A flexible conductive composite fiber material having a pleated structure and a method for preparing the same

Abstract

The application discloses a flexible conductive composite fiber material with a pleat structure and a preparation method thereof, and belongs to the technical field of composite materials. The method is as follows: a fiber base is mechanically pre-stretched along the fiber direction, the pre-stretched fiber is placed in a two-dimensional inorganic material water dispersion liquid for treatment, a composite fiber is obtained, and then the two ends of the composite fiber are fixed on a collector for drying, so that the flexible conductive composite fiber material with the pleat structure is obtained. The application realizes the effective assembly method of the two-dimensional nanosheet layer material on the stretchable fiber base by constructing the pleat structure, so that the interface enhancement and macroscopic performance regulation of the electromagnetic shielding composite fiber are realized, a new idea for continuously processing the conductive composite fiber device is provided, and the application has a good application prospect in dynamic electromagnetic shielding regulation and fiber surface customization.

Description

Technical Field

[0001] This invention belongs to the technical field of composite materials, and particularly relates to a flexible conductive composite fiber material with a pleated structure and its preparation method. Background Technology

[0002] Compared to other conductive functionalized composite materials (such as aerogels, hydrogels, and thin films), fiber-based wearable functional devices exhibit superior flexibility, adaptability, and resilience, thus attracting widespread attention. Currently, researchers have developed various technical routes for functionalized fiber molding and assembly, such as electrospinning, wet spinning, surface coating, and vacuum-assisted filtration. Furthermore, composite fiber assembly forms include blended composite fibers and core-shell composite fibers. Traditional composite fiber designs often neglect the structural enhancement effect on overall performance, and still suffer from drawbacks such as poor interfacial bonding strength, large amounts of functional fillers, and a limited range of achievable performance characteristics. Therefore, developing a universal, simple, and efficient molding process is of great significance for the functionalization and practical application of fiber devices.

[0003] Inspired by self-folded biomaterials (such as flower petals, cerebral cortex, and human skin), constructing multi-dimensional interlocking folded structures on the surface of fiber substrates can effectively enhance the interfacial bonding of composite fibers. Furthermore, folds of varying amplitudes allow for flexible control of their macroscopic properties. For example, Chinese patent document CN 112941666A discloses a conductive fiber with a surface polypyrrole folded core-shell structure, its preparation method, and its application. This method utilizes the volume shrinkage during gel fiber drying to create folds in the surface polypyrrole, thereby increasing the specific surface area of ​​the conductive fiber and improving its electrochemical cycling performance. Chinese patent document CN 115726060A discloses a gel fiber with a folded surface structure, its preparation method, and its application. This method uses argon or nitrogen plasma to treat the resin coating on the fiber substrate surface. The resulting gradient modulus in the coating thickness direction causes spontaneous formation of a ring-shaped folded structure along the fiber axis. Both methods are based on folded structures to prepare conductive composite fibers and achieve improved related properties. However, these methods still have some problems, such as: (1) from the perspective of microstructure, the range of wrinkles produced is small, and the contact area and interlocking form between wrinkles are difficult to achieve a high-strength interface bonding effect; (2) the traditional wrinkle construction method lacks simple, efficient, universal and continuous processing potential, and it is difficult to realize Chinese production applications; (3) its micro-wrinkle structure does not have a significant effect on improving and controlling the macroscopic properties of composite fibers.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The present invention aims to provide a flexible conductive composite fiber material with a wrinkled structure and its preparation method. The method achieves interfacial enhancement and performance regulation of the composite fiber through the construction of the wrinkled structure. A core-shell structure is established by constructing an elastic, stretchable fiber substrate and a rigid outer layer, creating a system with a significant modulus difference between the inner and outer layers. During natural drying, the dehydration effect drives the composite fiber to shrink and curl in multiple dimensions, forming a fiber material with a wrinkled structure. Specifically, silk fibroin fibers loaded with two-dimensional inorganic nanosheets shrink inward as moisture evaporates, causing the outer two-dimensional inorganic nanosheets to form a relatively small-amplitude wrinkled conductive network around the fiber. Simultaneously, under the action of capillary force, the outer layer of the two-dimensional inorganic material buckles, forming a neatly arranged parallel louver-like wrinkled structure along the fiber axis. The superimposed effect of these two formation mechanisms creates an interlaced and overlapping layered wrinkled structure, thereby improving the interfacial interaction and conductivity of the composite fiber.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention provides a method for preparing a flexible conductive composite fiber material with a pleated structure, comprising the following steps:

[0008] S1: Mechanically pre-stretch the fiber matrix along the fiber direction.

