JP2016067722A - Biomedical electrode and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly detect a biosignal by reducing impedance at low frequencies.SOLUTION: A biomedical electrode 10 is made of a paper-formed sheet 21 including a carbon nano-tube. The paper-formed sheet 21 has a carbon nano-tube of a layer structure. The carbon nano-tube of the layer structure is made by stacking carbon nano-tube aggregates obtained by opening a bundle.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a biomedical electrode using carbon nanotubes and a method for producing the biomedical electrode.

  The biological signal measuring device is a device that measures biological signals such as an electroencephalogram, an electrocardiogram, an electromyogram, and an nystagmus. The biological signal measuring device detects a biological signal from a biological electrode brought into contact with the living body. As a biological electrode, a plate electrode made of silver / silver chloride, a so-called silver plate electrode has been often used. When using a silver plate electrode, first, a paste containing an electrolyte such as physiological saline is applied to a measurement site of a living body, and then the silver plate electrode is brought into contact with the measurement site.

Japanese Patent Laid-Open No. 2001-276111

  For example, in brain surgery, it is desirable for the proper execution of surgery to take a brain image by X-ray CT, MRI or the like while measuring an electroencephalogram with an electroencephalograph. However, artifacts (false images) appear in the CT image due to the silver contained in the silver plate electrode. In addition, since the silver plate electrode is hard, the skin may be irritated when it is worn for a long time. Furthermore, the silver plate electrode is expensive because it uses silver, and it is difficult to dispose of the silver plate electrode.

  For this reason, development of an electrode using a conductive material other than silver has been desired, and an electrode using a carbon material has been devised as one of them. However, biological signals, particularly brain waves, are weak signals having a frequency of 0.5 to 70 Hz. For this reason, when the impedance of the electrode at a low frequency increases, noise increases and the biological signal cannot be sufficiently detected. It was difficult to develop an electrode using a carbon material and having a lower impedance at a lower frequency than a silver plate electrode.

  The present invention solves the above-described problems, can detect a biological signal satisfactorily by reducing impedance at a low frequency, can be used in combination with X-ray CT, and is inexpensive and can be disposable. It aims at providing an electrode and its manufacturing method.

  In order to achieve the above object, the biomedical electrode according to the present invention is characterized by having a papermaking molded sheet containing carbon nanotubes.

The carbon nanotube may have a specific surface area of 50 m ² / g or more and less than 2600 m ² / g.

  The paper-made molded sheet may have a thickness in the range of 100 nm or more and less than 10 mm.

  The papermaking sheet may be produced without using a binder.

  The papermaking sheet may further include a carbon powder dispersed in carbon nanotubes and having a particle diameter of less than 100 nm and subjected to a porous treatment.

  The biomedical electrode may further include a gel layer provided on the surface of the papermaking sheet and serving as a contact surface with the living body.

  The gel layer may be provided on a part of the surface of the papermaking sheet, and a part of the surface of the papermaking sheet may be exposed.

  The biomedical electrode may further include an insulating layer formed around the gel layer and supporting the gel layer.

  The gel layer may be fixed so that a part of the gel layer bites into the papermaking sheet.

  The biomedical electrode may further include a paste layer containing an electrolyte provided between the gel layer and the papermaking sheet.

  The biomedical electrode may further include a lead wire that is laminated on a surface facing the surface on which the gel layer of the papermaking molded sheet is provided, and is larger than the papermaking molded sheet.

  The papermaking sheet may include a carbon nanotube having a layered structure.

  The layered carbon nanotube may be a laminate of carbon nanotube aggregates obtained by opening a bundle.

  The carbon nanotube aggregate may have a thickness of 0.3 μm to 10 μm and a width of 0.1 μm to 500 μm.

  In addition, according to the present invention, there is provided a method for producing a biomedical electrode having a papermaking sheet containing carbon nanotubes, a step of mixing a carbon nanotube and a solvent to prepare a carbon nanotube dispersion solution, and the carbon solution from the dispersion solution. Extracting nanotubes and forming them into a sheet.

  The carbon nanotubes may be extracted from the dispersion solution by suction filtration of the dispersion solution using a filter paper.

  After the carbon nanotubes and the solvent are mixed, the carbon nanotubes may be opened.

  According to the present invention, an electrode having a high density and a large specific surface area can be obtained by using a paper-molded sheet containing carbon nanotubes for a living body electrode, impedance can be reduced at a low frequency, and a living body signal can be improved. Can be detected. In addition, since carbon nanotubes are used, it can be used in combination with X-ray CT, can be inexpensive and disposable, and the hygiene can be improved.

