A highly flexible core-shell structure conductive magnetic fiber and its preparation method and application

Abstract

The present invention discloses a highly flexible core-shell structure conductive magnetic fiber and its preparation method and application, belonging to the technical field of polymer materials and conductive materials. The method of the present invention can continuously prepare conductive magnetic fibers with core-shell structures in large quantities without multiple operation steps, avoiding the shortcomings of the multi-step method for synthesizing core-shell structures, which is cumbersome, wastes experimental consumables and reagents, and wastes time. It has the advantages of being simple, efficient, low-cost, and time-saving. The highly flexible core-shell structure conductive magnetic fiber prepared has the characteristics of high flexibility, strong conductivity, and adjustable magnetism, and exhibits hydrophobicity and good electromagnetic shielding performance, and has good application prospects in the fields of sensing detection, electromagnetic shielding, etc.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials and conductive materials, and specifically relates to a highly flexible core-shell structured conductive magnetic fiber and a preparation method and application thereof. Background Art

[0002] The development of wearable electronic devices and communication technologies in various fields has brought significant convenience to human life, but it has also caused serious problems such as electromagnetic radiation and interference. Consequently, research on protective fiber fabrics has attracted increasing attention. Traditional protective fiber fabrics require high concentrations of rigid conductive or magnetic fillers to achieve satisfactory conductivity or magnetic properties, which often results in poor fiber flexibility and stability.

[0003] The emerging flexible liquid metal (LM) has recently attracted widespread attention from researchers due to its excellent fluidity and electrical conductivity. However, the high surface tension of LM complicates its processing within fiber structures. Furthermore, exposed liquid metal is susceptible to oxidation and migration and removal by external forces. Therefore, it is necessary to construct a rationally stretchable liquid metal conductive fiber structure.

[0004] However, the current method for preparing such stretchable liquid metal conductive fibers is relatively cumbersome, requiring two or even multiple steps to couple the stretchable material and the liquid material together. This type of method ([1]Angew. Chem., Int. Ed. 2013, 52,13453−13457.[2]Journal of Materials Research and Technology.2023.25.4728-4738.[3]Chemical Engineering Journal 10.1016 / j.cej.2021.129962.) is complex and requires not only a large amount of organic solvents but also a high-cost manufacturing process. It is not only time-consuming and reagent-intensive but also cannot be prepared continuously, which limits its practical production and makes it difficult to further promote its application.

[0005] The preparation of conductive fibers based on coaxial wet spinning technology is a viable strategy to address the shortcomings of the aforementioned processes. For example, Chinese invention patent publication number CN114703555A discloses a one-step batch production method for core-shell structured liquid metal conductive fibers. The method involves extracting a polyurethane solution using a shell syringe and extracting a gallium-based liquid metal using a core syringe. To begin spinning, the shell syringe pump is first activated, extruding the polyurethane solution through the syringe pump and solidifying it through a coagulation bath. The core syringe pump is then activated to ensure that the liquid metal is sealed within the polyurethane shell, thereby producing a core-shell structured liquid metal conductive fiber with a liquid metal core and a polyurethane shell. This invention overcomes the high surface tension of liquid metal, resulting in liquid metal conductive fibers with excellent stretchability and conductivity. Another example, Chinese invention patent publication number CN111549396A provides a liquid metal-encapsulated fiber and a method for preparing the same. First, a hollow polymer fiber is obtained. After being collected via a conveyor belt and a turntable, liquid metal is injected into the fiber cavity to form the liquid metal-encapsulated fiber. The fiber prepared by the invention has uniform structure, controllable size, good conductivity, and can be stretched and deformed.

[0006] However, the above processes mainly focus on the production and preparation of conductive fibers, while magnetic powder must be added during the manufacturing process of magnetic fibers. Magnetic powder particles, as a hard material, will degrade the tensile properties of the fiber after addition. This degradation is particularly pronounced under high load conditions, thus affecting the subsequent normal use of the magnetic fiber. Therefore, designing a simple, low-cost, and large-scale continuous production method to prepare fibers with high flexibility, high conductivity, and adjustable magnetism is of great significance to related fields such as wearable electronic devices and communication technologies. Summary of the Invention

[0007] In view of the above-mentioned defects of the prior art, in a first aspect of the present invention, a method for preparing a highly flexible core-shell structured conductive magnetic fiber is provided, which has a simple process, low cost, and is conducive to large-scale continuous production, and comprises the following steps:

[0008] (1) Preparation of magnetic continuous phase solution:

