A copper-sheathed cellulose conductive fiber, and a preparation method and application thereof

Abstract

This invention relates to a copper-sheathed cellulose conductive fiber, its preparation method, and its application. The preparation method includes: swelling cellulose fibers and then immersing them in a copper ion coordination solution to obtain precursor fibers; pretreating the precursor fibers at 150–180°C for 10–30 min under an inert atmosphere to obtain pretreated fibers; placing the pretreated fibers in a tube furnace, introducing a hydrogen-argon mixed atmosphere, heating to 200–300°C, and maintaining the temperature for a reduction reaction for 1–3 h; after the reaction, cooling the furnace to room temperature and removing the fibers to obtain the copper-sheathed cellulose conductive fiber. The inert atmosphere low-temperature preheating of this invention can effectively control the material interface state and optimize the reduction behavior, significantly improving the material's conductive structure and overall quality. It can pre-remove adsorbed moisture, residual impurities, and various oxygen-containing functional groups from the matrix surface, effectively weakening interfacial forces and significantly reducing the activation energy of hydrogen participating in the reduction reaction, thereby achieving a lower temperature and more efficient completion of the reduction process, effectively improving the overall conductivity of the material.

Description

Technical Field

[0001] This invention belongs to the field of functional fiber technology, specifically relating to a copper sheath cellulose conductive fiber, its preparation method, and its application. Background Technology

[0002] With the rapid development of flexible electronics, smart wearables, and the Internet of Things (IoT) technologies, flexible strain and pressure sensors are showing broad application prospects in complex scenarios such as human health monitoring, motion behavior recognition, underwater safety equipment, and intelligent sports facilities. Conductive fibers, due to their flexibility, lightweight, weavability, and high-sensitivity conductivity, have become the core material for next-generation flexible sensors.

[0003] However, existing conductive fibers face significant bottlenecks in both material properties and fabrication processes, hindering their practical application. In terms of performance, traditional conductive fibers generally suffer from weak bonding between the conductive layer and the fiber substrate, as well as poor interfacial stability. This leads to the conductive layer easily detaching and cracking under repeated deformation or complex service environments, resulting in insufficient sensing stability and durability. More critically, existing fibers exhibit poor tolerance to environmental interference factors such as temperature, humidity, and water pressure. The superposition and crosstalk of multi-source excitation signals prevent effective decoupling and accurate identification. In scenarios such as simultaneous monitoring of multiple human movements, underwater dynamic sensing, and multi-ball impact recognition, signal misinterpretation is particularly prominent, severely limiting the reliability of the sensing system. In terms of fabrication processes, the construction of existing high-conductivity fibers largely relies on technologies such as high-temperature carbonization, chemical plating, or vapor deposition. These technologies generally suffer from drawbacks such as expensive equipment, cumbersome processes, and heavy environmental burdens. Furthermore, it is difficult to ensure excellent conductivity while simultaneously maintaining the fiber's mechanical strength and flexibility.

[0004] Therefore, developing a highly conductive fiber that is simple to process, environmentally friendly, has a strong conductive layer, excellent mechanical properties, and multi-signal decoupling capability has become a key need that urgently needs to be addressed in this field. Summary of the Invention

[0005] Based on the aforementioned shortcomings and deficiencies in the prior art, one of the objectives of this invention is to at least solve one or more of the aforementioned problems in the prior art. In other words, one of the objectives of this invention is to provide a copper sheath cellulose conductive fiber that meets one or more of the aforementioned requirements, as well as its preparation method and application.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: A method for preparing copper-sheathed cellulose conductive fibers includes the following steps: (1) The cellulose fibers were swollen and then immersed in a copper ion coordination solution to obtain precursor fibers; (2) Pre-treat the precursor fibers at 150-180℃ for 10-30 min under an inert atmosphere to obtain pre-treated fibers; (3) Place the pretreated fiber in a tube furnace, introduce a hydrogen-argon mixed atmosphere, heat to 200-300℃, and keep it at the temperature for 1-3 hours for reduction reaction. After the reaction is completed, cool the furnace to room temperature and take it out to obtain copper sheath cellulose fiber.

[0007] As a preferred embodiment, in step (1), swelling is carried out in a 5-15 wt% NaOH solution for a duration of 30-90 min.

