Synchronized Intermittent Motion Induced by the Interaction between Camphor Disks

A new mode of collective motion was discovered in a system of camphor disks floating on the water surface in a circular chamber. The mode was induced by tuning the number of the disks. A single or few disks are known to continuously move on the water surface. Conversely, when many disks are present, motion comes to a stop and the disks form ordered spatial patterns by repulsive interaction. Here we found the third mode that emerged at an intermediate disk number, in which inactive and active motion phases alternated non-periodically. This new mode exhibited synchronization as the disk number increased.