High-sensitivity capacitive pressure sensing fiber with three-level heterostructure and preparation method and application thereof

Abstract

The invention discloses a high-sensitivity capacitive pressure sensing fiber with a three-level heterostructure and a preparation method and application thereof, the high-sensitivity capacitive pressure sensing fiber with the three-level heterostructure has a coaxial three-level heterostructure, and the high-sensitivity capacitive pressure sensing fiber with the three-level heterostructure sequentially comprises a core layer, a middle layer and an outer layer from inside to outside; the core layer is a conductive fiber electrode layer with excellent flexibility, the middle layer is a porous aerogel electrode layer, and the outer layer is an ionic liquid doped elastic polymer dielectric layer. The high-sensitivity capacitive pressure sensing fiber with the three-stage heterostructure has the advantages of high sensitivity, wide pressure sensing range and short response time, realizes stable capacitance response in a compression release cycle process, and is particularly suitable for high-precision pressure signal detection; good application prospects are shown in the technical field of intelligent wearable equipment.

Description

Technical Field

[0001] The present invention belongs to the technical field of flexible wearable sensors, and specifically relates to a highly sensitive capacitive pressure sensing fiber with a three-level heterogeneous structure, and a preparation method and application thereof. Background Art

[0002] Wearable electronic textiles, with their exceptional flexibility, breathability, and skin compatibility, are ideal for next-generation applications. Among their essential components, flexible fiber pressure sensors have garnered widespread attention due to their potential for advanced military systems, artificial intelligence, medical monitoring, and wearable human-machine interfaces. Capacitive fiber pressure sensors, consisting of two fiber electrodes coated with a dielectric layer, convert external pressure stimuli into a capacitive signal. These sensors offer low drift, high stability, and a simple structure, making them ideal candidates for flexible wearable sensing devices.

[0003] Traditional film capacitive sensors have a large sensing area, while fiber sensors use cross-fiber electrodes, which results in a limited overlapping area. The inherently small sensing area makes them extremely sensitive. Traditional sensors detect pressure by changing the dielectric constant due to changes in the thickness of the dielectric layer, while the thickness and area of ​​the fiber dielectric layer change slightly, resulting in low sensitivity and a narrow pressure response range. The pressurization process causes the dielectric layer to compress and harden, forming a double limitation mechanism, which ultimately makes the fiber capacitive sensor exhibit low sensitivity (<5kPa). -1 ) and the technical bottleneck of limited detection range (0-100kPa).

[0004] Therefore, developing fibers with high sensitivity, wide detection range, fast response time, and long-term durability remains a major challenge. Summary of the Invention

[0005] To address the issues raised in the aforementioned background technology, the present invention aims to provide a highly sensitive capacitive pressure sensing fiber with a three-level heterostructure, as well as its preparation method and application. The synergistic effect of the multi-level fiber electrode structure and the ionic-electronic double layer formed at the interface between the dielectric layer and the electrode enables the highly sensitive capacitive pressure sensing fiber with a three-level heterostructure of the present invention to achieve high sensitivity, a wide pressure sensing range, and a fast response time. Furthermore, the highly sensitive capacitive pressure sensing fiber with a three-level heterostructure of the present invention also exhibits high mechanical flexibility, electrical conductivity, and excellent compression-release cycle performance and bending cycle performance.

[0006] In order to achieve the above-mentioned object, the technical solution adopted by the present invention is as follows: on the one hand, the present invention provides a high-sensitive capacitive pressure sensing fiber with a three-level heterogeneous structure, wherein the high-sensitive capacitive pressure sensing fiber with a three-level heterogeneous structure has a coaxial three-level heterogeneous structure, which comprises a core layer, an intermediate layer, and an outer layer from the inside to the outside;

[0007] The core layer is a conductive fiber electrode layer with excellent flexibility, the middle layer is a porous aerogel electrode layer, and the outer layer is an elastic polymer dielectric layer doped with ionic liquid.

[0008] Furthermore, the diameter of the highly sensitive capacitive pressure sensing fiber with the three-level heterogeneous structure is 50-900 μm;

[0009] The diameter of the core layer is 20-200 μm, the thickness of the middle layer is 20-300 μm, and the thickness of the outer layer is 10-400 μm.