[0009] Optionally, the pre-stretching is performed using a bidirectional stretching device.

[0010] Optionally, the fiber matrix includes one or more of regenerated silk fibroin fiber matrix, polyurethane fiber matrix, or polyvinylidene fluoride fiber matrix.

[0011] Preferably, the method for preparing the regenerated silk fibroin fiber matrix is ​​as follows: degumming silkworm cocoons, drying them at room temperature, dissolving them to obtain a spinning solution, injecting it into a coagulation bath for spinning, and then replacing the solvent in deionized water to obtain the final product.

[0012] Optionally, the degumming of the silkworm cocoons is performed by placing the silkworm cocoons in boiling sodium bicarbonate water for 20-40 minutes.

[0013] Optionally, the dissolution is performed in a formic acid-calcium chloride system.

[0014] Optionally, the coagulation bath is an aqueous solution of ethanol.

[0015] Optionally, the draw ratio of the spinning process is 0.94-0.96.

[0016] Preferably, the pre-stretch ratio is 1-3 times.

[0017] S2: The pre-stretched fibers are placed in an aqueous dispersion of two-dimensional inorganic materials for treatment to obtain composite fibers.

[0018] Optionally, the two-dimensional inorganic material includes one or more of MXene (two-dimensional transition metal carbon / nitride) nanosheets, GO (graphene oxide) nanosheets, or TMD (transition metal chalcogenide) nanosheets, which have the characteristics of abundant surface contact sites and excellent mechanical properties.

[0019] Furthermore, the concentration of the aqueous dispersion of the two-dimensional inorganic material is 5-25 mg / mL.

[0020] Preferably, the method for preparing the aqueous dispersion of MXene nanosheets includes: mixing LiF and HCl solutions to obtain a mixed solution, adding Ti3AlC2 powder and mixing evenly, stirring in a water bath at 30-45℃ for 36-48 hours, then adding deionized water and centrifuging to neutral, collecting the precipitate and adding water, then sonicating under an inert gas atmosphere, centrifuging and classifying, and taking the supernatant.

[0021] Preferably, before placing the pre-stretched fibers in an aqueous dispersion of the two-dimensional inorganic material, the pre-stretched fibers are first placed in a 0.5-1 mg / mL PEI (polyethyleneimine) aqueous solution for surface modification. The abundant surface end groups and positive charge properties of PEI alter the surface chemical properties of the polymer fiber matrix.

[0022] The intrinsic surface of the fiber matrix possesses hydrophilic polar end groups, enabling it to assemble with outer functional materials to form relatively small-amplitude wrinkled structures. However, by introducing more polar end groups into its surface through modification, the surface can assemble with more two-dimensional nanosheets, resulting in relatively large-amplitude wrinkled structures. Therefore, the surface wrinkled structure in this invention can be controllably constructed, thereby regulating its macroscopic properties.

[0023] In particular, the regenerated silk fibroin fiber matrix contains a large number of hydrophilic amino acids and calcium ions, which can capture a large number of water molecules, causing the fiber matrix to expand and thus change the orientation of the pleated structure and the conductive network, thereby realizing the conversion of dynamic electromagnetic shielding performance.

[0024] S3: Fix both ends of the composite fiber to the collector and dry it to obtain the final product.

[0025] Preferably, the drying process is natural drying. During the drying process, both ends of the fiber should be fixed to the collector, causing the fiber to undergo peristaltic contraction and form a specific wrinkled structure. Furthermore, under external load, a certain orientation will occur within the fiber, further improving the mechanical properties of the conductive composite fiber.

