Method for manufacturing bioelectrodes

Abstract

To provide as one purpose, a biological electrode production method capable of stably embedding, a plurality of electrode elements and a conductor connected thereto, in a support medium formed of hydrogel.SOLUTION: There is provided a biological electrode production method comprising: a step for, on a recess bottom surface comprising an opening end communicated to a side face of a first mold, adhering and fixing a plurality of electrode elements, for arranging wiring; a step for flowing a hydrogel material into a recess of the first mold, gelatinizing the material in a mold in which the top face of the recess is closed, for forming a biological electrode intermediate product comprising a support medium formed of hydrogel on one face side of the electrode elements; a step for detaching the biological electrode intermediate from the first mold, and then installing the same in a recess of a second mold in a state of directing the electrode elements to a front face side; a step for flowing the hydrogel material to the recess of the second mold, gelatinizing the material in the mold in which the top face of the recess is closed, for forming the residual support medium, for detaching the integrated support medium from the second mold for acquiring the biological electrode in which the electrode elements are embedded in the support medium.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a biological electrode.

Background Art

[0002] When measuring biological information such as electrocardiogram, electromyogram, and electroencephalogram, biological electrodes are used. Thereby, biological signals are detected or a stimulating current is propagated through the living body.

[0003] Patent Document 1 discloses an electrode body and a method for manufacturing the electrode body. This patent document describes the structure of an electrode body in which an electrode is covered with a gel. Further, FIG. 7 of Patent Document 1 discloses a method for manufacturing an electrode body using a mold.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] One object of the present invention is to provide a method for manufacturing a biological electrode capable of stably embedding a plurality of electrode elements and wires (lead wires) connected thereto in a support made of hydrogel.

Means for Solving the Problems

[0006] In a method for manufacturing a biological electrode according to one aspect of the present invention, a plurality of electrode elements are attached and fixed, wired, or the wired electrode elements are fixed to the bottom surface of a recess having an open end leading to the side surface of a first mold. Then, the electrode element is attached and fixed to the bottom surface of the recess using an adhesive with the same components as the hydrogel raw material. A step of pouring the hydrogel raw material into the recess of the first mold, A member having a flat surface on the side facing the bottom surface of the recess is pressed against the opening upper surface of the first mold, pushing out the excess hydrogel material towards the open end, and the opening upper surface is closed.The process involves gelling the electrode element in a mold to form a bioelectrode intermediate with a hydrogel support on one side, and removing the bioelectrode intermediate from the first mold. The side of the electrode element attached to the first mold faces the upper surface of the opening. , the step of installing in the recess of the second mold, The aforementioned The hydrogel raw material is poured into the recess opening The method comprises the steps of gelling the support in a mold with a closed top surface to form the remaining support, and removing the integrated support from the second mold to obtain a bioelectrode in which the electrode element is embedded in the support.

[0008] A method for manufacturing a bioelectrode according to one aspect of the present invention is characterized in that, after removing the bioelectrode intermediate from the first mold, it is cut into a predetermined shape and placed in a recess of the second mold having substantially the same shape as the predetermined shape. [Effects of the Invention]

[0009] According to the present invention, multiple electrode elements and connecting wires can be stably embedded in a hydrogel support, and variations in the arrangement of each electrode element within the support can be reduced. [Brief explanation of the drawing]

[0010] [Figure 1] These are perspective views and cross-sectional views illustrating the manufacturing process of the bioelectrode according to this embodiment. [Figure 2] These are perspective views and cross-sectional views illustrating the manufacturing process of the bioelectrode according to this embodiment. [Figure 3] These are perspective views and cross-sectional views illustrating the manufacturing process of the bioelectrode according to this embodiment. [Figure 4] These are perspective views and cross-sectional views illustrating the manufacturing process of the bioelectrode according to this embodiment. [Figure 5] This is a perspective view showing the manufacturing process for cutting the bioelectrode intermediate obtained through the manufacturing processes shown in Figures 1 to 4 into a predetermined shape. [Figure 6] This is a perspective view of the bioelectrode intermediate obtained via Figure 5. [Figure 7]This is a perspective view showing the manufacturing process of the bioelectrode of this embodiment. [Figure 8] These are perspective views and cross-sectional views illustrating the manufacturing process of the bioelectrode according to this embodiment. [Figure 9] These are perspective views and cross-sectional views illustrating the manufacturing process of the bioelectrode according to this embodiment. [Figure 10] This is a perspective view showing the final bioelectrode formed through the manufacturing process of this embodiment. [Modes for carrying out the invention]

[0011] The method for manufacturing the bioelectrode of this embodiment will be described in detail below. In the following description, similar components will be denoted by the same reference numerals in all drawings, and their descriptions will be omitted as appropriate. The bioelectrode of this embodiment, as shown below, can be used for bioelectrodes other than intracranial grid electrodes, but as an example, we will explain the conventional problems, etc., using intracranial electrodes.

