Locomotion of Active Polymerlike Worms in Porous Media

TL;DR

This study explores how active, polymer-like worms move through different arrangements of obstacles, revealing that their diffusion depends on obstacle density and order, with implications for sorting by activity levels.

Contribution

It demonstrates the impact of obstacle arrangement on active worm locomotion and validates experimental results with polymer model simulations, highlighting new insights into active matter behavior in complex media.

Findings

Increased obstacle density enhances diffusion in disordered media.

Ordered media trap worms, reducing their mobility.

Reducing worm activity promotes spreading and enables sorting.

Abstract

We investigate the locomotion of thin, living T. tubifex worms, which display active polymerlike behavior, within quasi-2D arrays of cylindrical pillars, examining varying spatial arrangements and densities. These active worms spread in crowded environments, with a dynamics dependent on both the concentration and arrangement of obstacles. In contrast to passive polymers, our results reveal that in disordered configurations, increasing the pillar density enhances the long-time diffusion of our active polymer-like worms, while we observe the opposite trend in ordered pillar arrays. We found that in disordered media, living worms reptate through available curvilinear tubes, whereas they become trapped within pores of ordered media. Intriguingly, we show that reducing the worm's activity significantly boosts its spread, enabling passive sorting of worms by activity level. Our experimental observations are corroborated through simulations of the tangentially driven polymer model with matched persistence length predicting the same trends.