Janus flexible super fabric with dynamic regulation of infrared emissivity and preparation method and application thereof

Abstract

The present application relates to a kind of Janus flexible super fabric of dynamic regulation infrared emissivity and its preparation method and application, belong to high-performance fiber product technical field.To solve the problem that the fabric of existing dynamic regulation infrared emissivity cannot realize stepless wide range infrared reflectivity dynamic regulation, the present application provides a kind of Janus flexible super fabric of dynamic regulation infrared emissivity, with sandwich structure, from bottom to top, it is hydrophobic nanofiber film layer, low emissivity coating and hydrophilic nanofiber film layer.By the surface binding energy difference of two sides hydrophilic-hydrophobic Janus porous fabric, construct anti-gravity type one-way carrier transport channel, hydrophilic low emissivity coating with ultralow infrared emissivity and Janus porous fabric are made into sandwich structure, by the continuous, reversible change of carrier content, adjust dielectric constant, realize stepless regulation of humidity response self-adapting super wide range infrared emissivity at room temperature.

Description

Technical Field

[0001] This invention belongs to the field of high-performance fiber products technology, and particularly relates to high-performance fiber fabrics with adaptive, stepless, wide-range adjustable infrared emissivity based on high-performance nylon, high-performance acrylic fibers, etc. Specifically, it is a Janus flexible metafabric with dynamically adjustable infrared emissivity, its preparation method, and its application. Background Technology

[0002] As a cutting-edge technology in the textile industry, high-performance fabrics with dynamically adjustable infrared emissivity can monitor temperature changes in the external environment or inside the human body in real time with advanced dynamic control technology, achieve dynamic temperature balance, effectively reduce energy consumption, and bring unprecedented comfort to wearers.

[0003] High-performance fabrics with dynamically adjustable infrared emissivity currently employ various control technologies: (1) Radiation electrochromic fiber weaving technology achieves dynamic changes in infrared emissivity by electrochemically controlling the carrier concentration of carbon nanotube layers. When a negative voltage is applied, hole doping occurs in the CNT layer, reducing infrared emissivity and forming a low emissivity state, which effectively reflects the radiant heat from the human body; when a positive voltage is applied, electron doping enhances interband absorption, and the emissivity recovers to a high value, accelerating heat dissipation through radiative cooling. Textiles prepared by this technology can effectively control the temperature changes of simulated skin under ambient temperature fluctuations, and can also be applied to wearable infrared camouflage and invisible infrared displays; (2) Rare earth infrared reflective hollow heat-insulating polyamide fiber technology, by constructing a rare earth element ratio model, enables the fiber to reflect solar radiation heat in a specific band, while achieving infrared transmittance in another band, forming a continuous active cooling effect; (3) Patterned polydimethylsiloxane / MXene / nanoporous polytetrafluoroethylene superfabric technology, through simple "flip-wearing", can realize the spectral selectivity characteristics of artificially switching between low emission in the mid-infrared band and synchronous high reflection in the solar band, as well as high emission in the mid-infrared band and synchronous high absorption in the solar band; (4) Transparent electrochromic infrared emissivity device technology, by reversibly injecting / extracting electrons into aluminum-doped zinc oxide nanocrystal materials, dynamically regulating their local surface plasmon resonance absorption, and realizing the dynamic regulation of infrared emissivity.

[0004] Despite numerous effective and diverse research efforts in the field of dynamic infrared emissivity control, current techniques still suffer from various limitations and shortcomings. For example, triggering mechanisms are not simple enough, the control range is insufficient to meet requirements, and material structures are difficult to match with practical application scenarios. The most significant shortcoming is that existing dynamic infrared emissivity control techniques can essentially only achieve point-to-point, step-like control of infrared emissivity, failing to meet the needs of wide-range, stepless dynamic control. Summary of the Invention

[0005] To address the problem that existing fabrics with dynamically adjustable infrared emissivity cannot achieve stepless wide-range dynamic control of infrared reflectivity, this invention provides a Janus flexible metafabric with dynamically adjustable infrared emissivity, its preparation method, and its application.

[0006] The technical solution of this invention:

[0007] A Janus flexible metafabric with dynamically adjustable infrared emissivity has a sandwich structure, consisting of a hydrophobic nanofiber film layer, a low-emissivity coating, and a hydrophilic nanofiber film layer from bottom to top.

[0008] The hydrophobic nanofiber film layer is made of a hydrophobic material with low surface binding energy, which includes one or a combination of thermoplastic polyurethane, fluorinated polyurethane, polyvinylidene fluoride, polystyrene or polyethersulfone.

[0009] The low emissivity coating is prepared from a low emissivity material, which is a two-dimensional Ti3C2T. x Or silver nanowires;

[0010] The hydrophilic nanofiber film layer is prepared from a hydrophilic material with high surface binding energy, which includes nylon, polyacrylonitrile, or hydrophilically modified polyethylene.

[0011] Furthermore, the low emissivity coating also contains hygroscopic nanofibers, which are cellulose nanofibers or carboxylated cellulose nanofibers.

[0012] Furthermore, the hydrophilic nanofiber film layer also contains optical nanoparticles, which are one or a combination of several of titanium dioxide nanoparticles, zirconium dioxide nanoparticles, alumina nanoparticles, barium sulfate nanoparticles or calcium carbonate nanoparticles, and the particle size of the optical nanoparticles is 100-1000 nm.

[0013] A method for preparing a Janus flexible metafabric with dynamically adjustable infrared emissivity includes the following steps:

[0014] Step 1: Preparation of hydrophobic nanofiber thin film layer:

[0015] The hydrophobic material with low surface binding energy is dissolved in solvent I and stirred thoroughly to obtain a hydrophobic electrospinning solution; the obtained hydrophobic electrospinning solution is electrospinned to form a hydrophobic nanofiber thin film layer, which is then dried for later use.

[0016] Step 2: Prepare a low emissivity coating:

[0017] A suspension of low emissivity material is prepared, and a low emissivity coating is coated on the surface of the hydrophobic nanofiber film layer obtained in step one to obtain a bilayer composite film.

[0018] Step 3: Preparation of hydrophilic nanofiber thin film layer:

[0019] The hydrophilic material with high surface binding energy is dissolved in solvent II and stirred thoroughly to obtain a hydrophilic electrospinning solution. Using the bilayer composite film obtained in step two as a substrate, the hydrophilic electrospinning solution is electrospinned onto the low emissivity coating surface of the bilayer composite film to form a hydrophilic nanofiber film layer. After drying, a Janus flexible superfabric with a sandwich structure and dynamically regulated infrared emissivity is obtained.

[0020] Furthermore, in step one, solvent I is one or a combination of two of N,N-dimethylformamide, dichloromethane, chloroform, acetone, or tetrahydrofuran, and the mass ratio of the low surface binding energy hydrophobic material to solvent I is 1:4-5; the thorough stirring is carried out at 60-100°C and at a stirring speed of 300-800 r / min for at least 10 hours.

[0021] The electrospinning parameters are as follows: positive voltage 12-16kV, negative voltage -1kV, liquid pushing speed 0.02mm / min, roller speed 300r / min, needle distance from roller 15cm, needle lateral translation speed 600mm / min, spinning environment humidity 60-70%, temperature 30-35℃, hydrophobic electrospinning solution volume 1-4ml, and the thickness of the obtained hydrophobic nanofiber film layer 8-24μm.

[0022] The drying process involves vacuum drying at 60–80°C for 1–2 hours.

[0023] Furthermore, in step two, the concentration of the low-emissivity material in the suspension is 0.5–1.0 mg / ml, and the coating is performed by air spraying, ultrasonic spraying, or vacuum filtration; the thickness of the resulting low-emissivity coating is 2–15 μm.

[0024] Furthermore, the suspension of the low-emissivity material described in step two also contains hygroscopic nanofibers, which are cellulose nanofibers or carboxylated cellulose nanofibers, and the mass ratio of the low-emissivity material to the hygroscopic nanofibers is 1-7:1-3. The hygroscopic nanofibers can significantly enhance the adsorption capacity of water molecules, thereby effectively improving the controllability range of dynamic infrared emissivity.

[0025] Furthermore, in step three, solvent II is one or a mixture of several of formic acid, glacial acetic acid, dichloromethane, or trifluoroethanol with a concentration of not less than 88%; the mass ratio of the hydrophilic material with high surface binding energy to solvent II is 1:1 to 2; the thorough stirring is carried out at room temperature with a stirring speed of 300 to 800 r / min for not less than 10 hours.

[0026] The electrospinning parameters are as follows: positive voltage 20-26 kV, negative voltage -1 kV, liquid pushing speed 0.026 mm / min, roller speed 300 r / min, needle distance from roller 15 cm, needle lateral translation speed 600 mm / min, spinning environment humidity 60-70%, temperature room temperature, hydrophilic electrospinning solution volume 1-4 ml, and the thickness of the obtained hydrophilic nanofiber film layer 8-65 μm.

[0027] The drying process involves vacuum drying at 60–80°C for 1–2 hours.

