论文标题
带电的胶体分散体的集体扩散系数：干涉测量在干燥液中
Collective diffusion coefficient of a charged colloidal dispersion: interferometric measurements in a drying drop
论文作者
论文摘要
在目前的工作中，我们使用Mach-Zehnder干涉法来彻底研究带电胶体分散液的2D约束滴的干燥动力学。该技术使得在液滴干燥期间以高精度（约0.5％）的干燥过程中测量胶体浓度场，并且具有高时空和空间分辨率（约1帧/s和5 $μ$ m/pixel）。这些功能使我们能够在这种不平衡情况下探测带电的分散体的大规模运输。特别是，我们的实验提供了一个证据，表明可以通过纯粹的扩散过程来描述液滴中的质量转运，以针对浮力驱动的对流可以忽略不计的某些参数。然后，我们能够从这些实验中提取分散体的集体扩散系数$ d（φ）$在广泛的浓度范围内$φ= 0.24 $ - $ 0.5 $，即，从液体分散状态到实心玻璃制度，具有很高的精度。 $ d（φ）\ simeq 5 $ - $ 12 d_0 $的测量值明显大于Stokes-Einstein关系给出的简单估计$ D_0 $，因此突出了胶体相互作用在此类分散体中所起的重要作用。
In the present work, we use Mach-Zehnder interferometry to thoroughly investigate the drying dynamics of a 2D confined drop of a charged colloidal dispersion. This technique makes it possible to measure the colloid concentration field during the drying of the drop at a high accuracy (about 0.5%) and with a high temporal and spatial resolution (about 1 frame/s and 5 $μ$m/pixel). These features allow us to probe mass transport of the charged dispersion in this out-of-equilibrium situation. In particular, our experiments provide the evidence that mass transport within the drop can be described by a purely diffusive process for some range of parameters for which the buoyancy-driven convection is negligible. We are then able to extract from these experiments the collective diffusion coefficient of the dispersion $D(φ)$ over a wide concentration range $φ=0.24$-$0.5$, i.e. from the liquid dispersed state to the solid glass regime, with a high accuracy. The measured values of $D(φ)\simeq 5$-$12 D_0$ are significantly larger than the simple estimate $D_0$ given by the Stokes-Einstein relation, thus highlighting the important role played by the colloidal interactions in such dispersions.
