Bacterial cellulose / silver nanowire / MXene composite conductive film and preparation method thereof

Abstract

The invention discloses a bacterial cellulose / silver nanowire / MXene composite conductive film and a preparation method thereof, and relates to the technical field of flexible conductive materials. The composite film comprises a bacterial cellulose substrate, an MXene conductive layer and a silver nanowire conductive network layer. The preparation method comprises the following steps: S1, preparing bacterial cellulose dispersion liquid; s2, preparation of an MXene dispersion liquid; s3, preparing a silver nanowire dispersion liquid; and S4, preparing the composite film. The composite film with a Janus structure is prepared through a vacuum-assisted layer-by-layer filtering process, and the composite film has high mechanical performance, low square resistance, excellent electromagnetic interference shielding effectiveness, rapid Joule heating performance and excellent environmental stability and mechanical durability. The problem that an existing flexible electromagnetic shielding material is difficult to consider ultrathin performance, high flexibility, strong mechanical performance and multifunctional integration is solved, and the flexible electromagnetic shielding material has wide application prospects in the fields of electromagnetic shielding, flexible electronic devices, wearable heaters and the like.

Description

Technical Field

[0001] This invention relates to the field of flexible conductive materials technology, specifically to a bacterial cellulose / silver nanowire / MXene composite conductive film and its preparation method. Background Technology

[0002] Electromagnetic wave technology is widely used in numerous fields, including wireless communication, surveillance radar, remote control, positioning systems, and medical services. However, electromagnetic radiation and pollution problems are becoming increasingly prominent. Electromagnetic radiation not only causes mutual interference between devices and reduces signal integrity, but can also cause irreversible damage to electronic devices. Traditional electromagnetic shielding materials, such as metal plates, metal meshes, and conductive coatings, have relatively stable and reliable shielding performance. Among them, metal plates such as copper and aluminum can effectively suppress multi-band electromagnetic waves, with significant and stable shielding effects; metal meshes and conductive coatings have certain advantages in terms of lightweighting and can meet the surface bonding requirements of complex structures to a certain extent. However, metal materials generally have high density and poor flexibility, making it difficult to adapt to the requirements of curved integration or lightweight applications. In addition, the shielding effectiveness of metal meshes is relatively limited, and conductive coatings often require a large coating thickness, leading to an increase in the overall thickness of the device. Therefore, in the field of flexible electronics, traditional materials still have significant limitations in terms of ease of use and wearability. In summary, developing new shielding materials and structures that combine high-efficiency electromagnetic interference shielding capabilities, excellent flexibility, ultra-thin characteristics, and good mechanical strength remains an important technological challenge.

[0003] Janus composite films have attracted widespread attention due to their unique bi-sided asymmetric structure, which achieves highly efficient electromagnetic interference shielding while significantly reducing overall thickness, and possesses lightweight, thin, and durable mechanical properties. The asymmetric functional layers of the Janus structure can achieve functional synergy on different surfaces, promoting multifunctional integration and expanding its application potential in fields such as flexible electronics. Bacterial cellulose (BC), as a microbially synthesized nanocellulose, can form a nanofiber network with a high specific surface area and a three-dimensional interconnected porous structure, exhibiting excellent mechanical properties. This excellent flexibility and high strength endow Janus films with good bending ability and long-term stability, making them highly suitable for flexible electronic devices. Furthermore, the porous structure of BC helps to regulate the multiple reflections and absorptions of electromagnetic waves within the film, further enhancing electromagnetic shielding effectiveness. Such composite materials typically possess both excellent conductivity and high shielding efficiency. However, if prepared solely through physical blending of single functional materials or conductive fillers, it is often difficult to fully utilize the synergistic effects of the materials, limiting their long-term development potential in multifunctional integration.

[0004] The immense potential of MXene in electromagnetic shielding stems from its unique intrinsic defects and the exceptional polarization and charge transport capabilities endowed by its surface functional groups. MXene possesses excellent conductivity, good hydrophilicity, mechanical stability, and compatibility with organic molecules. This combination of properties makes it urgently needed for applications such as energy storage, strain sensing, and electromagnetic protection, making it an ideal material for advanced wearable and portable electronic devices. However, excessively high filler content often leads to decreased mechanical properties and increased processing difficulty, significantly limiting its practical application in flexible electronic devices.

