Preparation method and application of flexible gel electrode for electroencephalogram monitoring

Abstract

The invention provides a preparation method and application of a gel electrode for electroencephalogram monitoring, and belongs to the technical field of electroencephalogram signal acquisition. The method is used for manufacturing electrodes for electroencephalogram signal detection. The method mainly comprises the following steps: sequentially dissolving 6H2O. MgCl2 and PVA in a mixed solution of EG and deionized water, stirring at a high temperature until PVA is completely dissolved to obtain a transparent mixed solution, then adding a conductive dispersion liquid, mixing to obtain a conductive gel solution, uniformly stirring, standing, repeatedly freezing and thawing, standing at room temperature to obtain a gel electrode main body, matching with a copper plate and a wire, connecting with the electrode main body, and carrying out electrostatic spinning to obtain the electrode. And obtaining the gel electrode. The prepared gel electrode does not need to use conductive paste, is convenient to operate, soft, comfortable, high in elasticity, high in moisture retention and good in use experience, can accurately monitor electroencephalogram signals, and has great potential in the aspect of long-term electroencephalogram monitoring.

Description

Technical Field

[0001] The present application relates to a preparation method and application of a gel electrode for electroencephalogram monitoring. Background Art

[0002] Electroencephalogram (EEG), as an important bioelectric detection means in modern science, essentially originates from the spontaneous discharge phenomenon of brain neurons. As an important bioelectric signal, it forms a visual waveform after being amplified by a precision instrument on the scalp surface, providing key data support for interdisciplinary research. In medical practice, EEG technology can accurately locate epileptic foci; in the field of psychology, it can analyze the characteristics of emotional fluctuations; and it also serves as the core data source of the brain-computer interface in the development of artificial intelligence, showing broad application prospects.

[0003] The key component for realizing EEG signal acquisition - the electroencephalogram electrode, whose performance directly affects the data quality. There are obvious differences in the current mainstream technologies: traditional wet electrodes rely on conductive paste media to significantly reduce the contact impedance. Although ideal signal quality can be obtained, there are problems such as long time consumption, complex operation, and residual cleaning. The emerging dry electrodes, although eliminating the use link of conductive paste, are limited by the physical properties of rigid materials such as metals, resulting in an increase in contact impedance and insufficient wearing comfort. These two types of electrodes both face technical bottlenecks in clinical and scientific research applications and urgently need breakthroughs in new materials and structural designs.

[0004] Hydrogel materials bring new breakthroughs to solve this technical bottleneck. Its three-dimensional network structure has both ionic conductivity characteristics and soft tissue-like mechanical properties, and the contact impedance is effectively reduced compared with dry electrodes; the unique self-adhesive property can closely fit the irregular scalp surface without external fixing devices and still maintain stable signal acquisition during strenuous exercise; the biocompatible material system supports continuous wearing without skin irritation, and the performance is significantly better than the traditional electrode system. Summary of the Invention

[0005] In view of this, the present invention provides a preparation method and application of a gel electrode for electroencephalogram monitoring, which can not only reduce the electrode-skin contact impedance, ensure the electroencephalogram signal quality, but also increase the flexibility and moisture retention of the electrode material, and improve the use comfort.

[0006] The preparation method of a flexible gel electrode for electroencephalogram monitoring provided by the present invention includes the following steps:

[0007] Step 1: Add ethylene glycol to deionized water and mix evenly;

[0008] Step 2: Add magnesium chloride hexahydrate to the mixed solution and stir until it is completely dissolved;

[0009] Step 3: Add polyvinyl alcohol to the mixed solution, heat and stir to completely dissolve it;

[0010] Step 4: Add the conductive dispersion liquid, stir evenly and then let it stand;

[0011] Step 5: Repeatedly freeze-thaw the homogeneous solution and let it stand at room temperature to obtain the gel electrode body;

[0012] Step 6: Cooperate with the copper plate and wire, connect it to the gel electrode body to obtain the gel electrode.

[0013] The present invention also provides a gel electrode prepared by the above method.

[0014] The present invention also provides an application of the described gel electrode in an electroencephalogram monitoring device.

[0015] The gel electrode provided by the present invention is excellent in conductivity, long-term stability, use comfort, biocompatibility, etc., can meet the requirements of electroencephalogram signal acquisition, does not require conductive paste, is convenient to operate, and has a good use experience. Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0017] Figure 1 It is a physical diagram of the main body of the gel electrode of the present application;

[0018] Figure 2 It is a physical diagram of the gel electrode of the present application;

[0019] Figure 3 It is a moisture retention test diagram of the gel electrode prepared by the present application;

[0020] Figure 4 It is an elastic stretching test diagram of the gel electrode of the present application;

[0021] Figure 5 It is a dynamic sensing resistance signal diagram of the gel electrode of the present application at intervals of 7 days.

