Nanofiber radiation refrigeration heat insulation film with bionic multilayer structure

Abstract

The invention belongs to the field of composite materials, and particularly relates to a nanofiber radiation refrigeration heat insulation film with a bionic multilayer structure. The device sequentially comprises a bionic anti-reflection layer, a solar spectrum reflection layer, a nanofiber porous heat insulation layer and an atmospheric window radiation layer from outside to inside, the bionic anti-reflection layer is a sub-wavelength nano bulge array simulating a moth eye structure and is formed on the outer surface of the solar spectrum reflecting layer; the solar spectrum reflecting layer is a polymer film doped with high-reflectivity nanoparticles; the nanofiber porous heat insulation layer is a porous membrane formed by interweaving polymer nanofibers prepared by an electrostatic spinning technology; the atmospheric window radiation layer is a functional layer formed by coating or blending high-emissivity inorganic nanoparticles on the inner surface of the nanofiber porous heat insulation layer; the film integrates bionic antireflection, high sunlight reflection, efficient heat radiation and physical heat insulation, and efficient, stable and flexible daytime radiation refrigeration is achieved.

Description

Technical Field

[0001] This invention belongs to the field of composite materials, specifically a biomimetic multilayer nanofiber radiation cooling and heat insulation film. Background Technology

[0002] With the global energy crisis and climate change becoming increasingly severe, developing zero-energy / low-energy active cooling technologies has become one of the key challenges for sustainable development. Against this backdrop, passive daytime radiative cooling (PDRC) technology has emerged, providing a solution for passive, zero-pollution cooling by utilizing the natural heat sink of the "cosmic cold source." Its core physical mechanism lies in the material design that simultaneously possesses two independent spectral characteristics: extremely high reflectivity in the 0.25-2.5 μm solar spectrum band to minimize the input of solar radiation energy; and extremely high emissivity in the 8-13 μm "atmospheric window" band, thereby efficiently dissipating internal heat through the atmosphere in the form of infrared radiation to the near-absolute zero of outer space.

[0003] Although the principles of PDRC technology are clear and its prospects are broad, existing technologies still face a series of severe challenges and limitations in the actual materialization and application process: 1. The dilemma of synergistic performance of spectral properties: Current mainstream PDRC materials, such as randomly distributed microporous polymer films (e.g., PVDF-HFP) or inorganic particle / polymer composite coatings, often struggle to achieve perfect synergy across a wide spectral range. For example, pursuing extremely high solar reflectance (95%) typically requires high concentrations of wide-bandgap inorganic scattering particles (e.g., TiO2). However, these particles may exhibit unnecessary phonon resonance absorption in certain mid-infrared bands, suppressing their ideal emissivity at atmospheric windows. Conversely, some organic polymers with intrinsically high emissivity in the 8-13 μm band often have insufficient solar reflectance. This "seesaw" effect in spectral performance makes it difficult for materials to simultaneously approach the theoretical ideal values ​​of solar reflection and infrared emission, limiting their maximum cooling efficiency.

[0004] 2. The fatal weakness of environmental thermal interference: Most studies focus on the radiation properties of material surfaces, generally neglecting the interference of heat conduction and convection from the environment. When PDRC materials are directly bonded to the protected object (such as building exterior walls, electronic device housings, or tank surfaces), heat from the high-temperature environment is continuously injected into the cooled system through solid conduction and air convection, severely extinguishing or even completely negating its radiative cooling effect. This coexistence of "cooling" and "heating" results in measured cooling effects being far lower than theoretical values ​​in practical applications, especially in high-temperature daytime environments. Therefore, the practical application value of PDRC structures lacking efficient thermal insulation design is greatly reduced.

[0005] 3. Comprehensive test of mechanical properties and durability: For practical applications, PDRC materials must possess excellent mechanical properties and long-term durability. However: Flexibility: Many PDRC materials based on rigid photonic crystals or silicon structures have excellent performance, but they are inherently brittle and cannot be applied to flexible or deformable substrates.

[0006] Strength: Although microporous films prepared by phase separation are flexible, their mechanical strength is often insufficient. They are easily torn and worn, and cannot withstand installation stress or external physical impact.