[0026] After pre-stretching, the modified fiber matrix undergoes further treatment in a specific two-dimensional inorganic material aqueous dispersion according to the target properties. The loading effect of the two-dimensional inorganic material is related to the concentration of its aqueous dispersion and the treatment time.

[0027] The fiber matrix loaded with two-dimensional inorganic nanosheets shrinks inward as moisture evaporates, causing the outer nanosheets to form a relatively small-amplitude folded conductive network around the fibers. Simultaneously, under capillary forces, the outer layer of the nanosheets buckles, forming a neatly arranged parallel louver-like fold structure along the fiber axis. The combined effect of these two formation mechanisms produces an interlaced and interconnected layered fold structure, thereby improving the interfacial interactions and conductivity of the composite fibers.

[0028] The present invention also provides a flexible conductive composite fiber material with a pleated structure prepared by the aforementioned preparation method.

[0029] Compared with existing technologies, this invention provides a universal, simple, and continuous method for preparing conductive composite fiber materials with a wrinkled structure. On the one hand, it solves the problems of poor interfacial bonding, large amount of functional filler, and limited range of achievable performance in traditional load-bearing composite fibers; on the other hand, it achieves effective control of macroscopic performance through microscopic surface structure design and can dynamically adjust electromagnetic shielding performance according to changes in external humidity.

[0030] Specifically, the pre-stretched polymer-based fiber matrix undergoes surface modification, and its abundant polar end groups and opposite charge can effectively combine with two-dimensional inorganic nanosheets (MXene, GO, etc.). As moisture is removed during natural drying, the composite fiber is driven to shrink in multiple dimensions, including the axial and circumferential directions, forming a multi-level interlocking fold structure and constructing a good conductive network on the fiber surface.

[0031] It is worth noting that during the formation of the wrinkled structure using this method, in addition to interactions such as hydrogen bonding and electrostatic attraction, there are also capillary forces generated during dehydration between the functional material and the fiber matrix. The synergistic effect of these multiple interactions forms a strong bonding interface for the composite fiber. Simultaneously, the interlocking wrinkled structure provides numerous stress points and contact areas, effectively preventing the conductive material from detaching during application. By adjusting the surface modification effect of the fiber matrix and the loading concentration of the two-dimensional nanosheets, the macroscopic properties of the composite fiber can be flexibly controlled. The composite fiber prepared based on this method exhibits a tunable wrinkled structure, endowing it with excellent conductivity (1125 S / cm), electromagnetic shielding performance (32 dB), and mechanical properties (214 MPa, 15 MJ / m²). 3This invention improves the bonding strength between the fiber and the interface. Furthermore, due to the excellent moisture-trapping capabilities of the silk fibroin fiber matrix, the pleated structure of this fiber exhibits dynamic changes with moisture, thereby achieving adjustable electromagnetic shielding properties. This invention provides a new approach for the continuous processing of conductive composite fiber devices, showing promising application prospects in dynamic electromagnetic shielding adjustment and fiber surface customization. Therefore, the flexible conductive composite fiber material can be widely used in fields such as conductive, dynamic electromagnetic shielding, or energy storage fiber devices. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0033] Figure 1 The images show scanning electron microscope (SEM) images, atomic force microscope (AFM) images, and scanning height curves of regenerated silk fibroin fiber (RSF), RSF / MXene (RM) fiber prepared in Example 1, and RSF / PEI / MXene (RPM) fiber prepared in Example 6. Specifically, Figure a1 is an SEM image of regenerated silk fibroin fiber (RSF), Figure b1 is an SEM image of RM fiber, Figure c1 is an SEM image of RPM fiber, Figure a2 is an AFM image of regenerated silk fibroin fiber (RSF), Figure b2 is an AFM image of RM fiber, Figure c2 is an AFM image of RPM fiber, Figure a3 is a scanning height curve of regenerated silk fibroin fiber (RSF), Figure b3 is a scanning height curve of RM fiber, and Figure c3 is a scanning height curve of RPM fiber.

