Diffusiophoretic Transport of Colloids in Complex Environments: from soil to the oceans

Colloid transport in complex flow environments plays a central role in environmental and biomedical systems, from drug delivery and filtration to the dispersion of microplastics in aquatic ecosystems. Chemical gradients are ubiquitous in these environments, and can lead to the diffusiophoretic transport of colloids. Yet, classical transport models do not account for these phoretic effects. Here, we demonstrate that even weak solute gradients can profoundly alter particle trajectories, dispersion, and spreading, even in the presence of strong background flows. Our microfluidic experiments with ordered/disordered obstacle arrays as analog 2D porous media demonstrate that solute-mediated cross-streamline migration of colloids significantly modulates their macroscopic spreading and dispersion. Our experiments with electromagnetically driven 2D cellular and chaotic flows further demonstrate that phoretic effects strongly modulate particle accumulation, escape dynamics, and interactions with coherent transport barriers. Our work therefore reveals the broad relevance of phoretic migration across diverse settings and underscores the need to incorporate these physicochemical effects into predictive models of particle transport in complex environments.