Bio-based ionic liquid gel as well as preparation method and application thereof

Abstract

The invention discloses bio-based ionic liquid gel as well as a preparation method and application thereof, and relates to the field of flexible bioelectronic sensing and electrophysiological signal monitoring. The gel material consists of bio-based ionic liquid and a flexible polymer network with good biocompatibility, and is prepared by the following steps: firstly, mixing bio-based raw material groups to prepare the bio-based ionic liquid, then introducing a monomer with good biocompatibility, and carrying out photo-initiation polymerization to obtain the ionic liquid gel. The gel material prepared by the invention has excellent biocompatibility and stability brought by an anhydrous system, and is suitable for long-term skin monitoring application. In addition, viscoelasticity is adjusted through a flexible network, so that the gel is in a solid-liquid state and can penetrate through hair and skin to form stable and seamless contact. Therefore, a bioelectronic interface is integrated, the skin contact impedance is greatly reduced, and the electroencephalogram signal monitoring sensitivity is greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of bio-based materials technology, specifically relating to bio-based ionic liquid gels, their preparation methods, and applications. Background Technology

[0002] Electrophysiological signals are a digital display of an organism's state. By decoding these signals, diverse information about behavioral states, physiological health, and even mental activities can be obtained. Among these, brain signals carry the richest information and are of paramount research significance because brain regions are involved in various behavioral activities such as sensory input, information processing, motor control, and emotional regulation. However, the complex monitoring interface of the hairy epidermis in brain regions makes it difficult to accurately capture weak brain signals, thus affecting subsequent signal analysis and further applications. This monitoring difficulty stems from the mismatch between rigid electronic devices and flexible skin, resulting in significant skin contact impedance, ultimately affecting the transmission of electrical signals. Therefore, using flexible gels that are adaptable to the skin as bioelectronic interfaces has become an effective strategy for solving the signal monitoring problem.

[0003] Gel materials possess abundant chemical and physical bonds, allowing for easy modulus adjustment to suit skin requirements. However, while solid gels can mechanically and electrically adhere to skin, they cannot penetrate hair for stable contact with the scalp. Even on hairless skin, their elasticity makes them difficult to adhere to the wavy texture, resulting in significant interfacial impedance. Liquid materials improve interfacial contact by penetrating hair and wavy skin texture. However, their inherent instability means that the reduction in contact impedance is temporary and may introduce crosstalk due to flow. Therefore, a material is needed to achieve sustainable, seamless integration between electronic devices and hairy skin, reducing interfacial impedance to improve the monitoring of electrophysiological signals. Furthermore, the material should possess biocompatibility and anti-drying properties to meet the practical application requirements of long-term skin-attached monitoring. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for preparing bio-based ionic liquid gels, comprising the following steps: 1) Preparation of bio-based ionic liquids: A certain amount of bio-based molten salt was added to a certain amount of acrylic acid, and after stirring, a bio-based ionic liquid was obtained. 2) Preparation of ionic liquid gels: The bio-based ionic liquid obtained in step 1) is mixed with a certain amount of monomer and photoinitiator under light-protected conditions to form a precursor solution, and then the bio-based ionic liquid gel is obtained by photoinitiated polymerization. The monomer is a biocompatible monomer.

[0005] As a preferred embodiment of the above technical solution, the two bio-based raw material powders are mixed, and deionized water is added and stirred at room temperature to obtain a homogeneous solution. The solution is then subjected to rotary evaporation and vacuum drying to obtain the bio-based molten salt.

[0006] As a preferred embodiment of the above technical solution, the two bio-based raw material powders include any one of the following: L-carnitine and malic acid, L-carnitine and tartaric acid, L-carnitine and lysine, L-carnitine and taurine, choline chloride and malic acid, and betaine and taurine; the monomers include any one of polyethylene glycol methyl ether acrylate, polyethylene glycol methyl ether methacrylate, polyethylene glycol, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate.

