Hydrogel material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of biological electrodes, in particular to a hydrogel material and a preparation method and application thereof. According to the hydrogel material, an amide polymer with a cyclic structure is used as a framework, metal salt is used as conductive particles, and polyvinyl alcohol and / or polyethylene glycol are / is used as a plasticizer; wherein the structure of the amide polymer with the cyclic structure is shown as a general formula (I); one or more of X1-X4 are amido groups, and are alkyl groups when not amido groups; r1-R5 are respectively independent, identical or different hydrogen atoms or alkyl groups containing 1-10 carbon atoms; m is any integer from 0 to 6; and n is any integer in the range of 20 to 20000. The permeable low-impedance hydrogel material provided by the invention is used for improving the problem that the interface contact between the skin and an electrode is not tight enough, is used for enhancing the definition of electrocardio and electroencephalogram signals, and can effectively make up the defects in the prior art.

Description

Technical Field

[0001] The present invention relates to the technical field of bioelectrodes, and in particular to a hydrogel material and a preparation method and application thereof. Background Art

[0002] With modern medicine's in-depth exploration of neuroscience and cardiac electrophysiology, as well as breakthroughs in biosensor technology and signal processing algorithms, the demand for brain and cardiac function monitoring is growing in multiple dimensions, and is rapidly developing towards life-cycle health management and multidisciplinary cross-applications. Taking neonatal neurodevelopmental monitoring as an example, electroencephalograms (EEGs) can dynamically assess infants' background EEG activity, sleep-wake cycles, and brain maturity, accurately identify hypoxic-ischemic encephalopathy, and significantly reduce the risk of sequelae such as cerebral palsy and cognitive impairment. These EEGs are of great medical value for the healthy growth of newborns. Clinically, EEG signals play an irreplaceable and critical role in diagnosing epilepsy types and seizure origins. By capturing the abnormal discharge characteristics of brain neurons, they can accurately locate the lesions, providing direct evidence for drug selection, surgical guidance, and neuromodulatory therapy. On the other hand, electrocardiogram (ECG) is a key tool for diagnosing various high-incidence and high-mortality heart diseases such as acute myocardial infarction, atrial fibrillation, and myocardial ischemia. It can effectively reduce the risk of thromboembolism, stroke, and sudden death, and has important decision-making value for improving patients' quality of life and primary prevention of cardiogenic diseases.

[0003] As one of the most widespread physiological signals in the human body, physiological electrical signals reflect the most basic state of life activities in the body. From neonatal brain protection to the management of co-morbidities of the elderly with heart and brain, electrophysiological monitoring is becoming the core link between basic research and clinical practice, providing a key breakthrough for conquering nervous system and cardiovascular diseases. The development of these technologies has not only reconstructed the diagnosis and treatment pathways for critical illnesses, but also promoted the realization of personalized precision medicine through innovative models such as remote monitoring and closed-loop feedback management systems. Therefore, accurately capturing and extracting physiological electrical signals (especially electrocardiogram and electroencephalogram signals) through bioelectrodes is a prerequisite for realizing the above-mentioned functions, and is also the basis for signal post-processing and qualitative and quantitative analysis, which is of great significance.

[0004] Compared with invasive and semi-invasive electrodes, non-invasive electrodes act on the surface of the skin and belong to the second category of medical devices, and do not need to be surgically implanted, have no risk of immune infection and long-term damage, have lower overall technical difficulty and manufacturing cost, and have higher market acceptance. For consumer medical, commercial entertainment, sports monitoring and other fields, disposable non-invasive electrodes are more popular. However, due to the fact that electrocardiogram and electroencephalogram signals are relatively weak and the heart and brain activities are very complex, how to accurately obtain effective signals from the human body and minimize noise interference remains a major technical problem. There are mainly the following two reasons: (1) The modulus difference between the dry electrode represented by metal (such as silver / silver chloride) and carbon-based composite materials and the skin is large, and the electrode cannot completely conform to the head or be conformal with other body parts; (2) In the case that the interface between the electrode and the skin lacks good contact, the electric signal is difficult to penetrate the high-impedance stratum corneum and air gap, and the conductive path is blocked, so most of the strength is lost, and thus the signal export process is seriously affected, and it is difficult to obtain high-quality bioelectric signals, which may be manifested as loss of characteristic waveform, small signal-to-noise ratio, etc., which poses higher challenges to subsequent analysis and identification algorithms.

