Strain sensing fiber and preparation and use thereof

Abstract

The present application relates to a kind of strain sensing fiber and its preparation and application, the fiber includes core layer and sheath layer, wherein core layer is high-elastic polymer layer;Sheath layer includes high-elastic polymer layer loaded with carbon nanotube and silver nanoparticles;Wherein core layer is solid structure;High-elastic polymer layer loaded with carbon nanotube in sheath layer has network porous structure, and network porous structure fixes silver nanoparticles in situ.The present application strain sensing fiber has large tensile property, ultra-high sensitivity, fast deformation response ability, wide strain monitoring range and the like advantages, has important application prospect in human motion monitoring, intelligent wearable device, biological medical diagnosis, soft robot field.

Description

Technical Field

[0001] This invention belongs to the field of functional fibers, and specifically relates to a strain sensing fiber and its preparation and application. Background Technology

[0002] The research on fiber strain sensors holds significant scientific importance and immense application potential. Their unique flexible structure and weaveability allow for more precise bonding or weaving into various media, thereby improving the accuracy of deformation monitoring and exhibiting excellent adaptability in various dynamic environments. This greatly expands their application scope in fields such as smart wearables, medical monitoring, and motion tracking. In-depth exploration of the performance characteristics of fiber strain sensors and optimization of their material systems and manufacturing processes will not only contribute to the innovative development of smart wearable technology but also provide innovative solutions for various industries, ultimately improving human quality of life and productivity. Therefore, the research on fiber strain sensors has significant theoretical and practical value and a profound strategic impact on advancing smart technologies.

[0003] Current fiber-optic strain sensors face challenges such as limited sensing range and low sensitivity, with most only capable of detecting deformation within 100% of the strain. An ideal fiber-optic strain sensor not only needs a wide sensing range to meet the requirements of detecting objects with large deformations, but also should possess excellent sensitivity, rapid response, and sustained mechanical and electrical stability. Such an ideal fiber-optic strain sensor holds significant promise for applications in fields such as intelligent wearable devices, intelligent robots, and biomedical electronic devices that handle complex deformations.

[0004] In conclusion, developing a type of strain sensing fiber with ultra-sensitive wide sensing range has significant scientific and practical value. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the technical problem this invention aims to solve is to provide a strain-sensing fiber and its preparation and application. This invention significantly increases the specific surface area of ​​the strain-sensing fiber by constructing a core-sheath structure with a porous network surface. Furthermore, a layer of silver nanoparticles is in-situ fixed and loaded onto the surface of the network fiber, synergistically reinforcing the sensing layer with carbon nanotubes in the fiber sheath after wet spinning. This achieves the preparation of a strain-sensing fiber that meets the requirements of large strain deformation, wide sensing range, high sensitivity, and rapid response, providing new design ideas and technical support for the design of high-performance sensing fibers.

[0006] This invention provides a strain-sensing fiber, the fiber comprising a core layer and a sheath layer, wherein the core layer is a highly elastic polymer layer; the sheath layer comprises a highly elastic polymer layer loaded with carbon nanotubes and silver nanoparticles; wherein the core layer has a solid structure; the highly elastic polymer layer loaded with carbon nanotubes in the sheath layer has a network-like porous structure, and the network-like porous structure fixes the silver nanoparticles in situ; wherein the highly elastic polymer is a polystyrene block copolymer.

[0007] Preferably, the polystyrene block copolymer is one or more of polystyrene-polyisoprene-polystyrene, polystyrene-ethylene-butene-polystyrene, and polystyrene-polybutadiene-polystyrene.

[0008] Preferably, the average particle size of the silver nanoparticles is 100-150 nm.

[0009] Preferably, the carbon nanotubes in the highly elastic polymer layer loaded with carbon nanotubes are 1-10 wt% of the highly elastic polymer.

[0010] This invention provides a method for preparing strain-sensing fibers, comprising the following steps:

[0011] Step (1) Mix the high-elasticity polymer and solvent to obtain the core spinning solution; mix the carbon nanotubes, high-elasticity polymer and solvent to obtain the sheath spinning solution, and perform coaxial wet spinning to obtain coaxial fibers; the high-elasticity polymer is a polystyrene block copolymer;

[0012] Step (2) Immerse the coaxial fiber in a metal salt solution, dry it, then immerse it in a reducing solution and dry it to obtain strain sensing fiber.

[0013] Preferably, the polystyrene block copolymer in step (1) is one or more of polystyrene-polyisoprene-polystyrene, polystyrene-ethylene-butene-polystyrene, and polystyrene-polybutadiene-polystyrene.

[0014] The solvent in step (1) is one or more of the following: ethanol, deionized water, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, hydrazine hydrate, acetone, dichloromethane, chloroform, toluene, chlorobenzene, tetrahydrofuran, and dimethyl sulfoxide.

[0015] Preferably, in step (1), the concentration of the high-elasticity polymer in the core spinning solution is 25-50 wt%; and the concentration of the high-elasticity polymer in the sheath spinning solution is 1-24 wt%.

