Magnetic response multi-dimensional deformation carbon nanotube composite fiber and preparation method and application thereof

Abstract

The invention provides a magnetic response multi-dimensional deformation carbon nanotube composite fiber and a preparation method and application thereof. The preparation method comprises the following steps: applying ultrasonic treatment to a fiber precursor; the fiber precursor is immersed in a solution of a magnetic material precursor, so that the magnetic material precursor is diffused into the fiber precursor; carrying out annealing treatment to obtain a pre-assembly body; twisting to form a twisted fiber body; and winding on a cylindrical body, and carrying out instantaneous Joule heat treatment shaping to obtain the magnetic response multi-dimensional deformation carbon nanotube composite fiber. According to the preparation method, a magnetic material precursor is fully permeated into carbon nanotube fibers in a solution dipping manner, uniformly dispersed and combined soft magnetic particles are formed after annealing treatment, spiral shaping is realized through an instantaneous Joule heating effect, and a carbon nanotube fiber body is tightly wrapped to form firm combination; the magnetic composite fiber provided by the invention has the characteristics of extremely strong flexibility, high strength, high conductivity and no failure such as interlayer stripping, and has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of materials science and technology, specifically relating to a magnetically responsive multidimensional deformation carbon nanotube composite fiber, its preparation method, and its application. Background Technology

[0002] With the development of flexible electronics, microrobotics, and biomedical technologies, stringent requirements have been placed on intelligent actuator materials, including lightweight, high strength, large deformation, rapid response, and biocompatibility. Magnetic fibers, as one-dimensional linear actuators, have attracted much attention due to their simple structure, ease of integration, and ability to achieve complex three-dimensional motion, showing great application potential in intravascular microrobots, variable stiffness grippers, and wearable integrated sensing and actuation devices.

[0003] However, traditional magnetic fiber material systems have significant limitations and cannot simultaneously meet the comprehensive requirements of the above applications: metal alloy magnetic fibers (such as iron-cobalt-nickel based alloys) have excellent mechanical strength and magnetic saturation strength, but their density is too high and their flexibility (bending / torsion performance) is insufficient. In applications requiring large bending deformation or rapid reciprocating motion, they are prone to plastic deformation or fatigue fracture; polymer-based magnetic composite fibers have low density and good flexibility, but the matrix itself has low mechanical strength and poor conductivity; multilayer composite magnetic fibers (such as core-shell or layered structures with magnetic layers / elastic layers / support layers) can partially balance performance through structural design, but the interlayer interfaces are prone to peeling under repeated deformation, leading to performance degradation, and the preparation process is usually complex and difficult to achieve continuous and large-scale production. Summary of the Invention

[0004] The main objective of this invention is to provide a magnetically responsive multidimensional deformation carbon nanotube composite fiber, its preparation method, and its application, so as to overcome the shortcomings of the prior art.

[0005] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing magnetically responsive multidimensional deformation carbon nanotube composite fibers, comprising: The carbon nanotube fiber precursor is subjected to ultrasonic treatment to loosen the fiber bundles in the carbon nanotube fiber precursor. The ultrasonically treated carbon nanotube fiber precursor is immersed in a solution of magnetic material precursor, allowing the magnetic material precursor to diffuse into the interior of the carbon nanotube fiber precursor, thus obtaining a magnetic carbon nanotube precursor. The magnetic carbon nanotube precursor is annealed to convert the magnetic material precursor into soft magnetic particles, thereby obtaining a pre-assembled body. The pre-assembled body is twisted to form a twisted fiber body; The twisted fiber is coiled on a columnar body to form a spiral shape, and an electric current is applied to the twisted fiber. The twisted fiber is then shaped by instantaneous Joule heat treatment to obtain a magnetically responsive multidimensional deformation carbon nanotube composite fiber. The instantaneous Joule heat treatment temperature is above 1000℃ and the duration of the current application is within 3 minutes.

[0006] In a second aspect, the present invention also provides a magnetically responsive multidimensional deformation carbon nanotube composite fiber prepared by the above preparation method, which includes a carbon nanotube fiber body and soft magnetic particles. The carbon nanotube fiber body has a twist along its length axis and a macroscopic helical shape, and the soft magnetic particles are embedded in the gaps between the fiber bundles in the carbon nanotube fiber body.

[0007] Thirdly, the present invention also provides the application of the above-mentioned magnetically responsive multidimensional deformation carbon nanotube composite fiber in the field of magnetic drive.

[0008] Compared with the prior art, the beneficial effects of the present invention include at least the following: The preparation method provided by this invention allows the magnetic material precursor to fully penetrate into the interior of carbon nanotube fibers through solution impregnation. After annealing, uniformly dispersed and bonded soft magnetic particles are formed. At the same time, the helical shaping is achieved through the instantaneous Joule heating effect, so that the carbon nanotube fiber body tightly wraps the soft magnetic particles to form a strong bond. This provides a magnetic composite fiber with extremely high flexibility, high strength, high conductivity and no failure characteristics such as interlayer delamination, which has broad application prospects in the field of magnetic drive.

