Graphene oxide modified ionic liquid based electrostatic pressure sensor and preparation method thereof

Abstract

The application discloses a kind of graphene oxide modified ionic liquid's electric field pressure sensor and preparation method, preparation method includes the following steps: (1) synthesis hydroxyl modified cation salt (2) ionic liquid preparation (3) ionic liquid and graphene oxide conjugate connection (4) PU foaming and covalent grafting (5) sensor assembly (6) sensor packaging.The application is modified by introducing graphene oxide (GO) to ionic liquid and makes it covalently grafted in polyurethane (PU) foam skeleton, overcomes the key technical bottleneck that signal drift, response delay and short cycle life etc. caused by ionic liquid leakage, migration and interface instability in traditional electric field pressure sensor.The application realizes the unity of high sensitivity, fast response, wide linear range and excellent durability, provides key technical support for long-term reliable application of electric field sensor in complex environment.

Description

Technical Field

[0001] This invention relates to the field of pressure sensor technology, specifically to an ionized pressure sensor based on graphene oxide-modified ionic liquid and its preparation method. Background Technology

[0002] Traditional flexible capacitive pressure sensors are widely used in tactile sensing, medical monitoring, and human-computer interaction due to their simple structure and stable signal. However, sensors based on the parallel-plate capacitance principle are limited by the incompressibility of the soft dielectric material, hindering sensitivity improvement. To improve performance, researchers have introduced microstructure designs (such as columnar and pyramidal structures) to increase capacitance change by increasing deformation under stress. However, these microstructures are prone to structural hardening under increased pressure, limiting sensitivity improvement. Furthermore, their fabrication often relies on complex photolithography or transfer processes, resulting in high cost and poor durability. In recent years, ionized pressure sensors have utilized the electron double-layer (EDL) effect to form ultra-high capacitance per unit area at the interface between the ion layer and the electrode, demonstrating sensitivity potential far exceeding that of traditional capacitive sensors. However, existing ionized sensors still face key challenges: First, ions in dielectric layers such as ion gels or hydrogels are prone to leakage or migration, leading to insufficient long-term stability of signal baseline drift. Second, dielectric layers are sensitive to fluctuations in environmental humidity, easily losing water or freezing in dry or low-temperature environments, affecting reliability. Third, while microstructure design can improve contact area variation, rapid ion aggregation under an electric field can easily lead to interface ion concentration saturation, limiting further sensitivity improvements. To address these challenges, researchers have attempted to optimize dielectric layers through material modification, such as developing supramolecular biopolymer gels to combine high ionic conductivity and stiffness, or using zwitterionic hydrogels and green solvents (such as acetone glycerol) to enhance environmental stability and self-healing capabilities. However, these methods still struggle to simultaneously achieve ion immobilization and efficient transport in solvent-free environments.

[0003] Graphene oxide (GO), as a two-dimensional nanomaterial, offers novel insights for ionization layer design due to its large specific surface area, abundant surface functional groups (such as carboxyl and hydroxyl groups), and tunable ion transport channels. Its surface functional groups can covalently or non-covalently bind to ionic liquids and polymer matrices to form stable ion transport networks; its nano-confinement effect can optimize ion migration paths and improve ionic conductivity. Furthermore, designing the dielectric layer as a foam structure can significantly increase the effective contact area change under pressure, further broadening the sensor's operating range and linear response. Therefore, there is an urgent need for a novel ionized pressure sensor that, through synergistic innovation in materials and structure, can achieve high sensitivity, a wide pressure range, and excellent environmental adaptability while ensuring ion stability. Summary of the Invention

[0004] The purpose of this invention is to provide a method for fabricating a novel, highly stable, leak-free, highly sensitive, high linear range, and flexible ionized pressure sensor.

[0005] A method for preparing an ionized pressure sensor based on graphene oxide-modified ionic liquid includes the following steps:

[0006] (1) Synthesis of hydroxyl-modified cationic salt: Pyridine and anhydrous acetonitrile were added to the reaction vessel as solvents, and acetonitrile solution of 2-bromoethanol was slowly added dropwise; after the addition was completed, the reaction mixture was heated and stirred at the temperature for a period of time; after the reaction was completed, the mixture was cooled to room temperature; impurities were filtered, the solvent acetonitrile was removed by vacuum drying, the mixture was washed with ethyl acetate solvent, and then vacuum dried to obtain N-2-hydroxyethylpyridine bromide;

[0007] (2) Preparation of ionic liquid: N-2-hydroxyethylpyridine bromide was dissolved in deionized water in a reaction vessel. Under light-proof and room temperature conditions, the aqueous solution of LiTFSI was slowly added while stirring. The stirring was continued for a period of time. After the reaction was completed, the product formed two liquid layers. The organic phase was collected, filtered, and then vacuum dried to obtain the hydroxyl-modified ionic liquid.

[0008] (3) Conjugate connection of ionic liquid and graphene oxide: Add graphene oxide and the ionic liquid prepared in step (2) to the reaction vessel, stir for a period of time in the dark to obtain graphene oxide modified ionic liquid;

[0009] (4) PU foaming and covalent grafting: The graphene oxide modified ionic liquid obtained in step (3) is added to polyether polyol, foaming agent and catalyst in sequence and stirred in a mixing tank for a period of time to form a homogeneous mixture; the premixed liquid and isocyanate are quickly mixed in proportion and mixed by impact using a high-pressure foaming machine. After mixing, the material is quickly injected into the mold; the material is freely foamed and gelled in the mold, and the foam after demolding is subjected to heat treatment; finally, the foam is placed at room temperature for more than 24 hours to make its size and performance completely stable.

[0010] (5) Sensor assembly: The graphene electrode is prepared by screen printing process, and the PU foam ionization layer after cutting is sandwiched between the two electrodes and the electrode leads are connected.

[0011] (6) Sensor encapsulation: The assembled sensor core is encapsulated using upper and lower double-layer PET films. For the upper and lower encapsulation PET films, the active areas of the sensor are pre-cut to ensure that the active areas are unobstructed. On the lower PET encapsulation film, a layer of pressure-sensitive adhesive is evenly coated by screen printing or dispensing. The sensor core is precisely placed on the adhesive area of ​​the lower encapsulation film to ensure that the electrode leads are exposed. The upper PET encapsulation film, which has been pre-cut and coated with pressure-sensitive adhesive, is covered on the surface of the sensor core. A roller or flatbed press is used to perform a light rolling process at room temperature to initially remove interlayer air bubbles and fix each layer initially. A ring of UV adhesive is applied around the active area of ​​the sensor using dispensing equipment to form a sealing ring. The UV adhesive sealing ring is irradiated with ultraviolet light to quickly cure and form a solid shape. Under the set temperature and pressure parameters, the final pressing and curing of the overall structure is completed to ensure that the adhesive reaches the best bonding strength, while further removing residual air bubbles to ensure the sealing performance and structural stability of the encapsulation.