[0016] Preferably, in step (1), the carbon nanotubes in the sheath spinning solution are 1-10 wt% of a highly elastic polymer.

[0017] Preferably, the coaxial wet spinning process parameters in step (1) are as follows: the coaxial needle size is 14G-18G, and the core layer spinning solution propulsion speed is 1-150 mL·h. -1 The propulsion speed of the sheath spinning solution is 1-80 mL·h -1 The coagulation bath is an anhydrous ethanol solution; the collecting roller speed is 1-20 r / min.

[0018] In step (1), the high-elasticity polymer and solvent are mixed in the spinning solution of the core layer at 20℃~100℃ for 2~6h.

[0019] Step (1) The sheath spinning solution is a mixture of carbon nanotubes and solvent, and a high-elasticity polymer is added and stirred for 0.5-6 h.

[0020] The dispersion treatment includes one or more of the following: water bath ultrasonic dispersion, mechanical stirring, high-speed shear dispersion, and tip ultrasonic dispersion (cell disruption treatment).

[0021] The dispersion process is described as a high-tip ultrasonic dispersion with a processing power of 30-300 W and a processing time of 5-60 minutes.

[0022] Preferably, in step (2), the metal salt solution is one or more of silver trifluoroacetate solution, silver ammonia solution, and silver nitrate solution; the reducing solution is one or more of hydrazine hydrate solution, ascorbic acid solution, and glucose solution.

[0023] Preferably, the concentration of the metal salt solution in step (2) is 1-20 wt%; and the concentration of the reducing solution is 1-30 wt%.

[0024] Preferably, the immersion time in the metal salt solution in step (2) is 0.1-3 hours; the immersion time in the reducing solution is 0.1-3 hours.

[0025] Preferably, in step (2), the metal salt solution is immersed in the solution, dried, and then immersed in a reducing solution. The drying process is repeated 1-5 times.

[0026] The drying process in step (2) includes one or more of the following: freeze drying, supercritical drying, and vacuum heating drying. Further, the drying is vacuum heating drying.

[0027] This invention provides an application of the strain-sensing fiber in the fields of human motion monitoring, smart wearable devices, biomedical diagnostics, and soft robotics.

[0028] This invention realizes a core-sheath structure strain sensing fiber with a porous network surface. Specifically, the core layer of the sensing fiber has a solid structure, which enhances the mechanical properties of the sensing fiber; the highly elastic polymer layer loaded with carbon nanotubes in the sheath layer is spun to obtain a network porous surface structure, which gives the sensing fiber high stretchability (sensing operating range); in addition, the network porous surface sheath layer increases the specific surface area of ​​the fiber and provides a large number of channels for the in-situ fixation of silver nanoparticles, which is conducive to the large loading of silver nanoparticles and enhances the sensitivity of the sensing fiber.

[0029] This invention employs a combination of wet spinning and dip-coating reduction treatment to fabricate fiber-based strain sensors with large deformation, high sensitivity, and a wide sensing range. The core spinning solution has a high polymer concentration, while the sheath spinning solution has a low polymer concentration. Coaxial wet spinning yields a porous core-sheath structure fiber. Furthermore, due to the interaction between the solid conductive filler carbon nanotubes in the sheath spinning solution and the highly elastic polymer, a uniform distribution of the solid conductive filler carbon nanotubes is achieved in the sheath layer. In addition, the porous sheath layer increases the specific surface area of ​​the fiber, providing channels for the extensive immersion of metal salt solutions. Repeated processing yields high-performance core-sheath structure strain-sensing fibers.

[0030] The present invention relates to a strain sensing fiber with a network-like porous surface core-sheath structure. The surface sheath layer is composited with a variety of conductive fillers. During the stretching process, the fiber surface sheath layer exhibits both silver nanoparticle layer crack propagation and carbon nanotube sliding orientation, enabling the fiber to adapt to large deformation monitoring and maintain relatively stable sensing or electrical properties.

[0031] Beneficial effects

[0032] The core-sheath structure strain sensing fiber of this invention has a large strain deformation capability, a wide sensing range, a tensile deformation range of 1% to 500%, and ultra-high sensitivity, fast response capability, and excellent sensing stability under large strain. It greatly improves the application of sensing fibers in wearable deformation monitoring, infrastructure monitoring, and robotic flexible electronic skin, and is suitable for wearable devices, electronic skin, and infrastructure monitoring with higher performance requirements.

[0033] This invention has low production costs and a simple production process, enabling large-scale fiber production and possessing the potential for large-scale production. Attached Figure Description

[0034] Figure 1 This is a scanning electron microscope image of the surface of the strain-sensing fiber with a core-sheath structure in Example 1;

[0035] Figure 2 This is a cross-sectional scanning electron microscope image of the strain-sensing fiber of the core-sheath structure in Example 1;

[0036] Figure 3(a) is the stress-strain curve of the strain sensing fiber of the core-sheath structure in Example 1 after stretching; (b) is the strain curve of resistance change after stretching.

