Emergent Chirality and Current Generation

TL;DR

This paper explores how vibrated achiral rods in a cylinder develop emergent chirality and induce rotational motion, with a stochastic model explaining the observed phenomena.

Contribution

It demonstrates that simple arrangements of achiral rods can produce persistent rotational motion through emergent chirality, supported by experimental and modeling insights.

Findings

Rotation depends non-monotonically on packing fraction

Emergent chirality arises from gravity and steric interactions

A stochastic model captures key experimental features

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 $\langle \omega \rangle$ of the rods at long times varies non-monotonically with the packing fraction $\phi$ for a given drive strength $\Gamma$. Though the precise nature of the variation of $\langle \omega \rangle$ with $\phi$ 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.