A yarn-like sensor with reversible color change and auxetic effect and a preparation method thereof

Abstract

This invention discloses a yarn-shaped sensor with reversible color change and tensile effect, and its preparation method, relating to the field of flexible sensors. The invention strengthens the constraint of the parallel double-core layer by forming a continuous figure-eight winding loop between three outer yarns and two parallel elastic spandex core filaments, ensuring high structural stability during weaving and use. During stretching, this configuration forces the two elastic spandex core filaments to push laterally apart through a cross-winding mechanism, inducing a more significant negative Poisson's ratio effect. The composite weaving process using synchronous feeding of the double-core filaments enhances the overall structural integrity and resilience of the yarn. Simultaneously, the introduction of conductive outer yarn into the outer layer of the yarn-shaped sensor reduces sensing hysteresis, improves long-term structural durability, and enhances the strain sensing sensitivity of the yarn-shaped sensor.

Description

Technical Field

[0001] This invention belongs to the field of flexible sensors, and specifically relates to a yarn-shaped sensor with both reversible color change and stretching effect, and its preparation method. Background Technology

[0002] Currently, the preparation of fiber or yarn-like sensors, i.e., yarn-like sensing materials, mainly employs various processes such as impregnation, coating, blending, printing, 3D printing, spinning, and twisting. By combining conductive materials such as conductive polymers, metal nanoparticles, metal nanowires, and carbon materials (carbon nanotubes, graphene, carbon black, carbon fibers) with an elastic matrix, a sensing structure with variable resistance when stretched or bent is constructed. Based on the spatial arrangement of the conductive phase and the matrix, common yarn-like sensor configurations are mainly divided into three categories: embedded structures, core-shell structures, and wound structures. Among them, embedded structures achieve functionality by embedding conductive particles inside a linear elastic substrate; however, in actual use, the conductive particles are easily detached due to mechanical friction or repeated cleaning, leading not only to sensor performance degradation or even failure but also potential safety risks to humans. Core-shell structures are typically constructed using complex spinning or elastic yarn surface coating processes. For spinning, it is necessary to customize and replace a dedicated coaxial spinning nozzle. The fabrication of concentrically expanding core-shell yarns involves a complex process. For surface coating, the interface between the conductive layer and the elastic matrix yarn is prone to peeling under cyclic stress, causing structural irregularity damage and severely affecting the sensor's sensitivity, stability, and service life. In contrast, wound yarn strain sensors spatially integrate the conductive component with the elastic fiber component through twisting and winding. This not only simplifies the fabrication process and enhances structural mechanical robustness, but also, due to its unique stress transmission mechanism, exhibits superior conductivity retention and interface stability under repeated cyclic deformation. Therefore, it is considered one of the feasible paths to achieve high-performance, long-life yarn-based strain sensors. From the perspective of tensile deformation effects, wound yarn strain sensors can be further divided into non-tensile and tensile types. Among them, the tensile structure shows significant advantages in applications requiring high responsiveness and a wide strain range, making its research value and application potential more prominent.

[0003] Braided yarn technology, due to its unique advantages in yarn structure redesign and multifunctional composite integration, has become one of the important pathways for developing high-performance strain-sensing yarns. This technology can achieve precise coating and stable interfacial bonding of multilayer heterogeneous materials, and its mature process and strong adaptability are conducive to large-scale production. (See the reference "Shape-adaptable and wearable strain sensor based on braided auxetic yarns for monitoring large human motions. Applied Materials Today, 2023, 35:..."). In 101996, a 16-spindle braiding machine was used to prepare four specifications of tensile yarns: BAY1 (one spandex and one silver-plated filament), BAY2 (one spandex and two silver-plated filaments), BAY3 (four spandex and two silver-plated filaments), and BAY4 (two spandex and four silver-plated filaments). The structure can be summarized as a composite of N elastic core layers and n sheath layers (1≤N≤4, 1≤n≤4). By adjusting the ratio of the core layer to the outer sheath, yarn-shaped sensors with different tensile behaviors can be obtained. To enhance the tensile effect (i.e., the negative Poisson's ratio effect), multiple elastic spandex core filaments were fed together, effectively acting as a single core filament with a larger diameter. Under axial tension, the multiple spandex core filaments migrated outward synchronously under the pressure of the outer silver-plated filaments, while the outer sheath gradually straightened from a spiral shape. However, in this structure, the migration paths of all core filaments were exactly the same, and it was difficult for multiple core filaments to remain completely parallel and straight throughout. Especially under low strain conditions, the core diameter becomes significantly thinner, weakening the tensile expansion effect. Patent ZL 20241072478.2, "A Tense Braided Yarn Sensor and Its Preparation Method," proposes interlocking the elastic outer yarn with the rigid outer yarn to prevent the rigid outer yarn from sliding along the elastic core yarn, thereby improving the stability and sensitivity of the sensor structure. However, because this yarn-shaped sensor only has one central tube, it has a clear structural limitation: it can only achieve close feeding of single or multiple parallel elastic spandex core yarns, making it difficult to control the synchronous introduction of multiple core yarns at a preset spacing. This structural limitation results in a single migration path for the core yarns during stretching, making it difficult to actively form effective lateral expansion; therefore, the tensile expansion effect it can achieve is relatively limited.Furthermore, based on hollow spindle wrapping spinning technology, stretched yarn sensors can also be fabricated by specifically modifying the yarn configuration or key components. For example, the hollow spindle double-wrapped stretched yarn structure reported in the literature "Full-fiber auxetic-interlaced yarn sensor for sign-language translation glove assisted by artificial neural network. Nano-MicroLetters, 2022, 14: 139." uses spandex elastic yarn as the core, and the outside is uniformly wrapped by two counter-wound silver-plated conductive filaments. When stretched, the visual diameter increases, and the change in the contact area at the interlacing points of the conductive yarns causes a change in resistance, thereby realizing strain sensing. Yarn structures using a single spandex core filament have relatively limited structural stability during long-term service and cyclic stretching. This lack of stability leads to significant and uncontrollable changes in the resistance of the yarn sensor, thus affecting its sensing performance, specifically manifested as decreased sensitivity and signal response hysteresis. Patent ZL 202310103609.0, "A spinning process for a bundled biaxial core-sheath structure tension yarn," uses two single-covered yarns (covering directions opposite) as the double core layer, and then spirally winds a high-elasticity yarn around them to enhance the overall structural integrity and robustness of the tension effect. In this yarn structure, the two single-covered yarns are held together by only one externally wound high-elasticity yarn, which often results in insufficient constraint. This easily leads to the two single-covered yarn core layers becoming twisted together, making it difficult to maintain a completely straight state, thus making it difficult for the yarn to produce a significant negative Poisson's ratio effect during stretching. Summary of the Invention

[0004] In view of the problems in related technologies, this invention proposes a yarn-shaped sensor with both reversible color change and stretching effect and a preparation method thereof, so as to overcome the above-mentioned technical problems existing in the existing related technologies.

[0005] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0006] The present invention is a yarn-shaped sensor (yarn-shaped sensor, i.e. yarn-shaped sensing material) that has both reversible color change and tensile effect, the yarn-shaped sensor comprising a core layer and a braided sheath layer;

[0007] The core layer consists of two elastic spandex core filaments as the structural skeleton, which are arranged in parallel. The braided sheath layer is formed by binding the two elastic spandex core filaments together with an outer sheath yarn through a braided structure. The outer sheath yarn includes two conductive outer sheath yarns and one thermochromic outer sheath yarn.

[0008] It should be noted that, since the yarn-shaped sensor of the present invention has a flat strip structure, its stretching effect is dependent on the viewing angle, that is, it is only visible from a specific direction.

[0009] The yarn-shaped sensor possesses excellent strain sensing performance, reversible electrochromic effect, and view-selective dilatation effect.

[0010] Preferably, by adjusting the relative spatial positions of the two conductive outer yarns and the thermochromic outer yarn, two typical yarn configurations are formed, namely configuration I and configuration II.

