Preparation method of electromyographic signal acquisition ultralow interface impedance skin self-adaptive electrode

Abstract

The invention provides a preparation method of an electromyographic signal acquisition ultralow interface impedance skin self-adaptive electrode, and belongs to the field of skin self-adaptive electrodes. The problems of high interface impedance, signal attenuation and noise existing in an existing commercial electrode are solved. The preparation method comprises the following steps: by taking polyvinyl alcohol as a base material, preparing a hydrogel matrix with excellent flexibility and biocompatibility through a freeze-thaw cycle process; the elemental silver is reduced on the inner surface of the gel by adopting a two-step soaking method, so that the conductivity and electrostatic induction capability of the electrode are remarkably enhanced, meanwhile, the electrode is endowed with good adhesion, and the stability of the electrode in a complex environment is ensured; tannic acid is introduced and can serve as a reducing agent, the mechanical performance and the adhesion performance of the electrode can be enhanced, interference of motion artifacts is effectively reduced, it is ensured that the electrode is continuously and reliably attached to the skin when the body moves, and therefore the signal-to-noise ratio of electromyographic signal collection is remarkably increased, and the integrity and stability of signals are kept to the maximum extent.

Description

Technical Field

[0001] The present invention relates to the technical field of skin adaptive electrodes, and in particular to a method for preparing an ultra-low interface impedance skin adaptive electrode for collecting electromyographic signals. Background Art

[0002] Electromyographic signals, as bioelectrical signals reflecting muscle electrophysiological activity, have become a core research topic in fields such as sports medicine, rehabilitation engineering, intelligent prosthetic control, and bio-electromechanical interfaces due to their close correlation with human motor function. The technological evolution in this field has been closely linked to innovations in electrode systems, and its development can be divided into five key stages: needle electrodes, surface electrodes, wireless surface electrodes, high-density surface electrodes, and wireless high-density surface electrodes. In clinical applications, since the FDA approved the clinical use of needle electrodes in 1987, this technology, with its unique invasive design, has enabled direct capture of motor unit action potentials, becoming the gold standard for diagnosing muscle diseases. However, it is important to note that invasive testing involves tissue trauma, which can lead to infection risks, and patients generally report significant pain. While the currently popular Ag / AgCl gel electrode offers the advantage of being non-invasive, its interfacial impedance leads to signal attenuation and a reduced signal-to-noise ratio, limiting the accuracy of clinical diagnoses. Summary of the Invention

[0003] The technical problems to be solved by the present invention are:

[0004] In order to solve the problems of high interface impedance, signal attenuation and noise in existing commercial electrodes.

[0005] The present invention is to solve the above technical problems using the following technical solutions:

[0006] The present invention provides a method for preparing an ultra-low interface impedance skin adaptive electrode for myoelectric signal acquisition, comprising the following steps:

[0007] S100, preparing a gel base,

[0008] According to the mass percentage of the total materials (polyvinyl alcohol, deionized water, acrylic acid), accurately weigh 0.5wt%-10wt% polyvinyl alcohol, stir magnetically in a water bath at 90℃ for 3 hours until it is completely dissolved, with a stirring speed of 200r / min-400r / min; then cool to room temperature, weigh 1wt%-10wt% acrylic acid, add it to the polyvinyl alcohol solution, and stir magnetically for 0.5h-2h at a stirring rate of 200r / min-400r / min to ensure that the polyvinyl alcohol and acrylic acid solutions are evenly mixed and no bubbles are generated; The prepared solution is cooled to room temperature and slowly poured into a cleaned and dried polytetrafluoroethylene mold, ensuring that the surface of the solution is flat and free of bubbles. The mold is quickly placed in a low-temperature refrigerator at -20°C to 18°C ​​and frozen for 2-12 hours to crosslink the polyvinyl alcohol solution and form a hydrogel with a three-dimensional network structure. After freezing, the mold is removed and thawed at room temperature for 1-5 hours to separate the hydrogel from the mold. At this point, the polyvinyl alcohol solution in the mold has solidified into a hydrogel substrate with a certain adhesion strength and toughness, completing the preparation of the polyvinyl alcohol hydrogel matrix material.

