A super-hydrophobic surface design using a spherical cap array structure

Abstract

The application discloses a kind of super-hydrophobic surface design method using cambered circular truncated cone array structure, and the microstructure for realizing super-hydrophobic function is the periodic arrangement micron cambered circular truncated cone array, and the application field is solar cell glass cover plate;The cambered circular truncated cone array structure designed can present super-hydrophobic function, meanwhile, the cambered structure of cambered circular truncated cone plays the role of reducing reflection and increasing transmission to incident sunlight, so that solar cell glass cover plate has high light transmittance under the premise of maintaining super-hydrophobic function;Based on the topographic structure characteristics of cambered circular truncated cone, combine Cassie-Baxter wetting model to deduce mathematical equation, to accurately represent the numerical relationship between the topographic structure characteristics of cambered circular truncated cone array and super-hydrophobic function, i.e.water droplet contact angle;According to numerical relationship, the design characteristics of cambered circular truncated cone array structure are brought in to solve water droplet contact angle, and the topographic structure characteristic parameters of cambered circular truncated cone array corresponding to contact angle greater than 150 ° are determined.The design method of the application can provide a design approach for super-hydrophobic surface structure of solar cell glass cover plate, and can realize automatic removal of dust deposited on the surface of solar cell glass cover plate and reducing reflection and increasing transmission to incident sunlight, so that solar cell can maintain high photoelectric conversion efficiency for a long time.

Description

Technical Field

[0001] The present invention relates to the field of designing super-hydrophobic structures on the surfaces of solar cell glass cover plates, and more particularly to a method for designing super-hydrophobic surfaces using a cambered truncated cone array structure. The designed cambered cone array structure exhibits super-hydrophobicity, while the cambered cones' curved surfaces reduce reflection and enhance transmittance of sunlight. The designed super-hydrophobic surface enables the solar cell glass cover plate to have high light transmittance while maintaining its super-hydrophobicity, automatically removes dust deposited on the solar cell glass cover plate, and reduces reflection and enhances transmittance of incident sunlight, thereby enabling the solar cell to maintain high photoelectric conversion efficiency over a long period of time. Background Art

[0002] my country's photovoltaic industry is experiencing rapid growth. Dust accumulation in service environments significantly reduces light transmittance on glass cover panels, impacting photovoltaic conversion efficiency. Traditional cleaning methods for these deposited dusts are labor-intensive, energy-intensive, and prone to damage. Therefore, efforts are underway to impart a superhydrophobic property to glass cover panels, enabling automated removal of deposited dust and maintaining high photovoltaic conversion efficiency for solar cells. However, current challenges include complex superhydrophobic microstructure preparation and low light transmittance.

[0003] A super-hydrophobic surface refers to a material surface with a water droplet contact angle greater than 150° and a rolling angle less than 10°. It has important application value in the fields of self-cleaning, corrosion prevention, and frost suppression. The contact angle of a droplet on a solid surface is an important indicator for measuring wetting properties. The contact angle is the result of the surface tension balance between the three interfaces of solid, liquid, and gas. When the tension is balanced, the total energy of the system tends to be the lowest, and the droplet on the solid surface is in a stable state. Wenzel believed that when a droplet contacts a solid surface, it can completely immerse the microstructure of the rough surface, and proposed the Wenzel equation cos i w =rcos i in i w is the droplet contact angle, r is the roughness factor, i is the intrinsic contact angle of a droplet on a smooth surface. However, the droplet cannot completely wet the microstructure of a rough surface, so the Cassie-Baxter wetting model was proposed, which believes that the contact surface is composed of three parts: the droplet, the microstructure of the solid surface, and the air trapped inside the microstructure. Based on this, the Cassie-Baxter equation cos i T = f sl ( f r cos i c +1)-1, where i T is the contact angle, i c is the intrinsic contact angle, f s1 is the ratio of the actual wetted solid area of ​​the droplet to the apparent geometric contact area. f r The roughness coefficient represents the degree of surface roughness. The superhydrophobic nature of a material surface is primarily due to the microtopography forming a large air-liquid interface that maintains the Cassie-Baxter wetting state, resulting in a large contact angle on the surface. Microtopography is a key factor influencing the high contact angle exhibited by water droplets on a material surface. Therefore, superhydrophobic surface preparation primarily involves modifying low-surface-energy materials onto rough surfaces with microtopography, or constructing microtopography on the surface of low-surface-energy materials.

