A high-adhesion hydrogel for electroencephalogram test and a preparation method and application thereof

Abstract

The application discloses a kind of high adhesion hydrogel for electroencephalogram test and its preparation method and application, belong to biomedical engineering technical field.The hydrogel includes the following components crosslinked product: anionic monomer, cationic monomer, monomer and mutual penetration agent;The anionic monomer is any one of malic acid, gluconic acid, citric acid and lactic acid, cationic monomer is betaine or acetyl L-carnitine, monomer is N, N-dimethyl acrylamide, acrylic acid, sodium acrylate, 4-acryloyl morpholine or sodium acrylamidomethyl propane sulfonate, mutual penetration agent is sodium chloride aqueous solution or sodium chloride water-retaining agent solution.Preparation, cationic monomer is mixed and dissolved, vacuum drying, adding photo initiator mixing, then mutual penetration agent is added, and it is obtained by ultraviolet light crosslinking.The hydrogel of the application has high adhesion (adhesion strength reaches 203.22 kPa), high ion mobility and excellent biocompatibility, and the signal gain in EEG and ECG test reaches 2-3 times of traditional conductive paste, which can be widely used in medical conductive paste field.

Description

Technical Field

[0001] This invention belongs to the field of biomedical engineering, specifically relating to a highly adhesive hydrogel for electroencephalography (EEG) testing, its preparation method, and its applications. Background Technology

[0002] Electroencephalography (EEG) and electrocardiography (ECG), as two key bioelectrical signal detection technologies, play an irreplaceable role in medical diagnosis and research. EEG is primarily used to monitor the electrical activity of the brain, and is of great significance for the diagnosis and monitoring of neurological diseases such as epilepsy, sleep disorders, and brain injury. ECG, on the other hand, is mainly used to monitor the electrical activity of the heart, and plays a crucial role in the diagnosis of cardiac diseases such as arrhythmias and myocardial infarction. The use of conductive gel is essential in both EEG and ECG testing. Conductive gel increases the electrolyte concentration, improving the conductivity between the electrodes and the skin, thereby obtaining clearer signals. Simultaneously, conductive gel ensures close contact between the electrodes and the skin, reducing motion artifacts and noise interference, and improving signal stability. Furthermore, conductive gel reduces electrode irritation to the skin, improving patient comfort.

[0003] While conductive gels play a crucial role in EEG and ECG testing, existing conductive gels still have some limitations that restrict their effectiveness in clinical applications. Insufficient adhesion is one of the main problems faced by current conductive gels. During testing, the conductive gel needs to ensure a stable and tight contact between the electrode and the scalp or skin to effectively conduct bioelectrical signals. However, many existing conductive gels have insufficient adhesion, causing the electrode to easily loosen or detach, thus affecting the stability and reliability of the signal. This instability not only reduces the diagnostic accuracy of EEG and ECG tests but may also cause discomfort and safety risks to patients. In addition to insufficient adhesion, existing conductive gels also suffer from low ion mobility and poor biocompatibility. Low ion mobility prevents the conductive gel from effectively conducting bioelectrical signals, thus affecting the sensitivity and accuracy of the test. Poor biocompatibility may trigger skin allergic reactions or other adverse reactions in patients, further impacting the clinical application of the conductive gel.

[0004] In recent years, conductive hydrogels have attracted widespread attention as a novel conductive material. Previous studies have reported the application of betaine in conductive hydrogels. A team from Nanjing University of Posts and Telecommunications reported a zwitterionic surfactant-enhanced stable hydrogel (AMB hydrogel), which utilizes the hydrogen bond network formed by betaine and water molecules to improve the hydrogel's resistance to dehydration and has been used for ECG and EEG signal acquisition (Xu W, Gu Y, Xia W, et al. Zwitterionic SurfactantEnhanced Stable Hydrogels for Epidermal Sensors and External Contact ObjectPerception[J].ACS Sensors, 2025. DOI: 10.1021 / acssensors.5c01319.). Furthermore, Chinese patent CN113201097B discloses a smart conductive antibacterial hydrogel prepared using a multi-amino polymer and a zwitterionic monomer. It exhibits good conductivity and antibacterial properties, but its main applications are in medical implants and wound dressings, and its preparation process is complex, using various functional monomers and crosslinking agents. Although the application of betaine in conductive hydrogels has been reported, existing technologies still have the following shortcomings: Most existing hydrogels use chemical cross-linking agents (such as N,N'-methylenebisacrylamide) for cross-linking, introducing potentially toxic substances; the overall performance of existing hydrogels in terms of adhesion strength, ion mobility, and biocompatibility still needs improvement, making it difficult to meet the higher requirements of EEG and ECG testing for signal quality and patient comfort. Therefore, to address the technical problems of insufficient adhesion, low ion mobility, and poor biocompatibility in existing conductive pastes and conductive hydrogels, there is an urgent need to develop a novel conductive material that can achieve a synergistic improvement in high adhesion, high ion mobility, and excellent biocompatibility by constructing an anion-cation synergistic system and introducing interpenetrating agents. Summary of the Invention

[0005] To address the shortcomings of existing conductive materials used in bioelectrical testing such as EEG and ECG, including insufficient interfacial adhesion leading to motion artifacts, low ion mobility resulting in poor signal-to-noise ratio, and poor biocompatibility causing skin irritation and allergies, this invention provides a highly adhesive hydrogel for EEG testing, its preparation method, and its application. This hydrogel is prepared using biocompatible materials. By constructing a synergistic anion-cation system and introducing an interpenetrating agent, it achieves a synergistic improvement in high adhesion, high ion mobility, and excellent biocompatibility, thereby significantly improving the signal quality and patient comfort of EEG and ECG tests.

