Photo-thermal / moisture response fiber as well as preparation method and application thereof

Abstract

The invention relates to a photo-thermal / moisture response fiber and a preparation method and application thereof, the fiber is a two-component parallel type composite fiber, and a first component comprises a photo-thermal 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 beta-eucryptite nanoparticles. The fiber microstructure is compact, the orientation degree is high, excellent mechanical performance and photo-thermal / wet response driving performance are shown, the fiber is twisted into yarn or woven into fabric, and the diversified and multi-dimensional actuating effect can be achieved. The intelligent material has huge application prospects in the fields of information, energy, environment, medical treatment, wearable equipment, intelligent equipment, soft robots and the like.

Description

Technical Field

[0001] The present invention belongs to the field of functional materials, and in particular relates to a light-heat-humidity responsive fiber and a preparation method and application thereof. Background Art

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

[0003] Photothermal / hygro-responsive actuators offer significant application prospects due to their wide range of energy sources, fast response speed, and high designability. Currently, most photothermal / hygro-responsive actuators are constructed using double-layer membranes with differential thermal / hygroscopic expansion or one-, two-, or three-dimensional structures made from shape memory materials (such as liquid crystal elastomers, polyurethanes, gels, and alloys). Fiber actuators offer high degrees of freedom and adaptability, enabling them to achieve expansion and contraction or bending deformations in complex environments, such as narrow and tortuous environments. Combined with weaving technology, they can create intelligent deformable materials with diverse structures and rich functions, showing significant potential in areas such as health monitoring, sports assistance, and medical rehabilitation.

[0004] Currently reported photothermal / hygroscopic fibers are mainly divided into two categories: (1) shape memory material (such as liquid crystal elastomer, shape memory polyurethane, etc.) fibers, whose actuation mechanism is thermal phase change / hygroscopic dynamic bond reorganization; (2) or bicomponent parallel composite fibers, whose actuation mechanism is asymmetric thermal / hygroscopic expansion. Bicomponent composite fibers have the advantages of 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 those that cannot combine high breaking strength, high interfacial adhesion, large bending deformation and fast response speed. Therefore, the development of a photothermal / hygroscopic fiber with high strength, fast response and large deformation is of great significance to promote 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 and its preparation method and application, so as to overcome the technical defects of existing fibers that cannot have high breaking strength, large bending deformation and stable responsiveness. At the same time, the present invention can also be designed into smart responsive fabrics in combination with weaving, knitting or three-dimensional weaving technologies, thereby broadening the application field of fiber / fabric-based smart responsive materials.

[0006] The present invention provides a photothermal / moisture responsive fiber, which is a two-component parallel composite fiber, wherein the first component includes a photothermal conversion filler and a hydrophobic polymer; the second component includes a negative thermal expansion filler and a polymer;

[0007] The negative thermal expansion fillers are zirconium tungstate nanoparticles and β-eucryptite nanoparticles;

[0008] The preparation method of the photothermal / humidity responsive fiber comprises:

[0009] (1) mixing a photothermal conversion filler, a hydrophobic polymer, and a solvent to obtain a first spinning solution;

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

[0011] (3) The first spinning solution and the second spinning solution are squeezed into the coagulation bath at the same time by parallel spinning technology, and then thermally stretched to obtain photothermal / moisture responsive fibers.

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

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

[0014] The light-to-heat conversion filler in the first component is uniformly distributed in the hydrophobic polymer.

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

[0016] Preferably, the photothermal conversion filler includes one or more of 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, ferroferric oxide nanoparticles, titanium dioxide nanoparticles, copper sulfide nanoparticles, molybdenum disulfide nanoparticles, paraffin, transition metal carbide MXene, lignin, polydopamine, polypyrrole, polyaniline and their derivatives.

[0017] Furthermore, the photothermal conversion filler is one or more of carbon nanotubes, transition metal carbide MXene, graphene, silver nanoparticles, ferroferric oxide 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 modifications thereof.

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

[0020] Preferably, the light-to-heat conversion filler in the first component is 0.1 wt%-50 wt% of the mass of the hydrophobic polymer.