[0009] Dissolving thermoplastic polyurethane in an organic solvent to obtain a polyurethane solution; adding a polymer dispersant to the polyurethane solution to form a uniform foam solution; then adding magnetic powder to the uniform foam solution and mixing to obtain a magnetic continuous phase solution;

[0010] (2) Preparation of magnetic conductive metal dispersed phase solution:

[0011] The liquid metal is treated with acid to remove its surface oxide layer, and then magnetic powder is added to the liquid metal, followed by ultrasonic dispersion and washing to obtain a magnetic conductive metal dispersed phase solution;

[0012] (3) Preparation of highly flexible core-shell conductive magnetic fibers:

[0013] Coaxial spinning is carried out using a magnetic continuous phase solution and a magnetic conductive metal dispersed phase solution as the raw materials for the shell layer and the core layer respectively. The injection rate of the shell layer is controlled to be greater than that of the core layer, so that the core layer is squeezed and wrapped in the shell layer at the outlet of the coaxial spinning needle, and then continuously formed into a line in a rotating coagulation bath to obtain a highly flexible core-shell structured conductive magnetic fiber.

[0014] The organic solvent should have good solubility and be able to fully dissolve the polyurethane for easy processing and application. The polarity of the organic solvent should be close to that of the polyurethane molecules to achieve effective dissolution. Common organic solvents for dissolving polyurethane include ketones, aromatic hydrocarbons, and amides, such as dimethylformamide, acetone, butanone, and toluene, all of which are suitable for the present invention.

[0015] Preferably, in step (1), the organic solvent includes at least one of dimethylformamide, acetone, butanone, and toluene.

[0016] Polymer dispersants have excellent dispersing effects and can effectively disperse particulate matter into solvents to form a uniform and stable dispersion system. In particular, in the present invention, polymer dispersants represented by polyvinyl pyrrolidone, polyacrylic acid, and polyvinyl alcohol can not only promote the dispersion of magnetic powder, but also achieve high load through the foam structure they form. The amount and molecular weight of the polymer dispersant are appropriately controlled within an appropriate range. When its molecular weight is too low, it cannot function as a dispersant and cannot be used to adjust the load of magnetic powder; when its molecular weight is too high, it is difficult to dissolve, which will affect its adsorption effect on the particle surface, thereby reducing the dispersion efficiency, or forming flocculation, seriously affecting the dispersion effect.

[0017] Preferably, in step (1), the polymer dispersant includes one of polyvinyl pyrrolidone, polyacrylic acid, and polyvinyl alcohol.

[0018] Preferably, in step (1), the weight average molecular weight of the polymer dispersant is 1,000-2,000,000.

[0019] Preferably, in step (1), the mass ratio of thermoplastic polyurethane to polymer dispersant is 10:1-10.

[0020] Preferably, in step (1), in the uniform foam solution, the concentration of the thermoplastic polyurethane is 1 wt.%-20 wt.%; and the concentration of the polymer dispersant is 1 wt.%-20 wt.%.

[0021] High magnetic powder loading generally degrades stretchability. Existing technology achieves a stretchability of approximately 350% without a magnetic shell. However, the process of this invention leverages the porous structure of the foam to ensure the fiber retains tensile resilience even in the presence of hard magnetic powder. This allows the fiber to achieve a 350% stretchability target even with a magnetic shell, without significant degradation. Furthermore, magnetic properties can be adjusted by adjusting the proportion of magnetic powder added.

[0022] Preferably, in step (1), the concentration of the magnetic powder in the magnetic continuous phase solution is 10 wt.%-70 wt.%.

[0023] Preferably, in step (1) and step (2), the magnetic powder includes one of iron powder, ferrite powder and Ru-Fe-B powder.

[0024] Among liquid metals, gallium-indium-tin alloys or gallium-indium alloys have very low melting points, usually below room temperature, which means they can remain liquid at room temperature. These alloys are biocompatible materials and are suitable as raw materials for wearable flexible electronic devices. Among them, commercially available Ga68.5In21.5Sn10 and Ga75In25 (the symbol and number represent the element type and mass fraction, respectively) are particularly suitable liquid metal choices due to their cost-effectiveness and wide availability.

[0025] Preferably, in step (2), the liquid metal includes a gallium-indium-tin alloy or a gallium-indium alloy.

[0026] Further preferably, the liquid metal includes a gallium-indium-tin alloy Ga68.5In21.5Sn10 or a gallium-indium alloy Ga75In25.