[0012] [Challenges of conventional bioelectrodes] For example, conventional intracranial grid electrodes for detecting brain surface electroencephalograms (EEGs) consist of small-diameter metal plates sandwiched between silicone rubber sheets and arranged and fixed in place. One side of the silicone rubber sheet has a hole through which the metal plate is exposed, creating a structure in which the electrode element (contact) made of the metal plate comes into contact with the brain surface.

[0013] In this structure, bending the silicone rubber sheet that serves as the substrate could easily cause the edges of the metal plate to protrude through the holes, posing a risk of damaging the brain surface or causing the electrode elements to detach. Furthermore, high-frequency radio waves emitted from the device during MRI imaging could heat the brain surface in contact with the electrode elements, potentially causing damage.

[0014] [Advantages of hydrogel bioelectrodes] Incidentally, in the case of a hydrogel biosensor, since the hydrogel itself contains an electrolyte solution, it has the same conductivity as a living body. Therefore, it is possible to detect brain waves without making holes in the support made of hydrogel. Further, the electrode element is embedded in the support made of hydrogel, and even if the support is bent, there is no possibility that the electrode element will protrude, and uniform brain wave detection can be achieved by making the film thickness constant. Furthermore, since it does not directly contact the brain surface, even if the temperature rises due to the high-frequency current during MRI imaging, the heat is dispersed and the risk of burns is reduced.

[0015] [Problems Regarding the Manufacturing Method of Hydrogel Biosensors] In the manufacturing method of a hydrogel biosensor, a method of embedding a plurality of electrode elements in a support made of hydrogel without removing them from the mold can be considered. For example, only half of the hydrogel raw material is put into the mold and gelled, a plurality of electrode elements are arranged thereon, and then the remaining hydrogel raw material is poured into the mold and gelled. By doing so, a hydrogel biosensor can be formed at once without removing it from the mold.

[0016] However, in the method of embedding a plurality of electrode elements in a support made of hydrogel using one mold as described above, it is difficult to fix the electrode elements during the manufacturing process, and when the remaining hydrogel raw material is poured into the mold, problems such as the electrode elements floating or being displaced occur. Therefore, the arrangement of the plurality of electrode elements embedded in the support is shifted, and the thickness of the support varies, resulting in a decrease in yield.

[0017] Therefore, as a result of intensive research by the present inventors, the mold for forming the support made of hydrogel and the mold for the final product are separated on one side of the plurality of electrode elements, so that each electrode element can be stably fixed during the manufacturing process, and a support made of hydrogel can be accurately formed on both sides of each electrode element. As a result, the variation in the arrangement of the electrode elements can be reduced, and a method for manufacturing a biosensor that can accurately and easily manufacture a biosensor having a desired shape has been invented.

[0018] [Specific description of the method for manufacturing bioelectrodes in this embodiment] Figure 1 shows a perspective view and a cross-sectional view illustrating the manufacturing process of the bioelectrode according to this embodiment. Figure 1(a) is a perspective view, and Figure 1(b) is a partial cross-sectional view of the perspective view of Figure 1(a) taken along line AA and viewed from the direction of the arrow. Note that the cross-sectional views shown in Figure 2 and subsequent figures are also cross-sectional views taken at the same position as Figure 1(a).

[0019] The X1-X2 and Y1-Y2 directions shown in Figure 1 are two orthogonal directions within the plane, with the Y1 direction being the forward direction, the Y2 direction being the backward direction, and the X1-X2 direction being the left-right direction.

[0020] As shown in Figures 1(a) and 1(b), a first recess 1 is formed on the surface of the first type M1. The depth of the first recess 1 is approximately half the thickness of the support made of hydrogel.

[0021] As shown in Figure 1(a), the first recess 1 is composed of a bottom surface 1a and side wall surfaces 1b, 1c, and 1d that surround the left-right (X1-X2) and rear (Y2) sides. On the other hand, the front (Y1) of the bottom surface 1a is an open end 2 that extends to the front side surface 1e of the first mold M1. The top of the first recess 1 is also open.