[0007] As a preferred embodiment of the above technical solution, the molar ratio of L-carnitine to malic acid is 0.3-3:1, the molar ratio of L-carnitine to tartaric acid is 0.3-3:1, the molar ratio of L-carnitine to lysine is 0.3-3:1, the molar ratio of L-carnitine to taurine is 0.3-3:1, the molar ratio of choline chloride to malic acid is 0.3-3:1, and the molar ratio of betaine to taurine is 0.3-3:1; in step 1), the molar ratio of bio-based molten salt to acrylic acid is 1-2:1; and the monomer accounts for 25-50 wt% of the total precursor solution.

[0008] As a preferred embodiment of the above technical solution, the solution in step 1) is subjected to rotary evaporation at 40-50℃ for 2-4 h, and the resulting viscous liquid is subjected to vacuum drying at 35-50℃ for 60-90 h.

[0009] As a preferred embodiment of the above technical solution, the photoinitiator includes 2-hydroxy-2-methyl-1-phenyl-1-propanone, and the photoinitiator accounts for 0.05-0.2 wt% of the total amount of the precursor solution.

[0010] As a preferred embodiment of the above technical solution, the precursor solution is sealed in a glass mold before photoinitiated polymerization.

[0011] As a preferred embodiment of the above technical solution, the precursor solution is irradiated under an ultraviolet light source for 20-40 minutes to initiate a photopolymerization reaction.

[0012] The bio-based ionic liquid gel was prepared by the method described above.

[0013] The application of bio-based ionic liquid gels: During electroencephalogram (EEG) signal monitoring, the bio-based ionic liquid gels are used to connect the skin and the monitoring device to form ionic gel electrodes.

[0014] The beneficial effects of this invention are: (1) This invention regulates the viscoelasticity of the gel through flexible polymer chains, making its morphology intermediate between solid and liquid. This state can maintain seamless contact with skin of different morphologies, and can even penetrate hair to perfectly fit the skin of the brain, solving the problem of mismatch between flexible and complex biological interfaces and rigid electronic interfaces.

[0015] (2) The gel provided by the present invention integrates a bioelectronic interface, which greatly reduces the skin contact impedance (by 1-2 orders of magnitude compared to commercial electrodes), thereby improving the monitoring sensitivity of EEG signals.

[0016] (3) The materials selected in this invention all have good biocompatibility, and combined with the long-term stability brought by the anhydrous system, they are suitable for long-term skin application. Attached Figure Description

[0017] Figure 1 This is a photograph of the iontophoresis gel in Example 1 adhering to the skin, where the scale bar is 10 mm. Figure 2 This is a skin contact impedance diagram of the ion gel electrode in Example 1; Figure 3 This is a comparison chart of the stability of skin contact resistance of the ion gel electrode in Example 1 and the commercial electrode over 72 hours; Figure 4 These are the results of the EEG time-domain spectrum (a top), time-frequency domain thermogram (a bottom), and power spectral density spectrum (b) of the eye-opening and closing tests using ion gel electrodes in Example 1. Figure 5 These are time-frequency domain thermograms at 0 h, 6 h, and 12 h when the ion gel electrode in Example 1 was continuously attached to the scalp to monitor the electroencephalogram (EEG) signals with eyes open and closed. Figure 6 This is a diagram showing the classification results of CNN on eight types of emotional EEG signals. Detailed Implementation

[0018] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Unless otherwise specified, the reagents, methods, instruments, and equipment used in this invention are conventional in the art. Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0020] Example 1 (1) Preparation of bio-based ionic liquids: First, L-carnitine (analytical grade, Sigma-Aldrich Reagents Ltd.) and malic acid (analytical grade, Sigma-Aldrich Reagents Ltd.) were mixed in a 1:1 molar ratio. Then, 150 wt% deionized water was added, and the mixture was stirred at room temperature to obtain a homogeneous solution. The solution was rotary evaporated at 45°C for 3 h to obtain a homogeneous viscous liquid (the pressure was initially reduced from 120 bar to 30 bar in a gradient of 0.5 h, followed by rotary evaporation at 30 bar for 2.5 h). This liquid was then dried in a vacuum oven at 40°C for 72 h to obtain a bio-based molten salt (BMS). Acrylic acid (AA, analytical grade, Sigma-Aldrich Reagents Ltd.) and BMS were mixed in a 1.75:1 molar ratio to induce proton transfer and form salt-bridged hydrogen bonds, resulting in a stable and partially ordered bio-based ionic liquid.