[0011] Configuration I consists of two conductive outer yarns wound around the surfaces of the two elastic spandex core yarns in opposite spiral paths, arranged in a symmetrical cross pattern on the surface of the yarn-shaped sensor. The thermochromic outer yarn is wrapped in the same spiral direction as one of the conductive outer yarns. Configuration II consists of two conductive outer yarns and a thermochromic outer yarn wound around the surfaces of the two elastic core yarns in the same spiral direction.

[0012] Preferably, the elastic spandex core yarn is coarse denier spandex yarn with a fineness of 840D-2500D; more preferably, the coarse denier spandex yarn has a fineness of 1120D, 1680D, or 2500D; the conductive outer covering yarn is silver-plated filament with a fineness of 40D-400D; more preferably, the silver-plated filament has a fineness of 40D, 70D, 140D, 200D, 280D, or 400D; the thermochromic outer covering yarn is a coated thermosensitive color-changing yarn; more preferably, the thermochromic outer covering yarn has a fineness of 150D, 150D / 2, 150D / 3, or 250D / 2, and the color-changing response temperature threshold is 30℃-65℃.

[0013] Preferably, the weaving structure is an "8"-shaped winding loop structure, so that all the outer yarns together form a braided sheath layer that binds the two elastic spandex core yarns.

[0014] Preferably, the yarn-shaped sensor has the characteristic of undergoing reversible color change under voltage excitation, and this characteristic is related to the working length of the yarn-shaped sensor. Therefore, by applying a predetermined voltage to both ends of the yarn-shaped sensor, a reversible color change can be generated between the energized and de-energized states. To achieve electrochromic response, a voltage range of 0.5-3.5 V / cm (i.e., a voltage range of 0.5-3.5 V per centimeter) can be applied to both ends of the yarn-shaped sensor. The specific operation steps are as follows: First, conductive copper sheets are attached to both ends of the yarn-shaped sensor as electrodes. Then, the two clamps of the DC regulated power supply are used to clamp the copper sheets at both ends of the yarn-shaped sensor to connect the circuit. By adjusting the output voltage of the DC regulated power supply, a corresponding voltage is applied to the yarn-shaped sensor, thereby exciting the yarn-shaped sensor to produce a corresponding dynamic color-changing effect.

[0015] A method for fabricating a yarn-shaped sensor that combines reversible color change and tensile effect, using a braiding machine, includes the following steps:

[0016] S1. By applying a predetermined multiple of pre-stretch through the active feed roller, the two elastic spandex core yarns are unwound from the bobbin in a taut state; then, they are respectively guided by the yarn guide hooks to the hollow spindle one and hollow spindle two corresponding to the center positions of the two meshing first and second corner wheels on the braiding machine chassis, and are drawn out from the upper ends of hollow spindle one and hollow spindle two respectively; the active feed roller is used to control the stretching and conveying of the elastic spandex core yarns;

[0017] S2. Two yarn tubes with conductive outer sheath yarn and one yarn tube with thermochromic outer sheath yarn are inserted into the first and second corner wheels according to a specific pattern. During the weaving process, the outer sheath yarn moves clockwise and counterclockwise around the first and second elastic spandex core yarns in a specific path, passing over one elastic spandex core yarn in turn and then crossing under the other elastic spandex core yarn to form a continuous figure-eight winding cycle, which together constitutes the braided sheath layer.

[0018] S3. The first and second elastic spandex core yarns converge with the braided sheath at the bundling ring to form a yarn-shaped sensor. This sensor is then evenly wound onto a bobbin to complete the fabrication process.

[0019] Preferably, in step S1, the elastic spandex core yarn one and elastic spandex core yarn two are pre-stretched by actively feeding rollers, and the pre-stretch ratio is controlled within the range of 1.25-3.50; nine spindles for inserting outer covering yarn are evenly distributed around the two meshing first and second corner rollers along a reverse figure-eight path, and are numbered sequentially as spindle positions 1 to 9.

[0020] Preferably, the installation of the outer wrapping yarn in S2 follows the following rules: To ensure the stability of the yarn sensor structure and the basic consistency of the feeding tension of each outer wrapping yarn, the three outer wrapping yarns are distributed on two meshing first and second corner pulleys to avoid uneven overall arrangement caused by the outer wrapping yarns being concentrated on a single corner pulley. The corresponding spindle configuration scheme is adopted according to the target yarn formation configuration: For yarn formation configuration I, two conductive outer wrapping yarns and one thermochromic outer wrapping yarn can be configured at spindle positions 3, 6, and 9 respectively; for yarn formation configuration II, two conductive outer wrapping yarns and one thermochromic outer wrapping yarn can be configured at spindle positions 3, 9, and 8 respectively.

[0021] Preferably, in step S2, by adjusting the gear transmission ratio of the weaving machine, the number of teeth on all gears is even, ranging from 20 to 46.

[0022] The present invention has the following beneficial effects:

[0023] 1. In this invention, three outer yarns and two parallel elastic spandex core filaments form a continuous figure-eight winding loop, thereby applying a stronger binding effect to the core layer. During the stretching process, the two elastic spandex core filaments are forced to be pushed laterally apart by the cross-winding mechanism. In comparison, this invention relates to a method that can effectively induce lateral displacement of the core yarn, thereby exhibiting a more significant negative Poisson's ratio effect. The processing method is simple, practical, and mass-producible; it only requires adding core components such as positive feed rollers to a braiding machine to produce a yarn-like sensor with both reversible color change and angle-selective stretching effect in one step. The sensor is the sensing material. This yarn-like sensor possesses excellent strain sensing performance, accurately responding to a wide range of human movements, from subtle physiological signals to large-scale joint movements. Under certain external voltage stimulation, the yarn-like sensor in this invention exhibits rapid and reversible visual color changes, thus possessing dynamic response capabilities. Furthermore, this yarn-like sensor exhibits a significant angle-selective stretching effect. Viewed from the side, under axial load, the two elastic spandex core yarns bend into a spiral shape under the constraint of the outer yarn, while the outer yarn gradually straightens from a spiral state, exhibiting an overall stretching behavior of expanding the apparent diameter of the yarn. This phenomenon is not observed when viewed from the front.

[0024] 2. The presence of two core filaments in this invention further enhances the overall resilience of the yarn-shaped sensor, reduces sensing hysteresis, and increases elastic durability. After 50 cycles of cyclic loading under relatively large tensile strains (such as 50%, 150%, and 200%), it still exhibits robust mechanical stability and fatigue resistance. By applying precisely controlled external voltages to both ends of the yarn-shaped sensor, reversible color changes can be achieved, giving it dynamic visual feedback capabilities. The product of this invention has low manufacturing costs and reliable and stable performance, which is conducive to its widespread application.

[0025] 3. The parallel dual-core yarn structure used in this invention strengthens the constraint and synergistic effect on the core yarns through an "8"-shaped winding mechanism, significantly improving the overall stability of the structure. Therefore, after repeated stretching, its resistive behavior is more stable and reliable, thereby effectively improving the accuracy and immediacy of the sensing. That is, the composite weaving process of synchronously feeding dual-core yarns enhances the overall structural integrity and resilience of the yarn sensor. At the same time, the introduction of silver-plated filaments into the outer layer of the yarn sensor can reduce sensing hysteresis, improve the structural durability for long-term service, and enhance the strain sensing sensitivity of the yarn sensor.

[0026] 4. In this invention, three outer yarns are used to spirally intertwine two parallel elastic spandex core filaments. This structure significantly enhances the wrapping and constraint of the core filaments, ensuring that the yarn-shaped sensor maintains a highly stable shape during deformation. The high stability of the yarn-shaped sensor structure effectively guarantees the high robustness of the negative Poisson's ratio effect of the final yarn-shaped sensor. By introducing thermochromic outer yarns into the yarn-shaped sensor, the controllable color-changing function of the yarn-shaped sensor is realized, significantly enhancing its application potential in fields such as visual sensing, human-computer interaction, and adaptive camouflage.

[0027] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 The images shown are of the yarn-shaped sensor of configuration I of the present invention, and are the surface morphology of the yarn-shaped sensor observed using a USB microscope; wherein (a) is an image of embodiment 1; and (b) is an image of embodiment 2.

[0030] Figure 2 The images shown are of the yarn-shaped sensor of configuration II of the present invention, and are the surface morphology of the yarn-shaped sensor observed using a USB microscope; wherein (a) is an image of Example 3; and (b) is an image of Example 4.

