Self-cleaning UV-resistant transparent superhydrophobic film, its preparation method and applications

Abstract

This invention belongs to the field of new materials and provides a UV-resistant transparent superhydrophobic film (TSURF) with excellent self-cleaning properties. This film can be mass-produced through lamination and plasma gas etching. In the preparation process, a UV-resistant polyethylene terephthalate (PET) layer is first used as an intermediate layer, with a pressure-sensitive adhesive (PSA) laminated at the bottom to provide excellent adhesion to various substrates. Then, a PMMA acetone dispersion solution of fumed hydrophobic silica (SiO2) is drop-coated onto the other side of the PET. After the solvent evaporates, the surface is finally etched and fluorinated with CHF3. TSURF exhibits selective transmittance of incident light, maintaining high transmittance in the visible light region (400-800nm) while reflecting almost all ultraviolet light (10-380nm). Furthermore, TSURF can withstand various external deformations and acid / alkali chemical environments, maintaining excellent superhydrophobic properties under different temperature conditions. It possesses excellent dustproof, self-cleaning, and weather-resistant properties, making it widely applicable in architectural glass, photovoltaic energy, and other fields.

Description

Technical Field

[0001] This invention belongs to the field of new materials and relates to an anti-ultraviolet transparent superhydrophobic film, especially an anti-ultraviolet transparent superhydrophobic film with excellent self-cleaning properties. Background Technology

[0002] The glass curtain walls of high-rise buildings worldwide have reached approximately 3 billion square meters, leading to higher cleaning costs and increased indoor ultraviolet (UV) radiation intake. Therefore, self-cleaning and light-management surface materials are crucial for addressing this trend. Ultraviolet radiation is essential for life on Earth; however, excessive UV radiation can damage organic bonds and is harmful to polymer products and even humans. Therefore, UV-resistant materials are needed to block the ultraviolet components of sunlight. For architectural glass, adequate transparency is required to provide optimal indoor lighting. Currently available materials for this problem typically exhibit selective light transmission properties, often displaying strong reflection of UV wavelengths and high transmittance of visible light. Currently, the most commercially successful is light blue low-emissivity (low-E) glass produced by vacuum magnetron sputtering; however, in practical use, low-E glass has been found to require additional manpower for regular cleaning due to its lack of self-cleaning and dust resistance. Therefore, for outdoor light-management materials, addressing surface contaminant adhesion is a critical issue.

[0003] Meanwhile, as green energy gradually becomes the mainstream direction of energy supply development, silicon-based photovoltaic (PV) devices have received widespread attention in recent years due to their high photovoltaic conversion efficiency. Currently, most photoelectric conversion elements are adapted to light wavelengths between 380nm and 1100nm, which means that ultraviolet radiation needs to be shielded to protect the external panels and internal integrated components from aging or damage. Another critical issue is that contaminant deposition increases the reflection and absorption of incident photons, negatively impacting the energy output of photovoltaic devices. However, the main solutions currently are manual or machine cleaning, which increases the labor and maintenance costs of photovoltaic power generation modules. Therefore, superhydrophobic materials with self-cleaning properties are considered a more advantageous passive cleaning strategy to improve energy conversion efficiency and reduce resource waste. Integrating ultra-wear-resistant surfaces with anti-fouling and self-cleaning properties into materials is a promising strategy that can expand the applicability and durability of optical materials in different fields.

[0004] Based on the surface wetting state, self-cleaning materials can be divided into superhydrophilic, superhydrophobic, and smooth materials. Superhydrophilic surfaces are considered to exhibit extremely low water contact angles, and their self-cleaning principle is similar to that of slippery liquid-injected porous surfaces (SLIPS), removing impurities from the surface through the high fluidity of the fluid surface [Tak-Sing Wong et al., Bioinspired self-repairing slippery surfaces with pressure-stable omniphobicity, Nature volume 477, pages 443–447 (2011); Zheming Tong et al., Hagffsh-inspired Smart SLIPS Marine Antifouling Coating Based on Supramolecular: Lubrication Modes Responsibly Switching and Self-healing Properties, Adv. Funct. Mater. 2022, 32, 2201290; Fang Wang, Light-induced charged slippery surfaces, Sci. Adv. 8, eabp9369 (2022) 8 July 2022]. However, such surfaces, which depend on the presence of a liquid film, are generally considered to be non-durable. Therefore, superhydrophobic surfaces inspired by the lotus effect are a preferred choice for solving the self-cleaning problem. However, the superhydrophobic light management materials reported to date are often opaque [wulong Li et al., In Situ Growth of a Stable Metal-Organic Framework (MOF) on Flexible Fabric via a Layer-by-Layer Strategy for Versatile Applications, ACS Nano 2022, 16, 14779-14791; Jianing Song, Durable radiative cooling against environmental aging, Nature Communications, (2022) 13: 4805]. Furthermore, due to the application scenarios, the surface needs to be able to withstand even minor dust accumulation, rain, and sunlight degradation. More demanding is the need to resist the wet abrasion effects of low surface energy fluids and even detergents (surfactant complexes), which have never been explored before. Therefore, achieving superhydrophobicity, wet abrasion durability, and transparency simultaneously in optical materials remains a challenge. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing an anti-UV transparent superhydrophobic membrane with excellent self-cleaning properties.