[0005] In recent years, metallic nanowires (such as silver nanowires) and nanofibers have attracted widespread attention due to their excellent performance in flexible conductive electrodes and heating elements. Silver nanowires (AgNWs), with their high aspect ratio and excellent mechanical flexibility, are widely used as one-dimensional conductive materials in electromagnetic interference shielding and resistive Joule heating. However, the high contact resistance and poor connectivity of AgNWs limit their conductivity and functional efficiency. Notably, MXene nanosheets exhibit excellent conductive bridging ability and gap-filling effect in AgNW networks, significantly improving the continuity of conductive pathways. Simultaneously, the abundant oxygen-containing functional groups (such as –OH and –O) on the MXene surface can form hydrogen bonds with AgNWs, enhancing the interfacial bonding and structural integrity of the composite system. Therefore, integrating the advantages of silver nanowires and MXene to construct high-performance three-dimensional conductive networks, especially in developing highly integrated and multifunctional flexible composite films that combine excellent electromagnetic interference shielding and Joule heating, remains a current research challenge. Summary of the Invention

[0006] Therefore, this invention provides a bacterial cellulose / silver nanowire / MXene composite conductive film and its preparation method, to solve the problem of poor conductivity and mechanical properties of the film caused by physical blending and excessive filler addition during the preparation process in the prior art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: According to a first aspect of the present invention, a method for preparing a bacterial cellulose / silver nanowire / MXene composite conductive film is provided, comprising the following steps: S1. Preparation of bacterial cellulose dispersion: Add the bacterial cellulose blocks to deionized water in a certain proportion and disperse them by ultrasonication for 5-20 minutes to obtain a bacterial cellulose dispersion. Preparation of S2 and MXene dispersions: Hydrochloric acid and lithium fluoride were mixed at a volume-to-mass ratio of 10 mL: 1 g and used to etch Ti3ALC2. The reaction was carried out at 40 °C for 48 h. After the reaction was completed, the product was centrifuged and washed until neutral. Finally, the product was dispersed in water to obtain MXene dispersion. S3. Preparation of silver nanowire dispersion: Polyvinylpyrrolidone (PVP) with a molecular weight of 36 wDa and PVP with a molecular weight of 5.8 wDa were dissolved in ethylene glycol. The solutions were transferred to reaction flasks preheated to 130 °C and reacted using the polyol method for 5 h. Silver nitrate was then added and completely dissolved. Under vigorous stirring, 0.6 mmol / L ferric chloride / ethylene glycol solution was added to the above solution, and stirring was continued for 10 min. After stopping the reaction, the solution was allowed to stand for 3.5 h. The resulting precipitate was washed successively with acetone and ethanol, centrifuged at 1000–2000 rpm for 5 min, and then redispersed in 5 mg / mL PPVP solution to obtain a silver nanowire dispersion. S4. Preparation of composite thin films: a. Vacuum filter the bacterial cellulose dispersion obtained in step S1 to obtain a bacterial cellulose substrate; b. The MXene dispersion obtained in step S2 is redispersed with deionized water and deposited on a bacterial cellulose substrate by vacuum filtration to form an MXene conductive layer; c. The silver nanowire solution obtained in step S3 is redispersed with a 5 mg / mL polyvinylpyrrolidone solution, and deposited on the MXene conductive layer by vacuum filtration to form a silver nanowire conductive network layer, thereby obtaining a composite conductive film.

[0008] Further, in step S1, the concentration of the bacterial cellulose dispersion is 0.1 mg / ml.

[0009] Furthermore, in step S2, the concentration of the MXene dispersion is 5 mg / ml.

[0010] Further, in step S3, the mass-to-volume ratio of polyvinylpyrrolidone with a molecular weight of 36 wDa, polyvinylpyrrolidone with a molecular weight of 5.8 wDa, ethylene glycol, ferric chloride / ethylene glycol solution, and silver nitrate is 0.32 g: 0.32 g: 100 mL: 0.975 mL: 0.72 g.

[0011] Furthermore, in step S3, the concentration of the silver nanowire dispersion is 1 mg / mL.