[0009] The above description is merely an overview of the technical solution of the present invention. In order to enable those skilled in the art to better understand the technical means of this application and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described below in conjunction with detailed drawings. Attached Figure Description

[0010] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 This is a partial flowchart illustrating the preparation method of magnetically responsive multidimensional deformation carbon nanotube composite fibers provided in a typical embodiment of the present invention. Figure 2 This is another part of the process flow diagram of the preparation method of magnetically responsive multidimensional deformation carbon nanotube composite fiber provided in a typical embodiment of the present invention; Figure 3 This is a comparative test diagram of the hysteresis loops of the original carbon nanotube fiber and the magnetically responsive multidimensional deformation carbon nanotube composite fiber provided in a typical embodiment of the present invention. Figure 4 This is a comparative test diagram of the mechanical strength of the original carbon nanotube fiber and the magnetically responsive multidimensional deformation carbon nanotube composite fiber provided in a typical embodiment of the present invention. Figure 5 This is a cross-sectional elemental distribution test diagram of magnetically responsive multidimensional deformation carbon nanotube composite fibers provided in a typical embodiment of the present invention; Figure 6 This is an electron microscope image of multidimensional deformation carbon nanotube composite fibers with different spring index magnetic responses, provided in a typical embodiment of the present invention.

[0012] Figure 7 This is an optical photograph of the magnetostrictive behavior of magnetically responsive multidimensional deformation carbon nanotube composite fibers provided in a typical embodiment of the present invention. Figure 8 This is a typical embodiment of the present invention, showing the magnetostriction curves of multidimensionally deformed carbon nanotube composite fibers under different loads. Figure 9 This is an optical photograph of the magneto-bending behavior of magnetically responsive multidimensional deformation carbon nanotube composite fibers provided in a typical embodiment of the present invention. Figure 10 This is a typical embodiment of the present invention, showing the relationship between the magnetostrictive bending angle and the magnetic field strength of multidimensional deformation carbon nanotube composite fibers with different strand numbers and different action lengths. Figure 11 This is an optical photograph of the targeted cargo delivery process of a microrobot made of magnetically responsive multidimensional deformation carbon nanotube composite fibers, provided in a typical embodiment of the present invention. Detailed Implementation

[0013] In view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The following will further explain and illustrate this technical solution, its implementation process, and its principles.

[0014] 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 therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0015] In view of the technical challenges pointed out in the background section above, the object of the present invention is: 1) Achieving deep and uniform loading of magnetic material precursors within carbon nanotube fibers via affinity wetting method. Utilizing the wetting characteristics of the magnetic material precursor solution and the preferential adsorption effect between the tube bundles, this method effectively solves the technical problems of uneven distribution of magnetic components and weak interfacial bonding between carbon nanotubes and magnetic components caused by conventional preparation methods. This endows the fibers with high and stable magnetic responsiveness, improving their magnetic response sensitivity under low field strength environments. At the same time, it completely preserves the original structure of carbon nanotubes, enabling the prepared magnetic carbon nanotube composite fibers to possess both excellent conductivity and mechanical strength, solving the problem of fiber conductivity and mechanical property degradation caused by traditional processes.

[0016] 2) To realize the combined application of Joule heat setting technology and the high conductivity magnetic carbon nanotube composite fiber of the present invention, relying on the unique advantage of the high conductivity of the fiber of the present invention to complete rapid setting, solving the defects of traditional high temperature external heating setting process that rely on large equipment, long setting time, damage to fiber mechanical properties, easy relaxation of helical structure and poor customization, and to achieve precise customization of fiber helical index, so as to meet the differentiated needs of fiber deformation ability in different application scenarios.

[0017] 3) Ultimately, a magnetic carbon nanotube fiber actuator with high magnetic responsiveness, high mechanical strength, high conductivity, and customizable macroscopic helical geometry is obtained, providing a high-performance, customizable, and easily fabricated core driving unit for cutting-edge fields such as micro soft robots, making up for the shortcomings of existing high-performance magnetic fiber actuators.

[0018] Based on the above technical approach, see Figure 1 and Figure 2 As shown, an embodiment of the present invention first provides a method for preparing magnetically responsive multidimensional deformation carbon nanotube composite fibers, which includes the following steps: The carbon nanotube fiber precursor is subjected to ultrasonic treatment to loosen the fiber bundles in the carbon nanotube fiber precursor. The ultrasonically treated carbon nanotube fiber precursor is immersed in a solution of magnetic material precursor, allowing the magnetic material precursor to diffuse into the interior of the carbon nanotube fiber precursor, thus obtaining a magnetic carbon nanotube precursor. The magnetic carbon nanotube precursor is annealed to convert the magnetic material precursor into soft magnetic particles, thereby obtaining a pre-assembled body. The pre-assembled body is twisted to form a twisted fiber body; The twisted fiber is coiled on a columnar body to form a spiral shape, and an electric current is applied to the twisted fiber. The twisted fiber is then shaped under a protective atmosphere using instantaneous Joule heat treatment to obtain a magnetically responsive multidimensional deformation carbon nanotube composite fiber. The instantaneous Joule heat treatment is performed at a temperature above 1000°C and the duration of the current application is less than 3 minutes.