[0034] Figure 2 a is a mechanical curve of regenerated silk fibroin fiber (RSF), RM fiber prepared in Example 1, and RPM fiber prepared in Example 6. Figure 2 b is a comparison diagram of the strength and toughness of regenerated silk fibroin fiber (RSF), RM fiber prepared in Example 1, and RPM fiber prepared in Example 6.

[0035] Figure 3 These are cross-sectional scanning electron microscope images of the RPM fibers prepared in Example 6 at different magnifications.

[0036] Figure 4a represents the electrical conductivity of composite fibers prepared with different concentrations of MXene or GO nanosheet dispersions. Unless otherwise specified, all are MXene dispersions. Specifically, these are the RPM fibers of Example 4 (dispersion concentration 5 mg / mL), the RPM fibers of Example 5 (dispersion concentration 10 mg / mL), the RM fibers of Example 9 (dispersion concentration 15 mg / mL), the RPG fibers of Example 8 (GO dispersion concentration 10 mg / mL), the RPM fibers of Example 6 (dispersion concentration 15 mg / mL), the RPM fibers of Example 7 (dispersion concentration 20 mg / mL), and the RPM fibers of Example 10 (dispersion concentration 25 mg / mL). Figure 4 b represents the electromagnetic shielding effectiveness curves of RSF fiber, RM fiber prepared in Example 9, and RPM fiber prepared in Example 6. Figure 4 c represents the electromagnetic shielding effectiveness of the RPM fibers prepared in Example 6 at different stacking layers.

[0037] Figure 5 a represents the electromagnetic shielding performance curves of the RPM fiber prepared in Example 6 under different humidity conditions; Figure 5 b represents the dynamic electromagnetic shielding performance of the RPM fiber prepared in Example 6 under multiple cyclic tests. Detailed Implementation

[0038] The embodiments of the present invention will be described in detail below with reference to specific examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0039] In the following embodiments, the electromagnetic shielding test method uses the waveguide method to test the electromagnetic shielding effectiveness in the X-band.

[0040] Example 1

[0041] A method for preparing a flexible conductive composite fiber material with a pleated structure:

[0042] (1) Silkworm cocoons were cut into small pieces and placed in boiling water containing 0.5 wt% sodium bicarbonate for degumming for 30 minutes. This process was repeated twice until excess sericin coating was removed. Then, the room-temperature dried silk fibroin fibers were dissolved in a 12% (w / v) formic acid-calcium chloride system to obtain a 25% (w / v) spinning solution. Subsequently, the degassed spinning solution was placed in a syringe and squeezed through a 23G nozzle (approximately 0.35 mm inner diameter) into a coagulation bath containing ethanol and water at a volume ratio of 4:1. The gelled silk fibroin fibers were rapidly formed with a draw ratio of 0.95. They were then transferred to deionized water for solvent diffusion and exchange to obtain the fiber matrix for further processing.

[0043] (2) Add 8g of LiF powder to 100mL of 9M hydrochloric acid to obtain mixed solution one. Add 5g of Ti3AlC2 powder slowly to mixed solution one to obtain mixed solution two. Place mixed solution two in a 40℃ water bath and stir magnetically for 40 hours. Then add deionized water and centrifuge to wash until neutral. Collect the precipitate, add water, and sonicate under argon atmosphere for 1 hour. Centrifuge and classify, take the supernatant to obtain MXene aqueous dispersion, and adjust the concentration of MXene aqueous dispersion to 5mg / mL.

[0044] (3) The fiber matrix obtained in step (1) is mechanically pre-stretched using a biaxial stretching device with a stretching ratio of 2. The stretched fiber is then immersed in the 5 mg / mL MXene aqueous dispersion obtained in step (2) for 5 minutes. Finally, the two ends of the obtained composite fiber are fixed on a collecting roller and allowed to dry naturally at room temperature, causing the fiber to undergo peristaltic shrinkage to form a specific wrinkled structure, thus obtaining the final product.

