Active droplets as model of bacterial colonies

Examples of active systems appear in various biological settings, such as flocks of birds, cell cytoskeleton and bacterial colonies. These out-of-equilibrium systems constantly transduce and dissipate energy and may exhibit phase separation, which in active matter can differ fundamentally from passive phase separation governed by free energy minimization. In this talk, we focus on phase separation occurring in bacterial colonies due to intracellular force generation. We use a continuum approach, representing bacterial colonies as active materials, which exhibit different surface profiles and position-dependent motility gradients. Moreover, the coalescence of two such droplets exhibits two time scales which cannot be solely understood by surface tension and viscosity. Our theoretical framework of active droplets provides a means of describing bacterial colony formation and can be extended to other cellular aggregates.