Polarization-controllable color radiation refrigeration metamaterial and preparation method and application thereof

Abstract

The application discloses a radiation cooling metamaterial capable of color display through polarization control, realizes diversified color display and high-efficiency cooling performance, and is composed of two parts, wherein the upper layer is an infrared emitter composed of a silicon dioxide cone and a titanium dioxide / silicon dioxide / PDMS multilayer film, has high emissivity in the atmospheric window of 8-13 microns, and realizes the cooling function; the lower layer is a visible light selective reflector composed of a silver / silicon dioxide multilayer elliptical cylinder and a silver layer, has high visible light reflectivity, and realizes polarization-controllable color display. The design can realize the adjustment of color display in various ways through the adjustment of the structure and the polarization angle, and the average emissivity in the atmospheric window reaches 96.62%, thereby realizing good cooling function. The radiation cooling metamaterial capable of polarization-controllable color display without additional energy source has a wide range of applications and can be effectively applied in the fields of energy-saving buildings, electronic equipment, personal thermal management and the like.

Description

Technical Field

[0001] This invention belongs to the field of radiation cooling technology, and particularly relates to a polarization-controllable color radiation cooling metamaterial, its preparation method, and its application. Background Technology

[0002] Global climate change and energy consumption have become enormous challenges facing humanity, with energy consumption in the cooling process being particularly prominent. Traditional cooling technologies require the consumption of large amounts of fossil fuels, and the resulting large emissions of greenhouse gases exacerbate global warming. Radiative cooling technology, through the permeability of an 8-13 μm atmospheric window, radiates heat into the surrounding space, thereby lowering the temperature without consuming any energy.

[0003] Currently, most radiant coolers are white or silver to achieve strong reflection of solar wavelengths, thus ensuring the highest cooling effect. However, this leads to problems such as light pollution and eye safety, and also has significant application limitations. Therefore, the design of colored radiant coolers can combine cooling function with aesthetic appeal.

[0004] Existing color radiation coolers either use pigments, resulting in weak cooling capacity, or use structural colors, which cannot flexibly change the display color. Polarization-controllable color radiation cooling metamaterials can better solve this problem. Summary of the Invention

[0005] The purpose of this invention is to provide a polarization-controllable color radiation cooling metamaterial, its preparation method, and its application, which can simultaneously achieve efficient cooling and polarization-controlled color display.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A polarization-controllable color radiation-cooled metamaterial includes an infrared emitter on the upper layer and a visible light selective reflector on the lower layer. The infrared emitter is composed of a composite of periodically arranged silicon dioxide conical films, titanium dioxide films, silicon dioxide films, and PDMS films from top to bottom. The visible light selective reflector is composed of a composite of periodically arranged silver elliptical cylinders, periodically arranged silicon dioxide elliptical cylinders, and silver films from top to bottom. The elliptical cylinder structure is to achieve anisotropy of the structure, and the different reflectivities at different polarization angles result in different colors.

[0007] Furthermore, the infrared emitter's period along the x and y axes P 1 =27±0.1μm, radius of the top silica cone r =13±0.1μm, thickness t 1 =10±0.1μm, the thicknesses of the titanium dioxide, silicon dioxide, and PDMS multilayer films are as follows:t 2 =6±0.1μm, t 3 =6±0.1μm, t 4 =7±0.1μm.

[0008] Furthermore, the visible light selective reflector has a period along the x and y axes. P 2 =300±1nm, the major and minor axes of the silver and silicon dioxide multilayer elliptical cylinder are a=30±1nm and b=18±1nm respectively, and the thicknesses are respectively t 5 =15±1nm, t 6 =15±1nm.

