A photothermal / humidity responsive fiber, its preparation method and application

Abstract

This invention relates to a photothermal / humidity-responsive fiber, its preparation method, and its applications. The fiber is a two-component side-by-side composite fiber, wherein the first component comprises a photothermal conversion filler and a hydrophobic polymer; the second component comprises a negative thermal expansion filler and a polymer, wherein the negative thermal expansion filler is zirconium tungstate nanoparticles and β-lithium nepheline nanoparticles. The fiber of this invention exhibits a dense microstructure and high orientation, displaying excellent mechanical properties and photothermal / humidity-responsive actuation performance. Twisting this fiber into yarn or weaving it into fabric can achieve diverse and multi-dimensional actuation effects. This type of smart material has enormous application prospects in information, energy, environment, medicine, wearable devices, intelligent equipment, soft robotics, and other fields.

Description

Technical Field

[0001] This invention belongs to the field of functional materials, and specifically relates to a photothermal / humidity responsive fiber, its preparation method, and its application. Background Technology

[0002] Smart responsive materials can sense environmental changes and various environmental stimuli (such as light, heat, electricity, magnetism, humidity, pH, chemical vapor, etc.) and actively provide feedback on physical or chemical properties. Flexible actuators represent a class of smart materials that can actively respond to environmental stimuli and undergo reversible deformation. They typically possess good flexibility, adaptability, and motion continuity, and have important applications in soft robotics, wearable devices, and intelligent deformable equipment.

[0003] Photothermal / humidity-responsive actuators possess advantages such as wide energy sources, fast response speed, and high designability, making them a class of actuators with significant application prospects. Currently, photothermal / humidity-responsive actuators are mostly bilayer film structures with thermal / humidity expansion differences or one-dimensional, two-dimensional, or three-dimensional structural materials prepared from shape memory materials (liquid crystal elastomers, polyurethanes, gels, alloys, etc.). Among them, fiber actuators offer high degrees of freedom and good adaptability, enabling them to perform expansion, contraction, or bending deformation in complex environments such as narrow and tortuous spaces. Combined with weaving technology, they can realize intelligent deformable materials with diverse structures and rich functions, showing significant potential in fields such as health monitoring, motion assistance, and medical rehabilitation.

[0004] Currently reported photothermal / humidity responsive fibers are mainly divided into two categories: (1) shape memory material fibers (such as liquid crystal elastomers, shape memory polyurethanes, etc.), whose actuation mechanism is thermal phase change / humidity-induced dynamic bond recombination; (2) or bicomponent parallel composite fibers, whose actuation mechanism is asymmetric thermal / humidity expansion. Bicomponent composite fibers have advantages such as wide material selection, convenient processing, and low production cost, and have great advantages in industrialization and commercialization. However, there are very few reports on such fibers, especially since they cannot simultaneously possess high tensile strength, high interfacial adhesion, large bending deformation, and fast response speed. Therefore, developing a photothermal / humidity responsive fiber with high strength, fast response, and large deformation is of great significance to promoting the development and application of such materials. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a photothermal / humidity responsive fiber, its preparation method and application, which overcomes the technical defects of existing fibers that cannot simultaneously possess high breaking strength, large bending deformation and stable responsiveness. At the same time, the present invention can also be combined with weaving, knitting or three-dimensional weaving and other technologies to design smart responsive fabrics, thus broadening the application field of fiber / fabric-based smart responsive materials.

[0006] This invention provides a photothermal / humidity responsive fiber, wherein the fiber is a two-component side-by-side composite fiber, wherein the first component includes a photothermal conversion filler and a hydrophobic polymer; and the second component includes a negative thermal expansion filler and a polymer.

[0007] The negative thermal expansion fillers are zirconium tungstate nanoparticles and β-lithium nepheline nanoparticles.

[0008] The method for preparing the photothermal / humidity responsive fiber includes:

[0009] (1) The photothermal conversion filler, hydrophobic polymer and solvent are mixed to obtain the first spinning solution;

[0010] (2) Mix the negative thermal expansion filler, polymer, and solvent to obtain the second spinning solution;

[0011] (3) The first and second spinning solutions are simultaneously extruded into the coagulation bath and thermally stretched to obtain light-heat / moisture responsive fibers by using parallel spinning technology.

[0012] The photothermal / humidity responsive fiber is an asymmetric photothermal / humidity responsive fiber.

