Fluid flow and spatiotemporal chaos in chemically active emulsions

Abstract: We study phase-separating fluid mixtures as they demix in the presence of chemical reactions that maintain them away from thermodynamic equilibrium. We show that in such chemically active emulsions the interplay of chemical reactions, phase separation, and hydrodynamics effects complex self-organisation and pattern formation that can give rise to spatiotemporal chaos. This chaotic dynamics, unlike in classical turbulence, is not due to fluid inertia $-$ we analyse the system in the Stokes flow regime $-$ and it is different from the $\textit{turbulence}$ of active nematics at low Reynolds number, for our fluid mixtures lack any orientational order. To explore the generic features of nonlinear dynamics in our system, we derive amplitude equations which we find to be identical to those obtained for Rayleigh-Benard convection with mean flow and stress-free conditions at the top and bottom plates. Chemically active emulsions possessing no internal order, we thus establish, can exhibit chaoticity that is driven by interfacial stresses in the fluid mixture.