It is sectional drawing which shows the structure of the biomedical electrode of this embodiment. It is a flowchart which shows the manufacturing method of the electrode of this embodiment. (A) is sectional drawing which shows the structure of the biological electrode in an Example and a comparative example, (b) is the figure which bonded together the biological electrode through the separator. 2 is an SEM image (× 5k) showing a fracture surface of the electrode of Example 1. FIG. It is a SEM image (x5k) which shows the torn surface of the electrode of Example 2. FIG. It is a SEM image (x5k) which shows the torn surface of the electrode of Example 3. It is a SEM image (x5k) which shows the fracture surface of the electrode of Example 4. It is a graph which shows the impedance of Examples 1-4 and Comparative Examples 2 and 3. It is a graph which shows the impedance of Example 1 and Example 3. FIG. It is a graph which shows the impedance of Example 2 and Example 4. FIG. It is a graph which shows the impedance of Examples 5-8 and the comparative example 2. FIG. It is sectional drawing which shows the structure of the biomedical electrode which concerns on other embodiment. It is sectional drawing which shows the structure of the biomedical electrode which concerns on other embodiment. It is sectional drawing which shows the structure of the biomedical electrode which concerns on other embodiment. It is sectional drawing which shows the structure of the biomedical electrode which concerns on other embodiment.

  Hereinafter, embodiments of the biological electrode and the manufacturing method of the biological electrode will be described.

(1) Biological electrode The biological electrode 10 includes a carbon nanotube sheet (hereinafter also referred to as “CNT sheet”) 21 as an electrode element, and is not limited to a specific structure. It can be set as such a structure.

  1, the adhesive layer 22 and the cover layer 23 are laminated on one surface of the CNT sheet 21, and the gel layer 24 is laminated on the opposite surface. The exposed surface of the gel layer 24 becomes a contact surface with the living body. One end of the lead wire 25 is sandwiched between the CNT sheet 21 and the cover layer 23 and bonded by the adhesive layer 22. The lead wire 25 can be made of, for example, a metal material such as aluminum or stainless steel, carbon fiber, or the like.

  The adhesive layer 22 is for bonding the CNT sheet 21 and the cover layer 23 together. The material of the adhesive layer 22 is preferably a biocompatible material. For example, synthetic resin adhesives such as polyethylene, polyethylene terephthalate, silicon rubber, polyurethane, etc., conductive adhesives in which carbon nanotubes are dispersed in synthetic resin adhesives, or conductive resins having their own conductivity The adhesive layer 22 can be formed by applying an adhesive made of or the like to the CNT sheet 21 or the cover layer 23.

  The cover layer 23 protects the lead wires 25 and reinforces the CNT sheet 21, and an insulating resin sheet is used.

  The gel layer 24 can be composed of, for example, a conductive gel sheet. The conductive gel sheet contains a hydrophilic polymer such as carboxymethyl cellulose, silicon, or polyurethane, and a sodium chloride solution. By using this gel layer as a living body contact surface, adhesion to the living body is improved. Further, the input impedance can be reduced by ionic conduction of the gel layer 24.

  Instead of the gel layer 24, a paste layer containing an electrolyte such as physiological saline may be formed on the opposing surface of the CNT sheet 21. Similar to the gel layer 24, the input impedance can be reduced by the electrolyte of the paste layer.

  The CNT sheet 21 is obtained by molding carbon nanotubes (hereinafter also referred to as “CNT”) into a sheet shape by a papermaking molding process described later. The carbon nanotubes used for the CNT sheet 21 may be long. The long length means a fiber diameter of less than 50 nm, a fiber length of 1 μm or more, preferably 200 μm or more, and an aspect ratio of 100 or more. Long CNTs are obtained by arc discharge method, laser evaporation method, chemical vapor deposition (CVD) method or the like.

  The CNT is not limited to a specific type as long as it is long. For example, single-wall carbon nanotubes (SWCNT) with a single graphene sheet, multi-wall carbon nanotubes (MWCNT) in which two or more graphene sheets are coaxially rounded, and the tube wall forms a multilayer, or a mixture thereof May be used.

The specific surface area of the CNT is 50 m ² / g or more and less than 2600 m ² / g, preferably 100 m ² / g or more and less than 2300 m ² / g, more preferably 200 m ² / g or more and less than 1500 m ² / g. desirable. When the specific surface area is larger than 2600 m ² / g and when the specific surface area is smaller than 50 m ² / g, the impedance increases.