[0005] At present, the commonly used solutions include applying conductive paste or adding a layer of polyacrylic acid-based (PAA) or polyacrylamide-based (PAM) hydrogel. However, the conductive paste needs to be injected into each electrode one by one during use, which is tedious, time-consuming and labor-intensive, and the electrode needs to be cleaned after use for recycling; PAA and PAM monomers themselves do not have good biocompatibility, and the production process does not comply with the principle of green development.

[0006] In view of this, the present application is proposed. SUMMARY

[0007] In view of the signal attenuation problem faced by non-invasive electrocardiogram and electroencephalogram monitoring, developing a new electrode-skin interface coupling medium has become a key direction to break through the technical bottleneck. The ideal medium material needs to meet the dual core demands: on the one hand, the rheological property matching (i.e. the shear modulus is close to the skin epidermis) is realized to achieve full filling of the interface gap; on the other hand, special intermolecular interaction is constructed to promote the penetration of electric signals through the dense stratum corneum barrier. Such a medium layer should have low impedance characteristics to minimize signal transmission loss. At the same time, its viscoelastic behavior needs to be coordinated with the skin biomechanical response to ensure the maintenance of a stable electrical contact interface during dynamic fitting.

[0008] In order to solve the above technical problems of the present application, the present application provides a permeable low-impedance hydrogel material to improve the problem of insufficient close contact between the skin and the electrode, for enhancing the clarity of electrocardiogram and electroencephalogram signals, and effectively making up for the deficiencies in the prior art.

[0009] Based on this, the present application has the following technical solutions: In the first aspect, the present application provides a hydrogel material, which has a cyclic structure amide polymer as a skeleton, a metal salt as a conductive particle, and polyvinyl alcohol and / or polyethylene glycol as a plasticizer. ; One or more of X1~X4 is an amide group, and when it is not an amide group, it is an alkyl group; R1~R5 are each independently, identically or differently, a hydrogen atom or an alkyl group containing 1~10 carbon atoms; m is any integer from 0~6; and n is any integer from 20~20000.

[0010] In the present application, the cyclic structure of the amide polymer with a cyclic structure is located in the side chain; the amide bond can be located in the main chain, or in the side chain or inside the cyclic structure of the side chain.

[0011] In the present application, the amide polymer with a cyclic structure as the basic skeleton of the hydrogel material gives the material good deformation ability, moderate rheological properties, and a shear modulus close to the skin epidermis, which can fit different shapes of human body parts, significantly reducing the possibility of air gap at the electrode-skin interface, and providing protection for the continuity of the conductive path. The amide polymer with a cyclic structure also provides the hydrogel material with the permeability of the stratum corneum of the skin, and its molecules can penetrate the skin surface by several microns, and form a strong interaction with the skin, which macroscopically exhibits excellent adhesion, further tightly locking the electrode and the skin together, and ensuring good contact between them when wearing and testing the device. The metal salt is dissolved in the solvent in the form of ions, which can move freely inside the hydrogel material, and construct sufficient conductive paths, so that the overall impedance is reduced to several thousand or even a few hundred ohms, to minimize signal transmission loss and improve the authenticity and recognition of small waveforms.

[0012] According to the hydrogel material provided by the present application, the amide polymer with a cyclic structure is one or more of polyvinylpyrrolidone, polyvinylpiperidone, polyvinylcaprolactam, and polyurethane containing urea-based pyrimidone side chains.

[0013] According to the hydrogel material provided by the present application, the hydrogel material is mainly prepared from the following raw materials by weight: 1.5~6 parts of an amide polymer with a cyclic structure, 1~10 parts of an additive, 20~55 parts of a solvent, and 1.5~3 parts of a metal salt; the additive includes a plasticizer.

[0014] As a preferred, the additive can also include one or more of anti-aging agents and coloring agents, which are not limited here.

[0015] The solvent comprises one or more of methanol, ethanol, ethylene glycol, formamide, formic acid, N-methyl formamide and water; preferably, the solvent comprises an ethanol aqueous solution with a mass fraction of 5-50 wt%.

[0016] The mass ratio of the amide polymer with a ring structure to the additive is (1-5):(1-10).

[0017] The metal salt comprises one or more of sodium chloride, lithium chloride, potassium chloride, calcium chloride, magnesium chloride, sodium carbonate and sodium sulfate.