[0021] Further preferably, the light-to-heat conversion filler in the first component is 0.1 wt%-20 wt% of the mass of the hydrophobic polymer.

[0022] Preferably, the mass ratio of the negative thermal expansion filler zirconium tungstate nanoparticles to the β-eucryptite 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 a hydrophilic polymer and a hydrophobic polymer.

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

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

[0026] Further 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, wood cellulose, cotton cellulose, ethyl cellulose, cellulose nitrate, 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 and second components are the same.

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

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

[0031] The photothermal / moisture responsive fiber has a diameter of 0.1-1 mm, and further has a diameter of 0.2-0.4 mm.

[0032] The first component has better thermal expansion properties than the second component.

[0033] The present invention provides a textile comprising yarn or fabric of the light-heat / moisture-responsive fiber.

[0034] The present invention provides a method for preparing any of the above-mentioned photothermal / humidity responsive fibers, comprising:

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

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

[0037] In step (3), the first spinning solution and the second spinning solution are squeezed into a coagulation bath at the same time by using a parallel spinning technology, and then thermally stretched to obtain a photothermal / moisture responsive fiber.

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

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

[0040] Furthermore, the light-to-heat conversion filler is 0.1 wt%-20 wt% of the hydrophobic polymer.

[0041] In the step (2), the concentration of the 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] The mixture is mixed and stirred in step (1), wherein the stirring temperature is 20-80 °C and the stirring time is 1-24 h.

[0044] In step (2), the mixture is stirred after mixing, wherein the stirring temperature is 20-80°C and the stirring time is 1-24 h.

[0045] The solvent in steps (1) and (2) includes one or more of 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 solvents used in steps (1) and (2) are the same.

[0047] The step (2) further includes a dissolving agent; wherein the dissolving agent is lithium chloride.

[0048] The coagulation bath in step (3) includes one or more of 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 the 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 heat stretching temperature is 50–100 °C and the stretching ratio is 1:1–1:2.

[0052] Step (3) heat stretching is followed by washing and then heat setting at 100–160 °C.

[0053] The present invention provides an application of any of the above-mentioned photothermal / moisture responsive fibers or the above-mentioned textiles in the fields of information, energy, environment, medical treatment, wearable devices, intelligent equipment, and soft robots.

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

[0055] Preferably, the applications in the energy field include energy conversion, energy collection, energy storage and 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 of the wearable device field include health monitoring, assisted sports, smart clothing, and electronic skin.

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

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

[0061] Specifically, the fiber material of this invention is a parallel-type composite fiber that exhibits bending-actuated behavior under infrared light irradiation. Due to the difference in thermal expansion properties between the two components of the parallel structure, the photothermal conversion material converts light energy into heat energy, which is then converted into mechanical energy through asymmetric thermal expansion, manifesting macroscopically as fiber bending deformation.

[0062] Beneficial effects

[0063] (1) Under photothermal conditions, the photothermal / moisture responsive fiber of the present invention forms a contraction stress field along the radial direction of the fiber formed by the anisotropic negative thermal expansion filler β-eucryptite nanoparticles, which synergizes with the local microstress field formed by the isotropic negative thermal expansion filler zirconium tungstate nanoparticles, and transmits the contraction stress to the thermal motion molecular chain through the hydrogen bond network, thereby inhibiting the thermal expansion of the polymer, thereby improving the photothermal driving speed and maximum bending angle of the parallel fibers.

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

[0065] (3) The present invention prepares highly oriented fibers through a heat-stretching strategy, and its breaking strength is more than 7 times that of non-heat-stretched fibers. In addition, the heat-stretched fibers have a dense structure and increased flexibility, so the response speed and maximum bending angle are significantly improved. By precisely controlling the heat-stretching strain ratio, the incompatibility problem of 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 to introduce a small amount of polymer material of another component into a certain component, aiming to promote the formation of parallel fibers and optimize the interfacial adhesion between the two components. This strategy not only gives the fiber actuator excellent cyclic stability, but also provides mechanical protection for subsequent thermal stretching treatment.