[0028] Furthermore, the hydrophilic electrospinning solution described in step three also contains optical nanoparticles, which are one or a combination of several of titanium dioxide nanoparticles, zirconium dioxide nanoparticles, alumina nanoparticles, barium sulfate nanoparticles, or calcium carbonate nanoparticles, with a particle size of 100–1000 nm; the mass ratio of the optical nanoparticles to the hydrophilic material with high surface binding energy is 1–3:5–10; due to their unique intrinsic optical properties and micro / nano scale, the optical nanoparticles can effectively improve the scattering efficiency of the solar light band, thereby effectively improving the reflectivity of the solar light band.

[0029] Applications of Janus flexible metafabric with dynamically adjustable infrared emissivity in intelligent thermal and humidity management, intelligent infrared camouflage and stealth, and intelligent security or anti-counterfeiting.

[0030] The beneficial effects of this invention are:

[0031] This invention provides a Janus flexible metafabric with adaptive, stepless, wide-range adjustable infrared emissivity based on humidity response. The two sides of the hydrophilic-hydrophobic Janus porous fabric have different surface binding energies. This asymmetric wetting gradient generates capillary force differences, thereby constructing an anti-gravity unidirectional liquid carrier transport channel, achieving a "liquid diode" function of unidirectional conduction from the hydrophobic side to the hydrophilic side. A sandwich structure is formed by combining a hydrophilic low-emissivity coating with the Janus porous fabric. Due to the presence of numerous hydrophilic groups such as -OH on the surface of the hydrophilic low-emissivity coating, it can bind with charge carriers, thereby altering its intrinsic infrared characteristics. The adsorption and desorption of water molecules change the sandwich interlayer spacing and charge carrier content. The dielectric constant is adjusted through continuous and reversible changes in the charge carrier content, thereby regulating the resonant absorption in the infrared band and achieving stepless control of the ultra-wide range of infrared emissivity at room temperature.

[0032] To maximize the effective control of thermal radiation characteristics, this invention introduces radiation regulation strategies and cooling mechanisms such as radiative cooling and evaporative cooling. The coupling effect of multiple strategies further enhances the control effect of dynamic radiation characteristics. The hydrophilic nanofiber film layer of this invention has high infrared transmittance in the infrared band, which can effectively characterize the radiation characteristics of the intermediate low emissivity coating. The introduction of optical nanoparticles into the hydrophilic nanofiber film layer can effectively improve the reflectivity in the solar light band, reduce the input of external heat sources, and then maximize the cooling effect through the evaporation effect of coupled charge carriers. The heating mode can also achieve excellent heating and heat preservation effects through the active Joule heating effect of the intermediate low emissivity coating.

[0033] The Janus flexible metafabric with a sandwich structure prepared by this invention has an infrared dynamic spectral modulation range of 2-15 μm, including most of the range from near-infrared to mid-infrared. This range includes the maximum thermal radiation band of the human body (7-14 μm) and the "atmospheric window" band (8-13 μm) required for radiative cooling. It has effective practical value and application significance, and provides a new mechanism for cutting-edge applications such as adaptive infrared camouflage and adaptive temperature control.

[0034] This invention boasts advantages such as simple process, ease of operation, and significant effects. The raw materials required for the preparation of the Janus flexible metafabric with stepless wide-range dynamic infrared control based on a layer-by-layer stacking design are all commercially available and inexpensive. Preparation can be completed using an electrospinning machine and a simple vacuum filtration device. The Janus flexible metafabric with humidity-responsive, stepless wide-range adjustable infrared emissivity provided by this invention can effectively save energy consumption and reduce carbon emissions, resulting in significant social and economic benefits. Attached Figure Description

[0035] Figure 1A photograph of the PA hydrophilic nanofiber film layer of the Janus flexible metafabric prepared in Example 1;

[0036] Figure 2 SEM images of different locations on the surface of the PA hydrophilic nanofiber film layer of the Janus flexible metafabric prepared in Example 1.

[0037] Figure 3 Comparison of reflectance curves of PA hydrophilic nanofiber thin films of Janus flexible metafabric prepared in Examples 4-7 in the solar radiation band.

[0038] Figure 4 Comparison of reflectance curves of PA hydrophilic nanofiber thin films of Janus flexible metafabric prepared in Examples 8-11 in the solar radiation band.

[0039] Figure 5 Comparison of reflectance curves of PA hydrophilic nanofiber thin films of Janus flexible metafabric prepared in Examples 12-15 in the solar radiation band.

[0040] Figure 6 Thermo-infrared image of the PA hydrophilic nanofiber film layer of the Janus flexible metafabric prepared in Example 1;

[0041] Figure 7 Infrared transmittance curve of PA hydrophilic nanofiber film layer of Janus flexible metafabric prepared in Example 1.

[0042] Figure 8 Infrared images of low emissivity coatings with different C-CNF doping ratios prepared in Examples 1, 19, 16 and Comparative Example 1 in the dry state;

[0043] Figure 9 This is a photograph of the double-layer composite film prepared in step two of Example 1;

[0044] Figure 10 This is a unidirectional moisture-wicking test diagram of the Janus flexible metawoven fabric prepared in Example 4;

[0045] Figure 11 Comparison of infrared emissivity curves of low emissivity coatings with different C-CNF doping ratios prepared in Examples 17-20 and Comparative Example 1 in the dry state and the fully wet state.

[0046] Figure 12 Infrared thermal imaging images of the double-layer composite film prepared in step two of Example 4 under different humidity conditions;

[0047] Figure 13 A photograph of the actual object used in the active Joule heating effect experiment.

[0048] Figure 14 The temperature change curves of the thin film of Janus flexible metafabric prepared in Example 4 under different voltages are shown. Detailed Implementation

[0049] The technical solution of the present invention will be further described below with reference to embodiments, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention. In the following embodiments, the process equipment or apparatus not specifically specified are all conventional equipment or apparatus in the art. Unless otherwise specified, the raw materials used in the embodiments of the present invention are all commercially available; unless otherwise specified, the technical means used in the embodiments of the present invention are all conventional means well known to those skilled in the art.

[0050] Example 1

[0051] This embodiment provides a method for preparing Janus flexible metafabric with dynamically adjustable infrared emissivity. The specific preparation steps are as follows:

[0052] Step 1: Preparation of hydrophobic nanofiber thin film layer:

[0053] Solvent I was obtained by uniformly mixing N,N-dimethylformamide and tetrahydrofuran in equal volume ratio. Thermoplastic polyurethane (TPU) particles were added to the mixed solution at a mass ratio of 1:4 to TPU. The mixture was placed on a magnetic stirrer and stirred at 500 r / min for at least 10 h at a water bath temperature of 80 °C until a uniform and transparent thermoplastic polyurethane solution was obtained. Fluorinated polyurethane (FPU) was added to the obtained thermoplastic polyurethane solution to improve the hydrophobicity of the nanofiber film. The amount of fluorinated polyurethane added was controlled at 2% of the mass of thermoplastic polyurethane. The mixture was stirred for at least 2 h to obtain a white and homogeneous TPU / FPU hydrophobic electrospinning solution.

[0054] The obtained TPU / FPU hydrophobic electrospinning solution was spun into a film using an electrospinning machine. The positive voltage of electrospinning was set to 12-16 kV, the negative voltage to -1 kV, the liquid pushing speed to 0.02 mm / min, the roller speed to 300 r / min, the distance between the needle and the roller to 15 cm, the left-right translation speed of the needle to 600 mm / min, the humidity of the spinning environment to 60-70%, and the temperature to 30-35 ℃. 1 mL of solution was spun continuously to obtain a TPU / FPU hydrophobic nanofiber film layer with a thickness of 7.9 μm. The obtained TPU / FPU hydrophobic nanofiber film layer was placed in a vacuum drying oven and vacuum dried at 60 ℃ for 1 h to obtain the hydrophobic nanofiber film layer.

[0055] Step 2: Preparation of two-dimensional Ti3C2T x coating:

[0056] The initial two-dimensional Ti3C2T solution with a concentration of 5 mg / ml was prepared using deionized water. x The solution was diluted to 0.5 mg / ml, and the diluted two-dimensional Ti3C2T was then... x The solution was placed in an ultrasonic oscillator and oscillated for 1-2 minutes to obtain a uniformly dispersed two-dimensional Ti3C2T. x The hydrophobic nanofiber film layer obtained in step one is placed on a vacuum filtration device, and the two-dimensional Ti3C2T in the suspension is removed by vacuum filtration. x Uniformly distributed on a hydrophobic nanofiber film layer, forming a black two-dimensional Ti3C2T film with a thickness of 3.5 μm. x A coating is applied to obtain a composite film with a two-layer structure.

[0057] This embodiment utilizes two-dimensional Ti3C2T x The surface groups of Ti3C2T contain a large number of hydrophilic groups such as -OH, which can dynamically adsorb and desorb water molecules, thus altering the properties of Ti3C2T. x The spacing and microstructure between layers enable the unique property of stepless wide-range infrared emissivity adjustment.

[0058] Step 3: Preparation of hydrophilic nanofiber thin film layer:

[0059] Formic acid and trifluoroethanol solution were mixed evenly at a volume ratio of 1:1.3 to obtain solvent II. Nylon particles were added to solvent II at a mass ratio of nylon PA to the obtained mixture of 4:25. The mixture was placed on a magnetic stirrer and stirred at a speed of 500 r / min at room temperature for no less than 10 h until a uniform and transparent nylon electrospinning solution with nylon PA accounting for 16% of the mass fraction of solvent II was obtained.

