Low-impedance polyimide-based all-fiber structure flexible pressure sensor and preparation method thereof

Abstract

The invention belongs to the technical field of flexible electronics, and particularly relates to a low-impedance polyimide-based all-fiber structure flexible pressure sensor and a preparation method thereof. The low-impedance polyimide-based all-fiber structure flexible pressure sensor comprises electrode fiber layers and a dielectric fiber layer, the electrode fiber layers are arranged on the upper surface and the lower surface of the dielectric fiber layer respectively, and the electrode fiber layers and the dielectric fiber layer form gradient dielectric filler distribution; and the electrode fiber layer and the dielectric fiber layer are laminated fibers prepared by mixing a polyimide material, a dielectric filler and a spinning aid and then carrying out airflow spinning. The three-layer structure and the gradient dielectric filler content design are adopted, the excellent sensing performance can still be kept in the temperature range of-70 DEG C to 200 DEG C, and high response consistency is kept in high and low temperature environments.

Description

Technical Field

[0001] This invention belongs to the field of flexible electronics technology, specifically relating to a low-impedance polyimide-based all-fiber flexible pressure sensor and its preparation method. Background Technology

[0002] With the rapid development of flexible electronics and electronic skin technologies, flexible pressure sensors are showing broad application prospects in fields such as robotic tactile sensing, human-computer interaction, medical rehabilitation, and industrial monitoring. High-performance flexible pressure sensors need to simultaneously possess high sensitivity and a wide sensing range to adapt to accurate perception in complex environments. However, existing technologies generally suffer from the problem of difficulty in achieving both performance targets.

[0003] Currently, common flexible capacitive pressure sensors are mainly divided into two categories: ionic and non-ionic. Ionic sensors achieve signal amplification through ion migration and the electrical double-layer effect, enabling them to output large capacitance changes at low pressures and exhibiting high sensitivity and good weak signal resolution. However, the ionic liquids or gel materials they rely on suffer from problems such as easy leakage, volatility, freezing at low temperatures, or decomposition at high temperatures. Furthermore, the ion conduction process is extremely sensitive to temperature, leading to severe performance degradation in extreme environments and making it difficult to guarantee long-term stability. This limits their application in extreme conditions such as aerospace, polar scientific research, and deep-sea operations.

[0004] In contrast, non-ionic sensors operate based on electronic polarization mechanisms, offering advantages such as high material stability, good temperature resistance, and low packaging requirements, making them more reliable in extreme temperatures and harsh environments. However, the capacitance variation of these sensors is primarily limited by minute adjustments to the dielectric constant, electrode spacing, or contact area, resulting in lower capacitance signal output and sensitivity far inferior to ionic devices. Furthermore, they struggle to maintain stable high responsivity over a wide pressure range, indicating a significant overall performance bottleneck. Therefore, achieving a unified breakthrough in high sensitivity and ultra-wide sensing range while maintaining the environmental stability of non-ionic devices has become a critical technical challenge that urgently needs to be addressed in this field. Summary of the Invention

[0005] To address the aforementioned shortcomings, this invention provides a low-impedance polyimide-based all-fiber flexible pressure sensor and its fabrication method. Employing a three-layer structure and a gradient dielectric filler content design, it maintains excellent sensing performance within a temperature range of -70 ℃ to 200 ℃ and exhibits high response consistency under both high and low temperature conditions.

[0006] The technical solution of the present invention:

[0007] The first technical problem to be solved by the present invention is to provide a low-impedance polyimide-based all-fiber flexible pressure sensor, the sensor comprising an electrode fiber layer and a dielectric fiber layer, the electrode fiber layer being respectively disposed on the upper and lower surfaces of the dielectric fiber layer, and the electrode fiber layer and the dielectric fiber layer forming a gradient dielectric filler distribution;

[0008] The electrode fiber layer and dielectric fiber layer are laminated fibers obtained by air-jet spinning after mixing polyimide material, dielectric filler and spinning aid.

[0009] Furthermore, the electrode fiber layer is a laminated fiber with high dielectric content, and the dielectric fiber layer is a laminated fiber with low dielectric content.