[0013] The two components of the bicomponent parallel composite fiber have asymmetric photothermal / moisture expansion properties, and can undergo reversible bending actuation behavior under near-infrared light irradiation / moisture stimulation.

[0014] In the first component, the photothermal conversion filler is uniformly distributed in the hydrophobic polymer.

[0015] In the second component, the negative thermal expansion filler is arranged in a highly oriented manner along the radial direction of the fiber. Through the spatial steric hindrance effect and the regulation of the micro-stress field, the thermal expansion coefficient of the inert component is reduced, giving the fiber anisotropic thermal expansion properties, increasing the thermal expansion difference between the two components, and significantly improving the fiber's response speed and driving angle.

[0016] Preferably, the photothermal conversion filler includes one or more of the following: carbon black, carbon nanotubes, graphene, gold nanoparticles, silver nanoparticles, copper nanoparticles, platinum nanoparticles, gold nanowires, silver nanowires, copper nanowires, platinum nanowires, copper oxide nanoparticles, cobalt oxide nanoparticles, nickel oxide nanoparticles, zinc oxide nanoparticles, iron oxide nanoparticles, iron tetroxide nanoparticles, titanium dioxide nanoparticles, copper sulfide nanoparticles, molybdenum disulfide nanoparticles, paraffin wax, transition metal carbides MXene, lignin, polydopamine, polypyrrole, polyaniline, and their derivatives.

[0017] Furthermore, the photothermal conversion filler is one or more of the following: carbon nanotubes, transition metal carbides MXene, graphene, silver nanoparticles, iron tetroxide nanoparticles, titanium dioxide nanoparticles, molybdenum disulfide nanoparticles, polydopamine, polypyrrole and their derivatives.

[0018] Preferably, the hydrophobic polymer in the first component includes one or more of polydimethylsiloxane, polyurethane, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polycarbonate, polyethylene, polypropylene, polystyrene, polyvinyl chloride, and their modified forms.

[0019] Furthermore, the hydrophobic polymer in the first component is one or more of polydimethylsiloxane, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polypropylene, polystyrene, and their modified forms.

[0020] Preferably, the photothermal conversion filler in the first component is 0.1 wt%–50 wt% of the hydrophobic polymer.

[0021] More preferably, the photothermal conversion filler in the first component is 0.1 wt%–20 wt% of the hydrophobic polymer.

[0022] Preferably, the mass ratio of the negative thermal expansion filler zirconium tungstate nanoparticles to β-lithium nepheline nanoparticles is 1:10–10:1.

[0023] Preferably, the polymer in the second component is a hydrophilic polymer, a hydrophobic polymer, or a mixture of hydrophilic and hydrophobic polymers.

[0024] More preferably, the polymer in the second component is a mixture of hydrophilic and hydrophobic polymers, wherein the mass ratio of the hydrophilic polymer to the hydrophobic polymer is 1 to 10:1.

[0025] Preferably, the negative thermal expansion filler in the second component is 0.1 wt%–50 wt% of the polymer mass.

[0026] More preferably, the negative thermal expansion filler in the second component is 10 wt%–30 wt% of the polymer mass.

[0027] Preferably, the hydrophilic polymer includes one or more of epoxy resin, polyimide, polyacrylonitrile, lignocellulose, cotton cellulose, ethylcellulose, nitrocellulose, cellulose acetate, sodium alginate, polymethyl methacrylate, chitosan, and gelatin; the hydrophobic polymer includes one or more of polydimethylsiloxane, polyurethane, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polycarbonate, polyethylene, polypropylene, polystyrene, and polyvinyl chloride.

[0028] The hydrophobic polymers in the first combination and the second component are the same.

[0029] Preferably, the mass ratio of the first component to the second component is 1:10 to 10:1, and more preferably, the mass ratio is 1:3 to 3:1.

[0030] The cross-section of the photothermal / humidity responsive fiber is circular.

[0031] The photothermal / humidity responsive fiber has a diameter of 0.1–1 mm, and more specifically, a diameter of 0.2–0.4 mm.

[0032] The thermal expansion properties of the first component are better than those of the second component.

[0033] The present invention provides a textile comprising yarns or fabrics of the photothermal / moisture responsive fibers.