[0021] (2) Preparation of ionic liquid gels: In step (1), a certain mass ratio of polyethylene glycol methyl ether acrylate (OEGA, 40 wt%, analytical grade, Sigma-Aldrich Reagent Co., Ltd.) and 2-hydroxy-2-methyl-1-phenyl-1-propanone (HMPP, 0.1 wt%, Sigma-Aldrich Reagent Co., Ltd.) was added to the bio-based ionic liquid, and the mixture was stirred evenly under light-protected conditions to obtain a precursor solution. Subsequently, the precursor solution was injected into a sealed mold composed of double-layered glass plates, and polymerized under ultraviolet light irradiation (GH03-4, Suzhou Liren Hearing Equipment Co., Ltd.) for 30 min to obtain an ionic liquid gel. The added mass of the above-mentioned polyethylene glycol methyl ether acrylate accounted for 40 wt% of the total mass of the mixed liquid, and the added mass of 2-hydroxy-2-methyl-1-phenyl-1-propanone accounted for 0.1 wt% of the total mass of the mixed liquid.

[0022] Example 2 (1) Preparation of bio-based ionic liquids: First, L-carnitine (analytical grade, Sigma-Aldrich Reagents Ltd.) and tartaric acid (analytical grade, Shanghai Maclean Biotechnology Co., Ltd.) were mixed in a 3:1 molar ratio. Then, 150 wt% deionized water was added, and the mixture was stirred at room temperature to obtain a homogeneous solution. The solution was rotary evaporated at 45°C for 3 h to obtain a homogeneous viscous liquid (the pressure was initially reduced from 120 bar to 30 bar in a gradient of 0.5 h, followed by rotary evaporation at 30 bar for 2.5 h). This liquid was then dried in a vacuum oven at 40°C for 72 h to obtain a bio-based molten salt (BMS). Acrylic acid (AA, analytical grade, Sigma-Aldrich Reagents Ltd.) and BMS were mixed in a 1.75:1 molar ratio to induce proton transfer and form salt-bridged hydrogen bonds, resulting in a stable and partially ordered bio-based ionic liquid.

[0023] (2) Preparation of ionic liquid gels: In step (1), a certain mass ratio of polyethylene glycol methyl ether acrylate (OEGA, 40 wt%, analytical grade, Sigma-Aldrich Reagent Co., Ltd.) and 2-hydroxy-2-methyl-1-phenyl-1-propanone (HMPP, 0.1 wt%, Sigma-Aldrich Reagent Co., Ltd.) was added to the bio-based ionic liquid, and the mixture was stirred evenly under light-protected conditions to obtain a precursor solution. Subsequently, the precursor solution was injected into a sealed mold composed of double-layered glass plates, and polymerized under ultraviolet light irradiation (GH03-4, Suzhou Liren Hearing Equipment Co., Ltd.) for 30 min to obtain an ionic liquid gel.

[0024] Example 3 (1) Preparation of bio-based ionic liquids: First, L-carnitine (analytical grade, Sigma-Aldrich Reagents Ltd.) and lysine (analytical grade, Sigma-Aldrich Reagents Ltd.) were mixed in a 3:1 molar ratio. Then, 150 wt% deionized water was added, and the mixture was stirred at room temperature to obtain a homogeneous solution. The solution was rotary evaporated at 45°C for 3 h to obtain a homogeneous viscous liquid (the pressure was initially reduced from 120 bar to 30 bar in a gradient of 0.5 h, followed by rotary evaporation at 30 bar for 2.5 h). This liquid was then dried in a vacuum oven at 40°C for 72 h to obtain a bio-based molten salt (BMS). Acrylic acid (AA, analytical grade, Sigma-Aldrich Reagents Ltd.) and BMS were mixed in a 1.75:1 molar ratio to induce proton transfer and form salt-bridged hydrogen bonds, resulting in a stable and partially ordered bio-based ionic liquid.

