All-solid-state ionic liquid-MXene composite film self-energized linear pressure sensor and preparation method thereof

Abstract

The invention belongs to the field of sensors, discloses an all-solid-state ionic liquid-MXene composite film self-energized linear pressure sensor and a preparation method thereof, and aims at solving the problems that a traditional sensor is prone to liquid leakage and low in sensitivity. And spin-coating the ionic liquid on the MXene film to obtain the ionic liquid-MXene composite film. The composite film is arranged in the middle of a polytetrafluoroethylene film with preformed holes to form a sandwich structure, the sandwich structure is clamped by two self-made polymer cavities, and the polymer cavities are sealed by flexible films. Solid gel electrolyte is added into the polymer cavity, and an Ag / AgCl electrode is inserted to serve as a working electrode. Compared with an MXene film, the composite film shows more excellent mechanical properties. Due to the electrostatic interaction, positive ions in the electrolyte are adsorbed on the surfaces of the nano channels of the composite membrane, and negative ions are repelled. Under the pressure, cations in the electrolyte can pass through the nano channel of the composite membrane and move directionally to generate an electric signal, and the self-energized characteristic is achieved.

Description

Technical Field

[0001] The present invention belongs to the field of sensors, and in particular relates to a self-powered linear pressure sensor. Background Art

[0002] With the rapid development of the Internet of Things (IoT), demand for self-powered pressure sensors is increasing in applications such as medical monitoring and industrial sensing. However, existing technologies still face two core challenges: the nonlinear response between force and electrical signals and the reliability limitations of liquid electrolytes, which severely restrict the practical application value of these sensors.

[0003] First, in terms of ion transport channel design, although traditional two-dimensional materials (such as MXene) have abundant interlayer channels, their easy stacking characteristics significantly limit the efficiency of ion migration. For example, in order to further improve the sensitivity of self-powered pressure sensors and solve the technical problem of their slow response time, the applicant previously disclosed CN118913485A, which studied the insertion of carbon nanotubes into MXene layered materials. Although this research improved the ion transport efficiency to a certain extent, it still faced some problems. For example, although liquid electrolytes (such as salt solutions) have high ion mobility, their leakage risk leads to a sharp decline in device reliability, severely limiting the application of flexible devices, and the ion transport efficiency is still unsatisfactory. In addition, although traditional solid-state electrolytes (such as ceramic materials) solve the leakage problem, their rigidity is fundamentally inconsistent with the flexibility requirements of wearable devices. Summary of the Invention

[0004] To address the above technical issues, the present invention proposes an all-solid-state ionic liquid-MXene composite membrane self-powered linear pressure sensor and its preparation method. The sensor's fabrication process is simple, energy-efficient, and environmentally friendly, while also achieving high precision while being self-powered.

[0005] To achieve the above object, the technical solution of the present invention is implemented as follows: A method for preparing an all-solid-state ionic liquid (Ionic Liquid)-MXene composite membrane self-powered linear pressure sensor, comprising the following steps: (1) Etching the precursor MAX to obtain a MXene colloidal solution, and then filtering to obtain a MXene film; (2) The MXene film is placed on a spin coater, and the ionic liquid is added dropwise to the MXene film. The ionic liquid-MXene composite film with incomplete penetration of the ionic liquid is obtained by spin coating; The introduction of the ionic liquid repairs interlayer defects in the MXene, shortens the ion transport path, and forms a stable "brick-and-mortar" structure. The hydrophobic ionic liquid side promotes ion dehydration and reduces transport resistance, while the hydrophilic MXene side provides abundant water sites for electrolyte ions. Through the design of asymmetric wettability, the two work synergistically to achieve dynamic regulation of ion transport behavior and enhance ion transport performance across the membrane.

[0006] (3) The ionic liquid-MXene composite membrane is placed between the double-sided porous dielectric layers to form a sandwich structure; wherein the integrity of the sandwich structure is achieved by using a silicone joint sealant during assembly. During specific assembly or use, the ionic liquid-MXene composite membrane can be cut as needed.

[0007] (4) The sandwich structure is mechanically fixed using two polymer cavities. The internal configuration of the polymer cavity matches the space of the double-sided porous dielectric layer, and the outside of the polymer cavity is airtightly protected by a flexible packaging film. (5) Filling the polymer cavity with a solid gel electrolyte; filling the reserved space to ensure the formation of a continuous ion conduction channel while avoiding interfacial peeling with the composite membrane; (6) An embedded mounting process was used to place an Ag / AgCl reference electrode in a solid gel electrolyte to obtain a fully solid-state ionic liquid-MXene composite membrane self-powered linear pressure sensor. The spatial isolation design kept the reference electrode and the composite membrane in a non-contact state, effectively reducing the interfacial polarization effect.

[0008] The etching in the above step (1) refers to selectively etching the precursor MAX phase with HCl and LiF; after etching, it also includes physical assisted intercalation, multi-stage centrifugal purification and ultrasonic stripping treatment.

[0009] Furthermore, in the MAX phase in the above step (1), M is a transition metal, A is mainly a group III element or a group IV element, and X is any one or a combination of C and N elements.

[0010] The thickness of the MXene film in step (2) above is 7.03 μm and the size is 9.6 cm 2 , add 0.8-1.2 mL of ionic liquid dropwise.

[0011] Furthermore, the ionic liquid is any one of 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, and 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide.

[0012] In the above step (3), the double-sided porous dielectric layer is two polytetrafluoroethylene films with pre-reserved holes (e.g., the size is 20×15 mm, the size of the pre-reserved hole is 3 mm). 2 ).