[0018] In a second aspect, the application provides a preparation method of the hydrogel material, comprising: Step 1: dissolving the amide polymer with a ring structure in a solvent to obtain precursor A solution; Step 2: dissolving the metal salt and the additive in the solvent to obtain precursor B solution; Step 3: adding the precursor B solution to the precursor A solution to obtain a precursor mixed solution; Step 4: pouring the precursor mixed solution after standing to obtain the upper clear liquid, and then pouring the upper clear liquid into a mold or performing blade coating to form a film, and then performing heat treatment to shape.

[0019] In the preparation method of the hydrogel material, the mold or the coated substrate is selected from one or more of polyethylene terephthalate film, transparent indium tin oxide film, carbon black conductive silicone rubber, silicone oil release film, glass, non-woven fabric, metal and carbon dry electrode.

[0020] In the preparation method of the hydrogel material, the thickness of the poured or blade-coated hydrogel material is 0.005 mm-10 mm.

[0021] In the preparation method of the hydrogel material, the heat treatment shaping temperature is 40℃-90℃.

[0022] In the preparation method of the hydrogel material, the precursor mixed solution is preheated and concentrated first, and the volume change of the concentrated precursor mixed solution is controlled to be 25%-75%, and then heat treatment shaping is performed; wherein the preheating and concentration temperature is 45℃-60℃.

[0023] Further, in step 4, the heat treatment shaping time is 0.01 hour-24 hours.

[0024] Further preferably, in step 4, the precursor mixed solution can be preheated and concentrated first, so that the solvent is preliminarily volatilized, the viscosity during pouring or coating is increased, and the time required for subsequent heat treatment and shaping is shortened. The preheating and concentration time is 1-12 hours, and the volume change of the precursor mixed solution after concentration is 25%-75%.

[0025] In the present application, the prepared hydrogel material has outstanding advantages in horizontal resistance, vertical alternating current impedance, 90° peeling strength, moisturizing capacity, and skin permeability.

[0026] The horizontal resistance is 0.015-15 MΩ, the vertical alternating current impedance is 0.1-50 kΩ, the working frequency is 1-10000000 Hz, and further preferably, the optimal working frequency is 10-100 Hz.

[0027] Further, the 90° peeling strength is 30-250 N / m.

[0028] In the present application, the moisturizing capacity refers to that under the condition of 7-day 60℃ accelerated aging, the mass and resistance value change are both less than 10%; and the skin permeability refers to that the components of the hydrogel material can penetrate 1-10 μm below the stratum corneum.

[0029] In a third aspect, the present application provides the use of the hydrogel material in any of the following aspects: a) skin surface biopotential electrode; b) electric stimulation treatment device; c) wearable device; d) health data analysis; e) physiological electrical signal acquisition.

[0030] Further preferably, due to the excellent biocompatibility and low skin sensitivity of the hydrogel material, the hydrogel material is preliminarily applied in the field of physiological electrical signal acquisition related to electrocardiogram electrode and electroencephalogram electrode.

[0031] Based on the electrocardiogram electrode of the hydrogel material, the signal baseline is finer and more stable, the P wave and Q wave are more clear and distinguishable, and the signal-to-noise ratio is greatly improved, which lays a solid foundation for subsequent signal analysis.

[0032] In a fourth aspect, the present application provides an electrocardiogram electrode containing the hydrogel material.

[0033] Based on the above, the technical scheme of the present application has the following beneficial effects: In the present application, the amide polymer with cyclic structure is used as the basic skeleton of hydrogel material, which gives the material proper rheological properties and fits different body parts; at the same time, it penetrates the stratum corneum and further reduces the possibility of electrode-skin interface instability. The metal salt exists in the form of ions in the solvent and moves freely inside the hydrogel material, building enough conductive paths and minimizing signal transmission loss. The preparation method of the present application is simple and reliable, has large-scale production capacity, can achieve wide adjustability through component control, has good anti-water loss and biocompatibility, and can be applied to non-invasive bioelectrodes such as electrocardiogram and electroencephalogram electrodes to improve the clarity and signal-to-noise ratio of electrocardiogram and electroencephalogram signals. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the present application or prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0035] Figure 1 It is a typical physical photo of the hydrogel material poured and shaped in Example 1 of the present application.

[0036] Figure 2 It is a typical physical photo of the hydrogel material scraped and shaped in Example 2 of the present application.

[0037] Figure 3 It is a vertical alternating current impedance curve graph of the hydrogel material in Example 1 of the present application at different frequencies.