[0007] Weather resistance: The material needs to be exposed to ultraviolet light, moisture, temperature cycling, and pollutants for extended periods. The polymer matrix may yellow due to ultraviolet radiation (leading to increased solar absorptivity), nanoparticles may be washed away by rainwater, and porous structures may fail due to dust blockage. Current material systems still face significant challenges in balancing high performance and long lifespan.

[0008] 4. Costs and technological barriers to large-scale production: To achieve specific optical structures (such as multilayer photonic crystals and complex micro / nano gratings), cutting-edge micro / nano fabrication technologies such as electron beam lithography and ion etching are often required. While these processes can produce high-performance samples, the equipment is expensive, the procedures are complex, and the yield is extremely low, making them completely unsuitable for large-scale applications such as construction and outdoor equipment. Developing a high-performance PDRC material that is compatible with mature and scalable industrial production processes (such as solution spinning and roll-to-roll coating) is essential for its industrialization and represents a current technological gap and challenge. Summary of the Invention

[0009] To overcome the shortcomings of existing technologies, this invention provides a biomimetic multilayer nanofiber radiative cooling and heat insulation film to address the problems of insufficient spectral performance, susceptibility to environmental thermal interference, and poor mechanical flexibility of existing radiative cooling materials. This film integrates biomimetic antireflection, high solar radiation reflection, efficient thermal radiation, and physical insulation to achieve efficient, stable, and flexible daytime radiative cooling.

[0010] The technical solution adopted by the present invention to solve its technical problem is: the present invention provides a biomimetic multilayer nanofiber radiation cooling and heat insulation film, which, from the outside to the inside, includes: a biomimetic antireflection layer, a solar spectrum reflection layer, a nanofiber porous heat insulation layer, and an atmospheric window radiation layer. The biomimetic antireflective layer is a subwavelength nano-protrusion array that mimics the structure of a moth's eye. It is formed on the outer surface of the solar spectrum reflective layer to reduce the reflection of sunlight and increase broadband antireflective performance. The solar spectrum reflective layer is a polymer film doped with high reflectivity nanoparticles, used for high reflectivity reflection of sunlight in the 250nm-2.5μm wavelength band; The nanofiber porous insulation layer is a porous membrane formed by interwoven polymer nanofibers prepared by electrospinning technology. Its porosity is greater than 80%, which is used to block heat conduction and convection, and allows infrared light in the 8-13μm band to pass through. The atmospheric window radiation layer is a functional layer in which high-emissivity inorganic nanoparticles are coated or blended on the inner surface of a nanofiber porous heat insulation layer, which is used to efficiently emit infrared radiation in the 8-13μm band into the outer space of the atmosphere.

[0011] As a further technical solution of the present invention: the nano-protrusions of the biomimetic antireflective layer are conical or hemispherical, with a diameter of 200-500nm and a height of 300-600nm.

[0012] As a further technical solution of the present invention: the material of the biomimetic antireflective layer is usually composed of a transparent polymer or metal oxide with high refractive index and weather resistance; the thickness of the biomimetic antireflective layer is 200nm-800nm.

[0013] As a further technical solution of the present invention: the solar spectrum reflective layer is composed of inorganic nanoparticles with high refractive index and low absorption uniformly doped into a transparent polymer matrix.

[0014] As a further technical solution of the present invention: the inorganic nanoparticles are selected from one or more of titanium dioxide, zinc oxide, and barium sulfate.

[0015] As a further technical solution of the present invention: the particle size of inorganic nanoparticles is controlled at 50-300nm to minimize Rayleigh scattering; the thickness of the solar spectral reflective layer is usually 10-50μm.

[0016] As a further technical solution of the present invention: the thickness of the nanofiber porous heat insulation layer is 50μm-300μm; the polymer nanofiber is one or more of polyvinylidene fluoride, polyurethane, and polyacrylonitrile; wherein, the diameter of a single fiber is 100-500 nm, the porosity is >80%, and the thickness is 100-500 μm.

[0017] As a further technical solution of the present invention: the high emissivity inorganic nanoparticles are made of one or more of silicon dioxide, silicon carbide, and boron nitride.

[0018] As a further technical solution of the present invention: the thickness of the atmospheric window radiation layer is 10μm-50μm, and the particle size of the high emissivity inorganic nanoparticles is 0.5-5μm.

