Co-operative motion of multiple benzoquinone disks at the air-water interface.

Self-motion of physical-chemical systems is a promising avenue for studying and developing mechanical functions with inanimate systems. In this paper, we investigate spontaneous motion of collections of solid macroscopic benzoquinone (BQ) disks at the air-water interface without intervention of chemical reactions. The BQ particles slowly dissolve and create heterogeneous interfacial tension fields on the water surface that drive the motion. Spontaneous, continuous locomotion was observed between multiple BQ particles, along with coupling, collisions, cycling and collective foraging for interfacial free energy. Analysis of the motion suggests co-operative behavior depends strongly on particle shape.