[0031] Figure 3 This is a schematic diagram of the tensile effect of the yarn-shaped sensor (configuration I) prepared in Embodiment 1 of the present invention: a reduction in apparent diameter induced by axial stretching (front view); wherein, d 0、 d 1. d 2 represents the outer contour diameter of the yarn-shaped sensor prepared in Example 1 under the following conditions: initial unstretched state (i.e., 0% tensile strain), 25% tensile strain, and 50% tensile strain (viewing angle from the front view).

[0032] Figure 4 This is a schematic diagram illustrating the tensile effect of the yarn-shaped sensor (configuration I) prepared in Embodiment 1 of the present invention: an increase in apparent diameter induced by axial stretching (side view). d 0、 d1 represents the outer contour diameter of the yarn-shaped sensor prepared in Example 1 in the initial unstretched state (i.e., 0% tensile strain) and at 50% tensile strain (side view observation angle).

[0033] Figure 5 This is a schematic diagram of the lateral view of the expansion effect of the yarn-shaped sensor (configuration I) prepared in Embodiment 2 of the present invention: an increase in apparent diameter induced by axial stretching; wherein, d 0、 d 1 represents the outer contour diameter of the yarn-shaped sensor prepared in Example 2 in the initial unstretched state (i.e., 0% tensile strain) and at 150% tensile strain (side view observation angle).

[0034] Figure 6 This is a schematic diagram of the lateral view of the expansion effect of the yarn-shaped sensor (configuration II) prepared in Example 3 of the present invention: an increase in apparent diameter induced by axial stretching; wherein, d 0、 d 1 represents the outer contour diameter of the yarn-shaped sensor prepared in Example 3 in the initial unstretched state (i.e., 0% tensile strain) and at 50% tensile strain (side view observation angle).

[0035] Figure 7 This is a schematic diagram of the lateral view of the expansion effect of the yarn-shaped sensor (configuration II) prepared in Example 4 of the present invention: an increase in apparent diameter induced by axial stretching; wherein, d 0、 d 1 represents the outer contour diameter of the yarn-shaped sensor prepared in Example 4 in the initial unstretched state (i.e., 0% tensile strain) and at 200% tensile strain (side view observation angle).

[0036] Figure 8 This is a schematic diagram of the performance curves of the yarn-shaped sensor prepared in Example 1 of the present invention; in the figure, (a) is the tensile mechanical curve of 50 cycles at a constant strain of 50%, and (b) is the corresponding tensile fracture mechanical curve.

[0037] Figure 9 This is a schematic diagram of the performance curves of the yarn-shaped sensor prepared in Example 2 of the present invention; in the figure, (a) is the tensile mechanical curve of 50 cycles at a constant strain of 150%, and (b) is the corresponding tensile fracture mechanical curve.

[0038] Figure 10 This is a schematic diagram of the performance curves of the yarn-shaped sensor prepared in Example 3 of the present invention; in the figure, (a) is the tensile mechanical curve of 50 cycles at a constant strain of 50%, and (b) is the corresponding tensile fracture mechanical curve.

[0039] Figure 11This is a schematic diagram of the performance curves of the yarn-shaped sensor prepared in Example 4 of the present invention; in the figure, (a) is the tensile mechanical curve of 50 cycles at a constant strain of 200%, and (b) is the corresponding tensile fracture mechanical curve.

[0040] Figure 12 This is a schematic diagram of the reversible color-changing response behavior of the 4 cm yarn-shaped sensor based on Embodiment 1 of the present invention under an applied voltage of 4 V;

[0041] Figure 13 This is a schematic diagram of the reversible color-changing response behavior of the 4 cm yarn-shaped sensor based on Embodiment 2 of the present invention under an applied voltage of 4 V;

[0042] Figure 14 This is a schematic diagram of the reversible color-changing response behavior of the 4 cm yarn-shaped sensor based on Embodiment 3 of the present invention under an applied voltage of 4 V;

[0043] Figure 15 This is a schematic diagram of the reversible color-changing response behavior of the 4 cm yarn-shaped sensor based on Embodiment 4 of the present invention under an applied voltage of 4 V;

[0044] Figure 16 This is a schematic diagram of the resistance change of the yarn-shaped sensor in Embodiment 1 of the present invention; in the figure, (a) is the resistance-strain response curve; (b) is the resistance stability after 5 cycles at 50% strain.

[0045] Figure 17 This is a schematic diagram of the resistance change of the yarn-shaped sensor in Embodiment 2 of the present invention; in the figure, (a) is the resistance-strain response curve; (b) is the resistance stability after 5 cycles at 50% strain.

[0046] Figure 18 This is a schematic diagram of the resistance change of the yarn-shaped sensor in Embodiment 3 of the present invention; in the figure, (a) is the resistance-strain response curve; (b) is the resistance stability after 5 cycles at 50% strain.

[0047] Figure 19 This is a schematic diagram of the resistance change of the yarn-shaped sensor in Embodiment 4 of the present invention; in the figure, (a) is the resistance-strain response curve; (b) is the resistance stability after 5 cycles at 50% strain.

[0048] Figure 20 This is a schematic diagram of the structure of the yarn-shaped sensor in Comparative Example 1 of the present invention; in the figure, (a) is a schematic diagram of the structure of the yarn-shaped sensor; (b) is an overall morphology and a partial magnified view of the yarn-shaped sensor after it is formed into a cross braid shape with 150 D high-elastic polyester yarn as the outermost binding yarn; (c) is a schematic diagram of the structure when the two single-wrapped yarns in the core layer are misaligned with 40 D spandex elastic yarn as the outermost binding yarn.

[0049] Figure 21This is a schematic diagram of the active unwinding roller device for unwinding elastic spandex core yarns according to the present invention and its placement method; in the figure, (a) is the active unwinding roller device for unwinding elastic spandex core yarns; (b) is the placement method of two elastic spandex core yarn bobbins on the device;

[0050] Figure 22 This is a schematic diagram of the structure of the present invention based on a reverse figure-eight path with two meshing angular wheels and nine spindles for inserting outer yarn. The numbers 1-9 represent the spindle numbers on the two meshing angular wheels that can be used to insert the outer yarn. Each of the two angular wheels has nine spindles, one of which is shared by both. The insertion of the outer yarn basically follows the insertion rule of 1 insert and 2 empty. The spindle numbering is only set for the convenience of explaining the specific insertion position of the outer yarn in the embodiment. By inserting the outer yarn on spindles with different numbers, different yarn structures can be formed, the most typical of which are configuration I and configuration II.

[0051] Figure 23 This is a schematic diagram of the structure of the yarn-shaped sensor (configuration I) prepared by configuring two conductive outer yarns and one thermochromic outer yarn at spindle positions 3, 6 and 9 respectively.

[0052] Figure 24 This is a schematic diagram of the structure of the yarn-shaped sensor (configuration II) prepared by configuring two conductive outer yarns and one thermochromic outer yarn at spindle positions 3, 9 and 8 respectively.

[0053] Figure 25 This is a schematic diagram of the structure of the invention for low-twist / high-twist knitting of outer yarn based on gear transmission ratio; in the figure, (a) is the low-twist knitting of outer yarn based on gear transmission ratio; (b) is the high-twist knitting of outer yarn based on gear transmission ratio.

