Bionic multilevel structure super-hydrophobic coating, preparation method and application

Abstract

The invention provides a bionic multilevel structure super-hydrophobic coating as well as a preparation method and application thereof. The bionic multilevel structure super-hydrophobic coating comprises a submillimeter layer, a micron layer and a nano layer, wherein the submillimeter layer is a substrate made of high-temperature laminated resin; the micron layer is a bulge made of high-temperature laminated resin; the raw materials of the nano layer comprise a substrate coating and a functional coating; wherein the substrate coating is prepared from epoxy resin (E-51), polydimethylsiloxane (PDMS), ethyl acetate, triethylene tetramine and a curing agent; the functional coating is prepared from the following raw materials: hydrophobic modified TiO2 nanoparticles, PDMS (Polydimethylsiloxane) and ethyl acetate. According to the bionic multilevel structure super-hydrophobic coating, the preparation method and the application, anisotropic liquid drop control performance (forward / reverse direction sliding angle difference), an adjustable liquid drop bouncing behavior and efficient resistance reduction (gt; 66%) at a high shear rate (such as 200s <-1 >) are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of coating, in particular to a biomimetic multi-level structure super-hydrophobic coating, a preparation method and application. BACKGROUND

[0002] Super-hydrophobic surfaces have broad application prospects in microfluidics, chip heat dissipation, and energy-saving fluid transmission. Currently, the main methods to construct super-hydrophobic surfaces with complex multi-level micro-nano structures include: Laser processing (such as laser direct writing, laser interference): high precision, but low processing efficiency, high cost, difficult to prepare in large area.

[0003] Template-assisted replication: relatively simple process, but limited by the fixed geometry of the mold, lack of structural adjustability, difficult to achieve customized design.

[0004] Chemical coating (such as spraying, drop coating): simple operation, but pure coating often has poor mechanical wear resistance, is easy to fail under long-term mechanical or chemical stress, and has limited control ability over the direction of liquid drop movement.

[0005] Traditional 3D printing (such as FDM, SLA, SLS): although flexible design is possible, most technologies lack sub-micron resolution and geometric precision, making it difficult to manufacture multi-level features that can achieve precise liquid drop manipulation.

[0006] The main defects of the prior art can be summarized as follows: Difficulty in integrating cross-scale structures: difficult to seamlessly integrate millimeter, micrometer, and nanometer scale features on a single surface.

[0007] Insufficient functional regulation ability: lack of precise, programmable control over surface structure (such as tilt angle, spacing), resulting in weak control over liquid drop anisotropic sliding, bouncing, and other dynamic behaviors.

[0008] Poor durability: mechanical wear resistance and chemical stability are often shortfalls, affecting actual service life.

[0009] Limited drag reduction efficiency: most surfaces cannot stably maintain air film under high shear conditions, resulting in insignificant or non-persistent drag reduction effect. SUMMARY

[0010] The present application aims to provide a biomimetic multi-level structure super-hydrophobic coating, a preparation method and application, which realizes anisotropic liquid drop manipulation performance (difference in sliding angle in forward / reverse direction), adjustable liquid drop bouncing behavior, and high-efficiency drag reduction (>66%) under high shear rate (such as 200 s -1 ).

[0011] In order to achieve the above object, the application provides a kind of bionic multistage structure super-hydrophobic coating, including sub-millimeter layer, micrometer layer, nanometer layer;Wherein, The sub-millimeter layer is the substrate made of high-temperature laminated resin; The micrometer layer is the protrusion made of high-temperature laminated resin; The raw material of nanometer layer includes substrate coating and functional coating;Wherein, the substrate coating is epoxy resin E-51, polydimethylsiloxane PDMS, ethyl acetate, curing agent, auxiliary curing agent;The raw material of functional coating is hydrophobic modified TiO2 nanoparticles, PDMS and ethyl acetate, wherein, The weight ratio of PDMS and epoxy resin is 2:5, the weight ratio of ethyl acetate and epoxy resin is 7:1, the weight ratio of curing agent and epoxy resin is 1.7:5, and the weight ratio of auxiliary curing agent and epoxy resin is 0.3:5; The mass ratio of hydrophobic modified TiO2 nanoparticles and PDMS is 1:10, and the ratio of ethyl acetate and hydrophobic modified TiO2 nanoparticles is 100-110:1.