[0019] In existing technologies for preparing magnetic carbon nanotube composite fibers, researchers have conducted extensive research to achieve high-performance magnetic fibers. The technical solutions closest to this invention mainly fall into two categories, but both have inherent defects that are difficult to overcome, as follows: 1) A class of prior art, represented by Chinese invention patent CN115404562A, discloses a method for preparing carbon nanotube composite fibers by physically mixing a carbon nanotube dispersion with a soluble metal salt precursor and then wet spinning. This process has significant technical shortcomings: the strong shearing action during the physical mixing process easily causes the carbon nanotubes to break and the tube wall structure to be damaged. This not only damages the originally excellent conductive network, resulting in a significant decrease in the conductivity of the prepared composite fiber, but also weakens the overall mechanical strength of the fiber due to the damaged aspect ratio of the carbon nanotubes and insufficient interfacial bonding between the metal salt and the carbon nanotubes. At the same time, it is difficult for the metal salt precursor to achieve uniform molecular-level dispersion in the carbon nanotube dispersion system. After subsequent spinning, the magnetic particles are prone to agglomeration, ultimately leading to uneven distribution of the magnetic properties of the fiber and failure to achieve efficient magnetic response.

[0020] 2) Another type of prior art, represented by Chinese invention patent with publication number CN102561007A, uses electrochemical deposition to deposit metal oxides on the surface of carbon nanotube fibers to prepare magnetic composite fibers. This method also has many limitations: electrochemical deposition uses fibers as working electrodes, and metal oxides can only be preferentially deposited on the fiber surface and cannot penetrate into the fiber interior, making it difficult to achieve a uniform bulk loading of magnetic components; moreover, this process has stringent equipment requirements, requiring a dedicated electrolysis device and strict control of parameters such as voltage and current density, making the operation process cumbersome. At the same time, the deposition effect is highly dependent on the conductivity of the fiber itself, resulting in poor process adaptability and large-scale preparation.

[0021] To address the aforementioned technical deficiencies, this invention innovatively employs an affinity wetting method to prepare magnetic carbon nanotube composite fibers. Compared to existing preparation techniques, its core advantages and unique technical differences lie in the following: The preparation method provided by this invention selects magnetic material precursors such as cobalt chloride, ferric chloride, and nickel chloride to prepare solutions. Utilizing the loose and porous structure of the carbon nanotube fiber precursors, and leveraging the strong electrostatic adsorption between carbon nanotubes and the ions of the magnetic material precursors, the magnetic material precursor solution rapidly and deeply wets into the interior of the carbon nanotube fibers. Furthermore, the magnetic material precursor ions preferentially adsorb between the tube bundles within the carbon nanotube fibers. The entire process requires no high-intensity physical mixing, nor complex electrochemical deposition equipment and operations, making the process simpler and the preparation efficiency higher. This preparation method can preserve the original micromechanical structure of carbon nanotube fibers to the greatest extent, while maintaining the high conductivity network characteristics of carbon nanotubes themselves. It fundamentally avoids the problem of conductivity and mechanical property degradation caused by carbon nanotube structure damage in the prior art. Moreover, the uniform wetting and preferential adsorption of magnetic material precursors in solution form can enable the magnetic components to achieve uniform bulk loading inside the carbon nanotube fibers. The elemental distribution map characterization results of the fiber cross-section in the embodiments of this invention can directly confirm this uniform loading effect.

[0022] In summary, the magnetic carbon nanotube composite fibers prepared by the affinity wetting method possess both excellent electrical conductivity and mechanical strength, and achieve uniform distribution of magnetic components within the fibers. This is the core and most unique technical advantage of the preparation method provided by this invention.

[0023] To achieve the magnetic drive performance of magnetic carbon nanotube composite fibers, high-temperature helical shaping of the fibers is a common industry practice. However, existing technologies rely on prolonged external heating at high temperatures, which has inherent drawbacks: prolonged high temperatures damage the internal structure of the carbon nanotube fibers, leading to a significant decrease in their mechanical properties; furthermore, the shaped helical structure is prone to relaxation and deformation during subsequent use, failing to maintain a stable magnetic drive morphology. Additionally, external heating requires large heating equipment, resulting in poor process flexibility and difficulty in customizing helical structures with different helical indices to meet the diverse requirements of different application scenarios regarding fiber deformation capacity and magnetic response. While Joule heating technology has applications in some conductive fiber fields, the core of this invention lies in the combined application of Joule heating technology with the highly conductive magnetic carbon nanotube composite fibers prepared by the affinity wetting method of this invention, rather than simply using Joule heating for shaping. Furthermore, Joule heating is a unique and inherent advantage of the magnetic carbon nanotube composite fibers described in this invention.

