Natural polymer gel electrode for electroencephalogram detection and preparation method and device thereof

Abstract

This invention relates to the technical field of brain-computer interfaces and bioelectrical signal detection, and discloses a natural polymer gel electrode for electroencephalogram (EEG) detection, its preparation method, and apparatus. By mass fraction, the gel electrode comprises the following components: 2-15 parts natural polymer, 15-50 parts moisturizing agent, 50-85 parts water, 0.05-1 part preservative, and 1-8 parts conductive agent. The natural polymer is component A and component B in a mass ratio of 1-7:1. The moisturizing agent is glycerol, erythritol, and sorbitol in a mass ratio of 1-3:1-3:1. This invention, through adjusting the types and proportions of natural polymers and moisturizing agents, yields a novel gel electrode that combines high biocompatibility, high compressive strength, long-term moisturization under dry conditions, low impedance, and stable conductivity, thus promoting the development of long-term wearable brain-computer interface technology.

Description

Technical Field

[0001] This invention relates to the technical field of brain-computer interfaces and bioelectrical signal detection, and in particular to natural polymer gel electrodes for electroencephalography (EEG) detection, as well as their preparation methods and devices. Background Technology

[0002] Electroencephalography (EEG) signals are a comprehensive reflection of the electrical activity of neurons in the brain on the scalp surface, and are widely used in clinical diagnosis, neuroscience research, and brain-computer interface (BCI) systems. As a key component for signal acquisition, the performance of the electrodes directly determines the signal quality and system stability.

[0003] Currently, mainstream EEG electrodes include wet electrodes, dry electrodes, and hydrogel electrodes. Wet electrodes, such as Ag / AgCl electrodes, require the use of conductive gel. They offer low impedance and high signal quality, making them the clinical "gold standard." However, the conductive gel dries easily, leading to increased impedance and signal attenuation. It can also cause skin allergies and is difficult to clean, making it unsuitable for long-term monitoring. Dry electrodes do not require conductive gel and are convenient to use, but they have high contact impedance and are susceptible to motion artifacts, especially exhibiting poor signal quality in hairy areas. Hydrogel electrodes combine the advantages of wet and dry electrodes, but existing products are mostly based on synthetic polymers (such as polyacrylic acid and PVA). For example, invention patent CN116763318 A discloses a gel layer and an implantable flexible brain-computer interface electrode incorporating this gel layer. The gel layer is formed by curing a liquid-phase prepolymer under ultraviolet light. The prepolymer includes monomers, crosslinking agents, photoinitiators, solvents, surfactants, humectants, and adhesion promoters. The monomer is hydroxyethyl methacrylate. However, the polyacrylic acid polymer used in this patent as the gel layer material has problems such as poor biocompatibility, easy water loss or excessive water absorption, and skin irritation from degradation products, making it difficult to meet the needs of long-term wear.

[0004] Natural polymer hydrogels exhibit good biocompatibility and low impedance upon contact with human skin. However, existing natural polymer hydrogel electrodes have a short lifespan; even with the addition of moisturizing ingredients, the actual usage time remains below 4 hours. Current natural polymer hydrogels also have low compressive strength, making them prone to flattening, collapsing, or breaking under pressure and dehydration during use, thus affecting their usability. Furthermore, current natural polymer hydrogels experience rapid water loss and weight reduction, limiting their usability to only half an hour in extremely dry environments, and their impedance increases linearly over time.

[0005] Therefore, there is an urgent need for a new type of EEG electrode or improved solution that combines high biocompatibility, high compressive strength, long-term moisture retention in dry environments, low impedance, and stable conductivity to promote the development of long-term wearable brain-computer interface technology. Summary of the Invention

[0006] To address the problems of poor biocompatibility, low compressive strength, insufficient moisture retention in dry environments, poor signal stability, and short service life in existing technologies, this invention provides a natural polymer gel electrode for electroencephalography (EEG) detection, along with its preparation method and apparatus. By adjusting the types and proportions of natural polymers and moisturizing components, a novel gel electrode is obtained that combines high biocompatibility, high compressive strength, long-term moisture retention in dry environments, low impedance, and stable conductivity, thus promoting the development of long-term wearable brain-computer interface technology.

[0007] The objective of this invention is achieved through the following technical solution: In a first aspect, the present invention provides a natural polymer gel electrode for electroencephalography (EEG) detection. The gel electrode, by mass fraction, comprises the following components: 2-15 parts natural polymer, 15-50 parts moisturizing agent, 50-85 parts water, 0.05-1 part preservative, and 1-8 parts conductive agent. The natural polymer is component A and component B in a mass ratio of 1-7:1. Component A includes at least one of red algae gum, carrageenan, tamarind gum, cassia gum, and chitosan. Component B includes at least one of konjac gum, xanthan gum, guar gum, gellan gum, and casein. The moisturizing agent is glycerol, erythritol, and sorbitol in a mass ratio of 1-3:1-3:1.

