO in a film of aqueous electrolyte covered with fluid layers of ionic surfactants and surrounded by gas. Following the experimental procedure, we compute the zeta potential from the EO velocity, defined as the velocity difference between the middle of the liquid film and the surrounding gas. We show that the zeta potential can be smaller or larger than existing predictions depending on the surfactant coverage. We explain the failure of previous descriptions by the fact that surfactants and bound ions move as rigid bodies and do not transmit the electric driving force to the liquid locally. Considering the reciprocal streaming current effect, we then develop an extended model, which can be used to predict the experimental zeta potential of surfactant-laden liquid-gas interfaces.
电渗透（Electro-osmosis，简称 EO）是一种在微纳流控系统中操纵液体的强大工具。尽管在固液界面上已经对电渗透进行了广泛的研究，但在泡沫膜和气泡等液体-气体界面的情况下，这一现象仍有待探索。在这里，我们对水基电解质膜中的电渗透进行了分子动力学（MD）模拟，该膜覆盖有离子型表面活性剂的流体层，并被气体包围。按照实验程序，我们从电渗透速度（定义为液体膜中间和周围气体之间的速度差）计算了 zeta 电势。我们表明，zeta 电势可以小于或大于现有预测值，具体取决于表面活性剂的覆盖度。我们通过以下事实解释了先前描述的失败：表面活性剂和结合离子作为刚体移动，并且不会将电场驱动力局部传递给液体。考虑到反向流动电流效应，我们随后开发了一个扩展模型，该模型可用于预测负载有表面活性剂的液-气界面的实验 zeta 电势。