[0010] Furthermore, the conductive fiber is selected from at least one of carbon nanotube fiber, MXene fiber, graphene fiber, copper fiber and gold fiber.

[0011] Furthermore, the material of the porous aerogel electrode layer is a conductive carbene material or a conductive polymer; the conductive carbene material is selected from at least one of graphene, reduced graphene oxide, MXene and carbon nanotubes; the conductive polymer is selected from at least one of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid, polypyrrole, polyaniline, polythiophene, polynaphthylamine and poly(m-phenylenediamine);

[0012] The porous aerogel electrode layer has an axially arranged honeycomb pore structure with an average pore size of 5-20 μm and a mass density of 0.01-0.1 g cm -3 This facilitates the dissipation of stresses caused by significant external deformations.

[0013] Furthermore, the ionic liquid is selected from at least one of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([EMIM][OTf]), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][TFSI]), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][TFSI]), 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]), and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][Tf2N]);

[0014] The elastic polymer is selected from at least one of polydimethylsiloxane (PDMS), polyvinyl alcohol (PVA), polyvinylidene fluoride, poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-HFP), poly(vinylidene fluoride-co-hexafluoropropylene), polyurethane, thermoplastic polyurethane, and Ecoflex;

[0015] The mass ratio of the elastic polymer to the ionic liquid is 1:(0.5-8).

[0016] In another aspect, the present invention provides a method for preparing a highly sensitive capacitive pressure sensing fiber having a three-level heterogeneous structure as described above, comprising the following steps:

[0017] (1) preparing a dispersion of a porous aerogel electrode layer material with a mass percentage concentration of 0.1-50%, and uniformly coating the dispersion on the surface of the conductive fiber, then freezing the conductive fiber with the coating layer in liquid nitrogen, and freeze-drying the frozen conductive fiber to obtain a layered fiber electrode with an aerogel shell structure;

[0018] (2) The elastic polymer is dissolved in a solvent to form a solution with a mass percentage concentration of 8-25%, the ionic liquid is added to the above solution and mixed evenly to obtain an elastic polymer / ionic liquid mixed solution, the elastic polymer / ionic liquid mixed solution is evenly coated on the surface of a layered fiber electrode with an aerogel shell structure, and after drying, a highly sensitive capacitive pressure sensing fiber with a three-level heterogeneous structure is obtained.

[0019] Furthermore, the freeze-drying temperature in step (1) is -40°C to (-60)°C, the vacuum degree is 5-100 Pa, and the time is 5-36 hours.

[0020] Furthermore, the solvent in step (2) is selected from at least one of N,N-dimethylformamide (DMF), dimethyl sulfoxide, ethanol and acetone;

[0021] Preferably, the step (2) of dissolving the elastic polymer in a solvent to form a solution with a mass percentage concentration of 8-25% is specifically as follows: adding the elastic polymer to the solvent and stirring at 60-120° C. for 20-90 minutes to obtain a solution with a mass percentage concentration of 8-25%;

[0022] Preferably, the mass ratio of the elastic polymer to the ionic liquid in step (2) is 1:(0.5-8);

[0023] Preferably, the drying temperature in step (2) is 0-60° C., and the drying time is 3-24 h.

[0024] On the other hand, the present invention provides an application of a high-sensitive capacitive pressure sensing fiber with a three-level heterostructure as described above or a high-sensitive capacitive pressure sensing fiber with a three-level heterostructure prepared by any of the above preparation methods in flexible wearable electronic fabrics.

[0025] On the other hand, the present invention provides an application of a high-sensitive capacitive pressure sensing fiber with a three-level heterogeneous structure as described above, or a high-sensitive capacitive pressure sensing fiber with a three-level heterogeneous structure prepared by any of the preparation methods described above, in flexible electronic devices, electronic skin, medical monitoring products and human-computer interaction products.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The present invention prepares a pressure sensing fiber with a layered core-shell structure by sequentially constructing a porous aerogel electrode layer and an ionic liquid-doped dielectric layer outside a fiber electrode, and utilizes the synergistic effect of the porous structure and the double-layer mechanism to obtain a high-performance capacitive pressure sensing fiber.