[0027] Preferably, in step (2), the proportion of magnetic powder used in the liquid metal is 1 wt.%-10 wt.%.

[0028] Preferably, in the step (3), during the coaxial spinning process, the injection rate of the magnetic continuous phase solution is 10-20 mL / h; the injection rate of the magnetic conductive metal dispersed phase solution is 5-10 mL / h.

[0029] The overall fiber diameter of the highly flexible core-shell structured conductive magnetic fiber can be adjusted by changing the inner diameters of the two syringe needles to obtain fibers of different specifications to flexibly meet the needs of different applications.

[0030] Preferably, in step (3), the inner diameter of the needle for injecting the magnetic continuous phase solution is 0.3-3 mm; the inner diameter of the needle for injecting the magnetic conductive metal dispersed phase solution is 0.2-2 mm.

[0031] Preferably, in step (3), the speed of the rotating coagulation bath is 10-500 r / min.

[0032] In the second aspect of the present invention, a highly flexible core-shell structured conductive magnetic fiber with high flexibility, strong conductivity and adjustable magnetism is provided, which is prepared by the preparation method of the first aspect of the present invention.

[0033] In the third aspect of the present invention, an application of the highly flexible core-shell structured conductive magnetic fiber according to the second aspect of the present invention is provided, specifically, an application as a fiber material in sensing detection and electromagnetic shielding.

[0034] Preferably, the application includes the following steps: fixing the highly flexible core-shell structure conductive magnetic fiber at the finger joints, and when the finger bending angle increases, the corresponding output voltage also increases, so that different gestures produce clear and repeatable signal patterns.

[0035] Further preferably, the length of the highly flexible core-shell structured conductive magnetic fiber is 3-6 cm.

[0036] Preferably, the application comprises the following steps: making the highly flexible core-shell structured conductive magnetic fiber into a fiber braid and using it for electromagnetic shielding.

[0037] Since magnetic powder is a hard material, as the magnetic powder loading rate increases, the extrusion of the wet coaxial spinning shell will become increasingly difficult, resulting in discontinuous fiber preparation. This is the technical difficulty that the process of the present invention needs to solve. During the research and development stage, the inventors found that simply mixing thermoplastic polyurethane, polymer dispersant, and magnetic powder together is difficult to make the fiber have a high magnetic powder loading rate. Based on the above technical scheme, the design concept and principle of the present invention is that after adding the dispersant to form a uniform foam solution, the magnetic powder is added, so that a large amount of magnetic powder can be dispersed in the foam structure of the former, thereby promoting the realization of high load. By utilizing the difference in the injection rate of the core layer and the shell layer solution, the magnetic conductive metal dispersed phase solution and the magnetic continuous phase solution are squeezed and wrapped in the shell layer at the outlet of the coaxial spinning needle based on fluid mechanics. Since magnetic powder is added to the raw materials of the shell layer and the core layer in this process, there is a magnetic interaction force between the core layer magnetic powder and the shell layer magnetic powder. When prepared in this way, the core layer is continuously formed into a line under the combined action of gravity, centrifugal force and interaction force with the shell layer magnetic powder in the rotating coagulation bath device. In this way, the micro-particle structure of the magnetic powder is used to adjust the surface tension of the liquid metal so that the core layer liquid can be continuously extruded. The polymer dispersant is also combined to adjust the loading rate of the core layer magnetic powder, adjust the shell-core structure in terms of size, and adjust the magnetic properties of the conductive fiber, making the preparation method simple, efficient, and capable of large-scale continuous preparation.

[0038] A large amount of uniform foam solution can be formed through simple mixing methods. For example, in actual operation, the desired effect can be achieved by adding a polymer dispersant in small amounts multiple times, followed by stirring at room temperature. Subsequently, the desired total amount of magnetic powder can be added in small amounts multiple times and dispersed in the foam using mechanical stirring. Those skilled in the art may also adopt other mixing methods to achieve the preparation of a uniform foam solution and the dispersion of the magnetic powder, depending on actual conditions. A rotating coagulation bath apparatus is a simple coagulation bath device capable of rotating clockwise or counterclockwise about its longitudinal axis (relative to the horizontal axis) and containing a coagulation bath, such as water. Compared to the prior art method that uses a stretching roller structure to cause the core layer to undergo volume changes under stretching to form a continuous conductive medium, this method can form a continuous line under the influence of the aforementioned forces, and the liquid metal in the core layer exhibits good continuity without the need for stretching. As a result, the fibers produced by this process can be stored directly in the coagulation bath, eliminating the need for stretching rollers and improving space utilization.