  The thickness of the CNT sheet 21 is preferably in the range of 100 nm or more and less than 10 mm, preferably 500 nm or more and less than 1 mm, more preferably 1 μm or more and less than 500 μm. When the thickness is larger than 10 mm and when the thickness is smaller than 100 nm, the impedance is increased.

  The CNT sheet 21 may have a layered structure on its fracture surface. The layered structure means a state where CNT masses are stacked to form a laminate. By having a layered structure, it is considered that the conductivity is improved by the uniform arrangement in the sheet. In addition, the CNT lump is a bundle formed by opening a bundle by a physical force. The aggregate of CNT is a spherical lump having a central particle diameter of 5 to 10 μm. These spherical aggregates are crushed to form a layered structure. Thereby, the contact area between the aggregates can be increased, and the impedance of the formed CNT sheet can be reduced. Here, “opening” means that a bundle of CNTs firmly bonded by van der Waals force is loosened by physical force.

  The thickness of the aggregate forming the layer is from 0.3 μm to 10 μm, preferably from 0.5 μm to 5 μm, more preferably from 1 μm to 3 μm. The width of the aggregate forming the layer is from 0.1 μm to 500 μm, preferably from 0.5 μm to 200 μm, and more preferably from 1 μm to 100 μm. When this thickness is smaller than 0.3 μm and when the thickness is larger than 10 μm, the impedance increases in any case. Impedance also increases when the width is smaller than 0.1 μm and larger than 500 μm.

  The CNT sheet 21 is preferably composed only of CNTs without mixing a binder such as a resin. In general, the binder needs to be added to reinforce the sheet. In this embodiment, since a sheet is produced by a papermaking molding method described later, sufficient strength can be maintained and a binder can be eliminated. By producing the CNT sheet 21 without using a binder, an increase in resistance due to the binder can be prevented. However, the CNT sheet 21 may be produced by adding a binder as long as it does not inhibit the detection of the biological signal.

  Carbon powder may be mixed into the CNT sheet 21 in order to improve impedance characteristics. The types of carbon powder include natural plant tissues such as palm, synthetic resins such as phenol, activated carbon derived from fossil fuels such as coal, coke, and pitch, ketjen black (hereinafter referred to as KB), and acetylene. Examples thereof include carbon black such as black and channel black, carbon nanohorn, amorphous carbon, natural graphite, artificial graphite, graphitized ketjen black, activated carbon, and mesoporous carbon.

(2) Electrode Manufacturing Method As described above, the CNT sheet 21 is produced by a process of making CNTs by papermaking (papermaking). Specifically, the paper making process includes the following steps as shown in FIG.
Step S01: CNT and a solvent are mixed to prepare a CNT dispersion solution.
Step S02: CNT is extracted from the CNT dispersion solution and molded into a sheet.

Hereinafter, each process is explained in full detail.
[Step S01]
CNT is mixed with a solvent to prepare a dispersion solution of CNT. The method for preparing the dispersion solution is not limited to a specific one, but as an example, the dispersion solution of CNT can be prepared by stirring CNT and a solvent with a general-purpose mixer such as a homogenizer for about 5 minutes. As the solvent, water, alcohols such as methanol and isopropyl alcohol, and the like can be used. You may add the opening process of CNT to the preparation process of the dispersion solution of CNT. The opening process is not limited to a specific method as long as the bundle of CNTs can be loosened. For example, a bundle of entangled CNTs can be loosened by applying a physical force to the CNTs by stirring the CNT dispersion with a ball mill. In addition, jet mixing is also available. The bundled CNTs form aggregates. The aggregate of CNTs is a spherical lump having a center particle diameter of 5 to 10 μm.

[Step S02]
CNTs are extracted from the CNT dispersion prepared in step S01 and molded into a sheet. Although the method for extracting CNTs is not limited to a specific one, for example, a CNT dispersion solution may be suction filtered using a filter paper. As the filter paper, for example, PTFE filter paper can be used. Only CNTs can be extracted on the filter paper by suction filtration. When the extract on the filter paper is dried, the CNT sheet 21 is completed.

  When the fiber opening process is performed in step 01, the completed CNT sheet has a layered structure by performing the suction filtration process in step S02. The following mechanism can be considered as the reason why a layered structure is formed by suction filtration. Aggregates of CNTs in the mixed solution are attracted onto the filter paper by suction filtration. The agglomerate is crushed into a disk shape because the force attracted downward acts even after contacting the filter paper. The disk-like aggregates are deposited so as to be folded to form a layered structure.