[0008] As a preferred embodiment, in step (1), the copper ion coordination solution is a copper ion-alkali mixed solution, and the immersion time is at least 3 hours.

[0009] As a preferred embodiment, the copper ion-alkali mixed solution is an aqueous solution of NaOH with a mass fraction of 5-15% and copper sulfate pentahydrate of 0.1-0.25M.

[0010] As a preferred option, in step (2), the inert atmosphere is nitrogen or argon.

[0011] As a preferred embodiment, in step (3), the volume ratio of hydrogen to argon in the hydrogen-argon mixed atmosphere is 2:8.

[0012] As a preferred embodiment, in step (3), the heating rate is 3-5 °C / min. -1 .

[0013] As a preferred embodiment, in step (1), the cellulose fibers are washed with a mixture of ethanol and water before the swelling treatment.

[0014] The present invention also provides copper-sheathed cellulose conductive fibers prepared by the preparation method described in any of the preceding embodiments, wherein the copper-sheathed cellulose conductive fibers have a cellulose fiber core and a copper sheath.

[0015] The present invention also provides the application of the copper sheath cellulose conductive fiber described above for flexible sensing.

[0016] Compared with the prior art, the beneficial effects of this invention are: (1) The process of this invention is green and simple, achieving dual reduction and interface locking in one step; unlike the complex multi-step processes such as chemical plating, vapor deposition or high-temperature carbonization, this invention utilizes the in-situ generation of reducing atmosphere and carbonaceous reducing agent by pyrolysis of cellulose to simultaneously complete the vapor phase reduction of copper ions, the in-situ carbon replacement reduction of copper oxide and the microphase regulation of the copper-cellulose interface in a single heat treatment process; no expensive plating solution, complex pretreatment or toxic chemical reagents are required, the process route is short, the cost is low, the environment is friendly, and it is easy to scale up industrially; (2) The inert atmosphere low-temperature preheating of the present invention can effectively regulate the material interface state and optimize the reduction behavior, significantly improving the material's conductive structure and overall quality; this pretreatment method can remove adsorbed moisture, residual impurities and various oxygen-containing functional groups from the substrate surface in advance, effectively weaken the interfacial forces, and significantly reduce the activation energy of hydrogen participating in the reduction reaction, thereby achieving efficient completion of the reduction process at a lower temperature; at the same time, it helps to build a continuous and regular conductive network, further improving the overall conductivity of the material and giving the material better and more stable physicochemical properties; (3) The present invention constructs a dual interface locking mechanism, which significantly enhances the anti-peeling and anti-oxidation capabilities of the conductive layer; the reducing gas hydrogen atmosphere reduces the copper ions anchored on the fiber surface to metallic copper, forming a copper sheath that is firmly bonded to the cellulose substrate; at the same time, the carbon components generated by cellulose pyrolysis undergo in-situ replacement at the copper-cellulose interface, which strengthens the interface anchoring on the one hand, and on the other hand, acts as a secondary reducing agent to reduce the copper oxide (CuO / Cu2O) that is inevitably generated at high temperature back to the conductive copper phase; this dual locking mechanism fundamentally inhibits the interface peeling and oxidation failure of the copper sheath during repeated bending, friction and underwater service, and the conductivity stability is significantly better than that of traditional physical coating or chemical plating conductive layers; (4) The copper sheath of the present invention has high purity, good density, and excellent and stable conductivity. Thanks to the synergistic effect of hydrogen primary reduction and pyrolytic carbon secondary reduction, the copper sheath is dynamically maintained in the zero-valence state of the metal, avoiding the oxidation deactivation problem caused by trace oxygen or temperature fluctuations under a single reducing atmosphere. The resulting copper sheath fiber has low resistivity and high conductivity retention rate, and maintains a stable conductivity response under the coupling effect of complex environment (temperature change, high humidity, underwater pressure).