[0012] In step (1), the hydroxyl-modified cationic salt is preferably a cationic salt containing pyridine, and more preferably N-2-hydroxyethylpyridine bromide.

[0013] In step (1), the preferred addition amounts of pyridine are 1 part, 2-bromoethanol is 1-5 parts, and anhydrous acetonitrile is 5-20 parts, and more preferably pyridine is 1 part, 2-bromoethanol is 1.7 parts, and anhydrous acetonitrile is 8 parts.

[0014] In step (1), the heating temperature is preferably 70-100℃, and more preferably 85℃.

[0015] The stirring time in step (1) is preferably 1-48h, more preferably 24h.

[0016] In step (1), the stirring speed is preferably 100-1000 rpm, more preferably 300 rpm.

[0017] In step (2), the preferred addition of N-2-hydroxyethylpyridine bromide is 1 part, the preferred addition of LiTFSI is 0.5-5 parts, and the preferred addition of deionized water is 10-20 parts. More preferably, the addition of N-2-hydroxyethylpyridine bromide is 1 part, the addition of LiTFSI is 1.1 parts, and the addition of deionized water is 10 parts.

[0018] The stirring time in step (2) is preferably 1-48h, more preferably 24h.

[0019] In step (2), the stirring speed is preferably 100-1000 rpm, more preferably 300 rpm.

[0020] In step (3), the preferred amount of graphene oxide added is 1 part, the preferred amount of ionic liquid prepared in step (2) is 0.5-3 parts, and more preferably, the preferred amount of graphene oxide added is 1 part and the preferred amount of ionic liquid prepared in step (2) is 1.5 parts.

[0021] The stirring time in step (3) is preferably 1-48h, more preferably 24h.

[0022] In step (3), the stirring speed is preferably 100-2000 rpm, more preferably 1000 rpm.

[0023] In step (4), the foaming agent is preferably water or a chemical foaming agent, and more preferably water.

[0024] In step (4), the catalyst is preferably an amine or organometallic catalyst, and more preferably dibutyltin dilaurate.

[0025] In step (4), the preferred amount of polyether polyol is 100 parts, the preferred amount of graphene-modified ionic liquid prepared in step (3) is 0.1-5 parts, the preferred amount of foaming agent is 0.1-5 parts, and the preferred amount of catalyst is 0.1-5 parts. More preferably, the preferred amount of polyether polyol is 100 parts, the preferred amount of graphene-modified ionic liquid prepared in step (3) is 2 parts, the preferred amount of foaming agent is 4 parts, and the preferred amount of catalyst is 0.2 parts.

[0026] The pre-stirring time in step (4) is preferably 0.1-2h, more preferably 1h.

[0027] In step (4), the pre-stirring speed is preferably 100-1000 rpm, more preferably 250 rpm.

[0028] In step (4), the pre-stirring temperature is preferably 40-100℃, more preferably 80℃.

[0029] In step (4), the isocyanate is preferably MDI or TDI, and more preferably diphenylmethane diisocyanate.

[0030] In step (4), the preferred amount of premixed liquid added is 100 parts, the preferred amount of isocyanate is 20-100 parts, and the preferred amount of premixed liquid is 100 parts and the preferred amount of isocyanate is 80 parts.

[0031] In step (4), the heat treatment temperature is preferably 50-200℃, more preferably 120℃.

[0032] The heat treatment time in step (4) is preferably 10-300 min, more preferably 60 min.

[0033] In step (5), the electrode is preferably a flexible electrode, and more preferably a graphene electrode.

[0034] In step (5), the thickness of the PU foam ionization layer is preferably 50-500 μm, and more preferably 200 μm.

[0035] In step (6), the active area of ​​the sensor is pre-cut out to the same length and width as the sensor size, and the thickness is half the sensor size. This ensures that the upper and lower cut-out encapsulation materials can fit the sensor well.

[0036] In step (6), the temperature of the pressing and curing process is preferably 50-100℃, and more preferably 80℃.

[0037] In step (6), the pressure during the pressing and curing process is preferably 0.1-2 MPa, more preferably 1 MPa.

[0038] The pressing and curing process in step (6) is preferably 1-10 min, more preferably 5 min.

[0039] A method for preparing an ionized pressure sensor based on graphene oxide-modified ionic liquid, obtained by the above-described preparation method.

[0040] The beneficial effects of this invention are as follows: By introducing graphene oxide (GO) to modify the ionic liquid and covalently grafting it onto the polyurethane (PU) foam framework, this invention overcomes the key technical bottlenecks of traditional ionized pressure sensors, such as signal drift, response hysteresis, and short cycle life caused by ionic liquid leakage, migration, and interface instability. This invention utilizes the two-dimensional layered structure of GO to construct nano-confined ion channels within the PU matrix, significantly improving ion transport efficiency. Through the synergistic effect of chemically bonded stable interfaces, GO nanochannels accelerating ion transport, and foam structure regulating deformation behavior, a unified approach of high sensitivity, rapid response, wide linear range, and excellent durability is achieved, providing key technical support for the long-term reliable application of ionized sensors in complex environments. Detailed Implementation

[0041] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0042] Example 1

[0043] A method for preparing an ionized pressure sensor based on graphene oxide-modified ionic liquid includes the following steps:

[0044] (1) Synthesis of hydroxyl-modified cationic salt: Pyridine and anhydrous acetonitrile were added to the reaction vessel as solvents, and acetonitrile solution of 2-bromoethanol was slowly added dropwise. The amount of pyridine added was 1 part, 2-bromoethanol was 1.7 parts, and anhydrous acetonitrile was 8 parts. After the addition was completed, the reaction mixture was heated to 85°C and stirred at 300 rpm for 24 h at this temperature. After the reaction was completed, the mixture was cooled to room temperature. Impurities were filtered, and the solvent acetonitrile was removed by vacuum drying. The mixture was washed with solvents such as ethyl acetate and then vacuum dried to obtain N-2-hydroxyethylpyridine bromide.

