Temperature sensing fiber and preparation method thereof

Abstract

The invention relates to the technical field of functional fiber materials, and particularly discloses a temperature sensing fiber and a preparation method thereof. The temperature sensing fiber comprises a core layer, an inner shell layer and an outer shell layer, the inner shell layer wraps the core layer, the outer shell layer wraps the inner shell layer, the core layer comprises thermoplastic polyurethane, MXene, ferrite and silver nanowires, the inner shell layer comprises oxidized sodium alginate and sericin, and the outer shell layer comprises phenanthroline. The temperature sensing fiber disclosed by the invention realizes full-chain autonomous response of sensing-feedback-repair of fiber damage, and has remarkable advantages in the aspects of structural design, function integration and long-acting stability.

Description

Technical Field

[0001] The present invention relates to the technical field of functional fiber materials, and in particular to a temperature sensing fiber and a preparation method thereof. Background Art

[0002] In recent years, research in the field of smart materials has increasingly focused on self-healing fiber materials, which show broad application prospects in aerospace, smart wearables, medical devices, and other fields. In existing technologies, self-healing fibers primarily achieve damage repair by introducing dynamic chemical bonds (such as hydrogen bonds and reversible covalent bonds) or encapsulating repair agents (such as microcapsules and microvessels). Patent application CN119711253A discloses a self-healing insulating paper based on a microcapsule-encapsulated repair agent. Repair is achieved by triggering the rupture of the microcapsules with an external force, releasing the repair agent. However, this method suffers from low repair efficiency and the inability to repeat repairs. Furthermore, the introduction of microcapsules may reduce the mechanical properties of the substrate, limiting its practical application.

[0003] In terms of damage warning, existing technologies mostly use conductive nanomaterials (such as carbon nanotubes and graphene) or photochromic materials to give fibers sensing functions. The literature "Advanced Functional Materials" (2024, 34 (40): 2404760) reports a hydrophobic carbon black coating based on a conductive network, which achieves damage detection through resistance changes. However, this type of material is not sensitive enough to microcracks, and the breakage of the conductive network may cause irreversible signal failure, making it difficult to accurately determine the degree of damage. In addition, existing warning and repair functions are mostly designed independently and lack a synergistic mechanism, resulting in time lag and spatial misalignment between the damage response and repair process.

[0004] Further analysis revealed that the main problems with existing technologies are: 1) the separation of self-repair and early warning functions, making real-time damage monitoring and targeted repair impossible; 2) the repair process is dependent on external conditions, making it difficult to adapt to complex environments; and 3) material performance degrades significantly after repeated repairs. This is due to the structural design of existing material systems lacking the ability to dynamically regulate the entire chain of damage initiation, early warning, and repair, and the integration of functional units (such as physical blending and simple coating) can easily lead to poor interfacial compatibility and functional failure. Achieving efficient coordination between the fiber's internal sensing and repair units, while improving repair accuracy and cyclic stability without sacrificing mechanical properties, has become a technical bottleneck restricting the development of this field.

[0005] In summary, the development of an intelligent fiber that integrates real-time damage warning, self-triggered precise repair and long-term stability has important scientific value and application needs. Summary of the Invention

[0006] In order to solve the problems in the prior art that the self-repair function is separated from the early warning function, the repair process depends on external conditions, it is difficult to adapt to complex environments, and the material performance is significantly reduced after multiple repairs, the present invention provides a temperature sensing fiber and a preparation method thereof. The fiber has damage early warning and self-repair functions, which greatly expands the practical application prospects of the fiber in protection fields such as flexible electronic textiles.

[0007] To achieve the above objectives, the present invention provides a temperature sensing fiber, comprising a core layer, an inner shell layer, and an outer shell layer, wherein the inner shell layer wraps the core layer, and the outer shell layer wraps the inner shell layer, wherein the core layer comprises thermoplastic polyurethane, MXene, ferrous salt, and silver nanowires, the inner shell layer comprises sodium alginate oxide and sericin, and the outer shell layer comprises o-phenanthroline.

[0008] Preferably, based on the total mass of the core layer, the content of the thermoplastic polyurethane is 10-15 wt.%, more preferably 12.5-13.5 wt.%.

[0009] Preferably, the content of the MXene is 55-70 wt.%, more preferably 60-65 wt.%.

[0010] Preferably, the content of the ferrous salt is 10-15 wt.%, more preferably 10-12.5 wt.%.

[0011] Preferably, the content of the silver nanowires is 10-15 wt.%, more preferably 12.5-15 wt.%.

[0012] Preferably, based on the total mass of the inner shell layer, the content of the oxidized sodium alginate is 50-75 wt.%, more preferably 50-60 wt.%.

[0013] Preferably, the content of the sericin is 25-50 wt.%, more preferably 40-50 wt.%.

