Biomimetic Swarm of Active Particles with Coupled Passive-Active Interactions

TL;DR

This paper investigates a class of biomimetic active colloids inspired by natural collective behaviors, demonstrating their ability to self-organize into various ordered states and revealing universal dynamics driven by interaction parameters.

Contribution

It introduces a model of active colloids with off-center interactions that self-organize into polar swarms, showing universal behavior explained by effective volume fractions and interaction ranges.

Findings

System transitions from crystalline to gas-like states with varying noise and density.

Long-range order and directional motion emerge without hydrodynamic interactions.

Universal behavior explained by force-range and torque-range based effective volume fractions.

Abstract

We study the universal behavior of a class of active colloids whose design is inspired by the collective dynamics of natural systems like schools of fish and flocks of birds. These colloids, with off-center repulsive interaction sites, self-organize into polar swarms exhibiting long-range order and directional motion without significant hydrodynamic interactions. Our simulations show that the system transitions from motile perfect crystals to solid-like, liquid-like and gas-like states depending on noise levels, repulsive interaction strength, and particle density. By analyzing swarm polarity and hexatic bond order parameters, we demonstrate that effective volume fractions based on force-range and torque-range interactions explain the system's universal behavior. This work lays a groundwork for biomimetic applications utilizing the cooperative dynamics of active colloids.