[0025] (2) Preparation of ionic liquid gels: In step (1), a certain mass ratio of polyethylene glycol methyl ether acrylate (OEGA, 40 wt%, analytical grade, Sigma-Aldrich Reagent Co., Ltd.) and 2-hydroxy-2-methyl-1-phenyl-1-propanone (HMPP, 0.1 wt%, Sigma-Aldrich Reagent Co., Ltd.) was added to the bio-based ionic liquid, and the mixture was stirred evenly under light-protected conditions to obtain a precursor solution. Subsequently, the precursor solution was injected into a sealed mold composed of double-layered glass plates, and polymerized under ultraviolet light irradiation (GH03-4, Suzhou Liren Hearing Equipment Co., Ltd.) for 30 min to obtain an ionic liquid gel.

[0026] Example 4 (1) Preparation of bio-based ionic liquids: First, choline chloride (analytical grade, Sigma-Aldrich Reagents Ltd.) and malic acid (analytical grade, Sigma-Aldrich Reagents Ltd.) were mixed in a molar ratio of 0.5:1. Then, 150 wt% deionized water was added, and the mixture was stirred at room temperature to obtain a homogeneous solution. The solution was rotary evaporated at 45°C for 3 h to obtain a homogeneous viscous liquid (the pressure was initially reduced from 120 bar to 30 bar in a gradient of 0.5 h, and then rotary evaporated at 30 bar for another 2.5 h). This liquid was then dried in a vacuum oven at 40°C for 72 h to obtain a bio-based molten salt (BMS). Acrylic acid (AA, analytical grade, Sigma-Aldrich Reagents Ltd.) and BMS were mixed in a molar ratio of 1.75:1 to induce proton transfer and form salt-bridged hydrogen bonds, resulting in a stable and partially ordered bio-based ionic liquid.

[0027] (2) Preparation of ionic liquid gels: In step (1), a certain mass ratio of polyethylene glycol methyl ether acrylate (OEGA, 40 wt%, analytical grade, Sigma-Aldrich Reagent Co., Ltd.) and 2-hydroxy-2-methyl-1-phenyl-1-propanone (HMPP, 0.1 wt%, Sigma-Aldrich Reagent Co., Ltd.) was added to the bio-based ionic liquid, and the mixture was stirred evenly under light-protected conditions to obtain a precursor solution. Subsequently, the precursor solution was injected into a sealed mold composed of double-layered glass plates, and polymerized under ultraviolet light irradiation (GH03-4, Suzhou Liren Hearing Equipment Co., Ltd.) for 30 min to obtain an ionic liquid gel.

[0028] Example 5 (1) Preparation of bio-based ionic liquids: First, betaine (analytical grade, Sigma-Aldrich Reagents Ltd.) and taurine (analytical grade, Sigma-Aldrich Reagents Ltd.) were mixed in a 1:1 molar ratio. Then, 150 wt% deionized water was added, and the mixture was stirred at room temperature to obtain a homogeneous solution. The solution was rotary evaporated at 45°C for 3 h to obtain a homogeneous viscous liquid (the pressure was initially reduced from 120 bar to 30 bar in a gradient of 0.5 h, followed by rotary evaporation at 30 bar for 2.5 h). This liquid was then dried in a vacuum oven at 40°C for 72 h to obtain bio-based molten salt (BMS). Acrylic acid (AA, analytical grade, Sigma-Aldrich Reagents Ltd.) and BMS were mixed in a 1.75:1 molar ratio to induce proton transfer and form salt-bridged hydrogen bonds, resulting in a stable and partially ordered bio-based ionic liquid.

