Tunable assembly and disassembly of active droplet clusters

Biological self-organization occurs in diverse systems and scales where individual, motile agents interact with their neighbors via physical and chemical means. Inspired by nature, synthetic active matter, seeks to recreate this dynamic organization. We study active droplets, oil droplets that spontaneously self-propel in a surfactant solution. With recent advancements, these droplets have been bonded together to form active, flexible polymers. However, these droplets are auto-chemo-repulsive, which limits the range of higher-order structures accessible with these active polymer systems. Furthermore, the hydrodynamic interaction of these active droplets typically prevents stable ordering or clustering in 2D. By forming droplets from liquid crystal oils, the internal order of the droplet can be controlled externally via temperature, which in turn affects the activity of the system. By tuning the temperature and surfactant choice, we find rich droplet dynamics and present a new emergent attractive interaction and self-organization of motile liquid crystal droplets under 2D confinement.