[0037] Figure 4 These are the stress and resistance variation curves of the core-sheath structure strain-sensing fiber in Example 1 under different small strain deformations;

[0038] Figure 5 Example 1 shows the resistance change over time of the core-sheath structure strain-sensing fiber during cyclic tensile testing at different high strain levels at room temperature.

[0039] Figure 6 This is the response speed curve of the strain-sensing fiber with a core-sheath structure in Example 1 under 1% strain;

[0040] Figure 7 Example 1 shows a core-sheath structure strain-sensing fiber woven into a fabric for monitoring small deformations of the human body;

[0041] Figure 8 Example 1 shows a core-sheath structure strain-sensing fiber woven into a fabric for monitoring large deformations of human joints;

[0042] Figure 9 (a) is the stress-strain curve of the strain sensing fiber of the core-sheath structure in Example 2 after stretching; (b) is the strain curve of resistance change after stretching.

[0043] Figure 10 Example 2 shows the resistance change over time of the core-sheath structure strain-sensing fiber during cyclic tensile testing at different high strain levels at room temperature;

[0044] Figure 11 Example 2 shows the resistance change curve generated after the pneumatic actuator deforms, where the core-sheath structure strain sensing fiber is seamlessly integrated onto the surface of a cylindrical pneumatic actuator.

[0045] Figure 12 (a) is the stress-strain curve of the strain sensing fiber of the core-sheath structure in Example 3 after stretching; (b) is the strain curve of resistance change after stretching.

[0046] Figure 13 Example 3 shows the resistance change over time of the core-sheath structure strain-sensing fiber during cyclic tensile testing at different high strain levels at room temperature;

[0047] Figure 14 This is a scanning electron microscope image of the surface in Comparative Example 1;

[0048] Figure 15 This is a cross-sectional scanning electron microscope image of Comparative Example 1;

[0049] Figure 16This is a comparison graph of the performance of Example 1 and Comparative Example 1 in uniaxial tensile tests at room temperature;

[0050] Figure 17 (a) is the stress-strain curve after stretching in Comparative Example 2; (b) is the strain curve after stretching due to resistance change.

[0051] Figure 18 This is a comparison chart of the sensing performance of the core-sheath structure strain sensing fibers of Examples 1-3 and Comparative Example 2;

[0052] Figure 19 This is a cross-sectional scanning electron microscope image of the core-sheath coaxial fiber based on thermoplastic polyurethane as the elastic matrix in Comparative Example 3.

[0053] Figure 20 This is a scanning electron microscope (SEM) image of the core-sheath coaxial fiber based on thermoplastic polyurethane as the elastic matrix in Comparative Example 3. Detailed Implementation

[0054] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0055] Relevant tests involved in the examples and comparative examples:

[0056] (1) Test method for fiber average diameter and cross-sectional area: Five core-sheath strain sensing fibers were selected and their cross-sectional morphology was photographed using a scanning electron microscope. Based on the electron microscope images of the cross-sections of the core-sheath strain sensing fibers, the average cross-sectional area of ​​the fibers was measured and calculated using ImageJ image analysis software.

[0057] (2) Test method for mechanical properties of core-sheath strain sensing fiber; First, cut the core-sheath strain sensing fiber into 40 mm lengths, take 10 core-sheath strain sensing fibers and fix them on a standard cardboard, and place them at room temperature under standard atmospheric pressure for 6 hours; Use a universal testing machine to perform tensile mechanical tests on each core-sheath strain sensing fiber sample. The test parameters are: sample gauge length l0 is 20 mm, tensile speed is 20 mm / min. -1 Finally, the stress-strain curve for each fiber sample was obtained. The formulas for calculating the fiber's breaking strength σ and breaking elongation ε are as follows:

[0058] ,

[0059] In the formula: F i The breaking strength of the i-th fiber (in N).

[0060] S0 is the initial cross-sectional area of ​​the fiber (unit: mm). 2 );

[0061] L i The tensile fracture length of the i-th fiber (in mm).

[0062] L0 is the gauge length for holding the fiber (20 mm).

[0063] (3) During the tensile test of the core-sheath strain sensing fiber under standard atmospheric pressure and room temperature conditions, the resistance change was measured simultaneously: The fiber was cut to a length of 40 mm, and copper foil tape was used as test electrodes at both ends of the fiber. Liquid metal was coated at the connection between the core-sheath strain sensing fiber and the copper foil electrode to ensure full contact between the fiber and the electrode. After being placed at room temperature under standard atmospheric pressure for 6 hours, tensile mechanical and electrical tests were performed on each core-sheath strain sensing fiber sample using a universal testing machine and a source meter (Keithey 2450). Test parameters: Gauge length l0 of the sample was 20 mm, and the tensile speed was 20 mm / min. -1 The tensile strain was set to 10%, 50%, and 100%, respectively. The stress-strain curves and resistance change curves of each core-sheath structure strain-sensing fiber sample were then obtained.