[0006] To achieve the above objectives, the present invention employs the following technical solution: In a first aspect, the present invention provides a highly adhesive hydrogel for electroencephalography (EEG) testing, the hydrogel comprising a crosslinking product of the following components: anionic monomer, cationic monomer, monomer and interpenetrating agent; The anionic monomer is any one of malic acid, gluconic acid, citric acid and lactic acid; The cationic monomer is any one of betaine, L-carnitine, γ-butylbetaine, proline betaine, and acetyl L-carnitine; The monomer is at least one of N,N-dimethylacrylamide, acrylic acid, sodium acrylate, 4-acryloylmorpholine, and sodium acrylamide methylpropanesulfonate. The water-retaining agent in the interpenetrating agent is any one of glycerin, sorbitol, sodium pyrrolidone carboxylate, and sodium hyaluronate.

[0007] Preferably, the photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone.

[0008] Preferably, the water-retaining agent is any one of glycerin, sorbitol, sodium pyrrolidone carboxylate, and sodium hyaluronate.

[0009] The water-retaining agents bind to water molecules through hydrogen bonding, effectively locking in moisture and preventing the hydrogel's performance from degrading due to water evaporation during prolonged EEG / ECG testing. Furthermore, these water-retaining agents are all biocompatible substances; sodium pyrrolidone carboxylate and sodium hyaluronate are components of the skin's natural moisturizing factor (NMF), further enhancing the product's biocompatibility and patient comfort. This limitation ensures the hydrogel's performance stability under long-term monitoring conditions.

[0010] Preferably, the molar ratio of the cationic monomer to the anionic monomer is 1:(1~4). By controlling the ratio between 1:1 and 4, the electrostatic interaction strength between the cation and anion can be optimized, forming a stable ion pair structure.

[0011] Preferably, the mass of the monomer is 40-80% of the total mass of the anionic and cationic monomers. This ensures a balance between rapid cross-linking and good mechanical properties of the hydrogel, while avoiding increased brittleness or cost due to excessive monomer content.

[0012] Preferably, the interpenetrating agent is an aqueous solution of sodium chloride with a molar concentration of 1 mol / L.

[0013] Secondly, the present invention provides a method for preparing the aforementioned highly adhesive hydrogel for electroencephalography (EEG) testing, comprising the following steps: Anionic and cationic monomers are mixed and dissolved, dried under vacuum, and then mixed with monomers and photoinitiators to obtain a mixture. An interpenetrating agent is added to the mixture, and a cross-linking reaction is carried out under ultraviolet light irradiation to obtain the highly adhesive hydrogel for EEG testing.

[0014] Preferably, the mixing and dissolution is carried out by stirring at room temperature for 2-3 hours, which ensures that the betaine and organic acid are fully dissolved and form a uniform ion pair system. The vacuum drying is carried out at 65-75 °C for 2-3 hours, which can effectively remove excess moisture (avoiding moisture interference with subsequent cross-linking reactions) and avoid damage to the raw material structure caused by high temperature.

[0015] Preferably, the volume ratio of the interpenetrating agent to the mixture is 1:(0.1~0.5). This ensures that the interpenetrating agent performs optimally in the system, providing sufficient ion transport channels without diluting the crosslinked network or reducing adhesion strength due to excessive addition.

[0016] Preferably, the amount of photoinitiator added is 0.1-4% of the total mass of the anionic and cationic monomers. This range achieves the best balance between crosslinking efficiency, mechanical properties, and biosafety, and experimental verification shows that the crosslinking effect is optimal at a dosage of 2%.

[0017] Preferably, in the crosslinking reaction, the ultraviolet lamp power is 10~30 W, the wavelength is 365-405 nm, and the irradiation time is 5~25 min. This combination of conditions achieves a balance between rapid crosslinking and good performance, making it suitable for large-scale production, while avoiding material aging or performance degradation that may result from prolonged irradiation.

[0018] More preferably, the ultraviolet lamp has a power of 20 W, a wavelength of 375 nm, and is used for irradiation for 20 min.

[0019] Thirdly, the present invention provides the application of the above-mentioned highly adhesive hydrogel for electroencephalography (EEG) testing in the preparation of medical conductive paste, wherein the medical conductive paste is used for EEG or ECG testing.

[0020] Compared with the prior art, the present invention achieves the following technical effects: The highly adhesive hydrogel provided by this invention for EEG testing utilizes a cation-anion system composed of betaine (cation) and organic acids such as malic acid (anions). Through electrostatic interactions and hydrogen bonding synergistic effects, the adhesion between the hydrogel and the skin interface is significantly enhanced. Simultaneously, the introduction of an interpenetrating agent constructs a highly efficient ion transport network, improving ion mobility and thus enhancing the transmission efficiency of bioelectrical signals. Experimental data show that the adhesive strength of the hydrogel reaches 203.22 kPa, which is 4.3 times that of medical gels; the signal gain in EEG testing is 2-3 times that of traditional conductive gels. Furthermore, all selected raw materials are biocompatible, avoiding skin allergic reactions that may be caused by traditional conductive gels. This product directly solves the three major technical problems of insufficient adhesion, low ion mobility, and poor biocompatibility in existing conductive gels.