[0010] Furthermore, in the low dielectric content laminated fiber, the mass of the dielectric filler accounts for 5-12% of the total solid mass; in the high dielectric content laminated fiber layer, the mass of the dielectric filler accounts for 18-20% of the total solid mass; the total solid mass = the mass of the polymer material + the mass of the dielectric filler + the mass of the spinning aid.

[0011] Both the electrode fiber layer and the dielectric fiber layer exhibit significant changes in dielectric properties with pressure. Meanwhile, the polyimide matrix provides excellent mechanical properties, and the physical interpenetrating network between fibers enhances structural stability, thereby improving the overall pressure resistance of the all-fiber structure.

[0012] Furthermore, the laminated fiber is prepared by the following method: polyamic acid, dielectric filler, spinning aid and solvent are mixed evenly to prepare a spinning solution, and then the spinning solution is used to prepare laminated fiber by air-jet spinning.

[0013] Furthermore, the dielectric filler is carbon nanotube, graphene, carbon black, MXene, or carbon fiber.

[0014] Furthermore, the dielectric filler is a multi-walled carbon nanotube or a single-walled carbon nanotube.

[0015] Preferably, the dielectric filler is a multi-walled carbon nanotube.

[0016] Furthermore, the spinning aid is polyacrylonitrile, polyvinylpyrrolidone, or polyethylene oxide; used to improve the spinnability of the spinning solution.

[0017] Furthermore, the solvent is tetrahydrofuran, N,N-dimethylformamide, or N,N-dimethylacetamide; capable of simultaneously dissolving the spinning aid and polyamic acid.

[0018] The second technical problem to be solved by this invention is to provide a method for fabricating the above-mentioned low-impedance polyimide-based all-fiber flexible pressure sensor, comprising the following steps:

[0019] S1. Polyamic acid, dielectric filler, spinning aid and solvent are mixed evenly to prepare spinning solution, and then the spinning solution is used to produce laminated fibers by air-jet spinning.

[0020] S2. Add spinning solution sequentially in the order of electrode fiber layer - dielectric fiber layer - electrode fiber layer, then perform compression treatment and imidization treatment, and attach conductive wires to the two electrode fiber layers respectively to obtain a low-impedance polyimide-based all-fiber flexible pressure sensor.

[0021] Furthermore, in step S1, the laminated fibers include laminated fibers with high dielectric content and laminated fibers with low dielectric content.

[0022] Furthermore, in the spinning solution for preparing laminated fibers with low dielectric content, the mass of the dielectric filler accounts for 5-12% of the total solid mass, and the mass of the spinning aid accounts for 1-10% of the total solid mass. The total solid mass = mass of polymer material + mass of dielectric filler + mass of spinning aid; the solid content of the spinning solution is 10-30%.

[0023] Furthermore, in the spinning solution for preparing laminated fibers with high dielectric content, the mass of dielectric filler accounts for 18-20% of the total solid mass, the mass of spinning aid accounts for 1-10% of the total solid mass, and the mass of polyamic acid accounts for 80-90% of the total solid mass.

[0024] Furthermore, the dielectric filler is carbon nanotube, graphene, carbon black, MXene, or carbon fiber.

[0025] Furthermore, the dielectric filler is a multi-walled carbon nanotube or a single-walled carbon nanotube.

[0026] Preferably, the dielectric filler is a multi-walled carbon nanotube.

[0027] Furthermore, the spinning aid is polyacrylonitrile, polyvinylpyrrolidone, or polyethylene oxide.

[0028] Furthermore, the solvent is tetrahydrofuran, N,N-dimethylformamide, or N,N-dimethylacetamide.

[0029] Further, in step S1, during air-jet spinning, the spinning solution is added to the injection pump with a needle orifice diameter of 0.05-0.4 mm and a spinning solution feed rate of 0.01-0.05 mL / min; the air pressure at the jet nozzle is 0.05-0.2 MPa, and the distance from the nozzle to the receiving device is adjusted to 20-30 cm; each layer of stacked fibers is collected for 10-20 min.

