Active Brownian motion of emulsion droplets driven by nanoscale effects under laser irradiation

This work presented the results of an experimental study of dynamics of emulsion complex composition droplets under laser irradiation. The oil-in-water emulsion consisted of liquid paraffin droplets containing magnetite nanoparticles and was placed in an aqueous solution of the surfactant. The magnetite nanoparticles had characteristic dimensions of 10−8 m, which correspond to the dimensions of molecular motors in living cells. For all emulsion droplets, motion in transitional and normal diffusive modes was observed. The effective kinetic temperature of emulsion droplets was 3.5 × 103 eV and was exceeded the temperature of thermal motion of the medium molecules, 0.03 eV. Experimentally observed active Brownian motion of emulsion droplets was a result of intra-droplet motion of magnetite nanoparticles absorbing laser irradiation. Laser irradiation caused the magnetite nanoparticle heating, which generated a thermophoretic force. As a result of viscous friction forces, the nanoparticles transferred momentum to the emulsion droplet, causing its motion.