[0060] Using the bilayer composite film obtained in step two as a substrate, the resulting nylon electrospinning solution was electrospinned in a two-dimensional Ti3C2T matrix using an electrospinning machine. x Electrospinning was used to form a film on the coating surface. The positive voltage for electrospinning was set to 20–26 kV, the negative voltage to -1 kV, the liquid pushing speed to 0.026 mm / min, the roller speed to 300 r / min, the distance between the needle and the roller to 15 cm, the lateral translation speed of the needle to 600 mm / min, the humidity of the spinning environment to 60–70%, and the temperature to room temperature. 2 mL of solution was used for continuous spinning in a two-dimensional Ti3C2T... xA PA hydrophilic nanofiber film layer with a thickness of 13.4 μm was obtained on the coating surface, which in turn yielded a composite film with a sandwich structure. The resulting composite film was placed in a vacuum drying oven and vacuum dried at 60°C for 1 h to obtain Janus flexible metafabric with adaptive humidity response and stepless wide-range adjustable infrared emissivity.

[0061] Example 2

[0062] This embodiment provides a method for preparing Janus flexible metafabric with dynamically adjustable infrared emissivity. The specific preparation steps are as follows:

[0063] Step 1: Preparation of hydrophobic nanofiber thin film layer:

[0064] Solvent I was obtained by uniformly mixing N,N-dimethylformamide and tetrahydrofuran in equal volume ratio. Thermoplastic polyurethane (TPU) particles were added to the mixed solution at a mass ratio of 1:4 to TPU. The mixture was placed on a magnetic stirrer and stirred at 500 r / min for at least 10 h at a water bath temperature of 80 °C until a uniform and transparent thermoplastic polyurethane solution was obtained. Fluorinated polyurethane (FPU) was added to the obtained thermoplastic polyurethane solution to improve the hydrophobicity of the nanofiber film. The amount of fluorinated polyurethane added was controlled at 2% of the mass of thermoplastic polyurethane. The mixture was stirred for at least 2 h to obtain a white and homogeneous TPU / FPU hydrophobic electrospinning solution.

[0065] The obtained TPU / FPU hydrophobic electrospinning solution was spun into a film using an electrospinning machine. The positive voltage of electrospinning was set to 12-16 kV, the negative voltage to -1 kV, the liquid pushing speed to 0.02 mm / min, the roller speed to 300 r / min, the distance between the needle and the roller to 15 cm, the left-right translation speed of the needle to 600 mm / min, the humidity of the spinning environment to 60-70%, and the temperature to 30-35 ℃. 1 mL of solution was spun continuously to obtain a TPU / FPU hydrophobic nanofiber film layer with a thickness of 7.9 μm. The obtained TPU / FPU hydrophobic nanofiber film layer was placed in a vacuum drying oven and vacuum dried at 60 ℃ for 1 h to obtain the hydrophobic nanofiber film layer.

[0066] Step 2: Preparation of two-dimensional Ti3C2T x coating:

[0067] The initial two-dimensional Ti3C2T solution with a concentration of 5 mg / ml was prepared using deionized water. x The solution was diluted to 0.5 mg / ml, and the diluted two-dimensional Ti3C2T was then... x The solution was placed in an ultrasonic oscillator and oscillated for 1-2 minutes to obtain a uniformly dispersed two-dimensional Ti3C2T. xThe hydrophobic nanofiber film layer obtained in step one is placed on a vacuum filtration device, and the two-dimensional Ti3C2T in the suspension is removed by vacuum filtration. x Uniformly distributed on a hydrophobic nanofiber film layer, forming a black two-dimensional Ti3C2T film with a thickness of 3.5 μm. x A coating is applied to obtain a composite film with a two-layer structure.

[0068] Step 3: Preparation of hydrophilic nanofiber thin film layer:

[0069] Formic acid and trifluoroethanol solution were mixed uniformly at a volume ratio of 1:1.3 to obtain solvent II. Nylon particles were added to solvent II at a mass ratio of 4:25 of nylon PA to the obtained mixture. The mixture was placed on a magnetic stirrer and stirred at 500 r / min at room temperature for no less than 10 h until a uniform and transparent nylon electrospinning solution with nylon PA accounting for 16% of the mass fraction of solvent II was obtained. Titanium dioxide nanoparticles with a particle size of 100-1000 nm were added to the nylon electrospinning solution at a mass ratio of 1:10 of titanium dioxide nanoparticles to nylon particles. The mixture was stirred for more than 4 h to obtain a white and homogeneous PA / TiO2 hydrophilic electrospinning solution.

[0070] Using the bilayer composite film obtained in step two as a substrate, the resulting PA / TiO2 hydrophilic electrospinning solution was electrospinned in a two-dimensional Ti3C2T matrix using an electrospinning machine. x Electrospinning was used to form a film on the coating surface. The positive voltage for electrospinning was set to 20–26 kV, the negative voltage to -1 kV, the liquid pushing speed to 0.026 mm / min, the roller speed to 300 r / min, the distance between the needle and the roller to 15 cm, the lateral translation speed of the needle to 600 mm / min, the humidity of the spinning environment to 60–70%, and the temperature to room temperature. 2 mL of solution was used for continuous spinning in a two-dimensional Ti3C2T... x A PA / TiO2 hydrophilic nanofiber film layer with a thickness of 14.3 μm and high solar reflectivity and high infrared transmittance was obtained on the coating surface, thus obtaining a composite film with a sandwich structure. The obtained composite film was placed in a vacuum drying oven and vacuum dried at 60℃ for 1 h to obtain Janus flexible metafabric with adaptive humidity response and stepless wide-range adjustable infrared emissivity.

[0071] Example 3

[0072] This embodiment provides a method for preparing Janus flexible metafabric with dynamically adjustable infrared emissivity. The specific preparation steps are as follows:

[0073] Step 1: Preparation of hydrophobic nanofiber thin film layer:

[0074] Solvent I was obtained by uniformly mixing N,N-dimethylformamide and tetrahydrofuran in equal volume ratio. Thermoplastic polyurethane (TPU) particles were added to the mixed solution at a mass ratio of 1:4 to TPU. The mixture was placed on a magnetic stirrer and stirred at 500 r / min for at least 10 h at a water bath temperature of 80 °C until a uniform and transparent thermoplastic polyurethane solution was obtained. Fluorinated polyurethane (FPU) was added to the obtained thermoplastic polyurethane solution to improve the hydrophobicity of the nanofiber film. The amount of fluorinated polyurethane added was controlled at 2% of the mass of thermoplastic polyurethane. The mixture was stirred for at least 2 h to obtain a white and homogeneous TPU / FPU hydrophobic electrospinning solution.

[0075] The obtained TPU / FPU hydrophobic electrospinning solution was spun into a film using an electrospinning machine. The positive voltage of electrospinning was set to 12-16 kV, the negative voltage to -1 kV, the liquid pushing speed to 0.02 mm / min, the roller speed to 300 r / min, the distance between the needle and the roller to 15 cm, the left-right translation speed of the needle to 600 mm / min, the humidity of the spinning environment to 60-70%, and the temperature to 30-35 ℃. 1 mL of solution was spun continuously to obtain a TPU / FPU hydrophobic nanofiber film layer with a thickness of 7.9 μm. The obtained TPU / FPU hydrophobic nanofiber film layer was placed in a vacuum drying oven and vacuum dried at 60 ℃ for 1 h to obtain the hydrophobic nanofiber film layer.

[0076] Step 2: Preparation of two-dimensional Ti3C2T x coating:

[0077] The initial two-dimensional Ti3C2T solution with a concentration of 5 mg / ml was prepared using deionized water. x The solution was diluted to 0.5 mg / ml, and cellulose nanofibers were added to the diluted solution to enhance the two-dimensional Ti3C2T. x The coating's hydrophilicity and flexibility, two-dimensional Ti3C2T x A solution containing cellulose nanofibers was placed in an ultrasonic oscillator and vibrated for 1–2 minutes at a mass ratio of 2:3 to 2:3 to obtain uniformly dispersed two-dimensional Ti3C2T. x The hydrophobic nanofiber film layer obtained in step one is placed on a vacuum filtration device, and the two-dimensional Ti3C2T in the suspension is removed by vacuum filtration. x Uniformly distributed on a hydrophobic nanofiber film layer, forming a black two-dimensional Ti3C2T film with a thickness of 4.9 μm. x A coating is applied to obtain a composite film with a two-layer structure.

[0078] Step 3: Preparation of hydrophilic nanofiber thin film layer:

[0079] Formic acid and trifluoroethanol solution were mixed evenly at a volume ratio of 1:1.3 to obtain solvent II. Nylon particles were added to solvent II at a mass ratio of nylon PA to the obtained mixture of 4:25. The mixture was placed on a magnetic stirrer and stirred at a speed of 500 r / min at room temperature for no less than 10 h until a uniform and transparent nylon electrospinning solution with nylon PA accounting for 16% of the mass fraction of solvent II was obtained.

