Adaptive dynamic electroencephalography electrode and method of making same

Abstract

The application belongs to the technical field of brain-computer interface, and particularly discloses a self-adaptive dynamic electroencephalogram electrode and a preparation method thereof. The electrode effectively solves the poor wearing comfort and mechanical mismatch under dynamic activities of the existing gel electrode. The electroencephalogram electrode has a three-layer structure from bottom to top, namely a contact layer, a buffer layer and a transmission layer. The contact layer is used for contacting biological tissues, the buffer layer is used for stress buffering and signal transmission, and the transmission layer is used for connecting electronic circuits. The modulus of the contact layer is 0.1-1 kPa, the modulus of the buffer layer is 1-10 kPa, and the modulus of the transmission layer is 10-100 kPa. The core material of the electroencephalogram electrode is a polyacrylic acid skeleton and metal ions. The application realizes the stepwise change of the mechanical properties of the single-component hydrogel from bottom to top, retains the dynamic reversibility and biological safety, and realizes non-invasive, high comfort and stable signal acquisition.

Description

Technical Field

[0001] This invention belongs to the field of brain-computer interface technology, and particularly relates to an adaptive dynamic EEG electrode and its preparation method. Background Technology

[0002] With the rapid development of wearable medical devices and biosensor technology, the demand for high-fidelity, comfortable, and long-term stable physiological signal acquisition is becoming increasingly urgent. Currently, commercially available and widely used physiological signal acquisition electrodes are mainly rigid electrodes. The mechanical properties (such as modulus and elasticity) of rigid materials are mismatched with those of human skin, resulting in high interfacial contact impedance and signal acquisition distortion. In particular, during dynamic movement or long-term wear, they are prone to skin irritation or falling off, causing discomfort.

[0003] Non-invasive brain-computer interface (BCI) technology, due to its non-invasive and safe characteristics, has broad application prospects in fields such as medical rehabilitation, neurofeedback, and human-computer interaction. Electroencephalogram (EEG) signal acquisition is a crucial component of BCI, and its quality directly affects system performance. Gel electrodes, as the core interface element between the scalp and the signal acquisition device, are of paramount importance. However, existing gel electrode technology has significant drawbacks, severely restricting the long-term comfort, dynamic stability, and signal reliability of BCI, specifically in the following aspects.

[0004] (1) Poor wearing comfort and biocompatibility issues: Existing electrodes often use rigid substrate materials (such as rigid plastics or metals). When these rigid materials are in long-term contact with soft and sensitive scalp tissue, they create local pressure points, leading to strong discomfort for users. Continuous pressure is more likely to cause redness, swelling, itching, or even allergic reactions in the contact area, significantly reducing user compliance and making it difficult to meet the needs of long-term continuous monitoring (such as epilepsy monitoring and neurofeedback training).

[0005] (2) Mechanical mismatch and signal instability under dynamic activities: When the human head is in a natural state (such as speaking, chewing, facial expressions, slight movements), the scalp tissue will deform. Existing rigid electrodes or electrode structures lacking self-adaptive capabilities cannot effectively follow these dynamic changes, resulting in poor contact at the electrode-skin interface, fluctuations in contact pressure, or even instantaneous separation. This mechanical mismatch directly causes a significant increase in interface contact impedance, signal baseline drift, increased noise (such as power frequency interference), and attenuation of the effective signal, severely degrading the signal quality and stability in dynamic application scenarios, and even causing signal acquisition interruption.

[0006] (3) Structural mechanical contradictions of homogeneous hydrogel materials: Current mainstream hydrogel electrode materials typically possess uniform mechanical properties (modulus). This leads to an irreconcilable contradiction: to conform to the skin's contours and cushion micro-movements to improve comfort and interface stability, the material needs to have a low modulus (high flexibility / elasticity); however, to ensure the overall shape retention of the electrode structure during wear and movement, prevent excessive deformation that could damage internal wires or cause contact point displacement, and provide necessary spatial positioning support for the electrode array, the material needs to have a relatively high modulus (rigidity / support). Existing homogeneous hydrogels cannot simultaneously meet these conflicting mechanical property requirements in a single material system, becoming a core bottleneck in improving the overall performance of electrodes.