[0014] Preferably, in the layer structure of the temperature sensing fiber, the diameter of the core layer is 0.2~0.45mm, preferably 0.29~0.34mm; the thickness of the inner shell layer is 0.25~0.55mm, preferably 0.36~0.43mm; the thickness of the outer shell layer is 9~17μm, preferably 11~15μm.

[0015] Another aspect of the present invention provides a method for preparing the temperature sensing fiber, the method comprising the following steps: 1) Thermoplastic polyurethane, MXene, ferrous salt, silver nanowires and solvent are mixed to prepare a core layer spinning solution; 2) mixing oxidized sodium alginate, sericin, and water to prepare an inner shell spinning solution; 3) using a coaxial wet spinning process to prepare a coaxial fiber by combining the core layer spinning solution prepared in step 1) and the inner shell layer spinning solution prepared in step 2); 4) The coaxial fibers prepared in step 3) are subjected to cross-linking reaction, solvent exchange, phytic acid solution immersion, freezing, and freeze-drying, and then sprayed and / or immersed in o-phenanthroline solution and air-dried.

[0016] Preferably, in step 1), the solvent is at least one of dimethyl sulfoxide, dimethylformamide and dimethylacetamide.

[0017] Preferably, the ferrous salt is at least one of ferrous sulfate, ferrous chloride, ferrous nitrate and ferrous carbonate.

[0018] Preferably, in step 1), the concentration of the thermoplastic polyurethane in the core layer spinning solution is 5-20 mg / mL.

[0019] Preferably, the concentration of the MXene is 40-60 mg / mL.

[0020] Preferably, the concentration of the ferrous salt is 5-15 mg / mL.

[0021] Preferably, the concentration of the silver nanowires is 10-20 mg / mL.

[0022] Preferably, in step 4), the coaxial fibers are mixed with a crosslinking agent solution to undergo a crosslinking reaction, and then solvent exchange is performed with a polyethylene glycol solution. The fibers are then soaked in a phytic acid solution and then frozen and freeze-dried.

[0023] Preferably, the solvent exchange time is 1 to 10 minutes, more preferably 4 to 6 minutes.

[0024] Preferably, the volume concentration of the polyethylene glycol solution is 30-70%, more preferably 45-55%.

[0025] Preferably, the volume concentration of the phytic acid solution is 5-15%, more preferably 7-10%.

[0026] Compared with the existing technology, this application has the following advantages: 1) Compared with existing self-repair fibers, which have the defects of separation of damage warning and repair functions, dependence of repair on external triggering conditions, and performance degradation after repeated repairs, the temperature sensing fiber of this application has both real-time damage warning and self-triggered precise repair functions without sacrificing mechanical properties.

[0027] 2) When the temperature sensing fiber of the present application has cracks (≥10μm), the phenanthroline (Phen) in the outer shell and the Fe in the core layer 2+ Upon full contact, the reaction generates a stable orange-red chelate complex, which can visualize the damaged area without external stimulation.

[0028] 3) The temperature-sensing fiber of this application requires no additional triggering agent, relying instead on the self-repair of imine bonds to promote repair of damaged interfaces. This self-repair process utilizes water molecules as a catalyst to accelerate the dynamic exchange reaction of the imine bonds. When the fiber material is damaged, localized stress concentrations may disrupt the imine bonds. The subsequent dynamic exchange reaction redistributes the stress, and elevated temperature (e.g., frictional heating or ambient heating) increases the mobility of the molecular segments, accelerating bond breakage and recombination.

[0029] 3) The temperature sensing fiber of the present application realizes precise crack filling and mechanical property reconstruction through the dynamic dual network structure of rigid skeleton + flexible dynamic bond. The tensile strength recovery rate after the first repair is ≥92%, the crack filling rate is >95%, and the tensile strength retention rate after 5 cycles of repair is >85%, which is significantly higher than the tensile strength retention rate of the existing technology fiber after 5 cycles of repair (<60%). It realizes the full-chain autonomous response of "perception-feedback-repair" of fiber damage, and has significant advantages in structural design, functional integration and long-term stability.

[0030] 4) The temperature sensing fiber based on damage detection and self-healing technology has high structural stability and functional reproducibility after damage, which can expand its application in the next generation of wearable flexible electronic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a 3D microscope image showing a visual warning of damage to the temperature sensing fiber of the present invention.

[0032] Figure 2 This is an electron microscope image of the temperature sensing fiber of the present invention after breaking and healing.

[0033] Figure 3 This is a graph of the thermoelectric output voltage of the temperature sensing fiber of the present invention under different temperature differences. DETAILED DESCRIPTION

[0034] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0035] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0036] The temperature sensing fiber described in the present invention includes a core layer, an inner shell layer and an outer shell layer, the inner shell layer wraps the core layer, and the outer shell layer wraps the inner shell layer, wherein the core layer includes thermoplastic polyurethane, MXene, ferrous salt and silver nanowires, the inner shell layer includes sodium alginate oxide and sericin, and the outer shell layer includes o-phenanthroline.