[0006] The technical solution of the present invention is as follows:

[0007] A method for preparing a self-cleaning, UV-resistant transparent superhydrophobic film (TSURF) includes the following steps:

[0008] S1, pressing silicone pressure-sensitive adhesive (PSA) onto the back side of a UV-resistant film; preferably, pressing the silicone pressure-sensitive adhesive (PSA) using a laminator; the UV-resistant film is commercially available;

[0009] S2, an acetone solution of PMMA mixed with hydrophobic vapor-phase nano-SiO2 is drop-coated onto the surface of a pressed PET film.

[0010] S3, after acetone evaporates, a solid PMMA coating doped with silicon dioxide is formed on the PET film.

[0011] S4, hydrophobic treatment of TSURF surface

[0012] Plasma gas etching using CHF3 as the working gas is employed. During the etching process, some PMMA is etched away, while the dispersed silicon dioxide is retained and forms the ends of the synaptic structures, creating a hierarchical three-dimensional rough structure on the TSURF surface.

[0013] The terms "back side" and "surface side" used in this invention only indicate the relative positions of the membrane, that is, one side of the membrane is the "back side" and the other side of the membrane is the "surface side".

[0014] A preferred method for preparing an acetone solution of PMMA mixed with hydrophobic vapor-phase nano-SiO2 involves first dissolving PMMA in acetone solvent, then adding nanoscale hydrophobic vapor-phase SiO2 and ultrasonically dispersing until completely dispersed. The solution is then deposited onto the surface of a PET film via drop-coating. After complete evaporation of the acetone, a uniform PMMA layer doped with nano-SiO2 is formed. More preferably, the mass fraction of PMMA is 10–20 wt%. A more preferred method is to use a PMMA mass fraction of 15 wt%.

[0015] Preferably, the hydrophobic vapor-phase nano-SiO2 has a particle size of 5–40 nm. More preferably, the hydrophobic vapor-phase nano-SiO2 has a particle size of 5–10 nm.

[0016] More preferably, the PMMA layer has a particle concentration of (0.4~2)×10⁻⁶ per unit volume. -3 g·mL -1The volume of solution dropped per unit area is 0.05–0.30 mL / cm². -2 .

[0017] The plasma etching process is performed in an inductively coupled plasma (ICP) etching system. CHF3 is used as the working gas to etch and fluorinate the film to obtain a transparent superhydrophobic film. The fluorination etching temperature is -5 to 5°C, and the processing time is 15 to 25 seconds. During etching, the gas pressure is set to 0.7 to 0.9 Pa, and the flow rate is 0.05 to 0.07 L / min. The upper electrode ICP power is set to 180 to 220 W, and the lower electrode RF power is set to 8 to 12 W. More preferably, the fluorination etching temperature is 0°C, and the processing time is 20 seconds. During etching, the gas pressure is set to 0.8 Pa, and the flow rate is 0.06 L / min. The upper electrode ICP power is set to 200 W, and the lower electrode RF power is set to 10 W.

[0018] The present invention also provides a self-cleaning, UV-resistant transparent superhydrophobic film (TSURF) obtained by the above method. The TSURF has an average transmittance of over 85% in the visible light region; the total thickness of the film is approximately 80 μm.

[0019] Preferably, a PMMA coating of SiO2 with a particle size of 7-10 nm can combine transmittance and roughness.

[0020] In the preparation of the PMMA layer, the particle concentration per unit volume is (0.4~2)×10⁻⁶. -3 g·mL -1 The volume of solution dropped per unit area is 0.05–0.30 mL / cm². -2 At this point, an average light transmittance of over 85% can be obtained. The particle concentration per unit volume is (0.4–1) × 10⁻⁶. -3 g·mL -1 The volume of solution dropped per unit area is 0.05–0.25 mL / cm². -2 At this point, an average light transmittance of 90% or higher can be obtained. More preferably, the PMMA layer has a particle concentration of 1×10⁻⁶ per unit volume. - 3 g·mL -1 The volume of solution dropped per unit area is 0.2 mL·cm³. -2 .

[0021] Preferably, the mass fraction of PMMA is 0–30 wt%. Balancing excellent superhydrophobicity and high transparency, the mass fraction of PMMA is 10–20 wt%, and most preferably, it is 15 wt%.

[0022] In tests using anhydrous ethanol as the wet grinding medium, after 12,800 friction cycles, the water contact angle on the TSURF surface decreased from the initial 154.68°±2.21° to 148.29°±4.47°, while the roll-off angle increased from the initial 2.13°±0.36° to 14.21°±2.43° (e.g., ...). Figure 8 (As shown in .b). The water droplet contact angle hysteresis (CAH) on the TSURF surface was only 3.81° ± 1.42° after 12,800 friction cycles. This indicates that the surface structure and chemical composition of the TSURF surface were hardly damaged during the wet abrasion test, and the lateral adhesion of water to its surface was very low.

[0023] TSURF exhibits adhesion of up to 20.73 ± 1.71 MPa to glass with a surface rich in polar hydroxyl groups. Even on polished wood and waxed leather surfaces, adhesion reaches 14.39 ± 1.21 MPa and 11.27 ± 2.46 MPa, respectively.

[0024] At the time of maximum light intensity, the ultraviolet radiation intensity reached 1540 μW·cm. -2 The intensity of ultraviolet light passing through Low-E glass is 854 μW·cm. -2 The ultraviolet intensity passing through TSURF-glass is only 9.6 μW·cm. -2 During testing, TSURF glass achieved an average UV blocking rate of 99.5%, while Low-E glass only achieved an average UV blocking rate of 45.8%.

[0025] The present invention also provides applications of the TSURF, specifically in photovoltaic (PV) materials.