[0008] The gel electrode in this invention uses a natural polymer matrix, which is non-toxic, non-irritating, and biocompatible, suitable for long-term skin contact. It utilizes moisturizing ingredients in conjunction with a three-dimensional network to lock in moisture, resulting in good moisturizing stability. By adjusting the types and proportions of natural polymers and moisturizing ingredients, it exhibits excellent mechanical properties, low impedance, and stable conductivity. If the content of natural polymers is too low, the gel will lack mechanical strength and fail to maintain its shape; if the content is too high, the gel will be too hard, affecting its adhesion to the skin. If the content of moisturizing ingredients is too low, the moisturizing effect will be poor, and the gel will easily lose water and crack; if the content is too high, the gel will be too soft and may lead to overhydration of the skin. If the content of conductive ingredients is too low, the conductivity will be insufficient, resulting in excessive impedance; if the content is too high, it may affect the mechanical properties and biocompatibility of the gel.

[0009] In addition, the natural polymer is formulated using a combination of components A and B. Component A is mainly a polysaccharide gel with excellent biocompatibility; however, gels formed from component A alone have low strength, are prone to deformation and collapse under pressure, have a high water loss rate, and poor moisturizing stability. Component B works synergistically with component A. The compliant chains of component A act as a molecular base, interspersed between the rigid chains of component B, alleviating the problem of excessive rigidity and brittleness when component B is used alone, thus giving the gel both strength and toughness. Simultaneously, components A and B are cross-linked through ionic and hydrogen bonds, forming a dense and stable gel network framework, improving the compressive strength of the gel matrix and regulating hardness and elasticity. The gel network framework obtained by combining components A and B in a certain proportion has abundant hydrophilic groups, providing more binding sites for moisturizing ingredients. This not only strengthens the basic water retention capacity, better locks in moisture, and delays water loss, but also further reduces the contact impedance between the gel surface and the skin, improving signal acquisition stability. The moisturizing ingredients are a combination of glycerol, erythritol, and sorbitol. Glycerol, a small-molecule alcohol, can quickly penetrate the gaps in the gel network; erythritol, a medium-molecule alcohol, and sorbitol, a large-molecule alcohol, together provide deep hydration and long-lasting moisture retention. When combined, the moisturizing ingredients are better dispersed in the natural polymeric gel network, resulting in a significantly higher moisturizing efficiency than a single moisturizing ingredient. Furthermore, excessive amounts of moisturizing ingredients do not cause gel softening or decreased strength, achieving a balance between moisturizing and mechanical properties.

[0010] Preferably, the material of the gel electrode further includes 0.5-2 parts of a reinforcing component; the reinforcing component includes one or more of fumed SiO2, mica and silica fume; the particle size of the reinforcing component is 1-50 μm.

[0011] Adding powdered substances can increase the compressive strength of the gel, and its internal nanopores (2-10 nm) can adsorb free water, forming a "capillary reservoir" that can reduce water loss. However, adding too much reinforcing material can lead to increased gel brittleness and resistance.

[0012] Preferably, the preservative includes one or more of potassium sorbate, sodium benzoate, and Kathon.

[0013] Preferably, the conductive component includes one or more of sodium chloride, potassium chloride, calcium chloride, Ag / AgCl conductive micro powder, silver nanowires, poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), poly(2-acrylamide-2-methyl-1-propanesulfonic acid), and phosphates (disodium hydrogen phosphate, potassium dihydrogen phosphate, or phosphate buffer).

[0014] Secondly, the present invention provides a method for preparing a natural polymeric gel electrode for electroencephalography (EEG) detection, comprising the following steps: (a) The moisturizing ingredients, preservatives, conductive ingredients and water are stirred and dissolved to obtain mixture A; (b) Add natural polymer to mixture A, heat and stir to obtain sol B; (c) After degassing, sol B is injected into a mold; after cooling and molding at room temperature, it is demolded to obtain a cavity-free gel or a cavity-containing gel, wherein the cavity is a hollow structure with at least one side exposed. (d) The gel is refrigerated and solidified to obtain a gel electrode.

[0015] Preferably, step (a) includes the following steps: premixing the reinforcing ingredient and a portion of the moisturizing ingredient to obtain a premix; adding the remaining moisturizing ingredient, preservative, conductive ingredient and water to the premix, stirring to dissolve, to obtain mixture A.

[0016] Preferably, in step (b), the heating and stirring temperature is 85-100℃, the stirring speed is 600-800rpm, and the time is 2-30min.

[0017] Preferably, in step (c), the defoaming method includes vacuum defoaming or ultrasonic treatment.

[0018] Preferably, in step (d), the temperature for cold curing is 2-8°C and the cold curing time is 12-72h.