[0024] Specifically, the magnetic carbon nanotube composite fiber described in this invention retains the highly conductive network of carbon nanotubes through affinity wetting, exhibiting excellent conductivity and forming the core basis for Joule heat setting. In contrast, magnetic carbon nanotube composite fibers prepared using existing technologies suffer from poor conductivity and cannot be adapted to this setting method. The combined setting effect offers significant advantages: First, it eliminates the need for large external heating equipment, requiring only a simple power supply device for setting, resulting in low equipment requirements and a simple process. Second, it can instantly raise the fiber temperature to 1000℃ within a short time (within 3 minutes), using instantaneous high temperature to eliminate internal stress in the helical structure and achieve stable setting, completely avoiding the damage to fiber mechanical properties caused by traditional high-temperature, long-term setting. Third, by precisely controlling the power supply parameters, it can achieve precise customization of different helical indices of the fiber, producing magnetically responsive fibers with varying deformation capabilities. This perfectly adapts to the differentiated requirements of different application scenarios for fiber magnetic response deformation, demonstrating strong customization adaptability.

[0025] The carbon nanotube fiber precursor can be a narrow strip (such as a narrow strip prepared by floating vapor deposition), or a round fiber formed by preliminary treatment of the above narrow strip. Of course, it can also be a non-extremely densified carbon nanotube fiber or narrow strip prepared by other methods ("extreme densification" means that after mechanical stretching and twisting or after polymer composite, the degree of densification is extremely high, resulting in the partial carbon nanotube products that cannot be penetrated by external solutions).

[0026] Regarding specific implementation details, in some implementation schemes, the power of the ultrasonic treatment is 50-200W, and the duration is 3-10min.

[0027] In some embodiments, the magnetic material precursor comprises halides of iron-based elements.

[0028] In some embodiments, the solvent in the solution of the magnetic material precursor includes water and / or alcohol solvents.

[0029] In some embodiments, the solution of the magnetic material precursor is preferably an ethanol solution of cobalt chloride. Multiple experiments conducted according to this invention have shown that the magnetic properties of the magnetically responsive multidimensional deformation carbon nanotube composite fibers prepared using an ethanol solution of cobalt chloride are significantly stronger.

[0030] In some embodiments, the concentration of the magnetic material precursor solution is 0.5-2 mol / L.

[0031] In some embodiments, the impregnation time of the carbon nanotube fiber precursor is not less than 10 minutes.

[0032] In some embodiments, the annealing atmosphere is a mixture of inert gas and hydrogen, with a volume ratio of (1-4):1; the annealing temperature is 300-500°C, and the time is 20-60 min.

[0033] Furthermore, the present invention provides a preferred embodiment, namely: in some embodiments, the preparation method specifically includes the following steps: A first load is applied to twist the pre-assembled body to form the twisted fiber body; A second load is applied to coil the twisted fiber body around the columnar heating body, and the instantaneous Joule heat treatment is performed while maintaining the second load. The second load is 3 to 8 times the first load.

[0034] During twisting, a suitable load (or traction force) is usually applied to the fiber to prevent it from becoming locally over-twisted and agglomerated. Under a suitable load, by applying a suitable twist, twisted straight fibers similar to ropes can be formed. For example, in a typical embodiment, a suspension load of about 2g is used, but it is not limited to this. The appropriate twisting load may be different for carbon nanotube fiber precursors of different diameters and sources, and can be determined experimentally based on the conditions. When performing spiral heating and setting, it was found that a higher load needs to be maintained, at least 3 times the twisting load, usually about 5 times, and up to 8 times to prevent breakage.

[0035] This is because when the temperature reaches above 1000℃, slight slippage and rearrangement of carbon nanotube bundles will occur. If the original load during twisting is maintained at this time, or even a lower load or no load is applied, the fiber structure will become locally loose due to the high-temperature slippage phenomenon of the bundles. Soft magnetic particles are easy to detach from their original positions, thereby destroying the original fiber network structure and reducing the mechanical strength and cycle life of the magnetic response multidimensional deformation carbon nanotube composite fiber.

[0036] Therefore, through the discovery and exploration of the inventors of this invention, the method of using a 3-8 times twisting load to achieve instantaneous heating and shaping can largely preserve the mechanical strength and flexibility of the original carbon nanotube fibers, while providing the best recyclability.

[0037] The embodiments of the present invention also provide a magnetically responsive multidimensional deformation carbon nanotube composite fiber prepared by the preparation method provided in any of the above embodiments, which includes a carbon nanotube fiber body and soft magnetic particles; the carbon nanotube fiber body has a twist with the length direction as the axis and a macroscopic helical shape, and the soft magnetic particles are embedded in the gaps between the fiber bundles in the carbon nanotube fiber body.

[0038] This invention also provides the application of the above-mentioned magnetically responsive multidimensional deformation carbon nanotube composite fiber in the field of magnetic drive.

[0039] The technical solution of the present invention will be further described in detail below through several embodiments and in conjunction with the accompanying drawings. However, the selected embodiments are only for illustrating the present invention and do not limit the scope of the present invention.