[0029] (2) Preparation of ionic liquid gels: In step (1), a certain mass ratio of polyethylene glycol methyl ether acrylate (OEGA, 40 wt%, analytical grade, Sigma-Aldrich Reagent Co., Ltd.) and 2-hydroxy-2-methyl-1-phenyl-1-propanone (HMPP, 0.1 wt%, Sigma-Aldrich Reagent Co., Ltd.) was added to the bio-based ionic liquid, and the mixture was stirred evenly under light-protected conditions to obtain a precursor solution. Subsequently, the precursor solution was injected into a sealed mold composed of double-layered glass plates, and polymerized under ultraviolet light irradiation (GH03-4, Suzhou Liren Hearing Equipment Co., Ltd.) for 30 min to obtain an ionic liquid gel.

[0030] Example 6 (1) Preparation of bio-based ionic liquids: First, L-carnitine (analytical grade, Sigma-Aldrich Reagents Ltd.) and malic acid (analytical grade, Sigma-Aldrich Reagents Ltd.) were mixed in a 1:1 molar ratio. Then, 150 wt% deionized water was added, and the mixture was stirred at room temperature to obtain a homogeneous solution. The solution was rotary evaporated at 45°C for 3 h to obtain a homogeneous viscous liquid (the pressure was initially reduced from 120 bar to 30 bar in a gradient of 0.5 h, followed by rotary evaporation at 30 bar for 2.5 h). This liquid was then dried in a vacuum oven at 40°C for 72 h to obtain a bio-based molten salt (BMS). Acrylic acid (AA, analytical grade, Sigma-Aldrich Reagents Ltd.) and BMS were mixed in a 1.75:1 molar ratio to induce proton transfer and form salt-bridged hydrogen bonds, resulting in a stable and partially ordered bio-based ionic liquid.

[0031] (2) Preparation of ionic liquid gels: In step (1), a certain mass ratio of polyethylene glycol methyl ether methacrylate (OEGMA, 40 wt%, analytical grade, Sigma-Aldrich Reagent Co., Ltd.) and 2-hydroxy-2-methyl-1-phenyl-1-propanone (HMPP, 0.1 wt%, Sigma-Aldrich Reagent Co., Ltd.) was added to the bio-based ionic liquid, and the mixture was stirred evenly under light-protected conditions to obtain a precursor solution. Subsequently, the precursor solution was injected into a sealed mold composed of double-layered glass plates, and polymerized under ultraviolet light irradiation (GH03-4, Suzhou Liren Hearing Equipment Co., Ltd.) for 30 min to obtain an ionic liquid gel.

[0032] Example 7 (1) Preparation of bio-based ionic liquids: First, L-carnitine (analytical grade, Sigma-Aldrich Reagents Ltd.) and lysine (analytical grade, Sigma-Aldrich Reagents Ltd.) were mixed in a 3:1 molar ratio. Then, 150 wt% deionized water was added, and the mixture was stirred at room temperature to obtain a homogeneous solution. The solution was rotary evaporated at 45°C for 3 h to obtain a homogeneous viscous liquid (the pressure was initially reduced from 120 bar to 30 bar in a gradient of 0.5 h, followed by rotary evaporation at 30 bar for 2.5 h). This liquid was then dried in a vacuum oven at 40°C for 72 h to obtain a bio-based molten salt (BMS). Acrylic acid (AA, analytical grade, Sigma-Aldrich Reagents Ltd.) and BMS were mixed in a 1.75:1 molar ratio to induce proton transfer and form salt-bridged hydrogen bonds, resulting in a stable and partially ordered bio-based ionic liquid.

[0033] (2) Preparation of ionic liquid gels: In step (1), a certain mass ratio of polyethylene glycol methyl ether methacrylate (OEGMA, 40 wt%, analytical grade, Sigma-Aldrich Reagent Co., Ltd.) and 2-hydroxy-2-methyl-1-phenyl-1-propanone (HMPP, 0.1 wt%, Sigma-Aldrich Reagent Co., Ltd.) was added to the bio-based ionic liquid, and the mixture was stirred evenly under light-protected conditions to obtain a precursor solution. Subsequently, the precursor solution was injected into a sealed mold composed of double-layered glass plates, and polymerized under ultraviolet light irradiation (GH03-4, Suzhou Liren Hearing Equipment Co., Ltd.) for 30 min to obtain an ionic liquid gel.