[0028] (2) The high-sensitivity capacitive pressure sensing fiber with a three-level heterogeneous structure of the present invention has excellent pressure sensing performance, and has high sensitivity (the average sensitivity within the pressure range of 20kPa reaches 152.3kPa -1 ) and wide pressure sensing range (sensing range up to 1200kPa).

[0029] (3) The highly sensitive capacitive pressure sensing fiber of the present invention with a three-level heterogeneous structure can generate a capacitive response to a tiny weight (4 mg) with a fast response time (70 ms).

[0030] (4) The highly sensitive capacitive pressure sensing fiber with a three-level heterogeneous structure of the present invention has excellent sensing stability and can achieve stable capacitive response during more than 2000 cycles of compression and release.

[0031] (5) The highly sensitive capacitive pressure sensing fiber with a three-level heterogeneous structure of the present invention has excellent fatigue resistance. After 1000 bending cycles, the conductivity retention rate is greater than 70%.

[0032] (6) The high-sensitivity capacitive pressure sensing fiber with a three-level heterogeneous structure of the present invention can be applied to flexible electronic devices, electronic skin, medical monitoring, human-computer interaction and other fields because of its high sensitivity, wide sensing range and excellent fatigue resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a scanning electron microscope image of the cross section of the highly sensitive capacitive pressure sensing fiber with a three-level heterostructure prepared in Example 1 of the present invention;

[0034] Figure 2 This is a sensing performance diagram of a pressure sensor composed of highly sensitive capacitive pressure sensing fibers with a three-level heterostructure and cross-overlapped structures, as prepared in Example 1 of the present invention;

[0035] Figure 3 This is a response time diagram of a pressure sensor composed of cross-overlapping high-sensitive capacitive pressure sensing fibers having a three-level heterostructure prepared in Example 1 of the present invention;

[0036] Figure 4This is a graph showing the capacitance response data generated by a pressure sensor composed of cross-overlapping, highly sensitive capacitive pressure sensing fibers with a three-level heterostructure prepared in Example 1 of the present invention to a tiny weight;

[0037] Figure 5 Schematic diagram of the sensing mechanism of the highly sensitive capacitive pressure sensing fiber with a three-level heterogeneous structure of the present invention;

[0038] Figure 6 This is a graph showing the compressive stress-strain data of a pressure sensor composed of cross-overlapped, highly sensitive capacitive pressure sensing fibers with a three-level heterogeneous structure prepared in Example 1 of the present invention during 1000 compression and release cycles;

[0039] Figure 7 This is a graph showing sensing data of a pressure sensor composed of cross-overlapping, highly sensitive capacitive pressure sensing fibers with a three-level heterogeneous structure prepared in Example 1 of the present invention during 2000 compression and release cycles;

[0040] Figure 8 This is a graph showing the conductivity data of the highly sensitive capacitive pressure sensing fiber with a three-level heterogeneous structure prepared in Example 1 of the present invention during a bending cycle;

[0041] Figure 9 This is the actual weaving diagram of the highly sensitive capacitive pressure sensing fiber with a three-level heterogeneous structure prepared in Example 4 of the present invention. DETAILED DESCRIPTION

[0042] In order to better understand the content of the present invention, the content of the present invention is further described below in conjunction with specific implementation methods, but the protection content of the present invention is not limited to the following embodiments.

[0043] Example 1

[0044] Highly sensitive capacitive pressure sensing fiber with three-level heterogeneous structure: It has a coaxial three-level heterogeneous structure, which consists of a core layer, a middle layer, and an outer layer from the inside to the outside; the core layer is a carbon nanotube fiber electrode layer, the middle layer is a porous aerogel carbon nanotube electrode layer, and the outer layer is a PVDF-HFP dielectric layer doped with [EMIM][TFSI].