[0040] Example 1 This embodiment has demonstrated a method for preparing magnetically responsive multidimensional deformation carbon nanotube composite fibers, as detailed below.

[0041] Step 1: Preparation of magnetic carbon nanotube fibers First, carbon nanotube fibers (narrow carbon nanotube bands prepared by floating vapor deposition) were subjected to ultrasonic pretreatment (ultrasonic power 100 W, ultrasonic time 5 min). Mechanical vibration broke up locally aggregated bundles within the carbon nanotube fibers, increasing the fiber's specific surface area and porosity, providing more sites for subsequent magnetic particle attachment. Then, the pretreated carbon nanotube fibers were immersed in a magnetic material precursor solution of the same concentration (1 mol / L, including an ethanol solution of ferric chloride, an ethanol solution of cobalt chloride, and an aqueous solution of nickel chloride) for 10 min. The strong electrostatic adsorption between the chlorides and carbon nanotubes enabled uniform adsorption and deposition of the magnetic precursors within the carbon nanotube fibers. Next, the fibers were annealed at 400℃ in an Ar / H2 atmosphere (flow ratio 2:1) for 30 min to complete the in-situ reduction of chlorides within the carbon nanotube fibers, thus obtaining pre-assembled bodies of various soft magnetic particles.

[0042] Through testing, the sample corresponding to the ethanol solution of CoCl2, which is the precursor of the magnetic material with the highest saturation magnetic moment density, can be selected. Subsequent tests will use this sample as the representative.

[0043] Step 2: Construction of the magnetic carbon nanotube fiber helical structure The prepared magnetic carbon nanotube fibers are uniformly wound onto rods of different diameters. The system is then placed in an argon atmosphere, and an electric current is passed through the magnetic carbon nanotube fibers. The fibers are rapidly heated to incandescence using Joule heating. After holding the temperature for several seconds, the current is cut off, and the rods are removed after natural cooling. This completes the rapid heat setting of the helical structure of the magnetic carbon nanotube fibers, resulting in magnetic carbon nanotube fibers with a stable helical structure.

[0044] The fabrication process of the fiber helical structure in this section plays a crucial role in determining its subsequent magnetically driven deformation performance. By replacing rods of different diameters, the winding angle between the fiber and the rod can be flexibly adjusted, and the fiber helical pitch can be precisely adjusted, thereby producing magnetic carbon nanotube helical fibers with different spring indices. Through the controllable adjustment of the fiber helical structure parameters, the prepared fibers can achieve different forms of magnetic response deformation such as bending, contraction, and rotation under the action of a magnetic field, which can precisely meet the differentiated requirements of different application scenarios for the type and degree of magnetically driven deformation of the fiber.

[0045] Experimental results: Figure 3 The magnetic hysteresis loops of the magnetically responsive multidimensional deformation carbon nanotube composite fiber and the carbon nanotube fiber precursor provided in this embodiment are shown. The saturation magnetic moment density of the original fiber is 8.45 emu / g, and the saturation magnetic moment density of the prepared magnetic carbon nanotube fiber is 107.73 emu / g, which is 12.7 times higher.

[0046] Figure 4 The mechanical strength curves of the magnetic carbon nanotube composite fiber and the carbon nanotube fiber precursor provided in this embodiment are shown. The mechanical strength of the original fiber is 168 MPa, and the mechanical strength of the prepared magnetic carbon nanotube composite fiber is 120 MPa, which is slightly lower, but still remains at the same level.

[0047] Figure 5 The cross-sectional surface scan energy spectrum of the magnetically responsive multidimensional deformation carbon nanotube composite fiber provided in this embodiment shows that the Co element is uniformly distributed in the cross-sectional area of ​​the carbon nanotube fiber (the carbon nanotube fiber precursor already contains iron element, which acts as a catalyst during growth). In addition, when other magnetic elements such as Fe and Ni are loaded using the affinity wetting method of this invention, the same excellent uniform distribution effect can be obtained in the cross-sectional area of ​​the carbon nanotube fiber.

[0048] Figure 6 These are electron microscope images of magnetic carbon nanotube helical fibers with different spring indices prepared in this embodiment. This invention successfully prepared magnetic carbon nanotube helical fibers with gradient spring indices (e.g., 3.57, 5.43, 7.08, 8.20, 9.96) by precisely controlling the mandrel diameter through a Joule heat setting process. Figure 6 As shown, from left to right, the spring index gradually increases, and the spiral fibers are evenly arranged and have a regular structure, indicating that the process can achieve stable and repeatable spiral structure shaping. This fully demonstrates that the present invention can achieve precise and controllable design of spiral structure through process parameters, providing a reliable structural basis for subsequent optimization of magnetostrictive drive performance and development of customized devices.