[0012] Preferably, the angle of the protrusion β Range from 0° to 75°, the height of the protrusion ranges from 120 μm ± 10 μm; The thickness of the millimeter layer is 200 μm ± 10 μm, the micrometer layer is columnar protrusion with a height of 120 μm ± 10 μm, a length of 100 μm ± 10 μm and a width of 50 μm ± 10 μm.

[0013] Preferably, the hydrophobic modified TiO2 nanoparticles include nano-titanium dioxide, pyrophosphoric acid type titanate coupling agent and solvent in a weight ratio of 10:1:162, and acetic acid is used to adjust pH=4.

[0014] Preferably, the curing agent includes triethylene tetramine and diethylene triamine; The auxiliary curing agent is polyamide and diethylene triamine; The solvent is ethanol aqueous solution; The acid-base regulator is acetic acid; The polydimethylsiloxane can be replaced by hydrogen-containing silicone oil; The epoxy resin can be replaced by epoxy resin E-44; The ethyl acetate can be replaced by anhydrous ethanol.

[0015] A preparation method of a bionic multistage structure super-hydrophobic coating, comprising the following steps: Construction of micron / millimeter-level structures: Using high-temperature lamination resin as the printing material, according to the designed millimeter / micron layer structure, the resin layer is uniformly coated on the platform by a precision doctor blade, exposed and cured by UV light projection, and the printing platform is moved downward according to the preset layer thickness. The coating-exposure-displacement cycle is repeated to complete the formation of the complete 3D structure. The entire process is controlled by the pixel-level light pattern of DMD to obtain the substrate. Spraying the base coating: Prepare a coating solution by mixing epoxy resin E-51, polydimethylsiloxane PDMS, ethyl acetate, triethylenetetramine and curing agent according to the mass ratio. Spray the coating solution onto the surface of the substrate and cure it to form a strong epoxy-PDMS composite adhesive layer, which is the base coating. Spraying functional coating: Hydrophobically modified TiO2 nanoparticles, PDMS and ethyl acetate are mixed in proportion and ultrasonically dispersed to form a uniform dispersion. The dispersion is then sprayed onto the surface of the base coating and cured. After curing, the modified TiO2 nanoparticles are uniformly embedded in the PDMS matrix, forming nanoscale roughness on the micron-structured surface, and finally constructing a superhydrophobic coating with a sub-millimeter-micron-nano three-level hierarchical structure.

[0016] Preferably, the preparation of hydrophobically modified TiO2 nanoparticles includes the following steps: Nano-titanium dioxide was dispersed in a solvent and ultrasonically dispersed evenly. Then, pyrophosphate-type titanate coupling agent TM-2P was added to obtain a mixed solution. The pH of the mixed solution was adjusted to 4 with acetic acid. Long-chain hydrophobic groups were grafted onto the surface of the nanoparticles through the dehydration condensation reaction between the titanate alkoxy group and the hydroxyl group on the surface of TiO2. After the reaction was completed, the nanoparticles were obtained by centrifugation, washing and drying.

[0017] Preferably, the degree of curing during UV light projection exposure curing is ≥90%.

[0018] Preferably, the heat distortion temperature of the high-temperature laminated resin is 218°C at 0.45 MPa, the tensile strength is 83 MPa~93 MPa, and the flexural modulus is 3.5 GPa~4.1 GPa.

[0019] Preferably, the dehydration condensation reaction takes 2-4 hours and the temperature is 70-100℃. When spraying the base coating and the functional coating, the spraying pressure is 0.3~0.5MPa, the spraying distance is 15~25cm, and the spraying time is 10~30s per spray. When spraying the functional coating, gradually increase the temperature from room temperature to a curing temperature of 130℃-140℃ at a heating rate of 10℃ / min, and maintain the temperature at the curing temperature for 5 hours.