[0067] (5) The present invention provides a method for preparing photothermal / wet responsive fibers. The method mainly adopts parallel wet spinning and thermal stretching technology, is applicable to a variety of polymer materials and fillers, and has a certain universality. The method can accurately control the structure and performance of the fibers. The process is mature and automated, and has the potential for large-scale production. The fibers prepared by the method of the present invention can be twisted into yarns and woven into fabrics. The obtained fiber / fabric-based actuators have extremely important applications in the fields of information, energy, environment, medical care, and intelligent equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 This is a macroscopic effect diagram of the polyvinylidene fluoride / lignocellulose composite fiber of Example 1;

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

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

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

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

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

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

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

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

[0077] Figure 10 is the maximum bending of the polyvinylidene fluoride / lignocellulose composite fiber of comparative example 2 under infrared light irradiation;

[0078] Figure 11 The woven fabric made of polyvinylidene fluoride / lignocellulose composite fiber of Example 1;

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

[0080] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

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

[0082] Polyvinylidene fluoride (PVDF, Mw=400,000, Yuanye); N,N-dimethylformamide (DMF, AR, Aladdin); dimethylacetamide (DMAc, AR, Bidex Pharmaceuticals); wood cellulose (MCC, RG, Titan); carbon nanotubes (CNT, RG, Titan); zirconium tungstate nanoparticles (ZrW2O8, RG, Huawei Raycus); anhydrous lithium chloride (LiCl, AR, Aladdin); β-eucryptite nanoparticles (Li2Al2Si2O8, RG, Yuxling).

[0083] Test method for tensile properties of photothermal / moisture responsive fibers:

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

[0085] Light, heat and humidity driving performance test:

[0086] The sample length was 5 cm, and the test environment was a sealed acrylic box. The light and heat stimulation source came from an infrared lamp with a power of 250 W, which was 20 cm away from the sample being tested, and the test lasted for 2 minutes. The humidity stimulation was provided by a humidifier, and the humidity in the box was monitored in real time using a humidity sensor. The test humidity was controlled within the range of 30%–90%. The deformation effect of the fiber during the test was recorded using 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 driving, compare the maximum deformation angle with that before the cycle test to see if the difference is within 5% of the initial maximum deformation angle.

[0090] Method for determining interface adhesion:

[0091] Observe with naked eyes whether there is any delamination of the photothermal / moisture responsive fiber bicomponent.

[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: Dissolve polyvinylidene fluoride in dimethylacetamide to prepare a 20 wt% spinning solution. Weigh carbon nanotubes as a photothermal conversion filler and add them to the spinning solution at a mass ratio of carbon nanotubes to polyvinylidene fluoride of 1:25. Stir at 60°C for 12 hours.

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

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

[0097] The macroscopic effect of polyvinylidene fluoride / lignocellulose composite fiber is shown in the figure Figure 1 As shown; the tensile fracture diagram is as follows Figure 2 As shown; the scanning electron microscope image of polyvinylidene fluoride / lignocellulose composite fiber is shown Figure 3 As shown; the continuous bending actuation behavior generated under infrared light irradiation is shown Figure 4 As shown; the continuous bending actuation behavior under moisture stimulation is shown Figure 5 shown.

[0098] The diameter of the polyvinylidene fluoride / lignocellulose composite fiber is about 0.25 mm, the mass ratio of the two components is 1:1, and the breaking strength is as high as 75.2 MPa; it has obvious bending driving behavior under infrared light irradiation, such as Figure 6 As shown in the figure, the fiber reaches a maximum bending angle of 90° at 56 seconds and recovers to its initial state within 120 seconds under moisture stimulation. The composite fiber exhibits excellent photothermal / wet response stability, with no change in the actuation amplitude after 50 cycles.

[0099] The fiber meets the requirements of the machine. The fiber is the warp yarn and the polyester yarn is the weft yarn. The plain and twill fabrics are woven as follows: Figure 11 and Figure 12 As shown in Figure 2, the designed fabric actuator can also produce obvious 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: Dissolve polyvinylidene fluoride in dimethylacetamide to prepare a 20 wt% spinning solution. Weigh carbon nanotubes as a photothermal conversion filler and add them to the spinning solution at a mass ratio of carbon nanotubes to polyvinylidene fluoride of 1:25. Stir at 60°C for 12 hours.