[0049] Example 2 This embodiment illustrates the magnetically driven cyclic application of the magnetically responsive multidimensional deformation carbon nanotube composite fiber provided in Example 1, as shown below: Figure 7 These are photographs of the magnetostrictive behavior of the magnetic carbon nanotube helical fibers described in this invention. In image a, the fiber is in its initial free state, with the helical structure stretched and its length stable. In image b, under the influence of an external magnetic field, the fiber undergoes axial contraction driven by the magnetic torque, resulting in a significant shortening of its overall length. It quickly returns to its initial state after the magnetic field is removed. Experimental results demonstrate that the magnetic carbon nanotube helical fibers prepared in this invention possess excellent magnetic response performance and deformation recovery capability. They can achieve reversible contraction-extension actuation under magnetic field control, providing an efficient wireless actuation unit for fields such as flexible actuators, microrobots, and smart fabrics.

[0050] Figure 8 This image shows the real-time actuation curves of the magnetic carbon nanotube helical fiber (spring index C=7.08) described in this invention under different loads (C) and magnetic field strengths. It can be seen that under a gradient magnetic field ranging from 200 mT to 1 T, the fiber can generate a stable and reversible actuation response, with the actuation amount increasing significantly with increasing magnetic field strength. Within a different load range from 270 mg to 612 mg, the fiber maintains efficient and rapid actuation behavior and good recovery, with the actuation amount showing a gradient trend with increasing load, demonstrating excellent load adaptability and actuation stability. The experimental results fully demonstrate that the magnetic carbon nanotube helical fiber prepared in this invention can achieve controllable and stable magnetostriction under a wide range of magnetic field and load conditions, providing a reliable performance basis for the customized design of devices such as flexible actuators, smart fabrics, and microrobots.

[0051] Figure 9 The images show physical representations of the magnetostrictive bending behavior of the magnetic carbon nanotube helical fibers described in this invention. In the smaller image (a), there is a superimposed view of various morphologies; in the smaller image (b), the fiber is in its initial free state, remaining straight and morphologically stable; and in the smaller images (ce), the fiber undergoes directional bending under the influence of an applied gradient magnetic field, driven by the magnetic torque. The bending angle gradually increases with increasing magnetic field strength, ultimately achieving a large 90° bend, and the fiber quickly returns to its initial straight state after the magnetic field is removed. Experimental results demonstrate that the magnetic carbon nanotube helical fibers prepared in this invention possess excellent low-field magnetic response sensitivity and precise angle control capabilities. They can achieve reversible and controllable bending actuation under gradient magnetic field control, providing an efficient wireless driving unit for fields such as flexible actuators, microrobots, and intelligent control devices.

[0052] Figure 10The figures show the magnetostrictive bending performance curves of the magnetic carbon nanotube helical fibers described in this invention under different structural parameters. In figure a, the smaller figure shows the relationship between the bending angle of fibers with different strand numbers and magnetic field strength when the working length is fixed at 20 mm; in figure b, the smaller figure shows the relationship between the bending angle of fibers with different working lengths and magnetic field strength when the single-strand structure is fixed. As can be seen from the figures, the fiber bending angle monotonically increases with increasing magnetic field strength and gradually approaches saturation. Furthermore, the magnetostrictive bending response sensitivity, saturation angle, and threshold magnetic field can be precisely customized by adjusting the strand number and working length. The experimental results fully demonstrate that the magnetic carbon nanotube helical fibers prepared in this invention possess excellent magnetic field controllability and structural adjustability, providing reliable support for the performance optimization and customized design of flexible magnetic actuation devices in various scenarios.

[0053] Figure 11 This invention illustrates the targeted cargo delivery process of a magnetic carbon nanotube helical fiber microrobot under magnetic field control. As shown in the figure, at time 0s, the microrobot and cargo are initially separated; after applying a gradient magnetic field, the microrobot rapidly starts and moves directionally along the channel within 0.28s; docking with the target cargo is completed at 1.25s; and the cargo is precisely pushed to the designated position at 2.14s. The entire process is rapid and smooth, requiring no wired power supply or mechanical contact, fully demonstrating the application potential of the magnetic carbon nanotube helical fiber in microrobots, minimally invasive medicine, and targeted delivery, providing an efficient and reliable technical solution for a wireless magnetically controlled micro-operating system.

[0054] Example 3 Step 1: Preparation of magnetic carbon nanotube fibers First, carbon nanotube fibers were immersed in different magnetic material precursor solutions of the same concentration (0.5 mol / L, ethanol solution of ferric chloride, ethanol solution of cobalt chloride, and aqueous solution of nickel chloride) for 15 min. Then, the fibers were annealed at 300℃ in an Ar / H2 atmosphere (flow ratio of 3:1) for 30 min. The magnetic material precursor solution with the highest saturation magnetic moment density was selected.

[0055] Step 2: Construction of the magnetic carbon nanotube fiber helical structure One end of a narrow strip of magnetic carbon nanotubes is vertically suspended from a twisting motor, while the other end is suspended with a 1.5 g load. The fibers are twisted at a certain rotation speed until a straight fiber structure is formed. With the aid of a 4.5 g load, the straight magnetic carbon nanotube fibers are wound around a graphite rod. A strong current is passed through the graphite rod under an argon atmosphere, and it is transiently heated to above 1100℃. After 2 minutes, it is shaped into a helical structure.