[0080] Using the bilayer composite film obtained in step two as a substrate, the resulting nylon electrospinning solution was electrospinned in a two-dimensional Ti3C2T matrix using an electrospinning machine. x Electrospinning was used to form a film on the coating surface. The positive voltage for electrospinning was set to 20–26 kV, the negative voltage to -1 kV, the liquid pushing speed to 0.026 mm / min, the roller speed to 300 r / min, the distance between the needle and the roller to 15 cm, the lateral translation speed of the needle to 600 mm / min, the humidity of the spinning environment to 60–70%, and the temperature to room temperature. 2 mL of solution was used for continuous spinning in a two-dimensional Ti3C2T... x A PA hydrophilic nanofiber film layer with a thickness of 13.4 μm was obtained on the coating surface, which in turn yielded a composite film with a sandwich structure. The resulting composite film was placed in a vacuum drying oven and vacuum dried at 60°C for 1 h to obtain Janus flexible metafabric with adaptive humidity response and stepless wide-range adjustable infrared emissivity.

[0081] Example 4

[0082] This embodiment provides a method for preparing Janus flexible metafabric with dynamically adjustable infrared emissivity. The specific preparation steps are as follows:

[0083] Step 1: Preparation of hydrophobic nanofiber thin film layer:

[0084] Solvent I was obtained by uniformly mixing N,N-dimethylformamide and tetrahydrofuran in equal volume ratio. Thermoplastic polyurethane (TPU) particles were added to the mixed solution at a mass ratio of 1:4 to TPU. The mixture was placed on a magnetic stirrer and stirred at 500 r / min for at least 10 h at a water bath temperature of 80 °C until a uniform and transparent thermoplastic polyurethane solution was obtained. Fluorinated polyurethane (FPU) was added to the obtained thermoplastic polyurethane solution to improve the hydrophobicity of the nanofiber film. The amount of fluorinated polyurethane added was controlled at 2% of the mass of thermoplastic polyurethane. The mixture was stirred for at least 2 h to obtain a white and homogeneous TPU / FPU hydrophobic electrospinning solution.

[0085] The obtained TPU / FPU hydrophobic electrospinning solution was spun into a film using an electrospinning machine. The positive voltage of electrospinning was set to 12-16 kV, the negative voltage to -1 kV, the liquid pushing speed to 0.02 mm / min, the roller speed to 300 r / min, the distance between the needle and the roller to 15 cm, the left-right translation speed of the needle to 600 mm / min, the humidity of the spinning environment to 60-70%, and the temperature to 30-35 ℃. 1 mL of solution was spun continuously to obtain a TPU / FPU hydrophobic nanofiber film layer with a thickness of 7.9 μm. The obtained TPU / FPU hydrophobic nanofiber film layer was placed in a vacuum drying oven and vacuum dried at 60 ℃ for 1 h to obtain the hydrophobic nanofiber film layer.

[0086] Step 2: Preparation of two-dimensional Ti3C2T x coating:

[0087] The initial two-dimensional Ti3C2T solution with a concentration of 5 mg / ml was prepared using deionized water. x The solution was diluted to 0.5 mg / ml, and cellulose nanofibers (CNF) were added to the diluted solution to enhance the two-dimensional Ti3C2T. x The coating's hydrophilicity and flexibility, two-dimensional Ti3C2T x A solution containing cellulose nanofibers was placed in an ultrasonic oscillator and vibrated for 1–2 minutes at a mass ratio of 2:3 to 2:3 to obtain uniformly dispersed two-dimensional Ti3C2T. x The hydrophobic nanofiber film layer obtained in step one is placed on a vacuum filtration device, and the two-dimensional Ti3C2T in the suspension is removed by vacuum filtration. x Uniformly distributed on a hydrophobic nanofiber film layer, forming a black two-dimensional Ti3C2T film with a thickness of 4.9 μm. x A coating is applied to obtain a composite film with a two-layer structure.

[0088] Step 3: Preparation of hydrophilic nanofiber thin film layer:

[0089] Formic acid and trifluoroethanol solution were mixed uniformly at a volume ratio of 1:1.3 to obtain solvent II. Nylon particles were added to solvent II at a mass ratio of 4:25 of nylon PA to the obtained mixture. The mixture was placed on a magnetic stirrer and stirred at 500 r / min at room temperature for no less than 10 h until a uniform and transparent nylon electrospinning solution with a nylon PA mass fraction of 16% in solvent II was obtained. Titanium dioxide nanoparticles with a particle size of 100-1000 nm were added to the nylon electrospinning solution at a mass ratio of 1:10 of titanium dioxide nanoparticles to nylon particles. The mixture was stirred for more than 4 h to obtain a white and homogeneous PA / TiO2 hydrophilic electrospinning solution.

[0090] Using the bilayer composite film obtained in step two as a substrate, the resulting PA / TiO2 hydrophilic electrospinning solution was electrospinned in a two-dimensional Ti3C2T matrix using an electrospinning machine. x Electrospinning was used to form a film on the coating surface. The positive voltage for electrospinning was set to 20–26 kV, the negative voltage to -1 kV, the liquid pushing speed to 0.026 mm / min, the roller speed to 300 r / min, the distance between the needle and the roller to 15 cm, the lateral translation speed of the needle to 600 mm / min, the humidity of the spinning environment to 60–70%, and the temperature to room temperature. 2 mL of solution was used for continuous spinning in a two-dimensional Ti3C2T... x A PA / TiO2 hydrophilic nanofiber film layer with a thickness of 14.3 μm and high solar reflectivity and high infrared transmittance was obtained on the coating surface, thus obtaining a composite film with a sandwich structure. The obtained composite film was placed in a vacuum drying oven and vacuum dried at 60℃ for 1 h to obtain Janus flexible metafabric with adaptive humidity response and stepless wide-range adjustable infrared emissivity.

[0091] Example 5

[0092] The only difference between this embodiment and Embodiment 4 is that the volume of the PA / TiO2 hydrophilic electrospinning solution used in step three of this embodiment is 1 mL, in the two-dimensional Ti3C2T... x A PA / TiO2 hydrophilic nanofiber film layer with a thickness of 8.3 μm and high solar reflectivity and high infrared transmittance was obtained on the coating surface, thus obtaining a composite film with a sandwich structure. The obtained composite film was placed in a vacuum drying oven and vacuum dried at 60℃ for 1 h to obtain Janus flexible metafabric with adaptive humidity response and stepless wide-range adjustable infrared emissivity.

[0093] Example 6

[0094] The only difference between this embodiment and Embodiment 4 is that the volume of the PA / TiO2 hydrophilic electrospinning solution used in step three of this embodiment is 3 mL, in the two-dimensional Ti3C2T... x A PA / TiO2 hydrophilic nanofiber film layer with a thickness of 20.3 μm and high solar reflectivity and high infrared transmittance was obtained on the coating surface, thus obtaining a composite film with a sandwich structure. The obtained composite film was placed in a vacuum drying oven and vacuum dried at 60℃ for 1 h to obtain Janus flexible metafabric with adaptive humidity response and stepless wide-range adjustable infrared emissivity.

[0095] Example 7

[0096] The only difference between this embodiment and Embodiment 4 is that the volume of the PA / TiO2 hydrophilic electrospinning solution used in step three of this embodiment is 4 mL, in the two-dimensional Ti3C2T... x A PA / TiO2 hydrophilic nanofiber film layer with a thickness of 26.6 μm and high solar reflectivity and high infrared transmittance was obtained on the coating surface, thus obtaining a composite film with a sandwich structure. The obtained composite film was placed in a vacuum drying oven and vacuum dried at 60°C for 1 h to obtain Janus flexible metafabric with adaptive humidity response and stepless wide-range adjustable infrared emissivity.

[0097] Example 8

[0098] The difference between this embodiment and embodiment 4 is only that in step three of this embodiment, formic acid and trifluoroethanol solution are mixed uniformly at a volume ratio of 1:1.3 to obtain a mixed system. Nylon particles are added to the obtained mixed system at a mass ratio of 1:5 of nylon PA to the obtained mixed system. The mixture is placed on a magnetic stirrer and stirred at a speed of 500 r / min at room temperature for no less than 10 h until a uniform and transparent nylon electrospinning solution with a nylon PA mass fraction of 20% in solvent II is obtained. Titanium dioxide nanoparticles with a particle size of 100-1000 nm are added to the nylon electrospinning solution at a mass ratio of 1:10 of titanium dioxide nanoparticles to nylon particles. The mixture is stirred for more than 4 h to obtain a white and homogeneous PA / TiO2 hydrophilic electrospinning solution.

[0099] Using the bilayer composite film obtained in step two as a substrate, the resulting PA / TiO2 hydrophilic electrospinning solution was electrospinned in a two-dimensional Ti3C2T matrix using an electrospinning machine. x Electrospinning was used to form a film on the coating surface. The positive voltage for electrospinning was set to 20–26 kV, the negative voltage to -1 kV, the liquid pushing speed to 0.026 mm / min, the roller speed to 300 r / min, the distance between the needle and the roller to 15 cm, the lateral translation speed of the needle to 600 mm / min, the humidity of the spinning environment to 60–70%, and the temperature to room temperature. 1 mL of solution was used for continuous spinning in a two-dimensional Ti3C2T... x A PA / TiO2 hydrophilic nanofiber film layer with a thickness of 11.7 μm and high solar reflectivity and high infrared transmittance was obtained on the coating surface, thus obtaining a composite film with a sandwich structure. The obtained composite film was placed in a vacuum drying oven and vacuum dried at 60°C for 1 h to obtain Janus flexible metafabric with adaptive humidity response and stepless wide-range adjustable infrared emissivity.

