Biomedical Engineering Reference
In-Depth Information
data [119]. As presented in Section 3.3.1, because the microfl uidic channel is
placed near the edge of a permanent magnet (NdFeB35; 50 mm
10 mm;
Magtopia, Korea) and the nickel microstructures were positioned between the
permanent magnet and microfl uidic channel, it was diffi cult to estimate the mag-
netic fl ux density around the microchannels using a numerical equation. Fortu-
nately, the width of the microchannel is narrow enough (100
×
25 mm
×
m) to make a rough
assumption that d
B
/d
x
has a linear relationship with the cross-sectional distance
of the microchannel. Therefore, Equation 3.8 can be used to estimate the magne-
tophoretic velocity,
V
x
(
t
,
x
).
In order to compare the numerical estimation with the experimental results, the
magnetophoretic and isomagnetophoretic analysis was assessed in the microchan-
nels. In Figure 3.22a, the lateral positions (18.52
μ
m,
n
= 802, respectively) of the PS and PMMA particles are overlapped so that the
two types of material cannot be distinguished one from another. A broad deviation
of the lateral position (PMMA and BS; 52.13
±
1.58
μ
m,
n
= 247; 18.20
±
6.61
μ
m,
n
= 1097) also results from
a large size variation of the particles, its deviation being proportional to the size
variation as described in Equation 3.7. Isomagnetophoresis, however, in Figure
3.22b exhibits the large difference of the lateral position of PS (17.68
±
5.33
μ
±
1.62
μ
m.
n
= 576) and PMMA (30.44
m,
n
= 406) particles providing the enhanced
discernible capability. Furthermore, it remarkably reduces the deviation width of
the particle position for all types of particle because the isomagnetophoretic migra-
tion is attenuated by the isopoint of
±
3.48
μ
and the particles stands in the vicinity of
the their isopoint, without regard for the particle size.
By combining the equation stated above, it is possible to predict the particle
traces in conventional magnetophoresis and new IMP. In the analytical model,
the microparticle positions in the microchannel are considered as a point in a
χ
(a)
(b)
Figure 3.22
Measured particle positions of PS, PMMA, and
borosilicate in conventional magnetophoresis (a) and
isomagnetophoresis (b). Subtle difference in magnetic
susceptibility between PS and PMMA was pre- eminently
discriminated in isomagnetophoretic displacement (b).
Reproduced with permission from Ref. [42]; © 2008,
American Chemical Society.
