Phase Separation by Entanglement of Active Polymerlike Worms

TL;DR

This study explores how active, worm-like polymers such as T. tubifex worms undergo phase separation through active motion and coalescence, revealing a novel mechanism distinct from traditional polymer phase separation.

Contribution

It introduces a new understanding of phase separation in active polymers, showing that active motion leads to a unique coalescence process different from classical droplet growth.

Findings

Worms spontaneously aggregate into entangled blobs.

Phase separation occurs via active motion and coalescence, not Ostwald ripening.

Diffusion constant of blobs is size-independent due to surface activity.

Abstract

We investigate the aggregation and phase separation of thin, living T. tubifex worms that behave as active polymers. Randomly dispersed active worms spontaneously aggregate to form compact, highly entangled blobs, a process similar to polymer phase separation, and for which we observe power-law growth kinetics. We find that the phase separation of active polymerlike worms does not occur through Ostwald ripening, but through active motion and coalescence of the phase domains. Interestingly, the growth mechanism differs from conventional growth by droplet coalescence: the diffusion constant characterizing the random motion of a worm blob is independent of its size, a phenomenon that can be explained from the fact that the active random motion arises from the worms at the surface of the blob. This leads to a fundamentally different phase-separation mechanism that may be unique to active polymers.