[0039] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0040] The present invention provides a method for preparing highly flexible core-shell structured conductive magnetic fibers, which can continuously prepare conductive magnetic fibers with core-shell structures in large quantities without multiple operating steps, avoiding the shortcomings of the multi-step method for synthesizing core-shell structures, which is cumbersome, wastes experimental consumables and reagents, and wastes time. This method has the advantages of being simple, efficient, low-cost, and time-saving.

[0041] The present invention provides a highly flexible core-shell structured conductive magnetic fiber, which has the characteristics of high flexibility, strong conductivity, adjustable magnetism, and exhibits hydrophobicity and good electromagnetic shielding performance.

[0042] The present invention provides an application of a highly flexible core-shell structured conductive magnetic fiber, which has good application prospects in the fields of sensing detection, electromagnetic shielding, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Schematic diagram of the process for preparing highly flexible core-shell structured conductive magnetic fibers using coaxial wet spinning;

[0044] Figure 2 These are optical photographs of the highly flexible core-shell conductive magnetic fiber prepared in Example 1; Figure (a) is an optical photograph of the fiber, and Figure (b) is an optical photograph of a continuously prepared fiber with a length of nearly 2 m.

[0045] Figure 3 The scanning electron microscope (SEM) image and element scanning image of the cross section of the highly flexible core-shell structure conductive magnetic fiber prepared in Example 1;

[0046] Figure 4 This is a stretching picture of the highly flexible core-shell structure conductive magnetic fiber prepared in Example 1;

[0047] Figure 5 1 is the magnetic property (HM) curve of the highly flexible core-shell structure conductive magnetic fiber prepared in Example 1-3;

[0048] Figure 6 The conductivity images of the highly flexible core-shell conductive magnetic fiber prepared in Example 1. (a)-(d) correspond to blue, green, yellow, and white LED bulbs, respectively.

[0049] Figure 7 This is a picture of the real-time output electrical signal of the highly flexible core-shell structure conductive magnetic fiber prepared in Example 1 under different gesture changes in application;

[0050] Figure 8 The contact angle of the highly flexible core-shell conductive magnetic fiber prepared in Example 1;

[0051] Figure 9 The electromagnetic shielding performance of the highly flexible core-shell structured conductive magnetic fiber prepared in Example 1. DETAILED DESCRIPTION

[0052] The present invention is further illustrated by way of examples below, but the present invention is not limited to the scope of the examples. Experimental methods in the following examples where specific conditions are not specified were performed according to conventional methods and conditions, or selected according to the product specifications.

[0053] Example 1

[0054] The preparation method of highly flexible core-shell structure conductive magnetic fiber comprises the following steps:

[0055] (1) Preparation of magnetic continuous phase solution:

[0056] 2 g of thermoplastic polyurethane was placed in 20 mL of N,N-dimethylformamide solution, heated and stirred at 60 °C for 12 h, and then allowed to cool at room temperature to completely dissolve the thermoplastic polyurethane, obtaining a polyurethane solution. 0.5 g of polyvinyl pyrrolidone (Mw: 1300000) powder was then added to the polyurethane solution, followed by mechanical stirring for 1 h to form a uniform foam solution. 1.2 g of rubidium iron boron powder was then added in batches, ultrasonically dispersed, allowed to stand, and then rinsed with deionized water to obtain a magnetic continuous phase solution.

[0057] (2) Preparation of magnetic conductive metal dispersed phase solution:

[0058] Gallium indium tin alloy (Ga68.5In21.5Sn10) was placed in dilute hydrochloric acid and ultrasonically dispersed to remove the insulating oxide layer on its surface. Rubidium iron boron powder was then added at a concentration of 5 wt.% of the gallium indium tin alloy. After ultrasonic dispersion, the mixture was allowed to stand for a period of time and then washed with deionized water to obtain a magnetic conductive metal dispersed phase solution.

[0059] (3) Preparation of highly flexible core-shell conductive magnetic fibers:

[0060] like Figure 1 As shown, the magnetic continuous phase solution and the magnetic conductive metal dispersed phase solution are used as the raw materials of the shell layer and the core layer respectively, and are loaded into the syringes of the coaxial wet spinning device respectively. The syringes are connected to the inner and outer phase ports of the coaxial spinning needle respectively, and two propellers are used to propel the shell layer syringe and the core layer syringe respectively. The injection rate of the shell layer is controlled to be 15 mL / h, and the injection rate of the core layer is controlled to be 8 mL / h; deionized water is used as the coagulation bath, and the different injection rates of the two propellers are used. The magnetic conductive metal dispersed phase solution and the magnetic continuous phase solution squeeze and wrap the core layer in the shell layer at the outlet of the coaxial spinning needle through fluid mechanics. The core layer is continuously formed into a line in the rotating coagulation bath device under the combined action of gravity, centrifugal force and interaction force with the shell magnetic powder, thereby obtaining a highly flexible core-shell structured conductive magnetic fiber.