[0021] The preparation method provided by this invention employs a solution synthesis approach, which is simple to operate and operates under mild reaction conditions. Excess moisture is removed through a vacuum drying step, ensuring thorough mixing of the monomers with the anion and cation systems and improving crosslinking uniformity. The ultraviolet light-initiated crosslinking reaction is conducted under mild conditions, avoiding the toxicity introduced by traditional chemical crosslinking agents (such as N,N'-methylenebisacrylamide). An interpenetrating agent is added before crosslinking to ensure uniform dispersion within the polymer network, constructing efficient ion transport channels. This method is simple to operate, reacts rapidly (as short as 12.3 seconds), is suitable for industrial production, and eliminates the need for complex post-processing steps, reducing preparation costs and environmental impact.

[0022] The hydrogel provided by this invention exhibits significantly superior performance compared to existing medical gels in ECG and EEG tests. In ECG tests, the ST wave signal amplitude is significantly improved compared to commercial gels. In unshaved prefrontal cortex EEG tests, the signal gain is 2 to 3 times that of traditional conductive gels, and the signal-to-noise ratio is improved. At the same time, its excellent biocompatibility ensures the safety of long-term wear and can be widely used in the medical and biomedical engineering fields. Attached Figure Description

[0023] Figure 1 This shows the trend of the adhesion force of the hydrogel in Example 4 of the present invention changing over time under atmospheric conditions; Figure 2 This invention illustrates the effect and trend of different sweat addition ratios on the adhesion of hydrogels in Example 4. Figure 3 This refers to the time required for the hydrogels synthesized in Examples 1-3 of this invention to fully crosslink; Figure 4 This is a statistical analysis of the device response time when Embodiments 1-3 of the present invention are applied to OECT devices; Figure 5This is a signal comparison between Embodiment 4 of the present invention and medical electrocardiogram electrode gel used for ECG testing; Figure 6 This is a comparison of the ST wave amplitude in Embodiment 4 of the present invention with that of medical electrocardiogram electrode gel used for ECG testing; Figure 7 The hydrogel synthesized in Example 4 of this invention is used for standard electrooculography signal testing. Figure 8 For the comparison of signals from Examples 4 and 7-9 of the present invention and medical non-adhesive conductive paste used for EEG testing of the frontal lobe without shaving, O1-AV is the signal measured in Example 8, and O2-AV is the signal measured by medical non-adhesive conductive paste. Figure 9 For the biocompatibility test of Example 8 of the present invention and medical non-adhesive conductive paste, (a) the cell viability staining results in the cell culture medium of Example 8 and the US Ten20@ conductive paste; (b) the mitochondrial activity of cells in the cell culture medium of Example 8 and the US Ten20@ conductive paste; (c) the cell density in the cell culture medium of Example 8 and the US Ten20@ conductive paste. Detailed Implementation

[0024] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0025] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0026] The following describes the key raw materials, terms, and their sources involved in the examples: The betaine used in this invention was purchased from Sigma-Aldrich (purity ≥99%). L-Carnitine (LC, chemical formula: C7H) 15 NO3) was purchased from Sigma-Aldrich (purity ≥99%). γ-Butyrobetaine (GBB, chemical formula: C7H) 15NO2 was purchased from Sigma-Aldrich (purity ≥98%). Proline betaine (Stachydrine, chemical formula: C7H) 13 NO2 was purchased from Aladdin (purity ≥98%). Acetyl-L-Carnitine (ALCAR, chemical formula: C9H) 17 NO4 was purchased from Sigma-Aldrich (purity ≥ 98%). The malic acid used in this invention was purchased from Sinopharm Chemical Reagent Co., Ltd. (purity ≥ 99%). Gluconic acid (chemical formula: C6H) 12 O7 was purchased from Aladdin (purity ≥ 98%). Citric acid (C6H8O7) was purchased from Sinopharm Chemical Reagent Co., Ltd. (purity ≥ 99.5%). Lactic acid (C3H6O3) was purchased from Sigma-Aldrich (purity ≥ 98%). N,N-Dimethylacrylamide (DMAA, C5H9NO) was purchased from Aladdin (purity ≥ 98%). Acrylic acid (AA, C3H4O2) was purchased from Sinopharm Chemical Reagent Co., Ltd. (purity ≥ 99%). Sodium acrylate (SA, C3H3O2Na) was purchased from Aladdin (purity ≥ 98%). 4-Acryloylmorpholine (ACMO, C7H4O2) was purchased from Aladdin (purity ≥ 98%). 11 NO2 was purchased from TCI (purity ≥98%). Sodium 2-Acrylamido-2-methylpropanesulfonate (AMPS-Na, chemical formula: C7H) 12 NO4SNa was purchased from Sigma-Aldrich (purity ≥98%). 2-Hydroxy-2-methylpropiophenone (HCPK, CAS No.: 7473-98-5) was purchased from Sigma-Aldrich (purity ≥97%). Sodium chloride (NaCl) was purchased from Sinopharm Chemical Reagent Co., Ltd. (purity ≥99.5%). Glycerol (C3H8O3) was purchased from Sinopharm Chemical Reagent Co., Ltd. (purity ≥99%). D-Sorbitol (C6H4SNa) was also purchased from Sinopharm Chemical Reagent Co., Ltd.14 O6 was purchased from Aladdin (purity ≥98%). Sodium pyrrolidone carboxylate (PCA-Na, chemical formula: C5H6NO3Na) was purchased from Aladdin (purity ≥98%). Sodium hyaluronate (HA-Na, chemical formula: C5H6NO3Na) was purchased from Aladdin (purity ≥98%). 14 H 20 NO 11 Na) n Purchased from Sigma-Aldrich (purity ≥98%). Deionized water (DI water, chemical formula: H2O) was purchased from Hangzhou Wahaha Group Co., Ltd. (conductivity ≤0.1μS / cm, meeting the GB / T 6682-2008 standard for Class I laboratory drinking water).