[0045] Example 2

[0046] A method for preparing a flexible conductive composite fiber material with a pleated structure:

[0047] Steps (1) and (2) are the same as in Example 1;

[0048] (3) The fiber matrix obtained in step (1) is mechanically pre-stretched using a biaxial stretching device with a stretching ratio of 2. The stretched fibers are then transferred to a PEI aqueous solution with a concentration of 0.5 mg / mL for surface modification for 1 minute. After cleaning off the excess PEI from the fiber surface, the fibers are transferred to a 5 mg / mL MXene aqueous dispersion obtained in step (2) for immersion for 5 minutes. Finally, the two ends of the obtained composite fiber are fixed to a collecting roller and allowed to dry naturally at room temperature, causing the fiber to undergo peristaltic shrinkage to form a specific wrinkled structure, thus obtaining the final product.

[0049] Example 3

[0050] A method for preparing a flexible conductive composite fiber material with a pleated structure:

[0051] Steps (1) and (2) are the same as in Example 1;

[0052] (3) The fiber matrix obtained in step (1) is mechanically pre-stretched using a biaxial stretching device with a stretching ratio of 3 times. The stretched fiber is then transferred to a PEI aqueous solution with a concentration of 0.5 mg / mL for surface modification for 1 minute. After cleaning off the excess PEI from the fiber surface, the fiber is transferred to the MXene aqueous dispersion obtained in step (2) and immersed for 5 minutes. Finally, the two ends of the obtained composite fiber are fixed on a collecting roller and allowed to dry naturally at room temperature, causing the fiber to undergo peristaltic shrinkage to form a specific wrinkled structure, thus obtaining the final product.

[0053] Example 4

[0054] A method for preparing a flexible conductive composite fiber material with a pleated structure:

[0055] Steps (1) and (2) are the same as in Example 1;

[0056] (3) The fiber matrix obtained in step (1) is mechanically pre-stretched using a biaxial stretching device with a stretching ratio of 3 times. The stretched fiber is then transferred to a PEI aqueous solution with a concentration of 1 mg / mL for surface modification for 1 minute. After cleaning off the excess PEI from the fiber surface, the fiber is transferred to a 5 mg / mL MXene aqueous dispersion obtained in step (2) for immersion for 5 minutes. Finally, the two ends of the obtained composite fiber are fixed to a collecting roller and allowed to dry naturally at room temperature, causing the fiber to undergo peristaltic shrinkage to form a specific wrinkled structure, thus obtaining the final product.

[0057] Example 5

[0058] A method for preparing a flexible conductive composite fiber material with a pleated structure:

[0059] Step (1) is the same as in Example 1; Step (2) differs from Example 1 in that the concentration of MXene aqueous dispersion is adjusted to 10 mg / mL.

[0060] (3) The fiber matrix obtained in step (1) is mechanically pre-stretched using a biaxial stretching device with a stretching ratio of 3 times. The stretched fiber is then transferred to a PEI aqueous solution with a concentration of 1 mg / mL for surface modification for 1 minute. After cleaning off the excess PEI from the fiber surface, the fiber is transferred to the MXene aqueous dispersion obtained in step (2) and immersed for 5 minutes. Finally, the two ends of the obtained composite fiber are fixed on a collecting roller and allowed to dry naturally at room temperature, causing the fiber to undergo peristaltic shrinkage to form a specific wrinkled structure, thus obtaining the final product.

[0061] Example 6

[0062] A method for preparing a flexible conductive composite fiber material with a pleated structure:

[0063] Step (1) is the same as in Example 1; Step (2) differs from Example 1 in that the concentration of MXene aqueous dispersion is adjusted to 15 mg / mL.

[0064] (3) The fiber matrix obtained in step (1) is mechanically pre-stretched using a biaxial stretching device with a stretching ratio of 3 times. The stretched fiber is then transferred to a PEI aqueous solution with a concentration of 1 mg / mL for surface modification for 1 minute. After cleaning off the excess PEI from the fiber surface, it is transferred to the MXene aqueous dispersion obtained in step (2) and immersed for 5 minutes. Finally, the two ends of the obtained composite fiber are fixed on a collecting roller and allowed to dry naturally at room temperature, causing the fiber to undergo peristaltic shrinkage to form a specific wrinkled structure, thus obtaining the final product.