[0054] Figure 23 , Figure 24 middle:

[0055] 1. Elastic spandex core yarn one; 2. Elastic spandex core yarn two; 3. Silver-plated filament outer covering yarn one; 4. Silver-plated filament outer covering yarn two; 5. Thermochromic outer covering yarn; 6. Positive feed roller; 7. Braiding machine chassis; 8. First angle roller; 9. Second angle roller; 10. Hollow spindle one; 11. Hollow spindle two; 12. Bundling ring; 13. Yarn sensor; 14. Boll tube. Detailed Implementation

[0056] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0057] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0058] Example 1

[0059] Please see Figure 1 , Figures 21-23 Tables 1 and 2 illustrate a yarn-shaped sensor with both reversible color change and stretching effect. It comprises two parallel elastic spandex core yarns (i.e., elastic spandex core yarn one and elastic spandex core yarn two, the elastic spandex core yarns being coarse denier spandex yarns), two conductive outer covering yarns (i.e., silver-plated filament outer covering yarn one and silver-plated filament outer covering yarn two, i.e., silver-plated filament conductive outer covering yarn; this product uses nylon filament as the base material and is made with a silver-plated surface, wherein the silver plating mass is 17%), and one thermochromic outer covering yarn (i.e., coated thermochromic outer covering yarn, polyester base, specifically a coated thermosensitive color-changing yarn). Specifically, the two conductive outer yarns and the one thermochromic outer yarn are respectively arranged at spindle positions 3, 6, and 9 (where the thermochromic outer yarn corresponds to spindle position 9) to ensure that the two conductive outer yarns are wound around the surface of the two parallel elastic spandex core yarns in a reverse spiral path and are symmetrically distributed on the surface of the yarn-shaped sensor. The thermochromic outer yarn is wrapped in the same direction spiral with one of the conductive outer yarns.

[0060] The yarn-shaped sensor has the characteristic of undergoing reversible color change under voltage excitation, and this change is related to the working length of the yarn-shaped sensor. Therefore, by applying a predetermined voltage to both ends of the yarn-shaped sensor, a reversible color change can be generated between the energized and de-energized states. To achieve electrochromic response, a voltage of 1V / cm (i.e., 1V per centimeter) can be applied to both ends of the yarn-shaped sensor. The specific operating steps are as follows: First, conductive copper sheets are attached to both ends of the yarn-shaped sensor as electrodes. Then, the two clamps of a DC regulated power supply are used to clamp the copper sheets at both ends of the yarn-shaped sensor to connect the circuit. By adjusting the output voltage of the DC regulated power supply, a corresponding voltage is applied to the yarn-shaped sensor, thereby exciting the yarn-shaped sensor to produce a corresponding dynamic color-changing effect.

[0061] In addition, a method for preparing a yarn-shaped sensor that combines reversible color change and stretching effect, using a 90-type 369-spindle braiding machine, includes the following steps:

[0062] S1. By applying a pre-stretch of 1.75 times to the spandex core yarn through the active feed roller, the two elastic spandex core yarns are unwound from the bobbin in a taut state; then, they are respectively guided by the yarn guide hook to the hollow spindle one and hollow spindle two corresponding to the center positions of the two meshing first and second corner wheels on the base of the braiding machine, and are drawn out from the upper ends of hollow spindle one and hollow spindle two respectively; the active feed roller is used to control the stretching and conveying of the elastic spandex core yarns;

[0063] S2. On the first and second corner wheels, two yarn tubes wrapped with conductive outer yarn (i.e., silver-plated filament outer yarn one and silver-plated filament outer yarn two) and one yarn tube wrapped with thermochromic outer yarn are inserted according to a specific pattern (i.e., the two conductive outer yarns and one thermochromic outer yarn are respectively positioned at spindle positions 3, 6, and 9, where the thermochromic outer yarn corresponds to spindle position 9); during the weaving process, the outer yarn moves clockwise and counterclockwise along a specific path around the elastic spandex core yarn one and the elastic spandex core yarn two, passing over one elastic spandex core yarn in turn, and then crossing under the other elastic spandex core yarn to form a continuous figure-eight winding cycle, which together constitutes the braided sheath layer. The wrapping density of the braided sheath layer is controlled by adjusting the gear transmission ratio of the braiding machine. The gear ratio (gear 1: gear 2: gear 3: gear 4) is 20:22:24:46; wherein, the specific pattern and specific path are all for forming the yarn configuration I.

[0064] The installation of the outer wrapping yarn described in S2 follows the following rules: To ensure the stability of the yarn sensor structure and the basic consistency of the feeding tension of each outer wrapping yarn, the three outer wrapping yarns are distributed on two meshing first and second corner pulleys to avoid uneven overall arrangement caused by the outer wrapping yarns being concentrated on a single corner pulley. A corresponding spindle configuration scheme is adopted according to the target yarn configuration: two conductive outer wrapping yarns and one thermochromic outer wrapping yarn can be configured at spindle positions 3, 6, and 9 respectively (where the thermochromic outer wrapping yarn corresponds to spindle position 9) to construct yarn configuration I;

[0065] S3. The first and second elastic spandex core yarns converge with the braided sheath at the bundling ring to form a yarn-shaped sensor. This sensor is then evenly wound onto a bobbin to complete the fabrication process.

[0066] Example 2

[0067] Please see Figure 1 , Figures 21-23Tables 1 and 2 illustrate a yarn-shaped sensor with both reversible color change and stretching effect. It comprises two parallel elastic spandex core yarns (i.e., elastic spandex core yarn one and elastic spandex core yarn two, the elastic spandex core yarns being coarse denier spandex yarns), two conductive outer covering yarns (i.e., silver-plated filament outer covering yarn one and silver-plated filament outer covering yarn two, i.e., silver-plated filament conductive outer covering yarn; this product uses nylon filament as the base material and is made with a silver-plated surface, wherein the silver plating mass is 17%), and one thermochromic outer covering yarn (i.e., coated thermochromic outer covering yarn, polyester base, specifically a coated thermosensitive color-changing yarn). Specifically, the two conductive outer yarns and the one thermochromic outer yarn are respectively arranged at spindle positions 3, 6, and 9 (where the thermochromic outer yarn corresponds to spindle position 9) to ensure that the two conductive outer yarns are wound around the surface of the two parallel elastic spandex core yarns in a reverse spiral path and are symmetrically distributed on the surface of the yarn-shaped sensor. The thermochromic outer yarn is wrapped in the same direction spiral with one of the conductive outer yarns.

[0068] The yarn-shaped sensor has the characteristic of undergoing reversible color change under voltage excitation, and this change is related to the working length of the yarn-shaped sensor. Therefore, by applying a predetermined voltage to both ends of the yarn-shaped sensor, a reversible color change can be generated between the energized and de-energized states. To achieve electrochromic response, a voltage of 1V / cm (i.e., 1V per centimeter) can be applied to both ends of the yarn-shaped sensor. The specific operating steps are as follows: First, conductive copper sheets are attached to both ends of the yarn-shaped sensor as electrodes. Then, the two clamps of a DC regulated power supply are used to clamp the copper sheets at both ends of the yarn-shaped sensor to connect the circuit. By adjusting the output voltage of the DC regulated power supply, a corresponding voltage is applied to the yarn-shaped sensor, thereby exciting the yarn-shaped sensor to produce a corresponding dynamic color-changing effect.

[0069] In addition, a method for preparing a yarn-shaped sensor that combines reversible color change and stretching effect, using a 90-type 369-spindle braiding machine, includes the following steps:

[0070] S1. By applying a pre-stretch of 3.0 times to the spandex core yarn through the active feed roller, the two elastic spandex core yarns are unwound from the bobbin in a taut state; then, they are respectively guided by the yarn guide hook to the hollow spindle one and hollow spindle two corresponding to the center positions of the two meshing first and second corner wheels on the base of the braiding machine, and are drawn out from the upper ends of hollow spindle one and hollow spindle two respectively; the active feed roller is used to control the stretching and conveying of the elastic spandex core yarns;

[0071] S2. On the first and second corner wheels, two yarn tubes wrapped with conductive outer yarn (i.e., silver-plated filament outer yarn one and silver-plated filament outer yarn two) and one yarn tube wrapped with thermochromic outer yarn are inserted according to a specific pattern (i.e., the two conductive outer yarns and one thermochromic outer yarn are respectively positioned at spindle positions 3, 6, and 9, where the thermochromic outer yarn corresponds to spindle position 9); during the weaving process, the outer yarn moves clockwise and counterclockwise along a specific path around the elastic spandex core yarn one and the elastic spandex core yarn two, passing over one elastic spandex core yarn in turn, and then crossing under the other elastic spandex core yarn to form a continuous figure-eight winding cycle, which together constitutes the braided sheath layer. The wrapping density of the braided sheath layer is controlled by adjusting the gear transmission ratio of the braiding machine. The gear ratio (gear 1: gear 2: gear 3: gear 4) is 20:22:46:46; wherein the specific pattern and specific path are for forming the yarn configuration I.