[0045] (2) Preparation of ionic liquid: N-2-hydroxyethylpyridine bromide was dissolved in deionized water in a reaction vessel. Under light-proof and room temperature conditions, an aqueous solution of LiTFSI was slowly added while stirring. The amount of N-2-hydroxyethylpyridine bromide added was 1 part, LiTFSI 1.1 parts, and deionized water 10 parts. The reaction was stirred at 300 rpm for 24 h. After the reaction was completed, the product formed two liquid layers. The organic phase was collected. After filtration, it was vacuum dried to completely remove trace amounts of water and solvent, and hydroxyl-modified ionic liquid was obtained.

[0046] (3) Conjugate connection of ionic liquid and graphene oxide: Add graphene oxide and the ionic liquid prepared in step (2) to the reaction vessel, with 1 part of graphene oxide and 1.5 parts of the ionic liquid prepared in step (2); stir at 1000 rpm for 24 h in the dark to obtain graphene oxide modified ionic liquid.

[0047] (4) PU foaming and covalent grafting: Add polyether polyol, water and dibutyltin dilaurate to the mixture in step (3) in the following order: 100 parts of polyether polyol, 2 parts of graphene-modified ionic liquid prepared in step (3), 4 parts of water and 0.2 parts of dibutyltin dilaurate. Pre-stir and mix at 80℃ and 250rpm for 1h to form a homogeneous mixture; quickly mix the premix with diphenylmethane diisocyanate in proportion: 100 parts of premix and 80 parts of diphenylmethane diisocyanate; use a high-pressure foaming machine to impact and mix, and quickly inject the mixture into the mold; the material foams freely in the mold and gels and sets, and the foam after demolding is heat-treated at 120℃ for 60min; finally, the foam needs to be placed at room temperature for more than 24 hours to make its size and performance completely stable.

[0048] (5) Sensor assembly: The graphene electrode is formed by screen printing; the cut 200um thick PU foam ionization layer is sandwiched between the two electrodes, the electrode leads are connected, and then it is encapsulated.

[0049] (6) Sensor encapsulation: The assembled sensor core is encapsulated using upper and lower double-layer PET films. For the upper and lower encapsulation PET films, pre-cut holes are made corresponding to the active area of ​​the sensor, with the length and width matching the sensor size and the thickness being half the sensor size, ensuring that the upper and lower cut-out encapsulation materials can fit the sensor well. A layer of pressure-sensitive adhesive is evenly coated onto the lower PET encapsulation film using screen printing or dispensing. The sensor core is precisely placed in the adhesive-coated area of ​​the lower encapsulation film, ensuring that the electrode leads are exposed. The pre-cut and coated pressure-sensitive adhesive is then applied to the sensor core. The upper PET encapsulation film of the adhesive is applied to the surface of the sensor core. A light rolling process is performed at room temperature using a roller or flatbed press to initially remove interlayer air bubbles and preliminarily fix each layer. A ring of UV adhesive is applied around the active area of ​​the sensor using a dispensing device to form a sealing ring. The UV adhesive sealing ring is then irradiated with ultraviolet light to rapidly cure and solidify. Finally, the entire structure is pressed and cured at 80℃ and 1MPa for 5 minutes to ensure optimal adhesive strength and further remove residual air bubbles, guaranteeing sealing and structural stability.

[0050] Example 2

[0051] A method for preparing an ionized pressure sensor based on graphene oxide-modified ionic liquid includes the following steps:

[0052] (1) Synthesis of hydroxyl-modified cationic salt: Pyridine and anhydrous acetonitrile were added to the reaction vessel as solvents, and acetonitrile solution of 2-bromoethanol was slowly added dropwise. The amount of pyridine added was 1 part, 2-bromoethanol was 1 part, and anhydrous acetonitrile was 5 parts. After the addition was completed, the reaction mixture was heated to 70°C and stirred at 100 rpm for 1 h at this temperature. After the reaction was completed, the mixture was cooled to room temperature. Impurities were filtered, and the solvent acetonitrile was removed by vacuum drying. The mixture was washed with solvents such as ethyl acetate and then vacuum dried to obtain N-2-hydroxyethylpyridine bromide.

[0053] (2) Preparation of ionic liquid: N-2-hydroxyethylpyridine bromide was dissolved in deionized water in a reaction vessel. Under light-proof and room temperature conditions, an aqueous solution of LiTFSI was slowly added while stirring. The amount of N-2-hydroxyethylpyridine bromide added was 1 part, LiTFSI 0.5 parts, and deionized water 10 parts. The reaction was stirred at 100 rpm for 1 h. After the reaction was completed, the product formed two liquid layers. The organic phase was collected. After filtration, it was vacuum dried to completely remove trace amounts of water and solvent, and hydroxyl-modified ionic liquid was obtained.

[0054] (3) Conjugate connection of ionic liquid and graphene oxide: Add graphene oxide and the ionic liquid prepared in step (2) to the reaction vessel. The amount of graphene oxide added is 1 part and the amount of ionic liquid prepared in step (2) is 3 parts. Stir at 100 rpm for 1 h in the dark to obtain graphene oxide modified ionic liquid.

[0055] (4) PU foaming and covalent grafting: Add the mixture from step (3) to polyether polyol, water, and dibutyltin dilaurate in sequence to the mixing tank; 100 parts of polyether polyol, 0.1 parts of graphene-modified ionic liquid prepared in step (3), 4 parts of water, and 0.2 parts of dibutyltin dilaurate are pre-mixed at 40°C and 100 rpm for 0.1 h to form a homogeneous mixture; the premix is ​​rapidly mixed with diphenylmethane diisocyanate in proportion, and 100 parts of premix and 20 parts of diphenylmethane diisocyanate are mixed by impact using a high-pressure foaming machine; after mixing, the material is quickly injected into the mold; the material is freely foamed and gelled in the mold, and the foam after demolding is heat-treated at 50°C for 10 min. Finally, the foam needs to be placed at room temperature for more than 24 hours to ensure that its size and performance are completely stable.

[0056] (5) Sensor assembly: The graphene electrode is formed by screen printing; the cut 50um thick PU foam ionization layer is sandwiched between the two electrodes, the electrode leads are connected, and then it is encapsulated.

[0057] (6) Sensor encapsulation: The assembled sensor core is encapsulated using a double-layer PET film. For the upper and lower encapsulation PET films, pre-cut perforations are made corresponding to the active area of ​​the sensor, with length and width matching the sensor dimensions and a thickness half that of the sensor, ensuring good adhesion between the two perforated encapsulation materials. A layer of pressure-sensitive adhesive is evenly coated onto the lower encapsulation PET film using screen printing or dispensing. The sensor core is precisely placed in the adhesive-coated area of ​​the lower encapsulation film, ensuring the electrode leads are exposed. The upper encapsulation PET film, also with perforations and adhesive coating, is then placed over the core. Light rolling is performed at room temperature using a roller or flatbed press to initially remove interlayer air bubbles and preliminarily fix each layer. A ring of UV adhesive is applied around the active area of ​​the sensor using precision dispensing equipment to form a sealing ring. Ultraviolet light is used for rapid curing; the final pressing and curing of the overall structure is completed at 80℃ and 1MPa for 5 minutes, ensuring the adhesive reaches optimal bonding strength and further removing residual air bubbles to guarantee encapsulation sealing and structural stability.

