Active droplets undergo self-sustained formation-dissolution cycles

Self-sustained formation-dissolution cycles of non-equilibrium liquid droplets have been observed to mediate biological functions such as DNA repair. The minimal physicochemcial prerequisite for such self-sustained cycles remains elusive. Here, we present a simple model with only three chemical components with their diffusive and chemical fluxes governed by non-equilibrium thermodynamics. A chemical reaction is maintained away from equilibrium by a fuel leading to active droplets. Our finding is that a single active droplet undergoes a pitchfork-bifurcation in the droplet volume upon increasing the fuel amount. Strikingly, we show that self-sustained formation and dissolution cycles emerge upon adding a further chemical reaction. We discuss how such cycles can be realized experimentally. The minimal nature of our model suggests self-sustained active droplets as modules for functions in de novo life systems.