Distortion and destruction of colloidal flocks in disordered environments

Abstract

How do flocks, herds and swarms proceed through disordered environments? This question is not only crucial to animal groups in the wild, but also to virtually all applications of collective robotics, and active materials composed of synthetic motile units. In stark contrast, appart from very rare exceptions, our physical understanding of flocking has been hitherto limited to homogeneous media. Here we explain how collective motion survives to geometrical disorder. To do so, we combine experiments on motile colloids cruising through random microfabricated obstacles, and analytical theory. We explain how disorder and bending elasticity compete to channel the flow of polar flocks along sparse river networks akin those found beyond plastic depinning in driven condensed matter. Further increasing disorder, we demonstrate that collective motion is suppressed in the form of a first-order phase transition generic to all polar active materials.

Final version published in Nature Physics

References in corpus (5)

• Novel type of phase transition in a system of self-driven particles
• Spontaneous motion in hierarchically assembled active matter
• Fluid Flows Created by Swimming Bacteria Drive Self-Organization in Confined Suspensions
• Emergent vortices in populations of colloidal rollers
• From Phase to Micro-Phase Separation in Flocking Models: The Essential Role of Non-Equilibrium Fluctuations

Cited by in corpus (9)

• Dynamic Phases of Active Matter Systems with Quenched Disorder
• Schools of skyrmions with electrically tunable elastic interactions
• Oscillatory chiral flows in confined active fluids with obstacles
• Microscopic theory for the diffusion of an active particle in a crowded environment
• Risk and interaction aversion: screening mechanisms in the Prisoner's Dilemma game
• Metastable Clusters and Channels Formed by Active Particles with Aligning Interactions
• Colloidal Brazil nut effect in microswimmer mixtures induced by motility contrast
• Pushing run-and-tumble particles through a rugged channel
• Active uniaxially ordered suspensions on disordered substrates