[0022] Figure 6 It is an electroencephalogram signal diagram collected by the hydrogel electrode of the present application. Detailed Embodiments

[0023] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clearly understood, the following will further elaborate on the technical solutions in the embodiments of this application in conjunction with the accompanying drawings in the embodiments of this application. It should be understood that the specific embodiments described herein are only used to explain this application and are not used to limit the technical solutions of this application. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope protected by this application.

[0024] A preparation method of a gel electrode for electroencephalogram monitoring provided by this application is as follows:

[0025] Step 1: Add EG to deionized water, stir at room temperature, and mix evenly.

[0026] Step 2: Add 6H2O·MgCl2 to the mixed solution, stir at room temperature until it is completely dissolved.

[0027] Step 3: Add PVA to the mixed solution, first stir at low speed and low temperature to make it swell and not stick, then dissolve it by sealing at high temperature, and then stir at high speed and low temperature and seal and let it stand to make it completely dissolved and have a low bubble volume, obtaining the base of the gel electrode.

[0028] Step 4: Add a conductive dispersion liquid, stir evenly at high speed and low temperature, and let it stand to eliminate bubbles.

[0029] Step 5: Pour the uniformly mixed solution into a mold, freeze-thaw repeatedly, and let it stand at room temperature to obtain the gel electrode body, as shown in Figure 1 .

[0030] Step 6: Cooperate with a copper plate and a wire, connect them to the gel electrode body to obtain the gel electrode, as shown in Figure 2 .

[0031] Furthermore, as a preference:

[0032] In Step 1: The mass ratio of deionized water to EG in the mixed solution is 6 - 20:3 - 15, the stirring temperature is 20 - 25°C, the stirring time is 5 - 15 min, and the stirring speed is 100 - 200 r / min.

[0033] In Step 2: The mass ratio of 6H2O·MgCl2 to PVA is 1 - 10:60 - 85, the stirring temperature is 20 - 25°C, the stirring time is 5 - 15 min, and the stirring speed is 100 - 200 r / min.

[0034] In Step 3: The stirring process is divided into two stages:

[0035] In the first stage, the stirring temperature is 45 - 60 °C, the stirring speed is 100 - 200 r / min, and the stirring time is 1.5 - 2 h, so that PVA swells by absorbing water and there are no obvious bubbles.

[0036] In the second stage, the mixed solution is sealed with tin foil and left to dissolve in an oven at 90 - 95 °C. After complete dissolution, it is taken out and the stirring temperature is adjusted to 90 - 95 °C, the rotation speed is moderately adjusted to 100 - 200 r / min, and finally it is sealed and left in the oven at 90 - 95 °C until the bubbles completely disappear.

[0037] In step 4: The conductive dispersion is a blend polymer of poly(3,4 - ethylenedioxythiophene) and polystyrene sulfonate. It is added dropwise into the dispersion in batches to make it evenly mixed without bonding and shaping. After all are evenly mixed, it is placed in a high - temperature environment of 80 °C - 95 °C and sealed and left standing for 30 - 45 min to eliminate a small amount of bubbles, and then poured into a mold.

[0038] In step 5: The freeze - thaw process is to put it in a refrigerator at - 15 °C - 25 °C and freeze for 6 - 12 h, then take it out and leave it standing at room temperature for 4 - 8 h, repeating 3 - 5 times.

[0039] In the above solution, EG is used as a conductive enhancer, which can increase the mobility and concentration of carriers, greatly improve the conductivity, and effectively reduce the contact impedance between the electrode and the skin; 6H2O·MgCl2 is used both as a conductive raw material to increase the conductivity of the gel and as an enhancer for the elasticity of the base material, effectively regulating the physical properties of the gel; PEDOT:PSS is used as a conductive raw material, and PEDOT:PSS has ion - electron conductivity; PVA is the main gel base material. PVA and PEDOT:PSS can be well miscible and form a semi - interpenetrating polymer network. Moreover, the PVA molecular chain contains a certain amount of hydroxyl groups, which improve the moisture - retaining performance of the gel electrode through hydrogen bonds between water molecules.