[0020] Application of a biomimetic multi-level superhydrophobic coating in microfluidic devices, chip heat dissipation and fluid drag reduction systems.

[0021] Therefore, the present invention employs the above-mentioned biomimetic multi-level structure superhydrophobic coating, preparation method, and application, and the technical effects are as follows: Breaking through the bottleneck of cross-scale manufacturing: By creatively combining PµSL 3D printing (precisely customizing micron / millimeter structures) and spray coating (introducing nanoscale roughness), seamless structural integration from the millimeter to the nanoscale is achieved, overcoming the difficulty of coordinating structures of different scales by traditional single technologies.

[0022] Highly adjustable and programmable functionality: Utilizing the digital manufacturing capabilities of PµSL, key parameters such as the tilt angle (β) of microprotrusions can be systematically controlled, enabling "on-demand design" of dynamic behaviors such as anisotropic sliding and controllable bouncing of droplets. High-speed cameras recorded the bouncing behavior of 5-25 μL water droplets falling from a height of 25 mm, tracking the horizontal displacement (X direction) and vertical rebound height (Z direction) at different β angles (15°-75°). The maximum horizontal displacement reached 2.87 mm at β=45°, and the maximum vertical rebound height reached 3.75 mm at β=60°.

[0023] Exceptional mechanical durability: Durability was verified by testing the water contact angle change after 0-50 cycles of reciprocating abrasion tests with 600# sandpaper, 5kPa pressure (200g load), and 50mm stroke. The microstructure printed by PµSL and the sprayed nano-coating form a strong bond through mechanical interlocking and chemical cross-linking (TiO2-coupling agent-PDMS-epoxy resin), enabling the coating to maintain a water contact angle >160° after 50 sandpaper abrasion tests, far exceeding that of ordinary superhydrophobic coatings.

[0024] Significant drag reduction performance: Using a TA Instruments DHR-3 rotational rheometer with a 26mm parallel plate, 0.5mm gap, and 25℃ environment, the drag reduction performance was achieved in the range of 0-200s. -1 At shear rates, the torque difference between coated and uncoated samples was tested, drag reduction efficiency was calculated, and the drag reduction effects at different β angles were compared with literature data. The three-level hierarchical structure effectively stabilized the gas film at a shear rate of 200 s⁻¹. -1 Under these conditions, a drag reduction efficiency of up to 66.6% was achieved, which is better than most reported disordered superhydrophobic surfaces and is applicable to the shear range of practical microfluidic operations.

[0025] Enhanced condensation heat transfer efficiency: Anisotropy and low adhesion properties facilitate rapid and directional removal of condensate droplets, prevent the formation of adiabatic liquid films, reduce interfacial thermal resistance, and provide a new approach for efficient thermal management of next-generation chips. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of a biomimetic multi-level superhydrophobic coating according to the present invention;Figure 1 (a) A scanning electron microscope image of the superhydrophobic coating magnified 20 times. Figure 1 (b) is a scanning electron microscope image of the superhydrophobic coating at 100x magnification. Figure 1 (c) is a scanning electron microscope image of the superhydrophobic coating magnified 200 times. Figure 1 (d) is a scanning electron microscope image of the superhydrophobic coating magnified 1000 times; Figure 2 The contact angle diagram of the superhydrophobic surface prepared in Example 1; Figure 3 The bounce height and horizontal displacement of droplets impacting the superhydrophobic surface prepared in Example 1; Figure 3 (a) is an image of the droplet's initial impact on the superhydrophobic surface; Figure 3 (b) is an image showing the maximum bounce height of a droplet after it impacts the superhydrophobic surface; Figure 3 (c) is a horizontal displacement image of a droplet after it impacts a superhydrophobic surface and remains completely stationary; Figure 4 The image shows the contact angle before the wear resistance test in Example 2. Figure 5 The image shows the contact angle after the wear resistance test in Example 2. Detailed Implementation

[0027] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0029] 3D printing resin: HT200 high-temperature resistant amination resin is selected. Its key performance parameters are: heat distortion temperature (0.45MPa) 218℃, tensile strength 88MPa, flexural modulus 3.8GPa, viscosity (25℃) 800±50mPa·s, to ensure the mechanical stability and high-temperature resistance of the substrate structure after printing.