[0037] In the temperature sensing fiber of the present invention, the innermost core layer is a thermoelectrically responsive core layer, comprising thermoplastic polyurethane, MXene, ferrous salt, and silver nanowires. Based on the total mass of the core layer, the content of the thermoplastic polyurethane may be 10-15 wt.%, preferably 12.5-13.5 wt.%; the content of the MXene may be 55-70 wt.%, preferably 60-65 wt.%; the content of the ferrous salt may be 10-15 wt.%, preferably 10-12.5 wt.%; and the content of the silver nanowires may be 10-15 wt.%, preferably 12.5-15 wt.%.

[0038] When the temperature sensing fiber is in a high-temperature external environment, the 3D conductive path composed of MXene and silver nanowires in the core layer outputs voltage due to the Seebeck effect.

[0039] In the temperature sensing fiber described herein, the inner shell layer surrounding the core layer serves as a dynamic repair mechanism. The inner shell layer comprises oxidized sodium alginate and sericin. Based on the total mass of the inner shell layer, the oxidized sodium alginate content can be 50-75 wt%, preferably 50-60 wt%, and the sericin content can be 25-50 wt%, preferably 40-50 wt%. The degree of oxidation of the oxidized sodium alginate can be 40-60%.

[0040] In the temperature sensing fiber of the present invention, the outer shell layer is wrapped around the outer periphery of the inner shell layer, and the outer shell layer includes o-phenanthroline. Based on the total mass of the outer shell layer, the content of o-phenanthroline can be 100 wt.%.

[0041] The temperature sensing fiber described in the present invention has a full-chain autonomous response of fiber damage perception-damage feedback-damage repair. When the fiber produces a crack ≥10μm, in the absence of external stimulation, the damaged part will appear orange-red, visualizing the damaged part. At the same time, no additional trigger is required, and the fiber relies on the imine bond for self-repair. During the repair process, water can be used as a catalyst to accelerate the dynamic exchange reaction of the imine bond and promote the repair of the damaged interface. When the fiber material is damaged, local stress concentration may also destroy the imine bond. At this time, the dynamic exchange reaction will redistribute the stress. By increasing the fiber temperature by frictional heat or environmental heating, the mobility of the molecular chain segments can be improved, accelerating the breaking and recombination of the bonds.

[0042] The temperature sensing fiber described in this invention achieves a tensile strength recovery rate of ≥92% after initial damage repair, and maintains a strength recovery rate of over 85% after five repair cycles. Scanning electron microscopy (SEM) observation of the repaired interface reveals a crack filling rate of >95%, an interpenetrating dynamic network with the original matrix, and an interfacial bonding energy of ≥15 kJ / m².

[0043] In the layer structure of the temperature sensing fiber described in the present invention, the diameter of the core layer can be 0.2~0.45mm, preferably 0.29~0.34mm; the thickness of the inner shell layer can be 0.25~0.55mm, preferably 0.36~0.43mm; the thickness of the outer shell layer can be 9~17μm, preferably 11~15μm.

[0044] The preparation method of the temperature sensing fiber comprises the following steps: 1) Thermoplastic polyurethane, MXene, ferrous salt, silver nanowires and solvent are mixed to prepare a core layer spinning solution; 2) mixing oxidized sodium alginate, sericin, and water to prepare an inner shell spinning solution; 3) using a coaxial wet spinning process to prepare a coaxial fiber by combining the core layer spinning solution prepared in step 1) and the inner shell layer spinning solution prepared in step 2); 4) The coaxial fibers prepared in step 3) are subjected to cross-linking reaction, solvent exchange, phytic acid solution immersion, freezing, and freeze-drying, and then sprayed and / or immersed in o-phenanthroline solution and air-dried.

[0045] The specific process of step 1) above may include: first dissolving thermoplastic polyurethane in a solvent, then adding MXene, ferrous salt, and silver nanowires, and then ultrasonically dispersing the resulting mixture for 10-60 minutes to obtain a core layer spinning solution. The solvent may be at least one of dimethyl sulfoxide, dimethylformamide, and dimethylacetamide.

[0046] In the core layer spinning solution, the concentration of the thermoplastic polyurethane may be 5-20 mg / mL, preferably 10-15 mg / mL; the concentration of the MXene may be 40-60 mg / mL, preferably 50-55 mg / mL; the concentration of the ferrous salt may be 5-15 mg / mL, preferably 10-15 mg / mL; and the concentration of the silver nanowires may be 10-20 mg / mL, preferably 10-15 mg / mL.

[0047] In the present invention, the weight average molecular weight of the thermoplastic polyurethane may be 50,000 to 100,000. In some specific embodiments, the thermoplastic polyurethane may be a thermoplastic polyurethane product purchased from Sigma-Aldrich (Shanghai) Trading Co., Ltd. The addition of thermoplastic polyurethane in the present invention can promote the close stacking of the interlayers of MXene, enhance the interfacial bonding, and improve the stability of the fiber structure compared to that without the addition of thermoplastic polyurethane. At the same time, MXene will oxidize at temperatures exceeding 300°C, and thermoplastic polyurethane can improve its antioxidant properties, further improving the conductive stability of the fiber.

