JPH03267041A - Conducting adhesive gel for medical treatment - Google Patents

Abstract

PURPOSE:To achieve higher adhesiveness between an electrode for a unit pickup and a human body by a method wherein a polymer having a specified constitution is plasticized, a low molecular dissociating salt is mixed therewith by dissolving to form a three-dimensional cross linked body and a conducting adhesive gel for medical treatment is prepared. CONSTITUTION:A polymer is synthesized which has an alkylene oxide long chain with two or more of repetition units of the alkylene oxide on a side chain thereof having a 40mol.% or more of an alkyl acrylate possessing a 2-18C alkyl group having 2-24mol.% of a dissociating functional group. After the polymer is plasticized, a low molecular dissociating salt is mixed therewith by dissolving, a three-dimensional cross-linked body structure is formed and a conducting adhesive gel for medical treatment is prepared. The conducting adhesive gel for medical treatment thus obtained has a sufficient strength to adhere to a human skin with a sufficient strength. A degree of balance expansion under water at 40 deg.C is below 3.5%.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to potential pickup electrodes (for example, electromyography electrodes, electroencephalogram measurement electrodes, electrocardiogram electrodes, electrooculography measurement electrodes, etc.) and current passive Conductive materials used for medical purposes or for biological observation of animals and plants to electrically and physically connect electrodes for electrical scalpels (e.g., return electrodes for electric scalpels, electrodes for low-frequency therapy devices, electrodes for iontophoresis, etc.) and living organisms. It concerns adhesive gel.

(Prior art) Until now, for the purpose of electrically and physically connecting electrodes for potential big amplifiers and electrodes for current passives to a living body,
A number of conductive adhesives or gels have been devised. A common feature of many of these proposed techniques is the use of polymer electrolytes as a means of achieving electrical conductivity. Examples of such means include carbon a salts (e.g.,
3.6939. JP 57-28505), quaternary ammonium salts (for example, JP 52-95895, JP 82-133935, JP 82-3596391)
, JP-A-62-270135, JP-A-62-29214
0. JP-A-63-43646), sulfonates (e.g., JP-A-55-81635, JP-A-58-13550)
6. JP-A-59-125545) and phosphates (for example, JP-A-61-85925).

These polymer electrolytes have very hard and brittle physical properties in a dry state and have very low conductivity. Therefore, in order to impart conductivity and adhesiveness to these polymer electrolytes, glycerin has to be added. It is necessary to plasticize these tough polymers by using a highly hydrophilic polyhydric alcohol, such as eg, in large quantities. Gels made by such means contain a large amount of plasticizer, so they have low gel strength and require support materials such as nonwoven fabric, and the gels tend to absorb moisture and desorb moisture due to changes in storage environment conditions, especially humidity. This has the disadvantage that the physical properties of the gel change greatly, so long-term deterioration of the physical properties is unavoidable, and in order to prevent this, expensive pancaging has been forced to be used. Furthermore, the fatal flaw when using these polyelectrolytes for such purposes is that when used under high humidity, the gels absorb moisture and sweat secreted from the skin, causing the gels to swell, resulting in sticky properties. In the worst case scenario, the electrode easily falls off from the skin due to its own weight. This drawback is an unavoidable problem when using polymer electrolytes for such purposes. Since the polymer disclosed in JP-A-56-36940 is composed of a nonionic polymer, it seems that the disadvantage of the adhesive gel swelling significantly can be avoided, but those who are involved in this field can easily explain the problem. As can be understood, the conductivity and adhesiveness of gels made from such technology are extremely low, and especially when connecting a potential pickup electrode to a living body using this gel, it is difficult to avoid interference from commercial power supply hum noise. It can be highly predicted that the purpose of physically connecting the living body and the electrode with sufficient strength will not be achieved due to its low adhesiveness.

What recently attracted the attention of inventors was Japanese Patent Application Laid-Open No. 621396.
This is an ion conductive gel disclosed in No. 28.

This gel is made of hydrophilic polyether urethane containing an alkali ionic compound, and is based on an unprecedented design concept for a nonionic hydrophilic gel that has relatively good conductivity and strong adhesiveness. It received attention because of its structure.

However, gels made from this technology have drawbacks stemming from the nature of the polymer synthesis and polymer structure, respectively.

