Density and inertia effects on two-dimensional active semiflexible filament suspensions

TL;DR

This study investigates how density and inertia influence the structural transitions of active semiflexible filaments in two-dimensional suspensions, revealing a reentrant phase transition from spirals to chains driven by inertial effects and interactions.

Contribution

It introduces a detailed numerical simulation analysis of density and inertia effects on active semiflexible filaments, highlighting a novel reentrant phase transition mechanism.

Findings

Increasing density causes spiral structures to break into chains.

Higher inertia leads to unwinding of spiral filaments.

Interactions among extended arms can fully unwind spirals.

Abstract

We examine the influence of density on the transition between chain and spiral structures in planar assemblies of active semiflexible filaments, utilizing detailed numerical simulations. We focus on how increased density, and higher P\'eclet numbers, affect the activity-induced transition spiral state in a semiflexible, self-avoiding active chain. Our findings show that increasing the density causes the spiral state to break up, reverting to a motile chain-like shape. This results in a density-dependent reentrant phase transition from spirals back to open chains. We attribute this phenomenon to an inertial effect observed at the single polymer level, where increased persistence length due to inertia has been shown in recent three-dimensional studies to cause polymers to open up. Our two-dimensional simulations further reveal that a reduction in the damping coefficient leads to partial unwinding of the spirals, forming longer arms. In suspension, interactions among these extended arms can trigger a complete unwinding of the spirals, driven by the combined effects of density and inertia.