[0027] I. Specific Implementation Cases Example 1 This embodiment provides a highly adhesive hydrogel for electroencephalography (EEG) testing, and the specific preparation process is as follows: Weigh 0.402 g betaine and 1.841 g malic acid raw materials, grind them thoroughly, and add them to a 10 mL glass bottle. Add 2 mL of deionized water to the glass bottle to cover the powder raw materials. Stir at room temperature for 1-2 h to fully dissolve the raw materials. Then, place the glass bottle open in a vacuum oven at 65-70 ℃ for 2-3 h to remove excess water and obtain a dry hydrogel solvent. 3.365 g of monomer N,N-dimethylacrylamide (DMAA, the amount of monomer added is 60 wt% of the total mass of anionic and cationic monomers), 0.067 g of photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone (HCPK, the amount of photoinitiator added is 2 wt% of monomer DMAA), and the above 5.675 g of hydrogel solvent were dissolved at 70~75℃ to obtain a hydrogel precursor solution. The hydrogel precursor solution was transferred to a silicone mold and irradiated with a 20 W ultraviolet lamp with a wavelength of 375 nm for 20 min to allow it to fully crosslink. After crosslinking was completed, the mold was demolded to obtain a highly adhesive hydrogel for EEG testing.

[0028] Example 2 This embodiment provides a highly adhesive hydrogel for electroencephalography (EEG) testing. Compared with Example 1, this example controls the monomer content in the final hydrogel product to be 40 wt%. The specific preparation process is as follows: Weigh 0.425 g betaine and 1.946 g malic acid raw materials, grind them thoroughly and add them to a 10 mL glass bottle. Add 2 mL of deionized water to the glass bottle to cover the powder raw materials. Stir at room temperature for 2 h to fully dissolve the raw materials. Place the glass bottle open in a vacuum oven at 65~70 ℃ for 2~3 h to remove excess water and obtain a dry hydrogel solvent. Weigh 1.581 g of monomer DMAA (the amount of monomer added is 40 wt% of the total mass of anionic and cationic monomers), 0.032 g of photoinitiator HCPK (the amount of photoinitiator added is 2 wt% of monomer DMAA), and the above 3.984 g of hydrogel solvent, and dissolve them at 70~75℃ to obtain a hydrogel precursor solution; transfer the hydrogel precursor solution into a silicone mold, and irradiate it with a 20 W ultraviolet lamp with a wavelength of 375 nm for 20 min to allow it to fully crosslink. After the crosslinking is completed, demold to obtain a highly adhesive hydrogel for EEG testing.

[0029] Example 3 This embodiment provides a highly adhesive hydrogel for electroencephalography (EEG) testing. Compared with Example 1, this example controls the monomer content in the final hydrogel product to be 20%. The specific preparation process is as follows: Weigh 0.457 g betaine and 2.092 g malic acid raw materials, grind them thoroughly, and add them to a 10 mL glass bottle. Add 2 mL of deionized water to the glass bottle to cover the powder raw materials. Stir at room temperature for 1-2 h to fully dissolve the raw materials. Then, place the glass bottle open in a vacuum oven at 65-70 ℃ for 2-3 h to remove excess water and obtain a dry hydrogel solvent. Weigh 0.637 g of monomer DMAA (the amount of monomer added is 20 wt% of the total mass of anionic and cationic monomers), 0.013 g of photoinitiator HCPK (the amount of photoinitiator added is 2 wt% of monomer DMAA), and the above 3.199 g of hydrogel solvent and dissolve them at 70~75℃ to obtain a hydrogel precursor solution. Transfer the hydrogel precursor solution to a silicone mold and irradiate it with a 20 W ultraviolet lamp with a wavelength of 375 nm for 20 min to allow it to fully crosslink. After the crosslinking is completed, demold the sample to obtain a highly adhesive hydrogel for EEG testing.

[0030] Example 4 This embodiment provides a highly adhesive hydrogel for electroencephalography (EEG) testing. Compared with Example 1, this embodiment adds an interosmotic agent to the system and controls the volume ratio of the hydrogel precursor solution to the interosmotic agent to be 2:1. The specific preparation process is as follows: Weigh 0.488 g of betaine and 2.234 g of malic acid raw materials, grind them thoroughly and add them to a 10 mL glass bottle. Add 2 mL of deionized water to the glass bottle to cover the powder raw materials. Stir at room temperature for 1-2 h to fully dissolve the powder. Place the glass bottle open in a vacuum oven at 65-70 ℃ for 2-3 h to remove excess water and obtain a dry hydrogel solvent. Weigh 4.083 g of monomer DMAA (the amount of monomer added is 60 wt% of the total mass of anionic and cationic monomers), 0.0816 g of photoinitiator HCPK (the amount of photoinitiator added is 2 wt% of monomer DMAA), and the above 6.805 g of hydrogel solvent and dissolve them at 70~75℃ to obtain a hydrogel precursor solution; take 2 mL of hydrogel precursor solution and add 1 mL of 1 M NaCl aqueous solution of interpenetrating agent (the volume ratio of hydrogel precursor solution to interpenetrating agent is 2:1), transfer it to a silicone mold, and irradiate it with a 20 W ultraviolet lamp with a wavelength of 375 nm for 20 min to allow it to fully crosslink. After the crosslinking is completed, demold to obtain a highly adhesive hydrogel for EEG testing.