[0061] Optical photos of highly flexible core-shell conductive magnetic fibers Figure 2 Figure (a) is an optical photograph of the fiber, and Figure (b) is an optical photograph of a continuously prepared fiber with a length of nearly 2 m. This method produces the finished product required by the design.

[0062] The cross section of the highly flexible core-shell structured conductive magnetic fiber was characterized by SEM and element scanning. Figure 3 shown. Figure 3 It shows that the shell layer of the highly flexible core-shell structured conductive magnetic fiber has a porous structure, proving that the target structure is formed by a uniform foam solution in the process, which helps to prevent the performance degradation of magnetic particles while taking into account stretchability.

[0063] This example studies the tensile properties of the prepared highly flexible core-shell conductive magnetic fiber. Figure 4 As shown in the figure, a 2 cm long fiber is fixed at one end and the other end is mechanically stretched to its maximum length. The original length of the 2 cm fiber can be stretched to 7 cm, and the stretching rate can reach 350%.

[0064] A 1 cm long highly flexible core-shell conductive magnetic fiber was placed in a superconducting quantum interference device for testing at 300 K. The magnetic property curve is shown in the figure below. Figure 5As shown. At 2000 Oe, the saturation magnetization of the fiber can reach 0.25 emu. Combined with the test results of Examples 2 and 3 below, the magnetic properties of the highly flexible core-shell conductive magnetic fiber can be easily adjusted by adjusting the amount of magnetic powder added.

[0065] The resistance of the highly flexible core-shell conductive magnetic fiber was tested using a digital multimeter, and the resistance value was 6.1 Ω. Figure 6 As shown in the figure, an external voltage (1.8-3 V) and an 8 cm conductive fiber are connected in series with blue, green, yellow, and white LED bulbs, respectively. When the external voltage is turned on, the corresponding LED bulb can be lit. When the voltage is turned off, the LED bulb goes out, proving that the conductive fiber has good conductivity.

[0066] Example 2

[0067] The preparation method of this embodiment is basically the same as that of embodiment 1, except that the amount of rubidium iron boron powder added in this embodiment is 1.0 g. The magnetic property curve is tested using the same method as above, and the results are as follows: Figure 5 The magnetic properties of the highly flexible core-shell structure conductive magnetic fiber of this embodiment were measured at 300 K, and the saturation magnetization intensity at 20,000 Oe was 0.21emu.

[0068] Example 3

[0069] The preparation method of this embodiment is basically the same as that of embodiment 1, except that the amount of rubidium iron boron powder added in this embodiment is 0.8 g. The magnetic property curve is tested using the same method as above, and the results are as follows: Figure 5 The magnetic properties of the highly flexible core-shell structure conductive magnetic fiber of this embodiment were measured at 300 K, and the saturation magnetization intensity at 20,000 Oe was 0.15 emu.

[0070] Example 4

[0071] In this embodiment, the highly flexible core-shell conductive magnetic fiber prepared in Example 1 is applied to sensing detection. Figure 7 As shown, five highly flexible core-shell structured conductive magnetic fibers are fixed at the five finger joints. When the finger bending angle increases, the corresponding output voltage also increases. Each gesture movement can produce a clear and repeatable signal pattern.

[0072] Example 5

[0073] In this embodiment, the highly flexible core-shell conductive magnetic fiber prepared in Example 1 is further woven into a fabric through warp and weft threads, and the hydrophilicity and hydrophobicity of the fabric are measured in a contact angle meter. Figure 8As shown in the figure, the contact angle results show that the fabric exhibits hydrophobic properties. The fabric was then cut into 10×10 mm 2 The electromagnetic shielding performance of the fabric was tested using the Agilent N5244A vector network analyzer. The waveguide method was used and the test frequency range was 8.2-12.4 GHz (X-band). The results are as follows: Figure 9 As shown in the figure, the magnetic shielding effectiveness was 30.1 dB, as determined by testing and calculation. These results demonstrate that the conductive fiber exhibits hydrophobicity and electromagnetic shielding properties in its applications.

