Bionic passive radiative cooling water-collecting foam material, construction method and application

Abstract

The present application relates to a kind of bionic passive radiative refrigeration water-collecting foam material, construction method and application, belong to the processing technical field of radiative refrigeration material.The main body of the foam material is thermoplastic polymer, and dielectric particles are blended in the thermoplastic polymer;The foam material has interconnected microporous structure inside, and the surface has micron structure array;The surface of the micron structure array has the micro-nano structure formed by the dielectric particles after fluorination modification.The bionic foam material of the present application introduces micropore and dielectric particles inside, constructs ellipsoidal structure array and micro-nano structure on surface, can effectively improve the light reflectivity and emissivity of foam material, reduce the surface temperature of foam material to close or lower than dew point, improve refrigeration efficiency, promote nucleation and condensation of small water droplets.The micron structure array (ellipsoidal structure array) and micro-nano structure on the surface of the foam material promote the material to exhibit macro petal effect, realize the quantitative transport of surface water droplets, and improve the water-collecting performance of the material.

Description

Technical Field

[0001] This invention belongs to the field of radiation cooling material processing technology, and more specifically, relates to a biomimetic passive radiation cooling water collection foam material, its construction method and application. Background Technology

[0002] Since the beginning of the 21st century, the importance of freshwater resources has become undeniable, impacting all aspects of daily life and industrial production. However, global freshwater reserves are limited and unevenly distributed in time and space. Ensuring a secure freshwater supply has become a crucial prerequisite for normal production and daily life, as well as for sustainable social and economic development. Atmospheric water is a ubiquitous and relatively abundant freshwater resource. How to collect and utilize atmospheric water has become an important direction for solving the world's freshwater resource problem. Based on this, existing research includes: increasing the gas-solid contact area to condense and collect larger-scale droplets (such as the condensation water collection system disclosed in Chinese patent application CN202210079839.3); introducing highly absorbent materials to collect water vapor under natural photothermal evaporation (such as the composite hygroscopic material disclosed in Chinese patent application CN202310006825.3); and imparting differentiated wettability to control the condensation and movement behavior of water droplets (such as the condensation coating disclosed in Chinese patent application CN202210548025.X). However, these researches still suffer from problems such as narrow applicability of materials, high energy consumption, difficulty in industrial production, low water collection efficiency, and difficulty in long-term service. Summary of the Invention

[0003] To address the problems of low material efficiency, narrow applicability, and significant environmental impact in existing atmospheric water harvesting and utilization technologies, this invention aims to provide a biomimetic passive radiative cooling water-collecting foam material and its construction method. The foam material is primarily composed of a thermoplastic polymer, with dielectric particles interspersed within it. The foam material has an internal interconnected microporous structure and a surface array of micron-sized structures. The surface of the micron-sized structure array features micro / nano structures formed by fluorinated and modified dielectric particles. In this invention, the internal microporous structure and surface micro / nano structures of the foam material effectively improve its light reflectivity and emissivity, enhancing radiative cooling efficiency and keeping the material's surface temperature below the dew point. Furthermore, the surface micro / nano structures increase the interfacial contact area between the material and air, providing more attachment sites for tiny water droplets. The overall hydrophobic "petal effect" facilitates water droplet nucleation and quantitative transport, significantly improving water collection efficiency. This foam material can be applied in domestic water collection, industrial metallurgy, aerospace, equipment cooling, scientific research, and agricultural irrigation.

[0004] According to a first aspect of the present invention, a foam material is provided, wherein the main body of the foam material is a thermoplastic polymer, and dielectric particles are mixed in the thermoplastic polymer; the interior of the foam material has a connected microporous structure, and the surface of the foam material has a micron structure array; the surface of the micron structure array has a micro-nano structure formed by fluorinated modified dielectric particles.

[0005] Preferably, the size of the microporous structure is 0.5–30 μm;

[0006] The density of the microstructure array is 5–20 units / mm. 2 The height is 100–400 μm and the diameter is 100–500 μm;

[0007] The dimensions of the micro / nano structures range from 0.1 to 20 μm.

