Self-organisation of auto-phoretic suspensions in confined shear flows

Abstract

Janus phoretic particles exploit chemical energy stored in their environment to self-propel. These active particles modify and respond to their hydrodynamic and chemical environments, thus giving them a sensibility to external flows and other particles. Furthermore, experimental observations and analysis on biological or synthetic active suspensions indicate that hydro-chemical interparticle interactions lead to non-trivial collective behaviour (e.g., cluster formation of phoretic particles or bacterial swarming) and that the response of the suspensions to shear flows is non-trivial. In fact, it can lead to significant reductions in viscosity due to the energy conversion at microscopic scales. In this work, using simulations of a continuum kinetic model, we analyse the dynamics and response to shear and confinement of dilute suspensions of chemotactic phoretic particles that reorient and drift toward the chemical solutes released by their neighbours. We show that a 1D transient steady distribution driven by the effect of confinement is a common feature considered and analyse its stability for varying confinement strength and shear rate. In the second step, we consider and discuss, more specifically, the feedback effect on the flow by the particle and the resulting effective viscosity of the suspension.