[0019] Preferably, in step (c), the mold includes a base platform and a cavity injection head disposed above the base platform; the base platform has a groove in the middle; one end of the cavity injection head is connected to the base platform and can be raised and lowered through the connection end; the cavity injection head has a protruding part; after the cavity injection head descends, the other end of the cavity injection head contacts the base platform, and the part of the protruding part that extends beyond the cavity injection head can extend into the groove of the base platform, and the surface of the protruding part in the groove forms a cavity in the gel.

[0020] Preferably, the groove is conical, cylindrical, conical, or hemispherical; the cavity is conical, cylindrical, conical, or hemispherical.

[0021] Preferably, the method for pre-storing conductive liquid in the gel electrode includes the following steps: When the gel electrode has no cavity, conductive liquid is injected immediately after the defoamed sol B is injected into the mold. After cooling and molding at room temperature, the gel is demolded to obtain a cavity-free gel with pre-stored conductive liquid; the gel is then cryogenically cured to obtain a cavity-free gel electrode with pre-stored conductive liquid. When the gel electrode contains a cavity, the gel containing the cavity is cryogenically cured, conductive liquid is injected into the cavity, and the electrode is sealed to obtain a cavity-containing gel electrode with pre-stored conductive liquid.

[0022] Preferably, the conductive liquid is a solution containing one or more conductive components such as potassium chloride, sodium chloride, and calcium chloride.

[0023] Thirdly, the present invention provides an apparatus for assembling a gel electrode, the apparatus comprising a liquid storage chamber, a delivery module, a gel electrode, and a signal transmission module; the liquid storage chamber is connected through the delivery module and a plurality of micropores provided on the delivery module on the surface in contact with the gel electrode; both the liquid storage chamber and the delivery module contain conductive liquid; the delivery module is further provided with a signal transmission module between the surfaces in contact with the gel electrode.

[0024] Preferably, a sustained-release membrane is provided between the micropores and the gel electrode; the sustained-release membrane is a one-way permeable membrane facing the gel electrode.

[0025] Compared with the prior art, the present invention has the following beneficial effects: (1) The gel electrode uses a natural polymer matrix, which is non-toxic and non-irritating, has good biocompatibility, and is suitable for long-term skin contact. It uses moisturizing ingredients in conjunction with a three-dimensional network to lock in water, and has good moisturizing stability. By adjusting the types and proportions of natural polymers and moisturizing ingredients, it exhibits good mechanical properties, low impedance and stable conductivity. (2) All components are natural biodegradable materials, the preparation process is green and mild, and there are no pollutant emissions; at the same time, by adjusting the component ratio, the hardness, elasticity and water content of the gel can be precisely controlled, which can be adapted to different EEG detection scenarios such as hair area, sensitive skin and long-term dynamic monitoring, and promote the practical application of long-term wearable brain-computer interface technology. (3) The provided mold and pre-stored conductive liquid solution expands the possibilities for gel electrodes; the provided device solution provides solutions for the replenishment source, liquid addition method, how to store liquid, how to transport, how to release conductive liquid, contact method and how to conduct signal transmission of gel or other materials that require conductive liquid to assist in the conduction of scalp signals. Attached Figure Description

[0026] Figure 1 The diagram shows the structure of the mold and the cavity-free gel electrode in Examples 3 and 4.

[0027] Figure 2 This is a schematic diagram of the mold and the cavity gel electrode in Example 1.

[0028] Figure 3 This is a schematic diagram of the mold and the cavity gel electrode in Example 2.

[0029] Figure 4 This is a schematic diagram of the device assembled with cavity-free gel electrodes in Examples 3 and 4.

[0030] Figure 5 This is a schematic diagram of the device with a cavity gel electrode assembled in Example 2.

[0031] Figure 6 This is a schematic diagram of the device with a cavity gel electrode assembled in Example 1.

[0032] Figure 7 This is a schematic diagram of the liquid storage tank.

[0033] The attached diagram is labeled as follows: 1. Base platform; 2. Cavity injection head; 2-1. Protruding component; 3. Gel electrode; 3-1. Cavity; 4. Liquid storage chamber; 4-1. Liquid replenishment port; 5. Delivery module; 5-1. Micropore; 6. Slow-release membrane; 7. Signal transmission module; 8. Liquid storage tank; 8-1. Cap; 8-2. Liquid filling port; 8-3. Interface; 9. Conductive liquid. Detailed Implementation

