44
2. THICK-ELECTRODE DEP FOR SINGLE-CELL 3D ROTATION
After exiting the electrode chamber, the cell can also rotate in the gap between the thick
electrodes and the bottom electrode. If the cell is in a conical region (as shown by the dashed boxed
area in Figure 2.25), it will make out-of-plane rotation about the axis perpendicular to the surface
of the thick electrodes. Figure 2.27 shows that one HeLa cell adsorbed on the electrode surface
under pDEP force (Vp-p = 6 V, f = 2 MHz) and doing out-of-plane rotation about the axis per-
pendicular to the electrode surface.
t=0 s
10 µm
t=0.2 s t=0.4 s t=0.6 s
Figure 2.27: Bottom electrode edge cone area cell rotation state.
After escaping from the conical zone, between the bottom electrode and the thick electrode
(as shown in Figure 2.25), the cells will resume rotation about the X-axis. ere would be two ro-
tation modes, depending on pDEP or nDEP signals applied. Under pDEP, the cell is adsorbed on
the surface of the thick electrode and rotate about the X-axis. Figure 2.28(a) is the force model of
single cell under pDEP force. Figure 2.28(b) shows that a HeLa cell adsorbed on the surface of the
electrode (Vp-p = 6 V, f = 1 MHz) and rotating about the X-axis at speed of ~ 120°/s. Switching
the phase shift sequence of the electrode signals, the cell rotation direction was switched to reverse
rotation about the X-axis.
80
60
40
20
0
3
2.5
2
1.5
1
0.5
×10
5
Surface: Electric Field (V/m)
-100 -50 0
Figure 2.28: e rotation of cells between the bottom electrode and the thick electrode under pDEP
force: (a) simulated force analysis; and (b) HeLa cells rotation around the X-axis under pDEP force.