[0034] This invention provides a method for preparing any of the aforementioned photothermal / humidity-responsive fibers, comprising:

[0035] Step (1) Mix the photothermal conversion filler, hydrophobic polymer, and solvent to obtain the first spinning solution;

[0036] Step (2) Mix the negative thermal expansion filler, polymer, and solvent to obtain the second spinning solution;

[0037] Step (3) uses parallel spinning technology to simultaneously extrude the first spinning solution and the second spinning solution into the coagulation bath and thermally stretch them to obtain photothermal / humidity responsive fibers.

[0038] The preferred embodiment of the above preparation method is as follows:

[0039] In step (1), the concentration of the hydrophobic polymer in the first spinning solution is 1 wt%–50 wt%; the photothermal conversion filler is 0.1 wt%–50 wt% of the hydrophobic polymer.

[0040] Furthermore, the photothermal conversion filler is 0.1 wt%–20 wt% of a hydrophobic polymer.

[0041] In step (2), the concentration of polymer in the second spinning solution is 1 wt%–50 wt%, and the negative thermal expansion filler is 0.1 wt%–50 wt% of the polymer.

[0042] Furthermore, the negative thermal expansion filler is 10 wt%–30 wt% of the polymer.

[0043] After mixing in step (1), the mixture is stirred at a temperature of 20–80 °C for 1–24 h.

[0044] In step (2), the mixture is stirred after mixing, with a stirring temperature of 20–80 ℃ and a stirring time of 1–24 h.

[0045] The solvents used in steps (1) and (2) include one or more of the following: deionized water, ethanol, N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, formic acid, acetic acid, toluene, xylene, dichloromethane, chloroform, cyclohexane, acetone, nitric acid, ethyl carbonate, sodium thiocyanate, and zinc chloride.

[0046] The solvent used in steps (1) and (2) is the same.

[0047] Step (2) also includes a co-solvent; wherein the co-solvent is lithium chloride.

[0048] The coagulation bath in step (3) includes one or more of the following: deionized water, methanol, ethanol, isopropanol, glycerol, N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, toluene, chloroform, cyclohexane, acetone, butanone, formic acid, acetic acid, sodium chloride, calcium chloride, phosphate buffer solution, sodium dihydrogen phosphate, hydrochloric acid, sulfuric acid, sodium sulfate, and zinc sulfate.

[0049] Furthermore, the coagulation bath is one or more of deionized water, ethanol, calcium chloride, N,N-dimethylformamide, dimethylacetamide, and dimethyl sulfoxide.

[0050] In step (3), the extrusion rate of the first spinning solution is 0.1–10 ml / min; the extrusion rate of the second spinning solution is 0.1–10 ml / min.

[0051] In step (3), the hot stretching temperature is 50–100 ℃ and the stretching ratio is 1:1–1:2.

[0052] Step (3) After hot stretching, wash and then heat set at 100–160 °C.

[0053] This invention provides an application of any of the aforementioned photothermal / humidity responsive fibers or textiles in the fields of information, energy, environment, medical, wearable devices, smart equipment, and soft robotics.

[0054] Preferably, the applications in the information field include autonomous sensing, information collection, sensing, information transmission, and information encryption.

[0055] Preferably, the energy applications include energy conversion, energy harvesting, energy storage, and energy release.

[0056] Preferably, the applications in the environmental field include environmental exploration, ecological monitoring, pollution control, and disaster response.

[0057] Preferably, the applications in the medical field include examination and diagnosis, surgical treatment, rehabilitation exoskeletons, and bionic prostheses.

[0058] Preferably, the applications in the field of wearable devices include health monitoring, assisted exercise, smart clothing, and electronic skin.

[0059] Preferably, the applications in the field of intelligent equipment include intelligent testing equipment, intelligent maintenance equipment, and bionic robotic arms.

[0060] Preferably, the applications in the field of soft robotics include artificial muscles, human-computer interaction, adaptive motion, and disaster relief.

[0061] In particular, the fiber material of the present invention is a parallel composite fiber that exhibits bending actuation behavior under infrared light irradiation. Based on the difference in thermal expansion properties between the two components of the parallel structure, the photothermal conversion material converts light energy into heat energy, and then utilizes asymmetric thermal expansion to convert it into mechanical energy, which macroscopically manifests as the bending deformation of the fiber.

[0062] Beneficial effects

[0063] (1) Under photothermal conditions, the anisotropic negative thermal expansion filler β-lithium nepheline nanoparticles form a shrinkage stress field along the radial direction of the fiber, which works synergistically with the local micro-stress field formed by the isotropic negative thermal expansion filler zirconium tungstate nanoparticles. The shrinkage stress is transferred to the thermally moving molecular chain through the hydrogen bond network, which inhibits the thermal expansion of the polymer, thereby improving the photothermal driving speed and maximum bending angle of the parallel fibers.

