Biomedical Engineering Reference
In-Depth Information
Fig. 1.25
Simulation framework. The spheres of the nanotube denote the possible forced-atoms
and
d
is the
z
coordinate of the possible forced-atom (reprinted from [
131
]. Copyright 2011
American Physical Society)
Fig. 1.26
The water flux
across the carbon nanotube
for different deformation
positions
d
(reprinted from
[
131
]. Copyright 2011
American Physical Society)
Our first observation is that the net water flux is sensitive to the position of the
deformation (see Fig.
1.26
). For the unperturbed CNT, the net water flux is about
14.8 ns
1
. The W-type profile shows that the water flux peaks at 12.5 ns
1
when the
deformation exists in the middle region (
d
D
0 A) of the SWNT. And it decreases
sharply as long as the deformation position moves away from the middle region.
Note that if the deformation position moves from
d
D
0
˚
Ato
d
D
4.9
˚
A(
2.5 A
distance from the end of the nanotube), the net water flux reaches the minimum. One
readily sees that the net water flux decreases dramatically when the deformation
position occurs near the end of the SWNT. The flux for
d
D
4.9 A falls to only
approximately one quarter of the flux for
d
D
0 A. In other words, the nozzle effect
is very important for water permeation. Furthermore, simulation results indicate that
the W-type profile is not fully symmetrical, even though the deformation positions
are symmetrical at approximately
d
D
0 A (see Figs.
1.25
and
1.26
). For example,
the net water flux for
d
D
4.9
˚
A(3.5ns
1
) is obviously smaller than that for
d
D
4.9
˚
A(5.1ns
1
). Meanwhile, the net water fluxes for
d
D
7.4 and 7.4
˚
Aalso
exhibit similar behavior and their values are 6.4 and 7.0 ns
1
, respectively.