[0064]

[0065] In the formula: R is the real-time resistance of the core-sheath structure strain sensing fiber;

[0066] R0 is the initial resistance of the core-sheath structure strain sensing fiber;

[0067] ΔR represents the relative change in resistance of the strain-sensing fiber in the core-sheath structure after stretching.

[0068] (4) Test method for fiber sensitivity GF at room temperature: The resistance change of the core-sheath strain sensing fiber after uniaxial stretching is recorded using a source table, and the fiber sensitivity is obtained by further differentiating the resistance change.

[0069]

[0070] In the formula: R0 is the initial resistance of the core-sheath structure strain sensing fiber;

[0071] ΔR represents the relative change in resistance of the strain-sensing fiber in the core-sheath structure after stretching.

[0072] ε represents the tensile strain of the core-sheath structure strain sensing fiber.

[0073] Example 1

[0074] The preparation method of the core-sheath structure strain sensing fiber is as follows:

[0075] (1) Weigh the high elastic polymer polystyrene-polyisoprene-polystyrene, add it to tetrahydrofuran solvent, and stir magnetically for 3 hours at room temperature to obtain a colorless and transparent solution, which is used as the core layer spinning solution. The mass percentage concentration of the high elastic polymer polystyrene-polyisoprene-polystyrene in the core layer spinning solution is 30wt%.

[0076] 0.04 g of multi-walled carbon nanotubes were weighed and added to 5 ml of tetrahydrofuran solvent. After ultrasonic dispersion for 30 minutes using a cell disruptor, 16 wt% of the high-elasticity polymer polystyrene-polyisoprene-polystyrene was added. After magnetic stirring at room temperature for 3 hours, a sheath spinning solution was obtained, in which multi-walled carbon nanotubes accounted for 4 wt% of the high-elasticity polymer polystyrene-polyisoprene-polystyrene.

[0077] (2) Transfer the sheath spinning solution and the core spinning solution into syringes respectively, and perform degassing treatment by ultrasonic treatment in a water bath for 30 minutes. Use a 14G / 18G coaxial needle as the wet spinning needle, and the core spinning solution is propelled at a speed of 15 mL·h. -1 The propulsion speed of the sheath spinning solution is 9 mL·h -1 Anhydrous ethanol solution was used as the coagulation bath; the collecting roller speed was 2 r / min, and wet spinning was performed. In the coagulation bath, the spinning solution solvent diffused bidirectionally with the coagulation bath, and the core-sheath fibers solidified and formed. After drying, coaxial fibers with a core-sheath structure were obtained.

[0078] (3) Prepare 5 wt% silver trifluoroacetate / ethanol solution and 20 wt% hydrazine hydrate / ethanol solution respectively. Immerse a core-sheath fiber of a fixed length of 20 cm in the silver trifluoroacetate / ethanol solution for 1 hour while mixing the solution on a shaker. Remove the core-sheath fiber, dry it, and then immerse it again in the hydrazine hydrate / ethanol solution for reduction treatment. After the core-sheath fiber is reduced for 30 min, it is removed, washed twice with deionized water, and placed in a vacuum oven to dry under vacuum at 60℃ for 1 hour. Repeat the immersion, reduction, and drying treatment three times to obtain the final core-sheath structure strain sensing fiber.

[0079] The core-sheath structure strain-sensing fibers exhibit significant morphological differences, with the surface sheath layer displaying a network-like porous structure and loaded with a large number of silver nanoparticles (e.g., silver nanoparticles with an average particle size of 120 nm). Figure 1 As shown, the core layer has a solid structure and the cross-section of the strain-sensing fiber in the entire core-sheath structure is oval with a cross-sectional area of ​​0.554 mm. 2 (like Figure 2 (As shown). The sensing range, fiber tensile stress, and sensitivity of the core-sheath structure strain sensing fiber are 426%, 0.83 MPa, and 257268, respectively. Figure 3 As shown in (a) and (b), tensile tests were conducted on the core-sheath structure strain-sensing fiber at small strain levels of 1%, 5%, and 10%, respectively. The results show that the core-sheath structure strain-sensing fiber has good monitoring capability for small strains (e.g., ...). Figure 4 As shown). In large strain cyclic testing, the core-sheath structure strain sensing fiber exhibits excellent cyclic stability and resistance change differentiation (e.g. Figure 5 (As shown).

[0080] The above results demonstrate that the core-sheath structured strain sensing fiber possesses high sensitivity and an ultra-wide strain monitoring range. Furthermore, at 1% strain and a tensile speed of 100 mm / min, the core-sheath structured strain sensing fiber exhibits excellent rapid deformation response capability, with a response time of only 45 ms and a recovery time of 128 ms (e.g., ...). Figure 6 (As shown). Furthermore, core-sheath structure strain-sensing fibers are woven into fabrics for monitoring human body surface deformation, achieving stable and clear motion monitoring (e.g., Figure 7 and 8 (As shown).