[0064] (2) This invention can prepare photothermal / humidity responsive fibers with different component mass ratios by controlling the composition / concentration of spinning solution and spinning parameters, thereby achieving precise control of fiber driving speed, recovery speed, maximum deformation and differentiated driving effect under photothermal / humidity stimulation.

[0065] (3) The present invention prepares highly oriented fibers by hot stretching strategy, and its breaking strength is more than 7 times higher than that of non-hot stretched fibers; and the structure of hot stretched fibers is dense and flexible, so the response speed and maximum bending angle are significantly improved. By precisely controlling the hot stretching strain ratio, the problem of incompatibility between high breaking strength, fast response rate and large bending deformation of parallel fiber actuators is overcome.

[0066] (4) The present invention adopts a polymer blending strategy, which introduces a small amount of polymer material of another component into one component, aiming to promote the forming of parallel fibers and optimize the interfacial adhesion between the two components. This strategy not only gives the fiber actuator excellent cycle stability, but also provides mechanical protection for subsequent hot stretching treatment.

[0067] (5) This invention provides a method for preparing photothermal / wet responsive fibers. This method mainly adopts parallel wet spinning and hot stretching technology, which is applicable to a variety of polymer materials and fillers and has a certain degree of universality. This method can precisely control the structure and properties of the fibers. The process is mature and automated, and has the potential for large-scale production. The fibers prepared by the method of this invention can be twisted into yarns and woven into fabrics. The fiber / fabric-based actuators obtained have extremely important applications in the fields of information, energy, environment, medical and intelligent equipment. Attached Figure Description

[0068] Figure 1 This is a macroscopic rendering of the polyvinylidene fluoride / lignocellulose composite fiber from Example 1.

[0069] Figure 2 This is a tensile fracture diagram of the polyvinylidene fluoride / lignocellulose composite fiber from Example 1;

[0070] Figure 3 This is a scanning electron microscope image of the polyvinylidene fluoride / lignocellulose composite fiber from Example 1;

[0071] Figure 4 This is the continuous bending actuation behavior of polyvinylidene fluoride / lignocellulose composite fibers under infrared light irradiation as described in Example 1.

[0072] Figure 5 This is the continuous bending actuation behavior of polyvinylidene fluoride / lignocellulose composite fibers under moisture stimulation as described in Example 1.

[0073] Figure 6 This is the maximum bending of the polyvinylidene fluoride / lignocellulose composite fiber under infrared light irradiation in Example 1;

[0074] Figure 7 This is the maximum bending of the polyvinylidene fluoride composite fiber under infrared light irradiation in Example 2;

[0075] Figure 8 This is the maximum bending of the polyvinylidene fluoride / lignocellulose composite fiber under infrared light irradiation in Example 3;

[0076] Figure 9 The maximum bending of the polyvinylidene fluoride / lignocellulose composite fiber in Comparative Example 1 under infrared light irradiation;

[0077] Figure 10 The maximum bending of the polyvinylidene fluoride / lignocellulose composite fiber in Comparative Example 2 under infrared light irradiation;

[0078] Figure 11 It is the woven fabric made of polyvinylidene fluoride / lignocellulose composite fiber as described in Example 1;

[0079] Figure 12This is a side view of the maximum bending of the polyvinylidene fluoride / lignocellulose composite fiber fabric in Example 1 under infrared light irradiation. Detailed Implementation

[0080] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0081] The main reagents involved in this invention are all of analytical grade and can be used directly.

[0082] Polyvinylidene fluoride (PVDF, Mw=400000, Yuanye); N,N-dimethylformamide (DMF, AR, Aladdin); dimethylacetamide (DMAc, AR, Bide Pharmaceuticals); lignocellulose (MCC, RG, Titan); carbon nanotubes (CNT, RG, Titan); zirconium tungstate nanoparticles (ZrW2O8, RG, Huawi Ruike); anhydrous lithium chloride (LiCl, AR, Aladdin); β-nepheline nanoparticles (Li2Al2Si2O8, RG, Yuxiling).

[0083] Methods for testing the tensile properties of photothermal / humidity responsive fibers:

[0084] According to GB / T 14337-2022, the tensile rate is 20 mm / min.