[0009] S200, soaking the gel substrate prepared in step S100 in a silver nitrate solution,

[0010] The polyvinyl alcohol hydrogel prepared in step S100 is cut into a suitable size to ensure that it meets the electrode size requirements, and then a silver nitrate solution with a concentration of 0.001 mol / L-5 mol / L is prepared. The silver nitrate solution is prepared by measuring a certain amount of deionized water with a graduated cylinder, placing it in a beaker, and stirring it with a magnetic stirrer. A certain amount of silver nitrate is weighed and slowly added to the beaker at a stirring speed of 50 rpm-400 rpm for 3-20 minutes. During the entire preparation process, the operation is strictly protected from light to prevent the silver nitrate from deteriorating.

[0011] Slowly immerse the cut gel substrate in the prepared silver nitrate solution, ensuring that the gel substrate is completely immersed; use a sealed container to seal the immersion system to prevent solution volatilization and interference from external impurities, while continuing to store it away from light; the immersion time depends on the thickness of the gel substrate and the concentration of the silver nitrate solution, generally 2 hours to 8 hours; during the immersion process, the silver ions in the silver nitrate solution will gradually diffuse into the internal network structure of the polyvinyl alcohol hydrogel, preparing for the subsequent reduction reaction;

[0012] S300, the gel substrate soaked in the silver nitrate solution in step S200 is further soaked in a tannic acid solution,

[0013] A tannic acid solution having a total (deionized water and tannic acid) mass fraction of 0.1 wt% to 15 wt% is prepared. The tannic acid solution is prepared by measuring a certain amount of deionized water with a graduated cylinder, placing the water into a beaker, and stirring the water with a magnetic stirrer. A certain amount of tannic acid is weighed and slowly added to the beaker at a stirring speed of 50 rpm to 400 rpm for 5 to 30 minutes. The beaker is then placed in an ultrasonic cleaner for a set ultrasonic time of 5 to 30 minutes to ultrasonically treat the solution so that the tannic acid molecules are more evenly dispersed in the solution, thereby forming a stable tannic acid solution.

[0014] After being soaked in the silver nitrate solution in step S200, the gel base is taken out from the silver nitrate solution, and the taken-out gel base is slowly immersed in the prepared tannic acid solution to ensure that the gel base is completely immersed; the container is also sealed; the soaking time depends on the distribution of silver ions in the gel base and the concentration of the tannic acid solution, generally 1h-24h; during the soaking process, tannic acid, as a natural reducing agent and polyphenol compound, can react with the silver ions in the gel base to reduce elemental silver particles on the inner surface of the gel; at the same time, tannic acid molecules can also cross-link with PVA (polyvinyl alcohol) molecular chains to enhance the tensile and adhesion properties of the hydrogel, so that the electrode can be firmly adhered to the skin without additional adhesives. The specific experimental process is as follows: Figure 1 shown.

[0015] The polyvinyl alcohol hydrogel matrix forms a continuous three-dimensional network structure through freeze-thaw cycles to ensure that it has good flexibility and mechanical properties and can adhere to the skin surface; a layer of elemental silver particles is restored on the inner surface of the gel. The elemental silver is evenly distributed inside the gel and presents the microscopic morphology of silver nanoparticles, enhancing the conductivity and electrostatic induction ability of the electrode; at the same time, considering the physiological structure and movement characteristics of human skin, the shape and size of the electrode are optimized to ensure that the electrode is comfortable to wear and does not affect normal human activities.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The present invention proposes a method for preparing a hydrogel electrode based on a freeze-thaw cycle method, using polyvinyl alcohol as a substrate, and preparing a hydrogel matrix with excellent flexibility and biocompatibility through a freeze-thaw cycle process. On this basis, a two-step immersion method is adopted to reduce elemental silver on the inner surface of the gel, which significantly enhances the conductivity and electrostatic induction ability of the electrode, while giving the electrode good adhesion, ensuring its stability in complex environments, enhancing the electrostatic induction ability of the electrode and reducing impedance. By introducing tannic acid, it can not only serve as a reducing agent, but also enhance the tensile and adhesion properties of the electrode, so that the electrode can achieve firm adhesion to the skin without the need for additional adhesives, effectively reducing the interference of motion artifacts, and ensuring continuous and reliable adhesion to the skin during body movement, thereby significantly improving the signal-to-noise ratio of electromyographic signal acquisition and maximizing the integrity and stability of the signal.