[0081] Example 2

[0082] The preparation method of the core-sheath structure strain sensing fiber is as follows:

[0083] (1) Weigh the high elastic polymer polystyrene-polyisoprene-polystyrene, add it to tetrahydrofuran solvent, and stir magnetically for 3 hours at room temperature to obtain a colorless and transparent solution, which is used as the core layer spinning solution. The mass percentage concentration of the high elastic polymer polystyrene-polyisoprene-polystyrene in the core layer spinning solution is 30wt%.

[0084] 0.04 g of multi-walled carbon nanotubes were weighed and added to 5 ml of tetrahydrofuran solvent. After ultrasonic dispersion for 30 minutes using a cell disruptor, 16% (by mass) of the high-elasticity polymer polystyrene-polyisoprene-polystyrene was added. After magnetic stirring at room temperature for 3 hours, a sheath spinning solution was obtained, in which multi-walled carbon nanotubes accounted for 4 wt% of the high-elasticity polymer polystyrene-polyisoprene-polystyrene.

[0085] (2) Transfer the sheath spinning solution and the core spinning solution into syringes respectively, and perform degassing treatment by ultrasonic treatment in a water bath for 30 minutes. Use a 14G / 18G coaxial needle as the wet spinning needle, and the core spinning solution is pushed at a speed of 15 mL·h. -1 The propulsion speed of the sheath spinning solution is 9 mL·h -1 Anhydrous ethanol solution was used as the coagulation bath; the collecting roller speed was 2 r / min, and wet spinning was performed. In the coagulation bath, the spinning solution solvent diffused bidirectionally with the coagulation bath, and the core-sheath fibers solidified and formed. After drying, core-sheath fibers were obtained.

[0086] (3) Prepare silver ammonia solution and ascorbic acid solution with a concentration of 5 wt% respectively. Immerse the core-sheath fiber with a fixed length of 20 cm in the silver ammonia solution for 1 hour while mixing the solution with a shaker. Take out the core-sheath fiber, dry it, and then immerse it in the ascorbic acid solution for reduction treatment. After the core-sheath fiber is reduced for 30 min, take it out, wash the core-sheath fiber twice with deionized water, and place it in a vacuum oven to dry it at 60℃ for 1 hour. Repeat the immersion, reduction, and drying treatment 3 times to obtain the final core-sheath structure strain sensing fiber.

[0087] The core-sheath structure strain sensing fiber has an oval cross-section with a cross-sectional area of ​​0.6 mm. 2 Furthermore, the surface sheath layer exhibits a porous network structure and is loaded with a large number of silver nanoparticles (average particle size of 130 nm). The sensing range, fiber tensile stress, and sensitivity of the core-sheath structure strain-sensing fiber are 415%, 0.93 MPa, and 539382, respectively. Figure 9 As shown in (a) and (b), cyclic tensile tests (10% strain, 50% strain, 100% strain) were conducted on the core-sheath strain-sensing fiber at a test speed of 20 mm / min. The core-sheath strain-sensing fiber exhibited stable and regular electrical responses, and the differences in the fiber's electrical response at different strains were significant (e.g., ...). Figure 10 As shown in the figure, this proves that the fiber has excellent sensitivity and sensing stability. The above results prove that the sensing fiber has high sensitivity, wide strain monitoring range and cycle stability. At the same time, it shows that the combination of silver ammonia solution and ascorbic acid in the scheme can also achieve a large number of in-situ fixation of silver nanoparticle layers.

[0088] A core-sheath structure strain-sensing fiber was seamlessly attached to the surface of a 3D-printed cylindrical pneumatic actuator using an elastic photocurable resin. After the resin cured, the cylindrical pneumatic actuator was inflated using a syringe at an injection rate of 20 ml / min. As the volume of gas injected into the actuator increased, the actuator expanded, causing an increase in the fiber resistance on the actuator surface. Figure 11 The paper demonstrates the change in fiber resistance of the core sheath structure strain sensor caused by the volume expansion of the pneumatic actuator, thus achieving stable monitoring of actuator deformation.

[0089] Example 3

[0090] The preparation method of the core-sheath structure strain sensing fiber is as follows:

[0091] (1) Weigh the high elastic polymer polystyrene-polyisoprene-polystyrene, add it to tetrahydrofuran solvent, and stir magnetically for 3 hours at room temperature to obtain a colorless and transparent solution, which is used as the core layer spinning solution. The mass percentage concentration of the high elastic polymer polystyrene-polyisoprene-polystyrene in the core layer spinning solution is 30wt%.