[0008] Preferably, the thermoplastic polymer is one or more of polylactic acid, polyurethane, polystyrene, polyvinyl chloride, polyethylene, phenolic resin, ABS resin, polypropylene, polyvinylidene fluoride, polymethyl methacrylate, polycarbonate, polyethylene terephthalate, polytetrafluoroethylene, polyoxymethylene, polyamide, polyphenylene ether, polysulfone, polybutylene terephthalate, and polyphenylene sulfide.

[0009] The dielectric particles are one or more of the following: barium sulfate, calcium carbonate, silicon dioxide, titanium dioxide, zirconium dioxide, boron nitride, silicon carbide, aluminum oxide, titanium oxide, hafnium dioxide, zinc sulfide, barium sulfide, silicon nitride, silicate glass microspheres, aluminosilicate ceramic microspheres, and polymer / inorganic composite microspheres.

[0010] According to another aspect of the present invention, a method for constructing any one of the foam materials is provided, comprising the following steps:

[0011] (1) After the thermoplastic polymer is melt-blended with dielectric particles and soluble particles, it is injected into the mold cavity with a micron structure array template fixed at the bottom. After the melt completely fills the surface of the micron structure array template, a polymer plate with a micron structure array on the surface is obtained.

[0012] (2) Peel the micron structure array template from the surface of the polymer sheet, place the peeled polymer sheet in water and stir or sonicate it to dissolve the soluble particles, and obtain a foam material with a micron structure array on the surface and a connected microporous structure inside.

[0013] (3) The fluorinated modified dielectric particles are mixed with polydimethylsiloxane to prepare a coating, which is then uniformly sprayed onto the surface of the foam material obtained in step (2) which has a micron structure array on the surface and a connected microporous structure inside. The foam material is then irradiated with ultraviolet light to form a micro-nano structure on the surface of the micron structure array of the fluorinated modified dielectric particles, thus obtaining the foam material.

[0014] Preferably, the dielectric particles are one or more of barium sulfate, calcium carbonate, silicon dioxide, titanium dioxide, zirconium dioxide, boron nitride, silicon carbide, alumina, titanium oxide, hafnium dioxide, zinc sulfide, barium sulfide, silicon nitride, silicate glass microspheres, aluminosilicate ceramic microspheres, and polymer / inorganic composite microspheres; the soluble particles are one or more of sodium sulfate, potassium sulfate, sodium chloride, potassium chloride, sodium carbonate, potassium carbonate, magnesium chloride, sugar particles, polyethylene glycol, polyethylene oxide, polyacrylic acid, polyacrylamide, and polyvinyl alcohol; the melt blending method is two-roll blending, internal mixing, open milling, or extrusion.

[0015] Preferably, the sugar granules are glucose, sucrose, or soluble starch.

[0016] Preferably, in step (2), the peeling method is as follows: using clamps to hold the micron structure array template and the polymer plate respectively, and peeling the micron structure array template from the surface of the polymer plate under external force.

[0017] Preferably, the peeling temperature is 30–100°C, the traction angle is less than or equal to 90°, the traction force is 5–50N, and the traction speed is less than or equal to 50mm / min; the ultrasonic treatment time is 2–5h.

[0018] Preferably, the fluorination-modifying agent is at least one selected from perfluorooctyltriethoxysilane, trifluoromethyltrimethylsilane, methyl trifluoroacetate, methyl fluorosulfonyl difluoroacetate, (difluoromethyl)trimethylsilane, and bis(2-methoxyethyl)aminosulfonium trifluoride.

[0019] Preferably, in step (3), the mass percentage of polydimethylsiloxane in the coating is 60% to 90%;

[0020] The intensity of the ultraviolet light is 500–1000 W / m. 2 The irradiation angle is 30° to 90° and the irradiation time is 30 to 120 minutes.

[0021] According to another aspect of the present invention, the application of the foam material described in any one of the claims in passive radiative cooling water collection is provided.