[0019] As a further technical solution of the present invention: the preparation method of the nanofiber radiation cooling and heat insulation film includes the following steps: Step 1: Using electrospinning technology, a polymer solution containing high emissivity nanoparticles is spun directly onto a cylindrical metal roller with a diameter of 20cm and a length of 30cm to form a composite structure of a nanofiber porous heat insulation layer and an atmospheric window radiation layer, thus obtaining the nanofiber composite lower layer. Step 2: First, a polymer film doped with highly reflective nanoparticles is prepared by casting, stretching or coating to obtain a solar spectrum reflective layer; Then, a biomimetic moth-eye structure is prepared on the surface of the film using nanoimprinting or self-assembly techniques to form a biomimetic composite upper layer. Step 3: The biomimetic composite upper layer and the nanofiber composite lower layer prepared above are laminated together using an environmentally friendly adhesive to obtain the final multilayer composite heat insulation film.

[0020] The beneficial effects of this invention are as follows: This invention introduces a moth-eye-like nanostructure as the outermost layer. The function of this structure is not simply to increase light transmittance, but rather to significantly reduce surface reflection loss through the principle of gradient refractive index, allowing more sunlight to enter the internal reflective layer and be efficiently reflected. This strategy of achieving enhanced reflection through reduced reflection optimizes the overall solar reflection efficiency from an optical perspective.

[0021] This invention uses an electrospun nanofiber membrane as the intermediate layer. Its high porosity gives it an extremely low thermal conductivity, while its polymer fiber skeleton is highly transparent to infrared light in the 8-13μm wavelength band; making it a functional transmission channel that is both heat-insulating and infrared-transmitting, isolating the lower layer's radiative cooling from the upper layer's external environment, ensuring that the radiative cooling effect is not affected by environmental heat.

[0022] This invention achieves a highly efficient, stable, and practical daytime radiation cooling and heat insulation film through a biomimetic antireflective layer (antireflective layer), a solar reflective layer (reflection), a nanofiber heat insulation layer (heat insulation / transmission), and an atmospheric window radiation layer (emission).

[0023] This invention employs a unique four-layer structure, which generates three major physical effects: high reflection, high radiation, and high heat insulation, thereby converging into the advantages of efficient, stable, and zero-energy-consumption cooling. Attached Figure Description

[0024] The invention will now be further described with reference to the accompanying drawings.

[0025] Figure 1 This is a schematic diagram of the structure of a biomimetic multilayer nanofiber radiation cooling and heat insulation film of the present invention; In the diagram: 10, biomimetic antireflective layer; 20, solar spectrum reflective layer; 30, nanofiber porous heat insulation layer; 40, atmospheric window radiation layer. Detailed Implementation

[0026] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0027] Example 1

[0028] like Figure 1 As shown in the embodiment of the present invention, a biomimetic multilayer nanofiber radiation cooling and heat insulation film includes, from the outside to the inside: a biomimetic antireflective layer 10, a solar spectrum reflective layer 20, a nanofiber porous heat insulation layer 30, and an atmospheric window radiation layer 40. The biomimetic antireflective layer 10 is a subwavelength nano-protrusion array that mimics the structure of a moth's eye. It is formed on the outer surface of the solar spectrum reflective layer 20 to reduce the reflection of sunlight and increase broadband antireflective performance. The thickness of the biomimetic antireflective layer 10 is 200 nm. Specifically, the nano-protrusions of the biomimetic antireflection layer 10 are conical or hemispherical, with a diameter of 200 nm and a height of 300 nm; The biomimetic antireflective layer 10 is typically made of a high-refractive-index, weather-resistant transparent polymer (such as a UV-curable resin) or a metal oxide (such as TiO2); the mass ratio of the weather-resistant transparent polymer to the metal oxide is 100:5. Among them, the subwavelength nano-protrusion array that mimics the structure of a moth's eye is used to reduce the surface reflectivity of sunlight in the solar spectrum (especially visible and near-infrared light), increase the incident light, and thus indirectly improve the overall structure's ability to reflect sunlight.