[0045] Preparation of highly sensitive capacitive pressure sensing fiber with three-level heterogeneous structure: (1) 30 mL of commercially available carbon nanotube dispersion was concentrated at 60°C for 4 h to obtain a carbon nanotube dispersion with a mass percentage concentration of 2%. The carbon nanotube dispersion was evenly coated on the surface of the carbon nanotube fiber, and then frozen with liquid nitrogen. After freezing, it was freeze-dried at -60°C and 10 Pa vacuum for 15 h to obtain a layered fiber electrode with an aerogel shell structure. (2) 2 g of PVDF-HFP was weighed and added to 10 g of DMF, and stirred at 80°C for 1 h to dissolve, obtaining a solution with a mass percentage concentration of about 16%. After cooling, 10 g of [EMIM][TFSI] was added to the above solution, and then mixed and stirred for 10 min to obtain a PVDF-HFP / [EMIM][TFSI] mixed solution. The PVDF-HFP / [EMIM][TFSI] mixed solution was evenly coated on the surface of the layered fiber electrode and dried at room temperature for 5 h to obtain a highly sensitive capacitive pressure sensing fiber with a three-level heterogeneous structure.

[0046] The high-sensitivity capacitive pressure sensing fiber with three-level heterostructure was scanned by electron microscope. Figure 1 As shown. Figure 1 It can be seen that the diameter of the highly sensitive capacitive pressure sensing fiber with a three-level heterogeneous structure is 345 μm; the diameter of the core layer is 145 μm, the thickness of the middle layer is 85 μm, and the thickness of the outer layer is 15 μm. The porous aerogel electrode layer has an axially arranged honeycomb pore structure with an average pore diameter of 9.4 μm and a mass density of 0.059 g cm -3 .

[0047] The pressure sensing performance of the high-sensitive capacitive pressure sensing fiber with a three-level heterostructure was tested: two high-sensitive capacitive pressure sensing fibers with a three-level heterostructure were placed crosswise and overlapped to form a pressure sensor. Then, gradually increasing pressure was applied from the top while recording the real-time capacitance changes. The results are as follows: Figure 2 As shown. Figure 2 It can be seen that the high-sensitive capacitive pressure sensing fiber with a three-level heterogeneous structure has excellent pressure sensing performance. Under a pressure below 20kPa, the average sensitivity of the pressure sensor composed of the cross-overlapping high-sensitive capacitive pressure sensing fibers with a three-level heterogeneous structure reaches 152.3kPa. -1 , reaching 69.4kPa in the range of 20-300kPa -1 , reaching 37.1kPa at pressures in the range of 300-630kPa -1 Under high pressure (>630kPa), the pressure sensor exhibits a nearly linear response with a sensitivity of 5.61kPa. -1. The sensing range is up to 1200kPa. Due to the unique layered structure of the highly sensitive capacitive pressure sensing fiber with a three-level heterogeneous structure, the pressure sensor composed of cross-overlap placement can achieve a fast capacitive response. The sensor has a response time of only 70ms. The results are as follows Figure 3 A tiny weight of 4 mg is placed on a pressure sensor composed of highly sensitive capacitive pressure sensing fibers with a three-level heterogeneous structure, which are placed cross-overlappingly. Due to the high sensitivity of the fiber pressure sensor, it can produce a significant capacitive response. The results are shown in Figure 4 The above excellent pressure sensing performance is attributed to the synergistic optimization of the porous electrode structure and the sensing mechanism. The sensing mechanism of the high-sensitive capacitive pressure sensing fiber with a three-level heterogeneous structure of the present invention is as follows Figure 5 As shown in Figure 1, under applied pressure, the dielectric layer thickness (d) decreases while the effective contact area (A) between the fibers increases, leading to a change in the capacitance of the fiber pressure sensor. More importantly, the sensing fiber's tertiary heterostructure enhances the fiber's deformability by bending or buckling the porous cell walls under compression, thereby regulating the pore channel spacing, further improving the sensitivity of the fiber pressure sensor. Furthermore, the double layer formed at the interface between the dielectric layer containing the ionic liquid and the electrode produces atomic-scale charge separation (~1 nm spacing), causing the sensing fiber to produce a large capacitance change under mechanical perturbation.

[0048] The highly sensitive capacitive pressure sensing fiber with a three-level heterogeneous structure was subjected to a tensile stress-strain test using a mechanical testing machine. The test results showed that the elongation at break was 15.8% and the breaking stress was 35 MPa.

