33
Single-cell capture positioning simulation
After single-cell capture, the cell is transferred to the electrode chamber using back ow, and the
location of the cell in the chamber can be determined in two ways. e rst method uses visual
feedback to observe the position of the cell in real time, and stops the micropump immediately
when the cell moves into the chamber. However, this method has delay time and the cell easily
ows out of the electrode chamber. e second method uses the DEP force to balance the stokes
force. When back ow pushes the trap cell into the electrode chamber, an electrical signal is applied
to the two thick electrodes on the right side, which creates a DEP force between the two electrodes.
Figure 2.12(a) is a simulation of the electric eld strength (Vp-p = 10 V, f = 100 kHz). Figure
2.12(b) shows the distribution of DEP forces along the A-A cutline at dierent voltage amplitudes.
Assuming cell ow rate 40 μm/s, the stokes force is about 24 pN. It is possible to estimate the po-
sition at which the DEP force equal to stokes force. e larger the voltage amplitude, the more the
balance position is to the left. For example, when the voltage amplitude is 10 V, the balance position
of the cell is approximately at the center of the chamber.
100
50
0
-50
-100 100
×10
14
5
4
3
2
1
0
0
-100 1000
A-A Cutline (µm)
75
50
25
0
10 V
5 V
2 V
F
DEP
(pN)
(µm)
(µm)
E
2
(V
2
/m
3
)
Figure 2.12: Simulation results of DEP force: (a) simulation of electric eld strength; and (b) the dis-
tribution of DEP force on A-A cutline.
3D rotational electric eld simulation
Horizontal rotation
Applying the same amplitude and frequency electrical signals (Vp-p = 10 V, f = 1 MHz) with a
phase shift of 90° on the four C-PDMS thick electrodes can generate a horizontally rotational elec-
tric eld in the chamber, causing the cell to do in-plane rotation. Figure 2.13 shows the electric eld
distribution simulation of the electrode chamber. Figure 2.13(a) shows that the electric eld in the
chamber rotates clockwise in one signal period. Figure 2.13(b) shows the electric eld in the cham-
ber rotates counterclockwise in one signal period once reversing the signals to the four electrodes.
2.3 THICKELECTRODE MULTIELECTRODE CHIP DESIGN