A flexible pressure sensor based on ink / MXene composite film and its preparation method

Abstract

The present invention relates to a flexible pressure sensor based on ink / MXene composite film and a preparation method thereof. The flexible pressure sensor based on ink / MXene composite film is a two-piece structure that overlaps and opposes each other, including: a flexible substrate, a sensitive material formed on the flexible substrate, electrodes arranged at both ends of the sensitive material, wires connected to the electrodes, and a packaging layer for protecting the sensitive material; the sensitive material is an ink / MXene composite film formed by discontinuously covering the MXene layer with ink in a specific pattern; the ink pattern includes one of gradient stripes with gradient ink thickness and step stripes composed of self-stepping stripes; the ink layer thickness is 0.1 to 20 μm; the area covered by the ink pattern accounts for 10 to 90% of the MXene layer, preferably 50 to 80%.

Description

Technical Field

[0001] The present invention belongs to the technical field of pressure sensors, and in particular relates to a flexible pressure sensor based on an ink / MXene composite film and a preparation method thereof. Background Art

[0002] In recent years, flexibility has gradually become an important development trend in the field of sensors. Compared with traditional rigid devices, light, thin, and deformable flexible sensors have greater flexibility and space utilization, and have attracted widespread attention from researchers. They have great application prospects in medical diagnosis, human health monitoring, entertainment communications, and other fields. Among them, flexible pressure sensors are relatively more common due to the strong demand for pressure monitoring in various fields.

[0003] According to the sensing mechanism, flexible pressure sensors can be divided into flexible piezoelectric sensors, flexible capacitive sensors and flexible piezoresistive sensors. Among them, flexible piezoresistive sensors can convert external pressure into resistance changes, thereby achieving real-time response to external stimuli. Due to its simple device structure and excellent response performance, it is widely used in the field of pressure sensing. Generally, flexible piezoresistive sensors are composed of sensitive materials and flexible substrates. Among them, the substrate usually selects polymer materials such as PDMS and PET, which determine the flexibility of the device; and the sensitive material generally selects low-dimensional conductive materials such as metal nanoparticles, nanowires, carbon nanotubes, graphene, etc., and their morphology and physicochemical properties determine the sensing performance of the device.

[0004] For flexible piezoresistive sensors, the interface design of sensitive materials is the key to improving the performance of piezoresistive sensors. A common interface design method is to construct a flexible substrate with a special surface structure by the inverted mold method and deposit sensitive materials on its surface by means of thermal deposition (Reference 1). However, the preparation process of the inverted mold method limits the types of flexible substrates, and the microstructure design is complex; and the thermal deposition of sensitive materials and other methods have high processing costs. In addition, it is also a common method to construct sensitive materials with porous structures by the template method (Reference 2). However, the processing process of this method is complex. Therefore, developing novel sensitive material components, designing their microstructures, and exploring their convenient construction methods are of great significance for constructing low-cost, high-performance piezoresistive flexible pressure sensors.

[0005] Prior art literature:

[0006] Document 1: Yang T, Deng W, Chu X, et al. Hierarchically Microstructure-Bioinspired Flexible Piezoresistive Bioelectronics[J]. ACS Nano 2021 15(7),11555-11563;

[0007] Document 2: Min P, Li Summary of the invention

[0008] In order to solve the above problems, the purpose of the present invention is to provide a high-performance flexible pressure sensor based on ink / MXene composite film and a preparation method thereof, which has high sensitivity, wide response range and extremely low detection limit.

[0009] Specifically, in the first aspect, the present invention provides a flexible pressure sensor based on an ink / MXene composite film, wherein the pressure sensor is a two-piece structure that overlaps and opposes each other, and comprises: a flexible substrate, a sensitive material formed on the flexible substrate, electrodes arranged at both ends of the sensitive material, wires connected to the electrodes, and a packaging layer for protecting the sensitive material;

[0010] The sensitive material is an ink / MXene composite film formed by discontinuously covering the MXene layer with ink in a specific pattern; the ink pattern includes one of gradient stripes with gradient ink thickness and step stripes composed of self-stepping stripes;

[0011] The ink layer has a thickness of 0.1 to 20 μm; the area covered by the ink pattern accounts for 10 to 90% of the MXene layer, preferably 50 to 80%.

[0012] Preferably, the flexible substrate is in the form of a film or fabric, with a length and width both greater than 5 mm and a thickness of 0.05 to 1 mm; the material of the flexible substrate is one of polyurethane, polyacrylate, silicone rubber, polydimethylsiloxane PDMS, polyimide, polyethylene terephthalate, polyethylene terephthalate, polyethylene PE, polyvinyl chloride, polypropylene, pure cotton cloth, double-sided tape, or biofiber; preferably one of polydimethylsiloxane, polyethylene, pure cotton cloth, or double-sided tape.

[0013] Preferably, the chemical formula of the MXene is M n+1 X n ; wherein n=1-4, M is a transition metal element, and X is a carbon and / or nitrogen element; the surface of the MXene layer in the composite film contains end groups, and the end groups include at least one of -F, -OH, and -O; the thickness of the MXene layer is 1-50 μm, preferably 2-10 μm, and the Zeta potential is -10 to -50 mV, preferably -30 to -50 mV.

[0014] Preferably, the encapsulation layer has a length and a width both greater than 5 mm and a thickness of 0.005 to 1 mm; the material of the encapsulation layer is selected from one of polyurethane, polyacrylate, silicone rubber, polydimethylsiloxane, polyimide, polyethylene terephthalate, polyethylene glycol terephthalate, polyethylene, polyvinyl chloride, polypropylene, pure cotton cloth, polypropylene transparent tape or biofiber; preferably, the material of the encapsulation layer is one of polydimethylsiloxane, polyethylene, pure cotton cloth, or polypropylene transparent tape.

[0015] In a second aspect, the present invention provides a method for preparing the above-mentioned flexible pressure sensor based on ink / MXene composite film, comprising:

[0016] The MAX phase powder material was added into a mixed solution of hydrochloric acid and lithium fluoride, and after etching, centrifugal separation was performed to obtain a multilayer MAX n+1 X n Powder; multi-layer M n+1 X n The powder is dissolved, centrifuged, and dried to obtain MXene powder; the MXene powder is redissolved, ultrasonicated, and vortexed to obtain a MXene dispersion;

[0017] Drawing an ink pattern on a film-forming substrate to obtain a surface-patterned ink / film-forming substrate;

[0018] Coating the MXene dispersion on the surface of the ink / film-forming substrate with a patterned surface, and drying to obtain an ink / MXene composite film;

[0019] The ink / MXene composite film is fixed on a flexible substrate, electrodes and wires are constructed to obtain a single ink / MXene / flexible substrate composite film, and two composite films are overlapped and packaged up and down to obtain the flexible pressure sensor based on the ink / MXene composite film.

