For years, our group has been developing innovative experimental methodologies [1] to monitor liquid transfer in porous media and complex fluids using dynamic NMR relaxometry. Combined with MRI, this non-invasive, multiscale, and time-resolved approach enables the individual tracking of all out-of-equilibrium protonic liquid phases during processes such as drying, imbibition, or internal water redistribution in model nanoporous media, for various applications involving geo-based (clay, granular systems) or bio-based materials (wood, paper, plant fibers [2]) and gels [3]. Here, we show how in this context, original quantitative information can be extracted from the detailed analysis of the evolution of the transverse NMR relaxation time distributions over time during such transfers based on fast exchange concept between bulk and surface water at the pore scale. Dynamic NMR relaxometry is able to reveal phenomena such as wetting and dewetting, chemical instabilities of the solid matrix, or the progressive loss of moisture homogeneity inside non-transparent materials — information that is highly valuable for improving predictive physical models of liquid transport for a large range of scale corresponding to all liquid states. Several examples of porous material and complex fluid will be presented to illustrate the versatility and robustness of this approach.

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 [1] Maillet, B.; Sidi-Boulenouar, R.; Coussot, P. Dynamic NMR Relaxometry as a Simple Tool for Measuring Liquid Transfers and Characterizing Surface and Structure Evolution in Porous Media. Langmuir 2022, 38, 15009–15025.

[2] L. Yan, Y. Zou, J. Gil-Roca, B. Maillet, B. St-Michel, P. Coussot, Fate of a water drop in a cellulosic material, Phys. Rev. Appl., 23 (1) (2025), Article 014073, 10.1103/PhysRevApplied.23.014073

[3] E. Julien, B. Maillet, L. Tocquer, S. Aime, P. Coussot, Dynamic NMR relaxometry as a straightforward measurement of concentration variations in colloidal gels, Langmuir, 40 (51) (2024), https://pubs.acs.org/doi/10.1021/acs.langmuir.4c03404