An electronic-ion bicontinuous network composite electrode material, a preparation method thereof and application thereof in biological electrical signal monitoring

Abstract

The present application relates to an electronic-ion bicontinuous network composite electrode material and its preparation method and application in biological electrical signal monitoring, and belongs to the field of material science and engineering technology and bioelectronics. The composite electrode material prepared by the method comprises nickel-coated polyurethane sponge and eutectic gel, and an electronic-ion bicontinuous conductive network is constructed by pouring the eutectic gel into the sponge. First, a choline chloride / glycerol eutectic solvent is prepared, and is mixed with a gelatin aqueous solution to obtain a eutectic gel precursor; then the nickel-coated polyurethane sponge is immersed in the heated precursor, and after cooling and gelation, the composite electrode is obtained. The composite electrode material prepared by the present application has skin adaptability mechanical properties and excellent environmental stability, has a low skin-electrode impedance, and exhibits a high signal-to-noise ratio and a long-term stable signal acquisition capability in electrophysiological monitoring. The present application has the advantages of high activity, strong stability and wide application range, and has significant advantages over the traditional Ag / AgCl electrode.

Description

Technical Field

[0001] This invention relates to electron-ion dual continuous network composite electrode materials, their preparation methods, and their applications in bioelectric signal monitoring, belonging to the fields of materials science and engineering technology and bioelectronics. Background Technology

[0002] With the rapid development of wearable health monitoring devices, high-fidelity, long-term stable physiological signal acquisition technology has attracted widespread attention. Electrocardiogram (ECG), electroencephalogram (EEG), and electromyography (EMG) are important biomarkers for diagnosing cardiovascular diseases, neurological diseases, and for rehabilitation assessment. However, achieving long-term dynamic monitoring faces two major challenges: First, traditional Ag / AgCl electrodes rely on conductive paste and skin pretreatment, which easily causes skin irritation. Furthermore, the rigid structure (modulus 1-10 GPa) is severely mismatched with the mechanical properties of soft tissue (modulus 0.1-100 kPa), leading to motion artifacts and interfacial impedance fluctuations. Second, while hydrogel-based electrodes possess good flexibility, their moisture evaporates easily, causing performance degradation. They also primarily rely on ionic conductivity, resulting in low electronic conductivity, which limits signal fidelity.

[0003] To address these challenges, researchers have attempted to incorporate conductive fillers into hydrogels to enhance conductivity or employ hydrophobic solvents to improve environmental stability. However, existing methods often struggle to simultaneously achieve high conductivity, mechanical compliance, and long-term environmental stability. Therefore, there is an urgent need to develop novel electrode materials that can synergistically combine electronic and ionic conductivity, while also possessing mechanical adaptability and environmental stability, to meet the demands of next-generation wearable bioelectronic devices.

[0004] This invention is the first to propose and realize the fabrication of a composite electrode material that combines high conductivity, skin-adaptive mechanical properties, and long-term environmental stability by infusing a eutectic gel into a nickel-coated polyurethane sponge to construct an electron-ion dual continuous conductive network. This material exhibits a high signal-to-noise ratio and excellent long-term stability in electrophysiological monitoring, making it suitable for high-fidelity acquisition of various bioelectrical signals such as electrocardiograms, electroencephalograms, and electromyograms. Summary of the Invention

[0005] 1. Objective of this invention

[0006] The purpose of this invention is to propose a method for preparing an electronic-ion dual continuous network composite electrode material, which can obtain a composite electrode material with high electronic conductivity, ionic conductivity, skin-adaptive mechanical properties and long-term environmental stability, to replace existing Ag / AgCl electrodes and hydrogel electrodes, improve the signal-to-noise ratio and long-term stability of bioelectrical signal monitoring, and promote the development of wearable health monitoring technology.

[0007] 2. Key Invention Points of this Technology

[0008] The key points of this invention are as follows:

[0009] (1) Mix choline chloride and glycerol in a molar ratio of 1:8 and stir at 80°C for 3 hours to obtain a clear and homogeneous eutectic solvent (DES).

[0010] (2) Disperse gelatin in deionized water and stir at 70°C for 1 hour to obtain a gelatin aqueous solution;

[0011] (3) Add the DES obtained in step (1) to the gelatin aqueous solution obtained in step (2) and stir at 70°C for 4 hours to obtain a homogeneous eutectic gel precursor solution without bubbles;

[0012] (4) Immerse the nickel-coated polyurethane sponge (PU@Ni) in the precursor solution obtained in step (3), keep it at 70°C for 1 hour, and supplement it with low-power ultrasonic treatment to fully wet the sponge pores with the precursor.

