Collective filament wrapping and nested spiral formation in active polydisperse systems

TL;DR

This paper uncovers how active, polydisperse filaments self-organize into nested spiral structures through a collective wrapping mechanism, with filament length controlling the assembly and disassembly processes in active matter.

Contribution

It introduces a novel collective wrapping mechanism in active polydisperse systems, highlighting filament length disparity as a key factor in hierarchical self-assembly.

Findings

Nested spiral structures form at intermediate activity levels.

Structural transitions occur with increasing activity, leading to disassembly.

Filament length disparity governs the organization and dynamics.

Abstract

We investigate a two-dimensional polydisperse suspension of self-propelled semiflexible filaments and reveal a collective wrapping mechanism that is absent in monodisperse systems. At intermediate activity levels, long filaments coil around shorter ones, forming nested spiral structures stabilized by filament length disparity. These assemblies generalize the single-filament spiraling seen in active systems into cooperative, multi-filament configurations. As activity increases, the nested spirals undergo structural transitions: medium-length filaments unwind, longer filaments encapsulate shorter ones, and eventually all spiral structures dissolve. This reorganization is reflected in the dynamics, where van Hove distributions uncover coexisting confined and motile filament populations. Our findings identify filament length as a key control parameter for nonequilibrium self-assembly and establish inter-filament wrapping as a minimal mechanism for hierarchical organization in active matter. This mechanism provides a simple model for the cooperative confinement and structural hierarchy observed in both biological and synthetic active systems.