# Biopolymer dynamics driven by helical flagella

## TL;DR

This study uses simulations to explore how a rotating helical flagellum influences nearby polymers, revealing polymer accumulation and elongation effects that depend on polymer length, which impacts microbial interactions with their environment.

## Contribution

It provides new insights into the hydrodynamic and steric interactions between rotating helical flagella and polymers, highlighting polymer migration and elongation near active microbes.

## Key findings

- Polymers migrate radially inward near the helix.
- Polymer elongation increases with polymer length.
- Helix actuation enhances polymer accumulation within its volume.

## Abstract

Microbial flagellates typically inhabit complex suspensions of polymeric material which can impact the swimming speed of motile microbes, filter-feeding of sessile cells, and the generation of biofilms. There is currently a need to better understand how the fundamental dynamics of polymers near active cells or flagella impacts these various phenomena, in particular the hydrodynamic and steric influence of a rotating helical filament on suspended polymers. Our Stokesian dynamics simulations show that as a stationary rotating helix pumps fluid along its long axis, polymers migrate radially inwards while being elongated. We observe that the actuation of the helix tends to increase the probability of finding polymeric material within its pervaded volume. This accumulation of polymers within the vicinity of the helix is stronger for longer polymers. We further analyse the stochastic work performed by the helix on the polymers and show that this quantity is positive on average and increases with polymer contour length.