[0013] (5) Take out the soaked sponge, cool it to room temperature, and let it stand for 5 minutes to gel, so as to obtain the electron-ion dual continuous network composite electrode material.

[0014] In this invention, the nickel-coated polyurethane sponge retains the three-dimensional porous structure of the polyurethane sponge, with the nickel layer forming continuous electronic conductive pathways on the pore walls. The eutectic gel, composed of choline chloride, glycerol, and gelatin, forms an ionic conductive medium through a hydrogen bond network, while also exhibiting good moisturizing properties and skin adhesion. The combination of these two components forms a dual continuous electron-ion conductive network, synergistically achieving efficient charge transport and interfacial coupling.

[0015] The proposed electron-ion dual-continuous network composite electrode material simultaneously achieves high electronic conductivity, low skin-electrode contact impedance, skin-adaptive mechanical properties, and long-term environmental stability. This material enables high signal-to-noise ratio signal acquisition in electrophysiological monitoring and can operate continuously for extended periods, significantly outperforming existing electrode materials.

[0016] (5) Drawings of the present invention

[0017] Figure 1 These are microstructure characterization images of the PU@Ni sponge and composite electrode material prepared by the method of this invention. (a) Cross-sectional SEM image of the PU@Ni sponge, showing a uniform nickel coating layer; (b) Cross-sectional SEM image of the composite electrode material after freeze-drying, showing that the gel completely fills the sponge pores; (c) FTIR spectrum of the composite electrode material, showing the enhanced features of the hydrogen bond network.

[0018] Figure 2These are mechanical property diagrams of the composite electrode material prepared by the method of this invention. (a) Stress-strain curve; (b) Fracture strain and modulus of the composite material; (c) Cyclic tensile test curve, showing the fatigue resistance of the material; (d) Cyclic compression test curve, showing the structural stability of the material.

[0019] Figure 3 This is an electrical property diagram of the composite electrode material prepared by the method of this invention, and a skin-electrode contact impedance frequency response curve.

[0020] Figure 4 These are bioelectrical signal monitoring performance graphs of the composite electrode material prepared by the method of this invention. (a) Impedance changes during EEG testing; (b) Steady-state visual evoked potentials obtained using this electrode.

[0021] (6) Embodiments of the present invention

[0022] The following describes embodiments of the method of the present invention:

[0023] Example 1

[0024] Preparation of PU@Ni-ChCl-egel composite electrode.

[0025] Choline chloride and glycerol were mixed at a molar ratio of 1:8 and stirred at 80°C for 3 hours to obtain a clear and homogeneous eutectic solvent. 2.2 g of gelatin was weighed and dispersed in 4 mL of deionized water, and stirred at 70°C for 1 hour to obtain a gelatin aqueous solution. 7 mL of the eutectic solvent was added dropwise to the gelatin aqueous solution, and stirred at 70°C for 4 hours to obtain a eutectic gel precursor solution. PU@Ni sponge (porosity >90%, pore size 200-400 μm) was immersed in the precursor solution and kept at 70°C for 1 hour, supplemented with low-power ultrasonic treatment to promote penetration. The immersed sponge was removed, cooled to room temperature, and allowed to stand for 5 minutes to gel, thus obtaining the PU@Ni-ChCl-egel composite electrode material.

[0026] Example 2

[0027] Mechanical property testing of composite electrode materials.

[0028] The composite electrode material prepared in Example 1 was cut to standard dimensions and subjected to uniaxial tensile testing using a universal testing machine at a tensile rate of 10 mm / min. The results showed that the fracture strain of the composite material was 70%, and the Young's modulus was 0.21 MPa. Cyclic tensile testing (20% strain, 10 cycles) showed that the energy loss stabilized rapidly after the first cycle, exhibiting excellent fatigue resistance. Cyclic compression testing (50% strain, 10 cycles) also showed a stable mechanical response.

[0029] Example 3

[0030] Electrical performance testing of composite electrode materials.

[0031] The DC resistance of the composite electrode material prepared in Example 1 was measured using the four-probe method. The results showed that the resistance slowly increased from 17 Ω to 27 Ω within a strain range of 0-35%, exhibiting strain insensitivity. Electrochemical impedance spectroscopy (EIS) tests showed that the bulk impedance of the composite electrode at 20 Hz was 27 Ω, which was about three orders of magnitude lower than that of the pure eutectic gel (15 kΩ). Skin-electrode contact impedance tests (10 Hz) showed that the composite electrode impedance was below 5 kΩ and remained stable during 24 hours of continuous monitoring.

