A polydopamine biogel electrode and a preparation method and application thereof

Abstract

The present application relates to a kind of polydopamine biological gel electrode and its preparation method and application, belong to the technical field of conductive hydrogel.The method uses polyacrylamide, dopamine hydrochloride, liquid metal gallium-indium alloy and glycerol as main raw materials, liquid metal gallium-indium alloy is conductive component, three-dimensional network is formed by crosslinking agent, and biological gel electrode with excellent conductivity, low skin contact impedance, good toughness and adhesion is obtained.The hydrogel prepared by the present application can be used as a biological electrode patch for electrocardiogram test system;In the aspect of signal acquisition, the electrode shows high signal-to-noise ratio, high signal accuracy, and also has lower impedance and skin interface impedance.In addition, the preparation method of the present application is simple, suitable for large-scale production and popularization and application.

Description

Technical Field

[0001] This invention relates to a polydopamine biogel electrode, its preparation method and application, belonging to the field of conductive hydrogel technology. Background Technology

[0002] Bioelectric signals are generated alongside vital activities within living organisms, such as electrocardiogram (ECG), electroencephalogram (EEG), and electromyogram (EMG). Bioelectrodes are sensors used to measure these bioelectric signals and are widely applied in medicine, physiological research, neuroscience, and human-computer interaction. Bioelectric signals are extremely weak (mV, μV levels), and current bioelectrodes cannot maintain stable contact impedance with the skin over extended periods, severely impacting signal quality. Furthermore, they are inconvenient to use, such as being difficult to clean. To address these issues, hydrogel electrodes have gained increasing attention. However, hydrogel electrodes generally have low strength and unsatisfactory viscosity, making it difficult to ensure good coupling between the hydrogel and skin, resulting in unstable contact impedance. Additionally, the low tensile strength and poor viscoelasticity of gels prevent them from being independently fixed to the skin, necessitating the addition of a large area of ​​pressure-sensitive adhesive around the electrode for fixation, which further increases its bulkiness.

[0003] Furthermore, most current biogel electrodes exhibit only simple adhesive properties, often causing unnecessary adhesion to clothing during wear. This can lead to unavoidable displacement during movement, resulting in distortion of biosignals and inconvenience during long-term use. They are also difficult to remove or have poor re-adhesion after use. Summary of the Invention

[0004] The technical problem solved by this invention is to overcome the shortcomings of the prior art and propose a polydopamine biogel electrode, its preparation method and application. This polydopamine biogel electrode has excellent adhesion, biocompatibility, sweat and moisture resistance, high tensile strength and low impedance. The preparation process is simpler and easier to operate, and has high repeatability. It overcomes the shortcomings of commonly used electrodes that cannot maintain stable contact impedance for a long time. It has the advantages of stable contact impedance, simple structure, good water retention and good biocompatibility. At the same time, it has Janus double-sided asymmetric adhesion, which can be repeatedly attached and separated as needed, and can be used for physiological electrical signal monitoring.

[0005] The technical solution of this invention is:

[0006] A polydopamine biogel electrode is a porous hydrogel whose main components include polyacrylamide, dopamine hydrochloride, liquid metal, and glycerin. Polyacrylamide serves as a framework, dopamine hydrochloride provides adhesion, liquid metal is used to reduce material impedance and provide conductivity, and glycerin is used for moisturizing.

[0007] Based on the total mass of the polydopamine biogel electrode being 100%, the mass percentage of each component is as follows:

[0008] Polyacrylamide 54%-61%

[0009] Dopamine hydrochloride 3%-4%

[0010] Liquid metal 6%-18%

[0011] Glycerin 26%-30%

[0012] A method for preparing a polydopamine biogel electrode includes the following steps:

[0013] Step 1: Prepare PDA@EGaIn solution. The specific method is as follows: Mix dopamine hydrochloride and liquid metal in a buffer solution. During mixing, first perform ultrasonic dispersion, and then perform magnetic stirring to obtain PDA@EGaIn solution.

[0014] Step 2: Prepare the PDA@EGaIn-PAM prepolymer solution. The specific method is as follows: add acrylamide and glycerol to the PDA@EGaIn solution obtained in Step 1, stir, and then add the initiator and crosslinking agent to obtain the PDA@EGaIn-PAM prepolymer solution.

[0015] Step 3: Pour the PDA@EGaIn-PAM prepolymer solution obtained in Step 2 into the electrode mold, seal it, and place it in an oven to heat and undergo a crosslinking reaction. After the reaction is completed, cool it down. After the temperature drops to room temperature, take out the product and add AlCl3 solution to the product surface for immersion. After immersion, a polydopamine biogel electrode with double-sided asymmetric adhesion is obtained.

