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2. THICK-ELECTRODE DEP FOR SINGLE-CELL 3D ROTATION
2.8.2 ANALYSIS OF RECONSTRUCTION RESULTS
From the reconstructed 3D cell morphology, several physical features of the cell, such as surface
area, volume, roughness, and ellipticity can be calculated. e alpha-shape algorithm builds a 3D
model by concatenating point clouds into triangular networks. e calculation of the surface area
is obtained by adding the areas of all the triangular meshes. e volume is calculated by using tri-
angular grid projection methods. e roughness is calculated by normalizing the constructed cell
model to the standard sphere to determine the corresponding standard deviation. Ellipticity is the
ratio of the long axis to the short axis of a 3D model.
e surface area and volume of 8 HeLa cells and 8 B lymphocytes were calculated, as shown
in Figure 2.38(a). e average surface area of HeLa cells was 312.16 µm
2
, and the average value of
B lymphocytes was 180.25 µm
2
. e average volume of HeLa cells was 666.86 fL, and the average
value of B lymphocytes was 212.03 fL.
1,000
800
600
400
200
0
0.3
0.25
0.2
100 200 300 400
Surface (µm
2
)
1 1.05 1.1 1.15
1.2
Ellipticity
Vo lume (fl)
Roughness
HeLa
B-lymphocytes
HeLa
B-lymphocytes
(a) (b)
Figure 2.38: (a) Surface area and volume distribution of HeLa cells and B cells; (b) Ellipsoid ratio and
surface roughness distribution of HeLa cells and B cells.
e average ellipticity of B lymphocytes was calculated to be 1.029, which was slightly lower
than that of HeLa cells (average of 1.084), as shown in Figure 2.38(b). ese values indicate that
the two cells have similar ellipticities but are not perfectly spherical. On the other hand, the rough-
ness of the cell surface can be calculated from the 3D morphology, and the average roughness of the
surface of the B lymphocyte is 0.264 and slightly larger than that of HeLa cells (0.231).
2.9 SUMMARY
is chapter introduced the application of multi-electrode structure of thick-electrode DEP, and
presented a single-cell 3D rotation microuidic device of “Armillary Sphere” type, which is success-
fully demonstrated for electrical property measurement of single cell and 3D image reconstruction.
Control of 3D rotation is achieved by adjusting signal parameters, including rotation direction,
55
speed, and rotation mode. e thick-electrode DEP chip has the advantages of overcoming the
limitations of 2D planar electrodes and providing a stable distribution of electric eld. In the ex-
periment, the cell area-specic membrane capacitance and cytoplasmic conductivity of cells were
extracted by tting the rotation spectrum. e electrical properties of four types of mammalian
cells were measured and analyzed. Based on out-of-plane rotation of cells, the 3D morphology of
single cells is reconstructed by image processing, and the geometrical features such as surface area,
volume, roughness, and ellipticity are calculated according to the reconstructed 3D morphology.
Based on the single-cell 3D rotation chip, it is easy to combine with other techniques to achieve
multi-parameter measurements of single cells.
2.9 SUMMARY
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