[0038] Figure 4 It is a 90° peel strength curve graph of the hydrogel material in Example 1 of the present application.

[0039] Figure 5 It is a moisture retention capacity curve graph of the hydrogel material in Example 1 of the present application, including the mass and resistance changes at different aging times.

[0040] Figure 6 It is a typical physical photo of an electrocardiogram electrode containing the hydrogel material of the present application in Example 7.

[0041] Figure 7 It is a comparison curve graph of electrocardiogram signals obtained by using the electrocardiogram electrode obtained in Example 7 and a common commercial electrocardiogram electrode in Example 8 of the present application. DETAILED DESCRIPTION

[0042] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be clearly and completely described below in combination with the drawings in the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0043] Unless otherwise specified, the various raw materials used in the examples and comparative examples are all commercially available conventional raw materials, and the technical means used is the conventional means well known to those skilled in the art.

[0044] Example 1 In this embodiment, the adopted amide polymer with a cyclic structure is polyvinylpyrrolidone (PVP) with a weight average molecular weight of 1300000 g / mol; the adopted additive is polyethylene glycol; the adopted solvent is a mixed solvent of ethanol and deionized water, and the ethanol content is 16wt%; and the adopted metal salt is sodium chloride.

[0045] The present embodiment provides a preparation method of a permeable low-impedance hydrogel material, and the specific steps are as follows: 1) Pour 10 g of polyvinylpyrrolidone into 20 mL of a mixed solvent of ethanol and water, and fully stir until all the powders are completely dissolved to form a transparent and homogeneous viscous solution; 2) Pour 4 g of polyethylene glycol and 3.88 g of sodium chloride into 30 mL of a mixed solvent of ethanol and water, and fully stir until all the powders are completely dissolved to form a transparent and homogeneous viscous solution; 3) Add the mixed solution of polyethylene glycol and sodium chloride dropwise into the above polyvinylpyrrolidone solution, and after all the dropwise addition is completed, fully stir at room temperature for 4 hours; 4) Take the supernatant, pour it into a mold, and place it in a 60 ℃ oven for 12 hours to complete the heat treatment and shaping.

[0046] The typical physical photos of the hydrogel material after pouring and shaping in this embodiment are shown in Figure 1 .

[0047] Example 2 The present example provides a preparation method of a permeable low-impedance hydrogel material, which is different from example 1 in that the pouring and shaping is replaced by scraping and shaping. The specific steps are as follows: use a 1 mm coater for scraping, and place it in a 60 ℃ oven for 30 minutes to complete the heat treatment and shaping.

[0048] The typical physical photos of the hydrogel material after scraping and shaping in this embodiment are shown in Figure 2 .

[0049] Example 3 The present example provides a method for preparing a permeable low impedance hydrogel material, which differs from Example 1 in that the weight average molecular weight of the polyvinylpyrrolidone is 58000 g / mol.

[0050] Example 4 The present example provides a method for preparing a permeable low impedance hydrogel material, which differs from Example 1 in that the mass ratio of polyvinylpyrrolidone to polyethylene glycol is 3:2.

[0051] Example 5 The present example provides a method for preparing a permeable low impedance hydrogel material, which differs from Example 1 in that the polyvinylpyrrolidone is replaced by a main chain type amide polymer with a ring structure (polyurethane PU-UPy containing a urea-based pyrimidinone side chain, number average molecular weight 35000).

[0052] Example 6 The present example provides a method for preparing a permeable low impedance hydrogel material, which differs from Example 1 in that the solvent is replaced by ethanol.

[0053] Comparative Example 1 The present example provides a method for preparing a permeable low impedance hydrogel material, which differs from Example 1 in that in step 3), the polyvinylpyrrolidone solution is added dropwise to the mixed solution of polyethylene glycol and sodium chloride.

[0054] Test Example In order to further test the performance of the permeable low impedance hydrogel material, the following tests are carried out, and the specific test method can use the method in the prior art, which is only briefly described here: Test one: horizontal resistance; Two points 2 cm apart on the surface of the shaped hydrogel material are selected as one group, and a total of four groups are selected in the length, width and diagonal directions. The resistance value is measured by a multimeter, and the average value is calculated. The test results are shown in Table 1 below, which shows that the resistance value of the hydrogel material in the horizontal direction is low, and the values at different positions are basically consistent, reflecting the good uniformity of the material.