[0009] A method for fabricating a polarization-controllable color radiation cooling metamaterial involves firstly depositing silver, silicon dioxide, and silver thin films in an orderly manner using DC magnetron sputtering. Then, silver and silicon dioxide elliptical cylinders are created using photolithography and plasma reactive etching techniques. Next, PDMS is uniformly coated onto the elliptical cylinder units using chemical spin coating. Then, silicon dioxide, titanium dioxide, and silicon dioxide thin films are sequentially deposited using DC magnetron sputtering. Finally, a sacrificial layer is coated on top, and a conical structure is obtained through photolithography and wet etching processes. The conical structure can achieve a higher emissivity in the atmospheric window band to achieve a better cooling effect.

[0010] A polarization-controllable color radiation cooling metamaterial is used in energy-efficient buildings, electronic devices, and personal thermal management.

[0011] The advantages of this invention are: 1. Since the mechanism of polarization controllability lies in the anisotropy of the surface unit structure, different structures in different directions lead to different reflection spectra of polarization changes, thereby realizing polarization-controlled color display. The polarization-controllable color radiation cooling metamaterial of the present invention has an average emissivity of 96.62% in the atmospheric window, which is significantly higher than the conventional 90% emissivity. The main reason is the combination of specific material selection and structural settings in the present invention. The elliptical cylindrical structure realizes the anisotropy of the structure, and the conical structure can achieve a higher emissivity in the atmospheric window band to achieve a better cooling effect. Combined with the inherent absorption of the material in the present invention, the final prepared metamaterial has high visible light reflectivity while realizing polarization-controllable color display. This design can adjust the color display in a variety of ways by adjusting the structure and polarization angle. 2. The polarization-controllable color radiation cooling metamaterial of the present invention has a high emissivity in the atmospheric window of 8-13 micrometers to achieve the cooling function, and can be effectively applied to energy-saving buildings, electronic devices, personal thermal management and other fields. Attached Figure Description

[0012] Figure 1 (a) is a 3D schematic diagram of the polarization-controllable color radiation cooling metamaterial of the present invention; (b) is a top view of the infrared emitter; (c) is a top view of the visible light selective reflector; and (d) is a side view.

[0013] Figure 2 The reflection spectrum (a) of the reflective portion and the emission spectrum (b) of the emitting portion of the polarization-controllable color radiation cooling metamaterial of the present invention are shown. Figure 3 The reflection spectra of the polarization-controllable color radiation cooling metamaterial silver / silica multilayer elliptical cylinder proposed in this invention under different aspect ratios in x-polarization (a), the reflection spectra under different aspect ratios in y-polarization (b), and the reflection spectra of the metamaterial under different polarization angles when the aspect ratio is 0.6 (c); points (d)-(f) on the CIE plot correspond to the reflection spectra of (a)-(c); and the color display corresponding to each reflection spectrum (g).

[0014] Figure 4 The radiation cooling power of the atmospheric window of the polarization-controllable color radiation cooling metamaterial proposed in this invention at different temperatures (a), the solar absorption power and net cooling power of the silver / silica multilayer elliptical cylinder at different aspect ratios (b), and the solar absorption power and net cooling power at different polarization angles when the aspect ratio is 0.6 (c).

[0015] Figure 5 The net cooling power of the polarization-controllable color radiation-cooled metamaterial proposed in this invention under different convection coefficients (a); and the radiation-cooling power and emissivity in the atmospheric window under different incident angles (b). Detailed Implementation Example