[0026] We designed a highly transparent superhydrophobic UV-resistant film (TSURF) that can be mass-produced through lamination and plasma gas etching. In the fabrication process, a UV-resistant polyethylene terephthalate (PET) layer is first used as an intermediate layer, with a pressure-sensitive adhesive (PSA) layer laminated to the bottom to provide excellent adhesion to various substrates. Then, a PMMA-acetone dispersion of fumed hydrophobic silica (SiO2) is drop-coated onto the other side of the PET. After the solvent evaporates, the surface is finally etched with CHF3 and fluorinated. TSURF exhibits selective transmittance of incident light, maintaining high transmittance in the visible light region (400-800 nm) while reflecting almost all ultraviolet light (10-380 nm). Furthermore, TSURF can withstand various external deformations and acid / alkali chemical environments, maintaining excellent superhydrophobic properties at different temperatures. Notably, TSURF retains its superhydrophobicity even after more than 10,000 wet milling cycles using ethanol and surfactants. At the same time, it has excellent dustproof, self-cleaning and weather resistance, which makes it widely used in architectural glass, photovoltaic energy and other fields. Attached Figure Description

[0027] Figure 1 A schematic diagram of the preparation process of TSURF, a superhydrophobic and UV-resistant film with high transparency.

[0028] Figure 2 shows the macroscopic and microscopic characterization of TSURF. (a) A photograph of TSURF pasted on glass. (b) SEM images of the surface and interface of TSURF.

[0029] Figure 3 The effect of dispersing nano-SiO2 of different particle sizes in an acetone solution of PMMA on the transmittance of the formed PMMA coating in the visible light region.

[0030] Figure 4 Effects of the concentration of nano-SiO2 dispersed in acetone solutions of different PMMA and the coating volume per unit area on the transmittance in the visible light region. (a) Curve of average transmittance of TSURF in the visible light region as a function of nanoparticle concentration per unit volume; (b) Curve of average transmittance of TSURF in the visible light region as a function of coating solution volume per unit area.

[0031] Figure 5 The effects of PMMA mass fraction on visible light transmittance and hydrophobic properties of the material are shown in the diagrams: (a) Schematic diagram of the effect of roughness distribution density after etching on the hydrophobicity of the material surface and incident light scattering / refraction; (b) Curve of visible light average transmittance of TSURF as a function of PMMA mass fraction; (c) Curve of water contact angle of TSURF surface as a function of PMMA mass fraction.

[0032] Figure 6 The effects of etching time on material transparency and hydrophobicity: (a) the effect of different plasma gas etching times on the hydrophobicity and visible light transmittance of the thin film; (b) photographs of the material transparency and water wetting state on the material surface after different etching times.

[0033] Figure 7 SEM images and magnified views of the TSURF surface.

[0034] Figure 8 TSURF Ethanol Wet Friction Test; (a) 3D schematic diagram of the wet friction test equipment, (b) Curves showing the changes in water contact angle and roll-off angle with friction cycles during the friction test with ethanol as the wet friction medium, (c) Curve showing the changes in water contact angle hysteresis with friction cycles during the friction test with ethanol as the wet friction medium.

[0035] Figure 9 Comparison of the adhesion of TSURF to different substrate materials.

[0036] Figure 10 Testing of ultraviolet blocking performance.

[0037] Figure 11 A photograph of the actual weather resistance testing equipment.

[0038] Figure 12 Comparison photos of different samples before and after weathering resistance testing; (a) Comparison photos of original glass before and after weathering resistance testing; (b) Comparison photos of TSURF-glass before and after weathering resistance testing; (c) Comparison photos of original stainless steel before and after weathering resistance testing; (d) Comparison photos of TSURF-stainless steel before and after weathering resistance testing.

[0039] Figure 13 Comparison of hydrophobic properties of Low-E glass and TSURF glass before and after weathering resistance testing.

[0040] Figure 14 Photographs of different samples before and after the dust resistance test and after water rinsing; (a) Photographs of the original glass before and after the dust resistance test and after water rinsing; (b) Photographs of the TSURF-coated glass before and after the dust resistance test and after water rinsing; (c) Photographs of the original stainless steel and the TSURF-coated stainless steel before and after the dust resistance test and after water rinsing.

[0041] Figure 15 Photos of the original PV panel and the panel with TSURF attached; (a) photos of the PV panel with TSURF attached before and after outdoor testing, and (b) photos of the original PV panel before and after outdoor testing.

[0042] Figure 16 TSURF performance in PV panels. Detailed Implementation

[0043] Experimental materials and instruments

[0044] Fumed hydrophobic silica, SiO2, analytical grade, Aladdin Group; polymethacrylate, (C5O2H8) n Analytical grade, Aladdin Group; silicone pressure-sensitive adhesive, commercial adhesive, Shenzhen KANGLIBANG; polyethylene terephthalate film, (C 10 H8O4) n Finished film, Dongguan Nanyu Technology Co., Ltd.; Acetone, CHO, analytical grade, Thermo Fisher Scientific; Hydrochloric acid, HCl, analytical grade, Aladdin Group. PET film, UV-blocked polyethylene terephthalate film, purchased from Dongguan Nanyu Technology Co., Ltd.

[0045] Fully automatic laminating machine, JXA-8530F PLUS, Jinan Wancai CNC Equipment Co., Ltd.; Inductively coupled plasma etching system, PlasmaPro 100, Oxford Instruments, UK; Ultraviolet radiation intensity meter, UV type, China Linshang Technology Co., Ltd.

