Translational and rotational dynamics of a self-propelled Janus probe in crowded environments

TL;DR

This study uses simulations to analyze how a self-propelled Janus particle moves in crowded environments, revealing complex dynamics influenced by crowder type, interaction, and self-propulsion, with implications for understanding active particle behavior.

Contribution

It provides new insights into the translational and rotational dynamics of self-propelled Janus probes in various crowded environments, highlighting the effects of crowder nature and interactions.

Findings

Mean square displacements show a three-step growth pattern.

Self-propulsion increases displacement regardless of crowder type.

Decoupling of translational and rotational dynamics occurs at intermediate crowder density.

Abstract

We computationally investigate the dynamics of a self-propelled Janus probe in crowded environments. The crowding is caused by the presence of viscoelastic polymers or non-viscoelastic disconnected monomers. Our simulations show that the translational, as well as rotational mean square displacements, have a distinctive three-step growth for fixed values of self-propulsion force, and steadily increase with self-propulsion, irrespective of the nature of the crowder. On the other hand, in the absence of crowders, the rotational dynamics of the Janus probe is independent of self-propulsion force. On replacing the repulsive polymers with sticky ones, translational and rotational mean square displacements of the Janus probe show a sharp drop. Since different faces of a Janus particle interact differently with the environment, we show that the direction of self-propulsion also affects its dynamics. The ratio of long-time translational and rotational diffusivities of the self-propelled probe with a fixed self-propulsion, when plotted against the area fraction of the crowders, passes through a minima and at higher area fraction merges to its value in the absence of the crowder. This points towards the decoupling of translational and rotational dynamics of the self-propelled probe at intermediate area fraction of the crowders. However, such translational-rotational decoupling is absent for passive probes.