[0012] Further, in step S4,a, the concentration of the redispersed silver nanowire dispersion is 0.10-0.50 mg / mL; in step S4,b, the concentration of the redispersed MXene dispersion is 1.0-4.0 mg / mL.

[0013] Furthermore, in step S4, the pressure of the filtration device is -0.1 MPa.

[0014] According to a second aspect of the present invention, a bacterial cellulose / silver nanowire / MXene composite conductive film is provided.

[0015] Furthermore, the film comprises a bacterial cellulose substrate, an MXene conductive layer, and a silver nanowire conductive network layer.

[0016] Furthermore, the bacterial cellulose substrate, the MXene conductive layer, and the silver nanowire conductive network layer are structured such that the bacterial cellulose substrate is covered with an MXene conductive layer, and the MXene conductive layer is covered with a silver nanowire conductive network layer.

[0017] The present invention has the following advantages: 1. Structural Innovation and Performance Synergy: A structure employing an MXene conductive layer synergistically coated with a PVP-encapsulated silver nanowire conductive protective layer is presented. This thin film structure uses a bacterial cellulose layer as a flexible substrate, MXene as an intermediate layer, and silver nanowires (AgNWs) as the surface layer, forming a composite system integrating high-efficiency electromagnetic interference shielding, electrothermal performance, and mechanical stability. By constructing an optimized bilayer conductive configuration with comprehensive hydrogen bonding interactions and an interconnected three-dimensional MXene-silver nanowire conductive network, strong interfacial bonding and excellent conductivity are achieved. This synergistic effect is crucial to the material's superior performance.

[0018] 2. Superior performance: The prepared film exhibits a tensile strength as high as 77.35 MPa and a sheet resistance as low as 0.429 Ω / sq. Electromagnetic interference shielding effectiveness reaches 52.3 dB. It can rapidly heat to 126°C within 60 seconds at 2.5V.

[0019] 3. Outstanding stability: After 100 adhesion tests, the sheet resistance remains almost unchanged; it exhibits excellent stability in a 3000s cyclic Joule heating test.

[0020] 4. Simple process, suitable for large-scale production: The vacuum filtration process adopted is simple to operate, low in cost, and has the potential for large-scale application. Attached Figure Description

[0021] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0022] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0023] Figure 1 A flowchart illustrating the preparation process of the bacterial cellulose / silver nanowire / MXene composite conductive film provided by this invention; Figure 2 This is a scanning electron microscope image of the bacterial cellulose / silver nanowire / MXene composite conductive film provided in Example 5 of the present invention at a scale of 50 μm. Figure 3 This is a scanning electron microscope image of the bacterial cellulose / silver nanowire / MXene composite conductive film provided in Example 5 of the present invention at the 10 μm scale. Figure 4 The thickness diagram of the bacterial cellulose / silver nanowire / MXene composite conductive film provided in Embodiment 5 of the present invention; Figure 5 The cyclic electroheating curve of the bacterial cellulose / silver nanowire / MXene composite conductive film provided in Example 5 of the present invention at 2.5V. Figure 6 The time-temperature curve of the bacterial cellulose / silver nanowire / MXene composite conductive film provided in Example 5 of the present invention at a voltage of 0.5-2.5V; Figure 7 The diagram shows the tensile strength and elongation of the bacterial cellulose / silver nanowire / MXene composite conductive films provided in Examples 1-5 of this invention. Figure 8 Comparison of resistance changes of AgNWs PVP and AgNWs composite conductive films provided in Examples 5 and 6 of the present invention after 100 adhesion cycles; Figure 9 The front and back photographs and resistance diagrams of the bacterial cellulose / silver nanowire / MXene composite conductive film provided in Example 5 of the present invention are shown. Figure 10 The electromagnetic shielding effectiveness diagrams are for the bacterial cellulose / silver nanowire / MXene composite conductive films provided in Examples 1-5 of this invention. Detailed Implementation