[0049] The compressive stress and strain test of the highly sensitive capacitive pressure sensing fiber with three-level heterogeneous structure was carried out by a mechanical testing machine. The results are as follows: Figure 6 As shown. Figure 6 It can be seen that the fiber has excellent resilience (stress retention rate is 92.1% at 20% strain, and it can withstand more than 1,000 compression cycles). This is attributed to the fact that the pores arranged along the fiber axis in the porous aerogel layer can effectively distribute the stress throughout the porous framework. Furthermore, the supporting rebound effect of the porous aerogel electrode layer is conducive to achieving long-term stable and highly sensitive sensing. The sensing stability of the fiber was evaluated by recording the real-time capacitance changes during the cyclic compression and release process. The results are as follows: Figure 7 As shown, from Figure 7 It can be seen that the fiber pressure sensor can achieve a stable capacitance response during 2000 compression and release cycles. The structural stability and fatigue resistance of the fiber were evaluated by testing the change in conductivity during the bending cycle. Figure 8 As shown. Figure 8It can be seen that the fiber maintains stable conductivity after being bent at 135° for 1000 times, with a conductivity retention rate of >70%.

[0050] Example 2

[0051] Highly sensitive capacitive pressure sensing fiber with a three-level heterogeneous structure: It has a coaxial three-level heterogeneous structure, which consists of a core layer, a middle layer, and an outer layer from the inside to the outside; the core layer is a graphene fiber electrode layer, the middle layer is a porous aerogel MXene electrode layer, and the outer layer is a PVA dielectric layer doped with [BMIM][TFSI].

[0052] Preparation of highly sensitive capacitive pressure sensing fiber with three-level heterogeneous structure: (1) Take 40mL of commercially available MXene dispersion and centrifuge it at 18000rpm for enrichment and redispersion to obtain a MXene dispersion with a mass percentage concentration of 50%. The MXene dispersion is evenly coated on the surface of the graphene fiber, and then it is frozen with liquid nitrogen. After freezing, it is freeze-dried at -40℃ and 90Pa vacuum for 12h to obtain a layered fiber electrode with an aerogel shell structure. (2) Weigh 2.5g of PVA and add it to 10g of DMF, stir it at 80℃ for 1h to dissolve it, and obtain a solution with a mass percentage concentration of 20%. After cooling, add 2.5g of [BMIM][TFSI] to the above solution, and then mix and stir for 10min to obtain a PVA / [BMIM][TFSI] mixed solution. The PVA / [BMIM][TFSI] mixed solution was evenly coated on the surface of the layered fiber electrode and dried at 40°C for 5 h to obtain a highly sensitive capacitive pressure sensing fiber with a three-level heterogeneous structure.

[0053] Example 3

[0054] Highly sensitive capacitive pressure sensing fiber with three-level heterogeneous structure: It has a coaxial three-level heterogeneous structure, which consists of a core layer, a middle layer, and an outer layer from the inside to the outside; the core layer is a gold fiber electrode layer, the middle layer is a porous aerogel carbon nanotube electrode layer, and the outer layer is a polyurethane dielectric layer doped with [EMIM][BF4].

[0055] Preparation of a highly sensitive capacitive pressure sensing fiber with a three-level heterogeneous structure: (1) 40 mL of commercially available carbon nanotube dispersion was concentrated at 90°C for 4 hours to obtain a carbon nanotube dispersion with a mass percentage concentration of 10%. The carbon nanotube dispersion was evenly coated on the surface of the gold fiber and then frozen with liquid nitrogen. After freezing, it was freeze-dried at -55°C and a vacuum of 25 Pa for 32 hours to obtain a layered fiber electrode with an aerogel shell structure. (2) 1.5 g of polyurethane was weighed and added to 10 g of DMF, and dissolved by stirring at 70°C for 1 hour to obtain a solution with a mass percentage concentration of approximately 13%. After cooling, 7.5 g of [EMIM][BF4] was added to the above solution, and then mixed and stirred for 10 minutes to obtain a polyurethane / [EMIM][BF4] mixed solution. The polyurethane / [EMIM][BF4] mixed solution was evenly coated on the surface of the layered fiber electrode and dried at 40°C for 12 hours to obtain a highly sensitive capacitive pressure sensing fiber with a three-level heterogeneous structure.