  The CNT sheet 21 is cut into a desired shape to form an electrode element, and an adhesive is applied thereon to form an adhesive layer 22. By laminating the cover layer 23 while sandwiching one end of the lead wire 25 on the adhesive layer 22, it can be used as the biological electrode 10.

  When carbon powder is mixed with CNT, in addition to CNT, carbon powder is also mixed with a solvent in step S01. Furthermore, by stirring using a ball mill, jet mixing, ultracentrifugation, or the like, the carbon powder can be subdivided and homogenized at the same time as the CNTs are opened.

Example 1
70 mg of SWCNT (specific surface area 800 m ² / g, fiber length 500 μm, fiber diameter 3 nm) and 30 cc of isopropyl alcohol were stirred for 5 minutes at a rotational speed of 20000 rpm using a homogenizer to prepare a dispersion solution of CNTs. The produced dispersion solution 10 cc was further stirred for 10 minutes using a ball mill to perform the CNT opening process. At this time, the ball diameter was 0.5 mm and the rotation speed was 1000 rpm. Subsequently, the dispersion solution of CNTs was suction filtered using PTFE filter paper (diameter: 35 mm, average pore size 0.2 μm), and the residue on the filter paper was dried at 110 ° C. for 10 minutes with a rotary dryer. A CNT sheet 21 was produced.

(Example 2)
A CNT sheet 21 was produced in the same manner as in Example 1 except that SWCNT was changed to MWCNT (specific surface area 250 m ² / g, fiber length 1.5 μm, fiber diameter 9.5 nm).

(Example 3)
The same material as in Example 1 was used. Without performing the CNT opening process using a ball mill, the dispersion solution of CNT produced by a homogenizer was suction filtered with a filter paper as it was. Other than that, a CNT sheet 21 was produced in the same manner as in Example 1.

Example 4
The same material as in Example 2 was used. Without performing the CNT opening process using a ball mill, the dispersion solution of CNT produced by a homogenizer was suction filtered with a filter paper as it was. Other than that, a CNT sheet 21 was produced in the same manner as in Example 1.

  The thickness of the CNT sheet 21 of Examples 1 to 4 produced by the method described above was about 100 μm. Using these CNT sheets 21, biomedical electrodes 2 shown in FIG. As described above, the biological electrode of the present invention is not limited to a specific structure. If the reduction in impedance at low frequency can be confirmed in the biological electrode 2 shown in FIG. 3, it can be said that the biological electrode having another structure, for example, the biological electrode 10 shown in FIG.

  As shown in FIGS. 3 (a) and 3 (b), the biological electrode 2 is formed by applying an adhesive 6 to one surface of the CNT sheet 21 and attaching a protective insulating tape 7 thereon, to thereby form a disk portion. And punched to have a lead portion. Then, two biomedical electrodes 2 were prepared, the disc portions were bonded together via the separator 4, impregnated with physiological saline, sandwiched between glass plates, and pressurized with clips. The adhesive 6 applied to the CNT sheet 21 is for reinforcing the CNT sheet 21 and facilitating adhesion to the insulating tape 7. The adhesive 6 is not limited to a specific type, but here, a biocompatible adhesive is used. The separator 4 is made of manila paper here, but is not limited to a specific type.

  Using the biomedical electrodes 2 and 2 bonded together, a measurement test was performed by a method described later to confirm the characteristics. In Examples 1 to 4, the biological electrode 2 is bonded through the separator 4 impregnated with physiological saline, and is similar to the biological electrode in the case where a paste layer is formed on the contact surface to the living body. This shows the characteristics.

(Comparative Example 1)
An attempt was made to produce a CNT sheet 21 by using the carbon fiber having a fiber diameter of micron which is not CNT, in the same manner as in Example 1. However, the fiber system is large and the sheet is not formed into a sheet due to insufficient strength. It was.

(Comparative Example 2)
A silver dish electrode (trade name: induction electroencephalogram dish electrode, model number: NE-132B, manufactured by Nihon Kohden Co., Ltd.) is used as the biological electrode, and this silver dish electrode is used in the same manner as the biological electrode 2 using the CNT sheet 21. Were prepared, bonded together through a separator, impregnated with physiological saline, sandwiched between glass plates and pressed with a clip.

(Comparative Example 3)
Carbon sheet 21 (product name Donakabo Paper S-251, sheet thickness) obtained by paper-molding by mixing resin binder with pitch-based carbon fiber (Donna carbon yarn, specific surface area 20 m ² / g or less, fiber diameter 13 μm) 1.3 mm, a sheet density of 0.038 g / cc), and a biological electrode was produced in the same manner as in Examples 1 to 4. Two of these biomedical electrodes were prepared and bonded together via the separator 4, impregnated with physiological saline, sandwiched between glass plates and pressed with a clip.