[0007] (4) Insufficient long-term electrochemical stability of conductive gels: Although commercially available conductive gels can provide low interfacial impedance in the initial stage, their conductivity significantly decreases during long-term use (from several hours to 24 hours). The main reasons include: evaporation of water within the gel or absorption of electrolytes by the skin leading to decreased conductivity; penetration of secretions such as sebum and sweat altering the interfacial chemical environment; and aging of the gel itself or interaction with the skin leading to deterioration of the conductive network structure. The time-varying increase in contact impedance directly causes attenuation of the acquired signal amplitude and a decrease in the signal-to-noise ratio, making it impossible to guarantee the signal quality stability required for long-term continuous recording.

[0008] Therefore, existing gel electrode technology is limited by inherent defects such as limited material mechanical properties, poor dynamic adaptability, and unstable long-term conductivity, making it difficult to meet the requirements of next-generation non-invasive BCI for high comfort, high dynamic robustness, and high signal quality durability. There is an urgent need to develop a novel gel electrode structure or material solution that can effectively solve the above problems, especially overcoming the performance contradiction between flexible adhesion and rigid support in homogeneous materials. Summary of the Invention

[0009] One objective of this invention is to provide an adaptive dynamic EEG electrode that effectively solves the problems of poor wearing comfort and mechanical mismatch under dynamic activities of existing gel electrodes.

[0010] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0011] The adaptive dynamic EEG electrode has a stepped three-layer structure, consisting of a contact layer, a buffer layer, and a transmission layer from bottom to top. The contact layer is used to contact biological tissue, the buffer layer is used for stress buffering and signal transmission, and the transmission layer is used to connect electronic circuits.

[0012] The modulus of the contact layer is 0.1 to 1 kPa, the modulus of the buffer layer is 1 to 10 kPa, and the modulus of the transmission layer is 10 to 100 kPa.

[0013] Furthermore, using polyacrylic acid as a backbone, containing Al 3+ or Fe 3+ or Mg 2+ .

[0014] Another object of the present invention is to provide a method for preparing the adaptive dynamic EEG electrode described in the above embodiments, comprising the following steps: S1, preparation of prepolymer solution: 0.2 wt% acrylic monomer, 0.03 wt% photoinitiator, 0.06 wt% crosslinking agent, γ-PGA, buffer solution and substance A are mixed evenly to obtain a prepolymer solution; wherein substance A is any one of sodium alginate, hyaluronic acid and chitosan-CuCl2.

[0015] S2. Different concentrations of metal ions are added to the prepolymer solution to obtain a contact layer solution, a buffer layer solution, and a transport layer solution, respectively. The contact layer solution has the lowest metal ion concentration, the transport layer solution has the highest metal ion concentration, and the buffer layer solution has a metal ion concentration in between. The metal ion is Al. 3+ Fe 3+ Mg 2+ Any one of them.

[0016] S3, Microfluidic Layered Infusion: Contact layer solution, buffer layer solution and transport layer solution are injected separately through Y-shaped microchannels, and the laminar interface polymerizes to form a stepped structure.

[0017] S4. Crosslinking and curing: Adaptive dynamic EEG electrodes are prepared by UV irradiation at a wavelength of 365nm for 1-5 minutes.

[0018] Furthermore, in step S1, the prepolymer solution is prepared as follows: γ-PGA is added to the buffer solution and stirred in a water bath at 40±2℃ until dissolved. Then, substance A is added and stirred at 40±2℃ until no particles are present, thus preparing a polysaccharide solution.

[0019] Mix 0.2 wt% acrylic monomer, 0.03 wt% photoinitiator, and 0.06 wt% crosslinking agent, and add the mixture dropwise to the polysaccharide solution at a rate of 1 ml / min under light-protected conditions. Stir in an ice bath at 0–4 °C for 30 min, keeping the bulk solution temperature ≤5 °C, and then disperse using ultrasonication at 40 kHz.

[0020] Furthermore, in step S2, the metal ion is Al. 3+ Al in the contact layer solution 3+ The concentration of Al in the buffer layer solution is 1 mM. 3+ The concentration of Al in the transport layer solution is 5 mM. 3+ The concentration is 20 mM.

[0021] Furthermore, in step S1, the buffer solution is a K2HPO4 solution.

