Theoretical development of in situ optical particle separator: cross-type optical chromatography

Abstract

An in situ separation system, cross-type optical chromatography, is developed theoretically, and an analytic solution of the retention distance is derived. Particle trajectories in the cross-type optical chromatography are calculated for various sizes and materials of the particles and for flow velocities. Further, cross-type optical chromatography assisted by a particle beam generation system is designed.

Nondimensional analysis of particle behavior during cross-type optical particle separation

“…In particular, crosstype optical particle separation, as illustrated in Fig. 1, is well established theoretically and experimentally [15][16][17][18]. In cross-type optical particle separation, a laser beam propagates in a direction perpendicular to that of the stream of particles, and the resulting scattering force, which acts on the particles in the direction of laser beam propagation, diverts the particles.…”

“…With the development of microfabrication techniques, various methods of particle separation have been developed, such as dielectrophoretic [4,5], magnetophoretic [6,7], hydrophoretic [8,9], and optical separation methods [10][11][12][13][14][15][16][17][18]. Optical particle separation has some advantages over the other methods: relatively simple structures can be used, resulting in easy to control separation characteristics, and pre-and posttreatments of the medium or separated particles are not required.…”

“…Due to the dependence of the scattering force on the properties of the particles, the particles are separated by their passage through the laser beam. Kim et al [15] first proposed the cross-type optical particle separation method and analyzed the behavior of particles during the separation process. They also derived an analytical expression for the retention distance that can be used to estimate the maximum displacement of particles after their passage through the laser beam.…”

“…In the present study we attempted to generalize this previous theoretical study [15] by ensuring that the governing equations for particle motion during the cross-type optical particle separation are nondimensional. This nondimensional analysis accounts for the gradient force, which has been ignored by previous studies of cross-type optical particle separation [15].…”

“…This nondimensional analysis accounts for the gradient force, which has been ignored by previous studies of cross-type optical particle separation [15]. Since the most important external forces exerted on particles during optical particle separation are the viscous drag force and the optical force, the ratio of these two forces can provide insight into particle behavior.…”