[Confirmation of layered structure]
4 to 7 show SEM images of fracture surfaces of the CNT sheets 21 created in Examples 1 to 4 described above. As can be seen from FIGS. 4 to 7, in Examples 1 to 4, it can be seen that CNTs are formed into a sheet shape. Moreover, the CNT sheet 21 of Example 1 and Example 2 shown in FIGS. 4 and 5 is higher in density than the CNT sheet 21 of Example 3 and Example 4 shown in FIGS. 6 and 7. I know that there is.

  Also, as shown in FIGS. 4 and 5, in Example 1 and Example 2 in which the CNT opening treatment and the dispersion solution suction filtration treatment were performed, the CNT aggregates were laminated so as to be compacted, and layered. You can see how the structure is formed. This is presumably because the CNTs that became aggregates in which the bundles were loosened by the fiber-opening treatment were laminated at a high density by the pressure of suction filtration.

  In Example 1, 10 layers were confirmed in the range of 30 μm, and the thickness of one layer was about 3 μm. Although each of the aggregates has a different size, one having a width of 0.1 μm or more and 500 μm or less, 1 μm or more and 200 μm or less, 10 μm or more and 100 μm or less was confirmed.

  In Example 2, 30 layers were confirmed in the range of 30 μm, and the thickness of one layer was about 1 μm. Although each of the aggregates has a different size, it was confirmed that the aggregate had a width of 0.1 μm to 100 μm, 0.5 μm to 50 μm, 1 μm to 20 μm.

  On the other hand, in Example 3 in which the fiber-opening treatment was not performed, the CNTs in a bundle were intertwined non-uniformly and did not have a layered structure (see FIG. 6). Further, in Example 4 in which the suction filtration treatment was not performed, the pressure applied to the CNT aggregate formed by the fiber opening process was weak, so the boundary between the aggregates disappeared, and the layered structure was not obtained (see FIG. 7). .

[Density and surface resistance]
The results of measuring the density and surface resistance of the bioelectrodes of Examples 1 to 4 are shown in Table 1 below.
<Measurement conditions>
Density: The CNT sheets of Examples 1 to 4 and the carbon sheet of Comparative Example 3 were cut into a width of 1.5 cm and a length of 1.5 cm, the weight and thickness of the sheet were measured, and the density was calculated.
-Surface resistance: The CNT sheets of Examples 1 to 4 and the carbon sheet of Comparative Example 3 were cut into a width of 1 cm and a length of 5 cm, and the measurement terminals were connected so that the distance between the terminals was 4 cm.

  In each of Examples 1 to 4, a CNT sheet 21 is formed by paper-making a long and large specific surface area CNT. Therefore, compared with the carbon sheet of Comparative Example 3, it is considered that the density is increased, and as a result, the DC resistance can be greatly reduced.

  Moreover, even if it uses the same SWCNT, Example 1 has a higher density than Example 3, and it turns out that DC resistance is still lower. Moreover, even if it uses the same MWCNT, Example 2 has a higher density than Example 4, and it turns out that DC resistance is still lower. This is probably because the CNT sheets of Example 1 and Example 2 formed a layered structure by performing the fiber opening process.

[Impedance]
Using the biological electrodes 2 and 2 of Examples 1 to 4 and Comparative Examples 2 and 3, impedance at each frequency was measured under the following conditions.
<Measurement conditions>
Potential: Open circuit potential superimposed voltage: ± 10 mV
Frequency range: 1Hz to 100Hz

  FIG. 8 is a graph showing the impedance of Examples 1 to 4 and Comparative Examples 2 and 3. In Comparative Example 1, the impedance as a biological electrode could not be measured because it could not be formed into a sheet due to insufficient strength. In Comparative Example 3, a carbon sheet electrode is produced using carbon fibers having a fiber diameter of micron, and the impedance thereof is higher than that of the silver plate electrode of Comparative Example 2. On the other hand, all of the electrodes of Examples 1 to 4 show lower impedance than the electrode using the carbon sheet of Comparative Example 3 as well as the silver plate electrode of Comparative Example 2. This tendency is particularly noticeable at low frequencies.

  As can be seen from FIG. 8, Example 1 using SWCNT has a lower impedance than Example 2 using MWCNT. That is, since carbon nanotubes having a long fiber length of 200 μm or more are used, the contact area between the fibers increases, and the impedance can be reduced.