A drawback in polymer synthesis is that the presence of water is not allowed during the gel-forming reaction. The gel-forming reaction referred to here refers to the reaction between a polyether polyol prepolymer and a polyisocyanate prepolymer. The conductivity of this adhesive gel made of polyether polyurethane gel is considerably inferior to that of the gel using the above-mentioned polymer electrolyte, so it cannot be used for the purpose of connecting potential pink-up electrodes and living organisms. ,
Furthermore, it is necessary to improve the conductivity. The simplest way to achieve this goal is to include a solvent with a high dielectric constant, such as water or (polyhydric) alcohol, in the gel. This is not a preferable method because it results in the generation of bubbles and a decrease in the physical properties of the adhesive. Therefore, when trying to improve conductivity using these solvents, it is necessary to add them in some way after the gel formation reaction, which results in a significant decrease in mass production efficiency. Will. In addition, strict control is required to avoid moisture absorption of the raw materials in the gel-forming reaction process and the raw material storage process, which inevitably increases costs.

A disadvantage of the polymer structure is that when a gel made from this technology is applied to a living body, the adhesive strength decreases relatively quickly.

This tendency is particularly noticeable when worn on slightly sweaty human skin.The reason for this is probably the low hydrophilicity of the polymer.

In other words, due to the gel's low hydrophilicity, the rate at which sweat secreted from the skin is absorbed is greater than the rate at which the gel absorbs the sweat, creating a sweat accumulation layer at the interface between the gel and the skin. As the body moves, the gel spreads over the entire surface and finally,
It is conceivable that the gel may come off. This is a fatal drawback when polyurethane made from polyether polyol is used for such purposes. This is because when attempting to further increase hydrophilicity, no effective means has been found other than increasing the proportion of ethylene oxide units in the raw material polyether polyol molecule. As researchers in this field can easily guess, increasing the proportion of ethylene oxide in the polyether polyol molecules promotes crystallization of the polyether polyol and the resulting gel. It is expected that this will make handling difficult in the process and also lead to a decrease in conductivity.

(Objective of the Invention) The object of the present invention is to solve the problems that could not be solved with the techniques proposed so far, namely, to ensure electrical and physical connection between the skin and the electrode even when used under high humidity. To provide a medical conductive adhesive gel that connects, maintains this connection for a long time, and maintains strong adhesiveness without falling off even when a human body sweats a little.

(Means for achieving the object) As a means for achieving the above object, the medical conductive adhesive gel of the present invention has a carbon number of 2 to 18 as an adhesive component.
40 mol% or more of an alkyl group, and 2 to 24 mol% of a dissociative functional group as an ion carrier,
Moreover, it is characterized by using a polymer characterized by having two or more alkylene oxide repeating units and having a long alkylene oxide chain in its side chain.

By controlling the type and amount of plasticizer, it is possible to provide sufficient adhesiveness by using only a polymer that does not exist in the alkylene oxide long-chain molecule, but sufficient conductivity cannot be obtained with this system alone. That is difficult. Therefore, when this polymer is used as a base polymer for an adhesive, it is necessary to contain an appropriate low molecular electrolyte. This yields a gel with adhesive properties and conductivity. However, when electrically connecting a potential pickup electrode to a living body, it is necessary to further improve conductivity to avoid hum noise from a commercial power source.

Methods for improving conductivity include increasing the content of dissociable functional groups as ion carriers and adding a small amount of water to the gel. If the former method is used, the purpose of improving conductivity can be achieved, but increasing the amount of dissociable functional groups in the base polymer will result in raising the glass transition temperature of the polymer, so this method is not sufficient. In order to obtain a strong adhesive property, a large amount of plasticizer is required, which is the same as the conventional technology of using a polyelectrolyte as a base polymer.

The disadvantages of this gel are as described above. Furthermore, if the conductivity is improved by the latter method, it will show good conductivity immediately after manufacturing, but if it is stored for a long time in a low humidity environment, the water added during manufacturing will evaporate. Therefore, in order to avoid this volatilization, it is necessary to use expensive packaging as described above, so this method cannot be said to be a desirable method either.

As a result of repeated research on this point, the inventors found that the above-mentioned alkyl group having 2 to 18 carbon atoms had a length of 40 m.