[0046] Testing and Characterization

[0047] Surface wetting performance test

[0048] The contact angle and roll-off angle of water droplets on TSURF surfaces were measured using a KRüSS DSA25S optical contact angle analysis system. For contact angle measurements in a stationary state, a water droplet (~10 μL) was first added to the sample surface using a motor-controlled syringe. Once the droplet stabilized, a side image was captured using a camera, and the static contact angle of the water droplet on the TSURF surface was calculated using software fitting. For roll-off angle measurements, a motor-controlled rotatable test platform was used to tilt the sample, with the platform's rotation angle displayed in real time on a computer connected to the motor. At the start of the test, the initial tilt angle of the platform was maintained at 0°. After a water droplet (~10 μL) was added to the TSURF surface using the syringe, the platform was rotated by the motor. The rotation stopped the instant the droplet began to roll on the surface, and the rotation angle displayed on the computer was recorded as the roll-off angle. Measurements were taken at three different locations for each sample to minimize data error.

[0049] Scanning electron microscopy (SEM) characterization

[0050] Scanning electron microscopy observation was performed at SUPRA TMThe study was conducted using a 55° thermal field emission scanning electron microscope (Zeiss, Germany). After preparing TSURF, samples with dimensions of 2 mm × 2 mm were cut for surface morphology and cross-sectional characterization. Simultaneously, the Si elemental distribution on the TSURF surface was also scanned.

[0051] Visible light transmittance test

[0052] The transmittance of TSURF to visible light was measured using a UV-vis spectrophotometer. The test sample measured 7.5 cm × 2.5 cm, and a glass slide of the same size was used as a control sample during the test. The transmittance of air was set as the baseline for the test. The test wavelength range was 400 nm to 800 nm.

[0053] X-ray photoelectron spectroscopy (XPS) analysis

[0054] XPS analysis was performed using an X-ray photoelectron spectroscopy (Al-Kα X-rays as the laser source). The instrument parameters were set as follows: test voltage 15 kV, test power 300 W. Quantitative elemental analysis was conducted on the TSURF surface.

[0055] Mechanical stability test

[0056] Wet friction test: During the test, the friction contact of the friction testing machine is covered with coarse cotton cloth, and its contact area with the TSURF surface is approximately 0.785 cm². 2 The load mass is 1 kg. The friction contact can move a distance of 3 cm in one direction on the surface, and one reciprocating motion is defined as one friction cycle (6 cm movement). After every 10 friction cycles, 0.5 mL of ethanol or detergent medium is added to the fabric to keep the coarse cotton cloth moist. After each specific number of friction tests, the contact angle and roll-off angle of water droplets on the TSURF surface are measured to evaluate its wet friction resistance.

[0057] Dry abrasion resistance test: The dry abrasion resistance of TSURF was tested using a Taber abrasion tester according to ASTM test standard (D4060). Two 100g loaded grinding wheels were used to perform the abrasion test on a 10cm diameter TSURF surface. After each specific number of abrasion test cycles, the contact angle and roll-off angle of the water droplets on the TSURF surface were measured as indicators of the Taber abrasion resistance of the TSURF.

[0058] Adhesion Test: To test the adhesion of the coating to different substrates, we refer to GB / T 5210-2006 standard and use an adhesion tester to test the adhesion between TSURF and various substrates using the mechanical pull-adhesion method. First, the spindle and coating are bonded together using the instrument's special adhesive. After drying at room temperature for at least 72 hours to ensure complete adhesion, a cutter is used to cut around the spindle and through the coating. Then, the unloading valve on the testing machine is fully released counterclockwise. The black piston on the quick-release sleeve is pressed down to connect the quick-release sleeve to the spindle. The instrument is turned on, set to "peak test" mode, and zeroed. The unloading valve is tightened to apply pressure. The peak pressure shown at the moment the coating separates from the substrate is the adhesion force between the coating and the substrate.

[0059] Stress-strain testing: Strain-stress curve data were obtained using a universal tensile testing machine. The tested TSURF sample was 1 cm wide, 3 cm long, and approximately 90 μm thick. The testing speed was 10 mm / min.

[0060] High / Low Temperature Stability Testing: In the high / low temperature environment stability testing of TSURF, 70℃ was selected as the high temperature environment and -45℃ as the low temperature environment for subsequent testing. During the testing process, the contact angle and roll-off angle of water droplets on the TSURF surface were measured every four days to evaluate its stability.

[0061] Chemical stability test

[0062] Chemical stability tests were conducted in 2.5M strong acid (hydrochloric acid) and 2.5M strong alkali (sodium hydroxide) solutions, respectively. During the tests, TSURF was completely immersed in the solutions, and the contact angle and roll-off angle of water droplets on the TSURF surface were measured every 12 hours to assess its stability.

[0063] UV blocking performance test

[0064] We used a UV radiation meter (China Forestry Technology) to measure UV intensity. Starting from sunrise, we measured the UV intensity of the original sunlight, the UV intensity transmitted through Low-E glass, and the UV intensity transmitted through TSURF glass at selected fixed test locations, with each test interval being 15 minutes.

[0065] Weather resistance test

[0066] Weather resistance tests were conducted in an accelerated UV aging test chamber. The intensity of the simulated UV light source was kept constant at 1.38 W / m² during the test. 2 The blackboard temperature was 50℃. Simulated rainfall spraying was performed every 2 hours, lasting for 1 hour, with a spray rate of approximately 1L / h.

