Inertial Migration of Cancer Cells in a Microfluidic Device - Bioanalysis Advanced Materials Methods and Devices - page 23

When Re p ¼ 0.16, the migration of rigid spheres was not clearly observed

(Fig. 2.5a ). When Re p ¼ 0.31 and 0.62, inertial migration of particles toward

equilibrium positions was observed. As Re p increased, the peak of the probability
density became larger. The migration of rigid spheres was not significant when
L ¼

0.5 or 1.0 cm, whereas migration was apparent when L

¼

1.5 or 2.0 cm
(Fig. 2.5b ). These results indicate that the migration of rigid spheres occurs due to
an inertial effect and that large values of Re p and L are necessary to achieve strong
migration of the spheres. These findings were consistent with those of previous
studies [ 1 , 5 , 16 ]. For Re p ¼ 0.16, the migration length ( L m )was1.3cm.For
L ¼ 0.5 or 1.0 cm, the channel length was shorter than L m ( L < L m ). When

L L m ). Our experimental

results demonstrate that the migration length ( L m ) calculated using ( 2.1 )correctly
describes the migration of rigid spheres.

¼ 1.5 or 2.0 cm, the channels had adequate length ( L >

2.6 Motion of Cancer Cells in a Microchannel

Next, the migration of cancer cells was compared with that of rigid spheres.
Figure 2.6 shows the probability density of the width position of cancer cells
upstream and downstream, with Re p ¼ 0.62. Like the rigid spheres, cancer cells

displayed a relatively homogeneous probability density upstream, whereas a large
peak, around 115 m from the wall), was observed

downstream. Compared with the rigid spheres, the maximum probability density of
the cancer cells was not as high and the probability density function slightly blunter.
The effects of Re p and L on the probability density of cancer cells are shown
in Fig. 2.7 . The peak in the probability density increased with Re p (Fig. 2.7a ).

m m from the center (i.e., 110 m

Fig. 2.6 Probability density
of the width position of
cancer cells at the upstream
and the downstream of the
test section with Re p 0.62.

Error bars indicate standard
deviations. The sidewall is
located 225

¼

m m from the

center [ 22 ]