[0085] Photothermal and wet drive performance testing:

[0086] The sample length was 5 cm, and the test environment was a sealed acrylic box. The photothermal stimulation source was an infrared lamp with a power of 250 W, which was placed 20 cm away from the sample and the test duration was 2 minutes. The humidity stimulation was provided by a humidifier, and the humidity inside the box was monitored in real time by a humidity sensor. The test humidity was controlled within the range of 30%–90%. The fiber deformation effect during the test was recorded by a high-definition camera.

[0087] Bending angle: Define vertical upward as 0°, draw a tangent at the free end of the fiber, and record the angle between the tangent and the vertical direction as the driving deformation angle.

[0088] Response stability determination method:

[0089] After 50 cycles of cyclic driving, compare the results with those before the cyclic test to see if the difference in the maximum deformation angle is within 5% of the initial maximum deformation angle.

[0090] Methods for determining interfacial adhesion:

[0091] Visually inspect the two components of the photothermal / humidity-responsive fiber to check for stratification.

[0092] Example 1

[0093] In this embodiment, a photothermal / humidity-responsive fiber is provided, and the preparation method is as follows:

[0094] Spinning solution A: A spinning solution with a mass fraction of 20 wt% was prepared by dissolving polyvinylidene fluoride in dimethylacetamide. Carbon nanotubes were weighed and added to the spinning solution as photothermal conversion fillers, wherein the mass ratio of carbon nanotubes to polyvinylidene fluoride was 1:25. The solution was stirred at 60 °C for 12 hours.

[0095] Spinning solution B: Weigh an appropriate amount of lignocellulose and lithium chloride and add them to dimethylacetamide. The mass fraction of lignocellulose and lithium chloride is 8 wt%. Then add 2 wt% polyvinylidene fluoride and stir. After mixing thoroughly, add 10 wt% (relative to the mass of lignocellulose and polyvinylidene fluoride) of zirconium tungstate nanoparticles and 10 wt% (relative to the mass of lignocellulose and polyvinylidene fluoride) of β-lithium nepheline nanoparticles in sequence. Continue stirring until uniform in preparation for subsequent spinning.

[0096] Spinning solutions A and B were both extruded into a 50 °C dimethylacetamide / deionized water (volume ratio 7:13) coagulation bath at a rate of 1 mL / min. The fibers were then hot-stretched in 80 °C deionized water at a stretch ratio of 1:1.3. After washing in methanol solvent to remove impurities, the fibers were finally heat-set at 150 °C to obtain polyvinylidene fluoride / lignocellulose composite fibers.

[0097] Macroscopic rendering of polyvinylidene fluoride / lignocellulose composite fiber as shown below Figure 1 As shown; tensile fracture diagram as shown. Figure 2 As shown; Scanning electron micrograph of polyvinylidene fluoride / lignocellulose composite fiber is shown below. Figure 3 As shown; the continuous bending actuation behavior generated under infrared light irradiation is as follows: Figure 4 As shown; the continuous bending actuation behavior generated under moisture stimulation is as follows: Figure 5 As shown.

[0098] The polyvinylidene fluoride / lignocellulose composite fiber has a diameter of approximately 0.25 mm, a bicomponent mass ratio of 1:1, and a tensile strength as high as 75.2 MPa. It exhibits significant bending-driven behavior under infrared irradiation, such as... Figure 6 As shown, the fiber reaches its maximum bending angle of 90° at 56 seconds and recovers to its initial state within 120 seconds under moisture stimulation. This composite fiber exhibits excellent photothermal / moisture response stability, with no change in drive amplitude after 50 cycles.

[0099] The fiber meets the requirements for machine operation. The fiber is the warp yarn, and the polyester yarn is the weft yarn. The actuators for the plain and twill fabrics woven from it are as follows: Figure 11 and Figure 12 As shown, the designed fabric actuator can also produce significant reversible bending deformation under infrared light irradiation / moisture stimulation.

[0100] Example 2

[0101] In this embodiment, a photothermal / humidity-responsive fiber is provided, and the preparation method is as follows:

[0102] Spinning solution A: A 20 wt% spinning solution was prepared by dissolving polyvinylidene fluoride in dimethylacetamide. Carbon nanotubes were weighed and added to the spinning solution as photothermal conversion fillers, wherein the mass ratio of carbon nanotubes to polyvinylidene fluoride was 1:25. The solution was stirred at 60 °C for 12 hours.

