Braiding dynamics in semiflexible filament bundles under oscillatory forcing

TL;DR

This paper investigates how oscillatory forces induce topological braid defects in semiflexible filament bundles, revealing non-equilibrium defect proliferation and complex length dynamics under tension, with implications for experimental studies.

Contribution

It introduces a detailed analysis of defect creation and dynamics in filament bundles under cyclic forces, highlighting non-equilibrium phenomena not captured by equilibrium models.

Findings

Compression cycles promote pair production of braid defects.

Tension causes nonmonotonic length creep due to braid motion.

Oscillatory forcing leads to defect proliferation beyond thermal equilibrium.

Abstract

We examine the nonequilibrium production of topological defects -- braids -- in semiflexible filament bundles under cycles of compression and tension. During these cycles, the period of compression facilitates the thermally activated pair production of braid/anti-braid pairs, which then may separate when the bundle is under tension. As result, appropriately tuned alternating periods of compression and extension should lead to the proliferation of braid defects in a bundle so that linear density of these pairs far exceeds that expected in thermal equilibrium. Secondly, we examine the slow extension of braided bundles under tension, showing that their end-to-end length creeps nonmonotonically under a fixed force due to braid deformation and the motion of the braid pair along the bundle. We conclude with a few speculations regarding experiments on semiflexible filament bundles and their networks.