[0034] The technical solution of the present invention will be illustrated below with specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0035] The mold for preparing the gel electrode in this invention includes a base platform 1 and a cavity injection head 2 disposed above the base platform 1. For example... Figures 1-3 As shown, the base platform 1 has a groove in the middle, which can be conical, cylindrical, conical, hemispherical, or other irregular shapes. Figures 1-3 The groove shape is cylindrical at the top and hemispherical at the bottom. This groove shape forms the overall shape of the gel electrode 3, and the specific shape can be customized. One end of the cavity injection head 2 is connected to the base platform 1 via a structural component, and its lifting and lowering are achieved through the connection end. The other end of the cavity injection head 2 contacts the base platform 1 but is not connected. The cavity injection head 2 includes a crossbeam and a protruding component 2-1 connected to the crossbeam. After the cavity injection head 2 descends, the other end of the cavity injection head 2 contacts the base platform 1, and the portion of the protruding component 2-1 extending beyond the cavity injection head 2 can extend into the groove of the base platform 1. The surface of the protruding component in the groove forms the cavity 3-1 in the gel. The portion of the protruding component 2-1 extending beyond the cavity injection head 2 is the shape of the cavity 3-1 of the gel electrode 3. The cavity 3-1 can be conical, cylindrical, hemispherical, or other irregular shapes, etc. Figure 2 The cavity 3-1 in the middle is spherical in shape; Figure 3 The cavity 3-1 in the middle is a combination of a sphere and several protruding shapes on the spherical surface.

[0036] The specific implementation method of the above mold is as follows: When the cavity injection head 2 has not descended, the part of the protruding part 2-1 that extends beyond the cavity injection head 2 has not entered the groove of the base platform 1. At this time, the defoamed sol B is injected into the groove of the base platform 1, cooled and shaped, and then demolded to obtain a cavity-free gel. The defoamed sol B is injected into the groove of the base platform 1, and then conductive liquid is injected. After cooling and shaped, it is demolded to obtain a cavity-free gel with pre-stored conductive liquid. After the cavity injection head 2 descends, the other end of the cavity injection head 2 contacts the base platform 1, and the part of the protruding part 2-1 that extends beyond the cavity injection head 2 can enter the groove of the base platform 1. At this time, the defoamed sol B is injected into the groove of the base platform 1, cooled and shaped, and then demolded to obtain a gel containing a cavity. The surface of the protruding part 2-1 in the groove forms the cavity 3-1 in the gel.

[0037] The device for assembling the gel electrode in this invention includes a liquid storage chamber, a delivery module, a gel electrode, a sustained-release membrane, and a signal transmission module. For example... Figures 4-6 As shown, the liquid storage chamber 4 and the delivery module 5 are in contact and connected, and both contain conductive liquid 9. The liquid storage chamber 4 can be circular, tubular, or other closed or semi-closed cavities capable of storing or containing liquid, allowing for temporary or long-term storage of liquid within the cavity. The outer surface of the cavity protrudes outward from one side of the main body to form an accumulation body. The top of this accumulation body has a liquid replenishment port 4-1 that can be closed or not, and the replenishment port 4-1 is connected to the internal cavity. The delivery module 5 is a channel connecting the liquid storage chamber and the gel electrode, as well as a channel for delivering the conductive liquid 9. It is a container or several pipes capable of containing the conductive liquid 9, and the delivery module 5 has several micropores 5-1 on the surface in contact with the gel electrode 3. The delivery module 5 and the gel electrode 3 are connected through the micropores 5-1. A slow-release membrane 6 can also be provided between the micropores 5-1 and the gel electrode 3. The slow-release membrane 6 is a one-way permeable membrane facing the gel electrode 3, such as PMND (PMND is a one-way permeable membrane). When the delivery module 5 is filled with conductive liquid 9, the liquid can permeate through the micropores 5-1 to the gel electrode 3 or permeate through the slow-release membrane 6 and then to the gel electrode 3. At this time, the gel electrode 3 can be slowly wetted, thereby increasing the service life of the gel electrode 3. The micropores 5-1 can exist at any position on the contact surface between the delivery module 5 and the gel electrode 3, with the purpose of allowing the conductive liquid 9 to flow out or slowly seep out.

[0038] The delivery module 5 also includes a signal transmission module 7 between its contact surface with the gel electrode 3. The position of the signal transmission module 7 does not coincide with the micropore 5-1. The signal transmission module 7 is generally a silver / silver chloride electrode or an electrode coated with silver / silver chloride. The electrode may be made of materials including, but not limited to, gold, copper, rubber, silicone polymers, or conductive graphite. Silicone polymers may include materials such as polydimethylsiloxane.

[0039] In addition, a movable or fixed liquid storage tank 8, equipped with a pressurization device, can be installed independently of the aforementioned device to replenish the conductive liquid 9 to the gel electrode device at any time. Figure 7 As shown, the top of the liquid storage tank 8 is provided with a liquid inlet 8-2, which is sealed by a cap 8-1. The cap 8-1 can be connected to the liquid inlet 8-2 by a screw, snap, or other method used for sealing bottle mouths. The bottom of the liquid storage tank 8 is provided with one or more interfaces 8-3. The gel electrode device is connected to the liquid storage tank 8 through the interfaces 8-3. The interfaces 8-3 can be connected by snap fasteners or other components with spring structures or elastic fixation. The liquid storage tank 8 can also be an injection device, which replenishes the liquid by drawing in the conductive liquid 9 and then injecting it into the liquid storage chamber 4 through the replenishment port 4-1 of the gel electrode device.