[0048] In the present invention, MXene is a two-dimensional layered metal carbide or nitride material. In the MAX phase of its parent material, M is a transition metal, A is primarily a Group IIIA or IVA element such as aluminum or silicon, and X is carbon or nitrogen. The layered two-dimensional material obtained by selectively etching away the A element is called MXene. The MXene described in the present invention can be prepared according to conventional methods in the art. For example, hydrofluoric acid can be used to break the strong chemical bond between the A and M elements in the MAX phase material, thereby selectively etching away the A layer to obtain the MXene. Alternatively, hydrofluoric acid and fluoride salts can be used as etchants to generate hydrofluoric acid in situ to etch the A layer in the MAX phase, thereby obtaining the MXene.

[0049] In the present invention, the ferrous salt may be at least one of ferrous sulfate, ferrous chloride, ferrous nitrate and ferrous carbonate, and is most preferably ferrous sulfate.

[0050] In the present invention, the silver nanowires are not particularly limited and can be purchased commercially or homemade. They can be prepared using conventional methods in the art. For example, they can be prepared by reducing silver ions with polyols. Surfactants can be added during the preparation process to prevent agglomeration. Furthermore, by controlling the reaction conditions, silver nanowires of varying diameters and lengths can be synthesized. In some embodiments, the silver nanowires can have a diameter of 80 to 170 nm and a length of 5 to 6 μm.

[0051] The specific process of the above step 2) may include: mixing oxidized sodium alginate, sericin and water, and then ultrasonically dispersing for 10 to 60 minutes to obtain an inner shell layer spinning solution.

[0052] The concentration of the oxidized sodium alginate in the inner shell layer spinning dope can be 50-150 mg / mL, preferably 100-125 mg / mL; and the concentration of the silk fibroin can be 50-200 mg / mL, preferably 100-150 mg / mL.

[0053] In the present application, the oxidized sodium alginate can be commercially available or prepared according to the conventional preparation method in the art. In some embodiments, the oxidized sodium alginate can be prepared by using sodium alginate and sodium periodate as raw materials for oxidation reaction, and adding ethylene glycol after a period of reaction to terminate the oxidation reaction, so as to control the oxidation degree of the oxidized sodium alginate.

[0054] In the present application, the silk fibroin is a natural macromolecular protein secreted by the silk gland of silkworm. In some embodiments, the silk fibroin can be purchased from Shanghai Maikelin Biochemical Technology Co., Ltd.

[0055] In the above step 3), coaxial fibers are prepared by using coaxial wet spinning process with the core layer spinning dope and the inner shell layer spinning dope, wherein the thermoplastic polyurethane is used as the matrix in the core layer spinning dope, and MXene, ferrous salt and silver nanowire are doped, and the fiber core is formed by wet spinning. When the temperature of the fiber environment is increased, the 3D conductive path composed of MXene and silver nanowire can output voltage due to the Seebeck effect. In the inner shell layer spinning dope, the oxidized sodium alginate is used as the flexible skeleton, and the silk fibroin is introduced to form a dynamic imine bond (-C=N) blending system, and the fiber inner shell layer is formed by wet spinning. The dynamic imine bond can reversibly break / recombine at room temperature, and the oxidized sodium alginate provides high flame retardancy (LOI=40%), ensuring the thermoelectric stability of the functional particles in the core layer.

[0056] In the coaxial wet spinning process, the core layer spinning dope and the inner shell layer spinning dope are injected into the inner and outer coaxial needle by using different injection pumps, and the injection speed can be 450-550 μL / min. The spinning temperature is 20-40℃, and the collection roller linear speed is 10-30 m / min. The nozzle diameter of the coaxial needle is 0.1-0.7 mm, and is further preferably 0.2-0.5 mm, and the draw ratio is 4-10 times, and is further preferably 5-8 times. The fiber inner diameter is accurately controlled by the nozzle diameter and the draw ratio.

[0057] In some embodiments, the specific process of step 4) includes: mixing the coaxial fiber with a crosslinker solution and causing a crosslinking reaction, then performing a solvent exchange with a polyethylene glycol solution, then soaking it with a phytic acid solution, and then freezing and freeze-drying to obtain an aerogel fiber, and then spraying the surface of the aerogel fiber with a phenanthroline solution, and / or immersing the aerogel fiber in the phenanthroline solution so that a layer of phenanthroline is evenly attached to the surface of the aerogel fiber, thereby obtaining the temperature sensing fiber of the present invention. In the above embodiment, the reaction between the coaxial fiber and the crosslinker solution will produce a hydrogel fiber, and in the subsequent solvent exchange process, part of the water in the hydrogel fiber is replaced by the polyethylene glycol solution.