[0030] Nanoparticle raw materials: TiO2 powder (particle size 60nm±5nm, purity ≥99.8%); titanate coupling agent TM-2P (purity ≥98%), used for hydrophobic modification of TiO2 surface.

[0031] Coating matrix materials: PDMS (Type 184, base adhesive to curing agent mass ratio 10:1); epoxy resin E-51 (epoxy value 0.51±0.03eq / 100g); curing agent triethylenetetramine (analytical grade, purity ≥99%); solvent ethyl acetate (analytical grade, purity ≥99.5%, water content ≤0.1%).

[0032] Auxiliary materials: anhydrous ethanol (analytical grade, purity ≥99.7%), deionized water, acetic acid (analytical grade, used to adjust pH value).

[0033] Structural design tools: SolidWorks 2022 CAD software was used to replicate the sub-millimeter macroscopic contours and micrometer-level leaf-like protrusions of snake scales. The sub-millimeter-level substrate was defined as the basic framework, and the micrometer-level columnar protrusions were defined as (120μm in height and 50μm in width). The tilt angle β between the protrusions and the substrate was adjustable to 0° (no protrusion control group), 15°, 30°, 45°, 60°, and 75°. The model was then exported to STL format to meet printing requirements. 3D printing tools and parameters: The nanoArch S140 Pro (BMF, China) PµSL printer was used, equipped with a UV LED light source with a wavelength of λ=405±5nm and a resolution of 1920×1080 pixels and a digital micromirror device (DMD).

[0034] The raw materials and tools used in the following two embodiments are the same as those described above.

[0035] Example 1 1. Printing and fabricating micron-to-submillimeter hierarchical structure substrates, including: 1.1 Model Design and Export: Using the scales of the Gabonese viper from West Africa as a template, a biomimetic array model was designed using SolidWorks 2022. The micro-protrusions have a β=45°, a height of 120μm±10μm, a side length of 100μm±10μm, a width of 50μm±10μm, a spacing of 100μm, and a base size of 20mm×20mm×2mm. The model was exported in STL format and imported into slicing software.

[0036] 1.2 Pre-treatment before printing: Degas HT200 resin at 60℃ for 30 minutes, clean the printing platform with anhydrous ethanol and blow dry.

[0037] 1.3. Print using the above printing tools and parameters, with a layer thickness of 30μm, an exposure time of 200ms, and a printing speed of 5mm / h.

[0038] 1.4 Post-printing processing: Ultrasonic cleaning with anhydrous ethanol for 10 min (100W), curing in an 80℃ oven for 2 h, Shore hardness D≥85.

[0039] 2. Coating preparation (spraying + curing) 2.1 Preparation of titanate-modified TiO2 nanoparticles 5g TiO2 was dispersed in 450mL of ethanol / water (9:1) and sonicated at 150W and 40kHz for 1h to obtain a dispersion solution. 0.3 g of TM-2P was added to the dispersion solution, and the pH was adjusted to 4.0 ± 0.1 with acetic acid. The mixture was stirred at 80 °C ± 2 °C for 4 h (300 r / min). After centrifugation at 8000 r / min for 10 min, the particles were washed three times with anhydrous ethanol and twice with deionized water, dried under vacuum at 60 °C for 12 h, and ground through a 200-mesh sieve to obtain modified TiO2 nanoparticles. Long-chain hydrophobic groups were grafted onto the surface of the nanoparticles through the dehydration condensation reaction of titanate alkoxy groups with the hydroxyl groups on the TiO2 surface.

[0040] 2.2 Base Coating Spraying and Curing Preparation of coating solution: Dissolve 5g of epoxy resin E-51 in 35g of ethyl acetate, then add 2g of PDMS base adhesive, followed by 1.7g of triethylenetetramine and 0.3g of curing agent, and stir sequentially at 200r / min for 65min; Spraying parameters: Use a 0.5mm nozzle spray gun, apply 0.3-0.5MPa pressure, spray at a distance of 20cm±1cm, at a speed of 10cm / s, and spray crosswise for 5 minutes; Curing: Heat to 130℃ at 5℃ / min and hold for 5 hours to form a strong epoxy-PDMS composite adhesive layer, providing a stable interface for subsequent nanostructure deposition.