[0040] In specific embodiments of the present invention, the conductive liquid used is a sodium chloride solution. The particle size of the reinforcing component is 1-5 μm.

[0041] Example 1 The gel electrode material, by weight, comprises the following components: 4.5 parts natural polymer, 30 parts moisturizing agent, 70.5 parts deionized water, 0.1 parts preservative (sodium benzoate), 2 parts conductive agent (potassium chloride), and 1 part reinforcing agent (gas-phase SiO2). The natural polymer consists of red algae gum and gellan gum in a weight ratio of 3.5:1, and the moisturizing agent consists of glycerol, erythritol, and sorbitol in a weight ratio of 1:1:1.

[0042] The preparation method of the above-mentioned gel electrode includes the following steps: (a) Mix 5 parts glycerol, 5 parts erythritol, 5 parts sorbitol and 1 part reinforcing component (gas phase SiO2) and stir for 3 min to obtain a premix; add 5 parts glycerol, 5 parts erythritol, 5 parts sorbitol, 2 parts conductive component (potassium chloride), 0.1 part preservative (sodium benzoate) and 70.5 parts deionized water to the premix and stir at room temperature until completely dissolved to obtain mixture A; (b) Add 3.5 parts of red algae gum and 1 part of gellan gum to mixture A, heat to 95°C and stir at high speed at 600 rpm for 30 min to obtain sol B; (c) After vacuum degassing of sol B, inject as follows: Figure 2 In the mold shown; after cooling and molding at room temperature, the gel with cavities is obtained by demolding. (d) Place at 5℃ for 48 hours to complete curing, resulting in the following: Figure 2 The cavity-containing gel electrode shown can be paired with, for example... Figure 6 The device shown is used.

[0043] Example 2 The gel electrode material, by weight, comprises the following components: 4.5 parts natural polymer, 30 parts moisturizing agent, 70.5 parts deionized water, 0.1 parts preservative (sodium benzoate), 2 parts conductive agent (potassium chloride), and 1 part reinforcing agent (gas-phase SiO2). The natural polymer consists of red algae gum and gellan gum in a weight ratio of 3.5:1, and the moisturizing agent consists of glycerol, erythritol, and sorbitol in a weight ratio of 1:1:1.

[0044] The preparation method of the above-mentioned gel electrode includes the following steps: (a) Mix 5 parts glycerol, 5 parts erythritol, 5 parts sorbitol and 1 part reinforcing component (gas phase SiO2) and stir for 3 min to obtain a premix; add 5 parts glycerol, 5 parts erythritol, 5 parts sorbitol, 2 parts conductive component (potassium chloride), 0.1 part preservative (sodium benzoate) and 70.5 parts deionized water to the premix and stir at room temperature until completely dissolved to obtain mixture A; (b) Add 3.5 parts of red algae gum and 1 part of gellan gum to mixture A, heat to 95°C and stir at high speed at 600 rpm for 30 min to obtain sol B; (c) After vacuum degassing of sol B, inject as follows: Figure 3 In the mold shown; after cooling and molding at room temperature, the gel with cavities is obtained by demolding. (d) Place at 5℃ for 48 hours to complete curing, resulting in the following: Figure 3 The cavity-containing gel electrode shown is used; after injecting conductive liquid into the cavity using an injection device, it is sealed and can be used with, for example... Figure 5 The device shown is used.

[0045] Example 3 The gel electrode material, by weight, comprises the following components: 4.5 parts natural polymer, 30 parts moisturizing agent, 70.5 parts deionized water, 0.1 parts preservative (sodium benzoate), 1.5 parts conductive agent (PEDOT:PSS), and 1 part reinforcing agent (vaporized SiO2). The natural polymer is red algae gum and gellan gum in a weight ratio of 3.5:1, and the moisturizing agent is glycerol, erythritol, and sorbitol in a weight ratio of 1:1:1.

[0046] The preparation method of the above-mentioned gel electrode includes the following steps: (a) Mix 5 parts glycerol, 5 parts erythritol, 5 parts sorbitol and 1 part reinforcing component (gas phase SiO2) and stir for 3 min to obtain a premix; add 5 parts glycerol, 5 parts erythritol, 5 parts sorbitol, 1.5 parts conductive component (PEDOT:PSS), 0.1 parts preservative (sodium benzoate) and 70.5 parts deionized water to the premix and stir at room temperature until completely dissolved to obtain mixture A; (b) Add 3.5 parts of red algae gum and 1 part of gellan gum to mixture A, heat to 95°C and stir at high speed at 600 rpm for 30 min to obtain sol B; (c) After vacuum degassing of sol B, inject as follows: Figure 1 In the mold shown; after cooling and molding at room temperature, the gel is demolded to obtain a cavity-free gel; (d) Place at 5℃ for 48 hours to complete curing, resulting in the following: Figure 1 The gel electrode shown can be paired with, for example... Figure 4 The device shown is used.