% or more and is a carrier of ions. 7M III
In the side chain of a polymer having 2 to 24 mol% of functional groups,
As a new ion carrier, a polymer into which a long chain of alkylene oxide with an alkylene oxide repeating number of 2 or more is introduced is used as a base polymer, this base polymer is plasticized with an appropriate plasticizer, and a low molecular electrolyte is contained therein. It has been found that a medical conductive adhesive gel with unprecedented adhesiveness, conductivity, and cohesive force can be obtained by crosslinking by a well-known means.

Next, each raw material constituting this medical conductive adhesive gel will be described in detail. The structure of the base polymer, when viewed in terms of monomer units, is basically composed of the following three units. That is, they are three components: an alkyl acrylate unit (A unit) having an alkyl group having 2 to 18 carbon atoms, an ion carrier unit (B unit), and other units (C unit).

The purpose of introducing the A unit is to lower the glass transition temperature of the base polymer to impart adhesiveness and to control hydrophilicity. The simplest and most practical method for introducing this unit is to copolymerize an alkyl ester of an α,β-unsaturated carboxylic acid having an alkyl group having 1 to 18 carbon atoms. Monomers suitable for this purpose include, but are not limited to, ethyl acrylate, acrylic acid
Examples include butyl, thi-butyl acrylate, 2-ethylhexyl acrylate, butyl methacrylate, 〇-lauryl methacrylate, tridecyl methacrylate, dibutyl fumarate, monobutyl itaconate, dibutyl itaconate, and the like. The proportion of A units in the base polymer is 40 mol% or more if the alkyl ester of α,β-unsaturated carboxylic acid is used as a unit, but the practical range is 60 to 90 Illo1%. 60 m
It was difficult to obtain sufficient adhesiveness when the content was less than 1%, and it was difficult to obtain sufficient hydrophilicity and conductivity when the content exceeded 90 mol%.

The purpose of introducing B units is to introduce an ion carrier into the base polymer and to control hydrophilicity in combination with the ratio of A units. B
As can be seen from the above explanation, the unit consists of a monomer unit having a dissociable functional group and an alkylene oxide repeating number of 2.
It consists of a monomer unit for introducing the above alkylene oxide long chain into the main chain of the base polymer.

As a means for introducing a dissociable functional group, when looking at the base polymer in terms of monomer units, it can be obtained by copolymerizing the following non-limiting monomers. α,β-unsaturated carboxylates (e.g. acrylates, methacrylates, itaconates, etc.), vinyl monomers with sulfonates (e.g. allylsulfonates, methacrylsulfonates, vinyl sulfonates) , 2-acrylamide-
(2-methylpropanesulfonate, etc.), monomers having a phosphate or phosphite (e.g., 2-acryloyloxyethyl phosphate, etc.), vinyl monomers having a quaternary ammonium salt (e.g., methacryloyloxyethyltrimethylammonium) Monomers such as chloride, methacrylate, ruamidopropyltrimethylammonium chloride, etc. are used to introduce dissociative functional groups, but they do not need to be in the salt form at the time of copolymerization, and can be partially neutralized after polymerization of the base polymer. It goes without saying that these dissociative functional groups can also be introduced by complete neutralization.
It is not limited to one type, and may be composed of monomer units having multiple types of dissociable functional groups.The proportion of these dissociable functional groups in the base polymer molecule is 2 to
24IIlo1%, practically 5 to 15 mol
% range. When the amount of 5IIlo is less than 1%, it is difficult to obtain sufficient hydrophilicity and cohesive force, and when it exceeds 15 mol%, the base polymer tends to become too hard and sufficient adhesive strength cannot be obtained.

There are two ways to introduce long alkylene oxide chains into the side chains of the base polymer: one is to use a polymer reaction, and the other is to copolymerize a vinyl monomer containing alkylene oxide. method seems to be better. A non-limiting structure of a monomer suitable for this purpose is shown in the following structural formula (1).

CH2=C-R.

(I) 0 = C-(E O) m-(A ○)
n-○ R23 4 Here, R5 is either IT or CH3, and R2 is an unsubstituted alkyl group such as H, CH3, CH2CH3, or a substituted alkyl group. (E○) represents an ethylene oxide unit, and m is a number of ≧0. (A○) indicates an alkylene oxide unit, and n is an integer of n≧2 or more, which is the number of repeats of the alkylene oxide unit. Non-limiting examples of alkylene oxide chains suitable for the present invention include those shown in structural formula (11).