[0024] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] According to a first aspect of the present invention, a method for preparing a bacterial cellulose / silver nanowire / MXene composite conductive film is provided, comprising the following steps: S1. Preparation of bacterial cellulose dispersion: Add the bacterial cellulose blocks to deionized water in a certain proportion and disperse them by ultrasonication for 5-20 minutes to obtain a bacterial cellulose dispersion. Preparation of S2 and MXene dispersions: Hydrochloric acid and lithium fluoride were mixed at a volume-to-mass ratio of 10 mL: 1 g and used to etch Ti3ALC2. The reaction was carried out at 40 °C for 48 h. After the reaction was completed, the product was centrifuged and washed until neutral. Finally, the product was dispersed in water to obtain MXene dispersion. S3. Preparation of silver nanowire dispersion: Polyvinylpyrrolidone (PVP) with a molecular weight of 36 wDa and PVP with a molecular weight of 5.8 wDa were dissolved in ethylene glycol. The solutions were transferred to reaction flasks preheated to 130 °C and reacted using the polyol method for 5 h. Silver nitrate was then added and completely dissolved. Under vigorous stirring, 0.6 mmol / L ferric chloride / ethylene glycol solution was added to the above solution, and stirring was continued for 10 min. After stopping the reaction, the solution was allowed to stand for 3.5 h. The resulting precipitate was washed successively with acetone and ethanol, centrifuged at 1000–2000 rpm for 5 min, and then redispersed in 5 mg / mL PPVP solution to obtain a silver nanowire dispersion. S4. Preparation of composite thin films: a. Vacuum filter the bacterial cellulose dispersion obtained in step S1 to obtain a bacterial cellulose substrate; b. The MXene dispersion obtained in step S2 is redispersed with deionized water and deposited on a bacterial cellulose substrate by vacuum filtration to form an MXene conductive layer; c. The silver nanowire solution obtained in step S3 is redispersed with a 5 mg / mL polyvinylpyrrolidone solution, and deposited on the MXene conductive layer by vacuum filtration to form a silver nanowire conductive network layer, thereby obtaining a composite conductive film.

[0026] In step S1, the concentration of the bacterial cellulose dispersion is 0.1 mg / ml.

[0027] In step S2, the concentration of the MXene dispersion is 5 mg / ml.

[0028] In step S3, the mass-to-volume ratio of polyvinylpyrrolidone with a molecular weight of 36 wDa, polyvinylpyrrolidone with a molecular weight of 5.8 wDa, ethylene glycol, ferric chloride / ethylene glycol solution, and silver nitrate is 0.32 g: 0.32 g: 100 mL: 0.975 mL: 0.72 g.

[0029] In step S3, the concentration of the silver nanowire dispersion is 1 mg / mL.

[0030] In step S4,a, the concentration of the redispersed silver nanowire dispersion is 0.10-0.50 mg / mL; in step S4,b, the concentration of the redispersed MXene dispersion is 1.0-4.0 mg / mL.

[0031] In step S4, the pressure of the filtration device is -0.1 MPa.

[0032] According to a second aspect of the present invention, a bacterial cellulose / silver nanowire / MXene composite conductive film is provided.

[0033] The film comprises a bacterial cellulose substrate, an MXene conductive layer, and a silver nanowire conductive network layer.

[0034] The structure of the bacterial cellulose substrate, the MXene conductive layer, and the silver nanowire conductive network layer is as follows: the bacterial cellulose substrate is covered with the MXene conductive layer, and the MXene conductive layer is covered with the silver nanowire conductive network layer.

[0035] To better illustrate the innovative aspects of this invention, the following embodiments and comparative examples are provided.