[0004] In the field of super-hydrophobic structure design for solar cell glass cover panels, high light transmittance of the glass cover panel is crucial. When light hits the surface of the glass cover panel, a certain proportion of the light will be reflected, and a certain proportion of the light can enter the interior of the object and be absorbed by the object, while the remaining light can penetrate the object and continue to propagate, generating light transmittance. The sum of reflectivity, transmittance, and absorptivity is 1, and a decrease in reflectivity means an increase in transmittance. The designed arc-surface truncated cone array structure, while meeting the super-hydrophobic function, has a curved surface structure of the arc-surface truncated cone that can reduce the incident angle and reflect sunlight multiple times, thereby playing a role in reducing reflection and increasing transmittance of sunlight.

[0005] Based on the principle of superhydrophobic surface design, the inventor of this patent application has carried out research on superhydrophobic surface design with the support of projects such as the Hebei Provincial Natural Science Foundation General Project (Research on the Superhydrophobic Mechanism of the Slip Zone of Pitcher Plant and the Bionic Preparation Technology of Micro-Nano Composite Structures, E2019208306) and the Central Guidance of Local Science and Technology Development Fund Project (Research on Femtosecond Laser Preparation Technology of Superhydrophobic Micro-Nano Composite Structures on Titanium Alloy Surfaces, 226Z1804G). Using the micro-morphological structure of the slip zone of pitcher plant that can exhibit superhydrophobic properties as a bionic prototype, a superhydrophobic surface was designed and prepared using 3D printing technology and high-voltage electrostatic adsorption technology. The test results showed that the water drop contact angle of the prepared superhydrophobic surface was 152.6°, indicating that it has good superhydrophobic function (authorized invention patent, patent number ZL 202010458218.7; academic paper, Bioinspired, Biomimetic and Nanobiomaterials, 2022, 11(1): 1-7). Therefore, the patent applicant has the basic conditions for super-hydrophobic surface design.

[0006] Invention Patent 202011525996.X discloses a method for designing and preparing a super-hydrophobic surface. The surface is etched away through a cutting process to create a microscopic surface topography of pits and bumps. The microscopic surface topography and surface texture combine to form a multi-level micro-nanostructure, resulting in a super-hydrophobic surface with excellent mechanical wear resistance. This structure boasts high production efficiency, low cost, cleanliness, and strong adaptability. However, its micro-topography cannot be applied to solar cell glass cover surfaces due to limitations in the construction materials. Invention Patent 202011352578.5 discloses a method for designing a biomimetic gradient super-hydrophobic structure based on the Marangoni effect. Based on typical biological surface hydrophobic structures, this method introduces both structural and temperature gradients on a solid surface by constructing a composite array structure and installing nano-heating plates. The Marangoni effect, generated by the coupling of these structural and temperature gradients, causes droplets to move in a directional manner and roll off automatically, imparting super-hydrophobic properties to the solid surface. However, due to limitations in the construction materials, this micro-topography cannot be applied to solar cell glass cover surfaces.

[0007] In summary, in the field of super-hydrophobic structure design on the surface of solar cell glass cover, although the existing super-hydrophobic surface can present good super-hydrophobic characteristics through the designed micro-morphology structure, it is not suitable for the field of solar cell glass cover surface. Therefore, the present invention proposes a super-hydrophobic surface design method using a cambered cone array structure, the designed cambered cone array structure can present super-hydrophobic function, and the cambered surface structure of the cambered cone can play a role of reducing reflection and increasing transmittance to incident sunlight; Based on the structural characteristics of the cambered cone array, a mathematical equation is derived in combination with the Cassie-Baxter wetting model, which is used to calculate the characteristic parameters of the cambered cone array structure to ensure that the designed surface has super-hydrophobic function. The present invention provides a super-hydrophobic surface design method using a cambered cone array structure, which can realize the automatic removal of dust deposited on the surface of solar glass cover and the reduction of reflection and increase of transmittance to incident sunlight, so that solar cells can maintain high photoelectric conversion efficiency for a long time. Summary of the Invention

[0008] The present invention provides a super-hydrophobic surface design method using a cambered truncated cone array structure, wherein the microstructure for achieving the super-hydrophobic function is a periodically arranged micron-scale cambered truncated cone array. Based on the structural characteristics of the cambered truncated cone array and combined with the Cassie-Baxter wetting model, a mathematical equation is derived to accurately calculate the three-dimensional structural parameters of the cambered truncated cone, so that the designed solar cell glass cover has high transmittance while maintaining the super-hydrophobic function. The present invention directly designs a microstructure on the surface to give it a super-hydrophobic function. In order to achieve the above functions, the technical solution adopted by the present invention is:

[0009] A method for designing a super-hydrophobic surface using a cambered frustum array structure, characterized by comprising the following steps:

[0010] Step 1: Design the microstructure of the super-hydrophobic surface, i.e., a periodically arranged cambered cone array structure; the radius of the top small circle of the cambered cone is r The radius of the arc surface is R ;

[0011] Step 2: Based on the Cassie-Baxter wetting model, a mathematical equation is derived to establish a numerical relationship between the structural characteristics of the cambered frustum array and the superhydrophobic function, i.e., the contact angle of a water droplet;

[0012] Step 3: Calculate the structural characteristic parameters of the cambered frustum array corresponding to a water drop contact angle greater than 150° based on the established numerical relationship.