[0092] 0.04 g of multi-walled carbon nanotubes were weighed and added to 5 ml of tetrahydrofuran solvent. After ultrasonic dispersion for 30 minutes using a cell disruptor, 16 wt% of the highly elastic polymer polystyrene-polyisoprene-polystyrene was added. After magnetic stirring at room temperature for 3 hours, a sheath spinning solution was obtained, in which multi-walled carbon nanotubes accounted for 4 wt% of the highly elastic polymer polystyrene-polyisoprene-polystyrene.

[0093] (2) Transfer the sheath spinning solution and the core spinning solution into syringes respectively, and perform degassing treatment by ultrasonic treatment in a water bath for 30 minutes. Use a 14G / 18G coaxial needle as the wet spinning needle, and the core spinning solution is propelled at a speed of 15 mL·h. -1 The propulsion speed of the sheath spinning solution is 9 mL·h -1 Anhydrous ethanol solution was used as the coagulation bath; the collecting roller speed was 2 r / min, and wet spinning was performed. In the coagulation bath, the spinning solution solvent diffused bidirectionally with the coagulation bath, and the core-sheath fibers solidified and formed. After drying, core-sheath fibers were obtained.

[0094] (3) Prepare a 5 wt% silver trifluoroacetate solution and a 5 wt% glucose solution respectively. Immerse a core-sheath fiber of a fixed length of 20 cm in the silver trifluoroacetate solution for 1 hour while mixing the solution using a shaker. Remove the core-sheath fiber, dry it, and then immerse it in the glucose solution again for reduction treatment. After the core-sheath fiber is reduced for 30 min, remove it, wash the core-sheath fiber twice with deionized water, and place it in a vacuum oven to dry it at 60℃ for 1 hour. Repeat the immersion, reduction, and drying treatment three times to obtain the final core-sheath structure strain sensing fiber.

[0095] The core-sheath structure strain-sensing fiber has a porous network-like surface sheath layer, with a large number of silver nanoparticles (average particle size 125 nm) loaded on the surface, and the fiber cross-section is oval with a cross-sectional area of ​​0.65 mm. 2 The sensing range, fiber tensile stress, and sensitivity of the core-sheath structure strain-sensing fiber are 449%, 0.91 MPa, and 1677800, respectively. Figure 12As shown in (a) and (b), cyclic tensile tests (10%, 50%, and 100% strain) were conducted on the core-sheath strain-sensing fiber at a test speed of 20 mm / min. The fiber exhibited stable and regular electrical responses, and the differences in electrical responses at different strains were significant, demonstrating excellent sensitivity and sensing stability (e.g., ...). Figure 13 (As shown in the figure). The above results demonstrate that the sensing fiber has high sensitivity and a wide strain monitoring range, and also show that the combination design of silver trifluoroacetate and glucose solution can also achieve large-scale in-situ fixation of silver nanoparticle layers.

[0096] Comparative Example 1

[0097] The preparation method of the core-sheath structure strain sensing fiber is as follows:

[0098] (1) Weigh the high elastic polymer polystyrene-polyisoprene-polystyrene, add it to tetrahydrofuran solvent, and stir magnetically for 3 hours at room temperature to obtain a colorless and transparent solution, which is used as the core layer spinning solution. The mass percentage concentration of the high elastic polymer polystyrene-polyisoprene-polystyrene in the core layer spinning solution is 30wt%.

[0099] 0.04 g of multi-walled carbon nanotubes were weighed and added to 5 ml of tetrahydrofuran solvent. After ultrasonic dispersion for 30 minutes using a cell disruptor, 16% (by mass) of the high-elasticity polymer polystyrene-polyisoprene-polystyrene was added. After magnetic stirring at room temperature for 3 hours, a sheath spinning solution was obtained, in which multi-walled carbon nanotubes accounted for 4 wt% of the high-elasticity polymer polystyrene-polyisoprene-polystyrene.

[0100] (2) Transfer the sheath spinning solution and the core spinning solution into syringes respectively, and perform degassing treatment by ultrasonic treatment in a water bath for 30 minutes. Use a 14G / 18G coaxial needle as the wet spinning needle, and the core spinning solution is propelled at a speed of 15 mL·h. -1 The propulsion speed of the sheath spinning solution is 9 mL·h -1 Anhydrous ethanol solution was used as the coagulation bath; the collecting roller speed was 2 r / min, and wet spinning was performed. In the coagulation bath, the spinning solution solvent diffused bidirectionally with the coagulation bath, causing the core-sheath fibers to solidify and form. After drying, core-sheath coaxial fibers were obtained. The core-sheath coaxial fibers have a distinct porous network-like surface sheath layer (such as…). Figure 14 (As shown) and an oval solid insulating core with a cross-sectional area of ​​0.5 mm. 2 (like Figure 15 (As shown). Tensile electromechanical properties of the core-sheath coaxial fiber were tested. The sensing range, fiber tensile stress, and sensitivity of the core-sheath coaxial fiber were 1117%, 3 MPa, and 1092, respectively.