(CH20), (CH2CH20)(
CH2CH(CH3) ○) (CH2CH2CH2CH20)
(■) (A○) shown in structural formula (1) may be a single unit of structural formula (n), or may be a random unit or block unit of multiple types of alkylene oxide units. However, from the viewpoint of hydrophilicity and conductivity, it is preferable that - part or all of (A○) shown in structural formula (1) is an ethylene oxide unit, and the number of m is 4 or more. is desirable. If the number is less than 4, it tends to be difficult to obtain sufficient hydrophilicity and conductivity. The monomer unit used as a means for introducing the alkylene oxide long chain is not limited to one type, and it is also possible to use a plurality of monomers in combination. Structural formula (1)
Non-limiting examples of monomers applicable to the above include polypropylene glycol monomethacrylate (propylene oxide repeating number (n=12)), polyethylene glycol monomethacrylate (n=7 to 9) polyethylene glycol (n-10) polytetramethylene Glycol (n-
5) Monomethacrylate, methoxypolyethylene glycol (n=8) allyl ether, methoxypolyethylene glycol (n:9) methacrylate, and the like.

The proportion of the monomer having this alkylene oxide chain in the base polymer is approximately 0.0%, although it is difficult to specify an appropriate range since the molecular weight of the monomer varies greatly depending on the number of repeating alkylene oxide units.
A tendency was observed that a range of 5 to 20 mol% was desirable.

The purpose of introducing the C unit is to finely adjust the adhesiveness, hydrophilicity, and cohesive force, and at the same time introduce a crosslinking functional group. Monomers suitable for this purpose include, without limitation, vinyl acetate, acrylonitrile, acrylamide, di-butylacrylamide, diacetone acrylamide, styrene, methyl methacrylate, methacrylic acid, acrylic acid,
Itaconic acid, maleic anhydride, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, dimethylaminoethyl methacrylate, methylol acrylamide, glycidyl methacrylate, acrylic acid-2
-methoxyethyl, ethoxyethoxyethyl acrylate, tetrahydrofurfuryl acrylate, etc. These monomers are incorporated into the base polymer by copolymerization, but as described above, they can also be used as crosslinking functional groups by known techniques. For example, it goes without saying that it also mentions the possibility of obtaining a self-crosslinking pace polymer, such as the combination of methacrylic acid and glycidyl methacrylate.The proportion of C units in the base polymer varies depending on the required properties. Therefore, it is not possible to provide a typical range.

The purpose of adding a plasticizer to the pace polymer is, of course, to plasticize the polymer, but also plays an important role in promoting the dissociation of the low molecular electrolyte, which will be described later. For this reason, it is difficult to achieve this purpose using only one type of plasticizer, and it is usually better to use a mixture of multiple plasticizers to obtain favorable results from the viewpoint of various physical properties. Non-limiting examples of plasticizers suitable for these purposes include water, polyhydric alcohols such as ethylene glycol, propylene glycol, and glycerin, polyethylene glycol derivatives such as ethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, and polyethylene glycol monomethyl ether; Polypropylene glycol derivatives such as polypropylene glycol, poly(oxyethylene-oxypropylene) alkyl ether, various other polyether (poly)ols, carbonate esters such as ethylene carbonate, propylene carbonate, and glycerin carbonate, N-methyl Although it varies greatly depending on the amide such as pyrrolidone, dimethylamide, hexamethylphosphoramide, polyoxyethylene alkylphenyl ether fatty acid ester, and polyoxyethylene glycerin, it is approximately 50 to 250 parts by weight per 100 parts by weight of the base polymer. The appropriate range is approximately 100%.