[0020] Preferably, the molar ratio of the hydrochloric acid, lithium fluoride and MAX phase powder is (40-120): (10-30): (0.5-2); the concentration of the MXene dispersion is 1-50 mg / mL, preferably 10-50 mg / mL.

[0021] Preferably, the ink comprises one of commercial marker ink, commercial pencil ink, commercial gel pen ink, or commercial fluorescent pen ink; and there is a difference in Zeta potential between the ink and the MXene nanosheets.

[0022] Preferably, the film-forming substrate comprises one of commercial semi-hydrophobic paper, commercial mixed cellulose filter membrane, polydimethylsiloxane (PDMS), or glass.

[0023] Preferably, the coating amount of the MXene dispersion is 0.05 to 1 mL / cm 2 .

[0024] Preferably, after coating the MXene dispersion, the coating is dried at 15-35° C. and normal pressure.

[0025] Beneficial Effects

[0026] (1) Material advantages: The sensitive material MXene used in the present invention has excellent conductivity and good mechanical properties; the raw materials of materials such as ink and flexible substrate are easily available, the material selection is wide, and the biocompatibility is good. At the same time, the preparation method of the composite film is simple and efficient, low in cost, and easy to mass produce;

[0027] (2) Structural advantages: The present invention can combine the effective isolation effect brought by thicker ink and the larger effective sensing area retained by thinner ink by designing the thickness, width and structure of the ink stripes on the surface of the composite film, and make the surface resistance of the corresponding area of ​​the composite film present a corresponding consistent or periodic change, so that the sensor device exhibits a more controllable electrical signal change when under pressure, thereby achieving a coordinated improvement in sensitivity and response range;

[0028] (3) Performance advantages: The device constructed by the present invention has excellent performance and high sensitivity (413 kPa -1 ), a wider response range (0-105kPa), a lower detection limit (0.29Pa) and a shorter response time (50ms). It has a wide range of applications and is expected to be used in many fields such as health monitoring, motion monitoring and human-computer interaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic diagram of the structure of a flexible pressure sensor based on ink / MXene composite film provided by the present invention;

[0030] Figure 2 Schematic diagram of the surface resistance of ink / MXene composite films with different ink coating times;

[0031] Figure 3 The ink / Ti3C2T prepared in Example 1 x Surface SEM image of the composite film;

[0032] Figure 4 The ink / Ti3C2T prepared in Comparative Example 1 x Surface / cross-section SEM images of the composite film;

[0033] Figure 5 It is a sensor signal output curve diagram of the flexible pressure sensor prepared in Example 1 and Comparative Example 1;

[0034] Figure 6 It is a sensor signal output curve diagram of the flexible pressure sensor prepared in Comparative Example 2 and Comparative Example 3;

[0035] Figure 7 is a sensor signal output curve diagram of the flexible pressure sensor prepared in Comparative Example 4;

[0036] Reference numerals:

[0037] 1-ink; 2-MXene; 3-flexible substrate; 4-conducting wire. DETAILED DESCRIPTION

[0038] The present invention is further described below by way of embodiments. It should be understood that the following embodiments are only used to illustrate the present invention, but not to limit the present invention.

[0039] The present invention uses ink / MXene composite film as the sensitive material and designs the surface structure of the ink / MXene composite film to achieve the construction of a flexible pressure sensor with high sensitivity and a wide response range.

[0040] Figure 1 The schematic diagram of the structure of the flexible pressure sensor based on the ink / MXene composite film provided by the present invention is shown. The flexible pressure sensor based on the ink / MXene composite film is a two-piece structure that overlaps and faces each other. The flexible pressure sensor includes: a flexible substrate, a sensitive material formed on the flexible substrate, electrodes arranged at both ends of the sensitive material, wires connected to the electrodes, and a packaging layer for protecting the sensitive material.

[0041] The flexible substrate is a flexible material that can withstand large deformation and achieve good adhesion with various structures. In some embodiments, the flexible substrate can be in the form of a film or fabric, with a length and width greater than 5 mm and a thickness of 0.05 to 1 mm.

[0042] Preferably, the material of the flexible substrate can be one of polyurethane, polyacrylate, silicone rubber, polydimethylsiloxane PDMS, polyimide, polyethylene terephthalate, polyethylene glycol terephthalate, polyethylene PE, polyvinyl chloride, polypropylene, pure cotton cloth, double-sided tape, or biofiber; more preferably one of polydimethylsiloxane, polyethylene, pure cotton cloth, or double-sided tape.

[0043] The sensitive material is an ink / MXene composite film formed by discontinuously covering the MXene layer with ink in a specific pattern, which is used to sense external stimuli and realize the conversion of pressure signals into electrical signals. The ink / MXene composite film can be prepared by in-situ transfer printing of ink on the MXene layer. The flexible substrate is used to provide support for the sensitive material; the electrodes and wires are used to collect electrical signals, and the electrodes are located at both ends of the sensitive material for leading out the wires, which are used to connect the sensor to the data collector; the encapsulation layer is used to isolate the sensitive material from the external environment and protect the sensitive material, thereby extending the life of the sensor.

[0044] The pressure sensor adopts a two-piece structure that overlaps and opposes each other. The conductive path between the upper and lower layers of ink / MXene composite film sensitive materials is limited by the ink layer located on the surface. When the sensor is subjected to external pressure, the contact area of ​​the two composite films increases, the conductive path increases, and the current increases, thereby achieving real-time response to external stimuli. By designing the surface structure of the ink / MXene composite film, the changes in the conductive path during the pressure process can be regulated, and then the sensing performance such as sensitivity, response range, response time and linearity can be regulated.

[0045] The chemical formula of the MXene is M n+1 X n ; wherein n=1-4, M is a transition metal element, and X is carbon and / or nitrogen. The surface of the MXene layer in the composite film contains end groups, and the end groups include at least one of -F, -OH, and -O. The Zeta potential of the MXene layer is -10 to -50 mV, preferably -30 to -50 mV.

[0046] In some embodiments, the ink / MXene composite film can be set to a rectangular shape, with a length of 0.3 to 10 cm, a width of 0.1 to 10 cm, and a thickness of 1 μm or more; preferably, the thickness of the MXene layer in the composite film is 1-50 μm, preferably 2-10 μm, and the thickness of the ink layer is 0.1-20 μm. Among them, the lateral size of the MXene nanosheet particles constituting the MXene layer is 0.05-5 μm, preferably 0.5-5 μm; the thickness is 0.8-80 nm, preferably 0.8-3 nm.

