Collective behavior

Motion (physics)

Combinatorics

Physics

Statistical physics

Pathology

Sociology

Artificial intelligence

Orientation (vector space)

Nanotechnology

Inertial frame of reference

Topology (electrical circuits)

Anthropology

Materials science

Alternative medicine

Geometry

Surface (topology)

Collective motion

Mathematics

Computer science

Medicine

Classical mechanics

Robot

Physical Review Letters

Simple ingredients, such as well-defined interactions and couplings for the velocity and orientation of self-propelled objects, are sufficient to produce complex collective behavior in assemblies of such entities. Here, we use assemblies of rodlike robots made motile through self-vibration. When confined in circular arenas, dilute assemblies of these rods act as a gas. Increasing the surface fraction leads to a collective behavior near the boundaries: polar clusters emerge while, in the bulk, gaslike behavior is retained. The coexistence between a gas and surface clusters is a direct consequence of inertial effects as shown by our simulations. A theoretical model, based on surface mediated transport accounts for this coexistence and illustrates the exact role of the boundaries. Our study paves the way towards the control of collective behavior: By using deformable but free to move arenas, we demonstrate that the surface induced clusters can lead to directed motion, while the topology of the surface states can be controlled by biasing the motility of the particles.

Boundaries Control Collective Dynamics of Inertial Self-Propelled Robots