[0013] In step (4), the polymer cavity is a self-made polymer cavity (e.g., a cavity with a size of 20 × 15 × 3 mm, a circular through hole with a diameter of 10 mm in the middle, and a material of silicone rubber). The reserved hole of the polytetrafluoroethylene film is arranged corresponding to the position of the circular through hole of the polymer cavity, forming a spatial match, thereby achieving contact between the ionic liquid-MXene composite membrane and the solid electrolyte.

[0014] Furthermore, mechanical fixing refers to the two polymer cavities being arranged relative to each other to clamp the sandwich structure. In addition, the interface between the two polymer cavities can be sealed with a polymer (such as V-705 polymer).

[0015] The solid gel electrolyte in the above step (5) is any one of a polyacrylamide (PAM)-based gel electrolyte, a polyvinyl alcohol (PVA)-based gel electrolyte, a polyacrylonitrile (PAN)-based gel electrolyte, a polyvinylidene fluoride (PVDF)-based gel electrolyte and a poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)-based gel electrolyte.

[0016] Furthermore, the electrolyte in the solid gel electrolyte is sodium chloride, potassium chloride or magnesium chloride.

[0017] Taking polyacrylamide (PAM)-based gel electrolyte as an example, its preparation method is: add N,N'-methylenebisacrylamide (MBAA), ammonium persulfate (APS) and electrolyte to acrylamide solution, and then add tetramethylethylenediamine (TEMED) and solidify to obtain it.

[0018] The final concentration of the electrolyte added is 0.001-0.05 M.

[0019] Furthermore, the electrolyte was added to a final concentration of 0.01 M.

[0020] In step (6), the Ag / AgCl reference electrode can be inserted into the polymer cavity through the micropores formed by the syringe, and the gap between the Ag / AgCl reference electrode and the micropores is sealed. The Ag / AgCl reference electrode is only placed in the solid gel electrolyte and does not directly contact the ionic liquid-MXene composite membrane.

[0021] An all-solid-state ionic liquid-MXene composite membrane self-powered linear pressure sensor was prepared using the above-mentioned preparation method.

[0022] Furthermore, the all-solid-state ionic liquid-MXene composite membrane self-powered linear pressure sensor comprises an ionic liquid-MXene composite membrane, a solid gel electrolyte, a polytetrafluoroethylene film, a polymer cavity, a flexible encapsulation film, and an Ag / AgCl reference electrode. Polytetrafluoroethylene films with pre-reserved holes are provided on either side of the ionic liquid-MXene composite membrane (ion-selective membrane), forming a sandwich structure. Polymer cavities are provided outside the polytetrafluoroethylene films, each filled with a solid gel electrolyte that provides ions to the ionic liquid-MXene composite membrane (ion-selective membrane). Flexible films are provided outside the polymer cavities to seal the ionic liquid-MXene composite membrane, hydrogel, polytetrafluoroethylene film, and two polymer cavities within the flexible film. The Ag / AgCl reference electrode is inserted into the gel electrolyte within the polymer cavity, connected to an external circuit and not in direct contact with the ionic liquid-MXene composite membrane.

[0023] Among them, since the surface of the ionic liquid-MXene composite membrane is negatively charged, it will attract cations in the gel electrolyte to adhere to the surface and repel anions. When external pressure is applied, the cations will pass through the composite membrane to form an electrical signal, realizing the conversion of pressure-electrical signal, thereby realizing the self-power supply of the sensor.

[0024] The voltage-pressure linearity of the above-mentioned all-solid-state ionic liquid-MXene composite membrane self-powered linear pressure sensor is 0.999, and the current-pressure linearity is 0.993.

[0025] The above-mentioned all-solid-state ionic liquid-MXene composite membrane self-powered linear pressure sensor has a current response time of 52 ms when the pressure is 1.2 kPa, and a voltage response time of 65 ms when the pressure is 3.7 kPa.

[0026] The above-mentioned all-solid-state ionic liquid-MXene composite membrane self-powered linear pressure sensor is used in the field of medical monitoring or industrial sensing for non-disease diagnosis purposes.

[0027] The beneficial effects produced by the present invention are: (1) The MXene used in the present invention is a member of the two-dimensional material family and has the characteristics of good flexibility, high mechanical strength, hydrophilic surface, end groups rich in negative charge, and variable surface charge. The MXene membrane has a large number of nanochannels with adjustable channel spacing, but its easy stacking property limits ion transport. As an organic electrolyte, ionic liquid not only has excellent thermal / chemical stability, adjustable composition and high charge density, but also can prevent the stacking of two-dimensional nanosheets and regulate their interlayer spacing. By spin-coating ionic liquid on the surface of the MXene membrane, an incompletely impregnated ionic liquid-MXene composite membrane is obtained, which has excellent mechanical properties and good stability in water.

[0028] (2) The sensor of the present invention can provide high-precision pressure measurement, and the output signal is linearly related to the pressure change. The relationship between the current corresponding to the pressure-to-electrical energy conversion and the corresponding pressure is: , where is the dielectric constant of the electrolyte, is the viscosity of the electrolyte, is the surface potential of the nanochannel, is the channel cross-sectional area, and is the length of the nanochannel. Generally speaking, for a given electrolyte and composite membrane, these parameters are constants. Therefore, the corresponding pressure difference value can be obtained from the current generated by the test, and there is a linear relationship between the two, which enables the sensor to accurately reflect the pressure change and provide reliable data support for various applications. Ionic liquids can not only seal tiny defects in the composite membrane and form a stable ion transmission path, but also have high ionic conductivity and good fluidity, which can significantly reduce the resistance of ion transmission between layers, thereby improving the ion transmission efficiency. When stimulated by external pressure (pressure of 3.7 kPa), the response time of the sensor voltage can be as low as 65 ms, and the recovery time is 85 ms. When the ionic liquid is spin-coated only on one side of the MXene, the linearity of the input pressure-output voltage is 0.999, and the linearity of the input pressure-output current is 0.993, which has a good linear relationship and is conducive to high-precision pressure measurement.