[0034] Example 8 (1) Preparation of bio-based ionic liquids: First, L-carnitine (analytical grade, Sigma-Aldrich Reagents Ltd.) and taurine (analytical grade, Sigma-Aldrich Reagents Ltd.) were mixed in a 1:1 molar ratio. Then, 150 wt% deionized water was added, and the mixture was stirred at room temperature to obtain a homogeneous solution. The solution was rotary evaporated at 45°C for 3 h to obtain a homogeneous viscous liquid (the pressure was initially reduced from 120 bar to 30 bar in a gradient of 0.5 h, followed by rotary evaporation at 30 bar for 2.5 h). This liquid was then dried in a vacuum oven at 40°C for 72 h to obtain a bio-based molten salt (BMS). Acrylic acid (AA, analytical grade, Sigma-Aldrich Reagents Ltd.) and BMS were mixed in a 1:1 molar ratio to induce proton transfer and form salt-bridged hydrogen bonds, resulting in a stable and partially ordered bio-based ionic liquid.

[0035] (2) Preparation of ionic liquid gels: In step (1), a certain mass ratio of polyethylene glycol methyl ether methacrylate (OEGMA, 40 wt%, analytical grade, Sigma-Aldrich Reagent Co., Ltd.) and 2-hydroxy-2-methyl-1-phenyl-1-propanone (HMPP, 0.1 wt%, Sigma-Aldrich Reagent Co., Ltd.) was added to the bio-based ionic liquid, and the mixture was stirred evenly under light-protected conditions to obtain a precursor solution. Subsequently, the precursor solution was injected into a sealed mold composed of double-layered glass plates, and polymerized under ultraviolet light irradiation (GH03-4, Suzhou Liren Hearing Equipment Co., Ltd.) for 30 min to obtain an ionic liquid gel.

[0036] Example 9 (1) Preparation of bio-based ionic liquids: First, L-carnitine (analytical grade, Sigma-Aldrich Reagents Ltd.) and taurine (analytical grade, Sigma-Aldrich Reagents Ltd.) were mixed in a 1:1 molar ratio. Then, 150 wt% deionized water was added, and the mixture was stirred at room temperature to obtain a homogeneous solution. The solution was rotary evaporated at 45°C for 3 h to obtain a homogeneous viscous liquid (the pressure was initially reduced from 120 bar to 30 bar in a gradient of 0.5 h, followed by rotary evaporation at 30 bar for 2.5 h). This liquid was then dried in a vacuum oven at 40°C for 72 h to obtain a bio-based molten salt (BMS). Acrylic acid (AA, analytical grade, Sigma-Aldrich Reagents Ltd.) and BMS were mixed in a 1:1 molar ratio to induce proton transfer and form salt-bridged hydrogen bonds, resulting in a stable and partially ordered bio-based ionic liquid.

[0037] (2) Preparation of ionic liquid gels: In step (1), a certain mass ratio of 2-hydroxyethyl methacrylate (HEMA, 40 wt%, analytical grade, Sigma-Aldrich Reagent Co., Ltd.) and 2-hydroxy-2-methyl-1-phenyl-1-propanone (HMPP, 0.1 wt%, Sigma-Aldrich Reagent Co., Ltd.) was added to the bio-based ionic liquid, and the mixture was stirred evenly under light-protected conditions to obtain a precursor solution. Subsequently, the precursor solution was injected into a sealed mold composed of double-layered glass plates, and polymerized under ultraviolet irradiation (GH03-4, Suzhou Liren Hearing Equipment Co., Ltd.) for 30 min to obtain an ionic liquid gel.

