Emergent chirality and current generation

Abstract

We investigate the phenomenon of producing vibration-induced rotational motion in a cylinder filled with achiral rods and being vibrated by an external drive. The arrangement of the rods develops chirality as a result of the interaction of gravity and steric hindrance, which is responsible for the induced motion. A two-rod arrangement is sufficient to generate a persistent motion. The average angular velocity 〈ω〉 of the rods at long times varies nonmonotonically with the packing fraction ϕ for a given drive strength Γ. Though the precise nature of the variation of 〈ω〉 with ϕ depends on the details of the interaction between individual rods, its general characteristics hold true for rods of various materials and geometries. A stochastic model based on the asymmetric simple exclusion process helps in understanding the key features of our experiments.