[0013] Based on the above technical solution, the super-hydrophobic surface design method using a cambered cone array structure is described. The microstructure that realizes the super-hydrophobic function is a periodically arranged micron-scale cambered cone array. The designed cambered cone array structure can exhibit super-hydrophobic function. At the same time, the cambered cone structure plays the role of reducing reflection and increasing transmittance of incident sunlight. In terms of characteristic parameters, the radius of the small circle at the top of the cambered cone is r Designed to be 10~15 μm, the radius of the arc surface structure of the arc cone R Designed to be 45-55 μm. When water droplets infiltrate the curved cone array structure, the gaps between adjacent curved cones trap air, forming a liquid-air-solid interface and thereby exhibiting superhydrophobicity. When incident sunlight strikes the curved surface structure of the curved cone, the curved structure reduces the incident angle and reflects the sunlight multiple times, thereby reducing reflection and increasing transmittance.

[0014] On the basis of the above technical solution, the numerical relationship of the super-hydrophobic surface design method using a cambered truncated cone array structure is:

[0015] Where: i T and i c Represent the theoretical contact angle and the intrinsic contact angle, respectively. The intrinsic contact angle of a water drop on a smooth surface i c 100°~110°; r、R are respectively the radius of the small circle on the top of the cambered cone and the radius of the cambered surface; l is the wetting coefficient, that is, the degree of wetting of the cambered cone by the water drop. When the water drop floats on the top of the cambered cone, l =0, when the water droplet completely soaks the cambered cone, λ=1, so 0≤λ≤1.

[0016] On the basis of the above technical solution, the structural characteristic parameters of the arc-surface frustum array are brought into the numerical relationship to control l The theoretical value of the water droplet contact angle is calculated, and whether the designed super-hydrophobic surface has super-hydrophobic function is judged based on whether the theoretical value of the contact angle is greater than 150°.

[0017] The beneficial effects of the above technical solution are: a super-hydrophobic surface design method using a cambered truncated cone array structure of the present invention, wherein the microstructure for realizing the super-hydrophobic function is a periodically arranged cambered truncated cone array; based on the structural characteristics of the cambered truncated cone array, a mathematical equation is derived in combination with the Cassie-Baxter wetting model to establish a numerical relationship between the structural characteristics of the cambered truncated cone array and the super-hydrophobic function, i.e., the contact angle of a water droplet; by regulating the characteristic parameters, a controllable design of the super-hydrophobic function can be realized, and high light transmittance can be achieved while ensuring the super-hydrophobic function (contact angle > 150°). BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of the overall structure of the present invention;

[0019] Figure 2 Schematic diagram of the cambered frustum of the present invention;

[0020] Figure 3 A schematic cross-sectional view of the arc-surface frustum structure of the present invention;

[0021] Figure 4 Schematic diagram of light reflection of the present invention;

[0022] Figure 5 Design flow chart of the present invention.

[0023] In the figure: 1. Cambered frustum; 1-1. Small circle on the top of the cambered frustum; 1-2. Cambered surface structure of the cambered frustum; 2. Bottom surface; 3. Base. DETAILED DESCRIPTION

[0024] The following examples are used to illustrate the present invention, but are by no means intended to limit the scope of the present invention. The working process of the present invention will be described in detail below with reference to the accompanying drawings.

[0025] The present invention discloses a method for designing a super-hydrophobic surface using a cambered truncated cone array structure. The design process comprises the following steps: designing a super-hydrophobic surface microstructure into a periodically arranged cambered truncated cone array structure; deriving a mathematical equation based on the Cassie-Baxter wetting model to establish a numerical relationship between the structural characteristics of the cambered truncated cone array and the super-hydrophobic function, namely, the water droplet contact angle; and calculating, based on the numerical relationship, the structural characteristic parameters of the cambered truncated cone array corresponding to a water droplet contact angle greater than 150°.