[0047] The surface of the ink / MXene composite film shows that the ink is discontinuously covered on the MXene layer in a specific pattern. The surface of the non-ink area of ​​the composite film contains only MXene, and the microstructure of the film-forming substrate surface is completely replicated; while the surface of the ink area also replicates the microstructure of the substrate, but due to the existence of the microstructure and the deformation of the substrate during the drop coating process, the thickness of the ink is unevenly distributed, and the thinner ink breaks, and some obvious cracks appear, exposing the bottom MXene layer.

[0048] Preferably, the area covered by the ink pattern can be controlled to account for 10-90% of the MXene layer, preferably 50-80%. Under the condition of appropriate area ratio of the ink pattern, the surface resistance of the ink / MXene composite film can be effectively regulated, and the pressure sensor can show a wider resistance change range during the pressure process, thereby achieving higher sensitivity. When the area ratio of the ink area is relatively small, the surface resistance of the composite film is small, so the initial resistance of the prepared pressure sensor is also small, and its variable resistance range after pressure is also small, that is, compared with the ink / MXene composite film-based pressure sensor with a suitable ink area ratio, its resistance changes relatively less when subjected to the same pressure, and its sensitivity is also lower. In contrast, when the area ratio of the ink area is large, the surface resistance of the composite film is large, so the initial resistance of the prepared pressure sensor is large, and the resistance is still large when subjected to extreme pressure, and the variable resistance range is also small, that is, compared with the appropriate ink area ratio, its resistance changes relatively less when subjected to the same pressure, and its sensitivity is also lower.

[0049] By regulating the thickness of the ink layer, the surface resistance of the composite film can be regulated, thereby achieving the regulation of the performance of the flexible pressure sensor. Preferably, the thickness of the ink layer is 0.1-20 μm. Specifically, the conductive network on the surface of the MXene film can be regulated by controlling the number of ink coatings. When only 2 layers are applied, the ink thickness is about 0.1-3 μm. Due to the unevenness of the fibers on the substrate surface, the ink can only cover the protruding fiber area, and some grooves are still not filled. Therefore, after transfer, there are still a large number of ink-free areas on the MXene surface, and the resistance only increases by one order of magnitude, about tens of ohms. When 4 layers are applied, the ink has basically completely covered the fiber structure on the surface of the substrate, with a thickness of about 1-6 μm. During transfer, the stress concentration caused by the deformation of the substrate causes the ink to break in the thinner area. Therefore, after transfer, only the ink crack area on the MXene surface has MXene exposed, and the resistance is greatly increased, about hundreds of ohms. The huge difference in surface resistance between ink / MXene composite films with different ink thicknesses makes it possible to design a highly sensitive pressure sensor similar to a sliding rheostat. Figure 2 Schematic diagram of the surface resistance of ink / MXene composite films with different ink coating times (i.e. different ink thicknesses).

[0050] By designing the structure of the ink pattern in a specific way, such as a gradient stripe structure with a gradient change in ink thickness and a step stripe structure composed of self-stepped stripes, the sensitivity and response range of the sensor can be improved at the same time, preferably a gradient stripe structure with a gradient change in ink thickness. The structure of the ink layer is a stripe structure with a periodic change in thickness, and the surface resistance of the ink area shows a corresponding periodic change, and has both a larger initial resistance brought by thicker ink and a smaller final resistance retained by thinner ink after being compressed, so that the sensor device shows a wider range of electrical signal changes when under pressure, thereby achieving a coordinated improvement in sensitivity and response range.

[0051] In the present invention, the sensing mechanism of the flexible pressure sensor based on the ink / MXene composite film is as follows: when there is no external pressure, the ink / MXene composite film is separated by the ink pattern, and only a small amount of MXene sheets exposed on the ink surface are connected, so the conductive network has fewer connections, the conductivity is extremely low and the resistance is extremely large, so the initial current is extremely small; as the pressure increases, the composite film is deformed under pressure, and more MXene sheets are in contact, which increases the conductive network and greatly increases the current; until the blank areas of the MXene sheets (i.e., the stripe spacing areas not covered by ink) are all in contact, the conductive network is enhanced by reducing the inter-sheet spacing inside the film, so that the current continues to increase, thereby expanding the sensing range of the device.

[0052] Parameters such as the width and thickness of the ink stripes, the area ratio of the ink area, and the structure have a great influence on the performance of the sensor. When the ink thickness is appropriate and its thickness variation is reasonably designed, the distribution of the conductive network on the film surface can be regulated, so that the contact resistance of the sensitive material can be controlled to change when the device is under pressure, thereby achieving excellent sensitivity and a wide response range. When the ink thickness is too low or the width is too small, the presence of a small amount of ink cannot effectively isolate the sensitive material MXene, which is not conducive to the construction of a high-sensitivity pressure sensor; when the ink thickness is too thick or the width is too wide, the non-conductive ink layer will completely insulate the ink area where it is located, reducing the effective sensing area of ​​the flexible pressure sensor and greatly reducing its sensitivity; at the same time, the overly thick ink layer has poor mechanical pressure bearing capacity and is easier to break, thus limiting the response range of the sensor. By structurally designing the ink, for example, making the thickness of the ink stripes change in a gradient (referred to as a gradient stripe structure) or making the thickness of each ink stripe change in a step-like manner, it is possible to have both the effective isolation effect brought by the thicker ink and the larger effective sensing area retained by the thinner ink, and to make the surface resistance of the corresponding area of ​​the composite film show corresponding consistent or periodic changes, so that the sensor device exhibits more controllable electrical signal changes when under pressure, thereby achieving a coordinated improvement in sensitivity and response range.

[0053] The electrode is a conductive material, and the sensor is connected to the data acquisition device through the wire led out of the electrode. In some embodiments, the material of the electrode can be one of conductive ink, conductive silver paste, or conductive carbon black; the wire can be one of a metal wire and a conductive fiber, and the length of the wire is greater than 2 cm and the diameter is 0.1-1 mm.

[0054] The encapsulation layer is an insulating flexible material, such as a dense insulating film, which can be tightly combined with the flexible substrate and completely cover the two-piece flexible pressure sensor, effectively transmit external pressure and other stimuli, and can effectively isolate sensitive materials from the external environment to protect sensitive materials.

[0055] In some embodiments, the encapsulation layer may be set to have a length and width greater than 5 mm and a thickness of 0.005 to 1 mm. Preferably, the material of the encapsulation layer may be selected from one of polyurethane, polyacrylate, silicone rubber, polydimethylsiloxane, polyimide, polyethylene terephthalate, polyethylene glycol terephthalate, polyethylene, polyvinyl chloride, polypropylene, pure cotton cloth, polypropylene transparent tape or biofiber; more preferably, the material of the encapsulation layer is one of polydimethylsiloxane, polyethylene, pure cotton cloth or polypropylene transparent tape.