[0029] The solar spectrum reflective layer 20 is a polymer film doped with high reflectivity nanoparticles, used for high reflectivity reflection of sunlight in the 250nm wavelength band; Specifically, the solar spectral reflective layer 20 is composed of a transparent polymer matrix (such as PET) uniformly doped with inorganic nanoparticles with high refractive index and low absorption; the mass ratio of the transparent polymer matrix to the inorganic nanoparticles is 100:5. Among them, the inorganic nanoparticles are selected from one or more of titanium dioxide (TiO2), zinc oxide (ZnO), and barium sulfate (BaSO4); the particle size is controlled at 50nm to minimize Rayleigh scattering; the thickness of the solar spectral reflective layer 20 is usually 10μm.

[0030] It should be noted that the solar spectral reflective layer 20, as the core reflective unit, provides high reflectivity across almost the entire spectrum of sunlight in the 250nm-2.5μm band (target > 92%), minimizing the absorption of solar radiation energy.

[0031] The nanofiber porous heat insulation layer 30 is a porous membrane formed by interwoven polymer nanofibers prepared by electrospinning technology. Its porosity is greater than 80%, which is used to block heat conduction and convection, and allows infrared light in the 8-13μm band to pass through; the thickness of the nanofiber porous heat insulation layer 30 is 50μm. Specifically, the polymer nanofibers prepared by electrospinning technology form a three-dimensional network structure through interweaving; the polymer nanofibers are made of polyvinylidene fluoride (PVDF) and the like; each fiber has a diameter of 100 nm, a porosity of 85%, and a thickness of 100 μm.

[0032] It should be noted that the nanofiber porous insulation layer 30 effectively blocks heat conduction and convection from the external environment through the large number of micron and nano-sized pores inside it; since the intrinsic vibration absorption peak of the polymer that makes up the nanofiber is usually not in the 8-13μm band, the layer is highly transparent to infrared radiation in this band, allowing the radiation from the inner layer to pass through unimpeded. The atmospheric window radiation layer 40 is a functional layer in which high emissivity inorganic nanoparticles are coated or blended on the inner surface of the nanofiber porous heat insulation layer 30, for efficiently emitting infrared radiation in the 8-13μm band into the outer space of the atmosphere; the thickness of the atmospheric window radiation layer 40 is 10μm.

[0033] Specifically, the high-emissivity inorganic nanoparticles are made of silicon dioxide (SiO2). These materials exhibit intrinsically high emissivity >0.9 in the 8-13 μm wavelength range; particle size: 0.5 μm, to ensure effective infrared emission; It should be noted that the atmospheric window radiation layer 40 is made of high emissivity inorganic nanoparticles that are firmly attached to the lower surface (or the entire skeleton) of the nanofiber porous heat insulation layer 30 through coating, impregnation or blending. As the core cooling unit, it efficiently emits infrared radiation in the 8-13 μm band and dissipates heat directly into the cold outer space through the atmospheric window.

[0034] Example 2

[0035] The biomimetic multilayer nanofiber radiation cooling and heat insulation film of the present invention comprises, from the outside to the inside: a biomimetic antireflection layer 10, a solar spectrum reflection layer 20, a nanofiber porous heat insulation layer 30, and an atmospheric window radiation layer 40. The biomimetic antireflective layer 10 is a subwavelength nano-protrusion array that mimics the structure of a moth's eye. It is formed on the outer surface of the solar spectrum reflective layer 20 to reduce the reflection of sunlight and increase broadband antireflective performance. The thickness of the biomimetic antireflective layer 10 is 500 nm. Specifically, the nano-protrusions of the biomimetic antireflection layer 10 are conical or hemispherical, with a diameter of 350 nm and a height of 450 nm; The biomimetic antireflective layer 10 is typically made of a high-refractive-index, weather-resistant transparent polymer (such as a UV-curable resin) or a metal oxide (such as TiO2, Si3N4); the mass ratio of the weather-resistant transparent polymer to the metal oxide is 100:30. Among them, the subwavelength nano-protrusion array that mimics the structure of a moth's eye is used to reduce the surface reflectivity of sunlight in the solar spectrum (especially visible and near-infrared light), increase the incident light, and thus indirectly improve the overall structure's ability to reflect sunlight.