The base polymer used in the present invention has much lower wood affinity than the base polymer using polymer electrolytes found in the prior art, so in order to provide sufficient conductivity, it is necessary to dissolve and contain a low molecular electrolyte. things are necessary. Electrolytes for achieving this purpose include alkali metal ions represented by Li+, Na'', and K'' as cationic components, or quaternary ammonium ions represented by R4N'' (R is hydrogen or a lower alkyl group), Examples of anionic components include halogen ions represented by CI-, Br'', and do, thiocyanate ions, perchlorate ions, alkylsulfonate ions, and the like. The electrolyte made of the combination of elements illustrated here is not limited to one type, and it is also possible to use a mixture of a plurality of electrolytes. Furthermore, these electrolytes may be added in advance by dissolving them in the polymerization solvent '1, or they may be added after polymerization. Although the range is about the same as the amount of paper, 1 to 10 parts is a range in which the physical properties of both adhesiveness and conductivity are well balanced in practical terms. If it is less than 1 part, sufficient conductivity cannot be obtained, and if it exceeds 10 parts, the base polymer tends to become hard and it is difficult to obtain sufficient adhesiveness.

(Functions and Effects) The medical conductive adhesive gel of the present invention has properties that were not obtained with conventional technology, namely, long-term storage under high humidity,
Even after long-term use, it does not swell and maintains sufficient adhesion and cohesive force, and can maintain sufficient adhesion even to slightly sweaty skin, and contains almost no volatile and moisture-absorbing components. Since it is not contained in any of these materials, it has the characteristic that its physical properties do not change significantly even with inexpensive and simple packaging.

In addition, the present invention will be explained in more detail by referring to a Scandinavian example of a gel using a conventional polymer electrolyte.

[Measurement method] Sandwich it with S304), incorporate it into one end of the bridge,
A 1 k 11 z sine wave is applied and the impedance is measured by the Lissajous method. The volume resistivity value is calculated from this value and the shape of the gel. All measurements were performed at 23℃ and 60RH%.
I did it.

2. Equilibrium swelling degree (DS) A sticky gel with a thickness of about 1 mm is 10 mm in diameter (dl=1
0mm) and paste it on a Petri dish with an inner diameter of 8cm and a depth of 2cm. Pour 40ml of pure water into this petri dish.

Appropriate evaporation prevention was applied to this, and the adhesive gel with a thickness of about 11 + 1 m was cut into a rectangle of 2 × 5 CI11 and placed in a 40°C incubator. Leave it in an environment of 40RI% for about 2 weeks. This open surface is covered with soft vinyl chloride.

[Preparation of Polymer and Gel] Comparative Example 1 A 3-tube separable flask was charged with raw materials in the following proportions (parts by weight).

2-hydroxy methacrylate 43.9 parts acrylic acid 6.1 (P2O). Similar measurements were carried out on samples that had been left for 2 weeks at 40°C and 90 RI (%).
O). From these two data (P90/P40
) and use this as the rate of decrease in peeling force.

4. Moisture absorption increase rate (I A) A pressure-sensitive adhesive sheet with a thickness of about 1 cm was punched out to a diameter of 20 mm and heated at 40°C.
, 75 Leave it in an R11% environment for about 2 weeks, and the moisture absorption (
W75) is determined. At this time, the sheet of the same shape was heated at 40℃.
90R) 1% environment for two weeks, and the amount of moisture absorbed (W2O) was determined. From these two data ((enemy9
O-W75)/O-W75) was determined, and the moisture absorption increase rate and 18-hour polymerization were determined. After cooling the system to near room temperature, 5N
- 10.11 parts of sodium hydroxide solution was added to control the degree of neutralization of acrylic acid to 0.5. a polymerization solvent;
The water used for neutralization was removed by heating and the polymer was pulverized.

To 10 parts of the obtained polymer, 28 parts of glycerin and 12 parts of purified water were added, and a uniform dope was obtained by dissolving at 80° C. for 116 hours.

To 50 parts of this dope, 0.5 part of tetrafunctional polyglycerol polyglycidyl ether was added, and the mixture was heated at 60°C for 1 hour.
A sticky gel was obtained by heating for 6 hours.

Comparative example & The preparation materials are as follows.

Butyl acrylate 32 parts acrylic acid
18 Methanol 75 AIBN 1.64 Methanol 30.0 Lithium perchlorate 1.0 AIBN, 0.51 under nitrogen stream,
Polymerization was carried out for about 16 hours at reflux temperature.

The entire system was cooled to around room temperature, and 14.0 parts of polyoxyethylene nonylphenyl ether (average repeating number of oxyethylene 7.5) was added as a plasticizer, and dimethoxypolyethylene glycol (based on molecular weight) was added by heating at 60°C for 16 hours. A sticky gel was obtained.

Example 1 Raw materials were charged into a 3-piece separable flask in the following proportions (parts by weight).