[0067] Dust resistance test

[0068] The dust resistance test was conducted in a dust test chamber, using premium talc powder (1250 mesh) to simulate dust. During the test, the sample was placed vertically in the chamber, and talc powder was continuously blown out from the built-in air outlet at the bottom to simulate a real dusty environment. After a specific test time, the sample was removed to observe the accumulation of dust on the surface, and then washed with running water to observe the surface's self-cleaning ability.

[0069] Photovoltaic power generation performance testing

[0070] The photovoltaic panels used in the photovoltaic power generation performance test were commercial silicon-based photovoltaic panels, and the power generation was calculated using a WT5000 power analyzer. During the test, the voltage input port was connected in parallel with the photovoltaic panel, and the current port was connected in series with the photovoltaic panel output port.

[0071] The following examples are further illustrations of the present invention, but the present invention is not limited thereto.

[0072] Example 1

[0073] Preparation and Synthesis of TSURF (High Transparency Superhydrophobic Anti-UV Film)

[0074] The preparation process of TSURF is as follows: Figure 1 As shown, a commercially available silicone pressure-sensitive adhesive (PSA) was first pressed onto the back side of a UV-resistant film using a laminator. Then, an acetone solution of PMMA mixed with hydrophobic vapor-phase nano-SiO2 was drop-coated onto the surface of the pressed PET film. After the acetone evaporated, a layer of silica-doped solid PMMA coating was formed on top of the PET film. Further hydrophobic treatment of the TSURF surface was performed using plasma gas etching with CHF3 as the working gas. During etching, some of the PMMA was etched away, while the dispersed silica was retained and formed the ends of synaptic structures, creating a hierarchical three-dimensional rough structure on the TSURF surface.

[0075] Molding process

[0076] The lamination process is carried out on a fully automatic laminating machine, where a silicone pressure-sensitive adhesive (PSA) is laminated onto one side of a polyethylene terephthalate (PET) film. The operating temperature, roller conveyor speed, and working air pressure are all set to the machine's default settings.

[0077] PMMA coating

[0078] First, polymethyl methacrylate (PMMA) was dissolved in acetone solvent, and then fumed hydrophobic nano-SiO2 was added and ultrasonicated until completely dispersed. It was then coated onto a PET surface by drop casting, and after complete evaporation of the acetone, a uniform PMMA layer was observed. In the preparation of the PMMA layer, the concentration of nano-SiO2 was 1 × 10⁻⁶. -3 g·mL -1 The PMMA mass fraction was 15 wt%, and the dropping parameters were 0.2 mL·cm. -2 Unless otherwise specified, "PET", "PET film", and "PET thin film" in this article refer to polyethylene terephthalate film that has been modified to block ultraviolet radiation, also known as a film with UV resistance.

[0079] Plasma gas etching

[0080] The plasma etching process was performed in an inductively coupled plasma (ICP) etching system. CHF3 was used as the working gas to etch and fluorinate the film to obtain a transparent superhydrophobic film. The fluorination etching process was carried out at 0°C for 20 seconds. The gas pressure was set to 0.8 Pa, the flow rate to 0.06 L / min, the upper electrode ICP power to 200 W, and the lower electrode RF power to 10 W.

[0081] After etching, TSURF exhibits excellent superhydrophobic properties and can adhere to the surfaces of various substrate materials. In addition, TSURF possesses extremely high transparency and can be fabricated on a large scale. Figure 2.a shows a photograph of TSURF adhered to a glass substrate measuring 85cm × 25cm. TSURF has an average transmittance of over 85% in the visible light region. SEM images reveal a uniformly rough nanoscale structure on the TSURF surface, allowing visible light waves to pass through with minimal reflection and scattering, thus ensuring high transparency. A cross-sectional SEM image of TSURF clearly distinguishes the PMMA, PET, and PSA layers, with a total film thickness of approximately 80μm (as shown in Figure 2.b).

[0082] Example 2

[0083] The rest is the same as in Example 1, except that the nano-SiO2 particles in the PMMA hydrophobic layer have different sizes. We dispersed hydrophobic nano-SiO2 particles of different sizes (5-40 nm) in acetone solvent of PMMA, and characterized the transmittance of the PMMA coating formed after acetone evaporation in the visible light region.

[0084] SiO2 in the PMMA hydrophobic layer has a crucial impact on the performance of TSURF. During the preparation of polymer materials with doped particles, the dispersion of micro / nano particles in the solvent is often difficult to achieve ideally, frequently resulting in irregular aggregation of these particles. This leads to the actual particle size of the filler material being larger than the theoretical particle size. Therefore, the particle size selected for preparing transparent materials needs to be strictly chosen. Especially in the preparation of transparent superhydrophobic materials, excessively small particle sizes increase transparency but may result in insufficient roughness to provide superhydrophobic properties; while excessively large particle sizes lead to a loss of transparency.

[0085] Although we did not intend to construct a superhydrophobic surface in one step in this work, selecting particles with larger sizes, while maintaining transparency as much as possible, will help achieve a more desirable roughness in subsequent fabrication processes. Figure 3 As shown, for PMMA coatings with SiO2 particles larger than 10 nm dispersed, the transmittance in the visible wavelength range drops below 80%, resulting in significant visual blurring even before etching. In contrast, although PMMA coatings with SiO2 particles of 5 nm dispersed can maintain more than 90% visible light transmittance, we ultimately chose 7 nm SiO2 as the filler to achieve the highest possible roughness, which maintains approximately 90% transmittance. PMMA coatings with SiO2 particles of 5–10 nm can achieve both high transmittance and high roughness.

[0086] Example 3

[0087] The rest is the same as in Example 1, except that the particle concentration per unit volume in the PMMA hydrophobic layer and the volume of the drop-coated solution per unit area are different.