[0029] (3) The sensor prepared by the present invention has a high output voltage and output current density. The introduction of ionic liquid repairs the defects between MXene layers, shortens the ion transmission path, and forms a stable "brick-mortar" structure. The hydrophobic ionic liquid side promotes ion dehydration and reduces the transmission resistance, while the hydrophilic MXene side provides abundant water sites for electrolyte ions. Through the design of asymmetric wettability, the two work together to achieve dynamic regulation of ion transmission behavior and enhance the ion transmembrane transmission performance. Specifically, when the pressure is 10 kPa, the output current density is 103.65 mA / m 2 ; When the pressure is 8.3kPa, the output voltage is 1.62 mV.

[0030] (4) The innovative use of an all-solid-state gel electrolyte system fundamentally eliminates the risk of liquid electrolyte leakage. The three-dimensional network structure of the gel combines high ionic conductivity with excellent mechanical flexibility, ensuring the long-term stability of the sensor under complex working conditions such as dynamic bending. At the same time, the close interfacial contact between the solid electrolyte and the functionalized composite membrane further reduces signal transmission loss, allowing the sensor to maintain reliable performance output even in harsh environments such as high humidity. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1 This is a schematic diagram of the preparation process of the all-solid-state ionic liquid-MXene composite membrane self-powered linear pressure sensor according to Example 1 of the present invention.

[0033] Figure 2 The precursor Ti3AlC2 used in the present invention and the prepared Ti3C2T X XRD pattern of .

[0034] Figure 3 XRD patterns of ionic liquid-MXene composite films prepared in Examples and Comparative Examples of the present invention; IL-MXene is the composite film prepared in Example 1; MXene is the MXene film prepared in Comparative Example 1; and IL / MXene is the composite film prepared in Comparative Example 2.

[0035] Figure 4 Cross-sectional SEM images of the MXene film (a) prepared in Comparative Example 1 of the present invention, the ionic liquid-MXene composite film (b) prepared in Example 1, and the ionic liquid / MXene composite film (c) prepared in Comparative Example 2.

[0036] Figure 5 (a) An optical image of the ionic liquid-MXene film prepared in Example 1 of the present invention and (b) a graph showing the mass fraction of the ionic liquid in the composite membranes prepared in Example 1 and Comparative Example 2.

[0037] Figure 6 These are pictures of the mechanical properties of the MXene film prepared in Comparative Example 1 of the present invention and the ionic liquid-MXene film prepared in Example 1.

[0038] Figure 7 VT diagrams of the ionic liquid-MXene composite membrane prepared in Example 1 of the present invention and the MXene membranes and ionic liquid / MXene composite membranes prepared in Comparative Examples 1 and 2; wherein, IL-MXene and MXene-IL are VT diagrams corresponding to the ionic liquid-MXene composite membrane prepared in Example 1 when pressure is applied on the ionic liquid side and the MXene side, respectively; MXene is the VT diagram corresponding to the MXene membrane prepared in Comparative Example 1; IL / MXene is the VT diagram corresponding to the ionic liquid / MXene composite membrane prepared in Comparative Example 2.

[0039] Figure 8 IT diagram (a) and IP diagram (b) of the self-powered linear pressure sensor prepared in Example 1 of the present invention at different pressures.

[0040] Figure 9 VT diagram (a) and VP diagram (b) of the self-powered linear pressure sensor prepared in Example 1 of the present invention at different pressures.

[0041] Figure 10 (a) Graph showing the current response and recovery time, and (b) graph showing the voltage response and recovery time of the self-powered linear pressure sensor prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0042] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0043] A method for preparing an all-solid-state ionic liquid-MXene composite membrane self-powered linear pressure sensor, comprising the following steps: (1) Etching the precursor MAX to obtain a MXene colloidal solution, and then filtering to obtain a MXene film; (2) The MXene film is placed on a spin coater, and the ionic liquid is added dropwise to the MXene film. An ionic liquid-MXene composite film with incomplete penetration of the ionic liquid is obtained by spin coating; (3) Placing the ionic liquid-MXene composite membrane between two double-sided porous dielectric layers (two polytetrafluoroethylene films with pre-reserved holes) to form a sandwich structure; (4) The sandwich structure is mechanically fixed using two polymer cavities. The internal configuration of the polymer cavity matches the space of the double-sided porous dielectric layer, and the outside of the polymer cavity is airtightly protected by a flexible packaging film. (5) Filling the polymer cavity with a solid gel electrolyte; filling the reserved space to ensure the formation of a continuous ion conduction channel while avoiding interfacial peeling with the composite membrane; (6) An embedded mounting process was used to place an Ag / AgCl reference electrode in a solid gel electrolyte to obtain a fully solid-state ionic liquid-MXene composite membrane self-powered linear pressure sensor. The spatial isolation design kept the reference electrode and the composite membrane in a non-contact state, effectively reducing the interfacial polarization effect.

[0044] The etching in the above step (1) refers to the selective etching of the precursor MAX phase by HCl and LiF, wherein M is a transition metal, A is mainly a group III element or a group IV element, and X is any one or a combination of two elements of C and N.

[0045] In the above step (6), the Ag / AgCl electrode is only placed in the solid gel electrolyte and is not in direct contact with the ionic liquid-MXene composite membrane.