[0018] The present invention uses a double immersion method to help improve the performance of the material. The first immersion is in a silver nitrate solution of a certain concentration, and the second immersion is in a tannic acid solution of a certain concentration. Nano-silver elements can be reduced inside the gel to meet the need of enhancing the charge density. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a flow chart of a method for preparing an ultra-low interface impedance skin adaptive electrode for myoelectric signal acquisition according to an embodiment of the present invention;

[0020] Figure 2 The actual image and microscopic morphology of the electrode of Example 1 prepared by this method in the embodiment of the present invention are shown;

[0021] Figure 3 This is the electrode energy spectrum diagram of the electrode of Example 1 prepared by this method in the embodiment of the present invention;

[0022] Figure 4 This is the XRD analysis diagram of the electrode of Example 1 prepared by this method in the embodiment of the present invention;

[0023] Figure 5 The comparative impedance graphs of electrode examples 1-3 prepared by the present method and a commercial electrode (Schindler electrode X-1) in the embodiments of the present invention are shown;

[0024] Figure 6 Electromyogram and signal-to-noise ratio analysis of myoelectric testing performed on electrodes (Examples 1-3 and commercial electrodes) prepared by this method in the embodiments of the present invention;

[0025] Figure 7 This is the electromyogram of the fist clenching electromyography test performed using the electrode prepared by this method in Example 1 of the present invention. DETAILED DESCRIPTION

[0026] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0027] Example 1

[0028] S100, prepare a gel substrate, take 10wt% polyvinyl alcohol and 5wt% acrylic acid according to the total mass percentage of the material, magnetically stir in a water bath at 90°C for 3 hours at a stirring speed of 300r / min; cool the prepared solution to room temperature, add acrylic acid to the completely dissolved polyvinyl alcohol solution, magnetically stir for 3 hours at a stirring speed of 300r / min, and after the two are completely mixed, pour into a polytetrafluoroethylene mold with a thickness of 2mm, place in a refrigerator at -18°C for 12 hours, and thaw at room temperature for 2 hours. At this time, the PVA solution in the mold has solidified into a hydrogel, completing the preparation of the polyvinyl alcohol hydrogel matrix material;

[0029] S200, soaking in a silver nitrate solution with a concentration of 1.0 M, cutting the gel substrate prepared in the previous step into suitable sizes, and soaking for 6 hours in a sealed container away from light;

[0030] S300, soaking in tannic acid solution: prepare a 5% tannic acid solution, take out the gel substrate soaked in step S200, and place it in the tannic acid solution for soaking for 24 hours.

[0031] Example 2

[0032] S100, prepare a gel substrate, take 10wt% polyvinyl alcohol and 3wt% acrylic acid according to the total mass percentage of the material, magnetically stir in a water bath at 90°C for 3 hours at a stirring speed of 300r / min; cool the prepared solution to room temperature, add acrylic acid to the completely dissolved polyvinyl alcohol solution, magnetically stir for 3 hours at a stirring speed of 300r / min, and after the two are completely mixed, pour into a polytetrafluoroethylene mold with a thickness of 1.5mm, place in a refrigerator at -18°C for 12 hours, and thaw at room temperature for 2 hours. At this time, the PVA solution in the mold has solidified into a hydrogel, completing the preparation of the polyvinyl alcohol hydrogel matrix material;

[0033] S200, soaking in a silver nitrate solution with a concentration of 0.25 M, cutting the gel substrate prepared in the previous step into suitable sizes and soaking them for 5 hours in a sealed container away from light;

[0034] S300, soaking in tannic acid solution: prepare a 15% tannic acid solution, take out the gel substrate soaked in step S200, and place it in the tannic acid solution for soaking for 12 hours.