[0031] Example 5 This embodiment provides a highly adhesive hydrogel for electroencephalography (EEG) testing. Compared with Example 1, this embodiment adds an interosmotic agent to the system and adjusts the volume ratio of the hydrogel precursor solution to the interosmotic agent to be 1:1. The specific preparation process is as follows: Weigh 0.504 g betaine and 2.380 g malic acid raw materials, grind them thoroughly and add them to a 10 mL glass bottle. Add 2 mL of deionized water to the glass bottle to cover the powder raw materials. Stir at room temperature for 2 h to fully dissolve the powder. Place the glass bottle open in a vacuum oven at 65~70 ℃ for 2~3 h to remove excess water and obtain a dry hydrogel solvent. Weigh 4.326 g of monomer DMAA (the amount of monomer added is 60 wt% of the total mass of anionic and cationic monomers), 0.087 g of photoinitiator HCPK (the amount of photoinitiator added is 2 wt% of monomer DMAA), and the above 7.297 g of hydrogel solvent and dissolve them at 70~75℃ to obtain a hydrogel precursor solution; take 2 mL of hydrogel precursor solution and add 2 mL of 1 M NaCl aqueous solution of interpenetrating agent (the volume ratio of hydrogel precursor solution to interpenetrating agent is 1:1), transfer it to a silicone mold, and irradiate it with a UV lamp with a power of 20 W and a wavelength of 375 nm for 20 min to allow it to fully crosslink. After the crosslinking is completed, demold to obtain a highly adhesive hydrogel for EEG testing.

[0032] Example 6 This embodiment provides a highly adhesive hydrogel for electroencephalography (EEG) testing. Compared with Example 1, this embodiment adds an interosmotic agent to the system and adjusts the volume ratio of the hydrogel precursor solution to the interosmotic agent to 2:3. The specific preparation process is as follows: Weigh 0.431 g betaine and 1.973 g malic acid raw materials, grind them thoroughly, and add them to a 10 mL glass bottle. Add 2 mL of deionized water to the glass bottle to cover the powder raw materials. Stir at room temperature for 1-2 h to fully dissolve the powder. Then, place the glass bottle open in a vacuum oven at 65-70 ℃ for 2-3 h to remove excess moisture and obtain a dry hydrogel solvent. Weigh 3.606 g of monomer DMAA (the amount of monomer added is 60 wt% of the total mass of anionic and cationic monomers), 0.072 g of photoinitiator HCPK (the amount of photoinitiator added is 2 wt% of monomer DMAA), and the above 6.082 g of hydrogel solvent, and dissolve them at 70~75℃ to obtain a hydrogel precursor solution; take 2 mL of hydrogel precursor solution and add 3 mL of 1 M NaCl aqueous solution of interpenetrating agent (the volume ratio of hydrogel precursor solution to interpenetrating agent is 2:3), transfer it to a silicone mold, and irradiate it with a 20 W ultraviolet lamp with a wavelength of 375 nm for 20 min to allow it to fully crosslink. After the crosslinking is completed, demold to obtain a highly adhesive hydrogel for EEG testing.

[0033] Example 7 This embodiment provides a highly adhesive hydrogel for electroencephalography (EEG) testing. Compared with Example 1, this embodiment replaces the monomer with 4-acryloylmorpholine. The specific preparation process is as follows: Weigh 0.469 g of betaine and 3.437 g of malic acid raw materials, grind them thoroughly, and add them to a 10 mL glass bottle. Add 2 mL of deionized water to the glass bottle to cover the powder raw materials. Stir at room temperature for 1-2 h to fully dissolve the powder. Then, place the glass bottle open in a vacuum oven at 65-70 ℃ for 2-3 h to remove excess moisture and obtain a dry hydrogel solvent. Weigh 5.942 g of monomer 4-acryloylmorpholine (the amount of monomer added is 60 wt% of the total mass of anionic and cationic monomers), 0.119 g of photoinitiator HCPK (the amount of photoinitiator added is 2 wt% of monomer DMAA), and the above 9.903 g of hydrogel solvent, and dissolve them at 70~75℃ to obtain a hydrogel precursor solution; take 2 mL of hydrogel precursor solution and add 1 mL of 1 M NaCl solution of interpenetrating agent (the volume ratio of hydrogel precursor solution to interpenetrating agent is 2:1), transfer it to a silicone mold, and irradiate it with a UV lamp with a power of 20 W and a wavelength of 375 nm for 20 min to allow it to fully crosslink. After the crosslinking is completed, demold to obtain a highly adhesive hydrogel for EEG testing.