[0030] Furthermore, in step S2, the temperature program for the imidization treatment is as follows: 0.5 h at 80 ℃, 0.5 h at 100 ℃, 0.5 h at 150 ℃, 0.5 h at 200 ℃, 0.5 h at 250 ℃, and 1 h at 300 ℃.

[0031] The present invention has the following beneficial effects:

[0032] 1. This invention achieves functionalization by adding different amounts of dielectric fillers to polyamic acid, and prepares spinning solutions with high dielectric content and low dielectric content respectively. Then, a simple air-jet spinning process is used to prepare gradient dielectric fibers with ultra-high porosity (greater than 80%), which are more prone to deformation compared with unstructured polymer materials. The electrode fiber layer with variable conductivity and the dielectric fiber layer with variable impedance work together to improve the sensing signal of the device.

[0033] 2. This invention employs a simple air-jet spinning method, which offers advantages such as simple process, low cost, open processing environment, safety, and strong operability. Furthermore, the resulting low-impedance polyimide-based all-fiber flexible pressure sensor possesses a stable, high-porosity all-fiber structure. The stable fiber network structure formed through fiber-to-fiber overlap and physical interpenetration avoids the functional layer separation problems that may occur with multi-layer fiber structures.

[0034] 3. In the low-impedance polyimide-based all-fiber flexible pressure sensor of the present invention, both the polyimide matrix and the dielectric material possess excellent resistance to high and low temperatures, radiation resistance, and good mechanical properties, which can solve the problem of sensor failure under extreme working conditions. This sensor can be integrated into protective clothing as a tactile sensing unit for extreme applications such as manual labor and robotic tactile feedback in extreme environments.

[0035] 4. The low-impedance polyimide-based all-fiber flexible pressure sensor of this invention exhibits multi-force sensitivity to pressure, bending, and tension. The three-dimensional porous nanofiber scaffold and elastic structure provide more contact points for the pressure sensor, and possess large deformation space and resilience. Furthermore, the low-impedance sensor mechanism facilitates amplification of the capacitive response signal, and the variable conductivity electrode fiber layer optimizes the electrode's contribution to capacitance, thereby achieving sensing performance with high sensitivity, short response time, wide detection range, and wide temperature applicability. Specifically, the sensitivity is improved by at least three orders of magnitude, and the response consistency is high under high and low temperature environments. Attached Figure Description

[0036] Figure 1 Figure 1 shows the microstructure of the low-impedance polyimide-based all-fiber flexible pressure sensor obtained in Example 1; Figure 2b is an enlarged view of the marked area in Figure 3a.

[0037] Figure 2 These are microscopic morphology diagrams of the electrode fiber layer and dielectric fiber layer in Example 1; Figure a shows the dielectric fiber layer, and Figure b shows the electrode fiber layer.

[0038] Figure 3 This is a potential diagram of the overlapping points of the laminated fibers in Example 1;

[0039] Figure 4 The sensitivity performance diagram of the low-impedance polyimide-based all-fiber flexible pressure sensor obtained in Example 1 is shown.

[0040] Figure 5 The response time signal diagram is shown for the low-impedance polyimide-based all-fiber flexible pressure sensor obtained in Example 1.

[0041] Figure 6 The image shows the cyclic response stability of the low-impedance polyimide-based all-fiber flexible pressure sensor obtained in Example 1 under different temperature environments.

[0042] Figure 7 The image shows the microstructure of the flexible pressure sensor obtained in Comparative Example 1.

[0043] Figure 8 The sensitivity performance diagram of the flexible pressure sensor obtained in Comparative Example 1 is shown.

[0044] Figure 9 The image shows the microstructure of the flexible pressure sensor obtained in Comparative Example 2.