[0036] The solar spectral reflective layer 20 is a polymer film doped with high reflectivity nanoparticles, used for high reflectivity reflection of sunlight in the 1.0 μm band; Specifically, the solar spectral reflective layer 20 is composed of a transparent polymer matrix (such as TPU) uniformly doped with inorganic nanoparticles with high refractive index and low absorption; the mass ratio of the transparent polymer matrix to the inorganic nanoparticles is 100:40. Among them, the inorganic nanoparticles are selected from one or more of titanium dioxide (TiO2), zinc oxide (ZnO), and barium sulfate (BaSO4); the particle size is controlled at 150 nm to minimize Rayleigh scattering; the thickness of the solar spectral reflective layer 20 is usually 30 μm.

[0037] It should be noted that the solar spectral reflective layer 20, as the core reflective unit, provides high reflectivity across almost the entire spectrum of sunlight in the 250nm-2.5μm band (target > 92%), minimizing the absorption of solar radiation energy.

[0038] The nanofiber porous heat insulation layer 30 is a porous membrane formed by interwoven polymer nanofibers prepared by electrospinning technology. Its porosity is greater than 80%, which is used to block heat conduction and convection, and allows infrared light in the 8-13μm band to pass through; the thickness of the nanofiber porous heat insulation layer 30 is 50μm-300μm. Specifically, a three-dimensional network structure is formed by interwoven polymer nanofibers prepared by electrospinning technology; the polymer nanofibers are made of polyurethane (PU); wherein, the diameter of a single fiber is 300 nm, the porosity is >88%, and the thickness is 300 μm.

[0039] It should be noted that the nanofiber porous insulation layer 30 effectively blocks heat conduction and convection from the external environment through the large number of micron and nano-sized pores inside it; since the intrinsic vibration absorption peak of the polymer that makes up the nanofiber is usually not in the 8-13μm band, the layer is highly transparent to infrared radiation in this band, allowing the radiation from the inner layer to pass through unimpeded. The atmospheric window radiation layer 40 is a functional layer with high emissivity inorganic nanoparticles coated or blended on the inner surface of the nanofiber porous heat insulation layer 30. It is used to efficiently emit infrared radiation in the 8-13μm band into the outer space of the atmosphere. The thickness of the atmospheric window radiation layer 40 is 30μm. Specifically, the high-emissivity inorganic nanoparticles are made of silicon carbide (SiC). These materials exhibit intrinsically high emissivity >0.9 in the 8-13 μm wavelength range; particle size: 2.5 μm, to ensure effective infrared emission; It should be noted that the atmospheric window radiation layer 40 is made of high emissivity inorganic nanoparticles that are firmly attached to the lower surface (or the entire skeleton) of the nanofiber porous heat insulation layer 30 through coating, impregnation or blending. As the core cooling unit, it efficiently emits infrared radiation in the 8-13 μm band and dissipates heat directly into the cold outer space through the atmospheric window.

[0040] Example 3

[0041] The biomimetic multilayer nanofiber radiation cooling and heat insulation film of the present invention comprises, from the outside to the inside: a biomimetic antireflection layer 10, a solar spectrum reflection layer 20, a nanofiber porous heat insulation layer 30, and an atmospheric window radiation layer 40. The biomimetic antireflective layer 10 is a subwavelength nano-protrusion array that mimics the structure of a moth's eye. It is formed on the outer surface of the solar spectrum reflective layer 20 to reduce the reflection of sunlight and increase broadband antireflective performance. The thickness of the biomimetic antireflective layer 10 is 800 nm. Specifically, the nano-protrusions of the biomimetic antireflection layer 10 are conical or hemispherical, with a diameter of 500 nm and a height of 600 nm; The biomimetic antireflective layer 10 is typically made of a high-refractive-index, weather-resistant transparent polymer (such as a UV-curable resin) or a metal oxide (such as TiO2, Si3N4); the mass ratio of the weather-resistant transparent polymer to the metal oxide is 100:60. Among them, the subwavelength nano-protrusion array that mimics the structure of a moth's eye is used to reduce the surface reflectivity of sunlight in the solar spectrum (especially visible and near-infrared light), increase the incident light, and thus indirectly improve the overall structure's ability to reflect sunlight.