[0058] Example 3

[0059] A method for preparing an ionized pressure sensor based on graphene oxide-modified ionic liquid includes the following steps:

[0060] (1) Synthesis of hydroxyl-modified cationic salt: Pyridine and anhydrous acetonitrile were added to the reaction vessel as solvents, and acetonitrile solution of 2-bromoethanol was slowly added dropwise. The amount of pyridine added was 1 part, 2-bromoethanol was 5 parts, and anhydrous acetonitrile was 20 parts. After the addition was completed, the reaction mixture was heated to 100°C and stirred at 1000 rpm for 48 h at this temperature. After the reaction was completed, the mixture was cooled to room temperature, impurities were filtered, and the solvent acetonitrile was removed by vacuum drying. The mixture was washed with solvents such as ethyl acetate and then vacuum dried to obtain N-2-hydroxyethylpyridine bromide.

[0061] (2) Preparation of ionic liquid: N-2-hydroxyethylpyridine bromide was dissolved in deionized water in a reaction vessel. Under light-proof and room temperature conditions, an aqueous solution of LiTFSI was slowly added while stirring. The amount of N-2-hydroxyethylpyridine bromide added was 1 part, LiTFSI 5 parts, and deionized water 20 parts. The reaction was stirred at 1000 rpm for 48 h. After the reaction was completed, the product formed two liquid layers. The organic phase was collected. After filtration, it was vacuum dried to completely remove trace amounts of water and solvent, and hydroxyl-modified ionic liquid was obtained.

[0062] (3) Conjugate connection of ionic liquid and graphene oxide: Add graphene oxide and the ionic liquid prepared in step (2) to the reaction vessel, with 1 part of graphene oxide and 0.5 parts of the ionic liquid prepared in step (2); stir at 2000 rpm for 48 h in the dark to obtain graphene oxide modified ionic liquid.

[0063] (4) PU foaming and covalent grafting: Add polyether polyol, water and dibutyltin dilaurate to the mixture in step (3) in the following order: 100 parts of polyether polyol, 5 parts of graphene modified ionic liquid prepared in step (3), 4 parts of water and 0.2 parts of dibutyltin dilaurate; pre-stir at 100℃ and 1000rpm for 2h to form a homogeneous mixture; quickly mix the premix with diphenylmethane diisocyanate in proportion: 100 parts of premix and 100 parts of diphenylmethane diisocyanate; use a high-pressure foaming machine to impact and mix, and quickly inject the mixture into the mold; the material foams freely in the mold and gels and shapes, and the foam after demolding is heat-treated at 200℃ for 300min; finally, the foam needs to be placed at room temperature for more than 24 hours to make its size and performance completely stable.

[0064] (5) Sensor assembly: The graphene electrode is formed by screen printing. The 500um thick PU foam ionization layer is cut and sandwiched between the two electrodes. The electrode leads are connected and then encapsulated.

[0065] (6) Sensor encapsulation: The assembled sensor core is encapsulated using upper and lower double-layer PET films. For the upper and lower encapsulation PET films, the active area of ​​the sensor is pre-cut with the same length and width as the sensor size and the thickness is half the sensor size to ensure that the upper and lower cut-out encapsulation materials can fit the sensor well. In the designated area of ​​the lower PET encapsulation film, a layer of pressure-sensitive adhesive is evenly coated by screen printing or dispensing. The sensor core is precisely placed in the adhesive coating area of ​​the lower encapsulation film, strictly ensuring that the electrode leads are exposed and avoiding obstruction. The pre-cut and coated PET film is then placed in the adhesive coating area of ​​the lower encapsulation film. The pressure-sensitive adhesive is topped with a PET encapsulation film, which covers the surface of the sensor core. A light rolling process is performed at room temperature using a roller or flatbed press to initially remove interlayer air bubbles and pre-fix each layer. A ring of UV adhesive is then applied around the active area of ​​the sensor using precision dispensing equipment, forming a closed-loop seal. The UV adhesive sealing ring is then irradiated with ultraviolet light to rapidly cure. Finally, the entire structure is pressed and cured at 80°C and 1MPa for 5 minutes to ensure optimal adhesive strength and further remove residual air bubbles, guaranteeing sealing and structural stability.

[0066] Example 4

[0067] A method for preparing a leak-free ionized pressure sensor based on a hydroxyl-modified ionic liquid includes the following steps:

[0068] (1) To synthesize the hydroxyl-modified cationic salt, pyridine and anhydrous acetonitrile were added as solvents to a reaction vessel. A solution of 2-bromoethanol in acetonitrile was slowly added dropwise. The amounts of pyridine added were 1 part, 2-bromoethanol 1.7 parts, and anhydrous acetonitrile 8 parts. After the addition was complete, the reaction mixture was heated to 85°C and stirred at 300 rpm for 24 h at this temperature. After the reaction was completed, the mixture was cooled to room temperature. Impurities were filtered out, and the solvent acetonitrile was removed by vacuum drying. The mixture was washed with solvents such as ethyl acetate and then vacuum dried to obtain N-2-hydroxyethylpyridine bromide.

[0069] (2) Preparation of ionic liquid: N-2-hydroxyethylpyridine bromide was dissolved in deionized water in a reaction vessel. Under light-protected and room temperature conditions, an aqueous solution of LiTFSI was slowly added with stirring. The addition amounts were 1 part N-2-hydroxyethylpyridine bromide, 1.1 parts LiTFSI, and 10 parts deionized water. The reaction was stirred at 300 rpm for 24 h. After the reaction was completed, the product formed two liquid layers, and the organic phase was collected. After filtration, the product was vacuum dried to completely remove trace amounts of water and solvent, yielding the hydroxyl-modified ionic liquid.

