Colloidal transport by active filaments

TL;DR

This paper demonstrates that active filaments attached to colloidal spheres can induce ballistic transport, surpassing diffusion limits, with transport efficiency depending on filament conformational states, resembling microorganism flagellar propulsion.

Contribution

It introduces a model of active filaments that enables internal energy-driven colloidal transport, revealing conformational states that optimize speed and efficiency.

Findings

Transport speed varies with filament conformations.

Filament writhe correlates with transport efficiency.

Resembles microorganism flagellar propulsion.

Abstract

Enhanced colloidal transport beyond the limit imposed by diffusion is usually achieved through external fields. Here, we demonstrate the ballistic transport of a colloidal sphere using internal sources of energy provided by an attached active filament. The latter is modeled as a chain of chemo-mechanically active beads connected by potentials that enforce semi-flexibility and self-avoidance. The fluid flow produced by the active beads and the forces they mediate are explicitly taken into account in the overdamped equations of motion describing the colloid-filament assembly. The speed and efficiency of transport depend on the dynamical conformational states of the filament. We characterize these states using filament writhe as an order parameter and identify ones yielding maxima in speed and efficiency of transport. The transport mechanism reported here has a remarkable resemblance to the flagellar propulsion of microorganisms which suggests its utility in biomimetic systems.