[0074] Example 6

[0075] The preparation method of highly flexible core-shell structure conductive magnetic fiber comprises the following steps:

[0076] (1) Preparation of magnetic continuous phase solution:

[0077] Thermoplastic polyurethane (concentration: 1 wt.%) was placed in acetone, heated and stirred at 60°C for 12 hours, and then allowed to cool at room temperature to completely dissolve the thermoplastic polyurethane, thereby obtaining a polyurethane solution. Polyacrylic acid (Mw: 2,000,000; concentration: 1 wt.%) powder was then added to the polyurethane solution and mechanically stirred for 1 hour to form a uniform foam solution. The mass ratio of thermoplastic polyurethane to polyacrylic acid was 10:1. Ferrite powder (concentration: 10 wt.%) was then added in batches, ultrasonically dispersed, allowed to stand, and then rinsed with deionized water to obtain a magnetic continuous phase solution.

[0078] (2) Preparation of magnetic conductive metal dispersed phase solution:

[0079] Gallium-indium alloy (Ga75In25) is placed in dilute hydrochloric acid and ultrasonically dispersed to remove the insulating oxide layer on its surface. Ferrite powder with a mass of 1 wt.% of the gallium-indium alloy is then added. After ultrasonic dispersion, the mixture is allowed to stand for a period of time and then washed with deionized water to obtain a magnetic conductive metal dispersed phase solution.

[0080] (3) Preparation of highly flexible core-shell conductive magnetic fibers:

[0081] The magnetic continuous phase solution and the magnetic conductive metal dispersed phase solution were used as the raw materials of the shell layer and the core layer respectively, and were loaded into the syringes of the coaxial wet spinning device. The syringes were connected to the inner and outer phase ports of the coaxial spinning needle respectively, and two propellers were used to propel the shell layer syringe and the core layer syringe respectively. The injection rate of the shell layer was controlled to be 10 mL / h, and the injection rate of the core layer was controlled to be 5 mL / h. Deionized water was used as the coagulation bath. The magnetic conductive metal dispersed phase solution and the magnetic continuous phase solution squeezed and wrapped the core layer in the shell layer at the outlet of the coaxial spinning needle through fluid mechanics by utilizing the different injection rates of the two propellers. The core layer was continuously formed into a line in the rotating coagulation bath device under the combined action of gravity, centrifugal force and interaction force with the shell magnetic powder, thereby producing a highly flexible core-shell structured conductive magnetic fiber.

[0082] Example 7

[0083] The preparation method of highly flexible core-shell structure conductive magnetic fiber comprises the following steps:

[0084] (1) Preparation of magnetic continuous phase solution:

[0085] Thermoplastic polyurethane (concentration: 20 wt.%) was placed in toluene, heated and stirred at 60°C for 12 hours, and then allowed to cool at room temperature to completely dissolve the thermoplastic polyurethane, thereby obtaining a polyurethane solution. Polyvinyl alcohol (Mw: 1000; concentration: 20 wt.%) powder was then added to the polyurethane solution and mechanically stirred for 1 hour to form a uniform foam solution. The mass ratio of thermoplastic polyurethane to polyvinyl alcohol was 1:1. Ferrite powder (concentration: 70 wt.%) was then added in batches, ultrasonically dispersed, allowed to stand, and then rinsed with deionized water to obtain a magnetic continuous phase solution.

[0086] (2) Preparation of magnetic conductive metal dispersed phase solution:

[0087] Gallium indium tin alloy (Ga68.5In21.5Sn10) is placed in dilute hydrochloric acid and ultrasonically dispersed to remove the insulating oxide layer on its surface. Ferrite powder with a mass ratio of 10wt.% of the gallium indium tin alloy is then added. After ultrasonic dispersion, the mixture is allowed to stand for a period of time and then washed with deionized water to obtain a magnetic conductive metal dispersed phase solution.

[0088] (3) Preparation of highly flexible core-shell conductive magnetic fibers:

[0089] The magnetic continuous phase solution and the magnetic conductive metal dispersed phase solution were used as the raw materials of the shell layer and the core layer respectively, and were loaded into the syringes of the coaxial wet spinning device. The syringes were connected to the inner and outer phase ports of the coaxial spinning needle respectively, and two propellers were used to propel the shell layer syringe and the core layer syringe respectively. The injection rate of the shell layer was controlled to be 10 mL / h, and the injection rate of the core layer was controlled to be 5 mL / h. Deionized water was used as the coagulation bath. The magnetic conductive metal dispersed phase solution and the magnetic continuous phase solution squeezed and wrapped the core layer in the shell layer at the outlet of the coaxial spinning needle through fluid mechanics by utilizing the different injection rates of the two propellers. The core layer was continuously formed into a line in the rotating coagulation bath device under the combined action of gravity, centrifugal force and interaction force with the shell magnetic powder, thereby producing a highly flexible core-shell structured conductive magnetic fiber.