  In FIG. 8, the graphs of Example 2 and Example 3 almost overlap, so FIG. 9 shows the impedance of Example 1 and Example 3, and FIG. 10 shows the impedance of Example 2 and Example 4. As shown in FIG. 9, the impedance of Example 1 is lower than that of Example 3. This is because in Example 1, the layered structure of CNTs is formed by performing the fiber opening process.

  As shown in FIG. 10, the impedance of Example 2 is lower than that of Example 4. This is also because a layered structure of CNTs is formed by performing the fiber opening process in Example 2.

  In addition, as described above, the biological electrode 2 having the paper-molded CNT sheet 21 of Examples 1 to 4 exhibits the effect of greatly reducing the impedance as compared with the silver plate electrode of Comparative Example 2. Yes.

[Experimental example of gel layer]
In Examples 1 to 4, the characteristics of the biological electrodes 2 and 2 bonded through the separator 4 impregnated with physiological saline were confirmed. Next, in Examples 5 to 8, the characteristics of the biological electrodes 2 and 2 bonded through the gel sheet were confirmed. Thereby, the characteristics of the biomedical electrode in which the gel layer 24 is formed on the contact surface with the living body as shown in FIG. 1 can be confirmed.

(Example 5)
70 mg of SWCNT (specific surface area 800 m ² / g, fiber length 500 μm, fiber diameter 3 nm) and 30 cc of isopropyl alcohol were stirred for 5 minutes at a rotational speed of 20000 rpm using a homogenizer to prepare a dispersion solution of CNTs. The produced dispersion solution 10 cc was further stirred for 10 minutes using a ball mill to perform the CNT opening process. At this time, the ball diameter was 0.5 mm and the rotation speed was 1000 rpm. Subsequently, the dispersion solution of CNTs was suction filtered using PTFE filter paper (diameter: 35 mm, average pore size 0.2 μm), and the residue on the filter paper was dried at 110 ° C. for 10 minutes with a rotary dryer. A CNT sheet 21 was produced.

(Example 6)
A CNT sheet 21 was produced in the same manner as in Example 5 except that SWCNT was changed to MWCNT (specific surface area 250 m ² / g, fiber length 15 μm, fiber diameter 8 nm).

(Example 7)
The same material as in Example 5 was used. Without performing the CNT opening process using a ball mill, the dispersion solution of CNT produced by a homogenizer was suction filtered with a filter paper as it was. Otherwise, the CNT sheet 21 was produced in the same manner as in Example 5.

(Example 8)
The same material as in Example 6 was used. Without performing the CNT opening process using a ball mill, the dispersion solution of CNT produced by a homogenizer was suction filtered with a filter paper as it was. Otherwise, the CNT sheet 21 was produced in the same manner as in Example 5.

  Using the CNT sheet 21 of each example produced by the method described above, the biological electrode 2 shown in FIG. 3A was produced in the same manner as in Examples 1 to 4. That is, the adhesive 6 was applied to one surface of the CNT sheet 21, the insulating tape 7 was affixed, and punched out so as to have a disk portion and a lead portion, thereby producing the bioelectrode 2.

  Subsequently, two biomedical electrodes 2 thus obtained were prepared, and a gel sheet was attached to the exposed surface of the CNT sheet 21 of one biomedical electrode 2. The other biomedical electrode 2 was opposed so as to be bonded with the gel sheet interposed therebetween, sandwiched between glass plates, and pressurized with a clip.

(Comparative Example 4)
The same as the biological electrode 2 using the CNT sheet 21 of Examples 5 to 8 using a silver dish electrode (trade name: Equivalent EEG dish electrode, model number: NE-132B, manufactured by Nihon Kohden Co., Ltd.) as the biological electrode. In addition, two silver dish electrodes were prepared, and a gel sheet was attached to the exposed surface of one silver dish electrode. The other silver plate electrode was opposed so as to be bonded with a gel sheet sandwiched between them, sandwiched between glass plates and pressurized with a clip.

(Comparative Example 5)
Carbon sheet 21 (product name Donakabo Paper S-251, sheet thickness 1.3 mm, mixed with resin binder mixed with pitch-based carbon fiber (Donna carbon yarn, specific surface area 20 m2 / g or less, fiber diameter 13 μm), Using a sheet density of 0.038 g / cc), biomedical electrodes were produced in the same manner as in Examples 5-8. Two biomedical electrodes using this carbon sheet were prepared, and the gel sheet was affixed on the surface where the carbon sheet of one biomedical electrode was exposed. The other biomedical electrode was opposed so as to be bonded with a gel sheet sandwiched therebetween, sandwiched between glass plates, and pressurized with a clip.