[0088] In practice, the transmittance of visible light is determined not only by particle size, but also by the particle concentration per unit volume and the volume of the droplet solution per unit area. Experiments have shown that the average transmittance of visible light decreases with increasing particle concentration (e.g., ...). Figure 4 (as shown in a); similarly, the more solution is dropped onto a unit area, the more particles are deposited, and the lower the average transmittance of visible light (as shown in a figure). Figure 4 (As shown in .b). In the preparation of the PMMA layer, the particle concentration per unit volume is (0.4~2)×10. -3 g·mL -1 The volume of solution dropped per unit area is 0.05–0.30 mL / cm². -2 At this point, an average light transmittance of over 85% can be obtained. The particle concentration per unit volume is (0.4–1) × 10⁻⁶. -3 g·mL -1 The volume of solution dropped per unit area is 0.05–0.25 mL / cm².-2 At that time, an average light transmittance of 90% or more can be obtained.

[0089] To maintain a transmittance of approximately 90% while also considering other membrane properties, we ultimately chose a particle concentration of 1×10⁻⁶ per unit volume. -3 g·mL -1 The volume of solution dropped per unit area is 0.2 mL·cm³. -2 As the optimal parameters for PMMA layer preparation.

[0090] Example 4

[0091] Everything else is the same as in Example 1, except that the mass fraction of PMMA is different.

[0092] The mass fraction of PMMA in the solution further affects the material's properties, directly controlling the bulk distribution of nanoparticles within the material. For example... Figure 5 As shown, a higher PMMA mass fraction means a thicker PMMA layer and less SiO2 distributed per unit volume. According to Snell's law, the greater the difference in refractive index between two media, the higher the refractive index of light. Figure 5 As shown in Figure 1, after etching, higher PMMA concentration results in less surface roughness and a more uniform substrate. This is beneficial for reducing incident light scattering and improving transparency, but it also leads to reduced hydrophobicity, with water droplets typically having a contact angle of less than 150° on the surface. Conversely, for low-concentration PMMA, the situation is reversed. Figure 5 As shown in iii of section a. Therefore, only by adding an appropriate mass fraction of PMMA can a reasonable surface structure be constructed while exhibiting excellent superhydrophobicity and high transparency (e.g., ...). Figure 5 (as shown in ii of .a).

[0093] PMMA with a mass fraction of 0–30 wt% can achieve a transparency of over 85%. PMMA with a mass fraction of 10–30 wt% can achieve a transparency of over 90%.

[0094] The PMMA has a mass fraction of 0–30 wt% and a surface contact angle of ≥150°. Alternatively, the PMMA has a mass fraction of 0–20 wt% and a surface contact angle of ≥153°.

[0095] Therefore, to balance excellent superhydrophobicity and high transparency, the mass fraction of PMMA is 10-20 wt%, with the most preferred mass fraction being 15 wt%.

[0096] Example 5

[0097] The rest is the same as in Example 1, except that the etching time is different.

[0098] The hydrophobicity and transparency of TSURF are also affected by etching time. Nanoparticles exhibit a stronger scattering effect in the air phase than in the polymer; a longer etching time means more PMMA is etched by the working gas, which leads to reduced material transparency, but a corresponding increase in superhydrophobicity (e.g., ...). Figure 6 (as shown in .a). To visually demonstrate the impact of manufacturing conditions on the final material properties, we selected three samples with different etching times (0 seconds, 20 seconds, and 60 seconds) for comparison (respectively...). Figure 6 (i-iii in .b).

[0099] After exploring the experimental conditions, the optimal preparation conditions for TSURF were finally determined to be: using 7nm hydrophobic SiO2 at a ratio of 1×10⁻⁶. -3 g·mL -1 The concentration was dispersed in a solution containing 15 wt% PMMA, and then at a concentration of 0.2 mL·cm⁻¹. -2 The coating was drop-coated onto the surface of a PET / PSA film, followed by etching for 20 seconds using CHF3 as the working gas. The TSURF surface exhibited a unique hierarchical roughness structure (e.g., Figure 7 As shown in the figure, after gas etching, the aggregated SiO2 particles were not etched, and the central part was a prismatic PMMA. Furthermore, the SiO2 aggregates exhibited distributions at different depths, forming a multi-level rough structure on the surface (as shown in the figure). Figure 6 As shown in Figure .b), this layered rough structure, combined with the fluorination of CHF3, provides excellent superhydrophobic properties.

[0100] Example 6

[0101] TSURF stability test

[0102] Durability has always been a major limiting factor for the practical application of superhydrophobic materials, as it typically determines their lifespan. While numerous studies have explored improving the resistance of superhydrophobic materials to external abrasion, these investigations have generally been conducted in air. However, practical applications of superhydrophobic surfaces often require handling more complex environments, such as organic detergents or surfactant mixtures used in surface cleaning processes. Here, we tested the wet abrasion resistance of TSURF using testing equipment such as… Figure 8 As shown in .a., the test method for wet friction resistance was as follows: a wet friction test was conducted on a multifunctional ethanol friction tester (Hongjin Technology Co., Ltd., China). During the test, the friction contact of the friction tester was covered with coarse cotton cloth, and its contact area with the TSURF surface was approximately 0.785 cm². 2The friction load mass was 1 kg, and the friction head could move a distance of 3 cm in one direction on the surface. A cycle was defined as a distance of 6 cm. After every 10 cycles, 0.5 mL of ethanol or detergent was added to the fabric to keep the rubbed cotton cloth moist. Then, after a specific number of friction cycles, the contact angle and roll-off angle of water on the material surface were measured to characterize its wetting properties and measure the material's resistance to wet abrasion.