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

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

[0105] The diameter of the polyvinylidene fluoride composite fiber is about 0.25 mm, the mass ratio of the two components is 1:1, and the breaking strength is 40.9 MPa; it has obvious bending driving behavior under infrared light irradiation, such as Figure 7 As shown in the figure, the fiber reaches a maximum bending angle of 15° at 10 seconds; the fiber has no obvious actuation behavior under moisture stimulation. The composite fiber shows excellent photothermal response stability, and the actuation amplitude does not change 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: Dissolve polyvinylidene fluoride in dimethylacetamide to prepare a 20 wt% spinning solution. Weigh carbon nanotubes as a photothermal conversion filler and add them to the spinning solution at a mass ratio of carbon nanotubes to polyvinylidene fluoride of 1:25. Stir at 60°C for 12 hours.

[0109] Spinning solution B: Weigh cellulose and lithium chloride and add them to dimethylacetamide, with the mass fraction of cellulose and lithium chloride being 8 wt%. Then add 2 wt% of polyvinylidene fluoride and stir. After thorough mixing, add 10 wt% (relative to the total mass of cellulose and polyvinylidene fluoride) of zirconium tungstate nanoparticles and 10 wt% (relative to the total mass of cellulose and polyvinylidene fluoride) of β-eucryptite nanoparticles in sequence, and continue stirring until uniform in preparation for subsequent spinning.

[0110] Spinning solutions A and B were squeezed 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 placed in a 30 °C oven for 24 hours to dry to obtain polyvinylidene fluoride / lignocellulose composite fibers.

[0111] The diameter of the polyvinylidene fluoride / lignocellulose composite fiber is about 0.25 mm, the mass ratio of the two components is 1:1, and the breaking strength can reach 62.7 MPa; it has obvious bending driving behavior under infrared light irradiation, such as Figure 8 As shown, the fiber reached a maximum bending angle of 18° at 3 seconds and returned to its initial state within 39 seconds under moisture stimulation. The composite fiber also exhibited excellent photothermal / wet response stability, with the actuation amplitude remaining unchanged 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: Dissolve polyvinylidene fluoride in dimethylacetamide to prepare a 20 wt% spinning solution. Weigh carbon nanotubes as a photothermal conversion filler and add them to the spinning solution at a mass ratio of carbon nanotubes to polyvinylidene fluoride of 1:25. Stir at 60°C for 12 hours.

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

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

[0117] The diameter of the polyvinylidene fluoride / lignocellulose composite fiber is about 0.25 mm, the mass ratio of the two components is 1:1, and the breaking strength can reach 60.1 MPa; it has obvious bending driving behavior under infrared light irradiation, such as Figure 9 As shown, the fiber reached a maximum bending angle of 51° at 69 seconds and recovered to its initial state within 103 seconds under moisture stimulation. The composite fiber also exhibited excellent photothermal / wet response stability, with no change in the actuation 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: Dissolve polyvinylidene fluoride in dimethylacetamide to prepare a 20 wt% spinning solution. Weigh carbon nanotubes as a photothermal conversion filler and add them to the spinning solution at a mass ratio of carbon nanotubes to polyvinylidene fluoride of 1:25. Stir at 60°C for 12 hours.

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

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

[0123] The diameter of the polyvinylidene fluoride / lignocellulose composite fiber is about 0.25 mm, the mass ratio of the two components is 1:1, and the breaking strength can reach 81.4 MPa; it has obvious bending driving behavior under infrared light irradiation, such as Figure 10 As shown, the fiber reached a maximum bending angle of 60° at 77 seconds; under moisture stimulation, it returned to its initial state within 112 seconds. In the absence of the synergistic effects of zirconium tungstate nanoparticles and β-eucryptite nanoparticles, the fiber's photothermal / hygroscopic deformation rate and maximum deformation angle were both lower than those of the fiber described in Example 1. Furthermore, the composite fiber exhibited excellent photothermal / hygroscopic stability, with no change in the actuation amplitude after 50 cycles.

