Surfing and crawling macroscopic active particles under strong confinement -- inertial dynamics

TL;DR

This paper investigates the complex inertial dynamics of macroscopic active particles under confinement, revealing novel behaviors driven by active noise and inertia, distinct from microscopic counterparts.

Contribution

It introduces a combined experimental, theoretical, and numerical study of macroscopic active particles, emphasizing the role of inertia in their confined dynamics.

Findings

Particles accumulate at a finite distance within boundaries.

Three distinct dynamical states are identified.

Inertia significantly influences macroscopic active matter behavior.

Abstract

We study two types of active (self-propelled) macroscopic particles under confinement: camphor surfers and hexbug crawlers, using a combined experimental, theoretical, and numerical approach. Unlike widely studied microscopic active particles and swimmers, where thermal forces are often important and inertia is negligible, our macroscopic particles exhibit complex dynamics due expressly to active non-thermal noise combined with inertial effects. Strong confinement induces accumulation at a finite distance within the boundary and gives rise to three distinguishable dynamical states; both depending on activity and inertia. These surprisingly complex dynamics arise already at the single particle level -- highlighting the importance of inertia in macroscopic active matter.