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

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 a 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 microscale 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 a micromachine, a microrotor is demonstrated. DOI: http://dx.doi.org/10.1103/PhysRevLett.105.268302 Received 11 September 2010Published 20 December 2010© 2010 The American Physical Society