[0055] Table 1

[0056] Test two: thickness AC impedance; The PET-ITO is used as a mold substrate to cast or blade coat, and after shaping, a layer of PET-ITO is further coated on the surface of the hydrogel material to form a sandwich structure of "ITO-hydrogel material-ITO". The thickness AC impedance is tested by an LCR tester, and the impedance Z value of the hydrogel material at different frequencies of 4 Hz, 10 Hz, 100 Hz, 1 kHz, 10 kHz, 100 kHz, 1 MHz and 10 MHz is tested by connecting the upper and lower ITO layers, and the results are shown in Figure 3 As can be seen, with the increase of working frequency, the thickness AC impedance of the hydrogel material presents a trend of first decreasing and then increasing, and the minimum value is 1.4 kΩ, and the corresponding frequency is 100 Hz. The test result proves the low impedance property of the hydrogel material, which can effectively reduce the hindering effect on physiological electrical signals, and meet the accurate acquisition of weak signals such as electrocardiogram and electroencephalogram.

[0057] Test three: 90° peeling strength The hydrogel material is attached to the arm and left for 15 minutes. The 90° peeling mechanical tensile tester is used for testing, and the results are shown in Figure 4 As can be seen, the adhesion of the hydrogel material to the skin reaches a peak of more than 200 N / m, which is far more than various gel products on the market. The test result proves that the hydrogel material has strong adhesion, which is mainly due to the penetration ability of the amide polymer with a ring structure to the stratum corneum of the skin, which plays a decisive role in stabilizing the electrode-skin interface, and can also be widely adjustable by simple component ratio control. In addition, the material has good deformation ability, moderate rheological property and shear modulus close to the skin epidermis, which can be attached to different shaped human body parts, significantly reducing the possibility of air gap in the electrode-skin interface, and providing guarantee for the continuity of the conductive path.

[0058] Test four: change of mass and resistance value during accelerated aging process The hydrogel material is placed in a 60 °C oven to accelerate the simulation of the aging process, and is taken out every certain time to measure the change of mass and horizontal resistance of the hydrogel material to reflect the strength of its moisturizing ability, and the results are shown in Figure 5 As can be seen, the commercial gel electrode often has a serious problem of water loss, which may lead to shrinkage, increased resistance and other phenomena, while the hydrogel material described in the application exhibits good anti-water loss effect and still has no obvious failure under more stringent experimental conditions.

[0059] Example 7 The present example provides a method for preparing a cardiac electrode containing the hydrogel material of the present application. The specific steps are as follows: 1 mm of the hydrogel material of Example 1 is scraped and coated on the surface of a silver / silver chloride dry electrode, which is placed in a 60°C oven for heat treatment for 12 hours; after the first layer of hydrogel material is completely shaped, 1 mm of the hydrogel material of Example 1 is scraped and coated again, which is placed in a 60°C oven for heat treatment for 12 hours, to obtain a cardiac electrode containing the hydrogel material of Example 1. The diameter of the silver / silver chloride dry electrode is about 1.5 cm, which is loaded on an adhesive non-woven fabric, as shown in Figure 6 .

[0060] In order to further test the performance of the cardiac electrode obtained in Example 7, the following tests are carried out, and the results are shown in Table 2 below. The specific test method is carried out according to the relevant guidelines of “YY / T0196-2005 Disposable Electrocardio Electrode”.

[0061] Table 2

[0062] Example 8 The present example provides a method for real-time acquisition of electrocardio signals using the cardiac electrode obtained in Example 7, and the waveform of the pulse signal is preliminarily analyzed through a single-chip microcomputer and software. The specific steps are as follows: 1) Three cardiac electrodes obtained in Example 7 are prepared and attached to the inner side of the left wrist, the inner side of the right wrist and the vicinity of the heart of the test personnel, respectively. The three cardiac electrodes are connected to the AD8232 single-lead heart rate monitoring chip through a three-way lead, and then connected to the corresponding pins of the Arduino Uno single-chip microcomputer, and the electrocardio signals are collected and output through the control program written in the laboratory.

