External seminar - Jacqueline Janssen (Max Planck Institut - IMPRS-CellDevoSys)

Abstract: Droplets form via phase separation and coexist with a dilute phase. After nucleation and growth of droplets, the resulting emulsion of many droplets undergoes coarsening kinetics to reach its thermal equilibrium state. Ostwald ripening describes the coarsening kinetics of emulsions for which the total droplet material is conserved. During Ostwald ripening, the droplet number density decreases, the average radius increases, and the droplet size distribution function broadens in a universal manner. Phase separation and kinetics of emulsions are relevant for the spatial organization of cells and for synthetic chemical systems. In these systems, droplet material is often not conserved due to the active production of droplet building blocks by fuel-driven chemical reaction cycles. In this talk, I will introduce the theoretical framework for coarsening in emulsions with matter supply, which comprises diffusion limited and interface-kinetics limited growth regimes. I will discuss the effect of matter supply on the statistics of droplet sizes and the universality of the droplet size distribution function.  We find that matter supply can transiently decouple emulsions and lead to new scaling behaviors. Furthermore, I will apply the theory to discuss experimental results, which show accelerated ripening in chemically-fuelled emulsions. Our theory can explain the effect of the chemical reaction cycle on emulsions' transient and long-term kinetics. The importance of this work is in understanding how matter supply can lead to size control in chemically-active emulsions, which can be a possible regulatory mechanism mediated by biomolecular condensates in living cells.