[0026] like Figure 1 、 Figure 2As shown, the present invention adopts a super hydrophobic surface design method using a cambered cone array structure, which is characterized in that the cambered cone 1 and the base 3 are an integrated structure, and the super hydrophobic surface microstructure is a cambered cone array structure. The radius of the top small circle 1-1 of the cambered cone is r =10~15 μm, in this embodiment r =10 μm; the radius of the arc surface structure 1-2 of the arc surface frustum R =45~55 μm, in this embodiment R = 50 μm. Based on the Cassie-Baxter wetting model, a mathematical equation was derived to establish the numerical relationship between the characteristic parameters of the cambered frustum array structure and the superhydrophobicity, namely the contact angle of a water droplet. The Cassie-Baxter wetting model posits that when a liquid droplet infiltrates a solid surface, it traps air within the solid surface microstructure. Therefore, the contact surface is composed of three components: the liquid droplet, the air, and the solid surface microstructure. Based on this, the Cassie-Baxter equation was proposed:

[0027] (1)

[0028] Where, i T is the contact angle, i c is the intrinsic contact angle, f s1 is the ratio of the actual wetted solid area of ​​the droplet to the apparent geometric contact area. f r Indicates the roughness coefficient, that is, the non-smoothness of the surface. Figure 1 、 Figure 2 As shown, the designed super-hydrophobic surface is a periodically arranged arc-shaped truncated cone array structure, and the projected area of ​​the unit microstructure is S P It can be calculated by formula (2):

[0029] (2)

[0030] The actual surface area generated by the unit microstructure S S It consists of three parts: the top small circle 1-1 of the arc-shaped cone, the arc-shaped cone structure 1-2, and the bottom surface 2. It is calculated by the following formula:

[0031] (3)

[0032] Where, r Indicates the radius of the small circle 1-1 at the top of the cambered cone; R Indicates the radius of the arc structure 1-2 of the arc-surface frustum; DIt represents the distance between adjacent arc-shaped cones 1, that is, the sum of the diameter of the top small circle 1-1 of the arc-shaped cone and the diameter of the arc-shaped structure 1-2 of the arc-shaped cone, that is, D =2( r+R ).

[0033] According to this roughness coefficient f r It can be expressed as,

[0034] (4)

[0035] When water droplets infiltrate the designed arc-surface truncated cone array structure, they will infiltrate the arc-surface truncated cone 1 to varying degrees, so the wetting coefficient is introduced. l , represents the degree of wetting of the cambered cone 1 by the water droplet; when the water droplet only wets the top of the cambered cone 1, λ=0, and when the water droplet completely wets the cambered cone 1, λ=1, so 0≤λ≤1; if the designed super-hydrophobic surface has a better super-hydrophobic function, the water droplet contact angle must be greater than 150°, which means that the water droplet has a smaller degree of wetting on the cambered cone 1, that is, l Should be a smaller value.

[0036] At this time, the water droplet wets the top small circle 1-1 of the arc-surface frustum and the arc-surface structure 1-2 of the partial arc-surface frustum, so the ratio of the area of ​​the arc-surface frustum 1 actually wetted by the water droplet to the apparent geometric contact area is f s1 It can be obtained by formula (5):

[0037] (5)

[0038] Where: f s1 It represents the ratio of the actual solid area wetted by the droplet to the apparent geometric contact area; l represents the wetting coefficient; r Indicates the radius of the small circle 1-1 at the top of the cambered cone; R Indicates the radius of the arc structure 1-2 of the arc-surface frustum; D It represents the distance between adjacent arc-shaped cones 1, that is, the sum of the diameter of the top small circle 1-1 of the arc-shaped cone and the diameter of the arc-shaped structure 1-2 of the arc-shaped cone, that is, D =2( r + R ).

[0039] Substituting formula (4) and formula (5) into formula (1), we can obtain the numerical relationship between the structural characteristics of the designed cambered cone array and the superhydrophobic function, i.e., the water droplet contact angle, as shown below:

[0040] (6)

[0041] Where: i T and i c The contact angle of a water droplet on a smooth surface is generally 100° to 110°. i c =105°.

[0042] In the designed super-hydrophobic surface, the microstructure is composed of a periodically arranged cambered cone array. In this embodiment, its characteristic parameters are set as follows: the radius of the top small circle 1-1 of the cambered cone r= 10 μm, radius of the arc structure 1-2 of the arc cone R =50 μm. The wettability coefficient of the water droplet on the cambered cone 1 is l =0.4. Substitute the above parameters into formula (6) to calculate the contact angle of the designed superhydrophobic surface i T =152.5°, indicating good superhydrophobicity.

[0043] The present invention adopts a method for designing a super-hydrophobic surface using a cambered truncated cone array structure. According to formula (6), when determining i c 、 l Under the premise of equal coefficients, by adjusting the radius of the small circle 1-1 on the top of the arc cone r , the radius of the arc structure 1-2 of the arc cone R , the controllable design of superhydrophobic function can be achieved.