[0100] Example 9

[0101] The difference between this embodiment and embodiment 4 is only that in step three of this embodiment, formic acid and trifluoroethanol solution are mixed uniformly at a volume ratio of 1:1.3 to obtain a mixed system. Nylon particles are added to the obtained mixed system at a mass ratio of 1:5 of nylon PA to the obtained mixed system. The mixture is placed on a magnetic stirrer and stirred at a speed of 500 r / min at room temperature for no less than 10 h until a uniform and transparent nylon electrospinning solution with a nylon PA mass fraction of 20% in solvent II is obtained. Titanium dioxide nanoparticles with a particle size of 100-1000 nm are added to the nylon electrospinning solution at a mass ratio of 1:10 of titanium dioxide nanoparticles to nylon particles. The mixture is stirred for more than 4 h to obtain a white and homogeneous PA / TiO2 hydrophilic electrospinning solution.

[0102] Using the bilayer composite film obtained in step two as a substrate, the resulting PA / TiO2 hydrophilic electrospinning solution was electrospinned in a two-dimensional Ti3C2T matrix using an electrospinning machine. x Electrospinning was used to form a film on the coating surface. The positive voltage for electrospinning was set to 20–26 kV, the negative voltage to -1 kV, the liquid pushing speed to 0.026 mm / min, the roller speed to 300 r / min, the distance between the needle and the roller to 15 cm, the lateral translation speed of the needle to 600 mm / min, the humidity of the spinning environment to 60–70%, and the temperature to room temperature. 2 mL of solution was used for continuous spinning in a two-dimensional Ti3C2T... x A PA / TiO2 hydrophilic nanofiber film layer with a thickness of 16.2 μm and high solar reflectivity and high infrared transmittance was obtained on the coating surface, thus obtaining a composite film with a sandwich structure. The obtained composite film was placed in a vacuum drying oven and vacuum dried at 60℃ for 1 h to obtain Janus flexible metafabric with adaptive humidity response and stepless wide-range adjustable infrared emissivity.

[0103] Example 10

[0104] The difference between this embodiment and embodiment 4 is only that in step three of this embodiment, formic acid and trifluoroethanol solution are mixed uniformly at a volume ratio of 1:1.3 to obtain a mixed system. Nylon particles are added to the obtained mixed system at a mass ratio of 1:5 of nylon PA to the obtained mixed system. The mixture is placed on a magnetic stirrer and stirred at a speed of 500 r / min at room temperature for no less than 10 h until a uniform and transparent nylon electrospinning solution with a nylon PA mass fraction of 20% in solvent II is obtained. Titanium dioxide nanoparticles with a particle size of 100-1000 nm are added to the nylon electrospinning solution at a mass ratio of 1:10 of titanium dioxide nanoparticles to nylon particles. The mixture is stirred for more than 4 h to obtain a white and homogeneous PA / TiO2 hydrophilic electrospinning solution.

[0105] Using the bilayer composite film obtained in step two as a substrate, the resulting PA / TiO2 hydrophilic electrospinning solution was electrospinned in a two-dimensional Ti3C2T matrix using an electrospinning machine. x Electrospinning was used to form a film on the coating surface. The positive voltage for electrospinning was set to 20–26 kV, the negative voltage to -1 kV, the liquid pushing speed to 0.026 mm / min, the roller speed to 300 r / min, the distance between the needle and the roller to 15 cm, the lateral translation speed of the needle to 600 mm / min, the humidity of the spinning environment to 60–70%, and the temperature to room temperature. Continuous spinning was performed using a solution volume of 3 mL in a two-dimensional Ti3C2T... x A PA / TiO2 hydrophilic nanofiber film layer with a thickness of 24.1 μm and high solar reflectivity and high infrared transmittance was obtained on the coating surface, thus obtaining a composite film with a sandwich structure. The obtained composite film was placed in a vacuum drying oven and vacuum dried at 60°C for 1 h to obtain Janus flexible metafabric with adaptive humidity response and stepless wide-range adjustable infrared emissivity.

[0106] Example 11

[0107] The only difference between this embodiment and embodiment 4 is that in step three of this embodiment, formic acid and trifluoroethanol solution are mixed uniformly at a volume ratio of 1:1.3 to obtain a mixed system. The mass ratio of nylon PA to the obtained mixed system is 1:5. Nylon particles are added to the obtained mixed system and placed on a magnetic stirrer. The mixture is stirred at 500 r / min at room temperature for no less than 10 h until a uniform and transparent nylon electrospinning solution with nylon PA accounting for 20% of the mass fraction of solvent II is obtained. Titanium dioxide nanoparticles with a particle size of 100-1000 nm are added to the nylon electrospinning solution. The mass ratio of titanium dioxide nanoparticles to nylon particles is 1:10. The mixture is stirred for more than 4 h to obtain a white and homogeneous PA / TiO2 hydrophilic electrospinning solution.

[0108] Using the bilayer composite film obtained in step two as a substrate, the resulting PA / TiO2 hydrophilic electrospinning solution was electrospinned in a two-dimensional Ti3C2T matrix using an electrospinning machine. x Electrospinning was used to form a film on the coating surface. The positive voltage for electrospinning was set to 20–26 kV, the negative voltage to -1 kV, the liquid pushing speed to 0.026 mm / min, the roller speed to 300 r / min, the distance between the needle and the roller to 15 cm, the lateral translation speed of the needle to 600 mm / min, the humidity of the spinning environment to 60–70%, and the temperature to room temperature. 4 mL of solution was used for continuous spinning in a two-dimensional Ti3C2T... xA PA / TiO2 hydrophilic nanofiber film layer with a thickness of 45.6 μm and high solar reflectivity and high infrared transmittance was obtained on the coating surface, thus obtaining a composite film with a sandwich structure. The obtained composite film was placed in a vacuum drying oven and vacuum dried at 60℃ for 1 h to obtain Janus flexible metafabric with adaptive humidity response and stepless wide-range adjustable infrared emissivity.

[0109] Example 12

[0110] The difference between this embodiment and embodiment 4 is only that in step three of this embodiment, formic acid and trifluoroethanol solution are mixed uniformly at a volume ratio of 1:1.3 to obtain a mixed system. Nylon particles are added to the obtained mixed system at a mass ratio of 1:4 of nylon PA to the obtained mixed system. The mixture is placed on a magnetic stirrer and stirred at a speed of 500 r / min at room temperature for no less than 10 h until a uniform and transparent nylon electrospinning solution with a nylon PA mass fraction of 25% in solvent II is obtained. Titanium dioxide nanoparticles with a particle size of 100-1000 nm are added to the nylon electrospinning solution at a mass ratio of 1:10 of titanium dioxide nanoparticles to nylon particles. The mixture is stirred for more than 4 h to obtain a white and homogeneous PA / TiO2 hydrophilic electrospinning solution.

[0111] Using the bilayer composite film obtained in step two as a substrate, the resulting PA / TiO2 hydrophilic electrospinning solution was electrospinned in a two-dimensional Ti3C2T matrix using an electrospinning machine. x Electrospinning was used to form a film on the coating surface. The positive voltage for electrospinning was set to 20–26 kV, the negative voltage to -1 kV, the liquid pushing speed to 0.026 mm / min, the roller speed to 300 r / min, the distance between the needle and the roller to 15 cm, the lateral translation speed of the needle to 600 mm / min, the humidity of the spinning environment to 60–70%, and the temperature to room temperature. 1 mL of solution was used for continuous spinning in a two-dimensional Ti3C2T... x A PA / TiO2 hydrophilic nanofiber film layer with a thickness of 13.4 μm and high solar reflectivity and high infrared transmittance was obtained on the coating surface, thus obtaining a composite film with a sandwich structure. The obtained composite film was placed in a vacuum drying oven and vacuum dried at 60℃ for 1 h to obtain Janus flexible metafabric with adaptive humidity response and stepless wide-range adjustable infrared emissivity.

[0112] Example 13

[0113] The difference between this embodiment and embodiment 4 is only that in step three of this embodiment, formic acid and trifluoroethanol solution are mixed uniformly at a volume ratio of 1:1.3 to obtain a mixed system. Nylon particles are added to the obtained mixed system at a mass ratio of 1:4 of nylon PA to the obtained mixed system. The mixture is placed on a magnetic stirrer and stirred at a speed of 500 r / min at room temperature for no less than 10 h until a uniform and transparent nylon electrospinning solution with a nylon PA mass fraction of 25% in solvent II is obtained. Titanium dioxide nanoparticles with a particle size of 100-1000 nm are added to the nylon electrospinning solution at a mass ratio of 1:10 of titanium dioxide nanoparticles to nylon particles. The mixture is stirred for more than 4 h to obtain a white and homogeneous PA / TiO2 hydrophilic electrospinning solution.