[0034] Example 8 This embodiment provides a highly adhesive hydrogel for electroencephalography (EEG) testing. Compared to Example 7, this embodiment replaces the monomer of the hydrogel product with sodium acrylamide methylpropanesulfonate. The specific preparation process is as follows: Weigh 0.402 g betaine and 2.637 g malic acid raw materials, grind them thoroughly, and add them to a 10 mL glass bottle. Add 2 mL of deionized water to the glass bottle to cover the powder raw materials. Stir at room temperature for 2 h to fully dissolve the powder. Then, place the glass bottle open in a vacuum oven at 65~70 ℃ for 2~3 h to remove excess water and obtain a dry hydrogel solvent. Weigh out 5.550 g of sodium acrylamide methylpropanesulfonate monomer (the amount of monomer added is 60 wt% of the total mass of anionic and cationic monomers), 0.111 g of photoinitiator HCPK (the amount of photoinitiator added is 2 wt% of monomer DMAA), and the above 7.598 g of hydrogel solvent in... 70~75℃ Dissolve to obtain a hydrogel precursor solution; take 2 mL of the hydrogel precursor solution and add 1 mL of 1 M NaCl solution (the volume ratio of the hydrogel precursor solution to the interpenetrating agent is 2:1), then transfer it to a silicone mold and irradiate it with a 20 W UV lamp with a wavelength of 375 nm for 20 min to allow it to fully crosslink. After crosslinking is completed, demold to obtain a highly adhesive hydrogel for EEG testing.

[0035] Example 9 This embodiment provides a highly adhesive hydrogel for electroencephalography (EEG) testing. Compared with Example 7, this embodiment replaces the monomer of the hydrogel with sodium acrylate. The specific preparation process is as follows: Weigh 0.474 g betaine and 2.170 g malic acid raw materials, grind them thoroughly, and add them to a 10 mL glass bottle. Add 2 mL of deionized water to the glass bottle to cover the powder raw materials. Stir at room temperature for 1-2 h to fully dissolve the raw materials. Then, place the glass bottle open in a vacuum oven at 65-70 ℃ for 2-3 h to remove excess water and obtain a dry hydrogel solvent. Weigh 3.966 g of sodium acrylate monomer (the amount of monomer added is 60 wt% of the total mass of anionic and cationic monomers), 0.079 g of photoinitiator HCPK (the amount of photoinitiator added is 2 wt% of the monomer DMAA), and the above 6.689 g of hydrogel solvent and dissolve them at 70~75℃ to obtain a hydrogel precursor solution; take 2 mL of hydrogel precursor solution and add 1 mL of 1 M NaCl solution of interpenetrating agent (the volume ratio of hydrogel precursor solution to interpenetrating agent is 2:1), transfer it to a silicone mold, and irradiate it with a 20 W ultraviolet lamp with a wavelength of 375 nm for 20 min to allow it to fully crosslink. After the crosslinking is completed, demold to obtain a highly adhesive hydrogel for EEG testing.

[0036] Example 10 This embodiment provides a highly adhesive hydrogel for electroencephalography (EEG) testing. Compared with Example 1, the molar ratio of betaine to malic acid is adjusted to 1:2 in this embodiment. The specific preparation process is as follows: Weigh 0.469 g betaine and 1.841 g malic acid (the molar ratio of betaine to malic acid is 1:2), grind them thoroughly, and add them to a 10 mL glass bottle. Add 2 mL of deionized water to the glass bottle to cover the powder raw material, stir at room temperature for 2 h to fully dissolve, and then place the open glass bottle in a vacuum oven at 65~70 ℃ for 2~3 h to remove excess water and obtain a dry hydrogel solvent. Weigh 3.365 g of monomer DMAA (the amount of monomer added is 60 wt% of the total mass of anionic and cationic monomers), 0.067 g of photoinitiator HCPK (the amount of photoinitiator added is 2 wt% of monomer DMAA), and the above 5.675 g of hydrogel solvent and dissolve them at 70~75 °C to obtain a hydrogel precursor solution; take 2 mL of hydrogel precursor solution and add 1 mL of 1 mol / L NaCl aqueous solution of interpenetrating agent (the volume ratio of hydrogel precursor solution to interpenetrating agent is 2:1), transfer it to a silicone mold, and irradiate it with a UV lamp with a power of 20 W and a wavelength of 375 nm for 20 min to allow it to fully crosslink. After the crosslinking is completed, demold to obtain a highly adhesive hydrogel for EEG testing.

[0037] Example 11 This embodiment provides a highly adhesive hydrogel for electroencephalography (EEG) testing. Compared with Example 1, this embodiment replaces betaine with acetyl-L-carnitine. The specific preparation process is as follows: Weigh 0.679g of acetyl-L-carnitine and 1.841g of malic acid raw materials, grind them thoroughly, and add them to a 10 mL glass bottle. Add 2 mL of deionized water to the glass bottle to cover the powder raw materials. Stir at room temperature for 1-2 h to fully dissolve the powder. Then, place the glass bottle open in a vacuum oven at 65-70 ℃ for 2-3 h to remove excess moisture and obtain a dry hydrogel solvent. 3.365 g of monomer N,N-dimethylacrylamide (DMAA, the amount of monomer added is 60 wt% of the total mass of anionic and cationic monomers), 0.067 g of photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone (HCPK, the amount of photoinitiator added is 2 wt% of monomer DMAA), and the above 5.675 g of hydrogel solvent were dissolved at 70~75℃ to obtain a hydrogel precursor solution. The hydrogel precursor solution was transferred to a silicone mold and irradiated with a 20 W ultraviolet lamp with a wavelength of 375 nm for 20 min to allow it to fully crosslink. After crosslinking was completed, the mold was demolded to obtain a highly adhesive hydrogel for EEG testing.

