Fluid dynamics in active emulsions

Chemically-active emulsions can drive hydrodynamic flows. We study these flows in active phase-separating systems by considering a binary fluid mixture that demixes in the presence of monomolecular chemical reactions in which its two components interconvert at fixed rates. These chemical reactions maintain the system away from thermodynamic equilibrium and drive the dynamics of the two phases as fluid flows ensue. This minimal system – a binary fluid mixture with simple (active) reactions – gives rise to a multitude of patterns and dynamics ranging from static pattern formation to spatiotemporal chaos. The chaotic behaviour is neither due to the inertia of the fluid, which we neglect, nor like the turbulence of active nematics observed at low Reynolds number, for ours is only a scalar mixture. Finally, we predict the range of parameter values corresponding to these different regimes.