Photophoretic velocimetry—a new way for the in situ determination of particle size distribution and refractive index of hydrocolloids

摘要

The migration of particles induced by the forces of light is known as photophoresis. The photophoreticnvelocity of particles under the influence of a strong light source, e.g. a laser beam, is recorded andnmeasured by means of digital image processing which is called photophoretic velocimetry (PPV). Thenphotophoretic velocity depends on the particle size as well as on its refractive index. By applying PPV,nwe show the determination of the intrinsic properties of polystyrene (PS), melamine resin (MF) andnSiO2 particles, deduced from velocity distributions of both monodisperse as well as polydispersensuspensions. Especially the continuous determination of the refractive index of single hydrocolloids isnof great interest for quality assurance and the discrimination of polydisperse biological or inorganicnsamples. Also, PPV is not restricted to in water dispersed samples only.