[0017] (5) The core-shell structure of the present invention endows the intrinsic multimodal sensing signal decoupling capability. Based on the heterogeneous structure of "flexible cellulose core-rigid copper sheath", the fiber produces a resistance response with physical intrinsic differences in response to different external stimuli: under strain, it is mainly manifested as the opening and closing of microcracks in the copper sheath; under pressure, it is mainly manifested as the change of sheath contact area and tunneling effect; when the copper sheath cellulose fiber is subjected to tensile deformation, the resistance response of the conductive sheath is sensitive to the integrity of the conductive path, and the capacitance response of the dielectric core-shell structure is sensitive to the geometric deformation of the interface. Based on this structure-response domain separation mechanism, the decoupling identification of sensing modes is realized by synchronously acquiring resistance signals and capacitance signals, which fundamentally solves the problem of crosstalk and misjudgment of traditional conductive fiber signals. Attached Figure Description

[0018] Figure 1 The images show the SEM morphology comparison of the copper-sheathed cellulose conductive fiber before and after preparation in Example 1 of the present invention. (a) is the surface of the lyocell fiber without copper sheath, and (b) is the surface of the copper-sheathed cellulose fiber after in-situ growth of copper sheath. Figure 2These are mechanical property test diagrams of the copper-sheathed cellulose conductive fiber and lyocell fiber from Examples 1-4 of the present invention. Figure 3 This is a bar chart comparing the conductivity of copper-sheathed cellulose conductive fibers in Examples 1-4 of the present invention. Figure 4 This is a diagram showing the response of the copper-sheathed cellulose conductive fiber of Embodiment 1 of the present invention to the sensing signals of the basic human body movement. Figure 5 This is a pressure signal response diagram of the copper-sheathed cellulose conductive fiber in an underwater distress call scenario according to Embodiment 1 of the present invention; Figure 6 This is a diagram illustrating the decoupling, identification, and classification of ball-related sensor signals in a gymnasium using the copper-sheathed cellulose conductive fiber sensor of Embodiment 1 of the present invention. Figure 7 This is an SEM image of the copper-sheathed cellulose conductive fiber of Comparative Example 4 of the present invention. Figure 8 This is a comparison of the conductivity of copper-sheathed cellulose conductive fibers in Examples 1-4 and Comparative Examples 1, 3, and 5 after 1000 bending cycles. Figure 9 This is an SEM image of the copper-sheathed cellulose conductive fiber of Comparative Example 5 of the present invention. Detailed Implementation

[0019] The copper sheath cellulose conductive fiber of the present invention, its preparation method and application are described in detail below.

[0020] The copper-sheathed cellulose conductive fiber of this invention uses cellulose fiber as the core and metallic copper as the sheath, employing a gas-phase reduction-carbon replacement synergistic interface microphase control strategy to construct a dense copper sheath conductive layer in situ on the cellulose surface. Specifically, during heat treatment, a hydrogen atmosphere reduces the copper precursor in situ to metallic copper, forming a highly conductive copper sheath. Simultaneously, the copper sheath surface is easily oxidized to form copper oxide under high temperature conditions, while the carbon components generated by the pyrolysis and carbonization of cellulose act as an in-situ reducing agent, reducing the copper oxide back to the conductive copper phase, thus achieving dynamic maintenance and structural replacement of the copper sheath's conductivity. The synergy of hydrogen reduction and carbon replacement not only ensures the density and high conductivity of the copper sheath but also constructs a dual locking mechanism at the copper-cellulose interface, fundamentally inhibiting the oxidation failure and interface peeling of the conductive layer.

[0021] The copper-sheathed cellulose conductive fiber of this invention possesses both excellent conductivity and mechanical flexibility, maintaining a stable conductive response even under the coupled effects of complex environmental factors such as temperature, humidity, and water pressure. Simultaneously, based on the intrinsic characteristics of its core-shell structure, the fiber exhibits multimodal signal decoupling capabilities, enabling effective differentiation and accurate identification of strain, pressure, and environmental interference signals. Overall, this copper-sheathed cellulose conductive fiber can be widely applied in complex scenarios such as simultaneous monitoring of multiple human signals, underwater dynamic sensing, and impact recognition of intelligent sports facilities, providing a highly reliable and multifunctional conductive fiber material for the field of flexible sensing and significantly expanding the application boundaries of conductive fibers.