[Impedance]
Using the biological electrodes of Examples 5 to 8 and Comparative Examples 4 and 5, impedance at each frequency was measured under the following conditions.
<Measurement conditions>
Potential: Open circuit potential superimposed voltage: ± 10 mV
Frequency range: 1Hz to 100Hz

  FIG. 11 is a graph showing impedances of Examples 5 to 8 and Comparative Examples 4 and 5. In Examples 5 to 8 using the gel sheet, the same characteristics as those in Examples 1 to 4 can be confirmed. That is, the biomedical electrodes of Examples 5 to 8 all have a lower impedance than the electrode using the silver plate electrode of Comparative Example 4 and the carbon sheet of Comparative Example 5. This tendency is particularly noticeable at low frequencies. From the above, it can be seen that the effect of reducing impedance can be obtained even when the gel layer 24 is formed on the contact surface of the living body electrode with the living body.

(3) Effects As described above, the living body electrode 10 of the present embodiment uses the CNT sheet 21 formed by paper-making carbon nanotubes having a high density and a large specific surface area, thereby reducing impedance at a low frequency. The signal can be detected well. Moreover, since the carbon nanotube is used, it can be used in combination with X-ray CT. Furthermore, it is cheap and can be disposable, and the hygiene aspect can be improved.

The CNT used for the CNT sheet 21 may have a specific surface area of 50 m ² / g or more and less than 2600 m ² / g. Thereby, an increase in impedance can be prevented.

  The CNT sheet 21 may have a thickness in the range of 100 nm or more and less than 10 mm. Thereby, an increase in impedance can be prevented.

  The CNT sheet 21 may be produced without using a binder. Thereby, an increase in resistance can be prevented.

  The CNT sheet 21 may have a porous carbon powder dispersed in CNTs and having a particle diameter of less than 100 nm. Larger capacity can be obtained with carbon powder.

  A gel layer 24 serving as a contact surface with a living body may be formed on the surface of the CNT sheet 21. The adhesiveness to the living body can be improved by the gel that is solid.

  Further, the CNT sheet 21 may include a CNT having a layered structure. Thereby, the density can be further increased, the contact area between the aggregates can be increased, and the impedance can be reduced. Moreover, since the impedance is low, the area of the CNT sheet of the bioelectrode can be reduced, which is advantageous by multipoint measurement.

  The carbon nanotube having a layered structure may be a laminate of carbon nanotube aggregates obtained by opening a bundle. By stacking the aggregates of the opened carbon nanotubes, high density and low impedance can be obtained.

  The aggregate of carbon nanotubes preferably has a thickness of 0.3 μm to 10 μm and a width of 0.1 μm to 500 μm. By setting this range, an increase in impedance can be prevented.

  The carbon nanotubes having a layered structure are obtained by suction-filtering a dispersion solution of carbon nanotubes using a filter paper and molding the residue on the filter paper into a sheet shape. By suction filtration, a high pressure is uniformly applied to the aggregate of carbon nanotubes, and a dense layer can be formed.

  The carbon nanotube dispersion solution is prepared by mixing the carbon nanotubes with a solvent and opening the carbon nanotubes. By performing the fiber opening process on the carbon nanotubes in the mixed solution, the carbon nanotubes become aggregates and a layered structure can be formed.

  The CNT sheet 21 may be formed without adding a binder such as a resin. An increase in resistance due to the addition of a binder can be prevented. In this embodiment, since the high-density CNT sheet 21 is formed by suction filtration of the CNT aggregate, sufficient strength can be maintained without adding a binder.

(4) Other Embodiments As described above, the embodiment of the present invention has been described. However, the embodiment is presented as an example, and various omissions, replacements, and modifications can be made without departing from the gist of the invention. It can be carried out. Such modifications are also included in the scope and gist of the invention together with the embodiments.

  For example, in the above-described embodiment, the example of FIG. 1 is shown as the structure of the biological electrode, and the example of FIG. 3 is used in the example. However, the biological electrode of the present invention is limited to these structures. is not. For example, a structure as shown in FIGS.

  In the example of FIG. 12, the gel layer 24 is laminated only on a part of the surface of the CNT sheet 21, and a part of the surface of the CNT sheet 21 is exposed. With such a structure, since the CNT sheet 21 can also serve as a lead wire, the lead wire 25 can be omitted.