[0046] Among them, the specific assembly method of the self-powered linear pressure sensor is an existing technology, which can be referred to in the literature (K. Chen, M. Gao, X. Liu, H. Xing, H. Sun, H. Wang, A. Lou, X. Song, W. Liu, H. Guo, Self-Powered Linear Pressure Sensor Based on MXene / CNT Nanofluid Membrane. Small 2025, 21, 2411706.).

[0047] Example 1 The preparation method of the all-solid-state ionic liquid-MXene composite membrane self-powered linear pressure sensor of this embodiment is shown in the flow chart. Figure 1 As shown, the steps are as follows: (1) A MXene solution of a certain concentration was obtained by selectively etching the precursor MAX phase with HCl and LiF. Specifically, 1.0 g of LiF powder and 1.0 g of Ti3AlC2 were weighed, and LiF and 20.0 mL of HCl (75 wt.%) were mixed. Ti3AlC2 (MAX phase) was slowly added to the mixed solution, and the mixture was fully reacted at 35°C for 27 h by magnetic stirring. After the reaction, the obtained acidic reactant was placed in a centrifuge tube, deionized water was added, and the centrifuge speed was set to 3500 rpm. Centrifugation was performed for 3 min to obtain a precipitate. Deionized water was added again for a second centrifugal washing. At the same time, water molecules were inserted into the interlayer by hand shaking to increase the interlayer spacing of the product. The above process was repeated several times using a multi-stage centrifugation method until the pH value of the reactant was neutral. Then, the precipitate was dispersed in a certain amount of deionized water, argon was continuously introduced in a water bath below 15°C, and ultrasonic exfoliation was performed using an ultrasonic machine for 1 h. Finally, the supernatant was collected by centrifugation at 3500 rpm for 1 h, which was the monolayer Ti3C2T xNanosheet colloidal solution, i.e., MXene solution. A small amount of MXene solution was weighed, vacuum-filtered for 2 h, and allowed to stand for 24 h. The solution was then peeled off from the filter paper to obtain a self-supporting MXene film of predetermined thickness. The MXene film had a thickness of 7.03 μm and a size of 9.6 cm. 2 .

[0048] (2) Place the MXene film on a spin coater and add 1 mL of ionic liquid (1-butyl-3-methylimidazole bis(trifluoromethyl)sulfonyl)imide) by spin coating to obtain an ionic liquid-MXene composite film, referred to as IL-MXene.

[0049] (3) Add 7.71 g of acrylamide monomer to 50 mL of deionized (DI) water and stir magnetically to obtain an acrylamide solution. Add 0.03 g of N,N'-methylenebisacrylamide (MBAA) and 0.08 g of ammonium persulfate (APS) to the acrylamide solution to obtain a mixed solution. Take 2 mL of the prepared solution, add a certain amount of sodium chloride to obtain a solution with a sodium chloride concentration of 0.01 M, and degas in a vacuum for 5 min. Add 5 μL of tetramethylethylenediamine (TEMED) to the above solution. Finally, the solution is dripped into a mold and cured at 60°C for 2 h to obtain a polyacrylamide-based gel electrolyte.

[0050] (4) Cut the ionic liquid-MXene composite membrane prepared in step (2) into a size of 5 × 5 mm and place it on two polytetrafluoroethylene films with pre-holes (size of 20 × 15 mm, with a pre-hole size of 3 mm). 2 ) to form a sandwich structure, and a homemade polymer cavity (made of silicone rubber, with a size of 20×15×3 mm and a circular through hole with a diameter of 10 mm in the middle) is used to mechanically fix the core unit, and the outside of the cavity is airtightly protected by a flexible packaging film (made of nitrile rubber); high-performance polyacrylamide-based gel electrolyte is filled into the cavity to fill the reserved space, ensuring the formation of a continuous ion conduction channel while avoiding interface peeling with the composite membrane.

[0051] (5) Using an embedded installation process, the Ag / AgCl reference electrode was inserted into the polyacrylamide-based gel electrolyte through the micropores formed by the syringe, and the gap between the Ag / AgCl reference electrode and the micropores was sealed. The electrode and the composite membrane were kept in a non-contact state through a spatial isolation design, and an all-solid-state ionic liquid-MXene composite membrane self-powered linear pressure sensor (also known as a 2D Nanofluid Sensor) was prepared.

[0052] Example 2 The preparation method of the all-solid-state ionic liquid-MXene composite membrane self-powered linear pressure sensor of this embodiment comprises the following steps: (1) A MXene solution of a certain concentration was obtained by selectively etching the precursor MAX phase with HCl and LiF. Specifically, 1.0 g of LiF powder and 1.0 g of Ti3AlC2 were weighed, and LiF and 20.0 mL of HCl (75 wt.%) were mixed. Ti3AlC2 (MAX phase) was slowly added to the mixed solution, and the mixture was fully reacted at 35°C for 27 h by magnetic stirring. After the reaction, the obtained acidic reactant was placed in a centrifuge tube, deionized water was added, and the centrifuge speed was set to 3500 rpm. Centrifugation was performed for 3 min to obtain a precipitate. Deionized water was added again for a second centrifugal washing. At the same time, water molecules were inserted into the interlayer by hand shaking to increase the interlayer spacing of the product. The above process was repeated several times using a multi-stage centrifugation method until the pH value of the reactant was neutral. Then, the precipitate was dispersed in a certain amount of deionized water, argon was continuously introduced in a water bath below 15°C, and ultrasonic exfoliation was performed using an ultrasonic machine for 1 h. Finally, the supernatant was collected by centrifugation at 3500 rpm for 1 h, which was the monolayer Ti3C2T x Nanosheet colloidal solution, i.e., MXene solution. A small amount of MXene solution was weighed, vacuum-filtered for 2 h, and allowed to stand for 24 h. The solution was then peeled off from the filter paper to obtain a self-supporting MXene film of predetermined thickness and surface morphology. The MXene film had a thickness of 7.03 µm and a size of 9.6 cm. 2 .