[0022] Specifically, the method for preparing copper-sheathed cellulose conductive fibers according to embodiments of the present invention includes the following steps: (1) The cellulose fibers were swollen and then immersed in a copper ion coordination solution to obtain precursor fibers; The cellulose fibers mentioned above are preferably lyocell fiber bundles; Prior to the swelling treatment, the cellulose fibers are washed with a mixture of ethanol and water to remove impurities from the fiber surface; the preferred volume ratio of ethanol to water is 1:1. The swelling was carried out in a 5-15 wt% NaOH solution for 30-90 min. The specific concentration and duration could be determined according to the actual application requirements. The copper ion coordination solution mentioned above is a copper ion-alkali mixed solution, and the immersion time is at least 3 hours; wherein, the copper ion-alkali mixed solution is preferably an aqueous solution of NaOH with a mass fraction of 5-15% and 0.1-0.25M copper sulfate pentahydrate; the specific concentration can be determined according to the actual application requirements.

[0023] (2) Pre-treat the precursor fibers at 150-180℃ for 10-30 min under an inert atmosphere to obtain pre-treated fibers; The inert atmosphere mentioned above is either nitrogen or argon, which can be determined according to the actual application requirements; The above pretreatment thoroughly removes adsorbed moisture, residual solvents, and unstable oxygen-containing impurities from the inside and surface of the material; and ensures that a reducing gas is introduced into the system to continue heating and carrying out the hydrogen reduction reaction.

[0024] (3) Place the pretreated fiber in a tube furnace, introduce a hydrogen-argon mixed atmosphere, heat to 200-300℃, and keep it at the temperature for 1-3 hours for reduction reaction. After the reaction is completed, cool the furnace to room temperature and take it out to obtain copper sheath cellulose fiber. In the hydrogen-argon mixed atmosphere, the volume ratio of hydrogen to argon is 2:8. The preferred heating rate is 3–5 °C / min. -1 The specific heating rate can be determined according to the actual application requirements.

[0025] The copper-sheathed cellulose conductive fiber prepared by this invention includes a cellulose fiber core and a dense copper sheath conductive layer covering the surface of the core. The copper sheath conductive layer is constructed in situ through a gas-phase reduction-carbon replacement synergistic interface microphase control strategy. Based on the synergistic effect of hydrogen main reduction and pyrolysis carbon in situ secondary reduction, a dual locking mechanism is formed at the copper-cellulose interface, which endows the fiber with high conductivity, interface stability and multimodal sensing signal decoupling capability.

[0026] The copper sheath cellulose conductive fiber of the present invention, its preparation method and application are further explained and illustrated below through specific embodiments and comparative examples.

[0027] Example 1: The method for preparing copper-sheathed cellulose conductive fibers in this embodiment includes the following steps: (1) CF@Cu 2+ Preparation of precursor fibers; Lyocell fiber bundles with an average diameter of 0.5 mm were selected and washed three times with a mixture of ethanol and deionized water at a volume ratio of 1:1 to remove surface impurities. Then, the fibers were placed in a 10% NaOH aqueous solution and pretreated for swelling at room temperature for 30 min. Preparation of copper ion coordination solution: Using 50 mL of water as a reference, add 10% NaOH and 0.2 mol / L copper sulfate pentahydrate, stir continuously for 15 min, remove a small amount of Cu(OH)2 precipitate by ordinary filtration, and obtain a clear copper ion coordination solution; The pretreated fibers were immersed in the above copper ion coordination solution and reacted at room temperature for 6 hours to allow Cu to... 2+ CF@Cu is firmly anchored to the fiber surface through coordination. 2+ Precursor fibers; (2) Preheating treatment; CF@Cu 2+ Precursor fibers were preheated at 150°C for 30 minutes in an inert N2 atmosphere to obtain preheated fibers. (3) Preparation of copper sheath cellulose conductive fibers The preheated fibers were placed in the constant temperature zone of a tube furnace, and a hydrogen-argon mixed atmosphere (hydrogen to argon volume ratio of 2:8) was introduced, with a temperature of 5℃·min. -1 The temperature was increased to 250℃ at a heating rate, and the reduction reaction was maintained at this temperature for 2 hours. After the reaction was completed, heating was stopped, and the furnace was cooled to room temperature. The furnace was then removed and dried in air for 2 hours to obtain copper-sheathed cellulose conductive fibers, denoted as CF@Cu. 0.2 .

[0028] Example 2: The method for preparing copper sheath cellulose conductive fibers in this embodiment differs from that in Example 1 in that: In step (1), the copper ion concentration of the copper ion coordination solution is 0.1M, the mass fraction of the NaOH solution is 5%, and the swelling pretreatment time is 90min; In step (3), the heating rate is 3℃·min. -1 The reduction temperature is 200℃; The other steps and process parameters are the same as in Example 1; The resulting copper-sheathed cellulose conductive fiber is denoted as CF@Cu 0.1 .