[0114] Using the bilayer composite film obtained in step two as a substrate, the resulting PA / TiO2 hydrophilic electrospinning solution was electrospinned in a two-dimensional Ti3C2T matrix using an electrospinning machine. x Electrospinning was used to form a film on the coating surface. The positive voltage for electrospinning was set to 20–26 kV, the negative voltage to -1 kV, the liquid pushing speed to 0.026 mm / min, the roller speed to 300 r / min, the distance between the needle and the roller to 15 cm, the lateral translation speed of the needle to 600 mm / min, the humidity of the spinning environment to 60–70%, and the temperature to room temperature. 2 mL of solution was used for continuous spinning in a two-dimensional Ti3C2T... x A PA / TiO2 hydrophilic nanofiber film layer with a thickness of 29.7 μm and high solar reflectivity and high infrared transmittance was obtained on the coating surface, thus obtaining a composite film with a sandwich structure. The obtained composite film was placed in a vacuum drying oven and vacuum dried at 60°C for 1 h to obtain Janus flexible metafabric with adaptive humidity response and stepless wide-range adjustable infrared emissivity.

[0115] Example 14

[0116] The difference between this embodiment and embodiment 4 is only that in step three of this embodiment, formic acid and trifluoroethanol solution are mixed uniformly at a volume ratio of 1:1.3 to obtain a mixed system. Nylon particles are added to the obtained mixed system at a mass ratio of 1:4 of nylon PA to the obtained mixed system. The mixture is placed on a magnetic stirrer and stirred at a speed of 500 r / min at room temperature for no less than 10 h until a uniform and transparent nylon electrospinning solution with a nylon PA mass fraction of 25% in solvent II is obtained. Titanium dioxide nanoparticles with a particle size of 100-1000 nm are added to the nylon electrospinning solution at a mass ratio of 1:10 of titanium dioxide nanoparticles to nylon particles. The mixture is stirred for more than 4 h to obtain a white and homogeneous PA / TiO2 hydrophilic electrospinning solution.

[0117] Using the bilayer composite film obtained in step two as a substrate, the resulting PA / TiO2 hydrophilic electrospinning solution was electrospinned in a two-dimensional Ti3C2T matrix using an electrospinning machine. x Electrospinning was used to form a film on the coating surface. The positive voltage for electrospinning was set to 20–26 kV, the negative voltage to -1 kV, the liquid pushing speed to 0.026 mm / min, the roller speed to 300 r / min, the distance between the needle and the roller to 15 cm, the lateral translation speed of the needle to 600 mm / min, the humidity of the spinning environment to 60–70%, and the temperature to room temperature. Continuous spinning was performed using a solution volume of 3 mL in a two-dimensional Ti3C2T... x A PA / TiO2 hydrophilic nanofiber film layer with a thickness of 46.5 μm and high solar reflectivity and high infrared transmittance was obtained on the coating surface, thus obtaining a composite film with a sandwich structure. The obtained composite film was placed in a vacuum drying oven and vacuum dried at 60°C for 1 h to obtain Janus flexible metafabric with adaptive humidity response and stepless wide-range adjustable infrared emissivity.

[0118] Example 15

[0119] The difference between this embodiment and embodiment 4 is only that in step three of this embodiment, formic acid and trifluoroethanol solution are mixed uniformly at a volume ratio of 1:1.3 to obtain a mixed system. Nylon particles are added to the obtained mixed system at a mass ratio of 1:4 of nylon PA to the obtained mixed system. The mixture is placed on a magnetic stirrer and stirred at a speed of 500 r / min at room temperature for no less than 10 h until a uniform and transparent nylon electrospinning solution with a nylon PA mass fraction of 25% in solvent II is obtained. Titanium dioxide nanoparticles with a particle size of 100-1000 nm are added to the nylon electrospinning solution at a mass ratio of 1:10 of titanium dioxide nanoparticles to nylon particles. The mixture is stirred for more than 4 h to obtain a white and homogeneous PA / TiO2 hydrophilic electrospinning solution.

[0120] Using the bilayer composite film obtained in step two as a substrate, the resulting PA / TiO2 hydrophilic electrospinning solution was electrospinned in a two-dimensional Ti3C2T matrix using an electrospinning machine. x Electrospinning was used to form a film on the coating surface. The positive voltage for electrospinning was set to 20–26 kV, the negative voltage to -1 kV, the liquid pushing speed to 0.026 mm / min, the roller speed to 300 r / min, the distance between the needle and the roller to 15 cm, the lateral translation speed of the needle to 600 mm / min, the humidity of the spinning environment to 60–70%, and the temperature to room temperature. 4 mL of solution was used for continuous spinning in a two-dimensional Ti3C2T... xA PA / TiO2 hydrophilic nanofiber film layer with a thickness of 64.1 μm and high solar reflectivity and high infrared transmittance was obtained on the coating surface, thus obtaining a composite film with a sandwich structure. The obtained composite film was placed in a vacuum drying oven and vacuum dried at 60℃ for 1 h to obtain Janus flexible metafabric with adaptive humidity response and stepless wide-range adjustable infrared emissivity.

[0121] Example 16

[0122] The only difference between this embodiment and Embodiment 4 is that in step two of this embodiment, deionized water is used to prepare the initial two-dimensional Ti3C2T solution with a concentration of 5 mg / ml. x The solution was diluted to 0.5 mg / ml, and carboxylated cellulose nanofibers (C-CNF) were added to the diluted solution, forming a two-dimensional Ti3C2T nanofiber. x The mass ratio of C-CNF to Ti3C2T is 1:4. The solution containing C-CNF is placed in an ultrasonic oscillator and oscillated for 1-2 minutes to obtain a uniformly dispersed two-dimensional Ti3C2T. x The suspension is designated as 20% Ti3C2T. x / C-CNF, the hydrophobic nanofiber film layer obtained in step one is placed on a vacuum filtration device, and the two-dimensional Ti3C2T in the suspension is removed by vacuum filtration. x Uniformly distributed on the hydrophobic nanofiber film layer, forming a two-dimensional Ti3C2T x The coating is then applied to obtain a composite film with a two-layer structure.

[0123] Example 17

[0124] The only difference between this embodiment and Embodiment 4 is that in step two of this embodiment, deionized water is used to prepare the initial two-dimensional Ti3C2T solution with a concentration of 5 mg / ml. x The solution was diluted to 0.5 mg / ml, and carboxylated cellulose nanofibers (C-CNF) were added to the diluted solution, forming a two-dimensional Ti3C2T nanofiber. x The mass ratio of C-CNF to Ti3C2T is 2:3. The solution containing C-CNF is placed in an ultrasonic oscillator and oscillated for 1-2 minutes to obtain a uniformly dispersed two-dimensional Ti3C2T. x Suspension, denoted as 40% Ti3C2T x / C-CNF, the hydrophobic nanofiber film layer obtained in step one is placed on a vacuum filtration device, and the two-dimensional Ti3C2T in the suspension is removed by vacuum filtration. x Uniformly distributed on the hydrophobic nanofiber film layer, forming a two-dimensional Ti3C2T x The coating is then applied to obtain a composite film with a two-layer structure.

[0125] Example 18

[0126] The only difference between this embodiment and Embodiment 4 is that in step two of this embodiment, deionized water is used to prepare the initial two-dimensional Ti3C2T solution with a concentration of 5 mg / ml. x The solution was diluted to 0.5 mg / ml, and carboxylated cellulose nanofibers (C-CNF) were added to the diluted solution, forming a two-dimensional Ti3C2T nanofiber. x The mass ratio of C-CNF to Ti3C2T is 1:1. The solution containing C-CNF is placed in an ultrasonic oscillator and oscillated for 1-2 minutes to obtain a uniformly dispersed two-dimensional Ti3C2T. x Suspension, denoted as 50% Ti3C2T x / C-CNF, the hydrophobic nanofiber film layer obtained in step one is placed on a vacuum filtration device, and the two-dimensional Ti3C2T in the suspension is removed by vacuum filtration. x Uniformly distributed on the hydrophobic nanofiber film layer, forming a two-dimensional Ti3C2T x The coating is then applied to obtain a composite film with a two-layer structure.

[0127] Example 19

[0128] The only difference between this embodiment and Embodiment 4 is that in step two of this embodiment, deionized water is used to prepare the initial two-dimensional Ti3C2T solution with a concentration of 5 mg / ml. x The solution was diluted to 0.5 mg / ml, and carboxylated cellulose nanofibers (C-CNF) were added to the diluted solution, forming a two-dimensional Ti3C2T nanofiber. x The mass ratio of C-CNF to Ti3C2T is 3:2. The solution containing C-CNF is placed in an ultrasonic oscillator and oscillated for 1-2 minutes to obtain a uniformly dispersed two-dimensional Ti3C2T. x The suspension is designated as 60% Ti3C2T x / C-CNF, the hydrophobic nanofiber film layer obtained in step one is placed on a vacuum filtration device, and the two-dimensional Ti3C2T in the suspension is removed by vacuum filtration. x Uniformly distributed on the hydrophobic nanofiber film layer, forming a two-dimensional Ti3C2T x The coating is then applied to obtain a composite film with a two-layer structure.