[0045] Figure 10 The graph shows the sensitivity performance of the flexible pressure sensor obtained in Comparative Example 2. Detailed Implementation

[0046] In a first aspect, the present invention provides a low-impedance polyimide-based all-fiber flexible pressure sensor, the sensor comprising an electrode fiber layer and a dielectric fiber layer, the electrode fiber layer being disposed on the upper surface and the lower surface of the dielectric fiber layer respectively, and the electrode fiber layer and the dielectric fiber layer forming a gradient dielectric filler distribution;

[0047] The electrode fiber layer and dielectric fiber layer are laminated fibers obtained by air-jet spinning after mixing polyimide material, dielectric filler and spinning aid.

[0048] Furthermore, the electrode fiber layer is a high-dielectric-content laminated fiber, and the dielectric fiber layer is a low-dielectric-content laminated fiber. In the low-dielectric-content laminated fiber, the mass of the dielectric filler accounts for 5-12% of the total solid mass; in the high-dielectric-content laminated fiber layer, the mass of the dielectric filler accounts for 18-20% of the total solid mass; the total solid mass = the mass of the polymer material + the mass of the dielectric filler + the mass of the spinning aid.

[0049] The electrode fiber layer is used to enhance the conductivity of the electrode, ensuring the stability of the overall structure and good capacitance change response; the dielectric fiber layer in the middle is a low dielectric content laminated fiber, which forms a gradient dielectric filler distribution with the high dielectric content laminated fibers on the upper and lower surfaces, which can optimize the capacitance response when the temperature changes.

[0050] Both the electrode fiber layer and the dielectric fiber layer exhibit significant changes in dielectric properties with pressure. Meanwhile, the polyimide matrix provides excellent mechanical properties, and the physical interpenetrating network between fibers enhances structural stability, thereby improving the overall pressure resistance of the all-fiber structure.

[0051] Secondly, a method for fabricating the aforementioned low-impedance polyimide-based all-fiber flexible pressure sensor is provided, comprising the following steps:

[0052] S1. Polyamic acid, dielectric filler, spinning aid and solvent are mixed evenly to prepare spinning solution, and then the spinning solution is used to produce laminated fibers by air-jet spinning.

[0053] S2. Add spinning solution sequentially in the order of electrode fiber layer - dielectric fiber layer - electrode fiber layer, then perform compression treatment and imidization treatment, and attach conductive wires to the two electrode fiber layers respectively to obtain a low-impedance polyimide-based all-fiber flexible pressure sensor.

[0054] Different amounts of dielectric filler are added to achieve functionalization of polymer-based fibers. High-dielectric-content laminated fibers serve as electrode fiber layers, while low-dielectric-content laminated fibers serve as dielectric fiber layers. Continuous spinning process enhances structural stability by forming a physical interpenetrating interface. High-temperature imidization leads to the mutual melting and welding between fiber matrices, further improving the stability of the fiber network. Polyimide material serves as the structural matrix of the fiber, providing good mechanical properties for the three-dimensional structure. Spinning aids are used to improve the spinnability of the composite material and obtain stable fiber output.

[0055] Furthermore, in step S1, the laminated fibers include laminated fibers with high dielectric content and laminated fibers with low dielectric content.

[0056] Furthermore, in the spinning solution for preparing laminated fibers with low dielectric content, the mass of the dielectric filler accounts for 5-12% of the total solid mass, and the mass of the spinning aid accounts for 1-10% of the total solid mass. The total solid mass = mass of polymer material + mass of dielectric filler + mass of spinning aid; the solid content of the spinning solution is 10-30%.

[0057] Furthermore, in the spinning solution for preparing laminated fibers with high dielectric content, the mass of dielectric filler accounts for 18-20% of the total solid mass, the mass of spinning aid accounts for 1-10% of the total solid mass, and the mass of polyamic acid accounts for 80-90% of the total solid mass.

[0058] Further, in step S1, during air-jet spinning, the spinning solution is added to the injection pump with a needle orifice diameter of 0.05-0.4 mm and a spinning solution feed rate of 0.01-0.05 mL / min; the air pressure at the jet nozzle is 0.05-0.2 MPa, and the distance from the nozzle to the receiving device is adjusted to 20-30 cm; each layer of stacked fibers is collected for 10-20 min.

