Emergence of Order in Chemically Active Droplets: Temporal Dynamics and Collective Behavior

Collective behaviors such as swarming, chemical signaling, and clustering are fundamental to biological microorganisms, enabling hierarchical colony formation, coordinated motion, and enhanced nutrient accessibility─crucial for their survival. Over the past few decades, active droplets have emerged as valuable synthetic analogues, effectively replicating key biological attributes and serving as ideal platforms for investigating collective phenomena. This research explores the collective behavior of 4-cyano-4'-pentylbiphenyl (5CB) oil droplets across varying Péclet (Pe) numbers. At high Pe, droplets exhibit a pusher mode of propulsion and form dynamic chain-like patterns. Decreasing Pe enhances repulsive interactions among droplets, resulting in the inhibition of clustering. These repulsive interactions, mediated by chemical fields, lead to the emergence of an ordered structure at low Pe. Furthermore, we also illustrate how active droplets of larger size efficiently navigate within such a soft structured environment. These findings significantly contribute to our comprehension of self-organized phenomena in active matter systems.