[0038] Example 10 (1) Preparation of bio-based ionic liquids: First, L-carnitine (analytical grade, Sigma-Aldrich Reagents Ltd.) and lysine (analytical grade, Sigma-Aldrich Reagents Ltd.) were mixed in a 3:1 molar ratio. Then, 150 wt% deionized water was added, and the mixture was stirred at room temperature to obtain a homogeneous solution. The solution was rotary evaporated at 45°C for 3 h to obtain a homogeneous viscous liquid (the pressure was initially reduced from 120 bar to 30 bar in a gradient of 0.5 h, followed by rotary evaporation at 30 bar for 2.5 h). This liquid was then dried in a vacuum oven at 40°C for 72 h to obtain a bio-based molten salt (BMS). Acrylic acid (AA, analytical grade, Sigma-Aldrich Reagents Ltd.) and BMS were mixed in a 1.75:1 molar ratio to induce proton transfer and form salt-bridged hydrogen bonds, resulting in a stable and partially ordered bio-based ionic liquid.

[0039] (2) Preparation of ionic liquid gels: In step (1), a certain mass ratio of 2-hydroxypropyl methacrylate (HPMA, 40 wt%, analytical grade, Sigma-Aldrich Reagent Co., Ltd.) and 2-hydroxy-2-methyl-1-phenyl-1-propanone (HMPP, 0.1 wt%, Sigma-Aldrich Reagent Co., Ltd.) was added to the bio-based ionic liquid, and the mixture was stirred evenly under light-protected conditions to obtain a precursor solution. Subsequently, the precursor solution was injected into a sealed mold composed of double-layered glass plates, and polymerized under ultraviolet light irradiation (GH03-4, Suzhou Liren Hearing Equipment Co., Ltd.) for 30 min to obtain an ionic liquid gel.

[0040] Application examples The ionic liquid gel prepared in Example 3 was characterized and its performance was tested. (1) Contact resistance test between ionic liquid gel and skin: After integrating the ionic liquid gel into a standard Ag / AgCl electrode, the electrode was placed on the skin, and the skin contact impedance was measured using a CHI 760E electrochemical workstation.

[0041] (2) Monitoring of EEG signals by ionic liquid gel electrodes According to international electrode placement systems, ionic liquid gel electrodes were placed on the hairy scalp at the back of the head (O2 location, the area responsible for collecting and processing visual information). Two standard electrodes were simultaneously connected to the skin behind the ear as a reference electrode and a ground electrode. All electrodes were connected to an EEG monitoring device (EEG TGAT module, Wuxi Borunyin Co., Ltd.) to record EEG signals. The acquired EEG signals were processed using Python, and power spectrum analysis was performed using short-time Fourier transform.

[0042] Appendix Figure 1This is a photograph of the ionogel prepared in Example 1 adhering to the skin. It can be seen that the materials used in this invention all possess good biocompatibility, and the anhydrous system avoids instability problems caused by drying, making it suitable for long-term skin application. Thanks to the regulation of viscoelasticity by the flexible monomers within the gel, it remains stable in a solid-liquid state, exhibiting excellent skin compliance and adhesion. Therefore, using this gel as an interface to integrate a bioelectronic interface reduces the skin contact impedance to 1.1 kΩ (at 10 Hz), which is 1-2 orders of magnitude lower than commercial electrodes (see attached). Figure 2 and 3 (As shown). Furthermore, this low impedance remains constant during the 72-hour skin-attachment process, solving the problem of impedance surges in commercial electrodes due to water loss from the interface gel.

[0043] It is worth noting that the gel prepared by this invention possesses a solid-liquid interphase characteristic, allowing it to easily penetrate hair and form conformal contact with the scalp in the hair-bearing region. Combined with its stable low contact impedance, it is highly suitable as a brain-computer interface for monitoring electroencephalogram (EEG) signals. After integrating Ag / AgCl standard electrodes, the gel electrode can clearly record the frequency characteristics of EEG signals in both open and closed eye states (as shown in the attached figure). Figure 4 (As shown). The alpha rhythm (8-13 Hz) is prominent when the eyes are closed, which is a characteristic EEG signal when the brain is in a relaxed state with eyes closed. With eyes open, a large amount of visual information is inputted, different cells are assigned to different tasks and move at different frequencies, and the regular alpha rhythm immediately disappears. This prominent alpha rhythm with eyes closed remained clearly visible even after 12 hours of continuous wear, demonstrating the gel electrode's ability to continuously record EEG signals with high fidelity (as shown in the attached image). Figure 5 (As shown). Based on this, the deep learning model of neural convolutional networks (CNN) was used to analyze and classify the electroencephalogram (EEG) signals measured under eight different emotions (labels 0-7 correspond to the emotions of excitement, calmness, tension, fear, sadness, relaxation, happiness, and confusion), achieving an overall classification accuracy of up to 95% (as shown in the attached figure). Figure 6 (As shown).