[0022] In summary, compared with the prior art, the above-described technical solutions conceived by this invention mainly possess the following technical advantages:

[0023] (1) The unique micron-structure array (ellipsoidal structure) on the skin surface of the puji tiger, which lives in the harsh climate of the Namib Desert, can collect moisture contained in the sea breeze. Introducing the water-collecting behavior and surface structure of the puji tiger into the design of water-collecting foam materials can not only promote the material surface temperature to approach or drop below the dew point, causing a large number of tiny water droplets to nucleate and condense, but also quantitatively transport larger water droplets under the action of the surface micron-structure array (ellipsoidal structure), realizing passive water collection, improving water collection efficiency, and providing a new idea for solving the freshwater resource crisis.

[0024] (2) The biomimetic foam material of the present invention, by introducing micropores and dielectric particles internally and constructing an ellipsoidal array and micro / nano structure on the surface, can effectively improve the light reflectivity and emissivity of the foam material, improve the radiation cooling efficiency, reduce the surface temperature of the foam material to near or below the dew point, improve the cooling efficiency, and promote the nucleation and condensation of tiny water droplets. In addition, the internal dielectric particles play a role in improving the light reflectivity and emissivity of the foam material, and the surface dielectric particles (such as titanium dioxide) have enhanced wettability after irradiation. The surface micro / nano structure increases the interfacial contact area between the material and the air, providing more attachment sites for tiny water droplets, causing the superhydrophobic surface of the material to exhibit point-like hydrophilic properties, thereby making the material exhibit a hydrophobic "petal effect" as a whole, which is conducive to water droplet nucleation and quantitative transport, and significantly improves the water collection efficiency.

[0025] (3) The equipment used in this invention to prepare biomimetic passive radiation cooling foam material is a commonly used melt blending, molding, ultrasonic, and spraying device. The biomimetic structural template can be reused repeatedly, making it easy to achieve continuous, batch, and low-cost manufacturing, with broad application prospects.

[0026] (4) The biomimetic passive radiative cooling foam material of this invention overcomes the dependence of traditional water collection materials on a cold source, improves the passive water collection performance of polymer materials, and expands the application range of polymer water collection materials. This foam material exhibits good cooling and water collection effects in environments such as forests, lakes, grasslands, and deserts. In grassland environments with a relative humidity ≥90%, the average surface temperature of the foam material is at least 2.5℃ lower than the average ambient temperature, and the water collection efficiency is at least 25g / m³. 2 h. Attached Figure Description

[0027] Figure 1 The image shows scanning electron microscope (SEM) images of the polymer sheets and products during the preparation process of the thermoplastic foam material in Comparative Example 1.

[0028] Figure 2 The contact angle of a 10 μL water droplet on the surface of the thermoplastic foam material in Comparative Example 1.

[0029] Figure 3This is a photograph of the biomimetic passive radiation cooling water collection foam material of Example 1.

[0030] Figure 4 This is a scanning electron microscope image of the cross-section of the biomimetic passive radiation cooling water collection foam material of Example 1.

[0031] Figure 5 This is a scanning electron microscope image of the surface of the biomimetic passive radiation cooling water collection foam material of Example 1.

[0032] Figure 6 This is a schematic diagram of the construction of the biomimetic passive radiation cooling water collection foam material in Example 1.

[0033] Figure 7 This is a scanning electron microscope image of the surface of the biomimetic microstructure array template of Example 1.

[0034] Figure 8 Photographs showing the contact angle of a 10 μL water droplet on the surface of the biomimetic passive radiation cooling water-collecting foam material of Example 1. Graphs showing the test results of the contact angle and roll-off angle of water droplets of different sizes on the foam material surface.

[0035] Figure 9 This is a photograph of the process by which tiny water droplets on the surface of the biomimetic passive radiation cooling water-collecting foam material of Example 1 converge to form large water droplets.

[0036] Figure 10 These are the reflection and emission spectra of the biomimetic passive radiation cooling water-collecting foam material of Example 1.

[0037] Figure 11 The graph shows the test results of the surface temperature, dew point, relative humidity, ambient temperature, and water collection efficiency of the biomimetic passive radiative cooling water collection foam material of Example 1 when applied to outdoor water collection.

[0038] Figure 12 This is a scanning electron microscope image of the cross-section of the biomimetic passive radiation cooling water collection foam material of Example 2.

[0039] Figure 13 This is a scanning electron microscope image of the surface of the biomimetic passive radiation cooling water collection foam material of Example 2.