[0029] Example 3: The method for preparing copper sheath cellulose conductive fibers in this embodiment differs from that in Example 1 in that: In step (1), the copper ion concentration of the copper ion coordination solution is 0.15M, the mass fraction of the NaOH solution is 15%, and the swelling pretreatment time is 30min; In step (3), the reduction temperature is 300℃; The other steps and process parameters are the same as in Example 1; The resulting copper-sheathed cellulose conductive fiber is denoted as CF@Cu 0.15 .

[0030] Example 4: The method for preparing copper sheath cellulose conductive fibers in this embodiment differs from that in Example 1 in that: In step (1), the copper ion concentration of the copper ion coordination solution is 0.25M, and the swelling pretreatment time is 60min; The other steps and process parameters are the same as in Example 1; The resulting copper-sheathed cellulose conductive fiber is denoted as CF@Cu 0.25 .

[0031] The copper-sheathed cellulose conductive fibers prepared in Examples 1-4 all exhibit excellent electrical conductivity, mechanical properties, and interfacial stability. The copper sheath conductive layer is firmly bonded and maintains a stable conductive response even after repeated bending and cleaning, meeting the needs of complex and multi-scenario applications. Specific applications are as follows: (1) Synchronous detection of multiple human movements; By weaving or attaching copper-sheathed cellulose conductive fibers to the skin, joints, and muscles of the human body, different movements such as walking, bending over, raising arms, and running cause different strain patterns in the fibers, resulting in changes in the copper sheath conductive network and outputting resistance signals with different waveforms, amplitudes, response rates, and relaxation times. This is suitable for human health monitoring and exercise behavior analysis.

[0032] (2) Underwater dynamic monitoring and emergency call; By integrating copper-sheathed cellulose conductive fibers into underwater wearable equipment such as diving suits or life jackets, a multimodal response mechanism based on copper sheathed fibers can be achieved. Normal limb movements generate periodic, low-amplitude resistance fluctuations; changes in water depth and current velocity cause slow, stable signal drift; while violent chest compressions or limb struggles during an emergency call manifest as abrupt, high-amplitude, and irregular resistance responses. These three types of signals exhibit significant differences in time-frequency domain characteristics. Real-time decoupling can be achieved through this mechanism, enabling accurate identification of emergency situations and triggering alarms. This avoids false alarms caused by water pressure and normal movement interference, thus improving the safety of underwater operations.

[0033] (3) Ball impact recognition and intelligent classification; By arraying copper-sheathed cellulose conductive fibers and laying them on the floor of a gymnasium or in the ball storage area, the impact signals from different balls such as basketballs, soccer balls, volleyballs, and table tennis balls—which differ significantly in mass, volume, elastic modulus, and surface structure—are generated when they fall or impact the fiber array. These balls produce pressure-impact composite signals with completely different peak sizes, pulse widths, energy decay rates, and spatial distributions. Through spatial positioning and waveform analysis, the fibers independently distinguish and classify the impact signals from different balls, enabling automatic ball sorting and trajectory tracking. This method is suitable for intelligent sports facilities and event equipment management.

[0034] Comparative Example 1: The preparation method of the copper sheath cellulose conductive fiber in this comparative example differs from that in Example 1 in that: The NaOH solution swelling pretreatment step is omitted, and the cleaned Lyocell fiber bundles are directly immersed in the copper ion coordination solution to carry out the coordination reaction. The other steps and process parameters are the same as in Example 1; Because there are insufficient active sites on the fiber surface due to the lack of interfacial pre-expansion activation, Cu 2+ The load capacity is low and the interfacial bonding is weak. After reduction, the conductive layer of the copper sheath lacks effective anchoring with the fiber substrate, making it prone to interfacial peeling, resulting in poor conductivity stability and significantly lower conductivity than in Example 1.