[0072] The installation of the outer wrapping yarn described in S2 follows the following rules: To ensure the stability of the yarn sensor structure and the basic consistency of the feeding tension of each outer wrapping yarn, the three outer wrapping yarns are distributed on two meshing first and second corner pulleys to avoid uneven overall arrangement caused by the outer wrapping yarns being concentrated on a single corner pulley. A corresponding spindle configuration scheme is adopted according to the target yarn configuration: two conductive outer wrapping yarns and one thermochromic outer wrapping yarn can be configured at spindle positions 3, 6, and 9 respectively (where the thermochromic outer wrapping yarn corresponds to spindle position 9) to construct yarn configuration I;

[0073] S3. The first and second elastic spandex core yarns converge with the braided sheath at the bundling ring to form a yarn-shaped sensor. This sensor is then evenly wound onto a bobbin to complete the fabrication process.

[0074] Example 3

[0075] Please see Figure 2 , Figure 21 , Figure 22 , Figure 24Tables 1 and 2 illustrate a yarn-shaped sensor with both reversible color change and stretching effect. It comprises two parallel elastic spandex core yarns (i.e., elastic spandex core yarn one and elastic spandex core yarn two, the elastic spandex core yarns being coarse denier spandex yarns), two conductive outer covering yarns (i.e., silver-plated filament outer covering yarn one and silver-plated filament outer covering yarn two, i.e., silver-plated filament conductive outer covering yarn; this product uses nylon filament as the base material and is made with a silver-plated surface, wherein the silver plating mass is 17%), and one thermochromic outer covering yarn (i.e., coated thermochromic outer covering yarn, polyester base, specifically a coated thermosensitive color-changing yarn). Specifically, the two conductive outer yarns and the one thermochromic outer yarn are respectively arranged at spindle positions 3, 9, and 8 (where the thermochromic outer yarn corresponds to spindle position 8) to ensure that the two conductive outer yarns and the thermochromic outer yarn are wound and wrapped around the surface of the two elastic core yarns in a spiral path in the same direction.

[0076] The yarn-shaped sensor has the characteristic of undergoing reversible color change under voltage excitation, and this change is related to the working length of the yarn-shaped sensor. Therefore, by applying a predetermined voltage to both ends of the yarn-shaped sensor, a reversible color change can be generated between the energized and de-energized states. To achieve electrochromic response, a voltage of 1V / cm (i.e., 1V per centimeter) can be applied to both ends of the yarn-shaped sensor. The specific operating steps are as follows: First, conductive copper sheets are attached to both ends of the yarn-shaped sensor as electrodes. Then, the two clamps of a DC regulated power supply are used to clamp the copper sheets at both ends of the yarn-shaped sensor to connect the circuit. By adjusting the output voltage of the DC regulated power supply, a corresponding voltage is applied to the yarn-shaped sensor, thereby exciting the yarn-shaped sensor to produce a corresponding dynamic color-changing effect.

[0077] In addition, a method for preparing a yarn-shaped sensor that combines reversible color change and stretching effect, using a 90-type 369-spindle braiding machine, includes the following steps:

[0078] S1. By applying a pre-stretch of 1.5 times to the spandex core yarn through the active feed roller, the two elastic spandex core yarns are unwound from the bobbin in a taut state; then, they are respectively guided by the yarn guide hook to the hollow spindle one and hollow spindle two corresponding to the center positions of the two meshing first and second corner wheels on the base of the braiding machine, and are drawn out from the upper ends of hollow spindle one and hollow spindle two respectively; the active feed roller is used to control the stretching and conveying of the elastic spandex core yarns;

[0079] S2. On the first and second corner wheels, two yarn tubes wrapped with conductive outer yarn (i.e., silver-plated filament outer yarn one and silver-plated filament outer yarn two) and one yarn tube wrapped with thermochromic outer yarn are inserted according to a specific pattern (i.e., the two conductive outer yarns and one thermochromic outer yarn are respectively positioned at spindle positions 3, 9, and 8; where the thermochromic outer yarn corresponds to spindle position 8). During the weaving process, the outer yarn moves clockwise and counterclockwise along a specific path around the elastic spandex core yarn one and the elastic spandex core yarn two, passing over one elastic spandex core yarn in turn, and then crossing under the other elastic spandex core yarn to form a continuous figure-eight winding cycle, which together constitutes the braided sheath layer. The wrapping density of the braided sheath layer is controlled by adjusting the gear transmission ratio of the braiding machine. The gear ratio (gear 1: gear 2: gear 3: gear 4) is 28:22:26:46; wherein, the specific pattern and specific path are for forming the yarn configuration II.

[0080] The installation of the outer wrapping yarn described in S2 follows the following rules: To ensure the stability of the yarn sensor structure and the basic consistency of the feeding tension of each outer wrapping yarn, the three outer wrapping yarns are distributed on two meshing first and second corner pulleys to avoid uneven overall arrangement caused by the outer wrapping yarns being concentrated on a single corner pulley. A corresponding spindle configuration scheme is adopted according to the target yarn configuration: two conductive outer wrapping yarns and one thermochromic outer wrapping yarn can be configured at spindle positions 3, 9, and 8 respectively (where the thermochromic outer wrapping yarn corresponds to spindle position 8) to construct yarn configuration II;

[0081] S3. The first and second elastic spandex core yarns converge with the braided sheath at the bundling ring to form a yarn-shaped sensor. This sensor is then evenly wound onto a bobbin to complete the fabrication process.

[0082] Example 4

[0083] Please see Figure 2 , Figure 21 , Figure 22 , Figure 24Tables 1 and 2 illustrate a yarn-shaped sensor with both reversible color change and stretching effect. It comprises two parallel elastic spandex core yarns (i.e., elastic spandex core yarn one and elastic spandex core yarn two, the elastic spandex core yarns being coarse denier spandex yarns), two conductive outer covering yarns (i.e., silver-plated filament outer covering yarn one and silver-plated filament outer covering yarn two, i.e., silver-plated filament conductive outer covering yarn; this product uses nylon filament as the base material and is made with a silver-plated surface, wherein the silver plating mass is 17%), and one thermochromic outer covering yarn (i.e., coated thermochromic outer covering yarn, polyester base, specifically a coated thermosensitive color-changing yarn). Specifically, the two conductive outer yarns and the one thermochromic outer yarn are respectively arranged at spindle positions 3, 9, and 8 (where the thermochromic outer yarn corresponds to spindle position 8) to ensure that the two conductive outer yarns and the thermochromic outer yarn are wound and wrapped around the surface of the two elastic core yarns in a spiral path in the same direction.

[0084] The yarn-shaped sensor has the characteristic of undergoing reversible color change under voltage excitation, and this change is related to the working length of the yarn-shaped sensor. Therefore, by applying a predetermined voltage to both ends of the yarn-shaped sensor, a reversible color change can be generated between the energized and de-energized states. To achieve electrochromic response, a voltage of 1V / cm (i.e., 1V per centimeter) can be applied to both ends of the yarn-shaped sensor. The specific operating steps are as follows: First, conductive copper sheets are attached to both ends of the yarn-shaped sensor as electrodes. Then, the two clamps of a DC regulated power supply are used to clamp the copper sheets at both ends of the yarn-shaped sensor to connect the circuit. By adjusting the output voltage of the DC regulated power supply, a corresponding voltage is applied to the yarn-shaped sensor, thereby exciting the yarn-shaped sensor to produce a corresponding dynamic color-changing effect.

