Inertial delay of self-propelled particles

TL;DR

This paper experimentally demonstrates the significant inertial effects on self-propelled particles, revealing an inertial delay that influences their long-term dynamics and can be modeled by an underdamped Langevin approach.

Contribution

It introduces the first experimental evidence of inertia's role in active Brownian particles and develops a generalized model to explain inertial delays in self-propelled systems.

Findings

Inertial delay observed between orientation and velocity.

Inertia significantly affects long-time particle dynamics.

Underdamped Langevin model explains inertial effects.

Abstract

The motion of self-propelled massive particles through a gaseous medium is dominated by inertial effects. Examples include vibrated granulates, activated complex plasmas and flying insects. However, inertia is usually neglected in standard models. Here, we experimentally demonstrate the significance of inertia on macroscopic self-propelled particles. We observe a distinct inertial delay between orientation and velocity of particles, originating from the finite relaxation times in the system. This effect is fully explained by an underdamped generalisation of the Langevin model of active Brownian motion. In stark contrast to passive systems, the inertial delay profoundly influences the long-time dynamics and enables new fundamental strategies for controlling self-propulsion in active matter.