[0056] The flexible pressure sensor based on ink / MXene composite film provided by the present invention can achieve real-time electrical signal response in a wide pressure range. The response range of the flexible pressure sensor is 0-105kPa, and the maximum sensitivity can reach 413kPa. -1 , the minimum detection limit can reach 0.29Pa.

[0057] The following is an exemplary description of a method for preparing a two-piece flexible pressure sensor based on an ink / MXene composite film provided by the present invention, and the preparation method mainly includes the following steps.

[0058] (1) Preparation of MXene dispersion. Add MAX phase powder material to a mixed solution of hydrochloric acid and lithium fluoride, and control the molar ratio of hydrochloric acid, lithium fluoride and MAX phase powder to be (40-120): (10-30): (0.5-2), and etch in an oil bath at 30-60°C for 6-48 hours. After the reaction is completed, centrifuge and wash the sample 1-8 times, the centrifugal speed is 3000-8000rpm, the centrifugal time is 3-10 minutes each time, and the deionized water used for each washing is 200-2000mL; after the pH of the centrifugal supernatant is greater than 6, freeze-dry the obtained precipitate at -60--15°C for 6-48 hours to obtain a multilayer MXene dispersion. n+1 X n Powder; Subsequently, the multilayer M n+1 X n The powder is dispersed in an appropriate amount of deionized water or distilled water or other solvents, and the multilayer M n+1 X n The mass ratio of powder to deionized water or distilled water is (0.25-1): (25-250), and argon gas is passed through an ice bath for ultrasonic treatment at 60-120W for 15 to 180 minutes, followed by centrifugation at a speed of 2000 to 4000 rpm for 15 to 120 minutes; the obtained supernatant is freeze-dried at -60 to -15°C for 12 to 72 hours to obtain the MXene powder; the MXene powder is redispersed in a solvent such as deionized water, ultrasonically and vortexed to obtain the MXene dispersion.

[0059] In some embodiments, the concentration of the MXene dispersion can be controlled to be 1 to 50 mg / mL, preferably 10 to 50 mg / mL. When the solution concentration is too low, it is difficult to form a film when constructing a MXene film by a drop coating method, a spray coating method, etc., or the film cannot be self-supporting; a suitable MXene solution concentration is conducive to the construction of a self-supporting film and the improvement of its mechanical properties.

[0060] (2) Preparation of surface patterned ink / film-forming substrate: A specific ink pattern is drawn on a film-forming substrate, and the ink is allowed to stand to fully dry, thereby obtaining the surface patterned ink / film-forming substrate.

[0061] The ink is a dried product of commercial oil-based ink, water-based ink or other inks, and there is a certain zeta potential difference between the ink and the MXene nanosheets, so that electrostatic adsorption can be achieved. Preferably, the ink can be one of commercial marker ink, commercial pencil ink, commercial gel pen ink, or commercial fluorescent pen ink.

[0062] The film-forming substrate can be selected from commercial semi-hydrophobic paper, commercial mixed cellulose filter membrane, polydimethylsiloxane PDMS, or glass; the drawing method can be selected from hand-painting, drip coating, spin coating, spraying or scraping; the ink pattern can be a stripe pattern; the drying method can be selected from natural drying at room temperature.

[0063] In one example, a stripe pattern with uniform width and spacing is hand-painted on commercial semi-hydrophobic paper using a commercial marker pen to obtain a film-forming substrate with uniform ink stripes. The ink may have a width of 0.1 to 3 mm, a spacing of 0.1 to 1 mm, and a thickness of 0.1 to 10 um.

[0064] The ink pattern can be realized by changing the width of the ink and the number of times the ink is written. The width and thickness of a single writing with a signature pen are recorded as unit width and unit thickness; preferably, the ink pattern is one of gradient stripes with a gradient change in ink thickness and step stripes composed of self-stepped stripes.

[0065] (3) Ink / MXene composite film construction. The MXene dispersion prepared in step (1) is coated on the surface-patterned ink / film-forming substrate prepared in step (2) and dried to form a film, and the film is peeled off to obtain a surface-patterned ink / MXene composite film. The film-forming substrate has a high surface electronegativity and has little interaction with the MXene nanosheets, so that the ink / MXene composite film obtained after the MXene film is dried can be easily peeled off from the film-forming substrate.

[0066] During the ink / MXene composite film construction process, the MXene dispersion can be coated by spraying or dripping or by casting, and the coating amount can be 0.05-1 mL / cm 2 , dried to form film at 15-35℃ and normal pressure.

[0067] In one example, a Ti3C2T x Dispersion liquid according to 0.1~1mL / cm 2 The amount of ink was dropped onto the film-forming substrate with consistent ink stripes, dried under room temperature and normal pressure, and the film was peeled off to obtain ink / Ti3C2T with consistent ink stripes. xComposite film.

[0068] The surface structure of the ink / MXene composite film can be controlled by adjusting the ink thickness, width and film-forming substrate, thereby controlling the surface resistance of the composite film and the performance of the flexible pressure sensor.

[0069] In the present invention, the preparation mechanism of the ink / MXene composite film is as follows: during the drop coating process, the film-forming substrate is infiltrated by the MXene solution and deforms to a certain extent, thereby forming stress concentration on the surface of the rigid ink, causing it to break and exposing the bottom film-forming substrate. At the same time, due to the generation of cracks, the bonding force between the ink and the substrate is also reduced. In the early stage of drying, the water molecules in the MXene solution evaporate, and the MXene sheets accumulate near the liquid-solid and liquid-gas interfaces. At the same time, the water molecules carry the bottom MXene sheets into the gaps of the ink to achieve comprehensive coverage of the ink. Subsequently, the MXene sheets with negative charges on the surface are initially assembled in the gel-like gel formed after a large amount of water molecules evaporate, and the ink imprint with a smaller bonding force with the substrate is adsorbed to the bottom of the MXene gel-like gel due to the effect of electrostatic adsorption. Subsequently, the residual water molecules in the gel-like gel are completely evaporated, and the capillary force further enhances the bonding between the sheets. Due to the disappearance of water, the bonding force between the MXene film and the substrate is reduced, so that a surface patterned and self-supporting ink / MXene composite film is obtained.