[0042] The solar spectral reflective layer 20 is a polymer film doped with high reflectivity nanoparticles, used for high reflectivity reflection of sunlight in the 250nm-2.5μm wavelength band; Specifically, the solar spectral reflective layer 20 is composed of a transparent polymer matrix (such as PVDF) uniformly doped with inorganic nanoparticles with high refractive index and low absorption; the mass ratio of the transparent polymer matrix to the inorganic nanoparticles is 100:80. Among them, the inorganic nanoparticles are selected from barium sulfate (BaSO4); the particle size is controlled at 300 nm to minimize Rayleigh scattering; the thickness of the solar spectral reflective layer 20 is typically 50 μm.

[0043] It should be noted that the solar spectral reflective layer 20, as the core reflective unit, provides high reflectivity across almost the entire spectrum of sunlight in the 250nm-2.5μm band (target > 92%), minimizing the absorption of solar radiation energy.

[0044] The nanofiber porous heat insulation layer 30 is a porous membrane formed by interwoven polymer nanofibers prepared by electrospinning technology. Its porosity is greater than 80%, which is used to block heat conduction and convection, and allows infrared light in the 8-13μm band to pass through; the thickness of the nanofiber porous heat insulation layer 30 is 300μm. Specifically, a three-dimensional network structure is formed by interwoven polymer nanofibers prepared by electrospinning technology; the polymer nanofibers are polyacrylonitrile (PAN); wherein, the diameter of a single fiber is 500 nm, the porosity is >80%, and the thickness is 500 μm.

[0045] It should be noted that the nanofiber porous insulation layer 30 effectively blocks heat conduction and convection from the external environment through the large number of micron and nano-sized pores inside it; since the intrinsic vibration absorption peak of the polymer that makes up the nanofiber is usually not in the 8-13μm band, the layer is highly transparent to infrared radiation in this band, allowing the radiation from the inner layer to pass through unimpeded. The atmospheric window radiation layer 40 is a functional layer with high emissivity inorganic nanoparticles coated or blended on the inner surface of the nanofiber porous heat insulation layer 30. It is used to efficiently emit infrared radiation in the 8-13μm band into the outer space of the atmosphere. The thickness of the atmospheric window radiation layer 40 is 50μm. Specifically, the high-emissivity inorganic nanoparticles are boron nitride (BN). These materials exhibit intrinsically high emissivity >0.9 in the 8-13 μm wavelength range; particle size: 5 μm, to ensure effective infrared emission; It should be noted that the atmospheric window radiation layer 40 is made of high emissivity inorganic nanoparticles that are firmly attached to the lower surface (or the entire skeleton) of the nanofiber porous heat insulation layer 30 through coating, impregnation or blending. As the core cooling unit, it efficiently emits infrared radiation in the 8-13 μm band and dissipates heat directly into the cold outer space through the atmospheric window.

[0046] Example 4

[0047] The method for preparing a biomimetic multilayer nanofiber radiation cooling and heat insulation film according to an embodiment of the present invention includes the following steps: Step 1: Using electrospinning technology, a polymer solution containing high emissivity nanoparticles (such as SiO2) is spun directly onto a cylindrical metal roller with a diameter of 20cm and a length of 30cm to form a composite structure of a nanofiber porous heat insulation layer 30 and an atmospheric window radiation layer 40, thus obtaining the nanofiber composite lower layer.

[0048] Step 2: First, a polymer film doped with high-reflectivity nanoparticles is prepared by casting, stretching or coating to obtain a solar spectral reflective layer 20.

[0049] Then, a biomimetic moth-eye structure (i.e., biomimetic antireflective layer 10) is prepared on the surface of the film using nanoimprinting or self-assembly techniques, forming a biomimetic composite upper layer.

[0050] Step 3: The biomimetic composite upper layer and the nanofiber composite lower layer prepared above are laminated together using an environmentally friendly adhesive to obtain the final multilayer composite heat insulation film.