[0070] (3) PU foaming and covalent grafting: Add polyether polyol, hydroxyl-modified ionic liquid prepared in step (2), water and dibutyltin dilaurate to the mixing tank in sequence. The proportion of each material (parts by mass) is: 100 parts of polyether polyol, 2 parts of hydroxyl-modified ionic liquid, 4 parts of water and 0.2 parts of dibutyltin dilaurate. Control the temperature in the mixing tank to 80℃ and the stirring speed to 250rpm. Continue to pre-stir and mix for 1h until a homogeneous premix is ​​formed. According to the mass ratio of 100 parts of premix and 80 parts of diphenylmethane diisocyanate, put the two into a high-pressure foaming machine and mix them by impact. After mixing, quickly inject the material into the preset mold. The material undergoes free foaming reaction in the mold and completes gel shaping at the same time. Place the demolded foam in a 120℃ environment for heat treatment for 60min. After heat treatment, place the foam at room temperature for more than 24h to ensure that its shape and various performance indicators are completely stable.

[0071] (4) Sensor assembly: The graphene electrodes are formed by screen printing. The cut 200um thick PU foam ionization layer is sandwiched between the two electrodes, the electrode leads are connected, and then it is encapsulated.

[0072] (5) Sensor encapsulation: The assembled sensor core is encapsulated using upper and lower double-layer PET films. For the upper and lower encapsulation PET films, the active area of ​​the sensor is pre-cut, with the length and width consistent with the sensor size and the thickness being half the sensor size, to ensure that the upper and lower cut-out encapsulation materials can fit the sensor well. In the designated area of ​​the lower PET encapsulation film, a layer of pressure-sensitive adhesive is evenly coated by screen printing or dispensing. The sensor core is precisely placed in the adhesive coating area of ​​the lower encapsulation film, strictly ensuring that the electrode leads are exposed and avoiding obstruction. The pre-cut-out and coated... The pressure-sensitive adhesive is topped with a PET encapsulation film, which covers the surface of the sensor core. A light rolling process is performed at room temperature using a roller or flatbed press to initially remove interlayer air bubbles and pre-fix each layer. A ring of UV adhesive is then applied around the active area of ​​the sensor using precision dispensing equipment, forming a closed-loop seal. The UV adhesive sealing ring is then irradiated with ultraviolet light to rapidly cure. Finally, the entire structure is pressed and cured at 80°C and 1MPa for 5 minutes to ensure optimal adhesive strength and further remove residual air bubbles, guaranteeing sealing and structural stability.

[0073] Example 5

[0074] A method for preparing an ionized pressure sensor based on graphene oxide-modified ionic liquid includes the following steps:

[0075] (1) Synthesis of hydroxyl-modified cationic salt: Pyridine and anhydrous acetonitrile were added to the reaction vessel as solvents, and acetonitrile solution of 2-bromoethanol was slowly added dropwise. The amount of pyridine added was 1 part, 2-bromoethanol was 5 parts, and anhydrous acetonitrile was 5 parts. After the addition was completed, the reaction mixture was heated to 100°C and stirred at 500 rpm for 36 h at this temperature. After the reaction was completed, the mixture was cooled to room temperature. Impurities were filtered, and the solvent acetonitrile was removed by vacuum drying. The mixture was washed with solvents such as ethyl acetate and then vacuum dried to obtain N-2-hydroxyethylpyridine bromide.

[0076] (2) Preparation of ionic liquid: N-2-hydroxyethylpyridine bromide was dissolved in deionized water in a reaction vessel. Under light-proof and room temperature conditions, an aqueous solution of LiTFSI was slowly added while stirring. The amount of N-2-hydroxyethylpyridine bromide added was 1 part, LiTFSI 5 parts, and deionized water 15 parts. The reaction was stirred at 600 rpm for 12 h. After the reaction was completed, the product formed two liquid layers. The organic phase was collected. After filtration, it was vacuum dried to completely remove trace amounts of water and solvent, and hydroxyl-modified ionic liquid was obtained.

[0077] (3) Conjugate connection of ionic liquid and graphene oxide: Add graphene oxide and the ionic liquid prepared in step (2) to the reaction vessel. The amount of graphene oxide added is 1 part and the amount of ionic liquid prepared in step (2) is 3 parts. Stir at 1500 rpm for 5 hours in the dark to obtain graphene oxide modified ionic liquid.

[0078] (4) PU foaming and covalent grafting: Add polyether polyol, water and dibutyltin dilaurate to the mixture in step (3) in the following order: 100 parts of polyether polyol, 0.1 parts of graphene-modified ionic liquid prepared in step (3), 2 parts of water and 2 parts of dibutyltin dilaurate. Pre-stir and mix at 100℃ and 500rpm for 2h to form a homogeneous mixture; quickly mix the premix with diphenylmethane diisocyanate in proportion: 100 parts of premix and 20 parts of diphenylmethane diisocyanate; use a high-pressure foaming machine to impact and mix, and quickly inject the mixture into the mold; the material foams freely in the mold and gels and sets, and the foam after demolding is heat-treated at 200℃ for 150min; finally, the foam needs to be placed at room temperature for more than 24 hours to make its size and performance completely stable.

[0079] (5) Sensor assembly: The graphene electrode is formed by screen printing; the cut 500um thick PU foam ionization layer is sandwiched between the two electrodes, the electrode leads are connected, and then it is encapsulated.

[0080] (6) Sensor encapsulation: The assembled sensor core is encapsulated using upper and lower double-layer PET films. For the upper and lower encapsulation PET films, pre-cut holes are made corresponding to the active area of ​​the sensor, with length and width matching the sensor size and thickness half the sensor size, ensuring good adhesion between the upper and lower cut-out encapsulation materials. A layer of pressure-sensitive adhesive is evenly coated onto the lower PET encapsulation film using screen printing or dispensing. The sensor core is precisely placed in the adhesive-coated area of ​​the lower encapsulation film, ensuring the electrode leads are exposed. The pre-cut and pressure-sensitive adhesive-coated... The upper PET encapsulation film is applied to the surface of the sensor core. A light rolling process is performed at room temperature using a roller or flatbed press to initially remove interlayer air bubbles and preliminarily fix each layer. A ring of UV adhesive is applied around the active area of ​​the sensor using a dispensing device to form a sealing ring. The UV adhesive sealing ring is then irradiated with ultraviolet light to rapidly cure and solidify. Finally, the entire structure is pressed and cured at 100℃ and 0.1 MPa for 10 minutes to ensure optimal adhesive strength and further remove residual air bubbles, guaranteeing sealing and structural stability.