[0016] In step 1, the buffer solution is at least one of phosphate buffer solution, borate buffer solution, and hydrochloric acid buffer solution, with a pH value of 7-9; the concentration of the buffer solution is 30-60 mM / L; the concentration of dopamine hydrochloride is 1-15 mg / ml, and the mass ratio of dopamine hydrochloride to liquid metal is 0.21-0.64:1; the mass ratio of dopamine hydrochloride and liquid metal to the buffer solution is 0.2-0.8 g:10 ml; the mixing temperature is 20-30℃, the ultrasonic dispersion power is 200-400 W, the ultrasonic dispersion time is 20-30 min, and the magnetic stirring time is 10-30 h; the liquid metal is at least one of gallium, mercury, gallium-indium alloy, gallium-indium-tin alloy, bismuth-tin alloy, and bismuth-tin-lead-indium alloy; more preferably, the liquid metal is a gallium-indium alloy, wherein the mass fraction of gallium in the gallium-indium alloy is 75.5% and the mass fraction of indium is 24.5%;

[0017] In step 2, the mass ratio of acrylamide to glycerol is 1.6-2:1g, and the ratio of PDA@EGaIn solution to glycerol is 10-12ml:1g; the mass ratio of initiator to glycerol is 20mg-25mg:1g, and the mass ratio of initiator to crosslinking agent is 1:1; the stirring time is 0.5-2h; the initiator is at least one of benzoyl peroxide, benzoyl tert-butyl peroxide, methyl ethyl ketone peroxide, ammonium persulfate, and potassium persulfate; the crosslinking agent is at least one of dimethylaminopropylamine, tetramethylethylenediamine, and N,N'-methylenebisacrylamide.

[0018] In step 3, the heating temperature is 60-80℃, with an optimal temperature of 75℃, and the heating time is 0.5-1h, with an optimal temperature of 50min; the concentration range of the AlCl3 solution is 20-40wt%, and the soaking time is 5-20min.

[0019] An application of a polydopamine biogel electrode involves attaching the prepared bi-sided asymmetric adhesive polydopamine biogel electrode to the skin as a sensor to measure bioelectrical signals such as electrocardiogram (ECG), electroencephalogram (EEG), or electromyogram (EMG).

[0020] Due to the adoption of the above technical solution, the beneficial effects achieved by this invention are:

[0021] (1) This invention uses dopamine hydrochloride to stably disperse liquid gallium indium alloy droplets in hydrogel. Polydopamine is formed by in-situ polymerization of dopamine hydrochloride monomers on liquid metal droplets, which effectively prevents the aggregation of liquid gallium indium alloy droplets. While ensuring that the gel electrode has a certain adhesion strength and mechanical properties, the conductivity of the gel is further improved.

[0022] (2) This invention uses dopamine and acrylamide as synthetic raw materials. The resulting gel has good tensile properties, adhesion and biocompatibility, and high adhesion to skin tissue without causing irritation. By complexing dopamine with AlCl3, the adhesion properties of the gel surface are changed, giving the dopamine gel the characteristic of double-sided asymmetric adhesion. Moreover, there is no adhesive residue after peeling, and it will not cause skin pain.

[0023] (3) The present invention adds liquid metal gallium indium alloy conductive molecules to the raw material components, which can quickly and accurately transmit the bioelectric signals generated by the heart to the electrode pads. Real-time acquisition of electrocardiogram signals can be realized through external signal acquisition and data module; at the same time, the direct contact between the gel and the skin tissue can realize signal sensing with high signal-to-noise ratio and high sensitivity.

[0024] (4) The highly adhesive biogel electrode prepared by the method of the present invention uses materials that are free of hazardous chemicals, ensuring excellent biocompatibility. Furthermore, the preparation method of the highly adhesive biogel electrode in the present invention requires gelatin, a polymer material that is inexpensive, readily available, and environmentally friendly, which is conducive to industrial promotion.