[0085] In addition, a method for preparing a yarn-shaped sensor that combines reversible color change and stretching effect, using a 90-type 369-spindle braiding machine, includes the following steps:

[0086] S1. By applying a pre-stretch of 2.8 times to the spandex core yarn through the active feed roller, the two elastic spandex core yarns are unwound from the bobbin in a taut state; then, they are respectively guided by the yarn guide hook to the hollow spindle one and hollow spindle two corresponding to the center positions of the two meshing first and second corner wheels on the base of the braiding machine, and are drawn out from the upper ends of hollow spindle one and hollow spindle two respectively; the active feed roller is used to control the stretching and conveying of the elastic spandex core yarns;

[0087] S2. Two yarn tubes wrapped with conductive outer yarn and one yarn tube wrapped with thermochromic outer yarn are inserted on two corner wheels according to a specific pattern (i.e., the two conductive outer yarns and one thermochromic outer yarn are respectively positioned at spindle positions 3, 9, and 8; where the thermochromic outer yarn corresponds to spindle position 8). During the weaving process, the outer yarn moves clockwise and counterclockwise around the two elastic spandex core yarns along a specific path, passing over one elastic spandex core yarn in turn and then crossing under the other elastic spandex core yarn, forming a continuous figure-eight winding cycle, which together constitutes the braided sheath layer. The wrapping density of the braided sheath layer is controlled by adjusting the gear transmission ratio of the braiding machine. The gear ratio (gear 1: gear 2: gear 3: gear 4) is 20:22:40:46; wherein, the specific pattern and specific path are for forming the yarn configuration II.

[0088] The installation of the outer wrapping yarn described in S2 follows these rules: To ensure the stability of the yarn sensor structure and the basic consistency of the feeding tension of each outer wrapping yarn, the three outer wrapping yarns are distributed on two meshing cams to avoid uneven overall arrangement caused by the outer wrapping yarns being concentrated on a single cam. A corresponding spindle configuration scheme is adopted according to the target yarn configuration: two conductive outer wrapping yarns and one thermochromic outer wrapping yarn can be configured at spindle positions 3, 9, and 8 respectively (where the thermochromic outer wrapping yarn corresponds to spindle position 8), to construct yarn configuration II;

[0089] S3. The first and second elastic spandex core yarns converge with the braided sheath at the bundling ring to form a yarn-shaped sensor. This sensor is then evenly wound onto a bobbin to complete the fabrication process.

[0090] Example 5

[0091] In this invention, yarn configuration I involves placing two conductive outer yarns and one thermochromic outer yarn at spindle positions 3, 6, and 9 (with the thermochromic outer yarn corresponding to spindle position 9), while yarn configuration II involves placing two conductive outer yarns and one thermochromic outer yarn at spindle positions 3, 9, and 8 (with the thermochromic outer yarn corresponding to spindle position 8). The core principle of this invention's yarn structure design is to arrange the thermochromic outer yarn adjacent to at least one conductive outer yarn, thereby utilizing the Joule heating effect of the conductive outer yarn to quickly trigger the color-changing effect of the thermochromic outer yarn. However, placing the two conductive outer yarns and one thermochromic outer yarn at the corner wheel spindle slots 2, 9, and 6 (with the thermochromic outer yarn corresponding to spindle position 6) is as follows: Figure 22 As shown.

[0092] Comparative Example 1

[0093] The yarn of this invention is prepared using a braiding machine. Hollow spindle wrapping spinning technology and the braiding technology of this invention belong to different spinning systems. Based on the hollow spindle wrapping spinning machine, a bundled, stretched yarn structure can be formed, such as... Figure 20 As shown; including the following steps:

[0094] Step S1: Two low-modulus, high-elongation fiber filaments, one and two low-modulus, high-elongation fiber filaments, are unwound using an active feed roller and fed into the lower hollow spindle center tubes one and two, respectively, to form two core filaments, denoted as core filament one and core filament two. Step S2: The high-modulus, low-elongation fiber filament one is wound in a positive spiral configuration around the surface of core filament one at the lower yarn guide hook, and the high-modulus, low-elongation fiber filament two is wound in a negative spiral configuration around the surface of core filament two at the lower yarn guide hook, thus forming a biaxial core-sheath structure covered yarn system, which passes through the upper hollow spindle center tube. Step S3: At the upper yarn guide hook, the fiber filament yarn with excellent elastic elongation wound on the upper hollow spindle is bound to the surface of the biaxial core-sheath structure covered yarn system with a low spiral covering density, forming a yarn-shaped sensor.

[0095] A schematic diagram of the yarn-shaped sensor is shown below. Figure 20 As shown in Figure a, under axial tension, this yarn-shaped sensor can produce a significant tensile expansion effect. To further verify the applicability of this process, a biaxial core-sheath structure system was constructed using 1680 D spandex (as a low-modulus, high-elongation filament) as the core yarn and 140 D / 48f silver-plated filament (as a high-modulus, low-elongation filament) as the covering material. Subsequently, two specifications of elastic yarns, namely 150 D polyester high-elastic yarn and 40 D spandex elastic yarn, were wrapped on the outside. This ultimately forms two specifications of bundled yarn sensors, such as... Figure 20 As shown in b-20c.

[0096] Comparative Example 2

[0097] The difference from Example 1 is that only the conductive outer yarn is replaced with conventional cotton yarn, while all other parameters and conditions are the same as in Example 1.

[0098] Comparative Example 3

[0099] The difference from Example 1 is that only the thermochromic outer yarn is replaced with conventional cotton yarn, while all other parameters and conditions are the same as in Example 1.

[0100] Comparative Example 4

[0101] The difference from Example 1 is that all three outer yarns are replaced with conventional cotton yarn; all other parameters and conditions are the same as in Example 1.

[0102] Please see Figures 1-19 , Figures 21-25The key parameters for weaving yarn in various embodiments of the present invention are detailed in Table 1;

[0103] Table 1. Key parameters for yarn weaving in each embodiment.

[0104]

[0105] In the gear transmission ratio, the number of teeth of gear 2 and gear 4 remains constant; that is, the number of teeth of gear 2 is 22 and the number of teeth of gear 4 is 46. Different densities of weaving and winding are achieved by changing the number of teeth of gear 1 and gear 3.

[0106] The three raw materials selected in this invention were determined based on reverse engineering of demand: spandex elastic yarn is intended to provide sufficient tensile recovery elasticity; conductive outer yarn is used to achieve excellent strain sensing performance and as a Joule heating element; thermochromic outer yarn can be excited to produce a reversible color-changing response after an external voltage is applied.

[0107] In the above embodiments and comparative examples: coarse denier spandex was purchased from Zhuji Haoting Chemical Fiber Business Department, a commercially available product with a fineness range of 840 D-2500 D; silver-plated conductive outer yarn was purchased from Qingdao Hengtong Weiye Special Fabric Technology Co., Ltd., a commercially available product with a yarn count range of 40 D-400 D and a specification of 140 D / 48F; coated thermosensitive color-changing outer yarn was purchased from Fujian Jinhaosheng Textile Technology Co., Ltd., a commercially available product with a yarn count of 150 D, double-ply yarn, and a Z-twist twist direction; polyester high-elastic yarn was purchased from Anhui Sanbo New Material Technology Co., Ltd., with a specification of 150 D; spandex elastic yarn was purchased from Haining Kaiwei Textile Co., Ltd., with a specification of 40 D; and conventional cotton yarn had a specification of 32s / 2.

[0108] Experimental data characterization and performance testing

[0109] The weaving and yarn properties of Examples 1-4 were tested, and the specific test results are shown in Table 2 and 3. Figures 3-19 Among them, the expansion effect corresponds to Figures 3-7 Cyclic tensile mechanics Figures 8-11 Reversible color change corresponds to Figures 12-15 The strain sensor tensile working range corresponds to Figures 16-19 The manual tensile strain ranges in Table 2 were obtained by performing manual tensile tests on the samples prepared in the corresponding embodiments.

[0110] Table 2. Schematic diagram of yarn weaving performance test data for each embodiment.

[0111]

[0112] Please see Figures 3-7According to Table 2, the relevant operating steps for the tensile performance of the yarn-like sensor in this invention are as follows: Fix both ends of the yarn-like sensor to the movable left and right clamps of the positive and negative threaded screw slide, and place the slide directly below the USB microscope. Connect the USB microscope to the computer to acquire images of the yarn-like sensor in real time. Set the initial clamping length of the yarn-like sensor to 2 cm, and apply different axial tensile strains to the yarn-like sensor by manually rotating the slide knob, simultaneously acquiring images under each strain state. Import the acquired images into ImageJ software to test the outer contour diameter of the yarn under different tensile strains. By comparing the increase in diameter of the stretched yarn-like sensor with the initial unstretched state, it is determined whether the yarn-like sensor has a tensile effect.