[0059] Furthermore, in step S2, the temperature program for the imidization treatment is as follows: 0.5 h at 80 ℃, 0.5 h at 100 ℃, 0.5 h at 150 ℃, 0.5 h at 200 ℃, 0.5 h at 250 ℃, and 1 h at 300 ℃.

[0060] The present invention will be further illustrated below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field.

[0061] Example 1

[0062] A low-impedance polyimide-based all-fiber flexible pressure sensor, the preparation method of which includes the following steps:

[0063] (1) 20 g of multi-walled carbon nanotubes were added to 180 g of N,N-dimethylformamide solvent and sonicated for 6 h to obtain a 10 wt% carbon nanotube dispersion.

[0064] (2) Take 4.5 g of carbon nanotube dispersion and add 0.045 g of polyethylene oxide (spinning aid), stir at 50 °C for 1 h, then add 10 g of polyamic acid solution (18 wt%), and stir magnetically at 50 °C for 3 h to obtain electrode fiber layer spinning solution;

[0065] Take 1.3 g of carbon nanotube dispersion and add 0.013 g of polyethylene oxide (spinning aid), stir at 50 °C for 1 h, add 10 g of polyamic acid solution (18 wt%), and stir magnetically at 50 °C for 3 h to obtain dielectric fiber layer spinning solution;

[0066] (3) Add the electrode fiber layer spinning solution to the micro injection pump. The needle orifice diameter is 0.05-0.4 mm, the solution feed rate is 0.05 mL / min, the air pressure of the jet nozzle is set to 0.12 MPa, the distance from the nozzle to the receiving cage is adjusted to 25 cm, and spinning is performed for 20 min.

[0067] (4) Under the same conditions, the dielectric fiber layer spinning solution was replaced and spun for 20 min. Then, the electrode fiber layer spinning solution was replaced and spun for 20 min.

[0068] (5) The obtained all-fiber sponge knot is pre-compressed and then placed in a muffle furnace for imidization treatment. The heating program is as follows: 80 ℃ for 0.5 h, 100 ℃ for 0.5 h, 150 ℃ for 0.5 h, 200 ℃ for 0.5 h, 250 ℃ for 0.5 h, 300 ℃ for 1 h. Finally, the sample is cut into 1 cm × 1 cm size, and conductive silver wire is attached to the surface of the upper and lower electrode fiber layers to obtain a low-impedance polyimide-based all-fiber flexible pressure sensor.

[0069] The low-impedance polyimide-based all-fiber flexible pressure sensor obtained in Example 1 was characterized using scanning electron microscopy, and the results are as follows: Figure 1 As shown. The fibers were characterized using transmission electron microscopy, such as... Figure 2 As shown. The fiber structure was cut into samples of 0.7 cm × 0.7 cm × 0.9 mm. The porosity was tested and calculated using the drainage method, and then calculated using the formula P = [(V0 - V) / V0] * 100%, where V0 = 0.9 cm. 3 After draining 0.089 mL of water, the calculated porosity P = 90.1%. The potential distribution at the fiber overlap was tested using atomic force microscopy. Figure 3 As shown.

[0070] Depend on Figure 1 It is known that the laminated fibers of the present invention have an ultra-high porosity of 90% and a fiber diameter of 0.8-2 micrometers; the sensor is composed of multiple layers of laminated fibers and has a physically interpenetrating fiber network. Figure 2 It can be seen that carbon nanotubes of different contents are uniformly oriented within the fibers; the orientation of the laminated fibers is obvious, and the distribution of multi-walled carbon nanotubes differs significantly between the high-dielectric-content laminated fibers in the electrode fiber layer and the low-dielectric-content laminated fibers in the dielectric fiber layer. Figure 3 It can be seen that the high potential at the overlap proves that fiber overlap can form a new dielectric network, and the potential at the fiber overlap is significantly increased.

[0071] Using a universal tensile testing machine and an LCR bridge, the capacitance of the sensor changes with pressure. The resulting sensitivity signal and response time of the low-impedance polyimide-based all-fiber flexible pressure sensor are shown in the figures below. Figure 4 and Figure 5 As shown; a universal tensile testing machine equipped with a temperature environment response chamber was used to conduct high-cycle cyclic tests at -70 ℃ and 200 ℃ under 2000 kPa high pressure, and the results are as follows. Figure 6 As shown.

