Light-induced thermal convection for size-based microparticle sorting

Separating and sorting of micrometer-sized particles in liquids are important subjects in current analytical chemistry, colloidal chemistry, environmental chemistry, and biological technology. In this paper, we propose and demonstrate a microparticle separating and sorting method based on light-induced thermal convection (LITC). The thermal convection generated as a result of frequency-dependent absorption of optical energy plays an important role in microparticle trapping and manipulation. By using the LITC, we can separate and sort microparticles of different sizes. Manipulation of microparticle sorting is noncontact, which contributes to keeping the natural characteristics of the microparticles. In addition, compared with traditional sorting methods, the microparticle sorting method based on the LITC effect is much easier to implement and convenient to manipulate. This possibility adds a light-induced thermal convection effect as an additional degree of freedom to microparticle separating and sorting.