Passive particle transport using a transversely propelling polymer “sweeper”

Abstract

Using Langevin dynamics simulations, we study a system of a transversely propelling polymer and passive Brownian particles. We consider a polymer whose monomers experience a constant propulsion force perpendicular to the local tangents, surrounded by passive particles undergoing thermal fluctuations in two dimensions. We demonstrate that the sideways propelling polymer can act as a sweeper to collect the passive Brownian particles, mimicking a shuttle-cargo system. The number of particles the polymer collects during its motion increases with time and finally saturates to a maximum number. Moreover, the velocity of the polymer decreases as the particles get trapped due to the extra drag they generate. Rather than going to zero, the polymer velocity eventually reaches a terminal value close to the contribution from the thermal velocity when it collects the maximum load. We show that, apart from the length of the polymer, the propulsion strength and the number of passive particles are the deciding factors for the maximum trapped particles. In addition, we demonstrate that the collected particles arrange themselves in a triangular, closed, packed state, similar to what has been observed in experiments. Our study reveals that the interplay between stiffness and active forces induces morphological changes in the polymer during particle transport, suggesting novel ways of designing robophysical models for particle collection and transport.