EEG electrode and preparation method thereof

Abstract

The present invention belongs to the technical field of electrophysiological signal detection and provides an EEG electrode and a preparation method thereof. The EEG electrode provided by the present invention comprises a shape memory polymer and a conductive filler. The EEG electrode provided by the present invention is a shape memory electrode, the modulus of which can be changed by the external environment, and has better flexibility of use and wearing comfort. Under the control of the external environment, the EEG electrode provided by the present invention can change its shape, which is conducive to its spreading on the scalp surface, increasing the contact area when collecting signals, reducing contact impedance, and improving the quality of collected signals. In addition, the phase change temperature of the EEG electrode provided by the present invention is adjustable, and the phase change can be driven by external stimuli or by human body temperature alone, which can meet different usage requirements.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrophysiological signal detection, and in particular relates to an electroencephalogram (EEG) electrode and a preparation method thereof. Background Art

[0002] Electroencephalogram (EEG) signals are electrical current signals within the brain measured through the scalp using metal or other conductive materials. The source of this current is primarily the potential changes generated during the stimulation and conduction of nerve cells within the brain. EEG signal acquisition is primarily used in the medical field to detect brain diseases such as Parkinson's disease, epilepsy, narcolepsy, depression, and some neurological movement disorders. In recent years, with the continuous development of acquisition technology, EEG signal acquisition has also found applications in entertainment and computer-related fields.

[0003] Currently, there are two main types of electrodes used in EEG testing: wet electrodes and dry electrodes. Wet electrodes are the most commonly used in EEG testing. They often use gold cup electrodes or Ag / AgCl commercial electrodes. In order to maintain good contact between the electrode and the scalp during the test, conductive gel needs to be applied to the scalp before collection, which is why these electrodes are called wet electrodes. Conductive gel can increase the contact area and reduce impedance, thereby obtaining high-quality signals. However, this collection method also has its drawbacks. First, the use of conductive gel brings trouble to the early preparation and later cleanup of the EEG test. In addition, the conductive gel will gradually lose water during use, which will reduce the signal quality and make long-term monitoring difficult.

[0004] Dry electrodes, which do not require the application of conductive gel during use, effectively avoid the aforementioned issues. They are simple and convenient to use, making them more suitable for long-term testing. However, without the aid of conductive gel, dry electrodes increase contact impedance, making it more difficult to obtain a signal. This contact impedance is primarily caused by the hair and epidermis. To address this, either invasive electrodes are used, piercing the epidermis and entering the dermis to reduce contact impedance, but this can cause damage to the subject's tissue. Alternatively, non-invasive electrodes can be used. Designing a needle-shaped electrode structure allows it to penetrate the hair, while applying a certain amount of pressure to reduce the contact impedance between the epidermis and the electrode, thereby obtaining a better signal. However, the subject still experiences noticeable pain and discomfort at the point of contact. Simply reducing the electrode modulus would cause the electrode to penetrate the hair, increasing the test impedance. Summary of the Invention

[0005] The purpose of the present invention is to provide a shape memory dry electrode made of a composite of a shape memory polymer and a conductive filler and a preparation method thereof, so as to overcome the above-mentioned shortcomings of the existing EEG wet electrodes and dry electrodes.

[0006] To solve the above technical problems, a first aspect of the present invention provides an EEG electrode comprising a shape memory polymer and a conductive filler.

[0007] Preferably, the shape memory polymer is selected from one or more of epoxy resin, polynorbornene, styrene-butadiene copolymer or cross-linked polyethylene shape memory polymers.

[0008] Preferably, the conductive filler is selected from one or more of metal powder, carbon black, metal nanowires or carbon nanotubes.

[0009] Preferably, the shape memory polymer is a composite of bisphenol A epoxy resin monomer and polyetheramine, and the conductive filler is flaky silver powder.

[0010] Preferably, in the shape memory polymer, the mass ratio of the composite of the bisphenol A epoxy resin monomer and polyetheramine to the flaky silver powder is 1:4 to 1:1.

[0011] Preferably, in the composite of the bisphenol A epoxy resin monomer and the polyetheramine, the molecular weight of the bisphenol A epoxy resin monomer is 400 to 600, and the average epoxy value is 0.3 to 0.56; the molecular weight of the polyetheramine is 100 to 10,000; and the molar ratio of the bisphenol A epoxy resin monomer to the polyetheramine is 1:1 to 2:1.

