Dynamics of drying colloidal suspensions, measured by optical coherence tomography

Abe, K., Atkinson, P.S., Cheung, C.S., Liang, H. ORCID: 0000-0001-9496-406X, Goehring, L. ORCID: 0000-0002-3858-7295 and Inasawa, S., 2024. Dynamics of drying colloidal suspensions, measured by optical coherence tomography. Soft Matter. ISSN 1744-683X

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Colloidal suspensions are the basis of a wide variety of coatings, prepared as liquids and then dried into solid films. The processes at play during film formation, however, are difficult to observe directly. Here, we demonstrate that optical coherence tomography (OCT) can provide fast, non-contact, precise profiling of the dynamics within a drying suspension. Using a scanning Michelson interferometer with a broadband laser source, OCT creates cross-sectional images of the optical stratigraphy of a sample. With this method, we observed the drying of colloidal silica in Hele–Shaw cells with 10 μm transverse and 1.8 μm depth resolution, over a 1 cm scan line and a 15 s sampling period. The resulting images were calibrated to show how the concentration of colloidal particles varied with position and drying time. This gives access to important transport properties, for example, of how collective diffusion depends on particle concentration. Looking at early-time behaviours, we also show how a drying front initially develops, and how the induction time before the appearance of a solid film depends on the balance of diffusion and evaporation-driven motion. Pairing these results with optical microscopy and particle tracking techniques, we find that film formation can be significantly delayed by any density-driven circulation occurring near the drying front.

Item Type: Journal article
Publication Title: Soft Matter
Creators: Abe, K., Atkinson, P.S., Cheung, C.S., Liang, H., Goehring, L. and Inasawa, S.
Publisher: Royal Society of Chemistry
Date: 13 February 2024
ISSN: 1744-683X
Rights: This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
Divisions: Schools > School of Science and Technology
Record created by: Jonathan Gallacher
Date Added: 04 Mar 2024 10:12
Last Modified: 04 Mar 2024 10:12
URI: https://irep.ntu.ac.uk/id/eprint/51001

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