[0081] Example 6

[0082] A method for preparing an ionized pressure sensor based on graphene oxide-modified ionic liquid includes the following steps:

[0083] (1) Synthesis of hydroxyl-modified cationic salt: Pyridine and anhydrous acetonitrile were added to the reaction vessel as solvents, and acetonitrile solution of 2-bromoethanol was slowly added dropwise. The amount of pyridine added was 1 part, 2-bromoethanol was 1 part, and anhydrous acetonitrile was 5 parts. After the addition was completed, the reaction mixture was heated to 75°C and stirred at 100 rpm for 14 h at this temperature. After the reaction was completed, the mixture was cooled to room temperature. Impurities were filtered, and the solvent acetonitrile was removed by vacuum drying. The mixture was washed with solvents such as ethyl acetate and then vacuum dried to obtain N-2-hydroxyethylpyridine bromide.

[0084] (2) Preparation of ionic liquid: N-2-hydroxyethylpyridine bromide was dissolved in deionized water in a reaction vessel. Under light-proof and room temperature conditions, an aqueous solution of LiTFSI was slowly added while stirring. The amount of N-2-hydroxyethylpyridine bromide added was 1 part, LiTFSI 5 parts, and deionized water 20 parts. The reaction was stirred at 590 rpm for 48 h. After the reaction was completed, the product formed two liquid layers. The organic phase was collected. After filtration, it was vacuum dried to completely remove trace amounts of water and solvent, and hydroxyl-modified ionic liquid was obtained.

[0085] (3) Conjugate connection of ionic liquid and graphene oxide: Add graphene oxide and the ionic liquid prepared in step (2) to the reaction vessel, with 1 part of graphene oxide and 0.5 parts of the ionic liquid prepared in step (2); stir at 1500 rpm for 1 h in the dark to obtain graphene oxide modified ionic liquid.

[0086] (4) PU foaming and covalent grafting: Add polyether polyol, water and dibutyltin dilaurate to the mixture in step (3) in the following order: 100 parts of polyether polyol, 0.1 parts of graphene-modified ionic liquid prepared in step (3), 5 parts of water and 5 parts of dibutyltin dilaurate. Pre-stir and mix at 40°C and 1000 rpm for 2 hours to form a homogeneous mixture; quickly mix the premix with diphenylmethane diisocyanate in proportion: 100 parts of premix and 100 parts of diphenylmethane diisocyanate; use a high-pressure foaming machine to impact and mix, and quickly inject the mixture into the mold; the material foams freely in the mold and gels and sets, and the foam after demolding is heat-treated at 200°C for 10 minutes; finally, the foam needs to be placed at room temperature for more than 24 hours to make its size and performance completely stable.

[0087] (5) Sensor assembly: The graphene electrode is formed by screen printing; the cut 50um thick PU foam ionization layer is sandwiched between the two electrodes, the electrode leads are connected, and then it is encapsulated.

[0088] (6) Sensor encapsulation: The assembled sensor core is encapsulated using upper and lower double-layer PET films. For the upper and lower encapsulation PET films, pre-cut holes are made corresponding to the active area of ​​the sensor, with the length and width matching the sensor size and the thickness being half the sensor size, ensuring that the upper and lower cut-out encapsulation materials can fit the sensor well. A layer of pressure-sensitive adhesive is evenly coated onto the lower PET encapsulation film using screen printing or dispensing. The sensor core is precisely placed in the adhesive-coated area of ​​the lower encapsulation film, ensuring that the electrode leads are exposed. The pre-cut and coated pressure-sensitive adhesive is then applied to the sensor core. The upper PET encapsulation film of the adhesive is applied to the surface of the sensor core. A light rolling process is performed at room temperature using a roller or flatbed press to initially remove interlayer air bubbles and preliminarily fix each layer. A ring of UV adhesive is applied around the active area of ​​the sensor using a dispensing device to form a sealing ring. The UV adhesive sealing ring is then irradiated with ultraviolet light to rapidly cure and solidify. Finally, the entire structure is pressed and cured at 50°C and 2 MPa for 10 minutes to ensure optimal adhesive strength and further remove residual air bubbles, guaranteeing sealing and structural stability.

[0089] Comparative Example 1

[0090] A method for fabricating a leak-free ionized pressure sensor based on ionized liquids includes the following steps:

[0091] (1) PU foaming and covalent grafting: Polyether polyol, 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid, water, and dibutyltin dilaurate were added to the mixing tank in sequence. The proportions (parts by mass) of each material were: 100 parts polyether polyol, 2 parts ionic liquid, 4 parts water, and 0.2 parts dibutyltin dilaurate. The mixture was pre-stirred at 80℃ and 250rpm for 1 hour to form a homogeneous mixture. The premix was then rapidly mixed with diphenylmethane diisocyanate in a specific ratio. The ratio was 100 parts premix and 80 parts diphenylmethane diisocyanate. The mixture was then impact-mixed using a high-pressure foaming machine. After mixing, the material was quickly injected into the mold. The material was allowed to foam freely and gel in the mold. The demolded foam was then heat-treated at 120℃ for 60 minutes. Finally, the foam was allowed to stand at room temperature for more than 24 hours to allow its dimensions and properties to stabilize completely.

[0092] (2) Sensor assembly: The graphene electrode is formed by screen printing. The 200um thick PU foam ionization layer is cut and sandwiched between the two electrodes. The electrode leads are connected and then encapsulated.

[0093] (3) Sensor encapsulation: The assembled sensor core is encapsulated using upper and lower double-layer PET films. For the upper and lower encapsulation PET films, pre-cut holes are made corresponding to the active area of ​​the sensor, with length and width matching the sensor size and thickness half the sensor size, ensuring good adhesion between the upper and lower cut-out encapsulation materials. A layer of pressure-sensitive adhesive is evenly coated in a designated area of ​​the lower PET encapsulation film using screen printing or dispensing. The sensor core is precisely placed in the adhesive-coated area of ​​the lower encapsulation film, strictly ensuring that the electrode leads are exposed and avoiding obstruction. The pre-cut and coated... The pressure-sensitive adhesive is topped with a PET encapsulation film, which covers the surface of the sensor core. A light rolling process is performed at room temperature using a roller or flatbed press to initially remove interlayer air bubbles and pre-fix each layer. A ring of UV adhesive is then applied around the active area of ​​the sensor using precision dispensing equipment, forming a closed-loop seal. The UV adhesive sealing ring is then irradiated with ultraviolet light to rapidly cure. Finally, the entire structure is pressed and cured at 80°C and 1MPa for 5 minutes to ensure optimal adhesive strength and further remove residual air bubbles, guaranteeing sealing and structural stability.

[0094] Comparative Example 2

[0095] A method for fabricating an ion-liquid-wetted ion-type pressure sensor includes the following steps:

[0096] (1) The formed PU foam was immersed in the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate for 10 minutes at room temperature until the foam was completely saturated with the ionic liquid. Then, the foam was squeezed with tweezers to remove most of the free ionic liquid in the pores, and then placed on lint-free paper to absorb the excess liquid. The mass ratio of PU to ionic liquid was adjusted by weighing, and the mass ratio of ionic liquid to polyurethane was approximately 3:1.

