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Geometric parameters optimization of planar interdigitated electrodes for bioimpedance spectroscopy

M. Ibrahim
M. Ibrahim
, 
J. Claudel
J. Claudel
, 
D. Kourtiche
D. Kourtiche
 e 
M. Nadi
M. Nadi
   | 01 mar 2013
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Article Category: Articles
Pubblicato online: 01 mar 2013
Pagine: 13 - 22
Ricevuto: 04 giu 2012
DOI: https://doi.org/10.5617/jeb.304
Parole chiave
© 2013 M. Ibrahim, J. Claudel, D. Kourtiche and M. Nadi, published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Fig. 1

(a) Configuration of interdigitated impedance cell structure and (b) its adapted equivalent circuit model. CCell and RSol models the dielectric properties of the medium under testing, and CDL models the properties of the double layer phenomena.
(a) Configuration of interdigitated impedance cell structure and (b) its adapted equivalent circuit model. CCell and RSol models the dielectric properties of the medium under testing, and CDL models the properties of the double layer phenomena.

Fig. 2

Interdigitated sensor structure of 4 electrodes. The dimensional parameters L, W, and S are finger length, finger width and finger spacing, respectively.
Interdigitated sensor structure of 4 electrodes. The dimensional parameters L, W, and S are finger length, finger width and finger spacing, respectively.

Fig. 3

Diagram of total impedance vs. frequency behavior. Three cases can be distinguished: For low frequencies (before FLow), the total impedance only depends on the double layer capacitance CDL. In the intermediate range the impedance reaches a plateau, which depends on the solution resistance RSol. For high frequencies (after FHi), the impedance depends on the cell capacitance CCell.
Diagram of total impedance vs. frequency behavior. Three cases can be distinguished: For low frequencies (before FLow), the total impedance only depends on the double layer capacitance CDL. In the intermediate range the impedance reaches a plateau, which depends on the solution resistance RSol. For high frequencies (after FHi), the impedance depends on the cell capacitance CCell.

Fig. 4

Analytical optimization of the dimensional parameters that to say width W and spacing S. The geometrical term Y (a) is a function of S and W, where the ratio a is equal to S/W. Its value of optimization is 0.66.
Analytical optimization of the dimensional parameters that to say width W and spacing S. The geometrical term Y (a) is a function of S and W, where the ratio a is equal to S/W. Its value of optimization is 0.66.

Fig. 5

The geometrical cell constant KCell by varying the number N of electrodes in the optimization case W = S ⋅ 3/2. The finger length L is 1000 μm.
The geometrical cell constant KCell by varying the number N of electrodes in the optimization case W = S ⋅ 3/2. The finger length L is 1000 μm.

Fig. 6

Top view of a structural model of 8 electrodes in a planar interdigitated array. The size is 1000×1000 μm, the width W and finger spacing S of the electrodes in this figure are 79 μm and 52 μm, respectively.
Top view of a structural model of 8 electrodes in a planar interdigitated array. The size is 1000×1000 μm, the width W and finger spacing S of the electrodes in this figure are 79 μm and 52 μm, respectively.

Fig. 7

3D view of structural model of 4 electrodes type planar interdigitated electrode array (layer 2) loaded by the full medium, which contains the double layer DL (layer 3) and blood medium (layer 4). The entire system is located on a glass substrate (layer 1). The width W and spacing S of electrodes in this figure is 167 μm and 111 μm, respectively. The size of full medium is 1000×1000×500 μm.
3D view of structural model of 4 electrodes type planar interdigitated electrode array (layer 2) loaded by the full medium, which contains the double layer DL (layer 3) and blood medium (layer 4). The entire system is located on a glass substrate (layer 1). The width W and spacing S of electrodes in this figure is 167 μm and 111 μm, respectively. The size of full medium is 1000×1000×500 μm.

Fig. 8

3D view of a structural model meshing of 4 electrodes type planar interdigitated array, covered by the full blood medium. The mesh type is Manhattan bricks and the element size is 5 μm.
3D view of a structural model meshing of 4 electrodes type planar interdigitated array, covered by the full blood medium. The mesh type is Manhattan bricks and the element size is 5 μm.

Fig.9

Simulated electrical impedance for a full blood medium deposited on the interdigitated structure of 16 electrodes. The medium is modeled with and without interface double layer DL.
Simulated electrical impedance for a full blood medium deposited on the interdigitated structure of 16 electrodes. The medium is modeled with and without interface double layer DL.

Fig. 10

Simulated response of interdigital biosensor with 16 electrodes, by changing the permittivity of the blood medium (layer 4). Electrical impedance simulated for two different permittivities, 80 and 5200, respectively.
Simulated response of interdigital biosensor with 16 electrodes, by changing the permittivity of the blood medium (layer 4). Electrical impedance simulated for two different permittivities, 80 and 5200, respectively.

Fig. 11

Simulated response of interdigital biosensor with 16 electrodes, by changing the conductivity of the blood medium (layer 4). Electrical impedance simulated for two different conductivities, 0.7 S/m and 9 S/m, respectively.
Simulated response of interdigital biosensor with 16 electrodes, by changing the conductivity of the blood medium (layer 4). Electrical impedance simulated for two different conductivities, 0.7 S/m and 9 S/m, respectively.

Fig. 12a

Behavior of simulated electrical impedance for the blood medium by varying the cell constant of the sensor with changing the ratio between width of electrodes and gap, while leaving the same contact area of sensor 1000 × 1000 microns by N = 8 electrodes.
Behavior of simulated electrical impedance for the blood medium by varying the cell constant of the sensor with changing the ratio between width of electrodes and gap, while leaving the same contact area of sensor 1000 × 1000 microns by N = 8 electrodes.

Fig. 12b

Behavior of corresponding electrical phase by varying the ratio between width of electrodes and gap.
Behavior of corresponding electrical phase by varying the ratio between width of electrodes and gap.

Fig. 13a

Behavior of simulated electrical Bioimpedance for the blood medium by varying the cell constant of the sensor with changing the number of electrodes N, while leaving the same contact area of sensor 1000 × 1000 microns.
Behavior of simulated electrical Bioimpedance for the blood medium by varying the cell constant of the sensor with changing the number of electrodes N, while leaving the same contact area of sensor 1000 × 1000 microns.

Fig. 13b

Behavior of corresponding electrical phase by varying the number of electrodes N.
Behavior of corresponding electrical phase by varying the number of electrodes N.

Fig. 14

Difference sensitivity percentage of simulated electrical Bioimpedance for the blood medium relative to the 2 electrodes type sensor by varying the number of electrodes N, while leaving the same contact area of sensor 1000 × 1000 microns. The sensitivity is calculated by (Zi-Z2)/ (Z2·volume), i is the number of electrodes.
Difference sensitivity percentage of simulated electrical Bioimpedance for the blood medium relative to the 2 electrodes type sensor by varying the number of electrodes N, while leaving the same contact area of sensor 1000 × 1000 microns. The sensitivity is calculated by (Zi-Z2)/ (Z2·volume), i is the number of electrodes.

Representative table of the variation of cut off frequency FLow depending on the geometry.

FLow (Hz)ΔFLow (Hz)change Relative %
S/W = 0.667·10300
S/W = 0.110·1033·10343
S/W = 520·10313·103186
eISSN:
1891-5469
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Inglese
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Argomenti della rivista:
Engineering, Bioengineering and Biomedical Engineering, Biomedical Electronics, Life Sciences, Biophysics, Medicine, Biomedical Engineering, Physics, Spectroscopy and Metrology
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