[0038] II. Performance Testing Experiment 1. Adhesion strength test Based on Examples 1-11, the maximum adhesion force of the hydrogel sample on the glass substrate was measured using a digital push-pull force gauge (Japanese Sanryu digital SMF push-pull force gauge). The specific steps are as follows: A 17 mm × 17 mm hydrogel sample was prepared and placed on a UV-ozone treated glass substrate to ensure good adhesion. A digital push-pull force gauge was used to accurately measure the maximum pull force of the hydrogel sample on the glass substrate. A 15 mm × 15 mm blank glass slide was mounted below the force gauge to ensure sufficient contact area during testing. During the test, the hydrogel sample was firmly adhered to the glass substrate, and the force gauge was raised at a constant speed (10 mm / min) to slowly peel the hydrogel sample from the glass substrate. The force gauge readings were continuously recorded until the hydrogel was completely detached from the glass substrate, at which point the maximum pull force was recorded. Finally, the maximum pull force (in Newtons, N) was divided by the actual contact area between the hydrogel sample and the glass substrate (in square meters, m²). 2 The adhesion strength of the hydrogel sample was calculated. This step helps to quantify the adhesion performance of the hydrogel on a specific substrate, and the test results are shown in Table 1.

[0039] Table 1: Comparison of Adhesion Strength of Medical Gels in Examples 4-6

[0040] As shown in Table 1, Example 4 exhibited the highest adhesion strength, reaching 203.22 kPa, which is 4.3 times that of the medical gel (47.60 kPa). (See attached table.) Figure 1 As shown, the adhesion strength of the synthesized hydrogel in Example 4 exhibits a significant change trend over time under atmospheric conditions. Experimental data indicate that the system reaches its maximum adhesion strength, approximately 203.22 kPa, when the volume ratio of the interpenetrating agent to the hydrogel precursor solution is 2:1.

[0041] 2. Sweat Adaptability Test like Figure 2 As shown in Example 4, the effect of the sweat addition ratio on the adhesion performance of the hydrogel indicates that under low sweat concentration conditions (<1.5%), the hydrogel adhesion force shows a slight increase; however, when the sweat addition ratio exceeds 1.5%, the material adhesion performance significantly decreases. The results suggest that a moderate sweating environment significantly enhances the adhesion performance of hydrogel materials. In practical applications, the sweating rate of the human body under normal activity is approximately 0.0008–0.0012 mL / cm². 2 / h. Experimental analysis revealed that only a very small amount of sweat (<1.5%) could penetrate into the hydrogel system, indicating that the hydrogel material has excellent sweat barrier properties while effectively utilizing trace amounts of sweat to enhance interfacial adhesion.

[0042] 3. Crosslinking time test like Figure 3 As shown, under 375 nm ultraviolet light (20 W) irradiation, the hydrogels of Examples 1-3 exhibited significantly different crosslinking kinetics. Experimental data showed that as the DMAA monomer content decreased, the time required for the hydrogel to reach a fully crosslinked state increased significantly: when the monomer content decreased from 60% to 40%, the full crosslinking time increased from 12.3 s to 37.7 s; when the monomer content decreased to 20%, the full crosslinking time increased to 68.5 s. This regular change clearly reveals the positive correlation between monomer content and the material crosslinking rate. Based on system optimization experiments, this invention determined that a 60% DMAA monomer ratio can achieve the best crosslinking time control effect, achieving efficient curing while ensuring material performance.

[0043] 4. Response time test As attached Figure 4The figure shows the statistical results of response time when Examples 1, 2, and 3 were used as electrolytes for organic electrochemical transistors (OECT) devices. The OECT devices employed a planar structure. Using a patterned mask combined with vacuum thermal evaporation, 2 nm of chromium (Cr) and 60 nm of gold (Au) were sequentially deposited on a pretreated quartz glass substrate as the source and drain, respectively. Subsequently, g2t-tt was spin-coated onto the patterned electrode surface as the channel layer material, with a film thickness controlled within the range of 50-60 nm. Reactive ion etching (RIE) was used to process the channel layer, with the following process parameters: power 20 W, oxygen (O2) flow rate 20 sccm, and etching time 4-10 min. Finally, 10 μL of a hydrogel precursor solution was dropped onto the channel surface, cured under UV light, and the device performance was characterized using a 2 mm diameter Ag / AgCl rod electrode. Experimental data show that as the monomer DMAA content decreases, the device response time increases: the response time is shortest at 60% monomer content, about 0.8 s; the response time increases to 1.5 s at 40% monomer content; and the response time further increases to 2.8 s at 20% monomer content.

[0044] 5. ECG test like Figure 5 As shown, the signal performance of Example 4 and commercial medical ECG electrode gel (Jinnote ECG conductive gel, Jining High-tech Zone Jinnote Medical Gel Factory) in electrocardiogram (ECG) testing was compared. In the experiment, the gel portion of the commercial electrode patch was replaced with that of Example 4, and a standard ammeter was used to acquire ECG signals. The results showed that Example 4 could stably acquire ECG signals under laboratory conditions, demonstrating good signal acquisition performance.

[0045] like Figure 6 As shown, the amplitude difference of the ST wave signal in ECG testing was further compared between Example 4 and commercial medical ECG electrode gel. Experimental data confirmed that Example 4 has a superior signal amplification capability compared to commercial medical electrode gel, with an ST wave signal amplitude approximately 1.8 times that of the commercial gel, and this capability gradually weakens with increasing interpenetrating agent volume ratio.

