Diffusiophoretic colloidal banding and emergent hydrodynamic instability.

Diffusiophoresis, the motion of colloids or macromolecules induced by concentration gradients of chemical species, represents a fundamental transport mechanism underlying many natural and biological processes. A classic signature of diffusiophoresis is the emergence of colloidal banding, i.e., regions of high particle density. We show that this property can be used to trigger hydrodynamic instabilities when coupled with a destabilizing driving force. Here, we will present a combination of experiments and multiphysics simulations to investigate the exclusion zone formation near ion-exchange membranes and the associated flow instabilities. Our simulation model quantitatively reproduces key experimental observations and enables systematic exploration of how diffusiophoresis can be exploited to influence flow patterns and induce mixing. We discuss how these responses can be controlled by the suspension's chemical and physical properties as well as by the system geometry.