[0103] In tests using anhydrous ethanol as the wet grinding medium, after 12,800 friction cycles, the water contact angle on the TSURF surface decreased from the initial 154.68°±2.21° to 148.29°±4.47°, while the roll-off angle increased from the initial 2.13°±0.36° to 14.21°±2.43° (e.g., ...). Figure 8 (as shown in .b). We also characterized the contact hysteresis (CAH) of water droplets on TSURF. CAH is the advance contact angle (θ) of the liquid as it moves laterally on the solid surface. Adv ) and retreat contact angle (θ) Rec The difference (e.g.) Figure 8 As shown in illustration .c, this is generally considered to be related to the lateral adhesion force of droplets on the material, and can also reflect the uniformity of the material's surface structure and chemical composition. Figure 8 As shown in Figure .c, after 12,800 friction cycles, the water droplet contact angle hysteresis on the TSURF surface was only 3.81° ± 1.42°, indicating that the surface structure and chemical composition of the TSURF surface were almost undamaged during the wet abrasion test, and the lateral adhesion of water to its surface was very low.

[0104] In addition to its excellent wear resistance, TSURF also exhibits superior adhesion to various substrates (such as...). Figure 9 (As shown). We tested the adhesion of TSURF to glass, stainless steel, and acrylonitrile-butadiene-styrene (ABS) plastic surfaces. TSURF showed adhesion of up to 20.73 ± 1.71 MPa to glass with a surface rich in polar hydroxyl groups. Even on polished wood and waxed leather, adhesion reached 14.39 ± 1.21 MPa and 11.27 ± 2.46 MPa, respectively. This indicates that TSURF can be applied to a variety of substrate surfaces without easily detaching.

[0105] Example 7

[0106] TSURF's UV blocking and weather resistance

[0107] The UV protection performance of TSURF was characterized using an ultraviolet radiometer. During the test, TSURF was attached to ordinary glass (hereinafter referred to as TSURF-glass), and commercially available single-layer Low-E glass was selected as a control sample. The test period was from sunrise (07:00 AM) to sunset (17:50 PM). Every 15 minutes during the test, the solar UV intensity, the UV intensity transmitted through the Low-E glass, and the UV intensity transmitted through the TSURF-glass were measured. Figure 10 As shown, at the point of maximum light intensity, the ultraviolet radiation intensity reached 1540 μW·cm. -2 The intensity of ultraviolet light passing through Low-E glass is 854 μW·cm. -2 The ultraviolet intensity passing through TSURF-glass is only 9.6 μW·cm. -2 During testing, TSURF glass achieved an average UV blocking rate of 99.5%, while Low-E glass only achieved an average UV blocking rate of 45.8%.

[0108] In addition, to simulate the stability of TSURF in more complex environments, we conducted weathering resistance tests according to GB / T1766-95 standard. The tests were carried out in an aging test chamber, where high-intensity ultraviolet light was applied and simulated rainfall was simulated (e.g., Figure 11 As shown in the figure, this test can verify the structural strength and surface composition stability of surface materials under outdoor conditions. Aging resistance tests were conducted on pristine glass, TSURF-glass, Low-E glass, and pristine stainless steel and stainless steel with TSURF coating (hereinafter referred to as TSURF-stainless steel) under the same conditions. Figure 12 .a to Figure 12 As shown in .d, after 100 hours of testing, the surfaces of the original glass and original stainless steel had accumulated a large amount of water stains, while the TSURF-glass and TSURF-stainless steel were very clean.

[0109] For commercially available Low-E glass, some water stains also accumulate on the surface, and most importantly, it loses its original waterproof performance (e.g., Figure 13 As shown in the two images on the left), TSURF glass still maintained excellent superhydrophobic properties after testing (e.g., Figure 13 As shown in the two figures on the right, this indicates that TSURF has stronger weather resistance than the already commercialized Low-E coating, meaning that TSURF has the potential to be promoted in the architectural glass industry and achieve commercialization.

[0110] Example 8

[0111] TSURF's sand and dust resistance and self-cleaning properties

[0112] TSURF also demonstrated excellent sand / dust resistance and self-cleaning capabilities. We simulated the effects of daily dust accumulation and extreme sandstorms on the material's surface properties in a dustproof test chamber. The five samples tested included pristine glass, TSURF-glass, pristine stainless steel, and TSURF-stainless steel. The test process included 24 hours of dust blowing followed by 30 seconds of water rinsing. Figure 14 As shown, the surfaces of the original glass and stainless steel samples exhibited significant dust accumulation after testing, with a considerable amount of sand and dust residue remaining even after rinsing with water. In contrast, the surfaces of the TSURF-glass and TSURF-stainless steel samples showed only minimal dust accumulation, and their surfaces were almost completely cleaned after rinsing with water, demonstrating TSURF's superior self-cleaning ability against sand and dust.