[0056] Example 4

[0057] Highly sensitive capacitive pressure sensing fiber with a three-level heterogeneous structure: It has a coaxial three-level heterogeneous structure, which consists of a core layer, a middle layer, and an outer layer from the inside to the outside; the core layer is a copper fiber electrode layer, the middle layer is a porous aerogel PEDOT:PSS electrode layer, and the outer layer is a PDMS dielectric layer doped with [BMIM][TFSI].

[0058] Preparation of a highly sensitive capacitive pressure sensing fiber with a three-level heterogeneous structure: (1) 30 mL of commercially available PEDOT:PSS dispersion was concentrated at 80°C for 6 h to obtain a PEDOT:PSS dispersion with a mass percentage concentration of 30%. The PEDOT:PSS dispersion was evenly coated on the surface of the copper fiber and then frozen in liquid nitrogen. After freezing, it was freeze-dried at -50°C and 60 Pa in a vacuum for 5 h to obtain a layered fiber electrode with an aerogel shell structure. (2) 2 g of PDMS was weighed and added to 10 g of DMF, and dissolved by stirring at 80°C for 1.5 h to obtain a solution with a mass percentage concentration of approximately 16%. After cooling, 2 g of [BMIM][TFSI] was added to the above solution, and then mixed and stirred for 10 min to obtain a PDMS / [BMIM][TFSI] mixed solution. The PDMS / [BMIM][TFSI] mixed solution was evenly coated on the surface of the layered fiber electrode and dried at 50°C for 5 h to obtain a highly sensitive capacitive pressure sensing fiber with a three-level heterogeneous structure.

[0059] The highly sensitive capacitive pressure sensing fiber with a three-level heterogeneous structure is woven. The actual weaving diagram is shown in the figure. Figure 9 As shown. Figure 9It can be seen that it can be combined with clothing or wristbands to realize wearable pressure monitoring, and has application potential in health monitoring, human-computer interaction and electronic skin.

[0060] In summary, the high-sensitive capacitive pressure sensing fiber with a three-level heterogeneous structure of the present invention is based on the synergistic double-electric layer enhancement mechanism of the porous structure, and adopts a three-level heterogeneous structure design: a flexible conductive fiber electrode core layer, a coaxial porous aerogel middle layer and an ionic liquid doped dielectric outer layer; wherein, the multi-level fiber electrode composed of the core layer and the middle layer significantly improves the effective sensing area under pressure through the dynamic contact area amplification effect; the double electric layer formed by the ionic dielectric layer and the electrode interface synergistically enhances the piezoelectric capacitor response strength; the anisotropic design of the aerogel pores gives the fiber excellent compressibility and fatigue resistance. The high-sensitive capacitive pressure sensing fiber with a three-level heterogeneous structure of the present invention has high sensitivity (the average sensitivity within the 20kPa pressure range reaches 152.3kPa -1 ), a wide pressure sensing range (sensing range up to 1200kPa) and a fast response time (70ms). A stable capacitive response (>2000 times) is achieved during the compression-release cycle. Based on the above characteristics, the highly sensitive capacitive pressure sensing fiber of the present invention is particularly suitable for high-precision pressure signal detection and shows good application prospects in the field of smart wearable technology.

[0061] The above description is only a specific embodiment of the present invention, not all embodiments. Any equivalent transformation of the technical solution of the present invention made by ordinary technicians in this field after reading the specification of the present invention is covered by the claims of the present invention.

Claims

1. A highly sensitive capacitive pressure sensing fiber with a three-level heterostructure, characterized in that: The high-sensitivity capacitive pressure sensing fiber with a three-level heterogeneous structure has a coaxial three-level heterogeneous structure, which comprises a core layer, a middle layer, and an outer layer from the inside to the outside; The core layer is a conductive fiber electrode layer with excellent flexibility, the middle layer is a porous aerogel electrode layer, and the outer layer is an elastic polymer dielectric layer doped with ionic liquid.

