A Mechanical Origin of Cooperative Transport

From humans hauling an oversized sofa to ants foraging a large leaf, cooperative transport is commonplace. However, achieving cooperative transport by design remains a great challenge for physicists, mechanical engineers, and roboticists. In my talk, I will present the ``transporton'', a new kind of self-propelled particle whose mechanical design gives rise to a novel dynamical response: when subjected to an external force, a transporton aligns and propagates in a direction opposite to the force. This unique force response allows these active particles to spontaneously coordinate the transport of a much larger payload. The force alignment is captured by an effective, charge-like parameter of a self-propelled particle. This effective parameter is signed and has units of curvature. We show in experiments and simulations that robots with a negative active charge push against an external payload, leading to transport, without relying on complex circuitry, sensors, or communication. Surprisingly, we find that transport increases with increasing payload size. We derive an analytical criterion for transport and find it has a geometrical origin as the interplay of two curvatures --- the payload's shape and the effective charge-like parameter. Our findings generalize existing models of self-propelled particles and offer new design rules for distributed robotic systems, potentially shedding light on cooperative transport in natural swarms.