Life-like swarm behavior of multiple chemotactic droplets

Abstract

Collective behavior, swarming and mutual interactions between living entities are well-known phenomena in biology where, for example, flocks of birds or schools of fish are extensively studied. Swarming has also been observed in bacteria or tumor cell populations. This kind of collective behavior can be implemented also in non-living systems, namely in biologically-inspired swarm robotics. However, the collective behavior of chemical droplets (mutual interactions of multiple “liquid robots”) has not been studied before and the present paper reports the experimentally observed phenomena and modes of behavior in such system. We show how multiple decanol droplets in a thin layer of decanoate solution behave and interact. We report, for the first time, several life-like features such as collective chemotaxis and number-dependent group formation.