[0040] Figure 14 The image shows scanning electron microscope (SEM) images of the surface and cross-section of the biomimetic passive radiation cooling water-collecting foam material of Example 3. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0042] This invention discloses a biomimetic passive radiative cooling water collection foam material. The foam material is one or more of the following: polylactic acid, polyurethane, polystyrene, polyvinyl chloride, polyethylene, phenolic resin, ABS resin, polypropylene, polyvinylidene fluoride, polymethyl methacrylate, polycarbonate, polyethylene terephthalate, polytetrafluoroethylene, polyoxymethylene, polyamide, polyphenylene ether, polysulfone, polybutylene terephthalate, and polyphenylene sulfide. The biomimetic foam material has an interconnected microporous structure with a diameter of 0.5–30 μm. The surface of the foam material has an ellipsoidal structure array, which is uniformly distributed with a density of 5–20 ellipsoids / mm². 2 The height is 100–400 μm and the diameter is 100–500 μm. The surface of the ellipsoidal structure array has micro-nano structures, which are uniformly distributed and have a scale of 0.1–20 μm.

[0043] The present invention discloses a method for constructing a biomimetic passive radiative cooling water-collecting foam material, comprising the following steps:

[0044] S1: After the thermoplastic polymer is melt-blended with dielectric particles and soluble particles, it is injected into the mold cavity with a biomimetic micron structure array template fixed at the bottom. After the melt completely fills the surface of the biomimetic micron structure array template, a polymer plate with a biomimetic micron structure array on the surface is obtained.

[0045] S2: Using clamps to hold the biomimetic micron structure array template and the polymer sheet respectively, the biomimetic micron structure array template is peeled off from the surface of the polymer sheet under external force traction. The peeled polymer sheet is placed in distilled water for ultrasonic treatment to obtain foam material.

[0046] S3: Fluorinated dielectric particles are mixed with PDMS to prepare a coating, which is then uniformly sprayed onto the surface of a foam material with an ellipsoidal structure array and irradiated with ultraviolet light to obtain the biomimetic passive radiation cooling water collection foam material.

[0047] Preferably, the dielectric particles can be one or more of barium sulfate, calcium carbonate, silicon dioxide, titanium dioxide, zirconium dioxide, boron nitride, silicon carbide, alumina, titanium oxide, hafnium dioxide, zinc sulfide, barium sulfide, silicon nitride, silicate glass microspheres, aluminosilicate ceramic microspheres, and polymer-inorganic composite microspheres, with a particle size of 0.1–20 μm; the soluble particles can be one or more of sodium sulfate, potassium sulfate, sodium chloride, potassium chloride, sodium carbonate, potassium carbonate, magnesium chloride, sugar particles (such as glucose, sucrose, soluble starch, etc.), polyethylene glycol, polyethylene oxide, polyacrylic acid, polyacrylamide, and polyvinyl alcohol, with a mesh size of 300–7000 mesh; the thermoplastic polymer, dielectric particles, and soluble particles can be melt-blended using methods such as two-roll milling, internal mixing, open milling, and extrusion; the template raw material can be a metal plate (such as aluminum, copper, stainless steel, nickel) or a non-metal plate (such as silicon dioxide);

[0048] Preferably, the peeling temperature of the biomimetic micron-structure array template peeling off from the surface of the polymer sheet is 30-100℃, the traction force is 5-50N, the traction angle is 0°-90°, and the traction speed is 0-50mm / min; the ultrasonic treatment time is 0.5-5h.

[0049] Preferably, the fluorination modifier can be perfluorooctyltriethoxysilane, trifluoromethyltrimethylsilane, methyl trifluoroacetate, methyl fluorosulfonyl difluoroacetate, (difluoromethyl)trimethylsilane, or bis(2-methoxyethyl)aminosulfonium trifluoride; the PDMS content in the coating is 60%–90%; and the ultraviolet light intensity is 500–1000 W / m². 2 The irradiation angle is 30° to 90°, and the irradiation time is 30 to 120 minutes.

[0050] Preferably, the biomimetic passive radiation cooling water collection foam material can be applied to fields such as domestic water collection, industrial metallurgy, aerospace, equipment cooling, scientific research, and farmland irrigation.