[0053] (2) Place the MXene film on a spin coater and add 0.8 mL of ionic liquid (1-butyl-3-methylimidazole bis(trifluoromethyl)sulfonyl)imide) by spin coating to obtain an ionic liquid-MXene composite film, referred to as IL-MXene.

[0054] (3) 7.71 g of acrylamide monomer was added to 50 mL of deionized (DI) water and magnetically stirred to obtain an acrylamide solution. 0.03 g of N,N'-methylenebisacrylamide (MBAA) and 0.08 g of ammonium persulfate (APS) were added to the acrylamide solution to obtain a mixed solution. 2 mL of the prepared solution was added with a certain amount of sodium chloride to obtain a solution with a sodium chloride concentration of 0.01 M. The solution was degassed in a vacuum for 5 min. 5 µL of tetramethylethylenediamine (TEMED) was added to the above solution. Finally, the solution was dropwise poured into a mold and cured at 60 °C for 2 h to obtain a polyacrylamide-based gel electrolyte.

[0055] (4) Cut the ionic liquid-MXene composite membrane prepared in step (2) into a size of 5 × 5 mm and place it on two polytetrafluoroethylene films with pre-holes (size of 20 × 15 mm, with a pre-hole size of 3 mm). 2 ) to form a sandwich structure, and a homemade polymer cavity (made of silicone rubber, with a size of 20×15×3 mm and a circular through hole with a diameter of 10 mm in the middle) is used to mechanically fix the core unit, and the outside of the cavity is airtightly protected by a flexible packaging film (made of nitrile rubber); high-performance polyacrylamide-based gel electrolyte is filled into the cavity to fill the reserved space, ensuring the formation of a continuous ion conduction channel while avoiding interface peeling with the composite membrane.

[0056] (5) Using an embedded installation process, the Ag / AgCl reference electrode was inserted into the polyacrylamide-based gel electrolyte through the micropores formed by the syringe, and the gap between the Ag / AgCl reference electrode and the micropores was sealed. A spatial isolation design was used to maintain a non-contact state between the electrode and the composite membrane, resulting in a fully solid-state ionic liquid-MXene composite membrane self-powered linear pressure sensor.

[0057] Example 3 The preparation method of the all-solid-state ionic liquid-MXene composite membrane self-powered linear pressure sensor of this embodiment is shown in the flow chart. Figure 1 As shown, the steps are as follows: (1) A MXene solution of a certain concentration was obtained by selectively etching the precursor MAX phase with HCl and LiF. Specifically, 1.0 g of LiF powder and 1.0 g of Ti3AlC2 were weighed, and LiF and 20.0 mL of HCl (75 wt.%) were mixed. Ti3AlC2 (MAX phase) was slowly added to the mixed solution, and the mixture was fully reacted at 35°C for 27 h by magnetic stirring. After the reaction, the obtained acidic reactant was placed in a centrifuge tube, deionized water was added, and the centrifuge speed was set to 3500 rpm. Centrifugation was performed for 3 min to obtain a precipitate. Deionized water was added again for a second centrifugal washing. At the same time, water molecules were inserted into the interlayer by hand shaking to increase the interlayer spacing of the product. The above process was repeated several times using a multi-stage centrifugation method until the pH value of the reactant was neutral. Then, the precipitate was dispersed in a certain amount of deionized water, argon was continuously introduced in a water bath below 15°C, and ultrasonic exfoliation was performed using an ultrasonic machine for 1 h. Finally, the supernatant was collected by centrifugation at 3500 rpm for 1 h, which was the monolayer Ti3C2T xNanosheet colloidal solution, i.e., MXene solution. A small amount of MXene solution was weighed, vacuum-filtered for 2 h, and allowed to stand for 24 h. The solution was then peeled off from the filter paper to obtain a self-supporting MXene film of predetermined thickness and surface morphology. The MXene film had a thickness of 7.03 μm and a size of 9.6 cm. 2 .

[0058] (2) Place the MXene film on a spin coater and add 1.2 mL of ionic liquid (1-butyl-3-methylimidazole bis(trifluoromethyl)sulfonyl)imide) by spin coating to obtain an ionic liquid-MXene composite film, referred to as IL-MXene.

[0059] (3) 7.71 g of acrylamide monomer was added to 50 mL of deionized (DI) water and magnetically stirred to obtain an acrylamide solution. 0.03 g of N,N'-methylenebisacrylamide (MBAA) and 0.08 g of ammonium persulfate (APS) were added to the acrylamide solution to obtain a mixed solution. 2 mL of the prepared solution was added with a certain amount of sodium chloride to obtain a solution with a sodium chloride concentration of 0.01 M. The solution was degassed in a vacuum for 5 min. 5 µL of tetramethylethylenediamine (TEMED) was added to the above solution. Finally, the solution was dropwise poured into a mold and cured at 60 °C for 2 h to obtain a polyacrylamide-based gel electrolyte.

[0060] (4) Cut the ionic liquid-MXene composite membrane prepared in step (2) into a size of 5 × 5 mm and place it on two polytetrafluoroethylene films with pre-holes (size of 20 × 15 mm, with a pre-hole size of 3 mm). 2 ) to form a sandwich structure, and a homemade polymer cavity (made of silicone rubber, with a size of 20×15×3 mm and a circular through hole with a diameter of 10 mm in the middle) is used to mechanically fix the core unit, and the outside of the cavity is airtightly protected by a flexible packaging film (made of nitrile rubber); high-performance polyacrylamide-based gel electrolyte is filled into the cavity to fill the reserved space, ensuring the formation of a continuous ion conduction channel while avoiding interface peeling with the composite membrane.

