Optofluidic microconvection with magnetic nanoparticles: Novel interaction of thermal diffusion and magnetic field

Abstract

Light-matter interactions are exploited in many applications, whereas superparamagnetic nanoparticles allow to introduce magnetic field control in diverse fluid environments. We study the structure of laser-induced thermal lens in thin layers of ferromagnetic colloid and predict significant magnetoconvective motion around the beam spot. It was found that localized heating depletes/accumulates magnetic nanoparticles in the beam-spot by thermal diffusion and collective magnetic interactions of nanoparticles produce strong microconvective currents. This mode of mass transport can be controlled by magnetic field. We expect the novel magnetosolutal microconvective coupling, which we describe, can be a multifunctional approach for precision optical manipulation and mixing of small fluid volumes using magnetic nanoparticles within integrated microfluidic devices.