[0040] Example 1

[0041] First, take 6 ml of deionized water and 6 ml of EG, stir them evenly at room temperature of 100 r / min for 10 min, then add 0.27 g of 6H2O·MgCl2 and stir at room temperature of 100 r / min for 15 min (or heat in an oil bath at 25 °C) until the 6H2O·MgCl2 crystals are completely dissolved. Subsequently, weigh 1.8 g of PVA and add it to the mixed solution, keep stirring at a low speed for 1.5 h until the PVA swells by absorbing water, seal it with tin foil and let it stand in an oven at 90 °C to dissolve. After complete dissolution, take it out, adjust the stirring temperature to 90 °C, moderately adjust the rotation speed to 100 r / min, and finally seal it and let it stand in an oven at 90 °C until all the bubbles disappear and the solution becomes transparent and white. Finally, evenly drop 10 ml of conductive dispersion liquid, adjust the stirring temperature to 80 °C, keep stirring at a low speed until evenly mixed, and the solution becomes dark brown with a small amount of bubbles. After sealing and standing in an oven at 90 °C for 30 min, pour it into a mold, take it out after freezing in a -20 °C refrigerator for 12 h, let it stand at room temperature for 6 h, and perform freeze-thawing 3 times to fix the gel shape.

[0042] Use a digital multimeter (DEM11) and a multifunctional resistance box to test the resistance of the conductive gel, and measure it multiple times through static measurement and dynamic stretching. The static resistance results are shown in Table 1. The average resistance value is 15.30 Ω, the static resistance is stable within 5 - 25 Ω, and the dynamic sensing resistance is stable within 60 - 100 ohms, as Figure 5 . The average conductivity is 2.96×10 2 s·m -1 , and there are relevant literatures indicating that when the conductivity reaches 0.31 s·m -1 , electroencephalogram (EEG) signals can be well collected. Therefore, the electrical properties of the conductive gel of the present invention can meet the requirements for EEG signal monitoring.

[0043] Table 1: Static resistance values

[0044]

[0045] Example 2

[0046] First, take 9 ml of deionized water and 6 ml of EG, stir them evenly at 100 r / min at room temperature for 10 min, then add 0.27 g of 6H2O·MgCl2 and stir at 100 r / min at room temperature for 15 min until the 6H2O·MgCl2 crystals are completely dissolved. Subsequently, weigh 1.8 g of PVA and add it to the mixed solution, keep stirring at a low speed for 2 h until the PVA absorbs water and swells, seal it with tin foil and place it in an oven at 90 °C to dissolve. After complete dissolution, take it out, adjust the stirring temperature to 90 °C, moderately adjust the rotation speed to 100 r / min, and finally seal it and place it in an oven at 90 °C until the bubbles completely disappear and the solution becomes transparent and white. Finally, evenly drop 12 ml of conductive dispersion liquid, adjust the stirring temperature to 80 °C, keep stirring at a low speed until evenly mixed, the solution becomes dark brown and has a small amount of bubbles. Place it in an oven at 90 °C in a high-temperature environment, seal it and let it stand for 30 min to eliminate the bubbles, then pour it into a mold, take it out after freezing in a -20 °C refrigerator for 12 h, let it stand at room temperature for 6 h, and freeze-thaw it 3 times to shape the gel.

[0047] Use a skin moisture tester (MPA SERIES 6) to measure the moisture retention of the conductive gel. After the experimental subjects rest in the measurement environment for 15 min, monitor the skin moisture content in a specific area on the inner side of the arm, then place the conductive gel on the specific area on the inner side of the arm, remove it after resting for 1 hour, observe the skin condition, and measure the skin moisture, as Figure 3 shown. The results show that the skin does not show any allergic or red and swollen phenomena and the skin epidermal moisture content has increased significantly. The average growth rate of the skin moisture in the corresponding area is 110.08%, indicating that the prepared gel electrode has excellent biocompatibility and moisture retention.

[0048] Example 3

[0049] First, take 12 ml of deionized water and 12 ml of EG, stir them evenly at 100 r / min at room temperature for 15 min, then add 0.54 g of 6H2O·MgCl2 and stir at 100 r / min at room temperature for 15 min until the 6H2O·MgCl2 crystals are completely dissolved. Subsequently, weigh 3.0 g of PVA and add it to the mixed solution, keep stirring at a low speed for 2 h until the PVA absorbs water and swells, seal it with tin foil and place it in an oven at 90 °C to dissolve. After complete dissolution, take it out, adjust the stirring temperature to 90 °C, moderately adjust the rotation speed to 100 r / min, and finally seal it and place it in an oven at 90 °C until the bubbles completely disappear and the solution becomes transparent and white. Finally, evenly drop 12 ml of conductive dispersion liquid, adjust the stirring temperature to 80 °C, keep stirring at a low speed until evenly mixed, the solution becomes dark brown and has a small amount of bubbles. Seal it and let it stand in an oven at 90 °C for 30 min, then pour it into a mold, take it out after freezing in a -20 °C refrigerator for 12 h, let it stand at room temperature for 6 h, and freeze-thaw it 3 times to shape the gel.