[0070] The composite film prepared by the present invention is realized by the electrostatic adsorption between MXene and ink. The main components of the ink are colorants (i.e., pigments and / or dyes) and binders (solvents and fillers). The MXene sheets themselves are electronegative and have low Zeta potential. There is a large Zeta potential difference between the colorants and the MXene nanosheets. When an ink having a large difference in Zeta potential from the MXene nanosheet is coated on the film-forming substrate, during the drying process of the MXene solution, the MXene sheet will electrostatically adsorb the ink in situ, and finally the imprint of the ink will be in situ rubbing onto the MXene film, and finally the ink / MXene composite film in which the ink is coated on the surface of the MXene film in a specific pattern is obtained.

[0071] (4) Preparation of flexible pressure sensor based on ink / MXene composite film. The ink / MXene composite film prepared in step (3) is fixed on a flexible substrate, and the ink surface is exposed to the outside to form a sensitive material; an electrode is constructed at one end of the sensitive material and a wire is led out to obtain a single ink / MXene / flexible substrate composite film; the two composite films are overlapped up and down to make the sensitive materials contact each other and avoid direct connection between the electrodes; and an insulating packaging layer is used for packaging to obtain a two-piece flexible pressure sensor based on the ink / MXene composite film.

[0072] In some embodiments, the ink / MXene composite film and the flexible substrate may be fixed by curing, cross-linking or pasting. The flexible substrate may be made of pure cotton cloth, polydimethylsiloxane (PDMS) or polyethylene terephthalate film. The electrode may be made of conductive silver paste. The conductor may be made of copper wire. The encapsulation layer may be made of polypropylene transparent tape.

[0073] In one example, the monomer and curing agent of PDMS are mixed and poured into a mold for curing. The ratio of monomer to curing agent is controlled to be 10:1, the curing temperature is 80°C, and the curing time is 60 minutes. A flexible substrate PDMS film with a thickness of 0.1-1 mm can be obtained.

[0074] According to the electrostatic adsorption effect, the present invention transfers the commercial ink in situ to the surface of the MXene film by dripping and spraying, etc., and uses the ink / MXene composite film as the sensitive material. After compounding with a flexible substrate and adding electrodes, a highly sensitive two-piece flexible pressure sensor based on the ink / MXene composite film is constructed. By designing the ink structure on the surface of the film, the conductive network on the surface of the ink / MXene composite film can be regulated, and the sensitivity, response range, linearity and other sensing properties of the two-piece flexible pressure sensor can be improved. When the flexible pressure sensor is subjected to external pressure, the contact sites of the conductive network on the surface of the film increase and the resistance decreases, thereby realizing real-time electrical signal response to external stimuli, and then realizing real-time monitoring of external pressure. The flexible pressure sensor provided by the present invention is expected to be applied to the real-time monitoring of weak physiological signals and movements of the human body and the analysis of material texture.

[0075] The present invention can achieve regulation of the sensitivity, response range and linearity of the flexible pressure sensor by regulating the ink thickness / width on the surface of the ink / MXene composite film.

[0076] The sensing performance testing method of the flexible pressure sensor based on the ink / MXene composite film provided by the present invention is as follows: Place the flexible pressure sensor flat on a pressure testing platform, and connect the sensor to an electrochemical workstation via a wire. Move the pressure head of the pressure testing platform to the surface of the sensor so that the sensor is in a critical state of zero pressure. By controlling the displacement of the pressure head of the pressure testing platform, the pressure on the sensor is gradually increased, and the pressure P on the sensor and the corresponding current change ΔI are recorded by the pressure sensor of the pressure testing platform and the electrochemical workstation. According to the sensitivity formula The sensitivity of the pressure sensor is obtained.

[0077] The following examples are further cited to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention belong to the scope of protection of the present invention, and the specific process parameters of the following examples are only an example within the appropriate range.

[0078] Example 1

[0079] (1) Ti3C2T x Preparation of dispersion. Take 3g (0.12mol) of lithium fluoride and dissolve it in 67mL of 9M HCl solution. After stirring evenly, weigh 3g (0.015mol) of Ti3AlC2 powder and slowly add it to the above solution. Stir evenly at room temperature. Seal the beaker and transfer it to an oil bath. Control the reaction temperature and time to be 30°C and 24h, respectively. After the reaction is completed, centrifuge and wash with deionized water several times. The centrifugation condition is 3000rpm and the centrifugation time is 5min each time. After the pH of the centrifuged supernatant is greater than 6, freeze-dry the precipitate to obtain multilayer Ti3C2 powder. Disperse 1g of the obtained powder in 50mL of deionized water, pass argon gas and perform ice bath ultrasound for 2h with an ultrasonic power of 100W. After the ultrasound is completed, centrifuge the dispersion at 2000rpm for 1h. Freeze-dry the supernatant obtained by centrifugation for 24h to obtain Ti3C2T x Powder. 150 mg of the obtained powder was dispersed in 15 mL of deionized water, ultrasonicated at 100 W for 5 min, and vortexed for 5 min to obtain a uniformly dispersed Ti3C2T x Solution.

[0080] (2) Preparation of surface patterned ink / film-forming substrate. A stripe pattern with uniform width and spacing was hand-painted on commercial semi-hydrophobic paper using a commercial marker pen, wherein the ink width was 0.8 mm and the spacing was 0.2 mm. The number of times each stripe was painted was inconsistent, and the number of times was determined according to the rule of "…-2-4-6-4-2-4-6-…" so that the thickness of each stripe varied in a gradient, thereby obtaining a paper-based film-forming substrate with stripes with gradient ink thickness variations.

[0081] (3) Ink / Ti3C2T x Composite film construction. 3mL Ti3C2T x The solution was 0.17 mL / cm 2 The amount of ink was dripped onto a paper-based film-forming substrate with stripes with a gradient change in ink thickness, dried under room temperature and atmospheric pressure, and the film was carefully peeled off to obtain an ink / Ti3C2T x Composite film.

[0082] (4) Based on ink / Ti3C2T x Preparation of flexible pressure sensor based on composite film. x The composite film was pasted on a polyethylene terephthalate (PET) substrate with double-sided tape, a wire was fixed at one end and a conductive silver paste was added to construct an electrode. After standing for 1 hour, a single-sheet ink / Ti3C2T x / PET composite film; after overlapping the two composite films and sealing them with transparent adhesive, the ink / Ti3C2T based x / PET composite film flexible pressure sensor.

[0083] In the flexible pressure sensor prepared in this embodiment, the area covered by the ink pattern accounts for 80% of the MXene layer, and the thickness of the ink layer is 0.1-10 μm.

