Rectification of Confined Soft Vesicles Containing Active Particles

TL;DR

This paper investigates how flexible vesicles with active particles can change shape and achieve directed motion in asymmetric channels, revealing the interplay of elastic and active forces for potential applications in micro-robotics.

Contribution

It introduces a study of shape fluctuations in active particle-filled vesicles and how these fluctuations enable rectification and directed motion in asymmetric environments.

Findings

Vesicle shape fluctuations facilitate squeezing through narrow openings.

Active particles induce rectification in asymmetric channels.

Optimal conditions for directed motion depend on elastic and active force interplay.

Abstract

One of the most promising features of active systems is that they can extract energy from their environment and convert it to mechanical work. Self propelled particles enable rectification when in contact with rigid boundaries. They can rectify their own motion when confined in asymmetric channels and that of microgears. In this paper, we study the shape fluctuations of two dimensional flexible vesicles containing active Brownian particles. We show how these fluctuations not only are capable of easily squeezing a vesicle through narrow openings, but are also responsible for its rectification when placed within asymmetric confining channels (ratchetaxis). We detail the conditions under which this process can be optimized, and sort out the complex interplay between elastic and active forces responsible for the directed motion of the vesicle across these channels.