[0058] In the present invention, the crosslinking agent is not particularly limited, and conventional crosslinking agents in the art can be used. In some embodiments, the crosslinking agent is at least one of CaCl2, SrCl2, BaCl2, and MgCl2. The concentration of the crosslinking agent solution can be 2-5 wt.%.

[0059] When using a polyethylene glycol solution for solvent exchange, the volume concentration of the polyethylene glycol solution can be 30-70%, preferably 45-55%. The solvent exchange time can be 1-10 minutes, preferably 4-6 minutes. In the present invention, controlling the solvent exchange time can ensure that only a portion of the water in the hydrogel fiber is replaced by the polyethylene glycol solution. The solvent exchange time described in the present invention can be 1-10 minutes, preferably 4-6 minutes.

[0060] The volume concentration of the phytic acid solution of the present invention can be 5-15%, preferably 7-10%. The fiber after cross-linking with low concentration of phytic acid has a sparse cross-linked network and low mechanical strength (lack of tensile strength and modulus), which is prone to swelling or fracture. After cross-linking with high concentration of phytic acid, the fiber network is too dense, the fiber becomes brittle, and the elongation at break decreases, which may increase fragility due to internal stress concentration. The above-mentioned optimal cross-linking concentration can form a uniform network structure, significantly improve the tensile strength and elastic modulus of the fiber, and maintain a certain toughness.

[0061] The concentration of the o-phenanthroline solution of the present invention can be 1-10 wt.%.

[0062] The temperature sensing fiber prepared according to the method of the present invention has a diameter of 0.7-1.5 mm and a linear density of 98-105 tex. Moreover, the tensile strength recovery rate of the temperature sensing fiber after the initial damage repair is ≥92%, and the strength recovery rate can still be maintained above 85% after five cycles of repair. Scanning electron microscopy (SEM) observation of the repair interface shows that the crack filling rate is greater than 95%, the dynamic network forms an interpenetrating structure with the original matrix, and the interface binding energy is ≥15 kJ / m².

[0063] The temperature sensing fiber and the preparation method thereof according to the present application are further illustrated by the following examples. The examples are implemented on the premise of the technical solutions of the present application, and detailed implementation modes and specific operation processes are given, but the protection scope of the present application is not limited to the following examples.

[0064] In the following examples, the experimental methods are all conventional methods in the art unless otherwise specified. The experimental materials used in the following examples are all commercially available unless otherwise specified.

[0065] Example 1 1) Preparation of oxidized sodium alginate (POSA) 4 g of sodium alginate SA was dissolved in 200 mL of distilled water to obtain a 2 wt.% sodium alginate solution. Then, 2.4 g of NaIO4 was introduced into the SA solution, and after reacting in the dark at a temperature of 30℃ for 24 h, 0.8 mL of EG and 1.2 g of NaCl were added to the mixture, followed by continuous stirring for 30 min to complete the oxidation reaction. The obtained precipitate was extracted with ethanol, and then purified with distilled water for three times. Finally, a white precipitate of POSA was obtained by freeze-drying.

[0066] 2) Preparation of silver nanowires (Ag NWs) Ag NWs were synthesized using the standard polyol method, first 20 mL of EG was heated in an oven at 160℃ for 1 h, then cooled to 47.6℃. Subsequently, 0.1 g of FeCl3 and 0.052 g of PVP were dissolved in the cooled EG solution, and stirred in an oil bath for 1.5 h. Then, AgNO3 was added to the mixture and stirred for 10 min until completely dissolved. Then the solution was placed in an oven at 180℃ for 7 h until a gray dispersion was formed. After cooling the gray dispersion to room temperature, it was collected by centrifugation and washed with ethanol to obtain pure Ag NWs.

[0067] 3) Preparation of MXene nanosheets MXene nanoplatelets dispersion was prepared by acid etching of Ti3AlC2 powder with a HC1 / LiF mixture. First, 1.6 g of LiF was mixed with 20 mL of 12 mol / L HC1 and magnetically stirred for 40 min. Subsequently, 1.6 g of Ti3AlC2 was added to the solution and the mixture was stirred thoroughly for 24 h to ensure complete removal of the aluminum layer. The resulting dispersion was washed thoroughly with distilled water for 10 min by centrifugation at 3000 rpm until the pH of the supernatant was above 6. The MXene precipitate was then sonicated for 2.5 h and centrifuged again at 3000 rpm to obtain the single-layer dispersed MXene nanoplatelets. Finally, the desired MXene nanoplatelets were collected by freeze-drying.