[0065] Example 7

[0066] A method for preparing a flexible conductive composite fiber material with a pleated structure:

[0067] Step (1) is the same as in Example 1; Step (2) differs from Example 1 in that the concentration of MXene aqueous dispersion is adjusted to 20 mg / mL.

[0068] (3) The fiber matrix obtained in step (1) is mechanically pre-stretched using a biaxial stretching device with a stretching ratio of 3 times. The stretched fibers are then transferred to a PEI aqueous solution with a concentration of 1 mg / mL for surface modification for 1 minute. After cleaning off the excess PEI from the fiber surface, the fibers are transferred to a 20 mg / mL MXene aqueous dispersion obtained in step (2) for immersion for 5 minutes. Finally, the two ends of the obtained composite fiber are fixed to a collecting roller and allowed to dry naturally at room temperature, causing the fiber to undergo peristaltic shrinkage to form a specific wrinkled structure, thus obtaining the final product.

[0069] Example 8

[0070] A method for preparing a flexible conductive composite fiber material with a pleated structure:

[0071] Step (1) is the same as in Example 1;

[0072] (2) The fiber matrix obtained in step (1) is mechanically pre-stretched using a biaxial stretching device with a stretching ratio of 3 times. The stretched fibers are then transferred to a PEI aqueous solution with a concentration of 1 mg / mL for surface modification for 1 minute. After cleaning off the excess PEI from the fiber surface, the fibers are transferred to a GO aqueous dispersion with a concentration of 10 mg / mL for immersion for 5 minutes. Finally, the ends of the obtained composite fibers are fixed to a collecting roller, and after reduction with hydrobromic acid, they are allowed to dry naturally at room temperature, causing the fibers to undergo peristaltic shrinkage and form a specific wrinkled structure, thus obtaining the final product.

[0073] Example 9

[0074] A method for preparing a flexible conductive composite fiber material with a pleated structure:

[0075] Step (1) is the same as in Example 1; Step (2) differs from Example 1 in that the concentration of MXene aqueous dispersion is adjusted to 15 mg / mL.

[0076] (3) The fiber matrix obtained in step (1) is mechanically pre-stretched using a biaxial stretching device with a stretching ratio of 3 times; it is then soaked in the 15 mg / mL MXene aqueous dispersion obtained in step (2) for 5 minutes. Finally, the two ends of the obtained composite fiber are fixed on a collecting roller and allowed to dry naturally at room temperature, causing the fiber to undergo peristaltic shrinkage to form a specific wrinkled structure, thus obtaining the final product.

[0077] Example 10

[0078] A method for preparing a flexible conductive composite fiber material with a pleated structure:

[0079] Step (1) is the same as in Example 1; Step (2) differs from Example 1 in that the concentration of MXene aqueous dispersion is adjusted to 25 mg / mL.

[0080] (3) The fiber matrix obtained in step (1) is mechanically pre-stretched using a biaxial stretching device with a stretching ratio of 3 times. The stretched fiber is then transferred to a PEI aqueous solution with a concentration of 1 mg / mL for surface modification for 1 minute. After cleaning off the excess PEI from the fiber surface, the fiber is transferred to the MXene aqueous dispersion obtained in step (2) and immersed for 5 minutes. Finally, the two ends of the obtained composite fiber are fixed on a collecting roller and allowed to dry naturally at room temperature, causing the fiber to undergo peristaltic shrinkage to form a specific wrinkled structure, thus obtaining the final product.

[0081] Table 1. Performance comparison of the composite fiber materials prepared in Examples 1-10

[0082]

[0083] As shown in Table 1, the higher the pre-stretch ratio of the silk fibroin fiber matrix, the better the comprehensive mechanical properties of the composite fiber. The introduction of PEI can enhance the conductivity of the fiber, with the best concentration of MXene dispersion being 15 mg / mL. Its electromagnetic shielding performance also reaches the optimal 32 dB, and it can be dynamically adjusted with changes in humidity.

