Active Motion of Janus Particle by Self-thermophoresis in Defocused Laser Beam

TL;DR

This paper investigates the self-propulsion mechanism of Janus particles driven by self-thermophoresis under laser irradiation, providing experimental measurements and demonstrating a micro-rotor heat engine application.

Contribution

It experimentally measures temperature distribution and flow fields around Janus particles, validating propulsion models and demonstrating a micro-rotor heat engine.

Findings

Measured temperature gradients match propulsion predictions.

Demonstrated a functioning micro-rotor heat engine.

Validated thermophoresis as a propulsion mechanism.

Abstract

We study self-propulsion of a half-metal coated colloidal particle under laser irradiation. The motion is caused by self-thermophoresis: i.e. absorption of laser at the metal-coated side of the particle creates local temperature gradient which in turn drives the particle by thermophoresis. To clarify the mechanism, temperature distribution and a thermal slip flow field around a micro-scale Janus particle are measured for the first time. With measured temperature drop across the particle, the speed of self-propulsion is corroborated with the prediction based on accessible parameters. As an application for driving micro-machine, a micro-rotor heat engine is demonstrated.