[0022] As shown in Figure 1(a), a narrow groove 1g for passing wiring 4 is formed in the side wall surface 1d located at the rear (Y2) of the first recess 1, extending to the rear side surface 1h of the first mold M1. The width dimension (length in the X1-X2 direction) of the narrow groove 1g is narrower than the width dimension of the side wall surface 1d.

[0023] While not limited to these dimensions, the width dimension of the first recess 1 in the left-right direction (X1-X2) is slightly larger than the width dimension of the final bioelectrode 20. Furthermore, the length dimension of the first recess 1 where the open end 2 is formed in the front-back direction (Y1-Y2) is larger than the length dimension of the final bioelectrode 20. Thus, the plane size of the first recess 1 is slightly larger than that of the final bioelectrode 20.

[0024] As shown in Figures 1(a) and 1(b), multiple electrode elements 3 are arranged at intervals and attached to the bottom surface 1a of the first recess 1. In Figure 1, multiple electrode elements 3 are arranged in a single row at intervals in the Y1-Y2 direction, and multiple such rows are formed at intervals in the X1-X2 direction, but this is not the only arrangement. For example, multiple electrode elements 3 may be arranged at intervals in the X1-X2 direction, or multiple electrode elements 3 may be arranged in a matrix with intervals in both the Y1-Y2 direction and the X1-X2 direction.

[0025] The electrode element 3 refers to a conductor for detecting biological signals or transmitting stimulating current to the living body. The material of the electrode element 3 is not particularly limited, but examples include carbon-based materials, metals, or stretchable conductors. Among these, it is preferable to select a carbon-based sheet that does not hinder the flexibility of the hydrogel.

[0026] Furthermore, the shape of the electrode element 3 is not limited to the circular shape shown in Figure 1, but may also be polygonal, elliptical, or other shapes. The thickness of the electrode element 3 is approximately a few micrometers to several hundred micrometers.

[0027] In Figure 1(a), lead wires 5 drawn from wiring 4 are electrically connected to each electrode element 3. As shown in Figure 1(a), the lead wires 5 can be directly connected to the surface of the electrode element 3, but the connection location is not limited. For example, tabs can be provided on the electrode element 3 and the lead wires 5 can be connected to these tabs.

[0028] As an example, after attaching and arranging multiple electrode elements 3 on the bottom surface of the recess of the first type M1, lead wires 5 are placed on top of each electrode element 3 according to their arrangement numbers and adhered with conductive paint. Then, an electrode number sticker can be attached on top. By assigning electrode numbers in this way, errors in the front and back surfaces of the bioelectrode intermediate can be prevented in later processes. Alternatively, in the process shown in Figure 1(a), multiple pre-wired electrode elements 3 may be fixed to the bottom surface of the recess of the first type M1.

[0029] Next, in the process shown in Figure 2, the hydrogel raw material 6 is poured from the supply nozzle 7 into the recess 1 of the first mold M1. Here, "hydrogel" refers to a structure in which water or an aqueous solvent is contained within a three-dimensional network structure containing a polymer. Hydrogels mainly contain water or an aqueous solvent, and specifically, although it depends on the intended use, from the viewpoint of flexibility, the water or aqueous solvent content is preferably about 85.0% by mass of the total amount of hydrogel. If it is 95% by mass or more, it becomes difficult to handle and easily breaks. If it is 70.0% by mass or less, it becomes a hard gel. For example, in the case of polyvinyl alcohol hydrogel, the water or aqueous solvent content can be determined from data that examines the relationship between the amount of PVA and the feel of the gel.

[0030] The hydrogel is colorless and transparent, but it may be made opaque or colored by adding pigments or other materials. The colorless and transparent nature allows for visual inspection of the electrode element 3, lead wire 5, and the biological surface beyond them, which are embedded in the support. This makes it possible to confirm the position of the electrode element 3 and easily check the connection status of the lead wire 5 (such as whether it is broken) when placing the bioelectrode 20 in biological tissue.

[0031] As shown in Figures 3(a) and 3(b), one side of each of the multiple electrode elements 3 is covered with hydrogel material 6. As shown in Figure 3(b), the hydrogel material 6 may be applied to a thickness slightly greater than the depth of the first mold M1, and a portion of the hydrogel material 6 may protrude above the opening of the first mold M1.

[0032] In Figures 4(a) and 4(b), the opening top surface of the first mold M1 is closed with a flat plate 8. The flat plate 8 is formed with at least one flat surface, and the flat surface is pressed against the opening top surface of the first mold M1. As a result, excess hydrogel material 6 flows toward the open end 2 of the first recess 1, or is expelled to the outside from the open end 2. The thickness of the hydrogel material 6 then matches the distance from the bottom surface 1a of the first recess 1 to the flat plate 8. Then, the hydrogel material 6 is gelled by freezing and thawing. It is preferable to repeat the freezing and thawing process multiple times.

