Non-Gaussian statistics for the motion of self-propelled Janus particles: experiment versus theory

TL;DR

This study combines experiments and theory to analyze the non-Gaussian statistical behavior of self-propelled Janus particles, revealing distinct motion regimes and validating theoretical predictions about their displacement distributions.

Contribution

It introduces a comprehensive theoretical model for the Langevin dynamics of active particles with coupled translational and rotational motion, validated by experimental data.

Findings

Identification of three motion regimes: Brownian, super-diffusive, and diffusive.

Experimental verification of non-Gaussian displacement distributions.

Observation of peaked and double-peak structures in displacement probability distributions.

Abstract

Spherical Janus particles are one of the most prominent examples for active Brownian objects. Here, we study the diffusiophoretic motion of such microswimmers in experiment and in theory. Three stages are found: simple Brownian motion at short times, super-diffusion at intermediate times, and finally diffusive behavior again at long times. These three regimes observed in the experiments are compared with a theoretical model for the Langevin dynamics of self-propelled particles with coupled translational and rotational motion. Besides the mean square displacement also higher displacement moments are addressed. In particular, theoretical predictions regarding the non-Gaussian behavior of self-propelled particles are verified in the experiments. Furthermore, the full displacement probability distribution is analyzed, where in agreement with Brownian dynamics simulations either an extremely broadened peak or a pronounced double-peak structure is found depending on the experimental conditions.