[0036] Example 1 This embodiment includes the following steps, the specific implementation steps are as follows: Figure 1 As shown: S1. Preparation of bacterial cellulose dispersion: 2g of bacterial cellulose was added to 20mL of deionized water and subjected to ultrasonic cell disruption for 20min to obtain a bacterial cellulose (BC) dispersion with a solution concentration of 0.1mg / mL, which was used for the preparation of bacterial cellulose / silver nanowire / MXene composite conductive film. Preparation of S2 and MXene dispersion: Ti3AlC2 was etched using hydrochloric acid and lithium fluoride. The specific steps were as follows: 20 mL of hydrochloric acid and 2 g of lithium fluoride were added to a polytetrafluoroethylene beaker and stirred continuously at room temperature for 20 min; then the temperature was raised to 40℃, and Ti3AlC2 powder was added in small batches under gentle stirring to remove the aluminum layer; the etching reaction was carried out at 40℃ for 48 h; after the reaction, the product was repeatedly washed with deionized water and centrifuged multiple times until the pH of the supernatant was greater than 6; finally, the obtained product was dispersed in deionized water to prepare a 5 mg / mL MXene dispersion for subsequent use. S3. Preparation of silver nanowire dispersion: First, 0.32 g of polyvinylpyrrolidone (PVP) with a molecular weight of 36 wDa and 0.32 g of PVP with a molecular weight of 5.8 wDa were dissolved in 100 mL of ethylene glycol. Then, the solution was transferred to a reaction flask preheated to 130 °C and reacted at this temperature for 5 h. Next, 0.72 g of silver nitrate was added to the solution and completely dissolved. Under vigorous stirring, 0.975 mL of FeCl3 / ethylene glycol solution with a concentration of 0.6 mmol / L was added to the above solution, and stirring was continued for 10 min. Finally, the reaction was stopped, and the mixture was allowed to stand for 3.5 h. The resulting precipitate was washed successively with acetone and ethanol, centrifuged at 1500 rpm for 5 min, and then redispersed in a pre-prepared 5 mg / mL PVP solution to obtain a 1 mg / mL silver nanowire dispersion for subsequent use. S4. Construction of bacterial cellulose substrate: 20 mL of the BC dispersion was filtered under vacuum at -0.1 MPa to form a BC substrate film. S5, Formation of the MXene conductive layer: The MXene dispersion in step S2 was redispersed with deionized water to a concentration of 1 mg / mL. After the bacterial cellulose substrate was formed, 4 mL of the redispersed MXene dispersion was vacuum filtered at -0.1 MPa and attached to the bacterial cellulose substrate to form an MXene conductive layer. S6. Preparation of PVP-coated silver nanowire conductive layer: The silver nanowire dispersion from step S3 was redispersed with a 5 mg / mL PVP solution to a concentration of 0.1 mg / mL. 1 mL of the redispersed silver nanowire dispersion was then deposited onto the surface of the MXene layer under vacuum at -0.1 MPa to obtain BMA1.

[0037] Example 2 This embodiment is based on Example 1, except that the amount of silver nanowire dispersion added in step S6 is 3 mL, and the other specific processing parameters are the same as in Example 1, to obtain BMA2.

[0038] Example 3 This embodiment is based on Example 1, except that the amount of silver nanowire dispersion added in step S6 is 5 mL, and the other specific processing parameters are the same as in Example 1, to obtain BMA3.

[0039] Example 4 This embodiment is based on Example 1, except that the amount of silver nanowire dispersion added in step S6 is 7 mL, and the other specific processing parameters are the same as in Example 1, to obtain BMA4.

[0040] Example 5 This embodiment is based on Example 1, except that the amount of silver nanowire dispersion added in step S6 is 9 mL, and the other specific processing parameters are the same as in Example 1, to obtain BMA5.

[0041] Example 6 S1. Preparation of bacterial cellulose dispersion: 2g of bacterial cellulose was added to 20mL of deionized water and subjected to ultrasonic cell disruption for 20min to obtain a bacterial cellulose (BC) dispersion with a solution concentration of 0.1mg / mL, which was used for the preparation of bacterial cellulose / silver nanowire / MXene composite conductive film. Preparation of S2 and MXene dispersion: Ti3AlC2 was etched using hydrochloric acid and lithium fluoride. The specific steps were as follows: 20 mL of hydrochloric acid and 2 g of lithium fluoride were added to a polytetrafluoroethylene beaker and stirred continuously at room temperature for 20 min; then the temperature was raised to 40℃, and Ti3AlC2 powder was added in small batches under gentle stirring to remove the aluminum layer; the etching reaction was carried out at 40℃ for 48 h; after the reaction, the product was repeatedly washed with deionized water and centrifuged multiple times until the pH of the supernatant was greater than 6; finally, the obtained product was dispersed in deionized water to prepare a 5 mg / mL MXene dispersion for subsequent use. S3. Preparation of silver nanowire dispersion: First, 0.32 g of polyvinylpyrrolidone (PVP) with a molecular weight of 36 wDa and 0.32 g of PVP with a molecular weight of 5.8 wDa were dissolved in 100 mL of ethylene glycol. Then, the solution was transferred to a reaction flask preheated to 130 °C and reacted at this temperature for 5 h. Next, 0.72 g of silver nitrate was added to the solution and completely dissolved. Under vigorous stirring, 0.975 mL of FeCl3 / ethylene glycol solution with a concentration of 0.6 mmol / L was added to the above solution, and stirring was continued for 10 min. Finally, the reaction was stopped, and the mixture was allowed to stand for 3.5 h. The resulting precipitate was washed successively with acetone and ethanol, centrifuged at 1500 rpm for 5 min, and then redispersed in deionized water to obtain a 1 mg / mL silver nanowire aqueous dispersion for subsequent use. S4. Construction of bacterial cellulose substrate: 20 mL of BC dispersion was filtered under vacuum at -0.1 MPa to form a BC substrate film; S5, Formation of the MXene conductive layer: The MXene dispersion in step S2 was redispersed with deionized water to a concentration of 1 mg / mL. After the bacterial cellulose substrate was formed, 4 mL of the redispersed MXene dispersion was vacuum filtered at -0.1 MPa and attached to the bacterial cellulose substrate to form an MXene conductive layer. S6. Preparation of PVP-coated silver nanowire conductive layer: The silver nanowire aqueous dispersion from step S3 was redispersed in deionized water to a concentration of 0.1 mg / mL. 9 mL of the redispersed silver nanowire aqueous dispersion was then vacuum filtered at -0.1 MPa and deposited onto the surface of the MXene layer to obtain BMA6.

