Dynamical quorum sensing in non-living active matter

Abstract

Oscillation in the metabolism of microorganisms often depends on the cell density, where each cell interacts through the mediator concentration(s) in its environment. Such bifurcation behavior induced by the increase in cell density is called quorum sensing. Here, we found similar behavior in “active matter”, which is a non-living material that spontaneously propels itself. Active camphor disk, which freely moves on water, showed oscillatory motion with the increase in density. This oscillatory motion is not reciprocation motion but alternates between rest and rapid motion. The disks interact through the camphor concentration in its environment and the oscillatory motion originates from the slow dynamics of the environmental condition, which is the typical characteristics of dynamical quorum sensing. This is the first report about dynamical quorum sensing in active matter.