[0056] Example 4 Step 1: Preparation of magnetic carbon nanotube fibers First, carbon nanotube fibers were immersed in different magnetic material precursor solutions of the same concentration (2 mol / L, ethanol solution of ferric chloride, ethanol solution of cobalt chloride, and aqueous solution of nickel chloride) for 10 min. Then, the fibers were annealed at 500℃ in an Ar / H2 atmosphere (flow ratio of 1:1) for 30 min to select the magnetic material precursor solution with the highest saturation magnetic moment density.

[0057] Step 2: Construction of the magnetic carbon nanotube fiber helical structure One end of a narrow strip of magnetic carbon nanotubes is vertically suspended from a twisting motor, while the other end is suspended from a 3 g load. The fibers are twisted at a certain speed until a straight fiber structure is formed. With the help of an 18 g load, the magnetic carbon nanotube fibers are wound around a carbon rod. A strong current is passed through the carbon rod in an argon atmosphere, and the structure is fixed into a helical structure after 1 minute.

[0058] Example 5 Step 1: Preparation of magnetic carbon nanotube fibers First, carbon nanotube fibers were immersed in different magnetic material precursor solutions of the same concentration (1 mol / L, ethanol solution of ferric chloride, ethanol solution of cobalt chloride, and aqueous solution of nickel chloride) for 10 min. Then, the fibers were annealed at 450℃ in an Ar / H2 atmosphere (flow ratio of 1.5:1) for 40 min to select the magnetic material precursor solution with the highest saturation magnetic moment density.

[0059] Step 2: Construction of the magnetic carbon nanotube fiber helical structure One end of a narrow strip of magnetic carbon nanotubes is vertically suspended from a twisting motor, while the other end is suspended from a 2 g load. The fibers are twisted at a certain rotation speed until a straight fiber structure is formed. With the help of a 15 g load, the straight magnetic carbon nanotube fibers are wound around a carbon rod. A strong current is passed through the carbon rod under an argon atmosphere, and after 1.5 minutes, it is shaped into a helical structure.

[0060] Example 6 Step 1: Preparation of magnetic carbon nanotube fibers First, carbon nanotube fibers were immersed in different magnetic material precursor solutions of the same concentration (1 mol / L, ethanol solution of ferric chloride, ethanol solution of cobalt chloride, and aqueous solution of nickel chloride) for 10 min. Then, the fibers were annealed at 350℃ in an Ar / H2 atmosphere (flow ratio of 2.5:1) for 40 min to select the magnetic material precursor solution with the highest saturation magnetic moment density.

[0061] Step 2: Construction of the magnetic carbon nanotube fiber helical structure One end of a narrow strip of magnetic carbon nanotubes was vertically suspended from a twisting motor, while the other end was suspended from a 2 g load. The fibers were twisted at a certain rotation speed until a straight fiber structure was formed. With the help of a 16 g load, the straight magnetic carbon nanotube fibers were wound onto a glass carbon rod. A strong current was passed through the glass carbon rod under an argon atmosphere, and after 3 minutes, it was shaped into a helical structure.

[0062] Example 7 Step 1: Preparation of magnetic carbon nanotube fibers First, carbon nanotube fibers were immersed in different magnetic material precursor solutions of the same concentration (1 mol / L, ethanol solution of ferric chloride, ethanol solution of cobalt chloride, and aqueous solution of nickel chloride) for 10 min. Then, the fibers were annealed at 400℃ in an Ar / H2 atmosphere (flow ratio of 1:1) for 30 min to select the magnetic material precursor solution with the highest saturation magnetic moment density.

[0063] Step 2: Construction of the magnetic carbon nanotube fiber helical structure One end of a narrow strip of magnetic carbon nanotubes is vertically suspended on a twisting motor, while the other end is suspended by a 4 g load. The fibers are twisted at a certain rotation speed until a straight fiber structure is formed. With the help of a 12 g load, the straight magnetic carbon nanotube fibers are wound around a carbon fiber bundle. A strong current is passed through the carbon fiber bundle under an argon atmosphere, and after 2.5 minutes, it is shaped into a helical structure.

[0064] Example 8 Step 1: Preparation of magnetic carbon nanotube fibers First, carbon nanotube fibers were immersed in different magnetic material precursor solutions of the same concentration (1 mol / L, ethanol solution of ferric chloride, ethanol solution of cobalt chloride, and aqueous solution of nickel chloride) for 10 min. Then, the fibers were annealed at 400℃ in an Ar / H2 atmosphere (flow ratio of 1:1) for 30 min to select the magnetic material precursor solution with the highest saturation magnetic moment density.

[0065] Step 2: Construction of the magnetic carbon nanotube fiber helical structure One end of a narrow strip of magnetic carbon nanotubes is vertically suspended from a twisting motor, while the other end is suspended from a 1 g load. The fibers are twisted at a certain rotation speed until a straight fiber structure is formed. With the help of a 7 g load, the straight magnetic carbon nanotube fibers are wound around a carbon rod. A strong current is passed through the carbon rod under an argon atmosphere, and the structure is fixed into a helical structure after 2 minutes.