[0103] Spinning solution B: Weigh 20 wt% of polyvinylidene fluoride and dissolve it in dimethylacetamide. After mixing thoroughly, add 10 wt% (relative to polyvinylidene fluoride) of zirconium tungstate nanoparticles and 10 wt% (relative to polyvinylidene fluoride) of β-lithium nepheline nanoparticles in sequence, and continue stirring until homogeneous in preparation for subsequent spinning.

[0104] Spinning solutions A and B were both extruded into a 50 °C N,N-dimethylacetamide / deionized water (volume ratio 7:13) coagulation bath at a rate of 1 mL / min. The fibers were then hot-stretched in deionized water at 80 °C at a stretch ratio of 1:1.3. After washing in methanol solvent to remove impurities, the fibers were finally heat-set at 150 °C to obtain polyvinylidene fluoride composite fibers.

[0105] The polyvinylidene fluoride composite fiber has a diameter of approximately 0.25 mm, a bicomponent mass ratio of 1:1, and a tensile strength of 40.9 MPa. Under infrared irradiation, it exhibits significant bending-driven behavior, such as... Figure 7 As shown, the fiber reaches its maximum bending angle of 15° at 10 seconds; the fiber exhibits no significant driving behavior under moisture stimulation. This composite fiber demonstrates excellent photothermal response stability, with no change in driving amplitude after 50 cycles.

[0106] Example 3

[0107] In this embodiment, a photothermal / humidity-responsive fiber is provided, and the preparation method is as follows:

[0108] Spinning solution A: A spinning solution with a mass fraction of 20 wt% was prepared by dissolving polyvinylidene fluoride in dimethylacetamide. Carbon nanotubes were weighed and added to the spinning solution as photothermal conversion fillers, wherein the mass ratio of carbon nanotubes to polyvinylidene fluoride was 1:25. The solution was stirred at 60 °C for 12 hours.

[0109] Spinning solution B: Weigh lignocellulose and lithium chloride and add them to dimethylacetamide. The mass fraction of lignocellulose and lithium chloride is 8 wt%. Then add 2 wt% polyvinylidene fluoride and stir. After mixing thoroughly, add 10 wt% (relative to the mass of lignocellulose and polyvinylidene fluoride) of zirconium tungstate nanoparticles and 10 wt% (relative to the mass of lignocellulose and polyvinylidene fluoride) of β-lithium nepheline nanoparticles in sequence. Continue stirring until homogeneous in preparation for subsequent spinning.

[0110] Spinning solutions A and B were both extruded into a 50 °C dimethylacetamide / deionized water (volume ratio 7:13) coagulation bath at a rate of 1 mL / min. After the fibers were formed, they were taken out and dried in an oven at 30 °C for 24 hours to obtain polyvinylidene fluoride / wood cellulose composite fibers.

[0111] The polyvinylidene fluoride / lignocellulose composite fiber has a diameter of approximately 0.25 mm, a bicomponent mass ratio of 1:1, and a tensile strength of up to 62.7 MPa. It exhibits significant bending-driven behavior under infrared irradiation, such as... Figure 8 As shown, the fiber reaches its maximum bending angle of 18° at 3 seconds; under moisture stimulation, it recovers to its initial state within 39 seconds. Furthermore, the composite fiber exhibits excellent photothermal / humidity response stability, with no change in the driving amplitude after 50 cycles.

[0112] Comparative Example 1

[0113] In this embodiment, a photothermal / humidity-responsive fiber is provided, and the preparation method is as follows:

[0114] Spinning solution A: A spinning solution with a mass fraction of 20 wt% was prepared by dissolving polyvinylidene fluoride in dimethylacetamide. Carbon nanotubes were weighed and added to the spinning solution as photothermal conversion fillers, wherein the mass ratio of carbon nanotubes to polyvinylidene fluoride was 1:25. The solution was stirred at 60 °C for 12 hours.

[0115] Spinning solution B: Weigh an appropriate amount of lignocellulose and lithium chloride and add them to dimethylacetamide. The mass fraction of lignocellulose and lithium chloride is 8 wt%. Then add 2 wt% polyvinylidene fluoride and stir. After mixing thoroughly, add 20 wt% (relative to the mass of lignocellulose and polyvinylidene fluoride) of zirconium tungstate nanoparticles and continue stirring until uniform in preparation for subsequent spinning.