[0047] Example 4 The gel electrode material comprises the following components by weight: 4.5 parts natural polymer, 30 parts moisturizing ingredient, 70.5 parts deionized water, 0.1 parts preservative (potassium sorbate), and 1.5 parts conductive ingredient (PEDOT:PSS). The natural polymer is red algae gum and gellan gum in a weight ratio of 3.5:1, and the moisturizing ingredient is glycerol, erythritol, and sorbitol in a weight ratio of 1:1:1.

[0048] The preparation method of the above-mentioned gel electrode includes the following steps: (a) Add 10 parts glycerol, 10 parts erythritol, 10 parts sorbitol, 1.5 parts conductive component (PEDOT:PSS), 0.1 parts preservative (potassium sorbate) and 70.5 parts deionized water to the premix and stir at room temperature until completely dissolved to obtain mixture A; (b) Add 3.5 parts of red algae gum and 1 part of gellan gum to mixture A, heat to 95°C and stir at high speed at 600 rpm for 30 min to obtain sol B; (c) After vacuum degassing of sol B, inject as follows: Figure 1 Conductive liquid is injected into the mold shown using an injection device; after cooling and solidification at room temperature, the mold is demolded to obtain a cavity-free gel. (d) Place at 5℃ for 48 hours to complete curing, resulting in the following: Figure 1 The gel electrode shown can be paired with, for example... Figure 4 The device shown is used.

[0049] Example 5 The gel electrode material, by weight, comprises the following components: 12 parts natural polymer, 50 parts moisturizing agent, 82 parts deionized water, 0.1 parts preservative (sodium benzoate), 4 parts conductive agent (potassium chloride), and 1.5 parts reinforcing agent (gas-phase SiO2). The natural polymer is carrageenan and casein in a 5:1 weight ratio, and the moisturizing agent is glycerol, erythritol, and sorbitol in a 2:2:1 weight ratio.

[0050] The preparation method of the above-mentioned gel electrode includes the following steps: (a) Mix 10 parts glycerol, 10 parts erythritol, 5 parts sorbitol and 1.5 parts reinforcing component (gas phase SiO2) and stir for 3 min to obtain a premix; add 10 parts glycerol, 10 parts erythritol, 5 parts sorbitol, 4 parts conductive component (PEDOT:PSS), 0.1 parts preservative (sodium benzoate) and 82 parts deionized water to the premix and stir at room temperature until completely dissolved to obtain mixture A; (b) Add 10 parts carrageenan and 2 parts casein to mixture A, heat to 95°C and stir at high speed at 800 rpm for 30 min to obtain sol B; (c) After vacuum degassing of sol B, inject as follows: Figure 1 In the mold shown; after cooling and molding at room temperature, the gel is demolded to obtain a cavity-free gel; (d) Place at 5℃ for 48 hours to complete curing, resulting in the following: Figure 1 The gel electrode shown can be paired with, for example... Figure 4 The device shown is used.

[0051] Example 6 The gel electrode material, by weight, comprises the following components: 5 parts natural polymer, 30 parts moisturizing agent, 70.5 parts deionized water, 0.1 parts preservative (sodium benzoate), 2 parts conductive agent (potassium chloride), and 1 part reinforcing agent (gas-phase SiO2). The natural polymer is chitosan and konjac gum in a 4:1 weight ratio, and the moisturizing agent is glycerol, erythritol, and sorbitol in a 1:1:1 weight ratio.

[0052] The preparation method of the above-mentioned gel electrode includes the following steps: (a) Mix 5 parts glycerol, 5 parts erythritol, 5 parts sorbitol and 1 part reinforcing component (gas phase SiO2) and stir for 3 min to obtain a premix; add 5 parts glycerol, 5 parts erythritol, 5 parts sorbitol, 1.5 parts conductive component (PEDOT:PSS), 0.1 parts preservative (sodium benzoate) and 70.5 parts deionized water to the premix and stir at room temperature until completely dissolved to obtain mixture A; (b) Add 4 parts chitosan and 1 part konjac gum to mixture A, heat to 95°C and stir at high speed at 600 rpm for 30 min to obtain sol B; (c) After vacuum degassing of sol B, inject as follows: Figure 1 In the mold shown; after cooling and molding at room temperature, the gel is demolded to obtain a cavity-free gel; (d) Place at 5℃ for 48 hours to complete curing, resulting in the following: Figure 1 The gel electrode shown can be paired with, for example... Figure 4 The device shown is used.

