# Studying Diffusiophoresis-Driven Colloid Transport in Porous Media Using Microfluidics

Pauline Etienne, Cyprien Soulaine, Sophie Roman

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Pauline Etienne, Cyprien Soulaine, Sophie Roman. Studying Diffusiophoresis-Driven Colloid Transport in Porous Media Using Microfluidics. JEMP 2025, Nov 2025, Orléans, France. 2025. hal-05380388

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Submitted on 24 Nov 2025

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# Studying Diffusiophoresis-Driven Colloid Transport in Porous Media Using Microfluidics

P. Etienne, C.Soulaine, S. Roman

Institut des Science de la Terre d'Orléans (ISTO), UMR 7327, Université d'Orléans, CNRS, BRGM, OSUC, F-45071 Orléans, France

**Keywords:** diffusiophoresis, porous media, colloid, microfluidics

The remediation of contaminated soils and groundwater is a major challenge. A promising approach exploits colloids movement under the effect of solute concentration gradient generated in situ [1]. This phenomenon, called diffusiophoresis, offers considerable potential to direct colloids toward areas of the porous microstructure that would otherwise be inaccessible (e.g. dead-end pores). However, diffusiophoretic transport in geological porous media has received very little attention to date, particularly in standard transport models, where this phenomenon is often overlooked. In most cases, studies are carried out on simple geometries, while the few investigations on complex geometries are mainly based on theoretical modeling [2].

The objective of this study is to better understand the diffusiophoretic transport of colloids in complex porous media, using microfluidic devices designed to replicate the geometries of natural environments. These devices allow direct observation of colloid displacement and the analysis of transport mechanisms at the pore scale. Experiments are conducted with and without concentration gradients to compare migration dynamics. The impact of local conditions on colloid behavior—such as the structure of the porous medium or the presence of dissolved chemical compounds—is also assessed. The tracking of colloids is ensured through high-resolution imaging techniques combined with advanced image processing algorithms to quantify the dynamics of movement and migration. The expected results should reveal significant differences in the behavior of colloids transport in the presence of concentration gradients in porous media [2]. This effect will be quantified both at the pore scale and by examining particle transport on a global scale. These results contribute to the design of new methods for groundwater remediation by enabling more precise control over colloid transport toward specific contaminated areas.

## References

[1] B. V. Derjaguin, G. Sidorenkov, E. Zubashchenko, et E. Kiseleva, « Kinetic Phenomena in the boundary layers of liquids 1. the capillary osmosis », *Prog. Surf. Sci.*, vol. 43, n° 1, p. 138-152, 1947, doi: 10.1016/0079-6816(93)90023-O.

[2] M. Jotkar, P. de Anna, M. Dentz, et L. Cueto-Felgueroso, « The impact of diffusiophoresis on hydrodynamic dispersion and filtration in porous media », *J. Fluid Mech.*, vol. 991, p. A8, juill. 2024, doi: 10.1017/jfm.2024.546.
# STUDYING DIFFUSIOPHORESIS-DRIVEN COLLOID TRANSPORT IN POROUS MEDIA USING MICROFLUIDICS

Pauline Etienne (pauline.etienne@univ-orleans.fr), Cyprien Soulaine, Sophie Roman
Institut des Sciences de la Terre d'Orléans (ISTO), UMR 7327, Université d'Orléans, CNRS, BRGM, Orléans, France

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## 1) Introduction

* Soil and subsurface pollution threatens groundwater quality, and conventional remediation methods struggle to reach isolated zones within porous media.

* Can we use **diffusiophoresis**, the directed motion of colloids induced by solute concentration gradients, to reach isolated zones in porous media for remediation?

* **Objective:** Investigate particle mobility under controlled solute gradients using microfluidic devices, addressing the current lack of experimental data¹.

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Field-scale and pore-scale representation of in situ remediation using colloids
¹M. Alipour, Y. Li, H. Liu, A. A. Pahlavan, « Diffusiophoretic transport of colloids in porous media », arXiv (preprint), 2024

## 2) Microfluidic setup

<figure><img src="image_8.png" /><figcaption>Experimental setup at ISTO Nanoulab</figcaption></figure>

* A PDMS micromodel with three inlets/outlets and **10 REV** is used to reproduce a porous medium.

* A **NaCl-blue dye solution** is injected to establish a concentration gradient, while **colloids** are introduced through the central inlet.

* A constant flow rate is maintained for 1 hour, then stopped to analyze particle distribution and behavior.

## 3) Diffusiophoresis in porous media

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* New experimental setup enabling stable, well-defined solute gradients for diffusiophoretic transport studies.

* These results align with **diffusiophoretic transport** mechanisms, showing that chemical gradients strongly drive particle migration and accumulation in porous structures.

## 4) Conclusions and perspectives

* The new setup allows controlled investigation of diffusiophoresis in porous media, with clear particle responses confirming expected mechanisms.

* It offers a solid basis to explore different conditions, analyze transport dynamics, and compare with numerical models.

This work was funded by the European Union (ERC, TRACE-it, 101039854).

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