[0097] (2) Sensor assembly: The graphene electrode is formed by screen printing. The 200um thick PU foam ionization layer is cut and sandwiched between the two electrodes. The electrode leads are connected and then encapsulated.

[0098] (3) Sensor encapsulation: The assembled sensor core is encapsulated using upper and lower double-layer PET films. For the upper and lower encapsulation PET films, pre-cut holes are made corresponding to the active area of ​​the sensor, with length and width matching the sensor size and thickness half the sensor size, ensuring good adhesion between the upper and lower cut-out encapsulation materials. A layer of pressure-sensitive adhesive is evenly coated in a designated area of ​​the lower PET encapsulation film using screen printing or dispensing. The sensor core is precisely placed in the adhesive-coated area of ​​the lower encapsulation film, strictly ensuring that the electrode leads are exposed and avoiding obstruction. The pre-cut and coated... The pressure-sensitive adhesive is topped with a PET encapsulation film, which covers the surface of the sensor core. A light rolling process is performed at room temperature using a roller or flatbed press to initially remove interlayer air bubbles and pre-fix each layer. A ring of UV adhesive is then applied around the active area of ​​the sensor using precision dispensing equipment, forming a closed-loop seal. The UV adhesive sealing ring is then irradiated with ultraviolet light to rapidly cure. Finally, the entire structure is pressed and cured at 80°C and 1MPa for 5 minutes to ensure optimal adhesive strength and further remove residual air bubbles, guaranteeing sealing and structural stability.

[0099] This invention utilizes the two-dimensional layered structure of GO to construct nano-confined ion channels within a PU matrix, significantly improving ion transport efficiency. N-2-hydroxyethylpyridine cations are covalently fixed to the PU backbone, making them positively charged, while the carboxyl groups and other functional groups abundant on the GO sheet surface are typically negatively charged in aqueous or polar environments. This creates a unique local electrostatic field near the GO sheets. This field strongly attracts and enriches negatively charged TFSI⁻ ions, significantly increasing their concentration at the channel inlet and providing a powerful driving force for transport. In solvent-free, covalently cross-linked PU foam, ion migration primarily occurs within the polymer bulk. The migration path within the polymer is a three-dimensional network composed of countless continuously occurring free volume vacancies, permeating the entire material. Due to the instantaneous free volume generated by the movement of chain segments, ion migration faces high resistance, resulting in generally low conductivity. Furthermore, ion hopping is a relatively slow process, leading to long response and recovery times for the sensor. Two-dimensional GO sheets construct nano-confined channels within the PU matrix, providing ions with a far superior and more continuous high-speed channel than free volume. Because GO is discontinuously distributed within the PU matrix, ion transport is an alternating process of "rapid gliding on GO sheets" and "short-range hopping within the PU matrix between sheets." As long as the amount of GO added reaches the threshold for forming an effective conductive pathway (percolation threshold), a rapidly energized ion transport chain can be formed throughout the composite material, significantly improving both ion conductivity and response time. Data from Examples 1 and 3 show sensitivities of 105.15 kPa⁻¹ and 78.69 kPa⁻¹, respectively, with response times as fast as 6.5 ms and 8.2 ms, and a wide linear range of 50 Pa–1.2 MPa. Furthermore, the solvent-free three-dimensional network formed by the covalent bonding of hydroxyethyl groups and PU isocyanate in the ionic liquid fundamentally suppresses ion leakage, resulting in a sensitivity retention rate of 99.5% after 10,000 cycles, far superior to the physically mixed types in Examples 1 and 2. In addition, GO, acting as a heterogeneous nucleation site, optimizes the PU foaming process, forming a uniform and dense cell structure. This not only increases the effective contact area and improves sensitivity but also enhances foam resilience by suppressing polymer chain slippage, enabling the sensor to maintain high linearity (R² ≥ 0.999) over a wide pressure range. In summary, this design achieves a balance of high sensitivity, rapid response, wide linear range, and excellent durability through the synergistic effect of chemically bonded stable interfaces, GO nanochannels accelerating ion transport, and foam structure regulating deformation behavior. This provides key technical support for the long-term reliable application of ionized sensors in complex environments.

[0100] Experimental Example

[0101] This invention relates to an ionized pressure sensor based on graphene oxide-modified ionic liquid, measuring its sensitivity, linearity, response time, and dynamic fatigue performance.

[0102] The sensitivity testing method involves fixing the sensor on a test platform, ensuring the pressure application surface is aligned with the pressure source, connecting a capacitance meter (LCR meter, set to 1kHz frequency and 0.5V), and recording the initial capacitance value C0. Using a pressure controller, an incremental static pressure is applied starting from 0, in a stepped manner. At each pressure point Pi, the pressure is held stable for 30 seconds until the capacitance value stabilizes, and the corresponding capacitance value Ci is recorded. This process is repeated until the maximum pressure point is reached. The relative capacitance change rate at each pressure point is calculated: ΔC / C0 = (Ci - C0) / C0. A curve is plotted with pressure P on the x-axis and ΔC / C0 on the y-axis. The sensitivity S is taken as the slope of this curve in the linear region.

[0103] The linearity detection method directly utilizes the pressure-capacitance change rate dataset obtained from sensitivity measurements. The least squares method is used to perform linear fitting on the data, yielding the fitted line equation, and R² is calculated based on the fitted equation.

[0104] The linear range is the pressure range corresponding to all data points where the deviation from the fitted straight line does not exceed ±1% or ±0.5% of the full-scale output.

[0105] The response time detection method uses a fast solenoid valve or an impact pressure generator to apply a step pressure within <1ms. A high-speed data acquisition system records the capacitance signal in real time. In the initial state of the sensor, a step pressure input is triggered. The capacitance change over time curve C(t) is recorded. The final stable value Cfinal of the capacitance change is determined. The 10% and 90% response points are calculated: C10 = C0 + 0.1 × (Cfinal − C0), C90 = C0 + 0.9 × (Cfinal − C0). The response time is the time required for the capacitance signal to rise from C10 to C90.

[0106] The dynamic fatigue testing method involves using a cyclic pressure device (frequency 1Hz, pressure range 0-60% of the range) to continuously load and unload the sensor. After a certain number of cycles (e.g., 10,000 cycles), the sensitivity decay rate is calculated as (sensitivity after cycles / initial sensitivity × 100%).