[0051] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A biomimetic multilayer nanofiber radiation cooling and heat insulation film, characterized in that: From the outside to the inside, it includes: a biomimetic anti-reflection layer (10), a solar spectrum reflective layer (20), a nanofiber porous heat insulation layer (30), and an atmospheric window radiation layer (40). The biomimetic antireflective layer (10) is a subwavelength nano-protrusion array that mimics the structure of a moth's eye. It is formed on the outer surface of the solar spectrum reflective layer (20) to reduce the reflection of sunlight and increase the antireflective performance of a wide band. The solar spectrum reflective layer (20) is a polymer film doped with high reflectivity nanoparticles, used for high reflectivity reflection of sunlight in the 250nm-2.5μm band; The nanofiber porous heat insulation layer (30) is a porous membrane formed by interwoven polymer nanofibers prepared by electrospinning technology. Its porosity is greater than 80%, which is used to block heat conduction and convection and allows infrared rays in the 8-13μm band to pass through. The atmospheric window radiation layer (40) is a functional layer with high emissivity inorganic nanoparticles coated or blended on the inner surface of the nanofiber porous heat insulation layer (30) for emitting infrared radiation in the 8-13μm band to the outer space of the atmosphere.

2. The biomimetic multilayer nanofiber radiation cooling and heat insulation film according to claim 1, characterized in that: The nanoprotrusions of the biomimetic antireflective layer (10) are conical or hemispherical, with a diameter of 200-500 nm and a height of 300-600 nm.

3. The biomimetic multilayer nanofiber radiation cooling and heat insulation film according to claim 2, characterized in that: The biomimetic antireflective layer (10) is usually made of a transparent polymer or metal oxide with high refractive index and weather resistance; the thickness of the biomimetic antireflective layer (10) is 200nm-800nm.

4. The biomimetic multilayer nanofiber radiation cooling and heat insulation film according to claim 1, characterized in that: The solar spectral reflective layer (20) is composed of inorganic nanoparticles with high refractive index and low absorption uniformly doped into a transparent polymer matrix.

5. The biomimetic multilayer nanofiber radiation cooling and heat insulation film according to claim 4, characterized in that: The inorganic nanoparticles are selected from one or more of titanium dioxide, zinc oxide, and barium sulfate.

6. The biomimetic multilayer nanofiber radiation cooling and heat insulation film according to claim 5, characterized in that: The particle size of the inorganic nanoparticles is controlled at 50-300 nm to minimize Rayleigh scattering; the thickness of the solar spectral reflective layer (20) is typically 10-50 μm.

7. The biomimetic multilayer nanofiber radiation cooling and heat insulation film according to claim 6, characterized in that: The thickness of the nanofiber porous insulation layer (30) is 50μm-300μm; the polymer nanofibers are one or more of polyvinylidene fluoride, polyurethane, and polyacrylonitrile; wherein, the diameter of a single fiber is 100-500 nm, the porosity is >80%, and the thickness is 100-500μm.

8. The biomimetic multilayer nanofiber radiation cooling and heat insulation film according to claim 7, characterized in that: High-emissivity inorganic nanoparticles are made of one or more of silicon dioxide, silicon carbide, and boron nitride.

9. The biomimetic multilayer nanofiber radiation cooling and heat insulation film according to claim 8, characterized in that: The atmospheric window radiation layer (40) has a thickness of 10μm-50μm, and the particle size of the high emissivity inorganic nanoparticles is 0.5-5μm.

10. The biomimetic multilayer nanofiber radiation cooling and heat insulation film according to claim 1, characterized in that: The preparation method of this nanofiber radiation cooling and heat insulation film includes the following steps: Step 1: Using electrospinning technology, a polymer solution containing high emissivity nanoparticles is spun and directly formed on a cylindrical metal roller with a diameter of 20cm and a length of 30cm to form a composite structure of a nanofiber porous heat insulation layer (30) and an atmospheric window radiation layer (40), thus obtaining the nanofiber composite lower layer. Step 2: First, a polymer film doped with high-reflectivity nanoparticles is prepared by casting, stretching or coating to obtain a solar spectral reflective layer (20). Then, a biomimetic moth-eye structure is prepared on the surface of the film using nanoimprinting or self-assembly techniques to form a biomimetic composite upper layer. Step 3: The biomimetic composite upper layer and the nanofiber composite lower layer prepared above are laminated together using an environmentally friendly adhesive to obtain the final multilayer composite heat insulation film.

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