[0022] Furthermore, in step S1, the photoinitiator is any one of 2-hydroxy-2-methylphenylpropanone, lithium phenyl-2,4,6-trimethylbenzoylphosphonate, and chlorophyll; the crosslinking agent is N,N'-methylenebisacrylamide and polyethylene glycol diacrylate, or cellulose nanofibers and nanoclay.

[0023] Compared with the prior art, the beneficial technical effects of the present invention are:

[0024] This invention achieves a bottom-up, stepwise leap in mechanical properties (modulus spanning three orders of magnitude) within a single-component hydrogel through the directional gradient distribution of metal ions, while preserving dynamic reversibility and biocompatibility. It also achieves non-invasive, highly comfortable, and stable signal acquisition, solving the problems of discomfort and mechanical mismatch associated with traditional electrodes. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the adaptive dynamic EEG electrode of the present invention. Detailed Implementation

[0026] Example 1: A method for preparing adaptive dynamic EEG electrodes, comprising the following steps:

[0027] S1. Preparation of prepolymer solution: Mix 0.2wt% acrylic monomer, 0.03wt% photoinitiator, 0.06wt% crosslinking agent, sodium alginate, γ-PGA and K2HPO4 buffer solution evenly to obtain prepolymer solution.

[0028] The specific steps for preparing the prepolymer solution are as follows:

[0029] (1) Add γ-PGA to K2HPO4 buffer and stir in a water bath at 40±2℃ until dissolved.

[0030] (2) Add sodium alginate to the solution prepared in step (1) and stir at 40±2℃ until there are no particles to obtain a polysaccharide solution.

[0031] (3) Mix 0.2wt% acrylic monomer, 0.03wt% photoinitiator and 0.06wt% crosslinking agent, and add them dropwise to the polysaccharide solution at a rate of 1ml / min under light-protected conditions. Stir in an ice bath at 0-4℃ for 30min, control the temperature of the main solution to ≤5℃, and disperse by ultrasonication at 40kHz.

[0032] In this embodiment, the photoinitiator is 2-hydroxy-2-methylphenylacetone, and the crosslinking agent is N,N'-methylenebisacrylamide and polyethylene glycol diacrylate.

[0033] S2. Different concentrations of metal ions are added to the prepolymer solution to obtain contact layer solution, buffer layer solution and transport layer solution respectively. Among them, the metal ion concentration in the contact layer solution is the lowest, the metal ion concentration in the transport layer solution is the highest, and the metal ion concentration in the buffer layer solution is in between.

[0034] The metal ion is Al. 3+ (aluminum chloride, aluminum hydroxide), Fe 3+ (ferric chloride), Mg 2+ Any of (magnesium chloride).

[0035] In this embodiment, the selected metal ion is Al. 3+ Al in the contact layer solution 3+ The concentration of Al in the buffer layer solution is 1 mM. 3+ The concentration of Al in the transport layer solution is 5 mM. 3+ The concentration is 20 mM.

[0036] S3, Microfluidic Layered Infusion: Contact layer solution, buffer layer solution and transport layer solution are injected separately through Y-shaped microchannels, and the laminar interface polymerizes to form a stepped structure.

[0037] S4. Crosslinking and curing: Adaptive dynamic EEG electrodes are prepared by UV irradiation at a wavelength of 365nm for 1-5 minutes.

[0038] The core materials of the adaptive dynamic EEG electrode prepared in this embodiment are: polyacrylic acid framework and Al. 3+ .like Figure 1 As shown, the EEG electrode prepared in this embodiment has a stepped three-layer structure, consisting of a contact layer, a buffer layer, and a transmission layer from bottom to top. The contact layer is used to contact biological tissue (scalp), and has ultra-soft mechanical properties (modulus of 0.1–1 kPa), belonging to Al. 3+ Low concentration region. The buffer layer is used for stress buffering and signal transmission, with moderate mechanical properties (modulus of 1-10 kPa), and belongs to Al. 3+ Transition concentration region. The transport layer is used to connect electronic circuits and has high mechanical rigidity (modulus of 10–100 kPa), belonging to Al. 3+ High concentration areas. It is worth noting that the shape of each layer of the EEG electrodes is not limited to... Figure 1 The shape shown.

[0039] Commercially available gel electrodes, commercially available dry electrodes, and the EEG electrodes prepared in this embodiment were selected, and their mechanical properties, dynamic stability, comfort, and electrochemical properties were tested respectively. The test conditions / standards and test results are shown in Table 1.

