Emergence of collective dynamical chirality for achiral active particles

TL;DR

This paper demonstrates that collective dynamical chirality can spontaneously emerge in systems of simple, achiral active particles, driven by active motion, confinement, and hydrodynamic interactions, leading to diverse chiral behaviors.

Contribution

It reveals the novel phenomenon of CDC arising from achiral units, expanding understanding of chiral structure formation in active matter systems.

Findings

CDC can spontaneously form in achiral particle systems

Multiple collective behaviors observed, including rotation and oscillation

Transitions between different chiral and structural states

Abstract

Emergence of collective dynamical chirality (CDC) at mesoscopic scales plays a key role in many formation processes of chiral structures in nature, which may also provide possible routines for people to fabricate complex chiral architectures. So far, most of reported CDCs are found in systems of active objects with individual structure chirality or/and dynamical chirality, and whether CDC can arise from simple and achiral units is still an attractive mystery. Here, we report a spontaneous formation of CDC in a system of both dynamically and structurally achiral particles motivated by active motion of cells. Active moving, confinement and hydrodynamic interaction are found to be the three key factors. Detailed analysis shows that the system can support abundant collective dynamical behaviors, including rotating droplet, rotating bubble, CDC oscillation, array of collective rotation, as well as interesting transitions such as chirality transition, structure transition and state reentrance.