[0041] 2.3 Functional Coating Spraying and Curing Preparation of dispersion: 0.3g modified TiO2 nanoparticles, 3g PDMS and 32g ethyl acetate were mixed uniformly by ultrasonication at 150W for 30min (aggregates ≤500nm) to obtain dispersion; The functional coating was sprayed onto the surface of the base coating using the same spraying parameters as the base coating. The wet film thickness of the functional coating after spraying was approximately 30 μm. The functional coating wet film was cured at 130℃±2℃ for 5 hours to form a three-level superhydrophobic coating of "submillimeter-micrometer-nanometer".

[0042] like Figure 1 As shown, the characteristics of the resulting coating are: It has a three-level hierarchical structure consisting of micron / millimeter-level protrusions printed by PµSL and nanoscale roughness introduced by spraying.

[0043] The tilt angle (β) of the micron-sized protrusions can be precisely adjusted from 0° to 75°, with 45° and 60° being preferred.

[0044] The coating surface exhibits excellent superhydrophobicity (water contact angle >160°, for example, 163.2°±1.3° when β=45°) and anisotropy (positive sliding angle <10°, negative sliding angle >25°).

[0045] Performance testing Test environment: Ambient temperature 25℃±1℃, relative humidity 50%±5%; Core equipment: Contact angle measuring instrument (DSA25E, KRÜSS GmbH), high-speed camera.

[0046] wettability test 5 μL of deionized water was drawn up with a microsyringe and dropped onto three different random locations on the surface of the tertiary superhydrophobic coating. After standing for 10 seconds, the droplet images were taken using a contact angle meter and the contact angles were calculated. The average value was then taken. Adjust the tilt angle of the sample stage of the measuring instrument and record the angle (sliding angle) when the droplet starts to roll. Similarly, test three positions and take the average value. Results: The water contact angle was 160.8°±2.5°, and the forward sliding angle (along the tilt direction of the micro-protrusion) was 8.2°±0.8°, meeting the definition of superhydrophobic performance (contact angle ≥150°, sliding angle ≤10°). Figure 2 As shown.

[0047] Droplet manipulation performance test Use a microsyringe to draw 10 μL of deionized water and drop it vertically onto the coating surface from a height of 25 mm. The entire process of a droplet sliding was captured using a high-speed camera, and the displacement of the droplet's center was tracked using image analysis software to calculate the horizontal sliding distance and bounce height. Results: The droplet contacted the coating in 5 ms, began directional contraction in 25 ms, and rebounded for the first time in 85 ms; the horizontal displacement reached 2.87 mm ± 0.10 mm (optimal), and the vertical rebound height was 3.70 mm ± 0.10 mm. Figure 3 As shown.

[0048] Example 2 The preparation method is the same as in Example 1, with the following differences: The tilt angle of the micro-protrusion in 1.1 of Example 1 is modified to β=75°; The amount of TM-2P added to the dispersion in Example 1, 2.1 was modified to 0.35g.

[0049] The amount of PDMS in Example 1, 2.2 was modified to 2.5g, the cross-spraying time was modified to 12min, the curing temperature was modified to 130℃, and the curing time was modified to 6h.

[0050] The curing temperature in Example 1, section 2.3 was modified to 130°C, and the curing time was modified to 6 hours.

[0051] Mechanical abrasion resistance test was performed on the superhydrophobic surface in Example 2. The superhydrophobic surface sample was fixed on the abrasion resistance testing instrument platform, covered with 600# sandpaper, and a pressure of 5 kPa was applied above the sandpaper (achieved by a 200g weight, with a contact area of ​​4 cm²). 2 ); The test stroke is set to 50mm, and the reciprocating motion is one cycle. A total of 50 cycles are tested. After every 10 cycles, the water contact angle of the coating surface is tested and the performance changes are recorded. Results: After 50 wear cycles, no obvious wear marks were observed on the coating surface, and the water contact angle remained at 152.3°±3.1°, indicating no loss of superhydrophobic properties and excellent mechanical durability. Figure 4 and Figure 5 As shown.