[0084] Example 2

[0085] (1) Ti3C2T x Preparation of dispersion. Take 4.5g (0.17mol) of lithium fluoride and dissolve it in 60mL of 9M HCl solution. After stirring evenly, weigh 3g (0.015mol) of Ti3AlC2 powder and slowly add it to the above solution. After stirring evenly at room temperature, seal the beaker and transfer it to an oil bath pot. Control the reaction temperature and time to be 35°C and 6h, respectively. After the reaction is completed, centrifuge and wash with deionized water several times. The centrifugation condition is 8000rpm, and the centrifugation time is 10min each time. After the pH of the centrifuged supernatant is greater than 6, freeze-dry the precipitate to obtain multilayer Ti3C2 powder. Disperse 1g of the obtained powder in 100mL of deionized water, pass argon gas for ice bath ultrasound for 0.5h, and the ultrasonic power is 100W. After the ultrasound is completed, centrifuge the dispersion at 3000rpm for 0.5h. Freeze-dry the supernatant obtained by centrifugation for 72h to obtain Ti3C2T x Powder. Disperse 300 mg of the obtained powder into 15 mL of deionized water and shake by hand for 10 min to obtain a uniformly dispersed Ti3C2T x Solution.

[0086] Steps (2)-(4) are as in Example 1.

[0087] In the flexible pressure sensor prepared in this embodiment, the area covered by the ink pattern accounts for 80% of the MXene layer, and the thickness of the ink layer is 0.1-10 μm.

[0088] Example 3

[0089] Step (1) refers to Example 1.

[0090] (2) Preparation of surface patterned ink / film-forming substrate. A commercial fluorescent pen was used to hand-paint stripe patterns with uniform width and spacing on commercial semi-hydrophobic paper, wherein the ink width was 0.8 mm and the spacing was 0.2 mm. The number of times each stripe was painted was inconsistent, and the number of times was determined according to the rule of "…-2-4-6-4-2-4-6-…" so that the thickness of each stripe varied in a gradient, thereby obtaining a paper-based film-forming substrate with stripes with gradient ink thickness variations.

[0091] Steps (3)-(4) refer to Example 1.

[0092] In the flexible pressure sensor prepared in this embodiment, the area covered by the ink pattern accounts for 80% of the MXene layer, and the thickness of the ink layer is 0.1-10 μm.

[0093] Example 4

[0094] Step (1) refers to Example 1.

[0095] (2) Preparation of surface patterned ink / film-forming substrate. A stripe pattern with uniform width and spacing was hand-painted on commercial semi-hydrophobic paper using a commercial pencil, wherein the ink width was 0.8 mm and the spacing was 0.2 mm. The number of times each stripe was painted was inconsistent, and the number of times was determined according to the rule of "…-2-4-6-4-2-4-6-…" so that the thickness of each stripe varied in a gradient, thereby obtaining a paper-based film-forming substrate with stripes with gradient ink thickness variations.

[0096] Steps (3)-(4) refer to Example 1.

[0097] In the flexible pressure sensor prepared in this embodiment, the area covered by the ink pattern accounts for 80% of the MXene layer, and the thickness of the ink layer is 0.1-10 μm.

[0098] Example 5

[0099] Step (1) refers to Example 1.

[0100] (2) Preparation of surface patterned ink / film-forming substrate. A commercial gel pen was used to hand-paint stripe patterns with uniform width and spacing on commercial semi-hydrophobic paper, wherein the ink width was 0.3 mm and the spacing was 0.1 mm. The number of times each stripe was painted was inconsistent, and the number of times was determined according to the rule of "…-2-4-6-4-2-4-6-…" so that the thickness of each stripe varied in a gradient, thereby obtaining a paper-based film-forming substrate with stripes with gradient ink thickness variations.

[0101] Steps (3)-(4) refer to Example 1.

[0102] In the flexible pressure sensor prepared in this embodiment, the area covered by the ink pattern accounts for 80% of the MXene layer, and the thickness of the ink layer is 0.1-10 μm.

[0103] Example 6

[0104] Step (1) refers to Example 1.

[0105] (2) Preparation of surface patterned ink / film-forming substrate. A commercial marker pen was used to hand-paint stripe patterns with uniform width and spacing on commercial mixed cellulose filter paper, wherein the ink width was 0.8 mm and the spacing was 0.2 mm. The number of times each stripe was painted was inconsistent, and the number of times was determined according to the rule of "…-2-4-6-4-2-4-6-…" so that the thickness of each stripe varied in a gradient, thereby obtaining a filter paper-based film-forming substrate with stripes with gradient ink thickness variations.

[0106] (3) Ink / Ti3C2T x Composite film construction. 1.5mL Ti3C2T x The solution was 0.17 mL / cm 2 The amount of ink / Ti3C2T2O3 was dropped onto the filter paper-based film-forming substrate with stripes with ink thickness gradient changes, dried under room temperature and normal pressure, and the film was carefully peeled off to obtain the ink / Ti3C2T2O3 with stripes with ink thickness gradient changes. x Composite film.

[0107] Step (4) refers to Example 1.

[0108] In the flexible pressure sensor prepared in this embodiment, the area covered by the ink pattern accounts for 80% of the MXene layer, and the thickness of the ink layer is 0.1-10 μm.

[0109] Example 7

[0110] Step (1) refers to Example 1.

[0111] (2) Preparation of surface patterned ink / film-forming substrate. A stripe pattern with uniform width and spacing was hand-painted on a glass substrate using a commercial marker pen, wherein the ink width was 0.8 mm and the spacing was 0.2 mm. The number of times each stripe was painted was inconsistent, and the number of times was determined according to the rule of "…-2-4-6-4-2-4-6-…" so that the thickness of each stripe varied in a gradient, thereby obtaining a glass substrate with stripes with gradient ink thickness.

[0112] (3) Ink / Ti3C2T x Composite film construction. 1.5mL Ti3C2T x The solution was 0.33 mL / cm 2The amount of ink stripes with ink thickness gradient changes was dropped onto a glass substrate, dried at room temperature and pressure, and the film was carefully peeled off to obtain ink stripes with ink thickness gradient changes. x Composite film.

[0113] Step (4) refers to Example 1.

[0114] In the flexible pressure sensor prepared in this embodiment, the area covered by the ink pattern accounts for 80% of the MXene layer, and the thickness of the ink layer is 0.1-10 μm.

[0115] Example 8

[0116] Step (1) refers to Example 1.

[0117] (2) Preparation of surface patterned ink / film substrate. PDMS monomer and curing agent were mixed in a ratio of 10:1, and magnetic stirring was performed for 1 hour to make them evenly mixed. The mixed solution was then poured into a mold and placed in a vacuum oven. The mixture was placed in a vacuum oven at room temperature for 1 hour to exhaust all bubbles in the solution. The mixture was then placed at 80°C for 1 hour to solidify, thereby obtaining a PDMS film substrate.

