Dominant mechanism for pattern-length selection in chemically active emulsions

Determine whether reaction-diffusion length scales arising from sustained non-equilibrium A↔B chemical conversions or the conservation law for total mass of the interconverting species (for example, ψ = (φ_A + φ_B)/2) governs the selection of pattern length scales in chemically active emulsions, defined as multi-component mixtures that undergo liquid–liquid phase separation while components convert into each other under non-equilibrium conditions.

Background

In passive phase-separating systems, lever rules associated with conserved quantities determine the equilibrium volumes of condensed phases and thereby set characteristic length scales. In contrast, chemically active emulsions are maintained away from equilibrium and exhibit reaction-diffusion length scales due to persistent interconversion of components, complicating the mechanism of pattern selection.

The paper contrasts these two determinants—reaction-diffusion length scales and conservation laws—and highlights that their competition is central to understanding droplet size and spacing in active emulsions. While the authors introduce a minimal ternary model and analyze scenarios leading to intensive or extensive droplets, the general dominance of one mechanism over the other in active emulsions is posed as an explicit unresolved question.