Issue 11, 2023

Microfluidic in-line dynamic light scattering with a commercial fibre optic system

Abstract

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−1), 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.

Graphical abstract: Microfluidic in-line dynamic light scattering with a commercial fibre optic system

Supplementary files

Article information

Article type
Paper
Submitted
19 Jan 2023
Accepted
14 Apr 2023
First published
18 Apr 2023
This article is Open Access
Creative Commons BY license

Lab Chip, 2023,23, 2540-2552

Microfluidic in-line dynamic light scattering with a commercial fibre optic system

L. M. G. Torquato, N. Hélaine, Y. Cui, R. O'Connell, J. Gummel, E. S. J. Robles, D. Jacob and J. T. Cabral, Lab Chip, 2023, 23, 2540 DOI: 10.1039/D3LC00062A

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