2. The highly sensitive capacitive pressure sensing fiber with a three-level heterostructure according to claim 1, characterized in that: The diameter of the highly sensitive capacitive pressure sensing fiber with a three-level heterogeneous structure is 50-900 μm; The diameter of the core layer is 20-200 μm, the thickness of the middle layer is 20-300 μm, and the thickness of the outer layer is 10-400 μm.

3. The highly sensitive capacitive pressure sensing fiber with a three-level heterostructure according to claim 1, characterized in that: The conductive fiber is selected from at least one of carbon nanotube fiber, MXene fiber, graphene fiber, copper fiber and gold fiber.

4. The highly sensitive capacitive pressure sensing fiber with a three-level heterostructure according to claim 1, characterized in that: The material of the porous aerogel electrode layer is a conductive carbene material or a conductive polymer; the conductive carbene material is selected from at least one of graphene, reduced graphene oxide, MXene and carbon nanotubes; the conductive polymer is selected from at least one of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid, polypyrrole, polyaniline, polythiophene, polynaphthylamine and poly(m-phenylenediamine); The porous aerogel electrode layer has an axially arranged honeycomb pore structure with an average pore size of 5-20 μm and a mass density of 0.01-0.1 g cm -3 .

5. The highly sensitive capacitive pressure sensing fiber with a three-level heterostructure according to claim 1, characterized in that: The ionic liquid is selected from at least one of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium tetrafluoroborate, and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide; The elastic polymer is selected from at least one of polydimethylsiloxane, polyvinyl alcohol, polyvinylidene fluoride, poly(vinylidene fluoride-co-trifluoroethylene), poly(vinylidene fluoride-co-hexafluoropropylene), polyurethane, thermoplastic polyurethane, and Ecoflex; The mass ratio of the elastic polymer to the ionic liquid is 1:(0.5-8).

6. The method for preparing a highly sensitive capacitive pressure sensing fiber having a three-level heterogeneous structure according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) preparing a dispersion of a porous aerogel electrode layer material with a mass percentage concentration of 0.1-50%, and uniformly coating the dispersion on the surface of the conductive fiber, then freezing the conductive fiber with the coating layer in liquid nitrogen, and freeze-drying the frozen conductive fiber to obtain a layered fiber electrode with an aerogel shell structure; (2) The elastic polymer is dissolved in a solvent to form a solution with a mass percentage concentration of 8-25%, the ionic liquid is added to the above solution and mixed evenly to obtain an elastic polymer / ionic liquid mixed solution, the elastic polymer / ionic liquid mixed solution is evenly coated on the surface of a layered fiber electrode with an aerogel shell structure, and after drying, a highly sensitive capacitive pressure sensing fiber with a three-level heterogeneous structure is obtained.

7. The preparation method according to claim 6, characterized in that The freeze-drying temperature in step (1) is -40°C to (-60)°C, the vacuum degree is 5-100 Pa, and the time is 5-36 hours.

8. The preparation method according to claim 6, characterized in that The solvent in step (2) is selected from at least one of N,N-dimethylformamide, dimethyl sulfoxide, ethanol and acetone; Preferably, the step (2) of dissolving the elastic polymer in a solvent to form a solution with a mass percentage concentration of 8-25% is specifically as follows: adding the elastic polymer to the solvent and stirring at 60-120° C. for 20-90 minutes to obtain a solution with a mass percentage concentration of 8-25%; Preferably, the mass ratio of the elastic polymer to the ionic liquid in step (2) is 1:(0.5-8); Preferably, the drying temperature in step (2) is 0-60° C., and the drying time is 3-24 h.

9. Use of the highly sensitive capacitive pressure sensing fiber with a tertiary heterostructure according to any one of claims 1 to 5 or the highly sensitive capacitive pressure sensing fiber with a tertiary heterostructure prepared by the preparation method according to any one of claims 6 to 8 in flexible wearable electronic fabrics.

10. Application of the highly sensitive capacitive pressure sensing fiber with a three-level heterostructure according to any one of claims 1 to 5 or the highly sensitive capacitive pressure sensing fiber with a three-level heterostructure prepared by the preparation method according to any one of claims 6 to 8 in flexible electronic devices, electronic skin, medical monitoring products and human-computer interaction products.

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