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 per s and 5 μm per 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) ≃ 5–12D₀ are significantly larger than the simple estimate D₀ given by the Stokes–Einstein relation, thus highlighting the important role played by the colloidal interactions in such dispersions.

中文翻译：

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带电胶体分散液的集体扩散系数：干滴中的干涉测量。

在目前的工作中，我们使用Mach-Zehnder干涉术来彻底研究带电胶体分散液的二维约束液滴的干燥动力学。该技术使得可以在液滴干燥期间以高精度（约0.5％）和高时间和空间分辨率（每秒钟约1帧，每像素5μm）测量胶体浓度场。这些功能使我们能够在这种不平衡的情况下探测带电分散体的质量传输。特别地，我们的实验提供了证据，对于浮力驱动的对流可以忽略不计的某些范围的参数，可以通过纯扩散过程描述液滴内的传质。然后，我们可以从这些实验中提取出色散D的集体扩散系数（φ）在很宽的浓度范围φ = 0.24-0.5，即从液体分散状态的固体玻璃制度，具有极高的精度。D（φ）12 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发挥的重要作用。