[0090] Example 8

[0091] The preparation method of highly flexible core-shell structure conductive magnetic fiber comprises the following steps:

[0092] (1) Preparation of magnetic continuous phase solution:

[0093] Thermoplastic polyurethane (concentration: 10 wt.%) was placed in butanone, heated and stirred at 60°C for 12 hours, and then allowed to cool at room temperature to completely dissolve the thermoplastic polyurethane, thereby obtaining a polyurethane solution. Polyvinyl pyrrolidone (Mw: 40,000; concentration: 10 wt.%) powder was then added to the polyurethane solution and mechanically stirred for 1 hour to form a uniform foam solution. The mass ratio of thermoplastic polyurethane to polyvinyl pyrrolidone was 5:1. Iron powder (concentration: 40 wt.%) was then added in batches, ultrasonically dispersed, allowed to stand, and then rinsed with deionized water to obtain a magnetic continuous phase solution.

[0094] (2) Preparation of magnetic conductive metal dispersed phase solution:

[0095] Gallium indium tin alloy (Ga68.5In21.5Sn10) is placed in dilute hydrochloric acid and ultrasonically dispersed to remove the insulating oxide layer on its surface. Iron powder is then added at a mass ratio of 5 wt.% of the gallium indium tin alloy. After ultrasonic dispersion, the mixture is allowed to stand for a period of time and then washed with deionized water to obtain a magnetic conductive metal dispersed phase solution.

[0096] (3) Preparation of highly flexible core-shell conductive magnetic fibers:

[0097] The magnetic continuous phase solution and the magnetic conductive metal dispersed phase solution were used as the raw materials of the shell layer and the core layer respectively, and were loaded into the syringes of the coaxial wet spinning device. The syringes were connected to the inner and outer phase ports of the coaxial spinning needle respectively, and two propellers were used to propel the shell layer syringe and the core layer syringe respectively. The injection rate of the shell layer was controlled to be 20 mL / h, and the injection rate of the core layer was controlled to be 10 mL / h. Deionized water was used as the coagulation bath. The magnetic conductive metal dispersed phase solution and the magnetic continuous phase solution squeezed and wrapped the core layer in the shell layer at the outlet of the coaxial spinning needle through fluid mechanics by utilizing the different injection rates of the two propellers. The core layer was continuously formed into a line in the rotating coagulation bath device under the combined action of gravity, centrifugal force and interaction force with the shell magnetic powder, thereby producing a highly flexible core-shell structured conductive magnetic fiber.

[0098] In summary, in the preparation method of the present invention, a uniform foam solution is formed by adding a dispersant, and then the magnetic powder is added, so that a large amount of magnetic powder is dispersed in the foam structure of the former, promoting the realization of high load, and the porous structure of the shell formed by the foam structure is used to maintain the tensile properties of the fiber, preventing the magnetic powder from deteriorating the performance. The present invention utilizes the difference in injection rates of the two propellers to allow the magnetic conductive metal dispersed phase solution and the magnetic continuous phase solution to squeeze and wrap the core layer in the shell layer at the outlet of the coaxial spinning needle based on fluid mechanics. Since magnetic powder is added to the raw materials of the shell layer and the core layer in this process, there is a magnetic interaction force between the core layer magnetic powder and the shell layer magnetic powder. Therefore, during the preparation, the core layer is continuously formed into a line under the combined action of gravity, centrifugal force and interaction force with the shell layer magnetic powder in the rotating coagulation bath device. In this way, the micro-particle structure of the magnetic powder is used to adjust the surface tension of the liquid metal so that the core layer liquid can be continuously extruded. The polymer dispersant is also combined to adjust the loading rate of the core layer magnetic powder, adjust the shell-core structure in terms of size, and adjust the magnetic properties of the conductive fiber, making the preparation method simple, efficient, and capable of large-scale continuous preparation.