[0116] Spinning solutions A and B were both extruded into a 50 °C N,N-dimethylformamide / deionized water (volume ratio 7:13) coagulation bath at a rate of 1 mL / min, and then hot-stretched in 80 °C deionized water at a stretch ratio of 1:1.3. After washing in methanol solvent to remove impurities, the fibers were finally heat-set at 150 °C to obtain polyvinylidene fluoride / lignocellulose composite fibers.

[0117] The polyvinylidene fluoride / lignocellulose composite fiber has a diameter of approximately 0.25 mm, a bicomponent mass ratio of 1:1, and a tensile strength of up to 60.1 MPa. It exhibits significant bending-driven behavior under infrared irradiation, such as... Figure 9 As shown, the fiber reaches its maximum bending angle of 51° at 69 seconds; under moisture stimulation, it recovers to its initial state within 103 seconds. Furthermore, the composite fiber exhibits excellent photothermal / humidity response stability, with no change in the driving amplitude after 50 cycles.

[0118] Comparative Example 2

[0119] In this embodiment, a photothermal / humidity-responsive fiber is provided, and the preparation method is as follows:

[0120] Spinning solution A: A spinning solution with a mass fraction of 20 wt% was prepared by dissolving polyvinylidene fluoride in dimethylacetamide. Carbon nanotubes were weighed and added to the spinning solution as photothermal conversion fillers, wherein the mass ratio of carbon nanotubes to polyvinylidene fluoride was 1:25. The solution was stirred at 60 °C for 12 hours.

[0121] Spinning solution B: Weigh an appropriate amount of lignocellulose and lithium chloride and add them to dimethylacetamide. The mass fraction of lignocellulose and lithium chloride is 8 wt%. Then add 2 wt% polyvinylidene fluoride and stir. After mixing thoroughly, add 20 wt% (relative to the mass of lignocellulose and polyvinylidene fluoride) of β-lithium nepheline nanoparticles and continue stirring until uniform in preparation for subsequent spinning.

[0122] Spinning solutions A and B were both extruded into a 50 °C N,N-dimethylformamide / deionized water (volume ratio 7:13) coagulation bath at a rate of 1 mL / min, and then hot-stretched in 80 °C deionized water at a stretch ratio of 1:1.3. After washing in methanol solvent to remove impurities, the fibers were finally heat-set at 150 °C to obtain polyvinylidene fluoride / lignocellulose composite fibers.

[0123] The polyvinylidene fluoride / lignocellulose composite fiber has a diameter of approximately 0.25 mm, a bicomponent mass ratio of 1:1, and a tensile strength of up to 81.4 MPa. It exhibits significant bending-driven behavior under infrared irradiation, such as... Figure 10 As shown, the fiber reaches its maximum bending angle of 60° at 77 seconds; under moisture stimulation, it recovers to its initial state within 112 seconds. The second component of this fiber contains only β-lithium nepheline nanoparticles. Without the synergistic effect of zirconium tungstate nanoparticles and β-lithium nepheline nanoparticles, the photothermal / humidity response deformation rate and maximum deformation angle of this fiber are smaller than those of the fiber described in Example 1. Furthermore, this composite fiber exhibits excellent photothermal / humidity response stability, with no change in the driving amplitude after 50 cycles.

[0124] Compared to Comparative Example 1 and Examples 1 and 2, the second component of the polyvinylidene fluoride / lignocellulose composite fiber in Comparative Example 1 only contained zirconium tungstate nanoparticles, while the second component of the polyvinylidene fluoride / lignocellulose composite fiber in Comparative Example 2 only contained β-lithium nepheline nanoparticles. Consequently, the photothermal deformation rate and maximum deformation angle of the composite fibers in Comparative Example 1 and Comparative Example 2 were both lower than those in Example 1. This invention improves the photothermal driving speed and maximum bending angle of the composite fiber through the synergistic effect of zirconium tungstate nanoparticles and β-lithium nepheline nanoparticles.

