Optical separation of ellipsoidal particles in a uniform flow

Abstract

The behavior of an ellipsoidal particle subjected to a vertical optical force by a loosely focused laser beam in a uniform flow was studied numerically. The fluid flow and the particle motion were separately solved and coupled using the penalty immersed boundary method, and the optical force was calculated using the dynamic ray tracing method. The optical force and optically induced torque on the ellipsoidal particle varied according to the aspect ratio and initial inclination angle. The ellipsoidal particle, whose major axis was initially aligned with the laser beam axis, was more migrated as the aspect ratio increased. The migration distance also depended on the initial inclination angle, even for a given ellipsoidal particle shape. As the laser beam power increased and the flow velocity decreased, the effect of the initial inclination angle increased. The ellipsoidal particles with different aspect ratios could be effectively separated if the rotation along the spanwise direction was suppressed. Moreover, the migration distance could be predicted analytically by introducing a new dimensionless number Sc to represent the ratio of the optical force to the viscous force for the ellipsoidal particles.

Anomalous transversal motion of spheroidal microparticles driven by radiation pressure and torque

“…[11] and references therein. Here we point out the results on the theory of optical forces acting on an ellipsoid [12] and a spheroid [13], studies of non-conservative dynamics of aspheric particles [14,15], optical sorting of aspheric particles [16,17], oscillations of elliptical particles [18], application of Laguerre-Gaussian beams [11], trapping and torsion of Rayleigh spheroids [7], as well as works on levitation [19], rotation [20] and reorientation [21] of such particles. Here we focus on spheroidal dielectric micropaticles subject to radiation forces induced by a plane linearly polarized wave.…”

Anomalous transversal motion of spheroidal microparticles driven by radiation pressure and torque

“…[11] and references therein. Here we point out the results on the theory of optical forces acting on an ellipsoid [12] and a spheroid [13], studies of non-conservative dynamics of aspheric particles [14,15], optical sorting of aspheric particles [16,17], oscillations of elliptical particles [18], application of Laguerre-Gaussian beams [11], trapping and torsion of Rayleigh spheroids [7], as well as works on levitation [19], rotation [20] and reorientation [21] of such particles. Here we focus on spheroidal dielectric micropaticles subject to radiation forces induced by a plane linearly polarized wave.…”

Recent trends and progress in the immersed boundary method

“…1,60 Afterwards, the original IBM and its developed versions have been extensively used in heart and blood flows. 61–68 At Stokes and low Reynolds number regimes, the IBM has been extensively used to cell/particulate flows, 13,17,46,69–84 cilia 85–87 and microswimmers. 88–94 For moderate Reynolds number flows, the IBM has been applied to study filament/flag flapping, 9,11,24,27,37,95–108 insect flying and fish swimming, 11,15,24,25,44,109…”

“…1,60 Afterwards, the original IBM and its developed versions have been extensively used in heart and blood flows. [61][62][63][64][65][66][67][68] At Stokes and low Reynolds number regimes, the IBM has been extensively used to cell/particulate flows, 13,17,46,[69][70][71][72][73][74][75][76][77][78][79][80][81][82][83][84] cilia [85][86][87] and microswimmers. [88][89][90][91][92][93][94] For moderate Reynolds number flows, the IBM has been applied to study filament/flag flapping, 9,11,24,27,37,[95][96][97][98][99]…”