[0099] The highly flexible core-shell conductive magnetic fiber fabricated using this process features adjustable core-shell dimensions, adjustable overall fiber diameter, and tunable magnetic properties. This conductive fiber exhibits excellent, continuous conductivity, enabling the illumination of LED bulbs of varying colors using a relatively low voltage (1-3 V). The fiber is also hydrophobic and exhibits electromagnetic shielding properties, achieving an electromagnetic shielding efficiency of 30.1 dB within the 8.2-12.4 GHz X-band frequency range. When used for sensing, the real-time output electrical signals generated by the power-down process are clear and distinct in response to different gestures, demonstrating broad application prospects.

[0100] The above describes in detail the preferred embodiments of the present invention. It should be understood that those skilled in the art can make numerous modifications and variations based on the concepts of the present invention without inventive effort. Therefore, any technical solutions that can be derived by those skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A method for preparing a highly flexible core-shell structured conductive magnetic fiber, characterized in that: The steps include: (1) Preparation of magnetic continuous phase solution: Dissolving thermoplastic polyurethane in an organic solvent to obtain a polyurethane solution; adding a polymer dispersant to the polyurethane solution to form a uniform foam solution; then adding magnetic powder to the uniform foam solution and mixing to obtain a magnetic continuous phase solution; The polymer dispersant includes one of polyvinyl pyrrolidone, polyacrylic acid, and polyvinyl alcohol; the weight average molecular weight of the polymer dispersant is 1000-2000000; (2) Preparation of magnetic conductive metal dispersed phase solution: The liquid metal is treated with acid to remove its surface oxide layer, and then magnetic powder is added to the liquid metal, followed by ultrasonic dispersion and washing to obtain a magnetic conductive metal dispersed phase solution; (3) Preparation of highly flexible core-shell conductive magnetic fibers: Coaxial spinning is carried out using a magnetic continuous phase solution and a magnetic conductive metal dispersed phase solution as the raw materials for the shell layer and the core layer respectively. The injection rate of the shell layer is controlled to be greater than that of the core layer, so that the core layer is squeezed and wrapped in the shell layer at the outlet of the coaxial spinning needle, and then continuously formed into a line in a rotating coagulation bath to obtain a highly flexible core-shell structured conductive magnetic fiber.

2. The method for preparing a highly flexible core-shell conductive magnetic fiber according to claim 1, characterized in that: In the step (1), the organic solvent includes at least one of dimethylformamide, acetone, butanone, and toluene.

3. The method for preparing a highly flexible core-shell conductive magnetic fiber according to claim 1, wherein: In the step (1), the mass ratio of thermoplastic polyurethane to polymer dispersant is 10:1-10.

4. The method for preparing a highly flexible core-shell conductive magnetic fiber according to claim 1, wherein: In the step (1), in the uniform foam solution, the concentration of thermoplastic polyurethane is 1 wt.%-20 wt.%; the concentration of polymer dispersant is 1 wt.%-20 wt.%; and the concentration of magnetic powder in the magnetic continuous phase solution is 10 wt.%-70 wt.%.

5. The method for preparing a highly flexible core-shell conductive magnetic fiber according to claim 1, wherein: In the step (2), the liquid metal includes a gallium-indium-tin alloy or a gallium-indium alloy; the proportion of the magnetic powder used in the liquid metal is 1 wt.%-10 wt.%.

6. The method for preparing a highly flexible core-shell conductive magnetic fiber according to claim 1, wherein: In the step (3), during the coaxial spinning process, the injection rate of the magnetic continuous phase solution is 10-20 mL / h; the injection rate of the magnetic conductive metal dispersed phase solution is 5-10 mL / h; the inner diameter of the needle for injecting the magnetic continuous phase solution is 0.3-3 mm; the inner diameter of the needle for injecting the magnetic conductive metal dispersed phase solution is 0.2-2 mm; and the speed of the rotating coagulation bath is 10-500 r / min.

7. A highly flexible core-shell conductive magnetic fiber, characterized by: The method is as described in any one of claims 1 to 6.

8. An application of the highly flexible core-shell conductive magnetic fiber according to claim 7, characterized in that: Application as fiber material in sensing detection and electromagnetic shielding.

9. The use of the highly flexible core-shell structured conductive magnetic fiber according to claim 8, characterized in that: The application includes the following steps: fixing highly flexible core-shell structured conductive magnetic fibers at the finger joints. When the finger bending angle increases, the corresponding output voltage also increases, so that different gestures produce clear and repeatable signal patterns.

10. The use of the highly flexible core-shell structured conductive magnetic fiber according to claim 8, characterized in that: The application comprises the following steps: preparing a fiber braid from a highly flexible core-shell structured conductive magnetic fiber and using the braid for electromagnetic shielding.

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