[0068] 4) Preparation of coaxial fiber A TPU solution was prepared by mixing 0.1 g of thermoplastic polyurethane (TPU) particles (purchased from Sigma-Aldrich (Shanghai) Trading Co., Ltd.) with 10 mL of dimethyl sulfoxide (DMSO) solvent and stirring for 3 h. Thereafter, 0.5 g of MXene (50 mg / mL) prepared in step 3), 0.1 g of Ag NWs (10 mg / mL) prepared in step 2), and 0.1 g of Fe2SO4(10 mg / mL) prepared in step 1) were added to the TPU solution to form a core layer spinning dope. Subsequently, 1 g of sericin protein (SS) (purchased from Shanghai Maikelin Biochemical Technology Co., Ltd.) and 1.3 g of POSA prepared in step 1) were mixed with 10 mL of deionized water to prepare an inner shell layer spinning dope. The core and inner shell spinning dopes were injected into the inner and outer coaxial needles using separate syringe pumps, with the injection speed of the inner needle (22G, inner diameter: ~0.41 mm) and the outer needle (14G, inner diameter: ~1.60 mm) set to 500 μL / min.

[0069] 5) Preparation of temperature sensing fiber The coaxial fiber prepared in step 4) was transferred into a coagulation bath with a concentration of 4 wt.% CaCl2, resulting in Ca 2+ Cross-linked newborn hydrogel fiber. The newborn hydrogel fiber was immersed in a polyethylene glycol aqueous solution (volume ratio of polyethylene glycol to water was 1:2) to replace part of the water in the newborn hydrogel fiber with EG solution, and after 1 min, the fiber was immersed in a PA aqueous solution with a volume concentration of 7%. Thereafter, the fiber was frozen at -20 ℃ and freeze-dried for 24 h to produce an aerogel fiber. Finally, the surface of the aerogel fiber was sprayed with a 10 mg / mL phenanthroline (Phen) aqueous solution to obtain the temperature sensing fiber A1 described in the present application.

[0070] Example 2 The difference from Example 1 is that: 4) Preparation of coaxial fiber A TPU solution was prepared by mixing 0.05 g of thermoplastic polyurethane (TPU) particles with 10 mL of dimethyl sulfoxide (DMSO) solvent and stirring for 3 h. Thereafter, MXene (50 mg / mL) prepared in step 3), Ag NWs (15 mg / mL) prepared in step 2), and Fe2SO4(5 mg / mL) were added to the TPU solution to form a core layer spinning dope. Subsequently, 1.5 g of sericin (SS) and 2 g of POSA prepared in step 1) were mixed with 10 mL of deionized water to prepare an inner shell layer spinning dope. The core and inner shell spinning dopes were injected into an inner-outer coaxial needle using separate syringe pumps, with the injection speed of the inner needle (22G, inner diameter: ~0.41 mm) and the outer needle (14G, inner diameter: ~1.60 mm) set to 500 μL / min.

[0071] 5) Preparation of temperature sensing fiber The coaxial fiber prepared in step 4) was transferred into a coagulation bath with a concentration of 4 wt.% CaCl2, resulting in Ca 2+ The newly born hydrogel fiber was immersed in a polyethylene glycol aqueous solution (volume ratio of polyethylene glycol to water was 1:1) to replace part of the water in the newly born hydrogel fiber with EG solution. After 1 min, the fiber was immersed in a PA aqueous solution with a volume concentration of 7%. Thereafter, the fiber was frozen at -20 ℃ and freeze-dried for 24 h to produce an aerogel fiber. Finally, the surface of the aerogel fiber was sprayed with a 10 mg / mL aqueous solution of phenanthroline (Phen) to obtain the temperature sensing fiber A2 described in the present application.

[0072] Example 3 The difference from Example 1 is that: 4) Preparation of coaxial fiber A TPU solution was prepared by mixing 0.05 g of thermoplastic polyurethane (TPU) particles with 10 mL of dimethyl sulfoxide (DMSO) solvent and stirring for 3 h. Thereafter, MXene (50 mg / mL) prepared in step 3), Ag NWs (15 mg / mL) prepared in step 2), and Fe2SO4(5 mg / mL) were added to the TPU solution to form a core layer spinning dope. Subsequently, 1.5 g of sericin (SS) and 2 g of POSA prepared in step 1) were mixed with 10 mL of deionized water to prepare an inner shell layer spinning dope. The core and inner shell spinning dopes were injected into an inner-outer coaxial needle using separate syringe pumps, with the injection speed of the inner needle (22G, inner diameter: ~0.41 mm) and the outer needle (14G, inner diameter: ~1.60 mm) set to 500 μL / min.

[0073] 5) Preparation of temperature sensing fiber The coaxial fiber prepared in step 4) was transferred to a coagulation bath with a concentration of 4 wt.% CaCl2 to produce Ca 2+ Cross-linked nascent hydrogel fibers. The nascent hydrogel fibers were immersed in a polyethylene glycol (PEG) aqueous solution (polyethylene glycol:water volume ratio of 1:0.5) to partially replace the water in the nascent hydrogel fibers with PEG solution. After 1 minute, the fibers were immersed in a 7% PA aqueous solution. The fibers were then frozen at -20°C and freeze-dried for 24 hours to produce aerogel fibers. Finally, the surface of the aerogel fibers was sprayed with a 10 mg / mL phenanthroline (Phen) aqueous solution to produce the temperature sensing fiber A3 described herein.