[0033] By following the steps shown in Figures 1 to 4, a bioelectrode intermediate 10 can be formed having a plurality of electrode elements 3 and a support 11 made of hydrogel formed on one side of the electrode elements 3 (see Figure 5).

[0034] The bioelectrode intermediate 10 is removed from the first mold M1 and cut into a predetermined shape as shown in Figure 5. The cut is made along the dotted line in Figure 5. The recess 1 of the first mold M1 in this embodiment is provided with an open end 2, and in the process shown in Figure 4, when the upper surface of the recess is closed with the flat plate 8, excess hydrogel material 6 is pushed out toward the open end 2, so the length dimension of the bioelectrode intermediate 10 in the front-to-back direction (Y1-Y2) is larger than the length dimension of the final bioelectrode 20. Also, the width dimension (X1-X2) is formed to be slightly larger than the width dimension of the final bioelectrode 20. Therefore, in Figure 5, the length dimension in the front-to-back direction (Y1-Y2) and the width dimension in the left-to-right direction (X1-X2) of the bioelectrode intermediate 10 are cut to match the size of the final bioelectrode 20. Furthermore, if the width dimension of the bioelectrode intermediate 10 in the left-right direction (X1-X2) is manufactured using the first type M1 so that it matches the width dimension of the final bioelectrode, then only the length dimension of the bioelectrode intermediate 10 in the front-back direction (Y1-Y2) can be cut to match the length dimension of the final bioelectrode 20.

[0035] Figure 6 is a perspective view of the bioelectrode intermediate 10 after cutting. While not limited to this, the corners of the bioelectrode intermediate 10 can be cut and chamfered as shown in Figure 6. This chamfering process allows the finished bioelectrode 20 to be smoothly removed from the second recess 2 used in the next process.

[0036] In the step shown in Figure 7, the bioelectrode intermediate 10 shown in Figure 6 is placed in the second recess 12 of the second type M2. At this time, the exposed surface of the electrode element 3 is placed facing upwards within the second recess 12. As described above, by attaching a sticker with the electrode number when the lead wire 5 is connected to each electrode element 3 in the step shown in Figure 1, the front and back sides of the bioelectrode intermediate 10 can be identified, and in the step shown in Figure 7, the exposed surface of each electrode element 3 can be placed facing upwards without misidentification.

[0037] As shown in Figure 7, the second recess 12 formed in the second mold M2 differs from the first recess 1 formed in the first mold M1 in that its bottom surface 12a is surrounded on all four sides by side walls 12b to 12e. However, a narrow groove 12g for passing the wiring 4 is opened in the rear side wall 12d, and although not shown, in the process of Figure 9, when the upper surface of the recess is closed with the flat plate 14, at least one narrow groove for releasing the pressure on the hydrogel raw material 13 to the outside is opened in at least one of the side walls 12b, 12c, and 12e.

[0038] In the process shown in Figures 8(a) and 8(b), the hydrogel raw material 13 is poured from the supply nozzle 7 onto the surface of the bioelectrode intermediate 10, which is placed in the second recess 12 of the second mold M2. It is preferable that the hydrogel raw material 13 has the same composition as the hydrogel raw material 6 used in the process shown in Figure 2. As shown in Figure 8, the pouring of the hydrogel raw material 13 is stopped when the surface of the hydrogel raw material 13 is approximately aligned with the upper part of the opening of the second recess 12. When the hydrogel raw material 13 is polyvinyl alcohol hydrogel, polyvinyl alcohol hydrogel melts at temperatures above 70°C, but even if high-temperature hydrogel raw material is poured in the process shown in Figure 8, it cools down quickly, so the shape of the hydrogel support on one side constituting the bioelectrode intermediate 10 is maintained, and the electrode element 3 is not affected by the pouring of the hydrogel raw material 13.

[0039] In the process shown in Figures 9(a) and 9(b), the upper surface of the recess of the second mold M2 is closed with a flat plate 14, and the hydrogel raw material 13 is frozen and thawed to gel the hydrogel raw material 13. It is preferable to repeat the freezing and thawing process multiple times.

[0040] Furthermore, the hydrogel support 11 formed on only one side of the bioelectrode intermediate 10 and the remaining hydrogel support 16 prepared in the process shown in Figure 9 are integrated to such an extent that the joint is almost indistinguishable.

