**- ****Separation of ellipsoidal particles with the initial
inclination angle of ***¥è*_{3}=¥ð/2

**
**

¡¤ **For the ellipsoidal
particle aligned with the laser beam axis (***¥è*_{3}=¥ð/2),
the migration distance decreased as the aspect ratio decreased, and the
ellipsoidal particles were found to be separable according to the aspect ratio
in a COPS system.

¡¤ **The migration distance
remained constant for a given ***S*
number, even if its components differed, as in the case of a rigid spherical
particle.** **

**Trajectories of the
ellipsoidal particles with an initial inclination angle of ***¥è*_{3}=¥ð/2 and different aspect ratios.

**(a) Inclination angle of
ellipsoidal particles with an initial inclination angle of ***¥è*_{3}=¥ð/2 as a function of the streamwise position; the
instantaneous positions and the distributions of the optical force on the
surfaces of the ellipsoidal particles with an initial inclination angle of *¥è*_{3}=¥ð/2 near the laser beam
axis: (b) *b*/*a*=0.9; (c) *b*/*a*=0.5; (d) *b*/*a*=0.3.

**The migration distances
of ellipsoidal particles with an initial inclination angle of ***¥è*_{3}=¥ð/2 as a function of the *S* number for either a fixed fluid
velocity or a fixed laser beam power. The analytical result was included to
compare with numerical results for the spherical particle.

**- ****Effects of the initial
inclination angle and the ***S* number on
the migration distance

¡¤ **The migration distance
depended on the initial inclination angle, even for a given ellipsoidal
particle shape. The effect of the rotation was increased as the ***S* number increased.

¡¤ **The migration distance
of the ellipsoids initially rotated about the ***x*- axis with *¥è*_{3}=0
was not significantly varied because the optical force induced by the
inclination acted along the *z*- axis. To
achieve the effective separation of ellipsoidal particles according to the
aspect ratio, the rotation about the axis along the spanwise direction should
be suppressed.

¡¤ **The ***S*_{c} number was introduced by including the effect of
aspect ratio, which could be used to predict the migration distance for
ellipsoidal particles.

**The migration distances
of ellipsoidal particles with different aspect ratios as a function of the
initial inclination angle ***¥è*_{3}:
(a) *S*=4; (b) *S*=6; (c) *S*=8; (d) *S*=10.