[0040] Table 1 Performance test results of different electrodes

[0041]

[0042] As shown in Table 1, the EEG electrode prepared in this embodiment outperforms commercially available gel electrodes and commercially available dry electrodes in terms of mechanical properties, dynamic stability, comfort, and electrochemical performance. This invention achieves a bottom-up, stepwise leap in mechanical properties (modulus spanning three orders of magnitude) within a single-component hydrogel through the directional gradient distribution of metal ions, while preserving dynamic reversibility and biocompatibility. It also achieves non-invasive, highly comfortable, and stable signal acquisition, solving the problems of discomfort and mechanical mismatch associated with traditional electrodes.

[0043] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for preparing adaptive dynamic EEG electrodes, characterized in that, Includes the following steps: S1. Prepolymer solution preparation: Mix 0.2wt% acrylic monomer, 0.03wt% photoinitiator, 0.06wt% crosslinking agent, γ-PGA, buffer solution and substance A evenly to obtain the prepolymer solution; Substance A is any one of sodium alginate, hyaluronic acid, and chitosan-CuCl2; S2. Different concentrations of metal ions were added to the prepolymer solution to obtain contact layer solution, buffer layer solution and transport layer solution respectively. Among them, the metal ion concentration in the contact layer solution was the lowest, the metal ion concentration in the transport layer solution was the highest, and the metal ion concentration in the buffer layer solution was in between. The metal ion is Al. 3+ Fe 3+ Mg 2+ Any one of them; S3, Microfluidic Layered Infusion: Contact layer solution, buffer layer solution and transport layer solution are injected separately through Y-shaped microchannels, and laminar interface polymerization forms a stepped structure; S4. Cross-linking and curing: Adaptive dynamic EEG electrodes are prepared by UV irradiation at a wavelength of 365nm for 1-5 minutes. The adaptive dynamic EEG electrode has a stepped three-layer structure, consisting of a contact layer, a buffer layer, and a transmission layer from bottom to top. The contact layer is used to contact biological tissue, the buffer layer is used for stress buffering and signal transmission, and the transmission layer is used to connect electronic circuits; The modulus of the contact layer is 0.1 to 1 kPa, the modulus of the buffer layer is 1 to 10 kPa, and the modulus of the transmission layer is 10 to 100 kPa.

2. The method for preparing adaptive dynamic EEG electrodes according to claim 1, characterized in that, The adaptive dynamic EEG electrode uses polyacrylic acid as a framework and contains Al. 3+ or Fe 3+ or Mg 2+ .

3. The method for preparing the adaptive dynamic EEG electrode according to claim 1, characterized in that, In step S1, the prepolymer solution is prepared as follows: Add γ-PGA to the buffer solution and stir in a water bath at 40±2℃ until dissolved. Then, add substance A and stir at 40±2℃ until no particles remain to prepare a polysaccharide solution. After mixing 0.2 wt% acrylic monomer, 0.03 wt% photoinitiator and 0.06 wt% crosslinking agent, the mixture was added dropwise to the polysaccharide solution at a rate of 1 mL / min under light-protected conditions. The mixture was stirred in an ice bath at 0–4 °C for 30 min, and the bulk temperature of the solution was controlled to be ≤5 °C. The mixture was then ultrasonically dispersed at 40 kHz.

4. The method for preparing adaptive dynamic EEG electrodes according to claim 3, characterized in that, In step S2, the metal ion is Al. 3+ Al in the contact layer solution 3+ The concentration of Al in the buffer layer solution is 1 mM. 3+ The concentration of Al in the transport layer solution is 5 mM. 3+ The concentration is 20 mM.

5. The method for preparing adaptive dynamic EEG electrodes according to claim 1, characterized in that, In step S1, the buffer solution is a K2HPO4 solution.

6. The method for preparing adaptive dynamic EEG electrodes according to claim 1, characterized in that, In step S1, the photoinitiator is any one of 2-hydroxy-2-methylphenylpropanone, lithium phenyl-2,4,6-trimethylbenzoylphosphonate, and chlorophyll; The crosslinking agent is N,N'-methylenebisacrylamide and polyethylene glycol diacrylate, or cellulose nanofibers and nanoclay.

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