[0025] (5) This invention relates to a method for preparing a highly adhesive dopamine biogel electrode, belonging to the field of bioelectrode technology. The method uses polyacrylamide, dopamine hydrochloride, liquid gallium-indium alloy, and glycerol as main raw materials, with the liquid metal as the conductive component. A three-dimensional network is formed through a crosslinking agent to obtain a biogel electrode with excellent conductivity, low skin contact impedance, good toughness, and adhesion. The hydrogel prepared by this invention can be used as a bioelectrode patch for electrocardiogram (ECG) testing systems. In terms of signal acquisition, the electrode exhibits a high signal-to-noise ratio, high signal accuracy, and lower impedance and skin interface impedance. Furthermore, the preparation method of this invention is simple and suitable for large-scale production and widespread application. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the preparation process of the polydopamine biogel electrode of the present invention;

[0027] Figure 2 These are photographs of the polydopamine biogel prepared by the method of this invention.

[0028] Figure 3 This is a microstructure image of the polydopamine biogel prepared by the method of this invention;

[0029] Figure 4 XPS spectrum and Ga 2p high-resolution spectrum of polydopamine biogel prepared by the method of this invention;

[0030] Figure 5 This is a graph showing the tensile and adhesive force test data of the polydopamine biogel prepared by the method of this invention;

[0031] Figure 6 This is a comparison chart of the frequency impedance curve of the polydopamine biogel prepared by the method of this invention and the impedance of a commercial electrode.

[0032] Figure 7 This is the impedance diagram of the polydopamine biogel electrode prepared by the method of this invention;

[0033] Figure 8 This is a schematic diagram and test curve of the interfacial impedance of the polydopamine biogel electrode prepared by the method of this invention;

[0034] Figure 9These are electrocardiograms and noise data of polydopamine biogel electrodes prepared by the method of this invention;

[0035] Figure 10 This is a bar chart showing the electrocardiogram signal, noise, and signal-to-noise ratio of the polydopamine biogel electrode prepared by the method of this invention;

[0036] Figure 11 This is the impedance-time curve of the polydopamine biogel electrode prepared by the method of this invention. Detailed Implementation

[0037] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0038] like Figure 1 As shown, a method for preparing a polydopamine biogel electrode includes the following steps:

[0039] Step 1: Prepare PDA@EGaIn solution. The specific method is as follows: Mix dopamine hydrochloride and liquid metal in a buffer solution. During mixing, first perform ultrasonic dispersion, and then perform magnetic stirring to obtain PDA@EGaIn solution.

[0040] Step 2: Prepare the PDA@EGaIn-PAM prepolymer solution. The specific method is as follows: add acrylamide and glycerol to the PDA@EGaIn solution obtained in Step 1, stir, and then add the initiator and crosslinking agent to obtain the PDA@EGaIn-PAM prepolymer solution.

[0041] Step 3: Pour the PDA@EGaIn-PAM prepolymer solution obtained in Step 2 into the electrode mold, seal it, and place it in an oven to heat and undergo a crosslinking reaction. After the reaction is completed, cool it down. After the temperature drops to room temperature, take out the product and add AlCl3 solution to the product surface for immersion. After immersion, a polydopamine biogel electrode with double-sided asymmetric adhesion is obtained.

[0042] Example 1

[0043] A method for preparing a polydopamine biogel electrode specifically includes the following steps:

[0044] Step 1: Weigh 0.128 g (0.04 wt%) of dopamine hydrochloride and 0.2 g (0.06 wt%) of liquid gallium-indium alloy and add them to 10 ml of hydrochloric acid buffer solution. Use a cell disruptor with an ultrasonic power of 300 W to sonicate in an ice bath for 25 min. Then stir at room temperature for 12 h to allow the dopamine monomer to completely polymerize and obtain PDA@0.2 LM solution. The gallium-indium alloy has a gallium mass fraction of 75.5% and an indium mass fraction of 24.5%. The concentration of the hydrochloric acid buffer solution is 0.05 mol / L and the pH value is 8.5.

[0045] Step 2: Weigh 2g (0.60wt%) acrylamide and 1g (0.30wt%) glycerol and add them to the solution prepared in Step 1. Stir at a constant temperature for 1 hour to ensure complete dissolution. Then, add 20mg of potassium persulfate initiator and 20mg of N,N'-methylenebisacrylamide crosslinking agent sequentially. After thorough stirring, a PDA@0.2LM-PAM prepolymer solution is obtained.

[0046] Step 3: Pour the prepolymer solution obtained in Step 2 into the electrode mold, seal it, and place it in an oven at 75°C for 50 minutes. After the temperature drops to room temperature, add 3 drops of 30% wt AlCl3 solution to the surface and soak for 10 minutes to obtain a polydopamine biogel electrode with double-sided asymmetric adhesion, which is named PDA-0.2LM hydrogel.