[0118] Use a commercial marker pen to hand-draw a stripe pattern with consistent width and spacing on the PDMS film, where the ink width is 0.8 mm and the spacing is 0.2 mm. The number of times each stripe is painted is inconsistent, and the number of times is determined according to the rule of "...-2-4-6-4-2-4-6-..." so that the thickness of each stripe varies gradiently, thereby obtaining a PDMS-based film-forming substrate with stripes with gradient varying ink thickness.

[0119] (3) Ink / Ti3C2T x Composite film construction. 3mL Ti3C2T x The solution was 0.17 mL / cm 2 The amount of ink was dropped onto the PDMS-based film-forming substrate with stripes with gradient ink thickness, dried at room temperature and pressure, and the film was carefully peeled off to obtain the ink / Ti3C2T with stripes with gradient ink thickness. x Composite film.

[0120] Step (4) refers to Example 1.

[0121] In the flexible pressure sensor prepared in this embodiment, the area covered by the ink pattern accounts for 80% of the MXene layer, and the thickness of the ink layer is 0.1-10 μm.

[0122] Example 9

[0123] Step (1) refers to Example 1.

[0124] (2) Preparation of surface patterned ink / film-forming substrate. A commercial marker pen was used to hand-draw a stripe pattern with a uniform structure and spacing on commercial semi-hydrophobic paper, where the cross-sectional structure of the ink resembled a "convex" shape, and each stripe consisted of 5 layers of ink with inconsistent widths. The ink widths from top to bottom were "2.7-2.3-1.9-1.5-1" mm, with a spacing of 0.3 mm, so that the cross-section of each stripe was stepped, thus obtaining a paper-based film-forming substrate with self-formed stepped ink stripes.

[0125] Steps (3)-(4) refer to Example 1.

[0126] In the flexible pressure sensor prepared in this embodiment, the area covered by the ink pattern accounts for 90% of the MXene layer, and the thickness of the ink layer is 0.1-8 μm.

[0127] Example 10

[0128] Steps (1)-(3) refer to Example 1.

[0129] (4) Based on ink / Ti3C2T x Preparation of flexible pressure sensor based on composite film. x The composite film was glued to a polyethylene (PE) substrate, a wire was fixed at one end and a conductive silver paste was added to construct an electrode. After standing for 1 hour, a single-sheet ink / Ti3C2T x / PE composite film; the two composite films are overlapped and sealed with transparent adhesive to obtain the ink / Ti3C2T x / PE composite film flexible pressure sensor.

[0130] Embodiment 11

[0131] Steps (1)-(3) refer to Example 1.

[0132] (4) Based on ink / Ti3C2T x Preparation of flexible pressure sensor based on composite film. x The composite film was pasted on a pure cotton cloth substrate with silica gel, a wire was fixed at one end and a conductive silver paste was added to construct an electrode. After standing for 1 hour, a single-sheet ink / Ti3C2T x / cotton cloth composite film; overlap the two composite films and sew them together with needle and thread to obtain ink / Ti3C2T x Flexible pressure sensor based on / cotton cloth composite film.

[0133] Comparative Example 1

[0134] Step (1) refers to Example 1.

[0135] (2) Pure Ti3C2Tx Thin film preparation. 3 mL Ti3C2T x The solution was 0.33 mL / cm 2 The amount of the film was dropped onto a commercial semi-hydrophobic paper-based film substrate, dried at room temperature and atmospheric pressure, and the film was carefully peeled off to obtain pure Ti3C2T x film.

[0136] (3) Ink / Ti3C2T x Composite film construction. A commercial marker pen was used to x The film is hand-painted with stripes of uniform width and spacing, wherein the ink width is 0.8 mm and the spacing is 0.2 mm. The number of times each stripe is painted is inconsistent. The number of times is determined according to the rule of "…-2-4-6-4-2-4-6-…" so that the thickness of each stripe changes gradually, and the ink with stripes with gradient ink thickness changes is obtained. x Composite film.

[0137] Step (4) refers to Example 1.

[0138] In the flexible pressure sensor prepared in this comparative example, the area covered by the ink pattern accounts for 80% of the MXene layer, and the thickness of the ink layer is 3, 6, and 9 μm, respectively.

[0139] Comparative Example 2

[0140] Step (1) refers to Example 1.

[0141] (2) Preparation of surface patterned ink / film-forming substrate. A stripe pattern with uniform width and spacing was hand-painted on commercial semi-hydrophobic paper using a commercial marker pen, wherein the ink width was 0.8 mm and the spacing was 0.2 mm. The number of times each stripe was painted was inconsistent, and the number of times was determined according to the rule of "…-1-2-3-2-1-2-3-…" so that the thickness of each stripe varied in a gradient, thereby obtaining a paper-based film-forming substrate with stripes with gradient ink thickness variations.

[0142] Steps (3)-(4) refer to Example 1.

[0143] In the flexible pressure sensor prepared in this comparative example, the area covered by the ink pattern accounts for 80% of the MXene layer, and the thickness of the ink layer is 0.01-0.09 μm.

[0144] Comparative Example 3

[0145] Step (1) refers to Example 1.

[0146] (2) Preparation of surface patterned ink / film-forming substrate. A stripe pattern with uniform width and spacing was hand-painted on commercial semi-hydrophobic paper using a commercial marker pen, wherein the ink width was 0.8 mm and the spacing was 0.2 mm. The number of times each stripe was painted was inconsistent, and the number of times was determined according to the rule of "…-3-6-9-6-3-6-9-…" so that the thickness of each stripe varied in a gradient, thereby obtaining a paper-based film-forming substrate with stripes with gradient ink thickness variations.

[0147] Steps (3)-(4) refer to Example 1.

[0148] In the flexible pressure sensor prepared in this comparative example, the area covered by the ink pattern accounts for 80% of the MXene layer, and the thickness of the ink layer is 21-25 μm.

[0149] Comparative Example 4

[0150] Step (1) refers to Example 1.

[0151] (2) Preparation of surface patterned ink / film-forming substrate. A stripe pattern with uniform width and spacing was hand-painted on commercial semi-hydrophobic paper using a commercial marker pen, wherein the ink width was 0.8 mm, the spacing was 0.2 mm, and each stripe was painted six times, to obtain a paper-based film-forming substrate with ink stripes of uniform thickness.

[0152] Steps (3)-(4) refer to Example 1.

[0153] In the flexible pressure sensor prepared in this comparative example, the area covered by the ink pattern accounts for 80% of the MXene layer, and the thickness of the ink layer is 20 μm.

[0154] Figure 2 The surface resistance diagram of the ink / MXene composite film with different ink coating times (i.e. different ink thickness) is shown. It can be seen from the figure that the more times the ink is coated (i.e. the thicker the ink layer), the greater the surface resistance of the composite film.