[0051] Comparative Example 1

[0052] A thermoplastic foam material, the specific preparation method of which is as follows:

[0053] S1. Polylactic acid is melt-blended with barium sulfate and sodium sulfate, and the melt is injected into a mold cavity under template-free conditions to obtain a square polymer sheet.

[0054] S2. Place the square polymer sheet in distilled water and sonicate it for 4 hours using an ultrasonic device to obtain a thermoplastic polymer material.

[0055] like Figure 1 These are scanning electron microscope images of the surfaces of polymer sheets and thermoplastic polymer materials. Figure 1It is known that the surface of the thermoplastic polymer material obtained by ultrasonic treatment of sodium sulfate particles in the polymer board has micropores with large pore size, which makes it easy for tiny water droplets to wet the foam material. The aggregation effect of tiny water droplets on the material surface is not good, and the water collection performance of the material is poor.

[0056] like Figure 2 This is a photograph showing the contact angle of a 10 μL water droplet on the surface of a thermoplastic foam material. (Source: [Insert Source Here]) Figure 2 It can be seen that thermoplastic polymer materials have relatively small contact angles, poor hydrophobicity, and poor water collection performance.

[0057] Example 1

[0058] A biomimetic passive radiation cooling water collection foam material ( Figure 3 The foam material has an interconnected microporous structure inside. Figure 4 The microporous structure has a diameter of 1–15 μm and its surface has an ellipsoidal array of structures and micro / nano structures. Figure 5 The ellipsoidal structure array is uniformly distributed with a density of 10 structures / mm², a height of 200 μm, and a diameter of 350 μm. The scale of the micro-nano structure is 0.1–1 μm, and the thermoplastic polymer is polylactic acid.

[0059] The specific preparation method of the biomimetic passive radiation cooling water collection foam material is as follows ( Figure 6 ):

[0060] S1: Polylactic acid 1, barium sulfate 2 (particle size 0.5-1 μm), and sodium sulfate 3 (2000-5000 mesh) are melt-blended and then injected into the mold cavity 5, which has a biomimetic micron-structured array template 4 fixed at the bottom. The melt 6 completely fills the biomimetic micron-structured array template 4. Figure 7 Afterwards, a polymer plate with a biomimetic micron structure array on the surface was obtained 7;

[0061] S2: Using clamps 8, the biomimetic micron structure array template 4 and polymer sheet 7 are clamped respectively. The constant temperature heating box is turned on to stabilize the peeling temperature at 30℃ and keep it at that temperature for 30 minutes. The traction speed is set to 20 mm / min. Under external traction (traction angle is 60°, traction force is 30 N), the biomimetic micron structure array template 4 is peeled off from the surface of the polymer sheet 7. The peeled polymer sheet 9 is placed in distilled water and ultrasonically treated with ultrasonic equipment 10 for 2 hours to obtain foam material 11.

[0062] S3: Titanium dioxide 14 and zirconium dioxide 15 were fluorinated using perfluorooctyltriethoxysilane 12 as the fluorinating agent and anhydrous ethanol 13 as the solvent. The fluorinated titanium dioxide 16 and zirconium dioxide 17 (particle size 2–5 μm) were then mixed with PDMS to prepare coating 18 (PDMS content 70%). The coating 18 was then uniformly sprayed onto the surface of foam material 11 with an ellipsoidal structure array using a spray gun 19, and the coating was applied using a light source with an intensity of 500 W / m². 2 Irradiation with ultraviolet light 20 for 1 hour (irradiation angle of 75°) enhances the wetting properties of titanium dioxide, resulting in a biomimetic passive radiation cooling water collection foam material 21 with a large number of hydrophilic sites on the surface.

[0063] It should be noted that:

[0064] The methods for determining the diameter of microporous structures, the density, diameter, and height of ellipsoidal structures, and the scale of micro / nano structures are as follows:

[0065] The cross-section and surface of the prepared passive radiative cooling water-collecting foam material were observed using a scanning electron microscope (SEM). The foam material was placed directly under the SEM lens for observation and original photographs were obtained. The density of the ellipsoidal structure was counted. The foam material was then cut using cryogenic cutting, with the cut surface placed perpendicular to the SEM lens. The microstructure of the cross-section was observed under the microscope, and original photographs were obtained. Using mapping software, the diameter of the micropores and the height and diameter of the ellipsoidal structure in different regions were measured, and the data were statistically analyzed to obtain the range of variation in the micropore diameter. A monolayer of dielectric particles and soluble particles was laid out and placed under the SEM lens for direct observation and original photographs. The particle size was measured.

