InterPore2026

Role of diffusiophoresis in colloidal transport through porous media: Microfluidics experiments

20 May 2026, 11:35

15m

Oral Presentation (MS02) Environmental Porous Media: Water, Agriculture, and Remediation MS02

Speaker

Pauline Etienne (Institut des Science de la Terre d’Orléans)

Description

The remediation of contaminated soils and groundwater is a major challenge. A promising approach exploits colloid movement under the effect of solute concentration gradients generated in situ by the contaminant [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 heterogeneous geometries are mainly based on theoretical modeling [2].
Recent progress in microfluidic experiments on simple geometries makes it possible to identify a wide range of local behaviors, including accumulation at constrictions [3] and penetration into dead-end features [4], [5]. As expected, the presence of a chemical gradient significantly alters colloid behavior by enhancing mobility, modifying directionality, and improving the ability of particles to overcome geometrical constraints.
To better understand diffusiophoretic transport in heterogeneous porous media, this study uses microfluidic devices that replicate natural geometries such as a sandstone. These devices provide high-resolution visualization of colloid trajectories and enable detailed pore-scale analysis. Experiments are conducted either with or without a stable and controlled salt gradient in the porous media. A dye whose behavior is analogous to that of salt is included for gradient visualization. These conditions enable a systematic comparison of polystyrene particles dynamics in the presence and absence of chemical gradient. This approach isolates the specific contribution of diffusiophoresis. The influence of local properties, such as pore morphology and connectivity, is examined. Measurements include micron-sized polystyrene particles and salt concentrations distributions and particle image velocimetry (PIV), allowing the quantification of changes in mobility, directionality, and the ability of colloids to explore geometrically constrained regions. It is found that particle behavior varies significantly depending on the experimental parameters used.
The influence of chemical gradients on colloid behavior is analyzed even in the presence of strong advective fluxes, focusing on the interplay between advection, salt diffusion, and particle diffusiophoretic mobility. The salt concentration gradient induces measurable changes in particle trajectories. These observations highlight the importance of diffusiophoresis in understanding and predicting colloid transport in heterogeneous porous structures, complementing purely hydrodynamic mechanisms.