[0155] Figure 3 The ink / Ti3C2T prepared in Example 1 is shown. x Surface SEM image of the composite film. As can be seen from the figure, the composite film replicates the fibrous structure of the substrate, and there is a large amount of discontinuous ink coverage in the ink area, that is, there are many cracks between the inks caused by deformation of the substrate during the transfer process, so some MXene is exposed.

[0156] Figure 4 The ink / Ti3C2T prepared in Comparative Example 1 is shown. x Surface / cross-section SEM images of the composite film. It can be seen from the figure that the ink / Ti3C2T prepared by this method xThe ink on the surface of the composite film is not only continuous, making the MXene surface in this area completely insulating; it also covers the fibrous structure of the MXene-replicated substrate, thus limiting its sensing performance.

[0157] Figure 5 The sensor signal output curves of the flexible pressure sensors prepared in Example 1 and Comparative Example 1 are shown. As can be seen from the figure, compared with the pressure sensor obtained by directly writing ink stripes on the MXene film in Comparative Example 1, the surface patterned ink / MXene pressure sensor prepared by the transfer method in Example 1 has a higher sensitivity, achieving a pressure range of up to 413 kPa in the pressure range of 0-10 kPa. -1 High sensitivity, and can maintain 173kPa in the pressure range of 10-20kPa -1 High sensitivity.

[0158] Figure 6 The sensor signal output curves of the flexible pressure sensors prepared in Comparative Examples 2 and 3 are shown. It can be seen from the figure that compared with the ink / MXene pressure sensor with appropriate oil film thickness obtained in Example 1, the composite film pressure sensors with too low or too high ink thickness obtained in Comparative Examples 2 and 3 have lower sensitivity.

[0159] Figure 7 The sensor signal output curve of the flexible pressure sensor prepared in Comparative Example 4 is shown. As can be seen from the figure, compared with the ink / MXene pressure sensor with excellent structure obtained in Example 1, the composite film pressure sensor with ink stripes without periodic thickness change obtained in Comparative Example 4 has lower sensitivity.

[0160] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

Claims

1. A flexible pressure sensor based on ink / MXene composite film, characterized in that: The pressure sensor is a two-piece structure that overlaps and faces each other, including: a flexible substrate, a sensitive material formed on the flexible substrate, electrodes arranged at both ends of the sensitive material, wires connected to the electrodes, and a packaging layer for protecting the sensitive material; The sensitive material is an ink / MXene composite film formed by discontinuously covering the MXene layer with ink in a specific pattern; the ink pattern includes one of gradient stripes with gradient ink thickness and step stripes composed of self-stepping stripes; The ink layer has a thickness of 0.1 to 20 μm; the area covered by the ink pattern accounts for 10 to 90% of the MXene layer.

2. The flexible pressure sensor based on ink / MXene composite film according to claim 1, characterized in that: The area covered by the ink pattern accounts for 50 to 80% of the MXene layer.

3. The flexible pressure sensor based on ink / MXene composite film according to claim 1, characterized in that: The flexible substrate is in the form of a film or fabric, with a length and width both greater than 5 mm and a thickness of 0.05 to 1 mm; the material of the flexible substrate is one of polyurethane, polyacrylate, silicone rubber, polydimethylsiloxane PDMS, polyimide, polyethylene terephthalate, polyethylene PE, polyvinyl chloride, polypropylene, pure cotton cloth, double-sided tape, or biofiber.

4. The flexible pressure sensor based on ink / MXene composite film according to claim 1, characterized in that: The chemical formula of the MXene is M n+1 X n ; wherein n = 1-4, M is a transition metal element, and X is a carbon and / or nitrogen element; the surface of the MXene layer in the composite film contains end groups, and the end groups include at least one of -F, -OH, and -O; the thickness of the MXene layer is 1-50 μm, and the Zeta potential is -10 to -50 mV.

5. The flexible pressure sensor based on ink / MXene composite film according to claim 4, characterized in that: The thickness of the MXene layer is 2-10 μm, and the Zeta potential is -30 to -50 mV.

6. The flexible pressure sensor based on ink / MXene composite film according to claim 1, characterized in that: The encapsulation layer has a length and a width both greater than 5 mm and a thickness of 0.005 to 1 mm; the material of the encapsulation layer is selected from one of polyurethane, polyacrylate, silicone rubber, polydimethylsiloxane, polyimide, polyethylene terephthalate, polyethylene, polyvinyl chloride, polypropylene, pure cotton cloth, polypropylene transparent tape or biofiber.

7. A method for preparing a flexible pressure sensor based on ink / MXene composite film according to claim 1, characterized in that: include: The MAX phase powder material was added into a mixed solution of hydrochloric acid and lithium fluoride, and after etching, centrifugal separation was performed to obtain a multilayer MAX n+1 X n Powder; multi-layer M n+1 X n The powder is dissolved, centrifuged, and dried to obtain MXene powder; the MXene powder is redissolved, ultrasonicated, and vortexed to obtain a MXene dispersion; Drawing an ink pattern on a film-forming substrate to obtain a surface-patterned ink / film-forming substrate; Coating the MXene dispersion on the surface of the ink / film-forming substrate with a patterned surface, and drying to obtain an ink / MXene composite film; The ink / MXene composite film is fixed on a flexible substrate, electrodes and wires are constructed to obtain a single ink / MXene / flexible substrate composite film, and two composite films are overlapped and packaged up and down to obtain the flexible pressure sensor based on the ink / MXene composite film.

8. The preparation method according to claim 7, characterized in that The molar ratio of the hydrochloric acid, lithium fluoride and MAX phase powder is (40-120): (10-30): (0.5-2); the concentration of the MXene dispersion is 1-50 mg / mL.

9. The preparation method according to claim 8, characterized in that The concentration of the MXene dispersion is 10-50 mg / mL.

10. The preparation method according to claim 7, characterized in that: The ink includes one of commercial marker ink, commercial pencil ink, commercial gel pen ink, or commercial fluorescent pen ink; there is a Zeta potential difference between the ink and the MXene nanosheet.

11. The preparation method according to claim 7, characterized in that: The film-forming substrate comprises one of commercial semi-hydrophobic paper, commercial mixed cellulose filter membrane, polydimethylsiloxane PDMS, or glass.

12. The preparation method according to claim 7, characterized in that The coating amount of the MXene dispersion is 0.05-1 mL / cm 2 .

13. The preparation method according to any one of claims 7 to 12, characterized in that: After coating the MXene dispersion, the mixture is dried at 15-35° C. and normal pressure.

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