[0066] The properties of the magnetically responsive multidimensional deformation carbon nanotube composite fibers prepared in Examples 2-8 are similar to those in Example 1. They not only have strong mechanical and magnetic properties, but also have significantly better cycle life.

[0067] Based on the above embodiments, it is clear that the advantages of the method for preparing magnetically responsive multidimensional deformation carbon nanotube composite fibers provided by the present invention include at least the following: 1) The preparation process is mild and efficient, and fully preserves the intrinsic properties of carbon nanotubes. The magnetic precursor is loaded using an affinity wetting method, which eliminates the need for strong shear mixing and complex electrochemical equipment, avoiding the breakage of carbon nanotubes, structural damage, and disruption of the conductive network. This method enhances the magnetic properties while maintaining the mechanical strength and conductivity of the fiber.

[0068] 2) The magnetic components are uniformly loaded and firmly bonded, resulting in a highly efficient and stable magnetic response. The magnetic precursor achieves a uniform distribution of depth and bulk phase through electrostatic adsorption and pore wetting, without agglomeration or segregation, with strong interfacial bonding and uniform magnetic property distribution, enabling rapid, stable, and reversible magnetostriction even under low magnetic fields.

[0069] 3) Joule heat setting is rapid and controllable, resulting in stable structure without degradation. It achieves in-situ Joule heat setting by relying on the high conductivity of the fiber itself, and eliminates internal stress with instantaneous high temperature in a short time without damaging mechanical properties; the spiral structure is firmly set and does not loosen, and there is no obvious deformation attenuation during the cyclic driving process.

[0070] 4) The spiral structure can be precisely customized and has extremely high adaptability. By adjusting the energizing parameters and the spindle diameter, spiral structures with different spring indices can be customized as needed, flexibly adjusting the driving force, response speed, and work capacity to meet the diverse driving scenario requirements.

[0071] 5) Simple, low-cost, and scalable. The entire process involves simple equipment, mild conditions, and a short procedure. It requires no special electrolysis or large external heating equipment and can be produced continuously and in batches, combining laboratory feasibility with industrialization potential.

[0072] It should be understood that the above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing magnetically responsive multidimensional deformation carbon nanotube composite fibers, characterized in that, include: The carbon nanotube fiber precursor is subjected to ultrasonic treatment to loosen the fiber bundles in the carbon nanotube fiber precursor. The ultrasonically treated carbon nanotube fiber precursor is immersed in a solution of magnetic material precursor, allowing the magnetic material precursor to diffuse into the interior of the carbon nanotube fiber precursor, thus obtaining a magnetic carbon nanotube precursor. The magnetic carbon nanotube precursor is annealed to convert the magnetic material precursor into soft magnetic particles, thereby obtaining a pre-assembled body. The pre-assembled body is twisted to form a twisted fiber body; The twisted fiber is coiled on a columnar body to form a spiral shape, and an electric current is applied to the twisted fiber. The twisted fiber is then shaped by instantaneous Joule heat treatment to obtain a magnetically responsive multidimensional deformation carbon nanotube composite fiber. The instantaneous Joule heat treatment temperature is above 1000℃ and the duration of the current application is within 3 minutes.

2. The preparation method according to claim 1, characterized in that, The ultrasonic treatment has a power of 50-200W and a duration of 3-10 minutes.

3. The preparation method according to claim 1, characterized in that, The magnetic material precursor includes halides of iron-based elements; And / or, the solvent in the solution of the magnetic material precursor includes water and / or alcohol solvents.

4. The preparation method according to claim 3, characterized in that, The magnetic material precursor solution is an ethanol solution of cobalt chloride.

5. The preparation method according to claim 4, characterized in that, The concentration of the magnetic material precursor solution is 0.5-2 mol / L.

6. The preparation method according to claim 1, characterized in that, The impregnation time of the carbon nanotube fiber precursor shall not be less than 10 min.

7. The preparation method according to claim 1, characterized in that, The annealing atmosphere is a mixture of inert gas and hydrogen, with a volume ratio of (1-4):

1. The annealing process is performed at a temperature of 300-500℃ for 20-60 minutes.

8. The preparation method according to claim 1, characterized in that, Specifically, it includes: A first load is applied to twist the pre-assembled body to form the twisted fiber body; A second load is applied to coil the twisted fiber body around the columnar heating body, and the instantaneous Joule heat treatment is performed while maintaining the second load. The second load is 3 to 8 times the first load.

9. The magnetically responsive multidimensional deformation carbon nanotube composite fiber prepared by the preparation method according to any one of claims 1-8, characterized in that, Includes carbon nanotube fiber body and soft magnetic particles; The carbon nanotube fiber body has a twist along its length axis and a macroscopic helical shape, and the soft magnetic particles are embedded in the gaps between the fiber bundles in the carbon nanotube fiber body.

10. The application of the magnetically responsive multidimensional deformation carbon nanotube composite fiber as described in claim 9 in the field of magnetic drive.

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