[0101] The difference between Comparative Example 1 and Example 1 is that no metal salt solution (silver salt solution) was used to impregnate and reduce the coaxial wet-spun fibers. The comparative results show that the core-sheath structure strain-sensing fiber has a sensitivity three orders of magnitude higher than the core-sheath coaxial fiber, exhibiting ultra-high sensitivity and a wider strain monitoring range. This highlights the important role of in-situ fixation of the silver nanoparticle layer in the sensing layer in synergistically enhancing the sensing layer (e.g., ...). Figure 16 (As shown).

[0102] Comparative Example 2

[0103] The preparation method of the core-sheath structure strain sensing fiber is as follows:

[0104] (1) Weigh the high elastic polymer polystyrene-polyisoprene-polystyrene, add it to tetrahydrofuran solvent, and stir magnetically for 3 hours at room temperature to obtain a colorless and transparent solution, which is used as the core layer spinning solution. The mass percentage concentration of the high elastic polymer polystyrene-polyisoprene-polystyrene in the core layer spinning solution is 30wt%.

[0105] For the sheath spinning solution, 4 wt% of the highly elastic polymer polystyrene-polyisoprene-polystyrene multi-walled carbon nanotubes were added to 5 ml of tetrahydrofuran solvent. After ultrasonic dispersion using a cell disruptor for 30 minutes, 16% of the highly elastic polymer polystyrene-polyisoprene-polystyrene was added. After magnetic stirring at room temperature for 1 hour, 20 wt% of the highly elastic polymer silver nanoparticles (average particle size of 120 nm) were added. After magnetic stirring again at room temperature for 2 hours, a uniform conductive filler dispersion was obtained, which was used as the sheath spinning solution.

[0106] (2) Transfer the sheath spinning solution and the core spinning solution into syringes respectively, and degas them by ultrasonic treatment in a water bath for 30 minutes. Use a 14G / 18G coaxial needle as the wet spinning needle, and the core spinning solution is pushed at a speed of 15 mL·h. -1 The propulsion speed of the sheath spinning solution is 9 mL·h -1 Anhydrous ethanol solution was used as the coagulation bath; the collecting roller speed was 2 r / min, and wet spinning was performed. In the coagulation bath, the spinning solution solvent diffused bidirectionally with the coagulation bath, and the core-sheath fibers solidified and formed. After drying, core-sheath coaxial fibers were obtained.

[0107] The obtained fibers were subjected to tensile testing, and their mechanical and sensing properties were as follows: Figure 17 As shown in (a) and (b), the sensing range, fiber tensile stress, and sensitivity of this core-sheath coaxial fiber are 595.8%, 1.2 MPa, and 673.8, respectively.

[0108] The difference between Comparative Example 2 and Examples 1, 2, and 3 lies in the direct addition of micro / nano silver particles and multi-walled carbon nanotubes to the sheath spinning solution, followed by direct wet spinning to construct the conductive sheath. Comparative results show that the core-sheath structure strain-sensing fibers obtained through metal salt impregnation and reduction treatment in these examples achieve ultra-high sensitivity (e.g., ...). Figure 18 (As shown).

[0109] Comparative Example 3

[0110] The preparation method of the core-sheath structure strain sensing fiber is as follows:

[0111] (1) Weigh out the high elasticity polymer thermoplastic polyurethane, add it to N,N dimethylformamide solvent, and stir magnetically for 3 hours at room temperature to obtain a colorless and transparent solution, which is used as the core layer spinning solution. The mass percentage concentration of the high elasticity polymer thermoplastic polyurethane in the core layer spinning solution is 30wt%.

[0112] 0.04 g of multi-walled carbon nanotubes were weighed and added to 5 ml of N,N-dimethylformamide solvent. After ultrasonic dispersion for 30 minutes using a cell disruptor, 16% of a highly elastic thermoplastic polyurethane polymer was added. After magnetic stirring at room temperature for 3 hours, a sheath spinning solution was obtained, in which the solid conductive filler accounted for 4 wt% of the highly elastic thermoplastic polyurethane polymer.

[0113] (2) Transfer the sheath spinning solution and the core spinning solution into syringes respectively, and perform degassing treatment by ultrasonic treatment in a water bath for 30 minutes. Use a 14G / 18G coaxial needle as the wet spinning needle, and the core spinning solution is propelled at a speed of 15 mL·h. -1 The propulsion speed of the sheath spinning solution is 9 mL·h -1 Deionized water solution was used as the coagulation bath; the collecting roller speed was 2 r / min for wet spinning. In the coagulation bath, the spinning solution solvent diffused bidirectionally with the coagulation bath, causing the core-sheath fibers to solidify and form. After drying, core-sheath coaxial fibers were obtained. These coaxial fibers have a circular cross-section with a hollow, porous center and a smooth outer surface, failing to achieve a network-like porous surface structure (e.g., ...). Figure 19 and 20 (As shown).

[0114] The difference between Comparative Example 3 and Examples 1, 2, and 3 is that thermoplastic polyurethane is used as the elastomer matrix for the fiber, and the core-sheath coaxial fibers are obtained through the same spinning process. Comparison revealed significant differences in morphology between the two methods, making it impossible to construct a solid core layer and a porous network-like surface sheath.