[0107] The test results are shown in Table 1.

[0108] Performance indicators Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Sensitivity (kPa⁻¹) 105.15 21.47 78.69 29.71 5.56 2.48 Response time (ms) 6.5 75.0 8.2 18.5 150.4 28.5 Linearity (R²) 0.999 0.985 0.998 0.996 0.950 0.720 Linear range 50Pa-1.2MPa 1kPa-500kPa 0.1kPa-800kPa 0.5kPa-750kPa 10kPa-200kPa 2kPa-600kPa Dynamic fatigue testing (sensitivity retention rate after 10,000 cycles) ≥99.5% ≥90% ≥98% ≥95% ≤70% ≤50%

[0109] Table 1 Performance Table of Ionized Flexible Pressure Sensor

[0110] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for preparing an ionized pressure sensor based on graphene oxide-modified ionic liquid, comprising the following steps: (1) Synthesis of hydroxyl-modified cationic salt: Pyridine and anhydrous acetonitrile were added to the reaction vessel as solvents, and acetonitrile solution of 2-bromoethanol was slowly added dropwise; after the addition was completed, the reaction mixture was heated and stirred at the temperature for a period of time; after the reaction was completed, the mixture was cooled to room temperature; impurities were filtered, the solvent acetonitrile was removed by vacuum drying, the mixture was washed with ethyl acetate solvent, and then vacuum dried to obtain N-2-hydroxyethylpyridine bromide; (2) Preparation of ionic liquid: N-2-hydroxyethylpyridine bromide was dissolved in deionized water in a reaction vessel. Under light-proof and room temperature conditions, the aqueous solution of LiTFSI was slowly added while stirring. The stirring was continued for a period of time. After the reaction was completed, the product formed two liquid layers. The organic phase was collected, filtered, and then vacuum dried to obtain the hydroxyl-modified ionic liquid. (3) Conjugate connection of ionic liquid and graphene oxide: Add graphene oxide and the ionic liquid prepared in step (2) to the reaction vessel, stir for a period of time in the dark to obtain graphene oxide modified ionic liquid; (4) PU foaming and covalent grafting: The graphene oxide modified ionic liquid obtained in step (3) is added to polyether polyol, foaming agent and catalyst in sequence and stirred in a mixing tank for a period of time to form a homogeneous mixture; the premixed liquid and isocyanate are quickly mixed in proportion and mixed by impact using a high-pressure foaming machine. After mixing, the material is quickly injected into the mold; the material is freely foamed and gelled in the mold, and the foam after demolding is subjected to heat treatment; finally, the foam is placed at room temperature for more than 24 hours to make its shape and performance completely stable. (5) Sensor assembly; (6) Sensor packaging: The assembled sensor core is packaged using double-layer PET film.

2. The method for preparing an ionized pressure sensor based on graphene oxide-modified ionic liquid according to claim 1, characterized in that: The specific steps (5) are as follows: the graphene electrode is prepared by screen printing process, the PU foam ionization layer after cutting is sandwiched between the two electrodes, and the electrode leads are connected.

3. The method for preparing an ionized pressure sensor based on graphene oxide-modified ionic liquid according to claim 1, characterized in that: The specific steps (6) are as follows: For the upper and lower layers of PET film used for encapsulation, the active area of ​​the sensor is pre-cut to ensure that the active area is unobstructed. On the lower PET encapsulation film, a layer of pressure-sensitive adhesive is evenly coated by screen printing or dispensing. The sensor core is precisely placed on the adhesive-coated area of ​​the lower encapsulation film to ensure that the electrode leads are exposed. The upper PET encapsulation film, which has been pre-cut and coated with pressure-sensitive adhesive, is then placed on the surface of the sensor core. A light rolling process is performed at room temperature using a roller or flatbed press to remove air bubbles between layers. A ring of UV adhesive is then applied around the active area of ​​the sensor using dispensing equipment to form a sealing ring. The UV adhesive sealing ring is irradiated with ultraviolet light to cure and form a solid shape; under the set temperature and pressure parameters, the final pressing and curing of the overall structure is completed, while further removing residual air bubbles.

4. The method for preparing an ionized pressure sensor based on graphene oxide-modified ionic liquid according to claim 1, characterized in that: In step (1): By mass parts: 1 part pyridine, 1-5 parts 2-bromoethanol, 5-20 parts anhydrous acetonitrile; The heating temperature is 70-100℃, the stirring speed is 100-1000 rpm, and the stirring time is 1-48h.

5. The method for preparing an ionized pressure sensor based on graphene oxide-modified ionic liquid according to claim 1, characterized in that: In step (2): By mass parts: 1 part N-2-hydroxyethylpyridine bromide, 0.5-5 parts LiTFSI, 10-20 parts deionized water; The stirring time is 1-48 hours, and the stirring speed is 100-1000 rpm.

6. The method for preparing an ionized pressure sensor based on graphene oxide-modified ionic liquid according to claim 1, characterized in that: In step (3): By mass fractions: 1 part graphene oxide and 0.5-3 parts ionic liquid prepared in step (2); The stirring time is 1-48 hours, and the stirring speed is 100-2000 rpm.

7. The method for preparing an ionized pressure sensor based on graphene oxide-modified ionic liquid according to claim 1, characterized in that: In step (4): The foaming agent is either water-based or a chemical foaming agent; The catalyst is an amine or organometallic catalyst; By mass fractions: 100 parts polyether polyol, 0.1-5 parts graphene-modified ionic liquid prepared in step (3), 0.1-5 parts foaming agent, and 0.1-5 parts catalyst; The pre-mixing time is 0.1-2 hours, the pre-mixing speed is 100-1000 rpm, and the pre-mixing temperature is 40-100℃. The isocyanate is MDI or TDI; By weight: 100 parts premix, 20-100 parts isocyanate. The heat treatment temperature is 50-200℃, and the heat treatment time is 10-300min.

8. The method for preparing an ionized pressure sensor based on graphene oxide-modified ionic liquid according to claim 2, characterized in that: In step (5): The electrode is a flexible electrode; The thickness of the ionized layer of PU foam is 50-500um.

9. The ionized pressure sensor of graphene oxide modified ionic liquid according to claim 3, characterized in that: In step (6): The active area of ​​the sensor is pre-cut out, with its length and width matching the sensor size and its thickness being half the sensor size; The pressing and curing process is carried out at a temperature of 50-100℃, a pressure of 0.1-2MPa, and a time of 1-10min.

10. An ionized pressure sensor based on graphene oxide-modified ionic liquid, characterized in that: It is prepared by any one of the preparation methods described in claims 1-9.