[0035] Comparative Example 2: The preparation method of the copper sheath cellulose conductive fiber in this comparative example differs from that in Example 1 in that: The reduction temperature in the tube furnace was reduced to 150℃; The other steps and process parameters are the same as in Example 1; Due to the excessively low reduction temperature, Cu 2+ Insufficient thermodynamic reduction driving force means that a large number of copper ions are not reduced to metallic copper, and a continuous and dense copper sheath conductive network cannot be formed on the fiber surface. As a result, the fiber is basically non-conductive and cannot meet the requirements of practical applications.

[0036] Comparative Example 3: The preparation method of the copper sheath cellulose conductive fiber in this comparative example differs from that in Example 1 in that: The copper ion coordination solution was not filtered to remove impurities, and the turbid liquid containing Cu(OH)2 precipitate was used directly for the coordination reaction; The other steps and process parameters are the same as in Example 1; Cu(OH)2 precipitation leads to Cu 2+ Uneven loading on the fiber surface resulted in microscopic defects and local fractures in the copper sheath conductive layer after reduction, leading to poor continuity of the conductive network and insufficient interface stability. Consequently, the conductivity and mechanical properties of the fiber were inferior to those in Example 1.

[0037] Comparative Example 4: The preparation method of the copper sheath cellulose conductive fiber in this comparative example differs from that in Example 1 in that: The reduction reaction was carried out directly by introducing hydrogen gas without preheating at 150°C under a nitrogen inert atmosphere. The other steps and process parameters are the same as in Example 1; Because adsorbed water, impurities, and oxygen-containing groups remain on the material surface and within the pores, not only does this raise the energy barrier of the reduction reaction and increase the required reduction temperature, but it also hinders hydrogen permeation and diffusion, resulting in a non-uniform reduction reaction. This makes it difficult to form a continuous and orderly conductive network, easily leading to defects such as disordered distribution of conductive components and poor interfacial bonding. Ultimately, this results in a significant deterioration in the material's conductivity and structural uniformity. Figure 7 As shown.

[0038] Comparative Example 5: The preparation method of the copper sheath cellulose conductive fiber in this comparative example differs from that in Example 1 in that: After copper ion coordination pretreatment, copper sheath cellulose conductive fibers were directly prepared using a traditional liquid phase process of 1wt% sodium borohydride solution, constant temperature liquid phase reduction at 60℃ for 3 hours, water washing and drying, without using the inert atmosphere preheating and hydrogen reduction process of this invention. The copper-sheathed cellulose conductive fibers prepared in this comparative example exhibit poor conductivity, forming only a common copper coating layer on the fiber surface, resulting in poor continuity of internal conductive pathways. Due to alkali treatment disrupting intermolecular hydrogen bonds and the lack of preheating for structural regulation, the fibers exhibit low tensile strength, insufficient interfacial bonding between copper nanoparticles and the cellulose matrix, and are prone to copper layer peeling and detachment after repeated bending and washing, demonstrating poor conductive stability. Figure 8 , Figure 9 As shown.

[0039] The electrical conductivity and breaking strength of the fibers prepared in Examples 1-4 and Comparative Examples 1-5 are compared below, and the results are shown in Table 1.

[0040] Table 1 Fiber Test Results .

[0041] like Figure 1 As shown, the original Lyocell fiber bundle surface structure is relatively loose; CF@Cu was obtained after copper loading modification. 0.2 After fiber deposition, the surface density of the material is significantly enhanced; the obvious difference in morphology between the two is attributed to the formation of a continuous and uniform deposition coating layer by conductive copper nanoparticles on the fiber surface.

[0042] like Figure 2 As shown, the mechanical properties of CF@Cu fibers modified by in-situ copper plating are significantly improved compared to the original lyocell fibers. The original lyocell fibers possess excellent flexibility; however, after constructing a conductive network, the tensile strength and elongation at break are significantly enhanced. This improvement in mechanical properties stems from a dual structural effect: firstly, the copper layer grown in situ on the fiber surface constructs a dense, rigid conductive framework, which can both suppress fiber slippage under stress and effectively transfer stress and alleviate stress concentration; secondly, copper ions undergo intramolecular chelation with the hydroxyl groups of the lyocell molecular chains, and the two form a strong coordination interaction, building a dense physical cross-linked network that resists external forces and enhances fiber rigidity.