[0041] Next, in the process shown in Figure 10, the flat plate 14 is removed from the second mold M2, and the final bioelectrode 20 is taken out of the second mold M2. Then, burrs and other debris around the bioelectrode 20 are removed. Through this process, a bioelectrode 20 can be manufactured in which multiple electrode elements 3 are embedded in a hydrogel support 21 (a hydrogel support 11 and 16 shown in Figure 9(b) are integrated).

[0042] [Method for fixing multiple electrode elements] In this embodiment, multiple electrode elements 3 are attached and fixed to the bottom surface of the recess of the first mold M1. Specifically, it is preferable to attach and fix each electrode element 3 using an adhesive 15 (see Figure 1) which has the same components as the hydrogel raw material 6.

[0043] Therefore, if the hydrogel raw material 6 is polyvinyl alcohol (PVA) hydrogel, PVA glue, which has the same components as the hydrogel, is dripped onto the electrode placement position on the bottom surface of the recess, and the electrode element 3 is attached and fixed on top of it. PVA glue is made by dissolving PVA in warm water, and its adhesive properties are weak, similar to starch glue that hardens when dry. In this case, water-soluble PVA glue dries easily and hardens quickly, so PVA glue may also be used as a temporary fixing agent. This method can be applied not only to fixing the electrode element 3 but also to fixing the lead wire 5.

[0044] In this embodiment, the electrode elements 3 are attached and fixed using an adhesive 15 made of substantially the same material as the hydrogel raw material 6. Subsequently, when the hydrogel raw material 6 is poured in, the elements assimilate and become one with the one-sided support 11 made of hydrogel, allowing for easy removal from the mold. The material of the mold is not limited, but it can be made of a material from which the hydrogel can be easily removed, such as PTFE.

[0045] [Regarding the bioelectrode 20 in this embodiment] The bioelectrode 20 formed through the processes shown in Figures 1 to 10 has multiple electrode elements 3 embedded in a support 21 made of a thin sheet-like or film-like hydrogel. Each electrode element 3 is electrically connected to multiple lead wires 5, and each lead wire 5 is fixed together to a covering and brought out to the outside as wiring 4. Parts of the lead wires 5 and wiring 4 are embedded in the support 21. [Industrial applicability]

[0046] As described above, the present invention reduces variations in the arrangement of electrode elements by forming hydrogel supports on each electrode element using separate molds, and is therefore preferably applied as a bioelectrode for measuring biological information such as electrocardiograms, pulse waves, electromyograms, and electroencephalograms. [Explanation of Symbols]

[0047] 1: First recess 1a: Bottom 1b~1d: Side wall surface 1e: Front side 1g:Narrow groove 1h: Rear side 2 :Open end 3: Electrode element 4: Wiring 5: Lead wires 6: Hydrogel raw materials 7: Supply nozzle 8, 14: Plane plate 10: Bioelectrode intermediate 11, 16, 21: Support 12: Second recess 12a: Bottom 12b~12e: Side wall surface 12g:Narrow groove 13: Hydrogel raw materials 15: Glue 20: Bioelectrodes M1: Type 1 M2: Type 2

Claims

1. The process involves attaching and fixing multiple electrode elements to the bottom surface of a recess having an open end leading to the side of the first type, wiring them, or fixing the wired electrode elements, and in this process, attaching and fixing the electrode elements to the bottom surface of the recess using an adhesive having the same components as the hydrogel raw material. The process involves pouring the hydrogel material into the recess of the first mold, pressing a member having a flat surface on the side facing the bottom of the recess against the opening upper surface of the first mold to push out the excess hydrogel material toward the open end, and gelling the material inside the mold with the opening upper surface closed to form a bioelectrode intermediate having a support made of hydrogel on one side of the electrode element, The steps include removing the bioelectrode intermediate from the first mold and placing it in the recess of the second mold such that the side of the electrode element attached to the first mold faces the upper surface of the opening, The process includes the step of pouring the hydrogel raw material into the recess of the second mold, gelling it within the mold with the opening of the recess closed, and forming the remaining support, The integrated support is removed from the second mold to obtain a bioelectrode in which the electrode element is embedded in the support. A method for manufacturing a bioelectrode, characterized by the following:

2. The method for manufacturing a bioelectrode according to claim 1, characterized in that, after removing the bioelectrode intermediate from the first mold, it is cut into a predetermined shape and placed in a recess of the second mold having substantially the same shape as the predetermined shape.

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