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Numerical and experimental study on the development of electric sensor as for measurement of red blood cell deformability in microchannels.

Tatsumi K, Katsumoto Y, Fujiwara R, Nakabe K - Sensors (Basel) (2012)

Bottom Line: Then, a microsensor was designed and fabricated on the basis of the numerical results.Resistance measurement was carried out using samples of normal RBCs and rigidified (Ca(2+)-A23186 treated) RBCs.Visualization measurement of the cells' behavior was carried out using a high-speed camera, and the results were compared with those obtained above to evaluate the performance of the sensor.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering and Science, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan. tatsumi@me.kyoto-u.ac.jp

ABSTRACT
A microsensor that can continuously measure the deformability of a single red blood cell (RBC) in its microchannels using microelectrodes is described in this paper. The time series of the electric resistance is measured using an AC current vs. voltage method as the RBC passes between counter-electrode-type micro-membrane sensors attached to the bottom wall of the microchannel. The RBC is deformed by the shear flow created in the microchannel; the degree of deformation depends on the elastic modulus of the RBC. The resistance distribution, which is unique to the shape of the RBC, is analyzed to obtain the deformability of each cell. First, a numerical simulation of the electric field around the electrodes and RBC is carried out to evaluate the influences of the RBC height position, channel height, distance between the electrodes, electrode width, and RBC shape on the sensor sensitivity. Then, a microsensor was designed and fabricated on the basis of the numerical results. Resistance measurement was carried out using samples of normal RBCs and rigidified (Ca(2+)-A23186 treated) RBCs. Visualization measurement of the cells' behavior was carried out using a high-speed camera, and the results were compared with those obtained above to evaluate the performance of the sensor.

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(a) Schematic views of the proposed method for measuring the RBC deformability; (b) equivalent circuit of the region between the electrodes; (c) equivalent model of a cell considered as a sphere with uniform complex permittivity.
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f1-sensors-12-10566: (a) Schematic views of the proposed method for measuring the RBC deformability; (b) equivalent circuit of the region between the electrodes; (c) equivalent model of a cell considered as a sphere with uniform complex permittivity.

Mentions: The microsensor proposed in this study measures the electric resistance of RBCs as they pass between its electrodes. Figure 1 shows a schematic of the basic elements of the proposed sensor. As shown in Figure 1(a), micro-membrane-type electrodes are attached to the bottom wall of the microchannel. An RBC is suspended in the flow and is controlled such that it passes between the electrodes. An equivalent circuit that represents the electric characteristics of the region between the electrodes is shown in Figure 1(b). The circuit consists of the cell, a solution, and an electric double layer formed on the surface of the electrodes. The cell is composed of the cytoplasm and cytomembrane. The resistance of the cytomembrane is much larger than that of the solution and is less than 1 × 10–6 S/m. This value is less than that of the cytoplasm and normal saline solution; thus, the cytomembrane acts as an insulating material. In this case, the resistance obtained from the impedance measured by the electrodes will be influenced mainly by two factors: that are, the resistance of the membrane and how the current flux in the electric field is interruption by the cell. This means that the measured resistance will reflect the size, height position, and shape of the cell. In addition to this, when the RBC passes the electrodes, the resistance will increase as it approaches the center of the electrodes and then decreases as it moves away; namely, the resistance will show a time-series distribution similar to the one shown by the graph in Figure 1(a). The previously mentioned parameters are considered to not only influence the resistance itself but also this time-series distribution of the resistance.


Numerical and experimental study on the development of electric sensor as for measurement of red blood cell deformability in microchannels.

Tatsumi K, Katsumoto Y, Fujiwara R, Nakabe K - Sensors (Basel) (2012)

(a) Schematic views of the proposed method for measuring the RBC deformability; (b) equivalent circuit of the region between the electrodes; (c) equivalent model of a cell considered as a sphere with uniform complex permittivity.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3472844&req=5

f1-sensors-12-10566: (a) Schematic views of the proposed method for measuring the RBC deformability; (b) equivalent circuit of the region between the electrodes; (c) equivalent model of a cell considered as a sphere with uniform complex permittivity.
Mentions: The microsensor proposed in this study measures the electric resistance of RBCs as they pass between its electrodes. Figure 1 shows a schematic of the basic elements of the proposed sensor. As shown in Figure 1(a), micro-membrane-type electrodes are attached to the bottom wall of the microchannel. An RBC is suspended in the flow and is controlled such that it passes between the electrodes. An equivalent circuit that represents the electric characteristics of the region between the electrodes is shown in Figure 1(b). The circuit consists of the cell, a solution, and an electric double layer formed on the surface of the electrodes. The cell is composed of the cytoplasm and cytomembrane. The resistance of the cytomembrane is much larger than that of the solution and is less than 1 × 10–6 S/m. This value is less than that of the cytoplasm and normal saline solution; thus, the cytomembrane acts as an insulating material. In this case, the resistance obtained from the impedance measured by the electrodes will be influenced mainly by two factors: that are, the resistance of the membrane and how the current flux in the electric field is interruption by the cell. This means that the measured resistance will reflect the size, height position, and shape of the cell. In addition to this, when the RBC passes the electrodes, the resistance will increase as it approaches the center of the electrodes and then decreases as it moves away; namely, the resistance will show a time-series distribution similar to the one shown by the graph in Figure 1(a). The previously mentioned parameters are considered to not only influence the resistance itself but also this time-series distribution of the resistance.

Bottom Line: Then, a microsensor was designed and fabricated on the basis of the numerical results.Resistance measurement was carried out using samples of normal RBCs and rigidified (Ca(2+)-A23186 treated) RBCs.Visualization measurement of the cells' behavior was carried out using a high-speed camera, and the results were compared with those obtained above to evaluate the performance of the sensor.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering and Science, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan. tatsumi@me.kyoto-u.ac.jp

ABSTRACT
A microsensor that can continuously measure the deformability of a single red blood cell (RBC) in its microchannels using microelectrodes is described in this paper. The time series of the electric resistance is measured using an AC current vs. voltage method as the RBC passes between counter-electrode-type micro-membrane sensors attached to the bottom wall of the microchannel. The RBC is deformed by the shear flow created in the microchannel; the degree of deformation depends on the elastic modulus of the RBC. The resistance distribution, which is unique to the shape of the RBC, is analyzed to obtain the deformability of each cell. First, a numerical simulation of the electric field around the electrodes and RBC is carried out to evaluate the influences of the RBC height position, channel height, distance between the electrodes, electrode width, and RBC shape on the sensor sensitivity. Then, a microsensor was designed and fabricated on the basis of the numerical results. Resistance measurement was carried out using samples of normal RBCs and rigidified (Ca(2+)-A23186 treated) RBCs. Visualization measurement of the cells' behavior was carried out using a high-speed camera, and the results were compared with those obtained above to evaluate the performance of the sensor.

Show MeSH