[0129] Example 20

[0130] The only difference between this embodiment and Embodiment 4 is that in step two of this embodiment, deionized water is used to prepare the initial two-dimensional Ti3C2T solution with a concentration of 5 mg / ml. x The solution was diluted to 0.5 mg / ml, and carboxylated cellulose nanofibers (C-CNF) were added to the diluted solution, forming a two-dimensional Ti3C2T nanofiber. x The mass ratio of C-CNF to Ti3C2T is 7:3. The solution containing C-CNF is placed in an ultrasonic oscillator and oscillated for 1-2 minutes to obtain a uniformly dispersed two-dimensional Ti3C2T. xThe suspension is designated as 70% Ti3C2T. x / C-CNF, the hydrophobic nanofiber film layer obtained in step one is placed on a vacuum filtration device, and the two-dimensional Ti3C2T in the suspension is removed by vacuum filtration. x Uniformly distributed on the hydrophobic nanofiber film layer, forming a two-dimensional Ti3C2T x The coating is then applied to obtain a composite film with a two-layer structure.

[0131] Example 21

[0132] The only difference between this embodiment and Embodiment 4 is that in step three of this embodiment, the mass ratio of titanium dioxide nanoparticles to nylon particles is 1:5, resulting in a white, homogeneous PA / TiO2 hydrophilic electrospinning solution. Using the bilayer composite film obtained in step two as a substrate, the resulting PA / TiO2 hydrophilic electrospinning solution is electrospinned using an electrospinning machine on a two-dimensional Ti3C2T... x The coating surface is electrospun into a film to obtain Janus flexible metafabric with adaptive humidity response and stepless wide-range adjustable infrared emissivity.

[0133] Example 22

[0134] The only difference between this embodiment and Embodiment 4 is that in step three of this embodiment, the mass ratio of titanium dioxide nanoparticles to nylon particles is 3:10, resulting in a white, homogeneous PA / TiO2 hydrophilic electrospinning solution. Using the bilayer composite film obtained in step two as a substrate, the resulting PA / TiO2 hydrophilic electrospinning solution is electrospinned using an electrospinning machine on a two-dimensional Ti3C2T... x The coating surface is electrospun into a film to obtain Janus flexible metafabric with adaptive humidity response and stepless wide-range adjustable infrared emissivity.

[0135] Example 23

[0136] The only difference between this embodiment and Embodiment 4 is that in step three of this embodiment, the mass ratio of titanium dioxide nanoparticles to nylon particles is 2:5, resulting in a white, homogeneous PA / TiO2 hydrophilic electrospinning solution. Using the bilayer composite film obtained in step two as a substrate, the resulting PA / TiO2 hydrophilic electrospinning solution is electrospinned using an electrospinning machine on a two-dimensional Ti3C2T... x The coating surface is electrospun into a film to obtain Janus flexible metafabric with adaptive humidity response and stepless wide-range adjustable infrared emissivity.

[0137] Example 24

[0138] The only difference between this embodiment and Embodiment 4 is that in step three of this embodiment, zirconium dioxide nanoparticles with a particle size of 100-1000 nm are added to the nylon electrospinning solution, with a mass ratio of zirconium dioxide nanoparticles to nylon particles of 1:10. Stirring is continued for at least 4 hours to obtain a white, homogeneous PA / ZrO2 hydrophilic electrospinning solution. Using the bilayer composite film obtained in step two as a substrate, the obtained PA / ZrO2 hydrophilic electrospinning solution is then processed through an electrospinning machine on a two-dimensional Ti3C2T... x The coating surface is electrospun into a film to obtain Janus flexible metafabric with adaptive humidity response and stepless wide-range adjustable infrared emissivity.

[0139] Example 25

[0140] The only difference between this embodiment and Embodiment 4 is that in step three of this embodiment, zirconium dioxide nanoparticles with a particle size of 100-1000 nm are added to the nylon electrospinning solution, with a mass ratio of zirconium dioxide nanoparticles to nylon particles of 1:5. Stirring is continued for at least 4 hours to obtain a white, homogeneous PA / ZrO2 hydrophilic electrospinning solution. Using the bilayer composite film obtained in step two as a substrate, the obtained PA / ZrO2 hydrophilic electrospinning solution is electrospinned using an electrospinning machine on a two-dimensional Ti3C2T substrate. x The coating surface is electrospun into a film to obtain Janus flexible metafabric with adaptive humidity response and stepless wide-range adjustable infrared emissivity.

[0141] Example 26

[0142] The only difference between this embodiment and Embodiment 4 is that in step three of this embodiment, zirconium dioxide nanoparticles with a particle size of 100-1000 nm are added to the nylon electrospinning solution, with a mass ratio of zirconium dioxide nanoparticles to nylon particles of 3:10. Stirring is continued for at least 4 hours to obtain a white, homogeneous PA / ZrO2 hydrophilic electrospinning solution. Using the bilayer composite film obtained in step two as a substrate, the obtained PA / ZrO2 hydrophilic electrospinning solution is electrospinned using an electrospinning machine on a two-dimensional Ti3C2T substrate. x The coating surface is electrospun into a film to obtain Janus flexible metafabric with adaptive humidity response and stepless wide-range adjustable infrared emissivity.

[0143] Example 27

[0144] The difference between this embodiment and Embodiment 4 is only that in Step 3 of this embodiment, zirconia nanoparticles with a particle size of 100 - 1000 nm are added to the nylon electrospinning solution, and the mass ratio of zirconia nanoparticles to nylon particles is 2:5. Stir for more than 4 h to obtain a white homogeneous PA / ZrO₂ hydrophilic electrospinning solution; using the double-layer composite film obtained in Step 2 as the substrate, the obtained PA / ZrO₂ hydrophilic electrospinning solution is electrospun into a film on the surface of the two-dimensional Ti3C2T x coating surface by an electrospinning machine to obtain a Janus flexible superfabric with humidity-responsive self-adaptive stepless wide-range adjustable infrared emissivity.

[0145] Comparative Example 1

[0146] The difference between this comparative example and Embodiment 4 is only that in Step 2 of this comparative example, no two-dimensional Ti3C2T x is added. Carboxylated cellulose nanofibers C-CNF are added to deionized water, and the solution containing C-CNF is placed in an ultrasonic oscillator and oscillated for 1 - 2 min to obtain a uniformly dispersed C-CNF suspension. The hydrophobic nanofiber film layer obtained in Step 1 is placed on a vacuum filtration device, and the C-CNF in the suspension is uniformly distributed on the hydrophobic nanofiber film layer through vacuum filtration to form an intermediate layer, and then a double-layer composite film is obtained.

[0147] Figure 1 Fig. is a physical photo of the PA hydrophilic nanofiber film layer of the Janus flexible superfabric prepared in Example 1; Figure 2 Fig. is a SEM image of different positions on the surface of the PA hydrophilic nanofiber film layer of the Janus flexible superfabric prepared in Example 1; It can be seen from Figure 1 and Figure 2 that macroscopically, the electrospun PA nanofiber membrane is a homogeneous white film; microscopically, the uniform and continuous nanofiber layers are stacked, and as the PA mass fraction increases, the diameter of the nanofibers also increases.

[0148] Figures 3-5 Fig. is a comparison chart of the reflectance curves in the solar spectrum band of the PA hydrophilic nanofiber film layers of the Janus flexible superfabrics prepared in Examples 4 - 7, Examples 8 - 11, and Examples 12 - 15; It can be seen from Figures 3-5 that as the amount of the electrospinning solution increases, the reflectance of the PA film in the solar spectrum band gradually increases. Under the condition of spinning the same volume of solution, the higher the PA mass fraction, the higher the reflectance of the PA film in the solar spectrum band.

[0149] Figure 6 Fig. is a thermal infrared imaging diagram of the PA hydrophilic nanofiber film layer of the Janus flexible superfabric prepared in Example 1; Figure 7The infrared transmittance curve of the PA hydrophilic nanofiber film layer of the Janus flexible metafabric prepared in Example 1 is shown. Figure 6 and Figure 7 It can be seen that as the thickness of the spinning increases, the infrared transmittance of the PA hydrophilic nanofiber film layer gradually decreases, and the infrared thermal imaging image of the object behind it gradually becomes blurry.

[0150] Figure 8 Infrared images of low emissivity coatings with different C-CNF doping ratios prepared in Examples 1, 19, 16, and Comparative Example 1 in their dry state; by Figure 8 It can be seen that, at the same temperature, the infrared thermal imaging temperature of the coating increases with the increase of the C-CNF doping ratio. According to the Stefan Boltzmann law, the higher the energy radiated by an object at the same temperature (i.e., the higher the thermal imaging temperature of the object's surface), the higher the infrared emissivity of the object. Therefore, it can be concluded that the higher the mass fraction of C-CNF, the higher the infrared emissivity of the thin film.

[0151] Figure 9 This is a photograph of the composite film with a double-layer structure prepared in step two of Example 1; Figure 9 It can be seen that the two-dimensional Ti3C2T x The coating has good adhesion to the hydrophobic electrospun film, and is uniformly adhered to one side of the hydrophobic electrospun film, forming a double-layer composite film with good tensile strength and deformation resistance.

