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Microfluidic in-line dynamic light scattering with a commercial fibre optic system
Luis M G Torquato1, Nelson Hélaine2, Yufan Cui1
1Department of Chemical Engineering, Imperial College London, London SW7 2AZ, UK. j.cabral@imperial.ac.uk.
Lab on a Chip
|May 15, 2023
Summary
This study introduces a novel fiber-optic dynamic light scattering (DLS) system integrated with microfluidics for fluid characterization. The contact-free approach enables real-time analysis of solutions and dispersions under flow conditions.
Area of Science:
- Fluid dynamics
- Materials science
- Analytical chemistry
Background:
- Characterizing fluid properties like micellar size and polymer dynamics is crucial in various scientific fields.
- Traditional methods often require bulk samples and lack real-time, in-situ analysis capabilities.
- Microfluidic systems offer precise control over fluid environments but integrating advanced characterization techniques remains challenging.
Purpose of the Study:
- To develop and validate a contact-free, fiber-optic dynamic light scattering (DLS) system for microfluidic applications.
- To enable in-situ characterization of solutions, dispersions, and structured fluids under varying flow conditions.
- To establish a systematic method for analyzing flow-DLS data and understanding the interplay between Brownian motion and convection.
Main Methods:
- Coupling dynamic light scattering (DLS) with microfluidics using a contact-free fiber-optic probe.
- Utilizing model systems including micellar solutions, polymer solutions, and colloidal dispersions (1-100 nm radii) for validation.
- Investigating flow-DLS analysis across a range of flow velocities (0-16 cm s⁻¹) and different microfluidic setups (capillary and direct microdevice measurement).
Main Results:
- The fiber-optic DLS system successfully characterized various solutions and dispersions in microfluidic channels.
- A systematic analysis identified distinct regions of flow-DLS behavior, from quiescent approximations to convection-dominated regimes.
- Demonstrated continuous flow measurement of a binary surfactant/salt solution, showing composition-dependent micellar size changes within minutes.
Conclusions:
- The developed flow-DLS system provides a robust and efficient method for in-situ characterization of fluids in microfluidics.
- The contact-free approach simplifies experimental setups and overcomes challenges in optical alignment.
- This technique enables rapid, statistically sound analysis of dynamic fluid properties, with applications in materials science and chemical analysis.