[0074] Example 4 The difference from Example 1 is that the concentration of thermoplastic polyurethane in the core layer spinning solution is 20 mg / mL.

[0075] The temperature sensing fiber A4 was prepared using the preparation method of Example 4.

[0076] Example 5 The difference from Example 1 is that the concentration of MXene in the core layer spinning solution is 60 mg / mL.

[0077] The temperature sensing fiber A5 was prepared using the preparation method of Example 5.

[0078] Example 6 The difference from Example 1 is that the concentration of ferrous salt in the core layer spinning solution is 15 mg / mL.

[0079] The temperature sensing fiber A6 was prepared using the preparation method of Example 6.

[0080] Example 7 The difference from Example 1 is that in step 5), the solvent exchange time is 10 min.

[0081] The temperature sensing fiber A7 was prepared using the preparation method of Example 7.

[0082] Example 8 The difference from Example 1 is that in step 5), the volume concentration of the PA aqueous solution is 15%.

[0083] The temperature sensing fiber A8 was prepared using the preparation method of Example 8.

[0084] Comparative Example 1 The difference from Example 1 is that in step 4) of preparing the coaxial fiber, Fe2SO4 is not added when preparing the core layer spinning solution, and fiber B1 is prepared.

[0085] Comparative Example 2 The difference from Example 1 is that in step 5) of preparing the temperature sensing fiber, the surface of the aerogel fiber obtained after freeze-drying does not need to be sprayed with a phenanthroline (Phen) aqueous solution, and the fiber B2 without an outer shell layer is prepared.

[0086] Comparative Example 3 The difference from Example 1 is that in step 4) of preparing the coaxial fibers, only the core spinning solution was prepared. This core spinning solution was then injected into a uniaxial needle (14G, inner diameter: ~1.60 mm) using a separate syringe pump at an injection rate of 500 μL / min. After solidification in water, the fibers were frozen at -20°C and freeze-dried for 24 hours to produce aerogel fibers. Finally, the surface of the aerogel fibers was sprayed with a 10 mg / mL aqueous solution of o-phenanthroline (Phen) to obtain fibers B3 without an inner shell layer.

[0087] Comparative Example 4 The difference from Example 1 is that in step 4) of preparing the coaxial fiber, only the inner shell spinning dope was prepared. This inner shell spinning dope was then injected into a uniaxial needle (14G, inner diameter: ~1.60 mm) using a separate syringe pump at an injection rate of 500 μL / min. After solidification in water, the fiber was frozen at -20°C and freeze-dried for 24 hours to produce the aerogel fiber. Finally, the surface of the aerogel fiber was sprayed with a 10 mg / mL aqueous solution of o-phenanthroline (Phen) to obtain fiber B4 without a core layer.

[0088] Comparative Example 5 A TPU solution was prepared by mixing 0.1 g TPU with 10 mL DMSO solvent and stirring for 3 h. Thereafter, 0.5 g MXene (50 mg / mL) prepared in Example 1 Step 3), 0.1 g Ag NWs (10 mg / mL) prepared in Example 1 Step 2) and 0.1 g Fe2SO4 (10 mg / mL) prepared in Example 1 Step 2) were added to the TPU solution to form a homogeneous solution C1. Subsequently, 1 g sericin (SS) and 1.3 g POSA prepared in Example 1 Step 1) were mixed with 10 mL DMSO to prepare a homogeneous solution C2. The C1 and C2 solutions were mixed to obtain a spinning dope C3. The spinning dope C3 was injected into a single-axial needle (14G, inner diameter: ~1.60 mm) using a syringe pump, and the injection speed was set to 500 μL / min. After coagulation in water, the fibers were frozen at -20 °C and freeze-dried for 24 h to produce aerogel fibers. Finally, the surface of the aerogel fibers was sprayed with a 10 mg / mL aqueous Phen solution to obtain the fiber B5 with a non-coaxial structure.

[0089] Test Example 1 Self-warning repair function detection The fiber prepared in Example 1 was detected by scanning electron microscopy, and the results are shown in Figure 1-2 .

[0090] As can be seen from Figure 1 , when the fiber is damaged, the damaged part changes from yellow to red within a few seconds, giving an independent warning of the damaged part and accurately locating the damaged location.

[0091] As can be seen from Figure 2 , the damaged and disconnected fiber can be self-healed within 24 h in a room temperature (relative humidity 20%-40%) environment. At the same time, after the damage began, the resistance of the fiber was monitored and increased from 30.06 kΩ to 10 5 kΩ. After healing, due to the fusion of TPU during the healing process, the resistance almost returned to the original level, reestablishing the conductive path, which also proves that the fiber has completed self-repair.

[0092] Test Example 2 High-temperature environment performance test Using the characteristic that electrons move from the heated side to the cooler side under temperature difference, the voltage change of the temperature sensing fiber of Example 1 at different temperatures was tested and evaluated. Specifically, two copper strips were used to connect the two ends of the STDF fiber in parallel with the voltage test equipment, and an external heat source was provided by a heating plate. The test results are shown in Figure 3 .

