Photo-thermophoresis as a new tool for aerosol characterization

Aerosols are particles in the size range of nanometers to some micrometers, suspended in air or other gases. Their characterization and separation according to different physical and chemical properties is of great interest for environmental analysis and certain industrial applications. Photo-thermophoresis is an optothermal effect, which occurs when aerosol particles are illuminated by intense light. Locally inhomogeneous heating, resulting in locally increased impingement rates of the gas molecules, generates driving forces. These photophoretic forces can move fine particles either towards or away from the light source. We employ this effect for characterization and separation according to optical and thermal properties of aerosols. We hope to establish this new approach as a helpful supplement to the existing separation methods based on electrical, thermal or flow field forces.