[0012] Preferably, the flake diameter of the silver powder is 0.1 to 1000 μm.

[0013] Preferably, the shape memory polymer is a composite of bisphenol A epoxy resin monomer and polyetheramine, wherein the composite is composed of bisphenol A epoxy resin monomer with a molecular weight of 400 to 600 and polyetheramine with a molecular weight of 400 to 2000 in a molar ratio of 1:1; the conductive filler is flaky silver powder; and the mass ratio of the shape memory polymer to the conductive filler is 1:4 to 2:3.

[0014] More preferably, the shape memory polymer is a composite of bisphenol A epoxy resin monomer and polyetheramine, wherein the composite is composed of bisphenol A epoxy resin monomer with a molecular weight of 450 and polyetheramine with a molecular weight of 400 in a molar ratio of 1:1; the conductive filler is flaky silver powder; and the mass ratio of the shape memory polymer to the conductive filler is 2:3.

[0015] The second aspect of the present invention provides a method for preparing the EEG electrode described in the first aspect, comprising: thoroughly mixing a shape memory polymer with a conductive filler in a molten state, injecting the mixed slurry into a mold for solidification and forming, to obtain the EEG electrode.

[0016] Preferably, the method for preparing the EEG electrode provided by the present invention comprises the following steps:

[0017] (1) heating a bisphenol A epoxy resin monomer with a molecular weight of 450 to a molten state, taking a polyetheramine with a molecular weight of 400, and mixing the bisphenol A epoxy resin monomer and the polyetheramine in a ratio of 1:1;

[0018] Place the mixture in an environment of 20-40°C and stir for 1-10 minutes until the mixture becomes a uniform, transparent, viscous liquid;

[0019] (2) adding flaky silver powder to an alcohol solution containing elemental iodine, and stirring the solution at 20 to 40° C. for 1 to 10 minutes, wherein the mass of the elemental iodine is 1 / 100 to 1 / 300 of the mass of the silver powder;

[0020] (3) filtering and removing the silver powder in step (2), drying it, and then adding it to the viscous liquid obtained in step (1), with the mass ratio of the viscous liquid to the silver powder being 2:3, and grinding it thoroughly to obtain a bright silver mixed slurry;

[0021] (4) The mixed slurry is injected into a mold of the designed electrode structure for curing, and the EEG electrode is obtained by molding, wherein the curing condition is 150° C. for 2 h, and then the temperature is increased by 20° C. and cured for 1 h.

[0022] This invention proposes a shape-memory dry electrode made from a composite of a shape-memory polymer and a conductive filler. Composed of a shape-memory polymer matrix and a conductive filler providing a conductive path, this electrode exhibits minimal discomfort and low contact impedance, allowing for long-term signal acquisition. The EEG electrode provided by this invention also has two distinct features. First, the electrode's modulus changes significantly before and after the glass transition that triggers the shape-memory effect. This allows the electrode to have a higher modulus before contact with the human body, allowing it to penetrate the hair layer. After contact with the human body, the modulus decreases, minimizing discomfort during signal acquisition. Second, shape memory allows the needle-shaped electrode to return to its original design upon reaching the scalp, potentially increasing the contact area between the electrode and the scalp, thereby reducing contact impedance and improving the quality of the acquired signal.

[0023] Compared with the prior art, the EEG electrodes provided by the present invention have the following advantages:

[0024] (1) The shape memory EEG electrode provided by the present invention can change its modulus under the control of the external environment, and has better flexibility of use and wearing comfort.

[0025] (2) The shape memory EEG electrode provided by the present invention can change its shape under the control of the external environment, which is conducive to its spreading on the scalp surface, increasing the contact area when collecting signals, reducing contact impedance, and improving the quality of collected signals.

[0026] (3) The phase change temperature of the shape memory EEG electrode provided by the present invention is adjustable. It can be changed by external stimulation or driven by human body temperature alone, which can meet different usage requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the process for preparing shape memory EEG electrodes in Example 1.

[0028] Figure 2 This is a schematic diagram of the structure of the shape memory EEG electrode prepared in Example 1, wherein Figure 2 -A and 2-B are examples of structures respectively.

[0029] Figure 3 This is the DMA test data of the shape memory EEG electrode prepared in Example 1.

[0030] Figure 4 This is the DMA test data of the shape memory EEG electrode prepared in Example 2.