18.0 parts of butyl acrylate and 2.0 parts of acrylic acid were added, and a sticky gel was obtained by heating at 60° C. for 16 hours.

Example 2 Raw materials were charged into a 3-tube separable flask in the following proportions (parts by weight).

Butyl acrylate 14.0 parts 5 6 Acrylic acid 2.0 MPEGMA (n=9) 4.0 Methanol 30.0 Lithium perchlorate 1.0 A I B N 0.51×MP
EGMA (n-9) means methoxypolyethylene glycol (the number of repeats of ethylene oxide n=9) methacrylate.

An adhesive sheet was obtained using the same operations and conditions as in Example 1.

Example 3 - (repetition number of ethylene oxide n=23) methacrylate.

An adhesive sheet was obtained using the same operations and conditions as in Example 1.

Example 4 Raw materials were charged into a 3-tube separable flask in the following proportions (parts by weight).

Butyl acrylate 14.0 parts Acrylic acid 2.0 MPEGMA (n-23) 4.0 Methanol 30.0 Lithium perchlorate 1.0 A I B N 0.52 parts
Tanol
30.0 Lithium perchlorate
1.0 A I B N 0.51*MP
EGMA (n=23) is methoxypolyethylene glyco (
Average repeating number of oxyethylene (7.5) 8.1 parts, glycerin carbonate 24.4 parts were added and mixed, and further 3
About 5 parts of N-potassium hydroxide is added to control the degree of neutralization of acrylic acid to 0.5. After confirming that the neutralization reaction was completed and the entire solution returned to room temperature, 0.27 parts of tetrafunctional polyglycerol polyglycidyl ether was added,
Raw materials were charged in the following proportions (parts by weight) into a 3-tube separable flask heated at 60°C for 116 hours.

Butyl acrylate 14.0 parts Acrylic acid 0.4 MPEGMA (n:23) 4.0 MO
ETMAC4,0 Methanol -
30.0 Lithium perchlorate
1.0 A I B N 0.52 Polymerization was carried out at a distillation temperature of 16 hours under a nitrogen stream.

The entire system was cooled to around room temperature, and 16.0 parts of polyoxyethylene nonylphenyl ether (average repeating number of oxyethylene 7.5) and 4.0 parts of dimethoxypolyethylene glycol (molecular weight 300) were added and mixed together with the plasticizer removed. Then, about 5 parts of 3N potassium hydroxide is added to control the degree of neutralization of acrylic acid to 0.5. After confirming that the neutralization reaction was completed and the entire solution returned to room temperature, the tetrafunctional polyglycerol polyglycidyl ether was added to 0.
22 parts were added and heated at 60° C. for 16 hours to obtain a sticky gel with a volume resistivity of 556 Ω·cl.

[Characteristics Evaluation] 1. Comparison of volume resistivity values Table 1 shows a comparison of the volume resistivity values of Examples 1 and 2.3. This data shows the effect of introducing long alkylene oxide chains on conductivity.

Table 1. Volume resistance value of Example (unit: kΩ・cm) 2. Comparison with conventional technology 9 0 Next, comparative example 1.2 and each characteristic value of Example 4 are shown in Table 2. I would like to clarify the superiority of this product compared to the one consisting of.

Table 2. Comparative Example 5 with the prior art shows that the coexistence of carboxylic acid salts and other dissociative functional groups as dissociative functional groups is possible.

As stated in the main text of the specification, the means for crosslinking is not limited to the reaction between the carboxylic acid salt and the water-soluble glycidyl compound shown in the examples, and any known means may be used. It is possible to do so.

Claims (1)

[Claims] (1) It has 40 mol% or more of an alkyl acrylate having an alkyl group having 2 to 18 carbon atoms as a monomer unit, has 2 to 24 mol% of a dissociative functional group, and has 2 or more repeating units of alkylene oxide. The essential condition was to use a polymer characterized by having a long alkylene oxide chain in its side chain, and this polymer was further plasticized and dissolved in a low-molecular dissociative salt to form a three-dimensional crosslinked structure. It is a conductive adhesive gel, has sufficient strength, adheres to the human body epidermis with sufficient strength, and has a
A medical conductive adhesive gel having an equilibrium swelling degree of 3.5 or less in °C water.