[0047] Example 2

[0048] The difference from Example 1 is that the mass of the liquid metal gallium indium alloy added in step 1 is 0.4 g (0.11 wt%), and the resulting product is named PDA-0.4LM hydrogel.

[0049] Example 3

[0050] The difference from Example 1 is that the mass of the liquid metal gallium indium alloy added in step 1 is 0.6g (0.17wt%), and the resulting product is named PDA-0.6LM hydrogel.

[0051] The mechanical properties of the hydrogel electrode were tested using a Mark-10 F105IM advanced electrodynamic stage from the American company Mark-10 Instruments. The dopamine biogel electrode (20mm×10mm×1mm) was placed in a tensile fixture and subjected to tensile performance testing at a speed of 10mm / min. For the adhesion test, the hydrogel was placed between two adhesion substrates, with the contact surface between the substrate and the gel being a circle with a diameter of 10mm. The adhesion performance of the hydrogel was tested using the advanced electrodynamic stage.

[0052] The electrical properties of hydrogel electrodes were measured using a CHI760E electrochemical workstation from Shanghai Chenhua Co., Ltd. Dopamine biogel electrodes (10mm × 10mm × 2mm) were bonded together to form an electrode pair. The working electrode was connected to the common pin of one electrode, and the reference electrode was short-circuited to the common pin of the other electrode. The impedance and impedance-frequency curves of the electrode pair were measured using this two-electrode system. The skin interface impedance testing method is as follows: Figure 9 As shown, the working electrode (WE), reference electrode (RE), and counter electrode (CE) were placed at the same distance from the skin for testing.

[0053] Figure 2 This is a photograph of the PDA-0.2LM gel electrode used in Example 1. Figure 2 It can be seen that the PDA-0.2LM gel electrode can adhere well to the skin surface.

[0054] Figure 3 a and Figure 3 Figure b shows an SEM image of the hydrogel of Example 1 of the present invention, with scale bars of (10 μm, 1 μm). As can be seen from the figure, the hydrogel has a uniform porous structure with a smooth structure and good internal cross-linking distribution. Furthermore, the PDA@EGaIn particles are uniformly dispersed in the porous gaps of the hydrogel.

[0055] Figure 4 a and Figure 4 b shows the XPS spectrum of the PDA-0.6LM hydrogel prepared in Example 3 and its high-resolution C1s, O 1s and Ga 2p spectra. It mainly contains three signal peaks: C1s (284eV), N 1s (398eV) and O 1s (530eV). Among them, the high-resolution XPS spectrum of Ga 2p (530eV) shows that the characteristic peak signal of Ga(III) is higher. The above results prove that Ga mainly exists in the oxidation state.

[0056] The tensile test results of the product obtained in Example 1 are as follows: Figure 5 As shown in Figure a, the maximum tensile strength of this gel electrode is 234 kPa, and the elongation at break is 250%. Furthermore, the adhesion of the product obtained in Example 1 was tested as follows: Figure 7 As shown, its maximum adhesion strength is 5.9 kPa.

[0057] Impedance tests were performed on the products obtained in Examples 1-3 and the commercial electrode (AMBU N-00-S / 25 gel electrode from Denmark) as follows: Figure 6 and Figure 7 As shown, in 10-10 5Within the Hz frequency range, the dopamine gel electrodes with varying contents of gallium-indium alloy conductive particles all exhibited significantly lower impedance values ​​than the commercially available electrodes. At 100Hz, the impedance values ​​of the dopamine gel electrodes were all below 100Ω, with the optimal value being 41.5Ω, while the impedance of the commercially available electrodes reached 1310Ω. Furthermore, the skin interface impedance test results for the PDA-0.4LM product obtained in Example 2 and the commercially available electrodes are as follows: Figure 8 As shown in b, in Figure 8 The interfacial impedance data for b show that the dopamine gel electrode exhibits resistance in the range of 1-10. 5 The impedance value within the Hz frequency range is still better than that of commercial electrodes, which also proves that the hydrogel has excellent conductivity.

[0058] The device utilizes flexible circuitry combined with hydrogel to read, transmit, and process electrocardiogram signals. The dopamine carboxyl groups and tannic acid carboxyl groups on the hydrogel electrodes can form a strong adhesion to human skin, enabling long-term wear. When it needs to be removed, it can be easily torn off, achieving controllable wear and removal.