[0152] Figure 10 This image shows a unidirectional moisture-wicking test of the Janus flexible metafabric prepared in Example 4. To test the unidirectional moisture-wicking effect of the Janus flexible metafabric, the hydrophilic-hydrophobic asymmetric surfaces of the prepared Janus flexible metafabric were each placed with equal amounts of blue liquid droplets facing upwards for a unidirectional moisture-wicking test. When the hydrophobic side faced upwards, the droplet was hemispherical and was gradually absorbed by the hydrophilic film below due to gravity and capillary forces. Almost no blue liquid residue remained on the hydrophobic film, as the blue droplet was almost entirely absorbed by the hydrophilic side below. When the hydrophilic side faced upwards, the droplet was disc-shaped and diffused rapidly within the hydrophilic layer. Due to the combined effects of gravity, capillary forces, and hydrophobic forces, the droplet did not continue to diffuse downwards after contacting the hydrophobic layer but instead diffused horizontally and uniformly within the hydrophilic layer. Specifically, the hydrophilic layer appeared deep blue, while the color of the hydrophobic layer remained almost unchanged. This indicates that the hydrophilic-hydrophobic Janus flexible fabric has a unidirectional moisture-wicking property, where liquid can only be conducted from the hydrophobic side to the hydrophilic side, and not from the hydrophilic side to the hydrophobic side, exhibiting the "liquid diode" characteristic of unidirectional moisture wicking.

[0153] To test the two-dimensional Ti3C2T xThe dynamic control performance of the coating was tested under different doping ratios for two-dimensional Ti3C2T. x Infrared emissivity of the coating under dry and fully wet conditions. Figure 11 The image shows a comparison of the infrared emissivity curves of low-emissivity coatings with different C-CNF doping ratios prepared in Examples 17-20 and Comparative Example 1 in both dry and fully wet states. Figure 11 It can be seen that as the mass ratio of titanium carbide gradually decreases, the infrared modulation range first increases and then decreases. In Ti3C2T x When the mass percentage is around 70%, the infrared modulation range of the film reaches its widest point, Δε = 68.18%. This is because C-CNF has both high hygroscopicity and high infrared emissivity.

[0154] Then, two-dimensional Ti3C2T was performed. x The stepless dynamic infrared emissivity control test of the coating was conducted by placing the fully wetted bilayer composite film prepared in step two of Example 4 on a 35°C constant temperature stage, and recording the infrared image of the film surface every minute. Figure 12 Infrared thermal imaging images of the bilayer composite film prepared in step two of Example 4 under different humidity levels; Figure 12 As shown, the temperature of the film gradually decreases as it transitions from a wet to a dry state, indicating that the infrared emissivity of the film gradually decreases, proving that the two-dimensional Ti3C2T... x The coating exhibits stepless dynamic infrared emissivity modulation characteristics as the humidity changes.

[0155] To test the active Joule heating capability of the Janus flexible metafabric, experiments were conducted using a portable 0-16V power supply connected to a wire. The actual test setup is shown in the image below. Figure 13 As shown. Figure 14 The graph shows the temperature change of the thin film of the Janus flexible metafabric prepared in Example 4 under different voltages. Figure 14 As can be seen, the maximum heating temperature can reach 51℃ under a voltage of 5V, with a maximum temperature rise of 31.1℃. Furthermore, after power is cut off, the temperature can rapidly drop to room temperature in a short time, thus demonstrating that Janus flexible microfabric has a significant rapid temperature regulation function.

Claims

1. A Janus flexible metafabric with dynamically adjustable infrared emissivity, characterized in that, It has a sandwich structure, consisting of a hydrophobic nanofiber film layer, a low emissivity coating, and a hydrophilic nanofiber film layer from bottom to top; The hydrophobic nanofiber film layer is made of a hydrophobic material with low surface binding energy, which includes one or a combination of thermoplastic polyurethane, fluorinated polyurethane, polyvinylidene fluoride, polystyrene or polyethersulfone. The low emissivity coating is prepared from a low emissivity material, which is a two-dimensional Ti3C2T. x Two-dimensional Ti3C2T x The surface groups contain hydrophilic groups, which dynamically adsorb and desorb water molecules, altering the Ti3C2T surface. x The spacing and microstructure between layers; The hydrophilic nanofiber film layer is prepared from a hydrophilic material with high surface binding energy, which includes nylon, polyacrylonitrile, or hydrophilically modified polyethylene.

2. The Janus flexible metafabric with dynamically adjustable infrared emissivity according to claim 1, characterized in that, The low emissivity coating also contains hygroscopic nanofibers, which are cellulose nanofibers.

3. The Janus flexible metafabric with dynamically adjustable infrared emissivity according to claim 1 or 2, characterized in that, The hydrophilic nanofiber film layer also contains optical nanoparticles, which are one or a combination of several of titanium dioxide nanoparticles, zirconium dioxide nanoparticles, alumina nanoparticles, barium sulfate nanoparticles or calcium carbonate nanoparticles, and the particle size of the optical nanoparticles is 100~1000 nm.

4. A method for preparing a Janus flexible metafabric with dynamically adjustable infrared emissivity as described in claim 1, characterized in that, Includes the following steps: Step 1: Preparation of hydrophobic nanofiber thin film layer: The hydrophobic material with low surface binding energy is dissolved in solvent I and stirred thoroughly to obtain a hydrophobic electrospinning solution; the obtained hydrophobic electrospinning solution is electrospinned to form a hydrophobic nanofiber thin film layer, which is then dried for later use. Step 2: Prepare a low emissivity coating: A suspension of low emissivity material is prepared, and a low emissivity coating is coated on the surface of the hydrophobic nanofiber film layer obtained in step one to obtain a bilayer composite film. Step 3: Preparation of hydrophilic nanofiber thin film layer: The hydrophilic material with high surface binding energy is dissolved in solvent II and stirred thoroughly to obtain a hydrophilic electrospinning solution. Using the bilayer composite film obtained in step two as a substrate, the hydrophilic electrospinning solution is electrospinned onto the low emissivity coating surface of the bilayer composite film to form a hydrophilic nanofiber film layer. After drying, a Janus flexible superfabric with a sandwich structure and dynamically regulated infrared emissivity is obtained.

5. The method for preparing Janus flexible metafabric with dynamically adjustable infrared emissivity according to claim 4, characterized in that, The solvent I mentioned in step one is one or a combination of two of N,N-dimethylformamide, dichloromethane, chloroform, acetone or tetrahydrofuran, and the mass ratio of the hydrophobic material with low surface binding energy to solvent I is 1:4~5; the thorough stirring is carried out at 60~100 ℃ and at a stirring speed of 300~800 r / min for not less than 10 h; The electrospinning parameters are as follows: positive voltage 12~16 kV, negative voltage -1 kV, liquid pushing speed 0.02 mm / min, roller speed 300 r / min, needle distance from roller 15 cm, needle lateral translation speed 600 mm / min, spinning environment humidity 60~70%, temperature 30~35 ℃, hydrophobic electrospinning solution volume 1~4 ml, and the thickness of the obtained hydrophobic nanofiber film layer 8~24 μm. The drying process involves vacuum drying at 60-80°C for 1-2 hours.

6. The method for preparing Janus flexible metafabric with dynamically adjustable infrared emissivity according to claim 4 or 5, characterized in that, In step two, the concentration of the low-emissivity material in the suspension is 0.5 to 1.0 mg / ml, and the coating is performed by air spraying, ultrasonic spraying, or vacuum filtration; the thickness of the resulting low-emissivity coating is 2 to 15 μm.

7. The method for preparing Janus flexible metafabric with dynamically adjustable infrared emissivity according to claim 6, characterized in that, The suspension of the low emissivity material described in step two also contains hygroscopic nanofibers, which are cellulose nanofibers, and the mass ratio of the low emissivity material to the hygroscopic nanofibers is 1~7:1~3.

8. The method for preparing the Janus flexible metafabric with dynamically adjustable infrared emissivity according to claim 7, characterized in that, The solvent II mentioned in step three is one or a mixture of formic acid, glacial acetic acid, dichloromethane or trifluoroethanol with a concentration of not less than 88%; the mass ratio of the hydrophilic material with high surface binding energy to solvent II is 1:1~2; the thorough stirring is carried out at room temperature and a stirring speed of 300~800 r / min for not less than 10 h. The electrospinning parameters are as follows: positive voltage 20~26 kV, negative voltage -1 kV, liquid pushing speed 0.026 mm / min, roller speed 300 r / min, needle distance from roller 15 cm, needle lateral translation speed 600 mm / min, spinning environment humidity 60~70%, temperature room temperature, hydrophilic electrospinning solution volume 1~4 ml, and the thickness of the obtained hydrophilic nanofiber film layer 8~65 μm. The drying process involves vacuum drying at 60-80°C for 1-2 hours.

9. The method for preparing the Janus flexible metafabric with dynamically adjustable infrared emissivity according to claim 8, characterized in that, The hydrophilic electrospinning solution described in step three also contains optical nanoparticles, which are one or a combination of titanium dioxide particles, zirconium dioxide particles, aluminum oxide particles, barium sulfate particles or calcium carbonate particles, and the particle size of the optical nanoparticles is 100~1000 nm. The mass ratio of the optical nanoparticles to the hydrophilic material with high surface binding energy is 1~3:5~10.

10. An application of Janus flexible metafabric with dynamically adjustable infrared emissivity as described in any one of claims 1-3 in the fields of intelligent thermal and humidity management, intelligent infrared camouflage and stealth, and intelligent security or anti-counterfeiting.

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