[0052] Superhydrophobic coatings can be used in applications requiring efficient droplet manipulation, drag reduction, and thermal management, such as: 1) Chip thermal management and heat dissipation of electronic devices: The superhydrophobic coating is applied to the chip surface or the inner wall of the heat dissipation channel. By utilizing its directional droplet transport capability, the tiny water droplets generated by condensation will quickly gather into droplets on the coating surface and slide off the surface in a directional manner along the tilt direction of the micro-protrusions. This avoids the increase in thermal resistance caused by the formation of a continuous liquid film, while reducing the interfacial thermal resistance, improving the condensation heat exchange efficiency, and solving the overheating problem of high-power chips during long-term operation.

[0053] 2) Microfluidic devices and directional droplet manipulation (e.g., biochemical detection chips, microreactors): By integrating coatings into the inner walls of microfluidic channels or reaction regions, and adjusting the angle of microprotrusions printed with PμSL, directional droplet transport, precise splitting, and controllable bouncing can be achieved. For example, in biochemical detection, no external force (such as pumps or electric fields) is required; sample droplets can slide along a preset path to the detection area solely based on surface anisotropy, or droplet mixing can be achieved through vertical bounce. In microreactors, the residence time and contact sequence of reaction droplets can be controlled, improving reaction efficiency and detection accuracy.

[0054] 3) Energy-saving fluid transport systems (such as microchannels and pipelines): This coating is applied to the inner wall of the pipeline or the fluid contact surface. Utilizing its high drag reduction efficiency, it stably captures the air layer through a three-stage structure, reducing viscous friction between the fluid and the solid surface. For example, in micro-pump systems, drag reduction can lower drive energy consumption and increase fluid flow rate; in low-flow-rate industrial pipelines, it can reduce media transport resistance, lower pump operating load, and reduce energy consumption over long-term use; on the surface of small underwater vehicles, it can reduce water friction resistance and improve navigation efficiency.

[0055] Therefore, this invention adopts the above-mentioned biomimetic multi-level superhydrophobic coating, preparation method and application, creatively combining PµSL 3D printing (precisely customizing micron / millimeter structures) and spray coating (introducing nanoscale roughness), to achieve seamless structural integration from millimeter to nanoscale, overcoming the problem that traditional single technology is difficult to coordinate structures of different scales.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A biomimetic multi-level structure superhydrophobic coating, characterized in that, Including submillimeter layers, micrometer layers, and nanometer layers; among them, The submillimeter layer is a substrate made of high-temperature laminated resin; The micron layer consists of protrusions made of high-temperature laminated resin. The raw materials for the nanolayer include a base coating and a functional coating; the base coating consists of epoxy resin E-51, polydimethylsiloxane (PDMS), ethyl acetate, a curing agent, and an auxiliary curing agent; the raw materials for the functional coating are hydrophobically modified TiO2 nanoparticles, PDMS, and ethyl acetate. The weight ratio of PDMS to epoxy resin is 2:5, the weight ratio of ethyl acetate to epoxy resin is 7:1, the weight ratio of curing agent to epoxy resin is 1.7:5, and the weight ratio of auxiliary curing agent to epoxy resin is 0.3:

5. The mass ratio of hydrophobically modified TiO2 nanoparticles to PDMS is 1:10, and the ratio of ethyl acetate to hydrophobically modified TiO2 nanoparticles is 100~110:

1.

2. The biomimetic multi-level structure superhydrophobic coating according to claim 1, characterized in that, The angle of the protrusion β The range is 0°-75°, and the height range of the protrusion is 120μm±10μm; The millimeter layer is 200μm±10μm thick, and the micrometer layer consists of columnar protrusions with a height of 120μm±10μm, a length of 100μm±10μm, and a width of 50μm±10μm.