[0072] Depend on Figure 4 and Figure 5 It is evident that the low-impedance polyimide-based all-fiber flexible pressure sensor of this invention possesses excellent sensitivity and exhibits outstanding consistency across different temperatures; its response speed is higher than that of human skin. The sensitivity can reach 158 kPa. -1 The response time is within 10 ms.

[0073] Depend on Figure 6 It is known that the low-impedance polyimide-based all-fiber flexible pressure sensor of the present invention can maintain excellent sensing performance in the temperature range of -70 ℃ to 200 ℃ and has service stability under ultra-high pressure.

[0074] Comparative Example 1

[0075] The difference between Comparative Example 1 and Example 1 is that no multi-walled carbon nanotubes are added to the dielectric fiber layer; specifically: in step (2), 0.045 g of polyethylene oxide (spinning aid) is added to 4.5 g of DMF solution, stirred at 50 °C for 1 h, 10 g of polyamic acid solution (18 wt%) is added, and magnetically stirred at 50 °C for 3 h to obtain the dielectric fiber layer spinning solution.

[0076] The flexible pressure sensor obtained in Comparative Example 1 was characterized using scanning electron microscopy, and the results are as follows: Figure 7 As shown in the figure. The sensitivity performance graph of the obtained flexible pressure sensor is as follows. Figure 8 As shown.

[0077] Depend on Figure 7 and Figure 8 It can be seen that the sensitivity of the flexible pressure sensor obtained in Comparative Example 1 is less than 0.027 kPa. -1 The resistance is much smaller than that of the low-impedance polyimide-based all-fiber flexible pressure sensor in Example 1, and the two have significant differences in high-temperature sensing performance.

[0078] Comparative Example 2

[0079] The difference between Comparative Example 2 and Example 1 is that multi-walled carbon nanotubes are not added to the dielectric fiber layer, but 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid (IL) is added; specifically: in step (2), 0.9 g of IL and 0.45 g of polyacrylonitrile (spinning aid) are added to 4.5 g of DMF solution, stirred at 50 ℃ for 1 h, 10 g of polyamic acid solution (18wt%) is added, and magnetically stirred at 50 ℃ for 3 h to obtain the dielectric fiber layer spinning solution.

[0080] The flexible pressure sensor obtained in Comparative Example 2 was characterized using scanning electron microscopy, and the results are as follows: Figure 9 As shown in the figure. The sensitivity performance graph of the obtained flexible pressure sensor is as follows. Figure 10 As shown.

[0081] Depend on Figure 9 and Figure 10 It can be seen that the sensitivity of the flexible pressure sensor obtained in Comparative Example 2 is significantly different from that in Example 1 at different temperatures, but the maximum sensitivity of the two is comparable under high temperature conditions.

[0082] It should be noted that while the preferred embodiments of the present invention are provided in the specification and accompanying drawings, the present invention can be implemented in many different forms and is not limited to the embodiments described in this specification. These embodiments are not intended to impose additional limitations on the content of the present invention; their purpose is to provide a more thorough and comprehensive understanding of the disclosure of the present invention. Furthermore, the above-mentioned technical features can be combined with each other to form various embodiments not listed above, all of which are considered to be within the scope of the present invention specification. Moreover, those skilled in the art can make various improvements, substitutions, or modifications based on common technical knowledge and conventional methods without departing from the above-described technical concept of the present invention, and all such improvements, substitutions, or modifications should fall within the protection scope of the appended claims.

Claims

1. A low-impedance polyimide-based all-fiber flexible pressure sensor, characterized in that, The sensor includes an electrode fiber layer and a dielectric fiber layer, wherein the electrode fiber layer is disposed on the upper surface and the lower surface of the dielectric fiber layer, and the electrode fiber layer and the dielectric fiber layer form a gradient dielectric filler distribution; The electrode fiber layer and dielectric fiber layer are laminated fibers obtained by air-jet spinning after mixing polyimide material, dielectric filler and spinning aid.