[0084] Depend on Figure 1 a1、 Figure 1 b1 and Figure 1 c1 and Figure 1 a2、 Figure 1 b2 and Figure 1 As can be seen from c2, untreated silk fibroin fibers have a relatively smooth surface morphology. Loading with two-dimensional MXene nanosheets can increase the surface roughness of the silk fibroin fiber matrix, and PEI modification can further enhance this process. Figure 1 a3、 Figure 1 b3 and Figure 1 c3 are respectively Figure 1 a2、 Figure 1 b2 and Figure 1 The height scan curve of c2 reflects the roughness of the fiber surface.

[0085] Depend on Figure 2 As can be seen, the addition of two-dimensional MXene nanosheets can effectively enhance the mechanical properties of the silk fibroin matrix; Figure 2 a and Figure 2 b shows that, compared with the untreated wet spinning silk fibroin fiber, its mechanical strength and toughness are increased to 1.8 and 13.8 times respectively.

[0086] Depend on Figure 3 It can be seen that the composite fiber exhibits strong interfacial bonding after tensile fracture, and the MXene conductive functional layer is still completely covered on the surface of the fiber matrix. This further illustrates that the overlapping and interlocking pleated structure effectively enhances the interface of the composite fiber.

[0087] Depend on Figure 4 a and Figure 4 As can be seen from b, the prepared RPM composite fiber exhibits excellent conductivity (1125 S / cm) and electromagnetic shielding performance (32 dB); Figure 4 As can be seen from c, its electromagnetic shielding performance increases with the increase of the number of fiber layers.

[0088] Depend on Figure 5As can be seen, based on the sensitive response of the silk fibroin fiber matrix to water vapor, the prepared RPM fiber exhibits dynamic electromagnetic shielding performance (12-32dB) with changes in external humidity, thus realizing the functional adjustment of electromagnetic shielding on / off for the fiber substrate; furthermore, by Figure 5 As can be seen from b, the switchable dynamic shielding performance of this composite fiber maintains good stability under multiple cycles, providing possibilities for subsequent practical applications.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

[0090] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are meant to be within the scope of the invention and form different embodiments. For example, in the foregoing claims, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of the invention and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A method for preparing a flexible conductive composite fiber material with a pleated structure, characterized in that, Includes the following steps: S1: The fiber matrix is ​​mechanically pre-stretched along the fiber direction using a biaxial stretching device; S2: First, the pre-stretched fibers are placed in a 0.5-1 mg / mL PEI aqueous solution for surface modification, and then the modified fibers are placed in an aqueous dispersion of MXene nanosheets for treatment to obtain composite fibers; S3: Fix both ends of the composite fiber to the collector and dry it to obtain the final product; In step S1, the fiber matrix is ​​a regenerated silk fibroin fiber matrix; The method for preparing the regenerated silk fibroin fiber matrix is ​​as follows: degumming silkworm cocoons, drying them at room temperature, dissolving them to obtain a spinning solution, injecting it into a coagulation bath for spinning, and then replacing the solvent in deionized water to obtain the final product. The process of degumming the silkworm cocoons involves placing the silkworm cocoons in boiling sodium bicarbonate water for degumming. The dissolution is in the formic acid-calcium chloride system; The coagulation bath is an aqueous solution of ethanol; The draw ratio of the spun yarn is 0.94-0.96; In step S1, the pre-stretch ratio is 1-3 times; The concentration of the aqueous dispersion of the MXene nanosheets is 15-25 mg / mL.

2. The preparation method according to claim 1, characterized in that, In step S2, the method for preparing the aqueous dispersion of MXene nanosheets includes: mixing LiF and HCl solutions to obtain a mixed solution, adding Ti3AlC2 powder and mixing evenly, stirring in a water bath at 30-45 ℃, then adding deionized water and centrifuging to neutral, collecting the precipitate and adding water, then sonicating under an inert gas atmosphere, centrifuging and classifying, and taking the supernatant to obtain the solution.

3. The preparation method according to claim 1, characterized in that, In step S3, the drying process is natural drying.

4. A flexible conductive composite fiber material with a pleated structure prepared by the preparation method according to any one of claims 1-3.

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