[0061] (5) Using an embedded installation process, the Ag / AgCl reference electrode was inserted into the polyacrylamide-based gel electrolyte through the micropores formed by the syringe, and the gap between the Ag / AgCl reference electrode and the micropores was sealed. A spatial isolation design was used to maintain a non-contact state between the electrode and the composite membrane, resulting in a fully solid-state ionic liquid-MXene composite membrane self-powered linear pressure sensor.

[0062] Comparative Example 1 This comparative example is a preparation method of a MXene film sensor, and the preparation method is as follows: (1) A MXene solution of a certain concentration was obtained by selectively etching the precursor MAX phase with HCl and LiF. Specifically, 1.0 g of LiF powder and 1.0 g of Ti3AlC2 were weighed, and LiF and 20.0 mL of HCl (75 wt.%) were mixed. Ti3AlC2 (MAX phase) was slowly added to the mixed solution, and the mixture was fully reacted at 35°C for 27 h by magnetic stirring. After the reaction, the obtained acidic reactant was placed in a centrifuge tube, deionized water was added, and the centrifuge speed was set to 3500 rpm. Centrifugation was performed for 3 min to obtain a precipitate. Deionized water was added again for a second centrifugal washing. At the same time, water molecules were inserted into the interlayer by hand shaking to increase the interlayer spacing of the product. The above process was repeated several times using a multi-stage centrifugation method until the pH value of the reactant was neutral. Then, the precipitate was dispersed in a certain amount of deionized water, argon was continuously introduced in a water bath below 15°C, and ultrasonic exfoliation was performed using an ultrasonic machine for 1 h. Finally, the supernatant was collected by centrifugation at 3500 rpm for 1 h, which was the monolayer Ti3C2T x Nanosheet colloidal solution, i.e., MXene solution. A small amount of MXene solution was weighed, vacuum-filtered for 2 h, and allowed to stand for 24 h. The solution was then peeled off from the filter paper to obtain a self-supporting MXene film of predetermined thickness and surface morphology. The MXene film had a thickness of 7.03 μm and a size of 9.6 cm. 2 .

[0063] (2) 7.71 g of acrylamide monomer was added to 50 mL of deionized (DI) water and magnetically stirred to obtain an acrylamide solution. 0.03 g of N,N'-methylenebisacrylamide (MBAA) and 0.08 g of ammonium persulfate (APS) were added to the acrylamide solution to obtain a mixed solution. 2 mL of the prepared solution was added with a certain amount of sodium chloride to obtain a solution with a sodium chloride concentration of 0.01 M. The solution was then degassed in a vacuum for 5 min. 5 µL of tetramethylethylenediamine (TEMED) was added to the above solution. Finally, the solution was dropwise poured into a mold and cured at 60 °C for 2 h to obtain a polyacrylamide-based gel electrolyte.

[0064] (3) Cut the MXene film obtained in step (1) into 5 × 5 mm and place it on two polytetrafluoroethylene films with pre-holes (20 × 15 mm, with a pre-hole size of 3 mm). 2) to form a sandwich structure, and a homemade polymer cavity (made of silicone rubber, with a size of 20×15×3 mm and a circular through hole with a diameter of 10 mm in the middle) is used to mechanically fix the core unit, and the outside of the cavity is airtightly protected by a flexible packaging film (made of nitrile rubber); high-performance polyacrylamide-based gel electrolyte is filled into the cavity to fill the reserved space, ensuring the formation of a continuous ion conduction channel while avoiding interface peeling with the composite membrane.

[0065] (4) Using an embedded installation process, the Ag / AgCl reference electrode was inserted into the polyacrylamide-based gel electrolyte through the micropores formed by the syringe, and the gap between the Ag / AgCl reference electrode and the micropores was sealed. The electrode and the composite membrane were kept in a non-contact state through a spatial isolation design, and an all-solid-state MXene thin film self-powered linear pressure sensor was prepared.

[0066] Comparative Example 2 The preparation method of the all-solid-state ionic liquid / MXene composite membrane self-powered linear pressure sensor of this embodiment comprises the following steps: (1) A MXene solution of a certain concentration was obtained by selectively etching the precursor MAX phase with HCl and LiF. Specifically, 1.0 g of LiF powder and 1.0 g of Ti3AlC2 were weighed, and LiF and 20.0 mL of HCl (75 wt.%) were mixed. Ti3AlC2 (MAX phase) was slowly added to the mixed solution, and the mixture was fully reacted at 35°C for 27 h by magnetic stirring. After the reaction, the obtained acidic reactant was placed in a centrifuge tube, deionized water was added, and the centrifuge speed was set to 3500 rpm. Centrifugation was performed for 3 min to obtain a precipitate. Deionized water was added again for a second centrifugal washing. At the same time, water molecules were inserted into the interlayer by hand shaking to increase the interlayer spacing of the product. The above process was repeated several times using a multi-stage centrifugation method until the pH value of the reactant was neutral. Then, the precipitate was dispersed in a certain amount of deionized water, argon was continuously introduced in a water bath below 15°C, and ultrasonic exfoliation was performed using an ultrasonic machine for 1 h. Finally, the supernatant was collected by centrifugation at 3500 rpm for 1 h, which was the monolayer Ti3C2T x Nanosheet colloidal solution, i.e., MXene solution. A small amount of MXene solution was weighed, vacuum-filtered for 2 h, and allowed to stand for 24 h. The solution was then peeled off from the filter paper to obtain a self-supporting MXene film of predetermined thickness and surface morphology. The MXene film had a thickness of 7.03 μm and a size of 9.6 cm. 2 .