[0113] Depend on Figure 3 The results show that, observed from the front view, the outer diameter of the yarn-shaped sensor prepared in Example 1 gradually decreases during stretching, while the relative positions of the components within the yarn exchange. Compared to the initial unstretched state, the outer diameter of the yarn-shaped sensor decreases by 35.71% and 40.48%, respectively, when the tensile strain reaches 25% and 50%. This result indicates that, in the front view direction, the yarn-shaped sensor prepared in Example 1 does not exhibit a tensile expansion effect.

[0114] Depend on Figure 4 The results show that, observed from the side view, the outer diameter of the yarn-shaped sensor prepared in Example 1 gradually increases during the stretching process, while the relative positions of the components within the yarn exchange. Compared to the initial unstretched state, when the tensile strain reaches 50%, the outer diameter of the yarn-shaped sensor increases by 13.64%. This result indicates that, in the side view direction, the yarn-shaped sensor prepared in Example 1 possesses excellent tensile strength.

[0115] Depend on Figure 5 The results show that, observed from the side view, the outer diameter of the yarn-shaped sensor prepared in Example 2 gradually increases during the stretching process, while the relative positions of the components within the yarn exchange. Compared to the initial unstretched state, when the tensile strain reaches 150%, the outer diameter of the yarn-shaped sensor increases by 26.67%. This result indicates that, in the side view direction, the yarn-shaped sensor prepared in Example 2 possesses excellent tensile strength.

[0116] Depend on Figure 6The results show that, observed from the side view, the outer diameter of the yarn-shaped sensor prepared in Example 3 gradually increases during the stretching process, while the relative positions of the components within the yarn exchange. Compared to the initial unstretched state, when the tensile strain reaches 50%, the outer diameter of the yarn-shaped sensor increases by 22.73%. This result indicates that, in the side view direction, the yarn-shaped sensor prepared in Example 3 possesses excellent tensile strength.

[0117] Depend on Figure 7 The results show that, observed from the side view, the outer diameter of the yarn-shaped sensor prepared in Example 4 gradually increases during the stretching process, while the relative positions of the components within the yarn exchange. Compared to the initial unstretched state, the outer diameter of the yarn-shaped sensor increases by 10% when the tensile strain reaches 200%. This result indicates that, in the side view direction, the yarn-shaped sensor prepared in Example 4 possesses excellent tensile strength.

[0118] Please see Figures 8-11 According to Table 2, the cyclic tensile mechanical property testing steps in this invention are as follows: To study the cyclic mechanical behavior of the yarn-like sensor prepared by the system under repeated stretching, a PT-1198GTD-C type tensile testing machine was used for cyclic tensile testing. The effective distance between the fixtures was set to 5 cm. The yarn-like sensor was subjected to cyclic loading under a set tensile strain, and its mechanical response was recorded. The tensile strength and elongation performance testing steps of the yarn-like sensor are as follows: The tensile strength and elongation performance testing of the yarn-like sensor was performed in accordance with the relevant provisions of GB / T 3916—2013 "Determination of breaking strength and elongation at break of single yarn in packaged yarn (CRE method)" and FZ / T 12010—2011 "Cotton and spandex core-spun natural yarn". A YG(B)021DL type electronic single yarn strength tester was used, with a distance of 50 mm, a stretching speed of 500 mm / min, and a pre-tension of 0.5 cN / tex. Each group of samples was tested 20 times, and the average value of the results was taken.

[0119] Depend on Figure 8 (a) It can be seen that the yarn-shaped sensor prepared in Example 1 did not show significant mechanical property degradation after 50 cycles of tensile stress with a large strain of 50%, demonstrating good cyclic stability and structural durability. Meanwhile, according to... Figure 8 (b) Related results: The components of the yarn sensor have significant differences in mechanical properties, which leads to multi-stage fracture characteristics during the stretching process, and the final fracture mode is a typical multi-peak fracture.

[0120] Depend on Figure 9(a) It can be seen that the yarn-shaped sensor prepared in Example 2 did not show significant mechanical property degradation after 50 cycles of 150% large strain tensile stress, demonstrating good cyclic stability and structural durability. Meanwhile, according to Figure 9 (b) Related results: The components of the yarn sensor have significant differences in mechanical properties, which leads to multi-stage fracture characteristics during the stretching process, and the final fracture mode is a typical multi-peak fracture.

[0121] Depend on Figure 10 (a) It can be seen that the yarn-shaped sensor prepared in Example 3 did not show significant mechanical property degradation after 50 cycles of tensile stress with a large strain of 50%, demonstrating good cyclic stability and structural durability. Meanwhile, according to... Figure 10 (b) Related results: The components of the yarn sensor have significant differences in mechanical properties, which leads to multi-stage fracture characteristics during the stretching process, and the final fracture mode is a typical multi-peak fracture.

[0122] Depend on Figure 11 (a) It can be seen that the yarn-shaped sensor prepared in Example 4 did not show significant mechanical property degradation after 50 cycles of 200% large strain, demonstrating good cyclic stability and structural durability. Meanwhile, according to... Figure 11 (b) Related results: The components of the yarn sensor have significant differences in mechanical properties, which leads to multi-stage fracture characteristics during the stretching process, and the final fracture mode is a typical multi-peak fracture.

[0123] Please see Figures 12-15 According to Table 2, the electrothermal color-changing experimental steps in this invention are as follows: First, conductive copper sheets are attached as electrodes to both ends of the yarn-shaped sensor, maintaining an effective spacing length of 4 cm. Then, the copper sheets at both ends of the yarn-shaped sensor are clamped using the two clamps of a DC regulated power supply to connect the circuit. The output voltage of the DC regulated power supply is adjusted to 4 V, and the color-changing behavior of the yarn-shaped sensor is observed. Furthermore, its reversible color-changing response is examined by switching the voltage.

[0124] Depend on Figure 12 It can be seen that under a 4V external voltage excitation, the yarn-shaped sensor prepared in Example 1 can rapidly change from purple to pink. By periodically controlling the on / off state of the external voltage, the yarn-shaped sensor exhibits a stable and obvious reversible color-changing response. Figure 13 It can be seen that under a 4V external voltage excitation, the yarn-shaped sensor prepared in Example 2 can rapidly change from purple to pink. By periodically controlling the on / off state of the external voltage, the yarn-shaped sensor exhibits a stable and obvious reversible color-changing response. Figure 14It can be seen that under a 4V external voltage excitation, the yarn-shaped sensor prepared in Example 3 can rapidly change from purple to pink. By periodically controlling the on / off state of the external voltage, the yarn-shaped sensor exhibits a stable and obvious reversible color-changing response. Figure 15 It can be seen that under an external voltage of 4 V, the yarn-shaped sensor prepared in Example 4 can quickly change from purple to pink. By periodically controlling the external voltage, the yarn-shaped sensor exhibits a stable and obvious reversible color-changing response.

[0125] Please see Figures 16-19 According to Table 2, the strain sensing performance testing steps in this invention are as follows: To systematically evaluate the strain sensing performance of the prepared yarn-shaped sensor, conductive copper sheets were attached to both ends of the yarn-shaped sensor, connected to the LinkZill-01RC resistance testing system, and clamped in the PT-1198GTD-C type tensile testing machine fixture, with an effective spacing of 3cm. First, the yarn-shaped sensor was subjected to a single stretch at a tensile speed of 250 mm / min until it broke, and its resistance change was recorded simultaneously. Subsequently, five cycles of tensile testing were performed under a constant strain condition of 50% to examine its electrical response stability and service durability under repeated strain.

[0126] Figure 16 (a) shows the evolution of the resistance change rate of the yarn-shaped sensor prepared in Example 1 as a function of tensile strain, exhibiting a typical nonlinear positive correlation characteristic. In the initial stage of strain, the curve rises gently, and the resistance change rate increases slowly; after reaching a certain strain, the slope of the curve increases significantly, and the resistance change rate rises rapidly. Figure 16 The resistance change cycle curve in (b) fully demonstrates the service stability of the yarn-shaped sensor prepared in Example 1 as a strain sensor.