[0059] like Figure 9 As shown, a control group was used to conduct ECG signal acquisition experiments using disposable commercial electrode patches. The same ECG signal acquisition experiments were performed on the PDA-0.4LM product obtained in Example 2. The ECGs obtained in Example 2 were essentially similar to those obtained using the commercial electrodes. Figure 10 It can be seen that the products obtained in Examples 1-3 have a better signal-to-noise ratio than traditional commercial electrodes, with a maximum signal-to-noise ratio of 21.0 dB. Furthermore, this dopamine gel electrode maintains a low electrochemical impedance even after 7 days. Figure 11 As can be seen, its resistance remained below 120Ω, and it still had good conductivity after a week.

[0060] In summary, this invention has developed a highly adhesive polydopamine biogel electrode. This biogel electrode can provide long-term, high-quality electrocardiogram (ECG) recordings. Furthermore, this biogel electrode exhibits good biocompatibility and long-term stable signal acquisition performance, providing a long-term guarantee of stability for ECG signal acquisition systems. The highly adhesive biogel electrode prepared using the method of this invention has high conductivity, good biocompatibility, and excellent signal acquisition performance, making it compatible with commonly used ECG signal acquisition equipment.

[0061] Although the present invention has been described in detail with reference to the accompanying drawings and preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention.

Claims

1. A method for preparing a polydopamine biogel electrode, characterized in that... Includes the following steps: Step 1: Prepare the PDA@EGaIn solution. The specific method is as follows: Mix dopamine hydrochloride and liquid gallium indium alloy in a buffer solution. During mixing, first perform ultrasonic dispersion, then magnetic stirring to ensure complete polymerization of the dopamine monomers, thus obtaining the PDA@EGaIn solution. The concentration of dopamine hydrochloride is 1-15 mg / ml, and the mass ratio of dopamine hydrochloride to liquid metal is 0.21-0.64:

1. The mass ratio of dopamine hydrochloride and liquid metal to the buffer solution is 0.2-0.8 g:10 ml. Step 2: Prepare the PDA@EGaIn-PAM prepolymer solution. Specifically, add acrylamide and glycerol to the PDA@EGaIn solution obtained in Step 1, stir, and then add the initiator and crosslinking agent to obtain the PDA@EGaIn-PAM prepolymer solution. The mass ratio of acrylamide to glycerol is 1.6-2:1, and the ratio of PDA@EGaIn solution to glycerol is 10-12 ml: 1 g. The crosslinking agent is N,N'-methylenebisacrylamide. Step 3: Pour the PDA@EGaIn-PAM prepolymer solution obtained in Step 2 into the electrode mold, seal it, and place it in an oven to heat and undergo a crosslinking reaction. After the reaction is completed, cool it down. After the temperature drops to room temperature, take out the product and add AlCl3 solution to the product surface for immersion. After immersion, a polydopamine biogel electrode with double-sided asymmetric adhesion is obtained.

2. The method for preparing a polydopamine biogel electrode according to claim 1, characterized in that: In step 1, the buffer solution is at least one of phosphate buffer solution, borate buffer solution, and hydrochloric acid buffer solution, with a pH value of 7-9; the concentration of the buffer solution is 30-60 mM / L; the mixing temperature is 20-30℃; the ultrasonic dispersion power is 200-400W; the ultrasonic dispersion time is 20-30 min; and the magnetic stirring time is 10-30 h.

3. The method for preparing a polydopamine biogel electrode according to claim 1, characterized in that: The gallium-indium alloy contains 75.5% gallium by mass and 24.5% indium by mass.

4. The method for preparing a polydopamine biogel electrode according to claim 1, characterized in that: In step 2, the mass ratio of initiator to glycerol is 20mg-25mg:1g; the mass ratio of initiator to crosslinking agent is 1:1; the stirring time is 0.5-2h; and the initiator is at least one of benzoyl peroxide, benzoyl tert-butyl peroxide, methyl ethyl ketone peroxide, ammonium persulfate, and potassium persulfate.

5. The method for preparing a polydopamine biogel electrode according to claim 1, characterized in that: In step 3, the heating temperature is 60-80℃, the heating time is 0.5-1h, the concentration range of AlCl3 solution is 20wt%-40wt%, and the soaking time is 5-20 min.

6. The method for preparing a polydopamine biogel electrode according to claim 5, characterized in that: In step 3, the heating temperature is 75°C and the heating time is 50 minutes.

7. An application of a polydopamine biogel electrode for non-disease diagnosis and treatment purposes, characterized in that: The polydopamine biogel electrode with bi-sided asymmetric adhesion prepared by the method described in claim 1 is attached to the skin as a sensor for measuring electrocardiogram (ECG), electroencephalogram (EEG), or electromyogram (EMG) signals.

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