[0032] Example 4

[0033] Applications of composite electrode materials in electrocardiogram monitoring.

[0034] The composite electrode material prepared in Example 1 was connected to an ECG acquisition system using a three-electrode configuration, with the electrodes placed at corresponding positions on the chest. Resting ECG signals were acquired and compared with those obtained using commercial Ag / AgCl electrodes. Results showed that the composite electrode acquired clear PQRST waveforms with a signal-to-noise ratio (SNR) of 49.7 dB, higher than that of the commercial electrode. 48-hour continuous ECG monitoring showed that the composite electrode consistently maintained a SNR above 45 dB, indicating stable signal quality.

[0035] Example 5

[0036] Applications of composite electrode materials in electroencephalography (EEG) monitoring.

[0037] The composite electrode material prepared in Example 1 was applied to a steady-state visual evoked potential (SSVEP) EEG acquisition system using an eight-channel electrode cap and 12 stimulation frequencies. Power spectrum analysis of the acquired EEG signals revealed a clear frequency-locked SSVEP response. Compared to commercial wet electrodes, the composite electrode maintained a stable classification accuracy (>50%) during 2 hours of continuous testing, while the accuracy of commercial electrodes decreased significantly due to gel dehydration. Long-term monitoring over 24 hours showed that the composite electrode maintained a classification accuracy above 50%, and the scalp-electrode impedance remained stable at approximately 6 kΩ.

[0038] Example 6

[0039] Application of composite electrode materials in electromyography monitoring.

[0040] The composite electrode material prepared in Example 1 was placed on the back of the forearm, and electromyographic signals were collected at different grip forces (10 lb, 20 lb, 30 lb). The results showed that the amplitude of the electromyographic signals collected by the composite electrode increased with increasing grip force, and was higher than that of the pure eutectic gel electrode at all grip force levels, especially showing higher sensitivity at a low grip force of 10 lb.

[0041] Example 7

[0042] Environmental stability testing of composite electrode materials.

[0043] The composite electrode material prepared in Example 1 was placed at 25°C and 55% relative humidity, and its mass change was recorded over 48 hours. The results showed that the mass retention rate of the composite electrode material was >95%, which was far superior to that of the pure eutectic gel. Further immersion of the composite electrode in a mixture of glycerol and glycerol-water resulted in a significantly lower mass gain rate than that of the pure eutectic gel, indicating that the PU@Ni framework effectively suppressed gel swelling and solvent evaporation.

[0044] Example 8

[0045] Preparation of PU@Ni-ChCl-egel composite electrode

[0046] Same as in Example 1, except that the molar ratio of choline chloride to glycerol is changed from 1:8 to 1:7.

[0047] Example 9

[0048] Preparation of PU@Ni-ChCl-egel composite electrode

[0049] Same as in Example 1, except that the molar ratio of choline chloride to glycerol is changed from 1:8 to 1:9.

[0050] Example 10

[0051] Preparation of PU@Ni-ChCl-egel composite electrode

[0052] Same as in Example 1, except that the amount of gelatin used was changed from 2.2 g to 2.0 g.

[0053] Example 11

[0054] Preparation of PU@Ni-ChCl-egel composite electrode

[0055] Same as in Example 1, except that the amount of gelatin used was changed from 2.2 g to 2.4 g.

Claims

1. A method for preparing an electron-ion dual continuous network composite electrode material, characterized in that... The method includes the following steps: (1) Mix choline chloride and glycerol in a molar ratio of 1:8 and stir at 80°C for 3 hours to obtain a clear and homogeneous eutectic solvent; (2) Disperse gelatin in deionized water and stir at 70°C for 1 hour to obtain a gelatin aqueous solution; (3) The eutectic solvent obtained in step (1) is added dropwise to the gelatin aqueous solution obtained in step (2), and stirred at 70°C for 4 hours to obtain a eutectic gel precursor solution; (4) Immerse the nickel-coated polyurethane sponge in the precursor solution obtained in step (3) and keep it at 70°C for 1 hour to allow the precursor to fully wet the pores of the sponge. (5) Take out the soaked sponge, cool it to room temperature, and let it stand to gel, so as to obtain the electron-ion dual continuous network composite electrode material.

2. The preparation method according to claim 1, characterized in that, In step (2), add 2.2g of gelatin to every 4 mL of deionized water.

3. The preparation method according to claim 1, characterized in that, The volume ratio of the eutectic solvent to the gelatin aqueous solution in step (3) is 7:

4.

4. The preparation method according to claim 1, characterized in that, The infiltration process described in step (4) is supplemented with low-power ultrasonic treatment.

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