[0127] Figure 17 (a) shows the evolution of the resistance change rate of the yarn-shaped sensor prepared in Example 2 as a function of tensile strain, exhibiting a typical nonlinear positive correlation characteristic. In the initial stage of strain, the curve rises gently, and the resistance change rate increases slowly; after reaching a certain strain, the slope of the curve increases significantly, and the resistance change rate rises rapidly. Figure 17 The resistance change cycle curve in (b) fully demonstrates the service stability of the yarn-shaped sensor prepared in Example 2 as a strain sensor.

[0128] Figure 18 (a) shows the evolution of the resistance change rate of the yarn-shaped sensor prepared in Example 3 as a function of tensile strain, exhibiting a typical nonlinear positive correlation characteristic. In the initial stage of strain, the curve rises gently, and the resistance change rate increases slowly; after reaching a certain strain, the slope of the curve increases significantly, and the resistance change rate rises rapidly. Figure 18The resistance change cycle curve in (b) fully demonstrates the service stability of the yarn-shaped sensor prepared in Example 3 as a strain sensor.

[0129] Figure 19 (a) shows the evolution of the resistance change rate of the yarn-shaped sensor prepared in Example 4 as a function of tensile strain, exhibiting a typical nonlinear positive correlation characteristic. In the initial stage of strain, the curve rises gently, and the resistance change rate increases slowly; after reaching a certain strain, the slope of the curve increases significantly, and the resistance change rate rises rapidly. Figure 19 The resistance change cycle curve in (b) fully demonstrates the service stability of the yarn-shaped sensor prepared in Example 4 as a strain sensor.

[0130] The results of Embodiment 5 of the present invention show that, in this layout, the two silver-plated filaments are located on one side, while the thermosensitive color-changing yarn is located on the other side. The two are relatively separated, which to some extent is not conducive to the rapid response of the electrothermal color-changing behavior.

[0131] Observation of the spinning process in Comparative Example 1 of this invention shows that, overall, the target yarn-shaped sensor can be successfully spun using this technology. However, the following two main problems were observed in some sections of the yarn-shaped sensor: First, the two single-wrap yarn units in the biaxial core-sheath structure system inside the yarn-shaped sensor are prone to entanglement, forming a twisted cross structure. Figure 20 (b) It is impossible to maintain an ideal straight and parallel state, which is not conducive to the stable performance of the stretching effect; secondly, it is difficult for the two single-cover yarns in the system to maintain a completely mirror-symmetrical arrangement, and there is more or less some misalignment between them. Figure 20 c), which further affected the prominence of the inflationary effect.

[0132] In Comparative Example 2, the yarn-shaped sensor exhibited only a certain tensile effect and did not show strain sensing behavior or thermosensitive color change effect. In Comparative Example 3, the yarn-shaped sensor also exhibited a certain tensile effect and had strain sensing behavior, but did not have thermosensitive color change effect. In Comparative Example 4, the yarn-shaped sensor exhibited only a certain tensile effect, and both strain sensing and thermosensitive color change effects were missing.

[0133] The comparative experiments above show that the raw material combination set by the present invention has a clear functional orientation. The synergistic configuration of conductive outer yarn and thermochromic outer yarn is a necessary condition for realizing strain sensing and thermochromic functions, which fully demonstrates the necessity and irreplaceability of the present invention in terms of material selection.

[0134] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, because according to the present invention, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are all optional embodiments, and the actions and modules involved are not necessarily essential to the present invention.

Claims

1. A yarn-like sensor with reversible color change and auxetic effect, characterized in that: The yarn-shaped sensor includes a core layer and a braided sheath layer; The core layer consists of two elastic spandex core filaments as the structural skeleton, which are arranged in parallel. The braided sheath layer is formed by binding the two elastic spandex core filaments together with an outer sheath yarn through a braided structure. The outer sheath yarn includes two conductive outer sheath yarns and one thermochromic outer sheath yarn. The yarn-shaped sensor is formed by spirally winding two conductive outer yarns together with thermochromic outer yarns; wherein the winding shape is a figure "8" shape. The relative spatial positions of the two conductive outer yarns and the thermochromic outer yarn are adjusted to form yarn-shaped sensors with different configurations. The configuration of the yarn-shaped sensor includes one or more of yarn-forming configuration I and yarn-forming configuration II; The yarn configuration I consists of two conductive outer yarns wound around the surface of the two elastic spandex core yarns in opposite spiral paths, and distributed symmetrically in a cross pattern on the surface of the yarn-shaped sensor. The thermochromic outer yarn is wrapped in the same spiral direction as one of the conductive outer yarns. The yarn configuration II consists of two conductive outer yarns and a thermochromic outer yarn, both wound sequentially in a spiral path in the same direction and wrapped around the surface of the two elastic core yarns.

2. The yarn-like sensor with reversible color change and stretch effect according to claim 1, characterized in that: The elastic spandex core yarn is coarse denier spandex yarn with a fineness of 840D-2500D; the conductive outer yarn is silver-plated filament with a fineness of 40D-400D.

3. A yarn-shaped sensor with both reversible color change and stretching effect according to claim 2, characterized in that: The thermochromic outer yarn is a coated thermosensitive color-changing yarn with a color-changing response temperature threshold of 30℃-65℃.

4. A yarn-shaped sensor with both reversible color change and stretching effect according to claim 1, characterized in that: The weaving structure is an "8"-shaped winding loop structure, which makes all the outer yarns together form a braided sheath layer that binds two elastic spandex core yarns.

5. A method for preparing a yarn-shaped sensor, characterized in that, To prepare a yarn-shaped sensor with reversible color change and tensile effect as described in claims 1-4, the preparation is carried out using a braiding machine, comprising the following steps: S1. By applying a predetermined multiple of pre-stretch through the active feed roller, the two elastic spandex core yarns are unwound from the bobbin in a taut state; then, they are respectively guided by the yarn guide hooks to the hollow spindle one and hollow spindle two corresponding to the center positions of the two meshing first and second corner wheels on the braiding machine chassis, and are drawn out from the upper ends of hollow spindle one and hollow spindle two respectively; the active feed roller is used to control the stretching and conveying of the elastic spandex core yarns; S2. On the first and second corner wheels, insert two yarn tubes with conductive outer sheath yarn and one yarn tube with thermochromic outer sheath yarn according to a specific pattern. During the weaving process, the outer sheath yarn moves clockwise and counterclockwise around the first and second elastic spandex core yarns in a specific path, passing over one elastic spandex core yarn in turn and then crossing under the other elastic spandex core yarn, forming a continuous figure-eight winding cycle, which together constitutes the braided sheath layer.

6. The method for preparing a yarn-shaped sensor according to claim 5, characterized in that: It also includes the following steps: S3. The elastic spandex core yarn one and elastic spandex core yarn two converge with the braided sheath layer at the bundling ring to form a yarn-shaped sensor; then it is evenly wound onto the bobbin to complete the preparation work.

7. The method for preparing a yarn-shaped sensor according to claim 5, characterized in that: In S1, the elastic spandex core yarn one and elastic spandex core yarn two are pre-stretched by actively feeding rollers, and the pre-stretch ratio is controlled within the range of 1.25-3.50; around the two meshing first and second corner rollers, multiple spindles for inserting outer covering yarn are evenly distributed along a reverse figure-eight path.

8. The method for preparing a yarn-shaped sensor according to claim 5, characterized in that, The installation of the outer covering yarn described in S2 includes the following steps: S21. Distribute the three outer yarns onto two meshing first and second angular pulleys; the three outer yarns include two conductive outer yarns and one thermochromic outer yarn. S22. Two conductive outer yarns are wound around the surface of the two elastic spandex core yarns in opposite spiral paths and are distributed in a cross-symmetrical manner on the surface of the yarn sensor. The thermochromic outer yarn is wrapped in the same spiral direction as one of the conductive outer yarns to obtain yarn configuration I. Two conductive outer yarns and a thermochromic outer yarn are wound and wrapped around the surface of the two elastic core yarns in a spiral path in the same direction to obtain yarn configuration II.

9. The method for preparing a yarn-shaped sensor according to claim 5, characterized in that: In step S2, the wrapping density of the braided sheath layer is controlled by adjusting the gear transmission ratio of the braiding machine. The number of teeth on the gears is an even number, ranging from 20 to 46.

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