Particles that are attracted to a chemical source actually spread out faster and further than particles that are repelled by it.
You would expect that if particles are attracted to a specific spot, they would cluster together and stay put. In the complex world of porous media like soil or rock, the opposite happens due to diffusiophoretic dispersion. Particles drawn toward a solute-rich blob are actually swept away more efficiently by the surrounding fluid flow. This counterintuitive reversal means that attraction in the ground actually leads to faster contamination spreading. This discovery forces environmental scientists to rethink how pollutants and nutrients travel through the Earth. It reveals that our basic assumptions about how things mix underground might be completely wrong.
Diffusiophoretic dispersion of a colloidal blob in porous media
arXiv · 2605.04424
Predicting and controlling the transport of colloids in porous media is essential for applications ranging from contaminant remediation to drug delivery. In these complex environments, solute gradients are ubiquitous and could drive diffusiophoretic particle migration, yet their impact on macroscopic colloid dispersion remains poorly understood. Here we combine experiments and simulations to quantify how diffusiophoresis alters the spreading of a colloidal blob in a 2D ordered/disordered porous