[0067] (2) The MXene film was soaked in 2 mL of ionic liquid (1-butyl-3-methylimidazolium bis(trifluoromethyl)sulfonyl)imide) for 2 h and then placed on a spin coater. The ionic liquid / MXene composite film was finally obtained by spin coating, referred to as IL / MXene.

[0068] (3) 7.71 g of acrylamide monomer was added to 50 mL of deionized (DI) water and magnetically stirred to obtain an acrylamide solution. 0.03 g of N,N'-methylenebisacrylamide (MBAA) and 0.08 g of ammonium persulfate (APS) were added to the acrylamide solution to obtain a mixed solution. 2 mL of the prepared solution was added with a certain amount of sodium chloride to obtain a solution with a sodium chloride concentration of 0.01 M. The solution was degassed in a vacuum for 5 min. 5 µL of tetramethylethylenediamine (TEMED) was added to the above solution. Finally, the solution was dropwise poured into a mold and cured at 60 °C for 2 h to obtain a polyacrylamide-based gel electrolyte.

[0069] (4) Cut the ionic liquid-MXene composite membrane prepared in step (2) into a size of 5 × 5 mm and place it on two polytetrafluoroethylene films with pre-holes (size of 20 × 15 mm, with a pre-hole size of 3 mm). 2 ) to form a sandwich structure, and a homemade polymer cavity (made of silicone rubber, with a size of 20×15×3 mm and a circular through hole with a diameter of 10 mm in the middle) is used to mechanically fix the core unit, and the outside of the cavity is airtightly protected by a flexible packaging film (made of nitrile rubber); high-performance polyacrylamide-based gel electrolyte is filled into the cavity to fill the reserved space, ensuring the formation of a continuous ion conduction channel while avoiding interface peeling with the composite membrane.

[0070] (5) Using an embedded installation process, the Ag / AgCl reference electrode was inserted into the polyacrylamide-based gel electrolyte through the micropores formed by the syringe, and the gap between the Ag / AgCl reference electrode and the micropores was sealed. The electrode and the composite membrane were kept in a non-contact state through a spatial isolation design, and an all-solid-state ionic liquid / MXene composite membrane self-powered linear pressure sensor was prepared.

[0071] Implementation effect examples Figure 2 The precursor Ti3AlC2 used in the present invention and the prepared Ti3C2T X From the XRD pattern, it can be seen that the Al in the precursor (Ti3AlC2) was successfully etched away.

[0072] Figure 3The XRD patterns of the ionic liquid-MXene composite films prepared in Example 1 and Comparative Example 2 of the present invention and the MXene film prepared in Comparative Example 1 show that the insertion of ionic liquid into MXene changes the diffraction peak angle of the composite film, thereby changing its interlayer spacing, and that the addition of ionic liquid increases the interlayer spacing of MXene.

[0073] Figure 4 Cross-sectional SEM images of the MXene film (a) prepared in Comparative Example 1 of the present invention, the ionic liquid-MXene composite film (b) prepared in Example 1, and the ionic liquid / MXene composite film (c) prepared in Comparative Example 2. The incompletely infiltrated IL-MXene film shows that the ionic liquid partially penetrates the MXene interlayers, resulting in a larger interlayer spacing than the MXene film. The fully infiltrated IL / MXene film shows that the ionic liquid fully penetrates the MXene interlayers, resulting in the largest interlayer spacing.

[0074] Figure 5a is an optical photograph of the ionic liquid-MXene composite membrane prepared in Example 1 of the present invention. It can be seen that the ionic liquid side and the MXene side exhibit different colors and exhibit excellent flexibility. Figure 5b is a graph showing the mass fraction of ionic liquid in the composite membranes prepared in Example 1 and Comparative Example 2. It can be seen that the mass fraction of ionic liquid in the incompletely wetted IL-MXene membrane is 7.9%, while the mass fraction of ionic liquid in the fully wetted IL / MXene membrane is 17.8%.

[0075] Figure 6 Figures show the mechanical properties of the MXene membrane and the ionic liquid-MXene membrane (Example 1) prepared according to the present invention. The addition of the ionic liquid shows improved mechanical properties for the composite membrane. Specifically, the MXene membrane exhibits a tensile strength of 13.25 MPa and an elongation at break of 5.39%, while the ionic liquid-MXene composite membrane exhibits a tensile strength of 17.72 MPa and an elongation at break of 10.07%.

[0076] Like the MXene membrane, the ionic liquid-MXene composite membrane can adsorb more cations on its surface, which is beneficial to improving the sensitivity and response time of the sensor. Moreover, the interlayer channels of the composite membrane are adjustable, which can control the optimal ion transport performance.

[0077] In order to further detect the performance of the sensor, VT test was performed on the sensors prepared in Example 1 and Comparative Examples 1-2. The specific steps are as follows: the pressure-electrical signal conversion test system consists of a motion control axis, a force gauge and a source meter. The motion control axis applies pressure to the sensor through the propulsion distance, the force gauge tests the pressure, and the source meter records the output electrical signal.

