Light-induced self-thermophoresis of Janus spheroidal nanoparticles.

A theoretical framework is provided for determining the self-thermophoretic velocity of a light irradiated spheroidal Janus nanoparticle consisting of symmetric dielectric and perfectly conducting semi-spheroids. The analysis is based on solving the linearized Joule heating problem due to uniform laser irradiance and on explicitly determining the temperature fields inside and outside the particle. We employ the thermoelectric (Peltier- Seebeck) methodology to find the surface self - induced temperature gradient and the related slip velocity which determines the autonomous phoretic (self - propulsion) mobility of the Janus particle. Simplified explicit expressions for the self - thermophoretic velocities of spheroidal (prolate and oblate) Janus particles in terms of their aspect ratios are found and few practical limiting cases (i.e., sphere, disk and needle) are also discussed.