[0031] Figure 5 This is the DMA test data of the shape memory EEG electrode prepared in Example 3.

[0032] Figure 6 This is the DMA test data of the shape memory EEG electrode prepared in Example 4.

[0033] Figure 7 This is the DMA test data of the shape memory EEG electrode prepared in Example 5.

[0034] Figure 8 This is the contact impedance test data of the shape memory EEG electrode prepared in Example 4.

[0035] Figure 9 Graph showing resistivity test data of the shape memory EEG electrodes prepared in Example 1, Example 6, and Example 7. DETAILED DESCRIPTION

[0036] To more clearly understand the objectives, features, and advantages of the present invention, embodiments of the present invention are described in detail below with reference to the accompanying drawings. Materials used without manufacturer identification are commercially available conventional products. The description of the exemplary embodiments is for illustrative purposes only and is not intended to limit the present invention and its applications.

[0037] EEG electrodes

[0038] A first aspect of the present invention provides an EEG electrode comprising a shape memory polymer and a conductive filler.

[0039] In some embodiments of the present invention, the shape memory polymer is selected from one or more of epoxy resin, polynorbornene, styrene-butadiene copolymer or cross-linked polyethylene shape memory polymers.

[0040] In some embodiments of the present invention, the conductive filler is selected from one or more of metal powder, carbon black, metal nanowires or carbon nanotubes.

[0041] In some embodiments of the present invention, the shape memory polymer is a composite of bisphenol A epoxy resin monomer and polyetheramine, and the conductive filler is flaky silver powder.

[0042] In some embodiments of the present invention, in the shape memory polymer, the mass ratio of the composite of bisphenol A epoxy resin monomer and polyetheramine to the flaky silver powder is 1:4 to 1:1.

[0043] In some embodiments of the present invention, in the composite of bisphenol A epoxy resin monomer and polyetheramine, the molecular weight of the bisphenol A epoxy resin monomer is 400-600, and the average epoxy value is 0.3-0.56; the molecular weight of the polyetheramine is 100-10000; and the amount ratio of the bisphenol A epoxy resin monomer to the polyetheramine is 1:1-2:1.

[0044] In some embodiments of the present invention, the flake silver powder has a diameter of 0.1 to 1000 μm.

[0045] In some embodiments of the present invention, the shape memory polymer is a composite of a bisphenol A epoxy resin monomer and a polyetheramine, wherein the composite is composed of a bisphenol A epoxy resin monomer with a molecular weight of 400 to 600 and a polyetheramine with a molecular weight of 400 to 2000 in a molar ratio of 1:1; the conductive filler is flaky silver powder; and the mass ratio of the shape memory polymer to the conductive filler is 1:4 to 2:3.

[0046] In some embodiments of the present invention, the shape memory polymer is a composite of bisphenol A epoxy resin monomer and polyetheramine, wherein the composite is composed of bisphenol A epoxy resin monomer with a molecular weight of 450 and polyetheramine with a molecular weight of 400 in a molar ratio of 1:1; the conductive filler is flaky silver powder; and the mass ratio of the shape memory polymer to the conductive filler is 2:3.

[0047] Preparation of EEG electrodes

[0048] According to the second aspect of the present invention, an embodiment of the present invention provides a method for preparing the EEG electrode described in the first aspect, comprising: fully mixing the shape memory polymer with the conductive filler in a molten state, injecting the mixed slurry into a mold for solidification and forming, to obtain the EEG electrode.

[0049] In some embodiments of the present invention, the method for preparing an EEG electrode comprises the following steps:

[0050] (1) heating a bisphenol A type epoxy resin monomer with a molecular weight of 450 to a molten state, taking a polyetheramine with a molecular weight of 400, and mixing the bisphenol A type epoxy resin monomer and the polyetheramine in a ratio of 1:1;

[0051] Place the mixture in an environment of 20-40°C and stir for 1-10 minutes until the mixture becomes a uniform, transparent, viscous liquid;

[0052] (2) adding flaky silver powder to an alcohol solution containing elemental iodine, and stirring the solution at 20 to 40° C. for 1 to 10 minutes, wherein the mass of the elemental iodine is 1 / 100 to 1 / 300 of the mass of the silver powder;

[0053] (3) filtering and removing the silver powder in step (2), drying it, and then adding it to the viscous liquid obtained in step (1), with the mass ratio of the viscous liquid to the silver powder being 2:3, and grinding it thoroughly to obtain a bright silver mixed slurry;

[0054] (4) The mixed slurry is injected into a mold of the designed electrode structure for curing, and the EEG electrode is obtained by molding, wherein the curing condition is 150° C. for 2 h, and then the temperature is increased by 20° C. and cured for 1 h.