[0078] Figure 7The VT graphs of the films prepared in Example 1, Comparative Example 1, and Comparative Example 2 of the present invention show that the ionic liquid-MXene composite membrane prepared in Example 1 has the best performance, with an output voltage of 3.90 mV. This can be attributed to the following: (1) the hydrophobic side of the heterostructure membrane has a larger confined space, which significantly improves the electrolyte ion storage capacity, promotes the dehydration of hydrated ions, and reduces the friction of ion transmission; (2) the smaller confined space on the hydrophilic side of the heterostructure membrane limits the electrolyte ion storage capacity, and the ion transmission resistance is relatively large; (3) a natural salinity gradient from the hydrophobic side to the hydrophilic side is formed in the heterostructure membrane. This asymmetric structure enables it to achieve the best electrical signal response. In contrast, the IL / MXene membrane prepared in Comparative Example 2 lacks a salinity gradient due to its bilaterally symmetrical structure, resulting in a lower electrical response signal. It is particularly noteworthy that when pressure acts on the MXene side of the heterostructure membrane, the reverse salinity gradient makes the electrical signal response relatively weak. The MXene membrane has the weakest electrical signal response due to its lowest electrolyte ion storage capacity and the largest transmission resistance.

[0079] In order to test the sensing performance of the sensor prepared in Example 1 at different pressures on the ionic liquid side, its IT and VT at different pressures were tested, and the results are as follows: Figure 8 a is the IT diagram of the self-powered linear pressure sensor prepared in Example 1 of the present invention at different pressures. It can be seen that as the pressure increases, the output current increases accordingly. When the pressure is 10 kPa, the output current density is 103.65 mA / m 2 . Figure 8 b is the IP diagram of the self-powered linear pressure sensor prepared in Example 1 of the present invention. It can be seen that the linearity of input pressure-output current is 0.993.

[0080] Figure 9 a is the VT diagram of the self-powered linear pressure sensor prepared in Example 1 of the present invention at different pressures. It can be seen that as the pressure increases, the output voltage increases accordingly. When the pressure is 8.3 kPa, the output voltage is 1.62 mV. Figure 9 b is the VP diagram of the self-powered linear pressure sensor prepared in Example 1 of the present invention. It can be seen that the linearity of input pressure-output voltage is 0.999.

[0081] Figure 10Figure 10a shows the response and recovery time of the current (I) of the self-powered linear pressure sensor prepared in Example 1 of the present invention. It can be seen that the sensor has an extremely fast response speed. When stimulated by an external pressure (1.2 kPa), the response time is 52 ms and the recovery time is 120 ms. Figure 10b shows the response and recovery time of the voltage (V) of the self-powered linear pressure sensor prepared in Example 1 of the present invention. It can be seen that the sensor has a relatively fast response speed. When stimulated by an external pressure (3.3 kPa), the response time is 65 ms and the recovery time is 85 ms.

[0082] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing an all-solid-state ionic liquid-MXene composite membrane self-powered linear pressure sensor, characterized in that: Here are the steps: (1) Etching the precursor MAX to obtain a MXene colloidal solution, and then filtering to obtain a MXene film; (2) The ionic liquid is added dropwise onto the MXene film, and an ionic liquid-MXene composite film with incomplete ionic liquid penetration is obtained by spin coating; (3) Placing the ionic liquid-MXene composite membrane between the double-sided porous dielectric layers to form a sandwich structure; (4) The sandwich structure is mechanically fixed using two polymer cavities. The internal configuration of the polymer cavity matches the space of the double-sided porous dielectric layer, and the outside of the polymer cavity is airtightly protected by a flexible packaging film. (5) Filling the polymer cavity with a solid gel electrolyte; placing an Ag / AgCl reference electrode in the solid gel electrolyte.

2. The method for preparing the all-solid-state ionic liquid-MXene composite membrane self-powered linear pressure sensor according to claim 1, characterized in that: The etching in step (1) refers to selectively etching the precursor MAX phase with HCl and LiF; after etching, it also includes physical assisted intercalation, multi-stage centrifugal purification and ultrasonic stripping treatment.

3. The method for preparing the all-solid-state ionic liquid-MXene composite membrane self-powered linear pressure sensor according to claim 2, characterized in that: The thickness of the MXene film in step (2) is 7.03 μm and the size is 9.6 cm 2 , add 0.8-1.2 mL of ionic liquid dropwise.

4. The method for preparing the all-solid-state ionic liquid-MXene composite membrane self-powered linear pressure sensor according to claim 3, characterized in that: The ionic liquid in step (2) is any one of 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide and 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide.

5. The method for preparing the all-solid-state ionic liquid-MXene composite membrane self-powered linear pressure sensor according to claim 4, characterized in that: In step (3), the double-sided porous dielectric layer is two polytetrafluoroethylene films with pre-reserved holes.

6. The method for preparing the all-solid-state ionic liquid-MXene composite membrane self-powered linear pressure sensor according to claim 5, characterized in that: The solid gel electrolyte in step (5) is any one of a polyacrylamide-based gel electrolyte, a polyvinyl alcohol-based gel electrolyte, a polyacrylonitrile-based gel electrolyte, a polyvinylidene fluoride-based gel electrolyte and a poly(vinylidene fluoride-co-hexafluoropropylene)-based gel electrolyte.

7. An all-solid-state ionic liquid-MXene composite membrane self-powered linear pressure sensor prepared by the preparation method according to claim 1.

8. The all-solid-state ionic liquid-MXene composite membrane self-powered linear pressure sensor according to claim 7, characterized in that: The voltage-pressure linearity of the all-solid-state ionic liquid-MXene composite membrane self-powered linear pressure sensor is 0.999, and the current-pressure linearity is 0.

993.

9. The all-solid-state ionic liquid-MXene composite membrane self-powered linear pressure sensor according to claim 7, characterized in that: The current response time is 52 ms when the pressure is 1.2 kPa, and the voltage response time is 65 ms when the pressure is 3.7 kPa.

10. Application of the all-solid-state ionic liquid-MXene composite membrane self-powered linear pressure sensor according to claim 7 in the field of medical monitoring or industrial sensing for purposes other than disease diagnosis.

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