[0066] Figure 8 The images show the contact angle of a 10 μL water droplet on the surface of a biomimetic passive radiative cooling water-collecting foam material, along with test results of the contact angle and roll-off angle of different water droplets on the material surface. The ellipsoidal and micro / nano structures on the surface of the product enhance the material's wetting resistance, providing more attachment sites for tiny water droplets. This causes the superhydrophobic surface of the material to exhibit point-like hydrophilic properties, resulting in an overall hydrophobic "petal effect." When water droplets land on the material surface, they form a solid-liquid-gas three-phase composite interface, reducing solid-liquid contact and preventing further wetting of the material, thus giving the foam material a larger contact angle.

[0067] Figure 9This describes the process of nucleation, aggregation, and rolling off of tiny water droplets on the surface of a biomimetic passive radiative cooling water-collecting foam material. When water vapor in the atmosphere comes into contact with the relatively cool foam material, the water vapor condenses at hydrophilic sites on the material surface to form tiny water droplets. These tiny droplets continuously aggregate on the material surface to form larger droplets, which then roll off the material surface into the collector under the influence of gravity, giving the material excellent water collection performance.

[0068] The reflectance and emissivity of the coating were characterized using infrared and ultraviolet-visible spectroscopy, and the results are as follows: Figure 10 As shown, Figure 10 These are the reflection and emission spectra of a biomimetic passive radiation-cooled water-collecting foam material. Figure 10 It can be seen that the average reflectivity of this foam material in the 0.3-2.5μm wavelength band of sunlight is as high as 90.5%, and the average emissivity in the 8-13μm wavelength band of infrared light is as high as 98.2%. Figure 11 The results show the surface temperature, dew point, relative humidity, and ambient temperature, as well as the water collection efficiency, when the biomimetic passive radiative cooling water-collecting foam material is applied to outdoor water collection. Throughout the entire water collection cycle, the surface temperature of the foam is lower than the ambient temperature, and for 5 hours the surface temperature is lower than the ambient dew point, which ensures that the material has a high water collection efficiency (29.5 g / m²h).

[0069] Example 2

[0070] The difference between the foam materials prepared in Example 2 and Example 1 is that the internal microporous structure of the product in Example 2 ( Figure 12 The diameter of the ellipsoidal structure array of the product is 1-10 μm. Figure 13 The micro / nano structures on the surface have a scale of 0.5–1 μm. The differences in the methods used to achieve them are:

[0071] The peeling temperature of S2 is 40℃, the traction speed is set at 40mm / min, the traction angle is 70°, the traction force is 20N, and the ultrasonic treatment time is 4h. The PDMS content in the coating of S3 is 85%, and the ultraviolet light intensity is 700W / m. 2 The irradiation angle was 45° and the irradiation time was 40 min. The remaining preparation steps were the same as in Example 1.

[0072] Example 3

[0073] The difference between the foam materials prepared in Example 3 and Example 1 is that the diameter of the internal micropore structure of the product in Example 2 is 5-30 μm, and the ellipsoidal structure array of the product ( Figure 14 The micro / nano structures on the surface have a scale of 0.5–2 μm. The differences in the methods used to achieve them are:

[0074] S2 has a set traction speed of 50 mm / min, a traction angle of 30°, and a traction force of 50 N. S3 has a PDMS content of 90% in its coating and an ultraviolet light intensity of 700 W / m. 2 The irradiation angle was 30° and the irradiation time was 1.5h. The remaining preparation steps were the same as in Example 1.

[0075] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A foam material, characterized in that, The foam material is primarily a thermoplastic polymer, in which dielectric particles are mixed; the interior of the foam material has a connected microporous structure, and the surface of the foam material has a micron-structure array; the surface of the micron-structure array has micro-nano structures formed by fluorinated and modified dielectric particles. The size of the microporous structure is 0.5~30 µm; The density of the microstructure array is 5~20 units / mm. 2 The height is 100~400 µm and the diameter is 100~500 µm; The dimensions of the micro / nano structures range from 0.1 to 20 µm.