[0035] Example 3

[0036] S100, prepare a gel substrate, take 10wt% polyvinyl alcohol and 3wt% acrylic acid according to the total mass percentage of the material, magnetically stir in a water bath at 90°C for 3 hours at a stirring speed of 300r / min; cool the prepared solution to room temperature, add acrylic acid to the completely dissolved polyvinyl alcohol solution, magnetically stir for 3 hours at a stirring speed of 300r / min, and after the two are completely mixed, pour into a polytetrafluoroethylene mold with a thickness of 1.5mm, place in a refrigerator at -18°C for 12 hours, and thaw at room temperature for 2 hours. At this time, the PVA solution in the mold has solidified into a hydrogel, completing the preparation of the polyvinyl alcohol hydrogel matrix material;

[0037] S200, soaking in a silver nitrate solution with a concentration of 0.5 M, cutting the gel substrate prepared in the previous step into suitable sizes and soaking them for 4 hours in a sealed container away from light;

[0038] S300, soaking in tannic acid solution: prepare 8 wt% tannic acid solution, take out the gel substrate soaked in step S200, and place it in the tannic acid solution for soaking for 12 hours.

[0039] Comparative experiment

[0040] The present invention conducted a series of detailed microstructure and composition analysis tests on the electrode prepared in Example 1 to fully characterize its physical properties and chemical composition. The macroscopic state and microscopic morphology of the electrode were carefully photographed using a scanning electron microscope (SEM). Figure 2 As shown in Figure 2, the SEM image clearly shows the fine structural features of the electrode surface. In addition, in order to determine the elemental composition of the electrode material, the electrode was scanned using energy dispersive spectroscopy (EDS) technology, as shown in Figure 2. Figure 3 As shown in Figure 2, the energy spectrum analysis results clearly reveal the distribution and relative content of silver in the electrode. In addition, the electrode was scanned and analyzed using X-ray diffraction (XRD) technology, as shown in Figure 2. Figure 4 As shown, the appearance and position of the characteristic diffraction peaks in the XRD pattern accurately correspond to the crystal structure of silver, which conclusively proves the successful generation of silver during the electrode preparation process.

[0041] The electrodes prepared in Example 1, Example 2 and Example 3 were subjected to impedance measurement and signal-to-noise ratio analysis. In terms of impedance measurement, an electrochemical workstation was used for testing. Figure 4It can be clearly seen from the test results that the impedance value of the electrode prepared by the present invention is significantly lower than the impedance level of commercial electrodes (about 100kΩ), among which the lowest impedance value is close to 13kΩ, which is very close to the ideal impedance value of the human body of 10kΩ, indicating that the electrode of the present invention has significant advantages in impedance characteristics and can better match the human body, thus providing a good basic condition for subsequent applications such as signal transmission and detection.

[0042] The significant reduction in interfacial impedance effectively enhances the signal-to-noise ratio performance of the electrode, which can be specifically demonstrated by Figure 5 The signal-to-noise ratio analysis results are intuitively presented. In many fields such as biomedicine that require precise detection of weak signals, a high signal-to-noise ratio is crucial for improving signal accuracy and reliability. The excellent signal-to-noise ratio performance of the electrode of the present invention enables it to more accurately capture and transmit bioelectric signals in practical applications. Compared with traditional commercial electrodes, it exhibits more outstanding performance advantages and brings substantial improvements and enhancements to related technical fields.

[0043] The advantages of the electrodes of the present invention in bioelectrical signal detection are not only reflected in their impedance characteristics and signal-to-noise ratio. In addition, the present invention also conducted fist-clenching electromyographic signal testing on the electrodes prepared in Example 1 to further verify their performance in actual application scenarios. Figure 7 The image clearly displays the EMG signal from a clenched fist. The signal's amplitude and waveform characteristics are consistent with typical EMG patterns, validating the electrode's ability to detect bioelectrical signals in practical applications. This result, consistent with previous impedance and signal-to-noise ratio test results, demonstrates the broad potential of the electrode in biomedical applications.

