Dynamics of wet granular hexagons

TL;DR

This study explores how the shape and wetting of hexagonal disks influence their collective behavior under vibration, leading to self-organized rotating hexagonal structures with geometric frustration.

Contribution

It demonstrates how particle shape and wetting-induced cohesion can tune the collective dynamics of granular matter in a vibrated monolayer.

Findings

Hexagons prefer to rotate under strong vibration.

Wetting introduces cohesive liquid bridges.

Self-organized rotating hexagonal structures form.

Abstract

The collective behavior of vibrated hexagonal disks confined in a monolayer is investigated experimentally. Due to the broken circular symmetry, hexagons prefer to rotate upon sufficiently strong driving. Due to the formation of liquid bridges, short-ranged cohesive interactions are introduced upon wetting. Consequently, a nonequilibrium stationary state with the rotating disks self-organized in a hexagonal structure arises. The bond length of the hexagonal structure is slightly smaller than the circumdiameter of a hexagon, indicating geometric frustration. This investigation provides an example where the collective behavior of granular matter is tuned by the shape of individual particles.