2. The low-impedance polyimide-based all-fiber flexible pressure sensor according to claim 1, characterized in that, The electrode fiber layer is a high dielectric content laminated fiber, and the dielectric fiber layer is a low dielectric content laminated fiber. In the low dielectric content laminated fiber, the mass of the dielectric filler accounts for 5-12% of the total solid mass; in the high dielectric content laminated fiber layer, the mass of the dielectric filler accounts for 18-20% of the total solid mass; the total solid mass = the mass of the polymer material + the mass of the dielectric filler + the mass of the spinning aid.

3. The low-impedance polyimide-based all-fiber flexible pressure sensor according to claim 1, characterized in that, The laminated fibers are prepared by the following method: polyamic acid, dielectric filler, spinning aid and solvent are mixed evenly to prepare a spinning solution, and then the spinning solution is used to prepare laminated fibers by air-jet spinning.

4. The low-impedance polyimide-based all-fiber flexible pressure sensor according to claim 3, characterized in that, The dielectric filler is carbon nanotube, graphene, carbon black, MXene, or carbon fiber; The dielectric filler is a multi-walled carbon nanotube or a single-walled carbon nanotube. The dielectric filler is a multi-walled carbon nanotube; The spinning aid is polyacrylonitrile, polyvinylpyrrolidone, or polyethylene oxide; The solvent is tetrahydrofuran, N,N-dimethylformamide, or N,N-dimethylacetamide.

5. The method for preparing the low-impedance polyimide-based all-fiber flexible pressure sensor according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Polyamic acid, dielectric filler, spinning aid and solvent are mixed evenly to prepare spinning solution, and then the spinning solution is used to produce laminated fibers by air-jet spinning. S2. Add spinning solution sequentially in the order of electrode fiber layer - dielectric fiber layer - electrode fiber layer, then perform compression treatment and imidization treatment, and adhere conductive wires to obtain a low-impedance polyimide-based all-fiber flexible pressure sensor.

6. The method for fabricating a low-impedance polyimide-based all-fiber flexible pressure sensor according to claim 5, characterized in that, In step S1, the laminated fibers include laminated fibers with high dielectric content and laminated fibers with low dielectric content.

7. The method for fabricating a low-impedance polyimide-based all-fiber flexible pressure sensor according to claim 6, characterized in that, In the spinning solution for preparing laminated fibers with low dielectric content, the mass of the dielectric filler accounts for 5-12% of the total solid mass, and the mass of the spinning aid accounts for 1-10% of the total solid mass. The total solid mass = mass of polymer material + mass of dielectric filler + mass of spinning aid; the solid content of the spinning solution is 10-30%. In the spinning solution for preparing laminated fibers with high dielectric content, the mass of dielectric filler accounts for 18-20% of the total solid mass, and the mass of spinning aid accounts for 1-10% of the total solid mass.

8. The method for fabricating a low-impedance polyimide-based all-fiber flexible pressure sensor according to claim 5, characterized in that, In step S1, the dielectric filler is carbon nanotube, graphene, carbon black, MXene, or carbon fiber. The dielectric filler is a multi-walled carbon nanotube or a single-walled carbon nanotube. The dielectric filler is a multi-walled carbon nanotube; The spinning aid is polyacrylonitrile, polyvinylpyrrolidone, or polyethylene oxide; The solvent is tetrahydrofuran, N,N-dimethylformamide, or N,N-dimethylacetamide.

9. The method for fabricating a low-impedance polyimide-based all-fiber flexible pressure sensor according to claim 5, characterized in that, In step S1, during air-jet spinning, the spinning solution is added to the injection pump with a needle orifice diameter of 0.05-0.4 mm and a spinning solution feed rate of 0.01-0.05 mL / min; the air pressure at the jet nozzle is 0.05-0.2 MPa, and the distance from the nozzle to the receiving device is adjusted to 20-30 cm; each layer of stacked fibers is collected for 10-20 min.

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