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

• Published in: Soft matter 2024-08, Vol.2 (33), p.6618-6626
• Main Authors: Janzen, Giulia, Matoz-Fernandez, D. A
• Format: Article
• Language: English
• Subjects: Chains (polymeric); Damping; Density; Filaments; Inertia; Peclet number; Phase transitions; Polymers; Shape effects; Unwinding; Winding
• ISSN: 1744-683X; 1744-6848; 1744-6848
• DOI: 10.1039/d4sm00572d

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 Péclet 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. We reveal that increasing density and Péclet numbers induce a reentrant phase transition in active semiflexible filaments, causing spirals to revert to chain-like shapes. This is driven by inertial effects at the level of a single polymer.