Department of Chemical Engineering, Imperial College London, London SW7 2AZ, UK.
CNRS UMR 5623, Laboratoire des IMRCP, Universite Paul Sabatier, Toulouse, France.
Lab Chip. 2023 May 30;23(11):2540-2552. doi: 10.1039/d3lc00062a.
We report the coupling of dynamic light scattering (DLS) in microfluidics, using a contact-free fibre-optic system, enabling the under-flow characterisation of a range of solutions, dispersions, and structured fluids. The system is evaluated and validated with model systems, specifically micellar and (dilute) polymer solutions, and colloidal dispersions of different radii (∼1-100 nm). A systematic method of flow-DLS analysis is examined as a function of flow velocity (0-16 cm s), and considerations of the relative contribution of 'transit' and 'Brownian' terms enable the identification of regions where (i) a quiescent approximation suffices, (ii) the flow-DLS framework holds, as well as (iii) where deviations are found, until eventually (iv) the convection dominates. We investigate practically relevant, robust setups, namely that of a capillary connected to microdevice, as well as direct measurement on a glass microdevice, examining the role of capillary dimensions and challenges of optical alignment. We conclude with a demonstration of a continuous flow measurement of a binary surfactant/salt solution, whose micellar dimensions vary with composition, characterised with hundreds of data points (every ∼5 s) and adequate statistics, within a few minutes.
我们报告了在微流控中使用无接触光纤系统进行动态光散射（DLS）的耦合，从而能够对各种溶液、分散体和结构化流体进行下向流特性分析。该系统使用模型系统进行了评估和验证，特别是胶束和（稀）聚合物溶液以及不同半径（∼1-100nm）的胶体分散体。作为流速（0-16cm/s）的函数，我们检查了一种系统的流动-DLS 分析方法，并考虑了“迁移”和“布朗”项的相对贡献，从而可以确定（i）静止近似足够、（ii）流动-DLS 框架成立以及（iii）出现偏差的区域，直到最终（iv）对流占主导地位。我们研究了实际相关的、稳健的设置，即与微器件相连的毛细管，以及在玻璃微器件上的直接测量，考察了毛细管尺寸的作用和光学对准的挑战。最后，我们展示了一种二元表面活性剂/盐溶液的连续流动测量，其胶束尺寸随组成而变化，在几分钟内用数百个数据点（每约 5s 一个）和足够的统计数据进行了表征。