[0055] Example

[0056] The advantages of the present application are further illustrated below with reference to specific examples and comparative examples. Materials used without manufacturer designation are conventional products that can be purchased commercially. It should be understood that these examples are intended only to illustrate the present application and are not intended to limit the scope of the present application.

[0057] Example 1

[0058] (1) Take out bisphenol A epoxy resin monomer with a molecular weight of 450 and heat it in a water bath at 60°C until its fluidity is significantly improved.

[0059] (2) Take an appropriate amount of polyetheramine with a molecular weight of 400, and mix the two substances in a ratio of 1.5 between the bisphenol A epoxy resin monomer and the polyetheramine.

[0060] (3) The mixture obtained in step (2) was placed in an environment of 30° C. and stirred for 5 min until the mixture became a uniform, transparent, viscous liquid.

[0061] (4) Weigh an appropriate amount of flaky silver powder, add it to an alcohol solution containing elemental iodine, and stir the solution at 30°C for 2 minutes, wherein the mass of elemental iodine in the alcohol solution is 1 / 200 of the mass of the silver powder.

[0062] (5) The silver powder in step (4) was filtered out and dried, and then the silver powder was added to the transparent viscous liquid obtained in step (3) and fully ground for 20 minutes to obtain a bright silver mixed slurry, wherein the mass ratio of the liquid to the silver powder was 0.67.

[0063] (6) The slurry is injected into a mold of the designed electrode structure and cured, and the desired electrode is obtained by molding. The curing conditions are 150°C for 2 hours, and then the temperature is increased by 20°C and cured for 1 hour to prepare the EEG electrode.

[0064] like Figure 1 FIG. 1 is a schematic diagram of the process for preparing shape memory EEG electrodes in Example 1. Figure 2 This is a schematic diagram of the structure of the shape memory EEG electrode prepared in Example 1. It should be noted that Figure 2 -A and 2-B are examples of structures respectively. The actual structure of the EEG electrode provided by the present invention can be varied and is not limited to Figure 2 The structure shown.

[0065] Example 2

[0066] The raw materials and steps for the preparation of Example 2 are mostly the same as those of Example 1, with the only difference being that the molecular weight of the polyetheramine used in step (2) is 2000.

[0067] Example 3

[0068] The raw materials and steps for the preparation of Example 3 are mostly the same as those of Example 1, with the only difference being that the molecular weight of the polyetheramine used in step (2) is 100.

[0069] Example 4

[0070] The raw materials and steps for the preparation of Example 4 are mostly the same as those of Example 1, with the only difference being that the ratio of the amount of bisphenol A epoxy resin monomer to the amount of polyetheramine in step (3) is 1.0.

[0071] Example 5

[0072] The raw materials and steps for the preparation of Example 5 are mostly the same as those of Example 1, with the only difference being that the ratio of the amount of bisphenol A epoxy resin monomer to the amount of polyetheramine in step (3) is 2.0.

[0073] Example 6

[0074] The raw materials and steps for the preparation of Example 6 are mostly the same as those of Example 1, with the only difference being that the mass ratio of the viscous liquid to the silver powder in step (5) is 0.25.

[0075] Example 7

[0076] The raw materials and steps for the preparation of Example 7 are mostly the same as those of Example 1, with the only difference being that the mass ratio of the viscous liquid to the silver powder in step (5) is 2.0.

[0077] EEG electrode performance test

[0078] 1. DMA test of electrode

[0079] (1) Take the EEG electrode prepared in the above embodiment and make it into a bone shape using a mold.

[0080] (2) DMA testing was performed using a TA Q200 device in film stretching mode with a temperature range of -20°C to 80°C, a heating rate of 5°C / min, and a stretching frequency of 1 Hz.

[0081] Figures 3 to 7 These are the DMA test data of the shape memory EEG electrodes prepared in Examples 1 to 5. Figure 5 It can be seen that the phase transition temperature of the EEG electrode prepared in Example 4 is 33° C., which is close to the human body temperature, and thus the phase transition can be driven by the human body temperature.