[0124] Compared with Example 1 and Comparative Example 2, in Comparative Example 1, only zirconium tungstate nanoparticles were added to the second component of the polyvinylidene fluoride / lignocellulose composite fiber in Comparative Example 1, and only β-eucryptite nanoparticles were added to the second component of the polyvinylidene fluoride / lignocellulose composite fiber in Comparative Example 2. Finally, the photothermal deformation speed and maximum deformation angle of the composite fibers of Comparative Example 1 and Comparative Example 2 were both lower than those of Example 1. The present invention improves the photothermal driving speed and maximum bending angle of the composite fibers through the synergistic effect of zirconium tungstate nanoparticles and β-eucryptite 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 light-heat conversion filler and a hydrophobic polymer; the second component includes a negative thermal expansion filler and a polymer; The negative thermal expansion fillers are zirconium tungstate nanoparticles and β-eucryptite nanoparticles; The preparation method of the photothermal / humidity responsive fiber comprises: (1) mixing a photothermal conversion filler, a hydrophobic polymer, and a solvent to obtain a first spinning solution; (2) mixing a negative thermal expansion filler, a polymer, and a solvent to obtain a second spinning solution; (3) The first spinning solution and the second spinning solution are squeezed into the coagulation bath at the same time by parallel spinning technology, and then thermally stretched to obtain photothermal / moisture responsive fibers.

2. The photothermal / humidity responsive fiber according to claim 1, characterized in that: The photothermal conversion filler includes one or more of 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, ferroferric oxide nanoparticles, titanium dioxide nanoparticles, copper sulfide nanoparticles, molybdenum disulfide nanoparticles, paraffin, transition metal carbide MXene, lignin, polydopamine, polypyrrole, polyaniline and derivatives thereof; 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 modifications thereof; The light-to-heat conversion filler in the first component is 0.1 wt%-50 wt% of the mass of the hydrophobic polymer.

3. The photothermal / humidity responsive fiber according to claim 1, characterized in that: The polymer in the second component is a hydrophilic polymer, a hydrophobic polymer, or a mixture of a hydrophilic polymer and a hydrophobic polymer; the negative thermal expansion filler in the second component accounts for 0.1 wt%-50 wt% of the mass of the polymer.

4. The photothermal / humidity responsive fiber according to claim 3, characterized in that: The hydrophilic polymer includes one or more of epoxy resin, polyimide, polyacrylonitrile, wood cellulose, cotton cellulose, ethyl cellulose, cellulose nitrate, 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.

5. 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 / moisture responsive fiber is circular; The diameter of the photothermal / humidity responsive fiber is 0.1–1 mm.

6. A textile, characterized in that: The textile comprises the yarn or fabric of the light-heat / moisture-responsive fiber according to claim 1.

7. A method for preparing the photothermal / humidity responsive fiber according to any one of claims 1 to 5, characterized in that: include: Step (1) mixing a photothermal conversion filler, a hydrophobic polymer, and a solvent to obtain a first spinning solution; Step (2) mixing the negative thermal expansion filler, the polymer, and the solvent to obtain a second spinning solution; In step (3), the first spinning solution and the second spinning solution are squeezed into a coagulation bath at the same time by using a parallel spinning technology, and then thermally stretched to obtain a photothermal / moisture responsive fiber.

8. The preparation method according to claim 7, characterized in that: In the 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 the step (2), the concentration of the 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 solvent in steps (1) and (2) includes one or more of 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.

9. The preparation method according to claim 7, characterized in that: The coagulation bath in step (3) comprises one or more of 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 heat stretching temperature is 50–100 °C and the stretching ratio is 1:1–1:2; Step (3) heat stretching is followed by washing and then heat setting at 100–160 °C.

10. An application of the photothermal / moisture responsive fiber according to any one of claims 1 to 5 or the textile according to claim 6 in the fields of information, energy, environment, medical treatment, wearable devices, intelligent equipment, and soft robotics.

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