Coacervate droplets as minimal models of dynamic cellular compartments

Liquid-liquid phase separation (LLPS) has emerged as a key mechanism in living cells, underlying the formation of biomolecular condensates that dynamically organize cellular matter, regulate reactions, and interact with membranes. Reproducing these features in minimal synthetic models remains a central challenge. In this talk, I will present coacervate droplets as minimal models of dynamic cellular compartments. I will first describe how light can be used as an external energy input to program coacervate phase behaviour. Using photoswitchable DNA-azobenzene systems, we achieve reversible and spatially controlled coacervation, enabling precise regulation of droplet formation and dissolution. By combining these systems with droplet-based microfluidics, we quantitatively dissect the kinetics of light-induced phase transitions and uncover non-equilibrium behaviours, such as budding and self-division. I will further illustrate how coacervates can function as reactive compartments, promoting and regulating simple chemical reactions, and how reaction-driven changes in molecular composition feed back onto phase behaviour. Finally, I will briefly discuss recent advances on coacervate-vesicle interactions, showing how condensates selectively wet phase-separated lipid membranes, a key step toward hybrid synthetic cells that integrate both membraneless and membrane-bound organization. Overall, this work shows how coacervate droplets provide minimal yet informative platforms to investigate dynamic compartmentalization principles relevant to biomolecular condensates and synthetic protocells.