Claims

1. A strain-sensing fiber, characterized in that, The fiber comprises a core layer and a sheath layer, wherein the core layer is a highly elastic polymer layer; the sheath layer comprises a highly elastic polymer layer loaded with carbon nanotubes and silver nanoparticles; wherein the core layer has a solid structure; the highly elastic polymer layer loaded with carbon nanotubes in the sheath layer has a network-like porous structure, and the network-like porous structure immobilizes the silver nanoparticles in situ; wherein the highly elastic polymer is a polystyrene block copolymer; the polystyrene block copolymer is one or more of polystyrene-polyisoprene-polystyrene, polystyrene-ethylene-butene-polystyrene, and polystyrene-polybutadiene-polystyrene. The method for preparing strain-sensing fibers includes the following steps: Step (1) Mix the high-elasticity polymer and solvent to obtain the core spinning solution; mix the carbon nanotubes, high-elasticity polymer and solvent to obtain the sheath spinning solution, and perform coaxial wet spinning to obtain coaxial fibers; wherein the high-elasticity polymer is a polystyrene block copolymer; the concentration of the high-elasticity polymer in the core spinning solution in step (1) is 25-50 wt%; the concentration of the high-elasticity polymer in the sheath spinning solution is 1-24 wt%; the carbon nanotubes in the sheath spinning solution in step (1) are 1-10 wt% of the high-elasticity polymer; the coagulation bath used for coaxial wet spinning is anhydrous ethanol solution; wherein the solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, acetone, dichloromethane, chloroform, toluene, chlorobenzene, tetrahydrofuran, and dimethyl sulfoxide; Step (2) Immerse the coaxial fiber in a metal salt solution, dry it, then immerse it in a reducing solution and dry it to obtain strain sensing fiber; wherein the metal salt solution is one or more of silver trifluoroacetate solution, silver ammonia solution, and silver nitrate solution.

2. The strain-sensing fiber according to claim 1, characterized in that, The average particle size of the silver nanoparticles is 100-150 nm.

3. The strain-sensing fiber according to claim 1, characterized in that, In the highly elastic polymer layer loaded with carbon nanotubes, the carbon nanotubes account for 1-10 wt% of the highly elastic polymer.

4. A method for preparing the strain-sensing fiber according to any one of claims 1-3, characterized in that, Includes the following steps: Step (1) involves mixing a highly elastic polymer and a solvent to obtain a core spinning solution; mixing carbon nanotubes, a highly elastic polymer, and a solvent to obtain a sheath spinning solution; and performing coaxial wet spinning to obtain coaxial fibers; wherein the highly elastic polymer is a polystyrene block copolymer; the concentration of the highly elastic polymer in the core spinning solution in step (1) is 25-50 wt%; and the concentration of the highly elastic polymer in the sheath spinning solution is 1-24 wt%. wt%; the carbon nanotubes in the sheath spinning solution in step (1) are 1-10 wt% of a highly elastic polymer; the coagulation bath used in coaxial wet spinning is anhydrous ethanol solution; the solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, acetone, dichloromethane, chloroform, toluene, chlorobenzene, tetrahydrofuran, and dimethyl sulfoxide; the polystyrene block copolymer is one or more of polystyrene-polyisoprene-polystyrene, polystyrene-ethylene-butene-polystyrene, and polystyrene-polybutadiene-polystyrene. Step (2) Immerse the coaxial fiber in a metal salt solution, dry it, then immerse it in a reducing solution and dry it to obtain strain sensing fiber; wherein the metal salt solution is one or more of silver trifluoroacetate solution, silver ammonia solution, and silver nitrate solution.

5. The preparation method according to claim 4, characterized in that, The coaxial wet spinning process parameters in step (1) are as follows: the coaxial needle size is 14G-18G, and the core spinning solution propulsion speed is 1-150 mL·h. -1 The propulsion speed of the sheath spinning solution is 1-80 mL·h -1 The collecting roller speed is 1-20 r / min.

6. The preparation method according to claim 4, characterized in that, The reducing solution in step (2) is one or more of hydrazine hydrate solution, ascorbic acid solution, and glucose solution; The concentration of the metal salt solution in step (2) is 1-20 wt%; The concentration of the reducing solution is 1-30 wt%.

7. The preparation method according to claim 4, characterized in that, In step (2), the immersion time in the metal salt solution is 0.1-3 hours; the immersion time in the reducing solution is 0.1-3 hours. Step (2) is repeated 1-5 times.

8. A fabric, characterized in that, The fabric contains any one of the strain-sensing fibers according to claims 1-3.

9. The application of the strain-sensing fiber of any one of claims 1-3 and the fabric of claim 8 in the fields of human motion monitoring, smart wearable devices, biomedical diagnosis, and soft robotics.

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