[0082] 2. Electrode contact impedance test

[0083] (1) Take the EEG electrodes prepared in the above embodiment, two in a group, and attach them to human skin that has been cleaned with alcohol, with a distance of 2 cm between the two electrodes.

[0084] (2) Using a Keithley LCR source meter, the contact impedance was tested under the condition that the AC voltage amplitude was 1V and the AC frequency ranged from 20Hz to 1000Hz.

[0085] Figure 8 This is the contact impedance test data of the shape memory EEG electrode prepared in Example 4.

[0086] 3. Electrode resistivity test

[0087] The EEG electrodes prepared in the above examples were made into rectangular films with a width of 5 mm, a length of 2 cm, and a thickness of 1 mm, and their resistivity was tested using a Shanghai Qianfeng SB100A / 2 four-probe tester.

[0088] Figure 9 Graph showing resistivity test data of the shape memory EEG electrodes prepared in Example 1, Example 6, and Example 7.

[0089] The above test data show that the EEG electrodes provided by the present invention can change their modulus and, therefore, their shape under control of the external environment, which is beneficial for spreading them on the scalp surface, increasing the contact area when collecting signals, reducing contact impedance, and improving the quality of collected signals.

[0090] The above examples are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.

Claims

1. An electroencephalogram electrode, characterized in that: including shape memory polymers and conductive fillers; The shape memory polymer is a compound of bisphenol A epoxy resin monomer and polyetheramine, and the conductive filler is flaky silver powder; the mass ratio of the compound of bisphenol A epoxy resin monomer and polyetheramine to the flaky silver powder is 1:4 to 1:1; In the composite of the bisphenol A epoxy resin monomer and the polyetheramine, the molecular weight of the bisphenol A epoxy resin monomer is 400 to 600, and the average epoxy value is 0.3 to 0.56; the molecular weight of the polyetheramine is 100 to 10,000; and the molar ratio of the bisphenol A epoxy resin monomer to the polyetheramine is 1:1 to 2:

1.

2. The EEG electrode according to claim 1, characterized in that The flake diameter of the flaky silver powder is 0.1 to 1000 μm.

3. The EEG electrode according to claim 1, characterized in that The shape memory polymer is a compound of bisphenol A epoxy resin monomer and polyetheramine, wherein the compound is composed of bisphenol A epoxy resin monomer with a molecular weight of 400 to 600 and polyetheramine with a molecular weight of 400 to 2000 in a molar ratio of 1:1; The conductive filler is flaky silver powder; The mass ratio of the shape memory polymer to the conductive filler is 1:4 to 2:

3.

4. The EEG electrode according to claim 3, characterized in that The shape memory polymer is a compound of bisphenol A epoxy resin monomer and polyetheramine, wherein the compound is composed of bisphenol A epoxy resin monomer with a molecular weight of 450 and polyetheramine with a molecular weight of 400 in a molar ratio of 1:1; The conductive filler is flaky silver powder; The mass ratio of the shape memory polymer to the conductive filler is 2:

3.

5. The method for preparing an EEG electrode according to any one of claims 1 to 4, characterized in that: include: The shape memory polymer is fully mixed with the conductive filler in a molten state, and the mixed slurry is injected into a mold for solidification and molding to obtain an EEG electrode.

6. The method for preparing an EEG electrode according to claim 5, characterized in that: The steps include: (1) heating a bisphenol A epoxy resin monomer with a molecular weight of 450 to a molten state, taking a polyetheramine with a molecular weight of 400, and mixing the bisphenol A epoxy resin monomer and the polyetheramine in a ratio of 1:1; placing the mixture in an environment of 20 to 40° C. and stirring for 1 to 10 minutes until the mixture becomes a uniform, transparent, viscous liquid; (2) adding flaky silver powder to an alcohol solution containing elemental iodine, and stirring the solution at 20 to 40° C. for 1 to 10 minutes, wherein the mass of the elemental iodine is 1 / 100 to 1 / 300 of the mass of the silver powder; (3) filtering and removing the silver powder in step (2), drying it, and then adding it to the viscous liquid obtained in step (1), with the mass ratio of the viscous liquid to the silver powder being 2:3, and grinding it thoroughly to obtain a bright silver mixed slurry; (4) The mixed slurry is injected into a mold of the designed electrode structure for curing, and the EEG electrode is obtained by molding, wherein the curing condition is 150° C. for 2 h, and then the temperature is increased by 20° C. and cured for 1 h.

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