[0016] A polarization-controllable color radiation-cooled metamaterial, such as Figure 1As shown, the structure includes an upper infrared emitter and a lower visible light selective reflector. The upper infrared emitter consists of periodically arranged silica cones and a titanium dioxide / silica / PDMS multilayer film. The lower visible light selective reflector consists of periodically arranged silver / silica multilayer elliptical cylinders and a silver layer. The upper and lower layers are combined to form a composite structure. The infrared emitter has a period of P1 = 27 μm along the x and y axes, the top silica cone has a period of r = 13 μm, t1 = 10 μm, and the titanium dioxide / silica / PDMS multilayer film thicknesses are t2 = 6 μm, t3 = 6 μm, and t4 = 7 μm. The visible light selective reflector has a period of P2=300nm along the x and y axes. The major and minor axes of the silver / silicon dioxide multilayer elliptical cylinders are a=30nm and b=18nm, respectively, and the thicknesses are t5=15nm and t6=15nm, respectively. The polarization-controllable color radiation cooling metamaterial of the present invention uses DC magnetron sputtering to orderly deposit silver / silicon dioxide / silver thin films. Then, photolithography and plasma reactive etching techniques are used to create silver / silicon dioxide elliptical cylinders. Next, PDMS is uniformly coated onto the elliptical cylinder units using chemical spin coating. Then, silicon dioxide / titanium dioxide / silicon dioxide thin films are sequentially deposited using DC magnetron sputtering. Finally, a sacrificial layer is coated on the top, and a conical structure is obtained through photolithography and wet etching processes. Figure 2 The results show that there is high reflectance in the visible spectrum and high emission through the atmospheric window, with an average emissivity of 96.62% through the atmospheric window.

[0017] Simulation Experiment The simulation was performed using the three-dimensional finite element multiphysics simulation software COMSOL Multiphysics. The structure of Example 1 was simulated, with a periodic boundary set in the planar direction to represent an infinitely large array structure. A plane electromagnetic wave was incident parallel to the z-axis, and the electric field direction was along the x-axis. Periodic boundary conditions were applied in the x and y-axis directions, and a perfectly matched layer was used in the z-direction to eliminate non-physical reflections at the boundary. The mesh was set to extremely fine, and then frequency domain scans were performed to calculate the absorption results, thereby obtaining the corresponding reflection and emission spectra.

[0018] Furthermore, to investigate the effects of the major and minor axis ratio, polarization, temperature, convection coefficient, and incident angle of the silver / silica multilayer elliptical cylinder on the color radiation cooling metamaterial of this invention, in the simulation experiment, except for the variable parameters, while ensuring that other parameters remained the same as in Example 1, the major and minor axis ratio, polarization angle, temperature, convection coefficient, and incident angle of the silver / silica multilayer elliptical cylinder were changed sequentially. The simulation results are as follows: 1. The Influence of Major and Minor Axis Ratios and Polarization of Silver / Silica Multilayer Elliptical Cylinders on the Visible Light Reflectance Spectrum Figure 3(a) and (b) show the reflection spectra of the polarization-controllable color radiation-cooling metamaterial of this invention under different major-minor axis ratios of the silver / silicon dioxide multilayer elliptical cylinders. As the major-minor axis ratio increases, the valley position of x-polarization shifts towards blue. For y-polarization, as the major-minor axis ratio increases, the valley position shifts towards red, opposite to the x-polarization direction.

[0019] 2. The effect of polarization angle on the visible light reflectance spectrum Figure 3 (c) illustrates the modulation effect of the polarization angle of the polarization-controllable color radiation-cooled metamaterial of this invention on the visible light reflection spectrum. Increasing the polarization angle from 0 degrees to 90 degrees results in a steady decrease in the corresponding 602nm valley value, while the 456nm valley value increases, thereby achieving a change in color display. This demonstrates the highly adjustable polarization controllable characteristic of this structure for color display.

[0020] 3. The effect of temperature on cooling capacity Figure 4 (a) The effect of different temperatures on the radiative cooling power of the polarization-controllable color radiation-cooled metamaterial proposed in this invention on the atmospheric window. The radiative cooling power increases with increasing ambient temperature. At an ambient temperature of 300 K, the radiative cooling power is 190.915 W / m. 2 The atmospheric absorption power is 15.939 W / m. 2 .