[0042] Test Example 1 The surface morphology of the composite film was observed using a cold field emission scanning electron microscope (SEM, Hitachi Regulus 8100) at an accelerating voltage of 10 kV. The results are as follows: Figure 2 and Figure 3 As shown. Figure 2 The typical morphology of the BMA5 thin film (BC / MXene / AgNWs) is shown. It can be observed that the high aspect ratio silver nanowires (AgNWs) are uniformly attached to the MXene surface, forming a three-dimensional conductive network framework. MXene effectively fills the gaps between the nanowires, creating a denser conductive network. This structure helps provide more conductive pathways and reduces the contact resistance between the nanowires.

[0043] Figure 3The specific morphology of the BMA5 film is shown. At a high magnification of 10 μm, it can be clearly seen that the PVP-coated conductive layer of silver nanowires makes the silver nanowires more stable on the MXene surface. Figure 4 The BMA5 is shown to be only 12 μm thick.

[0044] Test Example 2 To systematically investigate the electrothermal reliability and lifespan of the thin film under continuous energization, experiments were conducted on the long-term stability of a bacterial cellulose / silver nanowire / MXene composite conductive film. The specific test procedure was as follows: The film sample was attached to a thermally insulating substrate, and a thermocouple was fixed to the center of the sample surface using high-temperature resistant tape to monitor temperature changes in real time. A constant 2.5V DC voltage was then applied to the sample to simulate a real-world high-load continuous operating environment. During the test, the data acquisition system automatically and continuously recorded time (s), real-time temperature (°C), and operating voltage (V) at 5-second intervals to ensure complete capture of the film's dynamic temperature changes.

[0045] The long-term operational stability results of the thin film are as follows: Figure 5 As shown in the figure, the BMA5 (BC / MXene / AgNWs) film exhibits excellent durability. Under a constant voltage of 2.5V, the film can maintain a stable operating temperature of 126℃ for 3000s (approximately 1 hour), and the surface steady-state temperature fluctuation remains within 3℃ throughout the test, demonstrating highly stable thermal output characteristics. Furthermore, in 10 cycles of 0-2.5V switching voltage testing, the film's limiting temperature remained stable at 126℃ without significant degradation. This significant performance advantage stems from its unique three-dimensional conductive network structure: the PVP-coated silver nanowires enhance the film's mechanical strength while strengthening its oxidation resistance; the intermediate MXene conductive layer not only reinforces the overall network's mechanical stability but also promotes uniform current and heat distribution, effectively suppressing localized overheating. The synergistic effect of these two elements ensures the film's functional reliability and structural integrity under long-term, high-power conditions, providing crucial support for its practical application in flexible electronic devices.

[0046] Test Example 3 To verify the electrothermal properties of the bacterial cellulose / silver nanowire / MXene composite conductive film, this test example uses a BMA5 film as the experimental subject. The film was stimulated with different DC voltages ranging from 0.5 to 2.5 V, and the surface temperature change over time was monitored in real time. The results are as follows: Figure 6 As shown.