[0113] Example 9

[0114] Performance of TSURF in photovoltaic (PV) materials

[0115] As a key component of photovoltaic (PV) power generation, the sun-facing surface of PV panels needs to be kept clean to ensure power generation efficiency. Currently, most silicon-based PV materials have requirements for visible and short-wave near-infrared light that perfectly match the optical properties of TSURF, and it can prevent ultraviolet radiation from damaging the EVA and TPE / TPT backsheet structures within the PV panel. To test the improvement of PV material surface contamination caused by TSURF's dust-resistant and self-cleaning properties, we conducted a year-long test under actual environmental conditions. The test samples were placed outdoors throughout the test, and the daily power generation changes were monitored in real time. Figure 15 .a and Figure 15 As shown in Figure .b, the surface of the PV panel with TSURF attached (hereinafter referred to as the TSURF-PV panel) is cleaner than that of the original PV panel. The original PV panel has accumulated dust and water stains from rain, while the surface of the TSURF-PV panel remains almost unchanged. This helps to ensure stable input light intensity and improve power generation efficiency. To quantify the performance of TSURF in improving the power generation efficiency of PV modules, we measured the power generation of two PV panels of the same area over a year (e.g., ...). Figure 16(As shown). In the initial stage of testing, the power generation of the TSURF-PV panel was slightly lower than that of the original PV panel, which may be due to the attenuation of incident light by SiO2 on the TSURF surface. Over time, the accumulation of surface contaminants caused more reflection and refraction of light on the surface of the original panel, reducing the actual light input and thus reducing power generation. On the other hand, the TSURF-PV panel maintained a high level of power generation due to its excellent surface self-cleaning ability, and the surface could always be kept clean. Compared with the original PV panel, the annual power generation increased by nearly 66.89%.

[0116] In summary, by adjusting the nanoparticle concentration and drop-coating parameters of the PMMA layer on PET, we effectively controlled the bulk distribution of SiO2 in the PMMA matrix. After plasma gas etching with CHF3, a nanoscale hierarchical structure was observed. Combined with a simple PSA lamination technique, a transparent TSURF with an extremely high UV reduction rate of 99.5%, wet abrasion resistance, and excellent self-cleaning properties was prepared. Furthermore, even after 12,800 cycles of ethanol wet abrasion and 300 hours of weathering tests, TSURF maintained its superhydrophobicity and withstood bending, torsional deformation, high and low temperature environments, and strong acid and alkali corrosion. The excellent adhesion of TSURF to various substrates provides it with a wide range of application options. More importantly, in response to the development trend of green energy, TSURF, with its excellent optical management and self-cleaning properties, is expected to be widely used on photovoltaic panel surfaces to improve photoelectric conversion efficiency and reduce labor costs and resource waste.

Claims

1. A method for preparing a self-cleaning, UV-resistant, transparent, superhydrophobic membrane (TSURF), comprising the following steps: S1, Press the silicone pressure-sensitive adhesive PSA onto the back side of the UV-resistant PET film; S2, drop-coat an acetone solution of PMMA mixed with hydrophobic vapor-phase nano-SiO2 onto the surface of a PET film pressed with organosilicon pressure-sensitive adhesive PSA. S3, after acetone evaporates, a layer of solid PMMA coating doped with silicon dioxide is formed on the surface of the PET film. S4, perform hydrophobic treatment on the solid PMMA coating doped with silicon dioxide formed in step S3. In step S2, the mass fraction of PMMA is 10~20 wt%; In step S2, the concentration of nano-silica per unit volume during drop coating is (0.4~2)×10⁻⁶. -3 g·mL -1 The volume of acetone solution containing PMMA mixed with hydrophobic vapor-phase nano-SiO2 drop-coated per unit area is 0.05~0.30 mL·cm⁻¹. -2 ; The processing time for step S4 is 15~25 seconds.

2. The preparation method according to claim 1, characterized in that, In step S1, the silicone pressure-sensitive adhesive (PSA) is pressed using a laminating machine.

3. The preparation method according to claim 1, characterized in that, The hydrophobication process in step S4 is accomplished using plasma gas etching with CHF3 as the working gas.

4. The preparation method according to claim 1, characterized in that, The method for preparing the acetone solution of PMMA mixed with hydrophobic vapor-phase nano-SiO2 described in step S2 involves first dissolving PMMA in acetone solvent, then adding nanoscale vapor-phase hydrophobic SiO2 and subjecting it to ultrasonic vibration until it is completely dispersed.

5. The preparation method according to claim 1, characterized in that, In step S2, the particle size of hydrophobic vapor-phase nano-SiO2 is 5~40 nm.

6. The preparation method according to claim 5, characterized in that, In step S2, the particle size of the hydrophobic vapor-phase nano-SiO2 is 5~10 nm.

7. The preparation method according to claim 5, characterized in that, In step S2, the particle size of the hydrophobic vapor-phase nano-SiO2 is 7~10 nm.

8. The preparation method according to claim 3, characterized in that, In step S4, the plasma gas etching process is carried out in an inductively coupled plasma (ICP) etching system. During the etching process, CHF3 is used as the working gas to etch and fluorinate the film to obtain a transparent superhydrophobic film. The fluorination etching temperature is -5~5 ℃, the gas pressure is set to 0.7~0.9 Pa, the working flow rate is 0.05~0.07 L / min, the upper electrode ICP power is set to 180~220 W, and the lower electrode RF power is set to 8~12 W.

9. The self-cleaning, UV-resistant, transparent, superhydrophobic membrane TSURF obtained by the preparation method according to any one of claims 1-8.

10. The self-cleaning, UV-resistant, transparent, superhydrophobic membrane TSURF as described in claim 9, characterized in that, TSURF exhibits an average transmittance of over 85% in the visible light region; the total thickness of the film is 80 µm. TSURF glass has an average UV blocking rate of up to 99.5%.

11. The application of TSURF as described in claim 9 or 10, or the application of TSURF prepared according to any one of claims 1-8, in photovoltaic (PV) materials.

Images