[0046] 6. Electrooculogram (EOG) signal test like Figure 7As shown, the hydrogel material of Example 4 exhibits excellent performance in electrooculography (EOG) signal detection. The experiment used standard EEG electrodes, replacing traditional medical conductive gel with the hydrogel of Example 4. Signal acquisition and comparison tests were conducted in the eyelid region (standard EOG signal) and the cheek / back of the head region (top occipital EOG signal). Experimental data show that this hydrogel material can achieve high-precision EOG signal detection using a digital source meter, clearly identifying characteristic electrical signal changes generated by actions such as blinking (signal amplitude up to 1.7 mV) and vertical eye movements (signal amplitude up to 2.2 mV). This performance confirms the significant application value of the hydrogel of this invention in the field of bioelectrical signal sensing.

[0047] 7. EEG test like Figure 8 As shown, this study compared the signal acquisition performance of Examples 4, 7, 8, and 9 with that of a medical non-adhesive gel in prefrontal electroencephalography (EEG) testing. The experiment employed a dual-occipital pole comparison method, using Examples 4, 7, 8, and 9 on the left occipital pole and the medical non-adhesive conductive gel on the right, focusing on evaluating the signal amplification capability and signal-to-noise ratio (SNR) of both. Experimental data showed that Examples 4, 7, 8, and 9 significantly outperformed the traditional medical conductive gel in terms of EEG signal amplification performance. Regarding signal amplification performance, all tested hydrogels (Examples 4, 7, 8, and 9) exhibited significantly better signal amplification capabilities than the control group, with signal gain reaching 2-3 times that of the control group. Regarding SNR performance, all examples showed the highest SNR, approximately 35% higher than the control group. Considering cost analysis and biocompatibility, Example 8 demonstrated the best overall performance and is the most promising candidate material for clinical application.

[0048] 8. Biocompatibility testing To further evaluate the biocompatibility of Example 8, a cell culture experiment was conducted. The experimental method is as follows: The hydrogel of Example 8 and the US Ten20® conductive gel were respectively immersed in cell culture medium for 24 h, and the extracts were collected for human skin fibroblast culture. After 48 h of culture, the cells were stained using a live / dead cell staining kit to observe cell viability and morphology; at the same time, the CCK-8 assay was used to detect mitochondrial activity and cell density was counted. The results are shown in the attached figure. Figure 9 As shown.

[0049] Experimental data showed that, compared with medical conductive ointment, the cell culture medium soaked in Example 8 exhibited higher mitochondrial activity and cell density, with well-preserved cell morphology and a significantly lower proportion of dead cells compared to the control group. The mitochondrial activity of cells in the Example 8 group was approximately 28% higher than that in the control group, and the cell density was approximately 35% higher, confirming its excellent biocompatibility.

[0050] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A highly adhesive hydrogel for electroencephalography (EEG) testing, characterized in that, The hydrogel comprises a crosslinking product of the following components: anionic monomers, cationic monomers, monomers, interpenetrating agents, and photoinitiators; The anionic monomer is any one of malic acid, gluconic acid, citric acid and lactic acid; The cationic monomer is any one of betaine, L-carnitine, γ-butylbetaine, proline betaine, and acetyl L-carnitine; The monomer is at least one of N,N-dimethylacrylamide, acrylic acid, sodium acrylate, 4-acryloylmorpholine, and sodium acrylamide methylpropanesulfonate. The interpenetrating agent is an aqueous solution of sodium chloride or a water-retaining agent solution containing sodium chloride.

2. The highly adhesive hydrogel for electroencephalography (EEG) testing according to claim 1, characterized in that, The water-retaining agent in the interpenetrating agent is any one of glycerin, sorbitol, sodium pyrrolidone carboxylate, and sodium hyaluronate; the photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone.

3. The highly adhesive hydrogel for electroencephalography (EEG) testing according to claim 1, characterized in that, The molar ratio of the cationic monomer to the anionic monomer is 1:(1~4).

4. The highly adhesive hydrogel for electroencephalography (EEG) testing according to claim 1, characterized in that, The mass of the monomer is 40-80% of the total mass of the cationic and anionic monomers.

5. A method for using a highly adhesive hydrogel for electroencephalography (EEG) testing according to any one of claims 1-4, characterized in that, Includes the following steps: Anionic and cationic monomers are mixed and dissolved, dried under vacuum, and then mixed with monomers and photoinitiators to obtain a mixture. An interpenetrating agent was added to the mixture, and a cross-linking reaction was carried out under ultraviolet light irradiation to obtain the highly adhesive hydrogel for EEG testing.

6. The method for preparing a highly adhesive hydrogel for electroencephalography (EEG) testing according to claim 5, characterized in that, Mix and dissolve by stirring at room temperature for 2-3 hours; vacuum dry at 65-75℃ for 2-3 hours.

7. The method for preparing a highly adhesive hydrogel for electroencephalography (EEG) testing according to claim 5, characterized in that, The volume ratio of the interpenetrating agent to the mixture is 1:(0.1~0.5).

8. The method for preparing a highly adhesive hydrogel for electroencephalography (EEG) testing according to claim 5, characterized in that, The amount of photoinitiator added is 0.1-4% of the total mass of the anionic and cationic monomers.

9. The method for preparing a highly adhesive hydrogel for electroencephalography (EEG) testing according to claim 5, characterized in that, In the crosslinking reaction, the ultraviolet lamp power is 10~30 W, the wavelength is 365-405 nm, and the irradiation time is 5~25 min.

10. The application of the highly adhesive hydrogel for EEG testing according to any one of claims 1-4 in the preparation of a medical conductive paste, wherein the medical conductive paste is used for EEG or ECG testing.

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