[0044] Although the present invention is disclosed as above, the scope of protection disclosed by the present invention is not limited thereto. Those skilled in the art of the present invention may make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A method for preparing an ultra-low interface impedance skin adaptive electrode for myoelectric signal acquisition, characterized in that: The following steps are involved: S100, preparing a gel substrate, weighing 0.5 wt% to 10 wt% of polyvinyl alcohol, according to mass percentage, and dissolving it in water to obtain a polyvinyl alcohol solution; then weighing 1 wt% to 10 wt% of acrylic acid, adding it to the polyvinyl alcohol solution until it is completely dissolved, and then slowly pouring it into a cleaned and dried polytetrafluoroethylene mold and freezing it at low temperature, so that the polyvinyl alcohol solution undergoes a freeze-thaw cycle, thereby forming a gel substrate with a three-dimensional network structure; S200, soaking the gel substrate prepared in step S100 in a silver nitrate solution with a concentration of 0.001 mol / L-5 mol / L, sealing the immersion system in a sealed container, and storing in the dark for 2 h-8 h; S300. After taking out the gel substrate soaked in the silver nitrate solution in step S200, continue soaking it in a tannic acid solution with a mass fraction of 0.1wt%-10wt%. Use a sealed container to seal the soaking system and store it in the dark for 1h-24h to finally obtain a skin adaptive electrode.

2. The method for preparing an ultra-low interface impedance skin adaptive electrode for myoelectric signal acquisition according to claim 1, characterized in that: When preparing the polyvinyl alcohol solution, stir it magnetically in a water bath at 90°C for 3 hours until it is completely dissolved at a stirring speed of 200 r / min-400 r / min, and then cool it to room temperature.

3. The method for preparing an ultra-low interfacial impedance skin adaptive electrode for myoelectric signal acquisition according to claim 2, characterized in that: When adding the acrylic acid solution, magnetic stirring is performed for 0.5 h to 2 h at a stirring rate of 200 r / min to 400 r / min to ensure that the polyvinyl alcohol and the acrylic acid solution are mixed evenly without generating bubbles, and then cooled to room temperature.

4. The method for preparing an ultra-low interfacial impedance skin-adaptive electrode for myoelectric signal acquisition according to claim 3, characterized in that: During low-temperature freezing, the mold needs to be quickly placed in a low-temperature refrigerator at -20℃--18℃ and frozen for 2h-12h; after freezing, take out the mold and thaw it at room temperature for 1h-5h to separate the gel base from the mold.

5. The method for preparing an ultra-low interfacial impedance skin adaptive electrode for myoelectric signal acquisition according to claim 4, characterized in that: The silver nitrate solution is prepared by measuring deionized water with a measuring cylinder and placing it in a beaker. Silver nitrate with a concentration of 0.001 mol / L-5 mol / L is slowly added to the beaker and stirred with a magnetic stirrer at a speed of 50 r / min-400 r / min for 3 min-20 min.

6. The method for preparing an ultra-low interfacial impedance skin-adaptive electrode for myoelectric signal acquisition according to claim 5, characterized in that: The tannic acid solution is prepared by measuring deionized water with a measuring cylinder, placing it in a beaker, taking 0.1wt%-10wt% of tannic acid, slowly adding it to the beaker, stirring with a magnetic stirrer at a stirring speed of 50r / min-400r / min, stirring for 5min-30min, and then placing the beaker in an ultrasonic cleaner and setting the ultrasonic time to 5min-30min.

7. The method for preparing an ultra-low interfacial impedance skin-adaptive electrode for myoelectric signal acquisition according to claim 6, characterized in that: When soaking in the silver nitrate solution or tannic acid solution, completely immerse the gel base.

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