[0063] 2) The positions of the cardiac electrodes are adjusted forward and backward, and the arms are slightly rotated, so that the pulse signal amplitude displayed on the computer screen is maximum and the baseline is narrowest. After stable measurement for 30 seconds (which can be floated up and down for 10 seconds), the electrocardio data can be collected, and the collection time is generally 60 seconds. The different wavelets in the electrocardio pulse signal can be analyzed according to the collected data, such as P, Q, S, R and T waves. The electrocardio signals obtained by the cardiac electrode of Example 7 and the ordinary commercial cardiac electrode are shown in Figure 7 It can be seen that the baseline of the signal is significantly thinned, the P wave and the Q wave are more clear and distinguishable, and the signal-to-noise ratio is greatly improved, indicating that the cardiac electrode of Example 7 has lower noise and less interference in the signal extraction process. The above results prove that the hydrogel material of Example 1 has excellent performance, which benefits from its unique skin-permeable and low-impedance characteristics, and the clarity of the electrocardio and electroencephalogram signals can be greatly enhanced, which also lays a solid foundation for subsequent signal analysis. The hydrogel materials prepared in Examples 2-5 have similar effects to those of Example 1.

[0064] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and are not intended to limit the same; although the present application has been described in detail with reference to the foregoing examples, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A hydrogel material, characterized in that: An amide polymer with a cyclic structure is used as a skeleton, a metal salt is used as a conductive particle, and polyvinyl alcohol and / or polyethylene glycol is used as a plasticizer; wherein the structure of the amide polymer with a cyclic structure is shown in general formula (I): ； One or more of X1 to X4 is an amide group, and when not an amide group, it is an alkyl group; R1 to R5 are each independently, the same or different, a hydrogen atom or an alkyl group containing 1 to 10 carbon atoms; m is any integer from 0 to 6; and n is any integer from 20 to 20,000.

2. The hydrogel material according to claim 1, characterized in that The amide polymer having a cyclic structure is one or more of polyvinyl pyrrolidone, polyvinyl piperidone, polyvinyl caprolactam, and polyurethane containing urea-pyrimidone side chains.

3. The hydrogel material according to claim 1 or 2, characterized in that The hydrogel material is mainly prepared from the following raw materials in parts by weight: 1.5 to 6 parts of an amide polymer with a cyclic structure, 1 to 10 parts of an additive, 20 to 55 parts of a solvent, and 1.5 to 3 parts of a metal salt; the additive includes a plasticizer.

4. The hydrogel material according to claim 3, characterized in that The solvent includes one or more of methanol, ethanol, ethylene glycol, formamide, formic acid, N-methylformamide and water; preferably, the solvent includes an ethanol aqueous solution with a mass fraction of 5 to 50 wt%.

5. The hydrogel material according to claim 3, characterized in that The mass ratio of the amide polymer having a cyclic structure to the additive is (1-5): (1-10).

6. The hydrogel material according to claim 3, characterized in that The metal salt includes one or more of sodium chloride, lithium chloride, potassium chloride, calcium chloride, magnesium chloride, sodium carbonate and sodium sulfate.

7. The method for preparing the hydrogel material according to any one of claims 1 to 6, characterized in that: include: Step 1: dissolving an amide polymer having a cyclic structure in a solvent to obtain a precursor liquid A; Step 2: Dissolve the metal salt and additive in a solvent to obtain a precursor B solution; Step 3: Adding precursor B liquid to precursor A liquid to obtain a precursor mixed solution; Step 4: After the precursor mixed solution is allowed to stand, the supernatant is taken out for casting into a mold or coating into a film, and then heat-treated to set the shape.

8. The method for preparing a hydrogel material according to claim 7, wherein: In step 4, the mold or the coated substrate is selected from one or more of polyethylene terephthalate film, transparent indium tin oxide film, carbon black conductive silicone rubber, silicone oil release film, glass, non-woven fabric, metal and carbon dry electrode; And / or, in step 4, the thickness of the poured or scraped hydrogel material is 0.005 mm to 10 mm. And / or, in step 4, the temperature of the heat treatment is 40°C to 90°C. Preferably, in step 4, the precursor mixed solution is first preheated and concentrated, the volume change of the concentrated precursor mixed solution is controlled to be 25%~75%, and then heat treated to fix the shape; wherein the preheating and concentration temperature is 45℃~60℃.

9. Use of the hydrogel material according to any one of claims 1 to 6 or the hydrogel material prepared by the preparation method according to claim 7 or 8 in any of the following aspects: a) Skin surface bioelectrodes; b) electrical stimulation therapy equipment; c) Wearable devices; d) health data analysis; e) Physiological electrical signal acquisition.

10. An electrocardiogram electrode, characterized in that: Contains the hydrogel material according to any one of claims 1 to 6 or the hydrogel material prepared by the preparation method according to claim 7 or 8.

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