[0047] As can be seen, the film exhibits rapid and significant electrothermal response characteristics: the temperature increases non-linearly with increasing voltage, rapidly rising from room temperature (approximately 35°C) to 126°C within 60 seconds; after the voltage is removed, the film can recover to ambient temperature within 50 seconds, demonstrating excellent thermal response speed and thermal recovery capability. This result indicates that the bacterial cellulose / silver nanowire / MXene composite conductive film prepared in this invention possesses excellent comprehensive electrothermal performance: its rapid heating process benefits from the highly efficient three-dimensional conductive network synergistically constructed by high aspect ratio silver nanowires and MXene, which has low resistance characteristics, ensuring efficient current transmission and rapid Joule heat conversion; simultaneously, the film's rapid cooling rate stems from its low heat capacity and efficient heat exchange with the surrounding environment, a characteristic that is of great significance for applications such as wearable physiotherapy devices requiring rapid thermal cycling.

[0048] Test Example 4 To systematically evaluate the comprehensive mechanical properties of the prepared composite films, the tensile strength and elongation of the BMA1-BMA5 films were tested, and the results are summarized in [the table below]. Figure 7 .Depend on Figure 7 It can be seen that as the silver nanowire content increases, the mechanical strength of the film also increases. When the silver nanowire content reaches 0.9 mg, the fracture strength of the BMA5 film can reach 77.3 MPa and the elongation can reach 4.1%.

[0049] Test Example 5 To systematically evaluate the durability of the prepared composite film, this invention tested the resistance of the BMA5 film after 100 adhesion cycles and its front and back side resistances. Figure 8 It can be seen that the resistance of the BMA5 film containing the AgNWs-PVP layer hardly changed after 100 adhesion tests, while the resistance of the BMA6 film prepared from silver nanowires (AgNWs) without PVP blending in Example 6 increased from 0.429 Ω / sq to 3.73 Ω / sq after only 20 adhesion tests. This indicates that the BMA5 film has extremely strong durability, and the PVP effectively protects the performance stability of the silver nanowires, making them less prone to damage in daily use. This demonstrates its reliability in maintaining stable performance even under extreme conditions. Figure 9 It can be seen that the film has obvious Janus structure characteristics, with obvious color difference between the front and back sides, and the resistance of the conductive layer on the front side is only 0.429Ω / sq, while the back side is an insulator.

[0050] Test Example 6 To evaluate the application potential of the BMA composite film (BC / MXene / AgNWs) prepared in this invention in the field of electromagnetic interference protection, this invention systematically tested the electromagnetic shielding effectiveness (EMI SE) of BMA1-BMA5 films in the X-band (8.2-12.4GHz).

[0051] Test results are as follows Figure 10 As shown, the electromagnetic shielding effectiveness spectrum of BMA films with different silver nanowire (AgNWs) contents is clearly displayed. Quantitative analysis shows that at the center frequency of 8.2 GHz, with the increase of AgNWs content in the film (0.1-0.9 mg), its total electromagnetic shielding effectiveness (…) SE T The shielding performance of BMA1 shows a significant upward trend, with specific values ​​of 35.7 dB, 38.4 dB, 48.1 dB, 49.6 dB, and 52.3 dB, respectively. This characteristic is mainly due to its three-dimensional conductive network structure: AgNWs form a highly efficient conductive network responsible for reflecting and absorbing electromagnetic waves; MXene further enhances the network's connectivity and dielectric loss capability, while filling the gaps between the silver nanowire networks; and the PVP coating on the silver nanowires provides stable protection, enhancing the stability of the conductive network. The synergy of these three elements enables BMA to achieve shielding performance far exceeding the commercial application threshold (20 dB), demonstrating broad application prospects in the field of flexible transparent electronics.

[0052] In summary, the BMA composite conductive film prepared by this invention exhibits excellent mechanical strength, low thickness, conductivity, and environmental stability due to the tight bonding between its functional layers, providing a reliable guarantee for subsequent applications. The preparation process parameters are well-defined, have good repeatability, and are suitable for large-scale production.

