Laser Photophoresis of a Single Droplet in Oil in Water Emulsions

Abstract

Laser photophoretic behavior of an organic droplet in oil in water (o/w) emulsions was examined by radiating a single-mode Nd:YAG laser (1064 nm). In the nine emulsion systems examined, the photophoretic velocity (μm s-1) of an organic droplet was found to be linearly proportional to both the laser power and the radius of the droplet. Furthermore, for droplets of the same size, the photophoretic mobility (μm s-1 W-1), which means the photophoretic velocity normalized with the laser power, increased as the refractive index of the droplet increased. The dependence of the photophoretic mobility was discussed on the basis of a simple radiation theory in which a scattering force of a laser beam on a spherical droplet was formulated.