Active Janus particles in a complex plasma

TL;DR

This study experimentally investigates active Janus particles in a plasma, revealing their unique motion patterns, interactions, and propulsion mechanisms, notably photophoretic force, leading to complex plasma dynamics.

Contribution

First experimental analysis of Janus particles in plasma, identifying their motion, interactions, and propulsion mechanisms in a plasma sheath environment.

Findings

Janus particles exhibit looped trajectories with spinning and circling motion.

Interactions among particles lead to complex, non-Maxwellian velocity distributions.

Photophoretic force is identified as the main propulsion mechanism.

Abstract

Active Janus particles suspended in a plasma were studied experimentally. The Janus particles were micron-size plastic microspheres, one half of which was coated with a thin layer of platinum. They were suspended in the plasma sheath of a radio-frequency discharge in argon at low pressure. The Janus particles moved in characteristic looped trajectories suggesting a combination of spinning and circling motion; their interactions led to the emergence of rich dynamics characterized by non-Maxwellian velocity distribution. The particle propulsion mechanism is discussed, the main force driving the particle motion is identified as photophoretic force.