[0053] Comparative Example 1 The only difference from Example 1 is that the natural polymer is red algae gum and gellan gum in a mass ratio of 1:3.5.

[0054] Specifically, by weight, the gel electrode material comprises the following components: 4.5 parts natural polymer, 30 parts moisturizing agent, 70.5 parts deionized water, 0.1 parts preservative (sodium benzoate), 2 parts conductive agent (potassium chloride), and 1 part reinforcing agent (gas-phase SiO2). The natural polymer consists of red algae gum and gellan gum in a weight ratio of 1:3.5, and the moisturizing agent consists of glycerol, erythritol, and sorbitol in a weight ratio of 1:1:1.

[0055] Comparative Example 2 The only difference from Example 1 is that the natural polymers are gelatin and gellan gum in a mass ratio of 3.5:1.

[0056] Specifically, by weight, the gel electrode material comprises the following components: 4.5 parts natural polymer, 30 parts moisturizing agent, 70.5 parts deionized water, 0.1 parts preservative (sodium benzoate), 2 parts conductive agent (potassium chloride), and 1 part reinforcing agent (gas-phase SiO2). The natural polymer is gelatin and gellan gum in a weight ratio of 3.5:1, and the moisturizing agent is glycerol, erythritol, and sorbitol in a weight ratio of 1:1:1.

[0057] Comparative Example 3 The only difference from Example 1 is that the moisturizing ingredients are 1,2-propanediol, mannitol and sorbitol in a mass ratio of 1:1:1.

[0058] Specifically, by weight, the gel electrode material comprises the following components: 4.5 parts natural polymer, 30 parts moisturizing agent, 70.5 parts deionized water, 0.1 parts preservative (sodium benzoate), 2 parts conductive agent (potassium chloride), and 1 part reinforcing agent (gas-phase SiO2). The natural polymer consists of red algae gum and gellan gum in a weight ratio of 3.5:1, and the moisturizing agent consists of 1,2-propanediol, mannitol, and sorbitol in a weight ratio of 1:1:1.

[0059] Comparative Example 4 The only difference from Example 1 is that the proportion of natural polymers added to the gel electrode is too high and the proportion of moisturizing ingredients is too low.

[0060] Specifically, by mass percentage, the gel electrode material comprises the following components: 21 parts natural polymer, 13.5 parts moisturizing agent, 70.5 parts deionized water, 0.1 parts preservative (sodium benzoate), 2 parts conductive agent (potassium chloride), and 1 part reinforcing agent (gas-phase SiO2). The natural polymer is red algae gum and gellan gum in a mass ratio of 3.5:1, and the moisturizing agent is glycerol, erythritol, and sorbitol in a mass ratio of 1:1:1.

[0061] The gel electrode samples (12 mm in height, 11 mm in diameter, and 1.2 g in mass) from Examples 1-6 and Comparative Examples 1-4 were placed in a constant temperature and humidity chamber (37 ± 1 °C, 30 ± 5% RH). The sample mass and electrode-skin contact resistance were measured every hour. The test was terminated when the contact resistance was ≥ 50 KΩ. The test duration was considered within the specified conditions.

[0062] Moisturizing stability is assessed based on the weight after use: 1.08-1.2g indicates excellent moisturizing performance; 1.02-1.08g (excluding 1.08g) indicates good moisturizing performance; 0.84-1.02g (excluding 1.02g) indicates average moisturizing performance; 0.72-0.84g (excluding 0.84g) indicates poor moisturizing performance; and less than 0.72g indicates poor moisturizing performance.

[0063] Table 1. Performance test results of gel electrodes in Examples 1-4 and Comparative Examples 1-4 As shown in Table 1, Examples 1-2 used potassium chloride as the conductive component, while Examples 3-4 used PEDOT:PSS. The initial contact resistance of Examples 3-4 was lower than that of Examples 1-2. Examples 5-6, compared to Example 3, used other natural polymers and modified some of the formulation, resulting in slightly lower contact resistance and tensile strength of the resulting gel electrodes. However, compared to Comparative Examples 1-4, the gel electrodes of Examples 1-6 exhibited superior performance in terms of moisture retention stability, service life, conductivity, and mechanical properties.

[0064] Furthermore, the gel electrodes in Examples 1-2, due to their cavities, have a larger surface area, resulting in slightly poorer moisture retention stability compared to the gel electrodes in Examples 3-4 that do not contain cavities. In Example 2, compared to Example 1, the gel electrode pre-contains conductive liquid, leading to a lower initial contact resistance. In Example 4, compared to Example 3, the gel electrode's tensile strength is lower due to the absence of reinforcing components in its material composition, and the pre-contained conductive liquid also results in a lower initial contact resistance. Moreover, the gel electrode without cavities has conductive liquid injected immediately after molding, resulting in a more uniform and stable distribution of conductive liquid compared to the gel electrode with cavities, thus leading to a relatively lower initial contact resistance in Example 4.