[0050] The tensile properties of the conductive gel were measured using a universal testing machine (Instron Model 3367). The tensile properties of the conductive gel and the control group with the same concentration are as Figure 4 shown. The tensile strength increased by 201.11% and the elongation at break increased by 287.88%, indicating that the prepared gel electrode has excellent elasticity.

[0051] It can be seen from Examples 1 to 3 that the electrode of the present invention has excellent electrical conductivity, elasticity and moisture retention, can monitor electroencephalogram signals, and when used in an electroencephalogram monitoring device, the electrode-skin contact impedance is stable and has long monitoring stability.

[0052] In addition, the present application also provides an application method of the above gel electrode, that is: an electroencephalogram monitoring device, which includes a gel electrode having the above characteristics. The electroencephalogram monitoring device can be an implanted electroencephalogram electrode, such as electrocorticogram, penetrating intracortical electrode, etc.; it can also be a non-implanted electroencephalogram electrode, such as an electrode cap. The electroencephalogram signals collected by the hydrogel electrode are visible Figure 6 .

[0053] The above embodiments only represent several feasible implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation to the scope of the present invention patent. The embodiments are not intended to limit the protection scope in the claims of the present invention. For those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can be made. Any equivalent implementation or change made without departing from the present invention should be included in the technology of the present invention.

Claims

1. A preparation method of a flexible gel electrode for electroencephalogram monitoring, characterized in that, It includes the following steps: Step 1: Add ethylene glycol to deionized water and mix evenly; Step 2: Add magnesium chloride hexahydrate to the mixture and stir until it is completely dissolved; Step 3: Add polyvinyl alcohol to the mixture, heat and stir until it is completely dissolved; Step 4: Add a conductive dispersion liquid, stir evenly and then let it stand; Step 5: Repeatedly freeze-thaw the homogeneous solution and let it stand at room temperature to obtain the gel electrode body; Step 6: Cooperate with a copper plate and a wire to connect it to the gel electrode body to obtain a gel electrode.

2. The preparation method of a gel electrode for electroencephalogram monitoring according to claim 1, characterized in that: In Step 1, the mass ratio of deionized water to ethylene glycol in the mixture is 6 - 20:3 - 15, the stirring temperature is 20 - 25°C, the stirring time is 5 - 15 min, and the stirring speed is 100 - 200 r / min.

3. The preparation method of a gel electrode for electroencephalogram monitoring according to claim 1 or 2, characterized in that: The mass ratio of magnesium chloride hexahydrate to polyvinyl alcohol is 1 - 10:60 - 85, the stirring temperature is 20 - 25°C, the stirring time is 5 - 15 min, and the stirring speed is 100 - 200 r / min.

4. The preparation method of a gel electrode for electroencephalogram monitoring according to claim 3, characterized in that: In Step 3, the stirring process is as follows: First, keep it at 45 - 60°C and stir at 100 - 200 r / min for 1.5 - 2 h until the polyvinyl alcohol swells by absorbing water; Then, seal the mixture and let it stand in an oven at 90 - 95°C to dissolve. After complete dissolution, take it out, adjust the stirring temperature to 90 - 95°C, and adjust the rotation speed to 100 - 200 r / min; Finally, seal and let it stand in an oven at 90 - 95°C until the bubbles completely disappear.

5. The preparation method of a gel electrode for EEG monitoring according to claim 4, characterized in that: In Step 4, the conductive dispersion liquid is: a blend polymer of poly(3,4-ethylenedioxythiophene) and polystyrene sulfonate.

6. The preparation method of a gel electrode for electroencephalogram monitoring according to claim 5, characterized in that: The conductive dispersion liquid is added dropwise in batches to make the mixture evenly mixed and without bonding and shaping.

7. The preparation method of a gel electrode for electroencephalogram monitoring according to claim 1 or 6, characterized in that: In Step 4, the stirring temperature is 80 - 95°C, the stirring time is 30 - 45 min, the stirring speed is 100 - 200 r / min, the sealing and standing temperature is 80 - 95°C, and the standing time is 45 - 60 min.

8. The preparation method of a gel electrode for EEG monitoring according to claim 1, characterized in that: In Step 5, the freeze-thaw process is: put it in an environment of -15 - 25°C for 6 - 12 h, then take it out and let it stand at room temperature for 4 - 8 h, and repeat 3 - 5 times.

9. A gel electrode prepared by the method according to any one of claims 1 to 8.

10. The application of the gel electrode according to claim 8 in an electroencephalogram monitoring device.

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