[0053] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a bacterial cellulose / silver nanowire / MXene composite conductive film, characterized in that, Includes the following steps: S1. Preparation of bacterial cellulose dispersion: Add the bacterial cellulose blocks to deionized water in a certain proportion and ultrasonically disperse for 5-20 minutes to obtain a bacterial cellulose dispersion. Preparation of S2 and MXene dispersions: Hydrochloric acid and lithium fluoride were mixed at a volume-to-mass ratio of 10 mL: 1 g and used to etch Ti3ALC2. The reaction was carried out at 40 °C for 48 h. After the reaction was completed, the product was centrifuged and washed until neutral. Finally, the product was dispersed in water to obtain MXene dispersion. S3. Preparation of silver nanowire dispersion: Polyvinylpyrrolidone (PVP) with a molecular weight of 36 wDa and PVP with a molecular weight of 5.8 wDa were dissolved in ethylene glycol. The solutions were transferred to reaction flasks preheated to 130 °C and reacted using the polyol method for 5 h. Silver nitrate was then added and completely dissolved. Under vigorous stirring, 0.6 mmol / L ferric chloride / ethylene glycol solution was added to the above solution, and stirring was continued for 10 min. After stopping the reaction, the solution was allowed to stand for 3.5 h. The resulting precipitate was washed successively with acetone and ethanol, centrifuged at 1000–2000 rpm for 5 min, and then redispersed in 5 mg / mL PPVP solution to obtain a silver nanowire dispersion. S4. Preparation of composite thin films: a. Vacuum filter the bacterial cellulose dispersion obtained in step S1 to obtain a bacterial cellulose substrate; b. The MXene dispersion obtained in step S2 is redispersed with deionized water and deposited on a bacterial cellulose substrate by vacuum filtration to form an MXene conductive layer; c. The silver nanowire solution obtained in step S3 is redispersed with a 5 mg / mL polyvinylpyrrolidone solution, and deposited on the MXene conductive layer by vacuum filtration to form a silver nanowire conductive network layer, thereby obtaining a composite conductive film.

2. The method for preparing the bacterial cellulose / silver nanowire / MXene composite conductive film as described in claim 1, characterized in that, In step S1, the concentration of the bacterial cellulose dispersion is 0.1 mg / ml.

3. The method for preparing the bacterial cellulose / silver nanowire / MXene composite conductive film as described in claim 1, characterized in that, In step S2, the concentration of the MXene dispersion is 5 mg / ml.

4. The method for preparing the bacterial cellulose / silver nanowire / MXene composite conductive film as described in claim 1, characterized in that, In step S3, the mass-to-volume ratio of polyvinylpyrrolidone with a molecular weight of 36 wDa, polyvinylpyrrolidone with a molecular weight of 5.8 wDa, ethylene glycol, ferric chloride / ethylene glycol solution, and silver nitrate is 0.32 g: 0.32 g: 100 mL: 0.975 mL: 0.72 g.

5. The method for preparing the bacterial cellulose / silver nanowire / MXene composite conductive film as described in claim 1, characterized in that, In step S3, the concentration of the silver nanowire dispersion is 1 mg / mL.

6. The method for preparing the bacterial cellulose / silver nanowire / MXene composite conductive film as described in claim 1, characterized in that, In step S4,a, the concentration of the redispersed silver nanowire dispersion is 0.10-0.50 mg / mL; in step S4,b, the concentration of the redispersed MXene dispersion is 1.0-4.0 mg / mL.

7. The method for preparing the bacterial cellulose / silver nanowire / MXene composite conductive film as described in claim 1, characterized in that, In step S4, the pressure of the filtration device is -0.1 MPa.

8. The bacterial cellulose / silver nanowire / MXene composite conductive film prepared by the method according to any one of claims 1-7.

9. The bacterial cellulose / silver nanowire / MXene composite conductive film as described in claim 8, characterized in that, The film comprises a bacterial cellulose substrate, an MXene conductive layer, and a silver nanowire conductive network layer.

10. The bacterial cellulose / silver nanowire / MXene composite conductive film as described in claim 9, characterized in that, The bacterial cellulose substrate, the MXene conductive layer, and the silver nanowire conductive network layer are structured as follows: the bacterial cellulose substrate is covered with the MXene conductive layer, and the MXene conductive layer is covered with the silver nanowire conductive network layer.

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