Claims

1. A photothermal / humidity responsive fiber, characterized in that, The fiber is a two-component parallel composite fiber, wherein the first component includes a photothermal conversion filler and a hydrophobic polymer; and the second component includes a negative thermal expansion filler and a polymer. The negative thermal expansion fillers are zirconium tungstate nanoparticles and β-lithium nepheline nanoparticles. The photothermal conversion filler comprises one or more of the following: carbon black, carbon nanotubes, graphene, gold nanoparticles, silver nanoparticles, copper nanoparticles, platinum nanoparticles, gold nanowires, silver nanowires, copper nanowires, platinum nanowires, copper oxide nanoparticles, cobalt oxide nanoparticles, nickel oxide nanoparticles, zinc oxide nanoparticles, iron oxide nanoparticles, iron tetroxide nanoparticles, titanium dioxide nanoparticles, copper sulfide nanoparticles, molybdenum disulfide nanoparticles, paraffin wax, transition metal carbides (MXene), lignin, polydopamine, polypyrrole, and polyaniline; the hydrophobic polymer in the first component comprises one or more of the following: polydimethylsiloxane, polyurethane, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polycarbonate, polyethylene, polypropylene, polystyrene, and polyvinyl chloride. The polymer in the second component is a hydrophilic polymer, a hydrophobic polymer, or a mixture of hydrophilic and hydrophobic polymers; the hydrophilic polymer includes one or more of lignocellulose, cotton cellulose, cellulose acetate, sodium alginate, chitosan, and gelatin; the hydrophobic polymer includes one or more of polydimethylsiloxane, polyurethane, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polycarbonate, polyethylene, polypropylene, polystyrene, and polyvinyl chloride. The method for preparing the photothermal / humidity responsive fiber includes: (1) The photothermal conversion filler, hydrophobic polymer and solvent are mixed to obtain the first spinning solution; (2) Mix the negative thermal expansion filler, polymer, and solvent to obtain the second spinning solution; (3) The first and second spinning solutions are simultaneously extruded into the coagulation bath and thermally stretched to obtain light-heat / moisture responsive fibers by using parallel spinning technology.

2. The photothermal / humidity responsive fiber according to claim 1, characterized in that, The photothermal conversion filler in the first component is 0.1 wt%–50 wt% of the hydrophobic polymer.

3. The photothermal / humidity responsive fiber according to claim 1, characterized in that, The negative thermal expansion filler in the second component is 0.1 wt%–50 wt% of the polymer mass.

4. The photothermal / humidity responsive fiber according to claim 1, characterized in that, The mass ratio of the first component to the second component is 1:10 to 10:1; The cross-section of the photothermal / humidity responsive fiber is circular; The diameter of the photothermal / humidity responsive fiber is 0.1–1 mm.

5. A textile product, characterized in that, The textile includes yarns or fabrics of the photothermal / moisture-responsive fibers of claim 1.

6. A method for preparing the photothermal / humidity responsive fiber according to any one of claims 1–4, characterized in that, include: Step (1) Mix the photothermal conversion filler, hydrophobic polymer, and solvent to obtain the first spinning solution; Step (2) Mix the negative thermal expansion filler, polymer, and solvent to obtain the second spinning solution; Step (3) uses parallel spinning technology to simultaneously extrude the first spinning solution and the second spinning solution into the coagulation bath and thermally stretch them to obtain photothermal / humidity responsive fibers.

7. The preparation method according to claim 6, characterized in that, In step (1), the concentration of the hydrophobic polymer in the first spinning solution is 1 wt%–50 wt%; the photothermal conversion filler is 0.1 wt%–50 wt% of the hydrophobic polymer. In step (2), the concentration of polymer in the second spinning solution is 1 wt%–50 wt%, and the negative thermal expansion filler is 0.1 wt%–50 wt% of the polymer. The solvents used in steps (1) and (2) include one or more of the following: deionized water, ethanol, N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, formic acid, acetic acid, toluene, xylene, dichloromethane, chloroform, cyclohexane, acetone, nitric acid, ethyl carbonate, sodium thiocyanate, and zinc chloride.

8. The preparation method according to claim 6, characterized in that, The coagulation bath in step (3) includes one or more of the following: deionized water, methanol, ethanol, isopropanol, glycerol, N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, toluene, chloroform, cyclohexane, acetone, butanone, formic acid, acetic acid, sodium chloride, calcium chloride, phosphate buffer solution, sodium dihydrogen phosphate, hydrochloric acid, sulfuric acid, sodium sulfate, and zinc sulfate. In step (3), the extrusion rate of the first spinning solution is 0.1–10 ml / min; the extrusion rate of the second spinning solution is 0.1–10 ml / min. In step (3), the hot stretching temperature is 50–100 ℃ and the stretching ratio is 1:1–1:2; Step (3) After hot stretching, wash and then heat set at 100–160 °C.

9. The application of any of the photothermal / humidity responsive fibers of claims 1–4 or the textile of claim 5 in the fields of information, energy, environment, medical, wearable devices, smart equipment, and soft robotics.

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