We developed a procedure to measure diffusion coefficients using microfluidic devices that contributes to the transport analysis of high molecular weight solutes with low diffusion coefficient. This procedure allows a quick determination of diffusion coefficients and a precise evaluation of measurement errors. Making use of color variation of a pH indicator, we determined its diffusion coefficient in its own solvent (water). The value obtained was compared with previously published ones and was found to be similar to those cited. The microfluidic device has a serpentine-shaped channel that allows monitoring the solution evolution in different regions of the path in a single visual field without the need to move the camera or the microchip. This kind of device also allows the spatial and temporal tracking of the diffusion process. The solution color intensity is used to determine solute concentration; therefore, this method presents an advantage compared to those based on fluorescence detection. A complete analysis of the diffusive behavior along the channel path was performed in order to test the accuracy of these kinds of methodologies. This analysis can be used with similar devices, and the techniques employed for diffusion analysis can be applied to a µTAS-type microfluidic platform, allowing obtain variations of the diffusion coefficient as a function of time due to variations in external factors, e.g., temperature, etc.

Graphical abstract

中文翻译：

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用于测定可见光谱中可检测到的高分子量溶质的扩散系数的微流控装置分析

我们开发了一种使用微流体装置测量扩散系数的程序，该程序有助于低扩散系数的高分子量溶质的传输分析。该程序可以快速确定扩散系数并精确评估测量误差。利用 pH 指示剂的颜色变化，我们确定了它在其自身溶剂（水）中的扩散系数。将获得的值与以前发表的值进行比较，发现与引用的值相似。微流体装置具有蛇形通道，无需移动相机或微芯片即可在单个视野中监测路径不同区域的溶液演变。这种设备还允许对扩散过程进行空间和时间跟踪。溶液颜色强度用于确定溶质浓度；因此，与基于荧光检测的方法相比，该方法具有优势。对沿通道路径的扩散行为进行了完整分析，以测试这些方法的准确性。这种分析可以与类似的设备一起使用，用于扩散分析的技术可以应用于µ TAS 型微流控平台，由于外部因素（例如温度等）的变化，允许获得扩散系数随时间的变化。

图形概要