# Elasticity-based polymer sorting in active fluids: A Brownian dynamics study

## TL;DR

This study uses Brownian dynamics simulations to explore how active particles influence polymer motion, revealing superdiffusive behavior, non-monotonic diffusivity, and potential for polymer sorting based on elasticity and conformation.

## Contribution

It introduces a detailed analysis of active particle effects on polymer dynamics, highlighting non-monotonic diffusivity and conformational states relevant for sorting applications.

## Key findings

- Polymer center of mass exhibits superdiffusive motion at short times.
- Long-time diffusivity is enhanced and non-monotonic with chain length and stiffness.
- Barrier crossing times also show non-monotonic dependence, useful for polymer sorting.

## Abstract

While the dynamics of polymer chains in equilibrium media is well understood by now, the polymer dynamics in active non-equilibrium environments can be very different. Here we study the dynamics of polymers in a viscous medium containing self-propelled particles in two dimensions by using Brownian dynamics simulations. We find that the polymer center of mass exhibits a superdiffusive motion at short to intermediate times and the motion turns normal at long times, but with a greatly enhanced diffusivity. Interestingly, the long time diffusivity shows a non-monotonic behavior as a function of the chain length and stiffness. We analyze how the polymer conformation and the accumulation of the self-propelled particles, and therefore the directed motion of the polymer, are correlated. At the point of maximal polymer diffusivity, the polymer has preferentially bent conformations maintained by the balance between the chain elasticity and the propelling force generated by the active particles. We also consider the barrier crossing dynamics of actively-driven polymers in a double-well potential. The barrier crossing times are demonstrated to have a peculiar non-monotonic dependence, related to that of the diffusivity. This effect can be potentially utilized for sorting of polymers from solutions in \textit{in vitro} experiments.