2. The foam material as described in claim 1, characterized in that, The thermoplastic polymer is one or more of the following: polylactic acid, polyurethane, polystyrene, polyvinyl chloride, polyethylene, phenolic resin, ABS resin, polypropylene, polyvinylidene fluoride, polymethyl methacrylate, polycarbonate, polyethylene terephthalate, polytetrafluoroethylene, polyoxymethylene, polyamide, polyphenylene ether, polysulfone, polybutylene terephthalate, and polyphenylene sulfide. The dielectric particles are one or more of the following: barium sulfate, calcium carbonate, silicon dioxide, titanium dioxide, zirconium dioxide, boron nitride, silicon carbide, aluminum oxide, hafnium dioxide, zinc sulfide, barium sulfide, silicon nitride, silicate glass microspheres, and polymer / inorganic composite microspheres.

3. The method for constructing the foam material as described in any one of claims 1-2, characterized in that, Includes the following steps: (1) After the thermoplastic polymer is melt-blended with dielectric particles and soluble particles, it is injected into the mold cavity with a micron structure array template fixed at the bottom. After the melt completely fills the surface of the micron structure array template, a polymer plate with a micron structure array on the surface is obtained. (2) Peel the micron structure array template from the surface of the polymer sheet, place the peeled polymer sheet in water and stir or sonicate it to dissolve the soluble particles, and obtain a foam material with a micron structure array on the surface and a connected microporous structure inside. (3) The fluorinated modified dielectric particles are mixed with polydimethylsiloxane to prepare a coating, which is then uniformly sprayed onto the surface of the foam material obtained in step (2) which has a micron structure array on the surface and a connected microporous structure inside. The foam material is then irradiated with ultraviolet light to form a micro-nano structure on the surface of the micron structure array of the fluorinated modified dielectric particles, thus obtaining the foam material.

4. The construction method as described in claim 3, characterized in that, The dielectric particles are one or more of barium sulfate, calcium carbonate, silicon dioxide, titanium dioxide, zirconium dioxide, boron nitride, silicon carbide, aluminum oxide, hafnium dioxide, zinc sulfide, barium sulfide, silicon nitride, silicate glass microspheres, and polymer / inorganic composite microspheres; the soluble particles are one or more of sodium sulfate, potassium sulfate, sodium chloride, potassium chloride, sodium carbonate, potassium carbonate, magnesium chloride, sugar particles, polyethylene glycol, polyethylene oxide, polyacrylic acid, polyacrylamide, and polyvinyl alcohol; the melt blending method is two-roll blending, internal mixing, open milling, or extrusion.

5. The construction method as described in claim 4, characterized in that, The sugar granules are glucose or sucrose.

6. The construction method as described in claim 3, characterized in that, In step (2), the peeling method is as follows: the microstructure array template and the polymer plate are clamped by clamps respectively, and the microstructure array template is peeled off from the surface of the polymer plate under external force.

7. The construction method as described in claim 6, characterized in that, The peeling temperature is 30~100 ℃, the traction angle is less than or equal to 90°, the traction force is 5~50 N, and the traction speed is less than or equal to 50 mm / min; the ultrasonic treatment time is 2~5 h.

8. The construction method as described in claim 3, characterized in that, The fluorination-modifying reagent is at least one of perfluorooctyltriethoxysilane, trifluoromethyltrimethylsilane, methyl trifluoroacetate, methyl fluorosulfonyl difluoroacetate, (difluoromethyl)trimethylsilane, and bis(2-methoxyethyl)aminosulfonium trifluoride.

9. The construction method as described in claim 3, characterized in that, In step (3), the mass percentage of polydimethylsiloxane in the coating is 60% to 90%; The intensity of the ultraviolet light is 500~1000 W / m 2 The irradiation angle is 30°~90° and the irradiation time is 30~120 min.

10. The application of the foam material as described in any one of claims 1-2 in passive radiative cooling water collection.

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