  In the example of FIG. 13, the gel layer 24 is laminated only on a part of the CNT sheet 21 as in FIG. 12, and the CNT sheet 21 also serves as a lead wire. Further, the gel layer 24 is fixed so that a part of the gel layer 24 bites into the surface of the CNT sheet 21. Thereby, it is possible to prevent the gel layer 24 from being detached from the CNT sheet 21. Further, an insulating layer 26 is formed so as to surround the side surface of the gel layer 24. The insulating layer 26 is fixed so as to bite into the side surface of the gel layer 24. As a result, the insulating layer 26 can be prevented from being detached from the CNT sheet 21. The insulating layer 26 is preferably formed of a hard member having insulating properties. For example, a biocompatible insulating material can be used. As a result, when the gel layer 24 is brought into contact with the skin, the insulating layer 26 supports the gel layer 24, so that the CNT sheet 21 can be prevented from coming into direct contact with the skin. Also,

  In the example of FIG. 14, the gel layer 24 is fixed so as to partially penetrate the CNT sheet 21 as in FIG. 13, and the insulating layer 26 is formed around the gel layer 24. An electrolyte paste layer 27 is further formed below the gel layer 24. The paste layer 27 is also fixed so as to bite into the CNT sheet 21. The resistance can be reduced by the paste layer 27 containing the electrolyte, and the composite effect that the contact stability to the living body is obtained by the gel layer 24 can be obtained.

  In the example of FIG. 15, the lead wire 25 is larger than the CNT sheet 21. Therefore, one end of the lead wire 25 is not sandwiched between the CNT sheet 21 and the cover layer 23, but is laminated on the surface of the CNT sheet 21 via the adhesive layer 22, and further protrudes from the CNT sheet 21 to partially Is exposed. The cover layer 23 is the same size as the lead wire 25 and is laminated on the surface of the lead wire 25 opposite to the surface laminated on the CNT sheet 21.

2 Biological electrode 4 Separator 6 Binder 7 Insulating tape 10 Biological electrode 21 CNT sheet 22 Adhesive layer 23 Cover layer 24 Gel layer 25 Lead wire 26 Insulating layer 27 Paste layer

Claims (17)

  A biomedical electrode comprising a papermaking sheet containing carbon nanotubes. ^2. The bioelectrode according to claim 1, wherein the specific surface area of the carbon nanotube is in a range of 50 m ² / g or more and less than 2600 m ² / g.   The biomedical electrode according to claim 1 or 2, wherein the papermaking sheet has a thickness in a range of 100 nm or more and less than 10 mm.   The living body electrode according to any one of claims 1 to 3, wherein the papermaking sheet is produced without using a binder.   The biomedical electrode according to any one of claims 1 to 4, wherein the papermaking sheet further includes a carbon powder dispersed in carbon nanotubes and having a particle diameter of less than 100 nm and having been made porous. .   The living body electrode according to any one of claims 1 to 5, further comprising a gel layer provided on a surface of the papermaking sheet and serving as a contact surface with a living body.   The biological electrode according to claim 6, wherein the gel layer is provided on a part of the surface of the papermaking sheet, and a part of the surface of the papermaking sheet is exposed.   The living body electrode according to claim 6 or 7, further comprising an insulating layer formed around the gel layer and supporting the gel layer.   The biological electrode according to any one of claims 6 to 8, wherein the gel layer is fixed so as to partially bite into the papermaking sheet.   The biological electrode according to any one of claims 6 to 9, further comprising a paste layer containing an electrolyte provided between the gel layer and the papermaking sheet.   It has further a lead wire larger than the said papermaking sheet | seat laminated | stacked on the surface facing the surface in which the said gel layer of the said papermaking sheet | seat was provided. The biomedical electrode as described.   The biomedical electrode according to any one of claims 1 to 11, wherein the papermaking sheet includes a carbon nanotube having a layered structure.   13. The bioelectrode according to claim 12, wherein the carbon nanotubes having a layered structure are obtained by stacking aggregates of carbon nanotubes obtained by opening a bundle.   The biological electrode according to claim 13, wherein the aggregate of carbon nanotubes has a thickness of 0.3 to 10 µm and a width of 0.1 to 500 µm. A method for producing a biomedical electrode having a papermaking sheet containing carbon nanotubes,
A step of mixing a carbon nanotube and a solvent to prepare a dispersion solution of the carbon nanotube;
And a step of extracting the carbon nanotubes from the dispersion solution and molding the carbon nanotubes into a sheet shape.   The method for producing a biological electrode according to claim 15, wherein the carbon nanotubes are extracted from the dispersion solution by suction filtration of the dispersion solution using a filter paper. The method for producing a living body electrode according to claim 15 or 16, wherein the carbon nanotube is opened after the carbon nanotube and the solvent are mixed.