[0043] like Figure 3 As shown, to visually demonstrate its application potential, a circuit was built with a small light-emitting diode. The material can stably conduct electricity and illuminate the lamp. Excellent conductivity is a key condition for the flexible sensor to achieve reliable signal transmission. CF@Cu 0.1 CF@Cu 0.15 CF@Cu 0.2 CF@Cu 0.25 The electrical conductivity of the samples was 67.4 S / m, 122.5 S / m, 297.5 S / m, and 445.5 S / m, respectively. With increasing copper ion concentration, copper components were deposited layer by layer onto the fiber surface, forming a dense copper conductive layer, and the material's conductivity improved simultaneously. This phenomenon stems from the synergistic effect of hydrogen reduction and carbon compensation, which ensures both a dense copper coating structure and excellent conductivity, while also constructing a dual-locking structure at the copper-cellulose interface, effectively inhibiting oxidation failure and interface delamination of the conductive layer. During the coordination stage, copper ions form strong coordination bonds with the polar functional groups of the lyocell fiber; during thermal reduction, copper atoms nucleate and grow at anchor points, constructing a highly conductive copper shell. Under high-temperature conditions, the copper layer is easily oxidized to form copper oxide, and the carbon components generated by the pyrolysis and carbonization of cellulose can reduce the oxide in situ, maintaining the stability of the metallic conductive phase and completing structural self-compensation. The aforementioned synergistic effect tightly binds the outer copper shell to the internal fiber skeleton, forming a continuous conductive network.

[0044] like Figure 4 As shown, the CF@Cu test was verified. 0.2 The potential application of flexible wearable sensors in real-time monitoring of movement in multiple parts of the human body. CF@Cu 0.2The fibers are attached to various parts of the human body, capturing and responding in real time to small and large movements such as blinking, swallowing, finger flexion and extension, wrist bending, and leg flexion. The rate of change of resistance ΔR / R0 changes synchronously and stably with deformation, and the signal quickly returns to its initial value after the movement is reset, exhibiting characteristics of fast response, stable signal, and good repeatability. The resistance change curves generated by movements of different parts and amplitudes have obvious characteristic distinctions, proving that CF@Cu 0.2 The sensor can accurately identify subtle and large-scale human movement behaviors and has practical application value in wearable health monitoring, human-computer interaction and other scenarios.

[0045] like Figure 5 As shown, CF@Cu was constructed based on pressure intensity grading. 0.2 The sensor's signal encoding and conversion system, relying on its coral-bud-like microstructure, divides the pressing behavior into low-pressure point signals and high-pressure line marks, corresponding to the basic units of Morse code. Under light pressure, the material primarily exhibits elastic recovery; under heavy pressure, the internal copper layers are fully compressed and interlocked, significantly increasing the contact area and forming a stable conductive path. Combining the standard letter-Morse code mapping relationship, different pressure signals can be converted into electrical signals and decoded to output valid information. Therefore, CF@Cu 0.2 It can be integrated into diving suits as an underwater wearable sensor to monitor finger and wrist movements. In case of distress, the user can reliably output an SOS distress code by pressing the button. Experiments have shown that this method provides stable signal transmission in underwater environments and can meet the needs of safety warnings and emergency calls.

[0046] like Figure 6 As shown, this is to investigate CF@Cu 0.2 Application of dual-mode self-decoupling sensors in sports equipment management: conducting object grasping simulation tests: attaching the sensor to the hand allows for simultaneous sensing of the object's weight and shape, achieving self-decoupling monitoring of pressure and tension dual signals; The test selected three types of equipment: shot put, baseball, and badminton shuttlecock, and simultaneously collected the capacitance and resistance responses: (1) Shot put: When under static pressure, the capacitance signal is stable and the resistance response is weak; when the finger is bent at 32° to grasp the shot, the resistance response is sensitive and the capacitance response is weak. (2) Baseball: When statically compressed, the capacitance response is weak and the resistance response is significant; when bent at 40° and grasped, the resistance continues to respond sensitively and the capacitance remains stable. (3) Badminton shuttlecock: It needs to be bent at 90° to be grasped, and the resistance signal also shows a significant response; The results show that CF@Cu 0.2The sensor can independently decouple and synchronously detect pressure and tension signals during the grasping process, accurately distinguishing differences in object weight and shape. When grasping different types of balls, the signal characteristics are distinct and repeatable, providing reliable technical support for the intelligent identification, classification, and management of ball equipment in sports venues.