[0044] like Figure 3 、 Figure 4 As shown, a super-hydrophobic surface design using a curved cone array structure. When incident sunlight illuminates the curved surface structure 1-2 of the curved cone, the curved surface structure 1-2 of the curved cone can reduce the incident angle and reflect the sunlight multiple times, thereby reducing reflection and increasing transmittance of the sunlight.

[0045] like Figure 5As shown, a design process of a super-hydrophobic surface design method using a cambered cone array structure, first designing a super-hydrophobic surface microstructure model, i.e. designing a cambered cone array structure; combining the Cassie-Baxter infiltration model to derive a mathematical equation, establishing a numerical relationship between the cambered cone array structural feature and the super-hydrophobic function, i.e. the water drop contact angle; presetting structural characteristic parameters according to the mathematical equation, calculating the contact angle and determining whether it is greater than 150 °; optimizing the design of the super-hydrophobic surface by regulating and controlling the structural characteristic parameters, until the contact angle is greater than 150 °, realizing the controllable design of the super-hydrophobic surface. A super-hydrophobic surface design method using a cambered cone array structure provided by the present invention, can provide a design approach for the super-hydrophobic surface of a solar cell glass cover plate, can realize the automatic removal of dust deposited on the surface of the solar glass cover plate and the anti-reflection and anti-transmittance of incident sunlight, so that the solar cell maintains a high photoelectric conversion efficiency for a long time.

[0046] Finally, it should be noted that the above embodiments are intended only to illustrate the technical solutions of the present invention and are in no way intended to limit the scope of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention are intended to be encompassed by the claims of the present invention.

Claims

1. A method for designing a super-hydrophobic surface using a cambered frustum array structure, characterized in that The design steps include: Step 1: Designing a super-hydrophobic surface microstructure, wherein the microstructure is composed of a periodically arranged micron-scale truncated cone array; Step 2: Based on the Cassie-Baxter wetting model, a mathematical equation is derived to establish the numerical relationship between the structural characteristics of the cambered cone array and the superhydrophobic function, i.e., the contact angle of the water droplet. ， Where: θ T and θ c Represent the theoretical contact angle and the intrinsic contact angle, respectively. The intrinsic contact angle of a water drop on a smooth surface θ c 100°~110°; r、R are respectively the radius of the small circle on the top of the cambered cone and the radius of the cambered cone's arc surface structure; λ is the wetting coefficient, that is, the degree of wetting of the cambered cone by the water drop. When the water drop floats on the top of the cambered cone, λ =0, when the water droplet completely soaks the cambered cone λ =1; Step 3: Calculate the structural characteristic parameters of the cambered frustum array corresponding to a water drop contact angle greater than 150° based on the established numerical relationship.

2. The method for designing a super-hydrophobic surface using a cambered frustum array structure according to claim 1, wherein The arc-surface frustum and the base are an integrated structure. The arc-surface frustum is arranged periodically. The curvature of the arc-surface frustum is a quarter of a circle. The arc-surface frustum array structure can achieve super-hydrophobic function. At the same time, the arc structure of the arc-surface frustum can reduce reflection and increase transmittance of incident sunlight.

3. The method for designing a super-hydrophobic surface using a cambered frustum array structure according to claim 1, wherein The radius r of the small circle on the top is designed to be 10~15 μm, and the radius R of the arc surface structure of the arc-surface frustum is designed to be 45~55 μm. The arc-surface frustum has structural characteristic parameters at the micron level. The arc-surface frustum array structure formed can retain air, and when water droplets infiltrate, a liquid-gas-solid contact interface can be formed, thereby presenting a superhydrophobic function; when incident sunlight illuminates the arc surface structure of the arc-surface frustum, the arc surface structure can reduce the incident angle and reflect the sunlight multiple times, thereby playing a role in reducing reflection and increasing transmittance of the sunlight.

4. The method for designing a super-hydrophobic surface using a cambered frustum array structure according to claim 1, wherein The design features of the arc-surface truncated cone array structure are brought into the numerical relationship to calculate the theoretical value of the water droplet contact angle. The super-hydrophobic function is judged based on whether the contact angle is greater than 150°, thereby realizing the controllable design of the super-hydrophobic surface. The arc-surface structure of the arc-surface truncated cone can also play a role in reducing reflection and increasing transmittance of incident sunlight. Therefore, the designed super-hydrophobic surface can make the solar cell glass cover have high transmittance while maintaining the super-hydrophobic function.

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