[0093] As can be seen from Figure 3It can be seen that when the heating element is used to generate temperature differences of 100, 200, 300, 400, and 500 K, the corresponding maximum output voltages of the temperature sensing fiber are 0.89, 1.90, 3.10, 4.11, and 4.95 mV, respectively. The fiber's ability to directly convert thermal energy into electrical energy is enabled by the potential difference generated by internal charge carriers along the high-temperature region. The stability of the output voltage indicates that the sensor can effectively detect temperature, demonstrating the highly sensitive temperature monitoring performance of the temperature sensing fiber of the present invention.

[0094] Test Example 3 The relevant properties of the fibers prepared in Examples 1-8 and Comparative Examples 1-5 were tested, and the test results are shown in Table 1: Table 1

[0095] It can be seen from the results in Table 1 that the temperature sensing fiber prepared by the method described in the present invention has excellent damage self-monitoring characteristics, high healing efficiency, and a wide high-temperature warning temperature monitoring range. As a visual damage warning intelligent temperature sensor, it has significantly better effects.

[0096] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A temperature sensing fiber, characterized in that: The temperature sensing fiber includes a core layer, an inner shell layer and an outer shell layer, wherein the inner shell layer wraps the core layer, and the outer shell layer wraps the inner shell layer, wherein the core layer includes thermoplastic polyurethane, MXene, ferrous salt and silver nanowires, the inner shell layer includes oxidized sodium alginate and sericin, and the outer shell layer includes o-phenanthroline.

2. The temperature sensing fiber according to claim 1, characterized in that: Based on the total mass of the core layer, the content of the thermoplastic polyurethane is 10-15 wt.%, preferably 12.5-13.5 wt.%; and / or The content of the MXene is 55-70 wt.%, preferably 60-65 wt.%; and / or The content of the ferrous salt is 10-15 wt.%, preferably 10-12.5 wt.%; and / or The content of the silver nanowires is 10-15 wt.%, preferably 12.5-15 wt.%.

3. The temperature sensing fiber according to claim 1 or 2, characterized in that: Based on the total mass of the inner shell layer, the content of the oxidized sodium alginate is 50-75 wt.%, preferably 50-60 wt.%; and / or The content of the sericin is 25-50 wt.%, preferably 40-50 wt.%.

4. The temperature sensing fiber according to any one of claims 1 to 3, characterized in that: In the layer structure of the temperature sensing fiber, the diameter of the core layer is 0.2-0.45 mm, preferably 0.29-0.34 mm; the thickness of the inner shell layer is 0.25-0.55 mm, preferably 0.36-0.43 mm; and the thickness of the outer shell layer is 9-17 μm, preferably 11-15 μm.

5. The method for preparing the temperature sensing fiber according to any one of claims 1 to 4, characterized in that: The preparation method comprises the following steps: 1) Thermoplastic polyurethane, MXene, ferrous salt, silver nanowires and solvent are mixed to prepare a core layer spinning solution; 2) mixing oxidized sodium alginate, sericin, and water to prepare an inner shell spinning solution; 3) using a coaxial wet spinning process to prepare a coaxial fiber by combining the core layer spinning solution prepared in step 1) and the inner shell layer spinning solution prepared in step 2); 4) The coaxial fibers prepared in step 3) are subjected to cross-linking reaction, solvent exchange, phytic acid solution soaking, freezing, and freeze-drying, and then sprayed and / or immersed in o-phenanthroline solution and air-dried.

6. The preparation method according to claim 5, characterized in that In step 1), the solvent is at least one of dimethyl sulfoxide, dimethylformamide and dimethylacetamide; and / or The ferrous salt is at least one of ferrous sulfate, ferrous chloride, ferrous nitrate and ferrous carbonate.

7. The preparation method according to claim 5 or 6, characterized in that: In step 1), in the core layer spinning solution, the concentration of the thermoplastic polyurethane is 5-20 mg / mL, the concentration of the MXene is 40-60 mg / mL, the concentration of the ferrous salt is 5-15 mg / mL, and the concentration of the silver nanowires is 10-20 mg / mL.

8. The preparation method according to any one of claims 6 to 7, characterized in that In step 4), the coaxial fibers are mixed with a crosslinking agent solution to undergo a crosslinking reaction, and then solvent exchange is performed with a polyethylene glycol solution. The fibers are then soaked in a phytic acid solution and then frozen and freeze-dried.

9. The preparation method according to claim 8, characterized in that The solvent exchange time is 1 to 10 minutes, preferably 4 to 6 minutes.

10. The preparation method according to claim 8, characterized in that The volume concentration of the polyethylene glycol solution is 30-70%, preferably 45-55%; and / or The volume concentration of the phytic acid solution is 5-15%, preferably 7-10%.

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