[0021] 4. The effect of the major and minor axis ratio of silver / silicon dioxide multilayer elliptical cylinders on solar power absorption and net cooling power. Figure 4 (b) The effect of different aspect ratios on the solar absorption power and net cooling power of the polarization-controllable color radiation cooling metamaterial silver / silica multilayer elliptical cylinder proposed in this invention. When the aspect ratio is 0.4, the absorbed solar energy is 39.759 W / m. 2 The color is pinkish-purple, and the amount of solar energy absorbed gradually increases with the increase of the aspect ratio. When the aspect ratio is 0.8, the absorbed solar energy is 44.358 W / m. 2 The color gradually changed to blue-green; the corresponding net cooling power also increased from 135.216 W / m 2 It decreased to 130.617 W / m 2 .

[0022] 5. The effect of polarization angle on solar absorbed power and net cooling power Figure 4 (c) The effect of the polarization angle of the polarization-controllable color radiation-cooling metamaterial proposed in this invention on the solar absorbed power and net cooling power. The absorbed solar energy initially increases, then decreases, reaching 54.627 W / m at a 45° angle.2 The maximum value is 37.029 W / m at 90°. 2 The minimum value. The corresponding net cooling power is 120.348 W / m. 2 and 137.946 W / m 2 The results show that high cooling performance is maintained even when the color is changed by the polarization angle.

[0023] 6. The effect of convection coefficient and incident angle on cooling power Figure 5 This invention relates to the effect of convection coefficient and incident angle on the cooling capacity of the polarization-controllable color radiation cooling metamaterial. The value of the convection coefficient is inversely proportional to the cooling capacity. As the convection coefficient increases, the radiation power decreases, but when the convection coefficient is 9 W / m... 2 It still possesses cooling capability at / K. With increasing incident angle, the average emissivity and cooling power within the atmospheric window initially decrease, rise slightly at 20 degrees, and then continue to decrease with further increases in the incident angle. At an incident angle of 40 degrees, the emissivity is 93.465%, and the cooling power is 184.681 W / m². 2 Even at an incident angle of 60 degrees, the emissivity remains at 87.851%, and the cooling power is 173.587 W / m. 2 The results demonstrate a high launch capability that adapts to multiple angles.

Claims

1. A polarization-controllable color radiation cooling metamaterial, characterized in that: The system includes an upper infrared emitter and a lower visible light selective reflector. The infrared emitter, from top to bottom, is composed of a composite of periodically arranged silicon dioxide conical films, titanium dioxide films, silicon dioxide films, and PDMS films. The visible light selective reflector, from top to bottom, is composed of a composite of periodically arranged silver elliptical cylindrical films, periodically arranged silicon dioxide elliptical cylindrical films, and silver films. The visible light selective reflector has a periodicity along the x and y axes. P 2 =300±1nm, the major and minor axes of the silver and silicon dioxide multilayer elliptical cylinder are a=30±1nm and b=18±1nm respectively, and the thicknesses are respectively t 5 =15±1nm, t 6 =15±1nm.

2. The polarization-controllable color radiation-cooled metamaterial as described in claim 1, characterized in that: The infrared emitter's period along the x and y axes P 1 =27±0.1μm, radius of the top silica cone r =13±0.1μm, thickness t 1 =10±0.1μm, the thicknesses of the titanium dioxide, silicon dioxide, and PDMS multilayer films are as follows: t 2 =6±0.1μm, t 3 =6±0.1μm, t 4 =7±0.1μm.

3. The method for preparing the polarization-controllable color radiation-cooled metamaterial as described in any one of claims 1-2, characterized in that: First, silver, silicon dioxide, and silver thin films are deposited in an orderly manner using DC magnetron sputtering. Then, silver and silicon dioxide elliptical cylinders are created using photolithography and plasma reactive etching techniques. Next, PDMS is uniformly coated onto the elliptical cylinder units using chemical spin coating. Then, silicon dioxide, titanium dioxide, and silicon dioxide thin films are deposited sequentially using DC magnetron sputtering. Finally, a sacrificial layer is coated on top, and a conical structure is obtained through photolithography and wet etching processes.

4. The polarization-controllable color radiation cooling metamaterial as described in any one of claims 1-2 is used in energy-efficient buildings, electronic devices, and personal thermal management.

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