Self-organisation and rheology of phoretic suspensions in confined pressure-driven flows

Phoretic particles exploit the interfacial flows driven at their surface by self-generated physico-chemical gradients to self-propel and interact through the long-ranged hydrodynamic and chemical footprints they leave on their environment. For example, in the absence of any external flow, such interactions lead to the dynamic clustering of chemotactic particles.



An external flow, as well as the presence of confining wall, modifies these spontaneous dynamics. We numerically solve a kinetic model to study the self-organisation of dilute phoretic suspensions in pressure-driven flows within a thin confined layer. For a fixed confinement, four regimes are identified depending on the flow strength, ranging from stationary streamwise uniform distribution of particles to the highly dynamic evolution of two-dimensional patterns. These observed collective dynamics are physically explained with the aid of a reduced model of the suspension.



Active particles also exert mechanical stresses on the surrounding flow. Their collective organisation therefore modifies the stress-strain relationship within the suspension, providing a first insight on the active rheological opportunities of such phoretic suspensions.