[0044] It is worth mentioning that the technical features such as the electroencephalogram (EEG) monitoring device involved in this patent application should be regarded as prior art. The specific structure, working principle, and possible control methods and spatial arrangement of these technical features can be adopted using conventional choices in the field, and should not be regarded as the inventive point of this patent. This patent will not be further elaborated in detail.

[0045] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make many modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning or limited experimentation on the basis of the prior art should be within the scope of protection defined by the claims.

Claims

1. A method for preparing a bio-based ionic liquid gel, characterized in that, It includes the following steps: 1) Preparation of bio-based ionic liquids: A certain amount of bio-based molten salt was added to a certain amount of acrylic acid, and after stirring, a bio-based ionic liquid was obtained. 2) Preparation of ionic liquid gels: The bio-based ionic liquid obtained in step 1) is mixed with a certain amount of monomer and photoinitiator under light-protected conditions to form a precursor solution, and then the bio-based ionic liquid gel is obtained by photoinitiated polymerization. The monomer is a biocompatible monomer.

2. The method for preparing the bio-based ionic liquid gel as described in claim 1, characterized in that, Two bio-based raw material powders were mixed, and deionized water was added at room temperature and stirred to obtain a homogeneous solution. The solution was then subjected to rotary evaporation and vacuum drying to obtain the bio-based molten salt.

3. The method for preparing the bio-based ionic liquid gel as described in claim 2, characterized in that, The two bio-based raw material powders include any one of the following: L-carnitine and malic acid, L-carnitine and tartaric acid, L-carnitine and lysine, L-carnitine and taurine, choline chloride and malic acid, and betaine and taurine; the monomers include any one of polyethylene glycol methyl ether acrylate, polyethylene glycol methyl ether methacrylate, polyethylene glycol, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate.

4. The method for preparing the bio-based ionic liquid gel as described in claim 3, characterized in that, The molar ratio of L-carnitine to malic acid is 0.3-3:1, the molar ratio of L-carnitine to tartaric acid is 0.3-3:1, the molar ratio of L-carnitine to lysine is 0.3-3:1, the molar ratio of L-carnitine to taurine is 0.3-3:1, the molar ratio of choline chloride to malic acid is 0.3-3:1, and the molar ratio of betaine to taurine is 0.3-3:1; the molar ratio of bio-based molten salt to acrylic acid in step 1) is 1-2:1; the monomer accounts for 25-50 wt% of the total precursor solution.

5. The method for preparing the bio-based ionic liquid gel as described in claim 4, characterized in that, The solution in step 1) is subjected to rotary evaporation at 40-50℃ for 2-4 h, and the resulting viscous liquid is subjected to vacuum drying at 35-50℃ for 60-90 h.

6. The method for preparing the bio-based ionic liquid gel as described in claim 3, characterized in that, The photoinitiator includes 2-hydroxy-2-methyl-1-phenyl-1-propanone, and the photoinitiator accounts for 0.05-0.2 wt% of the total amount of the precursor solution.

7. The method for preparing the bio-based ionic liquid gel as described in claim 6, characterized in that, The precursor solution is sealed in a glass mold before undergoing photoinitiated polymerization.

8. The method for preparing the bio-based ionic liquid gel as described in claim 7, characterized in that, The precursor solution is irradiated under an ultraviolet light source for 20-40 minutes to initiate a photopolymerization reaction.

9. A bio-based ionic liquid gel, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

10. The application of the bio-based ionic liquid gel as described in claim 9, characterized in that, During EEG signal monitoring, the bio-based ionic liquid gel is used to connect the skin and the monitoring device to form an ionic gel electrode.

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