[0047] like Figure 7 As shown, if Comparative Example 4 is not preheated at 150 °C in a nitrogen inert atmosphere and is directly reduced with hydrogen, the adsorbed water, impurities, and oxygen-containing functional groups remaining on the material surface and in the pores will significantly increase the energy barrier of the reduction reaction, leading to an increase in the required reduction temperature. At the same time, it will hinder the effective diffusion and penetration of hydrogen, resulting in an uneven and insufficient reduction process, making it difficult to form a continuous, dense, and regular conductive network, and ultimately easily leading to structural defects such as disordered distribution of conductive phase and low interfacial bonding strength.

[0048] like Figure 8 As shown, the sample from the examples exhibits excellent electrical conductivity stability. Comparative Example 1, however, did not undergo interface pre-expansion activation, resulting in insufficient active sites and Cu... 2+ With low loading and weak interfacial bonding, the copper sheath layer is easily peeled off, resulting in a significant decrease in conductivity and stability. Comparative Example 3 uses an unfiltered Cu(OH)2-containing turbid liquid for coordination, resulting in uneven copper source dispersion, uncontrollable nucleation, discontinuous copper sheath layer, poor interfacial bonding, and poor conductivity. Comparative Example 5 uses traditional sodium borohydride liquid-phase reduction without inert atmosphere preheating and high-temperature hydrogen reduction, resulting in low copper layer crystallinity, weak interfacial bonding, and unstable conductive network, thus leading to poor conductivity.

[0049] like Figure 9 As shown, the material obtained by using the traditional sodium borohydride liquid-phase reduction process in Comparative Example 5 exhibits severe agglomeration of copper components, poor conductivity continuity, and weak bonding between the conductive layer and the fiber matrix, ultimately resulting in poor conductivity stability.

[0050] Given that there are numerous embodiments of the present invention, and the raw materials and quantities involved can be selected within a limited range according to actual needs, and that the experimental data for each embodiment are extensive and numerous, it is not suitable to list and describe them one by one here. However, the content to be verified and the final conclusions obtained in each embodiment are similar. Therefore, the verification content of each embodiment will not be described one by one here.

[0051] The above description is merely a detailed explanation of preferred embodiments and principles of the present invention. For those skilled in the art, there may be changes in specific implementation methods based on the ideas provided by the present invention, and these changes should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing copper-sheathed cellulose conductive fibers, characterized in that, Includes the following steps: (1) The cellulose fibers were swollen and then immersed in a copper ion coordination solution to obtain precursor fibers; (2) Pre-treat the precursor fibers at 150-180℃ for 10-30 min under an inert atmosphere to obtain pre-treated fibers; (3) Place the pretreated fiber in a tube furnace, introduce a hydrogen-argon mixed atmosphere, heat to 200-300℃, and keep it at the temperature for 1-3 hours for reduction reaction. After the reaction is completed, cool it to room temperature with the furnace and take it out to obtain copper sheath cellulose conductive fiber.

2. The preparation method according to claim 1, characterized in that, In step (1), swelling is carried out in a 5-15 wt% NaOH solution for a duration of 30-90 min.

3. The preparation method according to claim 1, characterized in that, In step (1), the copper ion coordination solution is a copper ion-alkali mixed solution, and the immersion time is at least 3 hours.

4. The preparation method according to claim 3, characterized in that, The copper ion-alkali mixed solution is an aqueous solution of NaOH (5-15% by mass) and copper sulfate pentahydrate (0.1-0.25M).

5. The preparation method according to claim 1, characterized in that, In step (2), the inert atmosphere is nitrogen or argon.

6. The preparation method according to claim 1, characterized in that, In step (3), the volume ratio of hydrogen to argon in the hydrogen-argon mixed atmosphere is 2:

8.

7. The preparation method according to claim 1, characterized in that, In step (3), the heating rate is 3-5℃·min. -1 .

8. The preparation method according to claim 1, characterized in that, In step (1), before the swelling treatment, the cellulose fibers are also washed with a mixture of ethanol and water.

9. The copper-sheathed cellulose conductive fiber prepared by the preparation method according to any one of claims 1-8, characterized in that, The copper-sheathed cellulose conductive fiber has a cellulose fiber core and a copper sheath.

10. The application of the copper-sheathed cellulose conductive fiber as described in claim 9, characterized in that, Used for flexible sensing.

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