[0065] Comparative Example 1, due to an improper ratio of red algae gum and gellan gum, resulted in a hard gel with poor skin adhesion, high impedance, and poor moisturizing stability. Comparative Example 2, using gelatin instead of red algae gum, resulted in insufficient gel strength, easy deformation, and significant impact on impedance and moisturizing stability. Comparative Example 3, employing different combinations of moisturizing ingredients, showed a significant decrease in moisturizing effect. Comparative Example 4, due to an excessively high content of natural polymers and an excessively low content of moisturizing ingredients, resulted in an overly hard gel with rapid water loss and a short shelf life.

[0066] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made using the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A natural polymer gel electrode for electroencephalography, characterized by, The gel electrode material comprises the following components by mass: 2-15 parts of natural polymer, 15-50 parts of moisturizing ingredient, 50-85 parts of water, 0.05-1 part of preservative, and 1-8 parts of conductive ingredient; the natural polymer is component A and component B in a mass ratio of 1-7:1; component A includes at least one of red algae gum, carrageenan, tamarind gum, cassia gum, and chitosan; component B includes at least one of konjac gum, xanthan gum, guar gum, gellan gum, and casein; the moisturizing ingredient is glycerol, erythritol, and sorbitol in a mass ratio of 1-3:1-3:

1.

2. The natural polymer gel electrode for electroencephalography according to claim 1, wherein The material of the gel electrode further includes 0.5-2 parts of reinforcing components; the reinforcing components include one or more of fumed SiO2, mica and silica fume; the particle size of the reinforcing components is 1-50 μm.

3. The natural polymer gel electrode for electroencephalography according to claim 1, wherein The preservatives include one or more of potassium sorbate, sodium benzoate, and Kathon.

4. The natural polymer gel electrode for electroencephalography (EEG) detection according to claim 1, 2, or 3, characterized in that, The conductive components include one or more of sodium chloride, potassium chloride, calcium chloride, Ag / AgCl, silver nanowires, PEDOT:PSS, poly(2-acrylamide-2-methyl-1-propanesulfonic acid) and phosphate.

5. A method for preparing a natural polymeric gel electrode for electroencephalography (EEG) detection as described in any one of claims 1-4, characterized in that, Includes the following steps: (a) The moisturizing ingredients, preservatives, conductive ingredients and water are stirred and dissolved to obtain mixture A; (b) Add natural polymer to mixture A, heat and stir to obtain sol B; (c) After degassing, sol B is injected into a mold; after cooling and molding at room temperature, it is demolded to obtain a cavity-free gel or a cavity-containing gel, wherein the cavity is a hollow structure with at least one side exposed. (d) The gel is refrigerated and solidified to obtain a gel electrode.

6. The method for preparing the natural polymer gel electrode for electroencephalography (EEG) detection according to claim 5, characterized in that, Step (a) includes the following steps: premixing the reinforcing ingredient and a portion of the moisturizing ingredient to obtain a premix; adding the remaining moisturizing ingredient, preservative, conductive ingredient and water to the premix, stirring to dissolve, to obtain mixture A.

7. The method for preparing a natural polymeric gel electrode for electroencephalography (EEG) detection according to claim 5 or 6, characterized in that, In step (b), the heating and stirring temperature is 85-100℃, the stirring speed is 600-800rpm, and the time is 2-30min; in step (d), the cold storage and curing temperature is 2-8℃, and the cold storage time is 12-72h.

8. The method for preparing the natural polymer gel electrode for electroencephalography (EEG) detection according to claim 5, characterized in that, In step (c), the mold includes a base platform and a cavity injection head disposed above the base platform; the base platform has a groove in the middle; one end of the cavity injection head is connected to the base platform and can be raised and lowered through the connection end; the cavity injection head has a protruding part; after the cavity injection head descends, the other end of the cavity injection head contacts the base platform, and the part of the protruding part that extends beyond the cavity injection head can extend into the groove of the base platform, and the surface of the protruding part in the groove forms a cavity in the gel.

9. An apparatus for assembling a gel electrode as described in any one of claims 1-4 or a gel electrode prepared by the preparation method as described in any one of claims 5-8, characterized in that, The device includes a liquid storage chamber, a delivery module, a gel electrode, and a signal transmission module. The liquid storage chamber is connected through the delivery module and several micropores on the delivery module's contact surface with the gel electrode. Both the liquid storage chamber and the delivery module contain conductive liquid. The delivery module also has a signal transmission module between its contact surface with the gel electrode.

10. The apparatus according to claim 9, characterized in that, A sustained-release membrane is also provided between the micropores and the gel electrode; the sustained-release membrane is a one-way permeable membrane facing the gel electrode.

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