3. The biomimetic multi-level structure superhydrophobic coating according to claim 1, characterized in that, The hydrophobically modified TiO2 nanoparticles are formulated with nano-titanium dioxide, pyrophosphate-type titanate coupling agent, and solvent in a weight ratio of 10:1:162, and the pH is adjusted to 4 using acetic acid.

4. The biomimetic multi-level structure superhydrophobic coating according to claim 1, characterized in that, Curing agents include triethylenetetramine and diethylenetriamine; The auxiliary curing agents are polyamide and diethylenetriamine; The solvent is an aqueous solution of ethanol; The acid-base regulator is acetic acid; Polydimethylsiloxane can be replaced with hydrogen-containing silicone oil; Epoxy resin can be replaced with epoxy resin E-44; Ethyl acetate can be replaced with anhydrous ethanol.

5. A method for preparing a biomimetic multi-level structured superhydrophobic coating, characterized in that, Includes the following steps: Construction of micron / millimeter-level structures: Using high-temperature lamination resin as the printing material, according to the designed millimeter / micron layer structure, the resin layer is uniformly coated on the platform by a precision doctor blade, exposed and cured by UV light projection, and the printing platform is moved downward according to the preset layer thickness. The coating-exposure-displacement cycle is repeated to complete the formation of the complete 3D structure. The entire process is controlled by the pixel-level light pattern of DMD to obtain the substrate. Spraying the base coating: Prepare a coating solution by mixing epoxy resin E-51, polydimethylsiloxane PDMS, ethyl acetate, triethylenetetramine and curing agent according to the mass ratio. Spray the coating solution onto the surface of the substrate and cure it to form a strong epoxy-PDMS composite adhesive layer, which is the base coating. Spraying functional coating: Hydrophobically modified TiO2 nanoparticles, PDMS and ethyl acetate are mixed in proportion and ultrasonically dispersed to form a uniform dispersion. The dispersion is then sprayed onto the surface of the base coating and cured. After curing, the modified TiO2 nanoparticles are uniformly embedded in the PDMS matrix, forming nanoscale roughness on the micron-structured surface, and finally constructing a superhydrophobic coating with a sub-millimeter-micron-nano three-level hierarchical structure.

6. The method for preparing a biomimetic multi-level structure superhydrophobic coating according to claim 5, characterized in that, The preparation of hydrophobically modified TiO2 nanoparticles includes the following steps: Nano-titanium dioxide was dispersed in a solvent and ultrasonically dispersed evenly. Then, pyrophosphate-type titanate coupling agent TM-2P was added to obtain a mixed solution. The pH of the mixed solution was adjusted to 4 with acetic acid. Long-chain hydrophobic groups were grafted onto the surface of the nanoparticles through the dehydration condensation reaction between the titanate alkoxy group and the hydroxyl group on the surface of TiO2. After the reaction was completed, the nanoparticles were obtained by centrifugation, washing and drying.

7. The method for preparing a biomimetic multi-level structure superhydrophobic coating according to claim 5, characterized in that, The degree of curing during UV light projection exposure curing is ≥90%.

8. The method for preparing a biomimetic multi-level structure superhydrophobic coating according to claim 5, characterized in that, The heat distortion temperature of the high-temperature laminated resin is 218℃ at 0.45MPa, the tensile strength is 83MPa~93MPa, and the flexural modulus is 3.5GPa~4.1GPa.

9. The method for preparing a biomimetic multi-level structure superhydrophobic coating according to claim 5, characterized in that, The dehydration condensation reaction takes 2-4 hours and is carried out at a temperature of 70-100℃. When spraying the base coating and the functional coating, the spraying pressure is 0.3~0.5MPa, the spraying distance is 15~25cm, and the spraying time is 10~30s per spray. When spraying the functional coating, gradually increase the temperature from room temperature to a curing temperature of 130℃-140℃ at a heating rate of 10℃ / min, and maintain the temperature at the curing temperature for 5 hours.

10. Application of a biomimetic multi-level superhydrophobic coating in microfluidic devices, chip heat dissipation and fluid drag reduction systems.

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