Bionic composite resistance and noise reduction layer structure and preparation method and application thereof

Abstract

The invention discloses a bionic composite resistance and noise reduction layer structure and a preparation method and application thereof, and belongs to the technical field of underwater equipment. The structure comprises a flexible layer and a polymer brush layer, the flexible layer is used for being combined with a substrate, an array of micron-scale microstructures is arranged on the surface of the flexible layer, the surface of the flexible layer is connected with the polymer brush layer, and the polymer brush layer can form a hydration layer with water molecules; the material of the flexible layer comprises one or more of polyurethane, polyurea and polydimethylsiloxane; the flexible layer contains a photoinitiator; the polymer brush layer includes one or more of a zwitterionic polymer and a neutral polymer. The flexible layer can absorb turbulent kinetic energy of a flow field in a near-wall area and absorb pressure pulsation in the flow field; the microstructure can achieve the resistance reduction effect by increasing the distance between the wall surface and the turbulent vortex; the polymer brush layer enables fluid to slide on the wall surface, formation of gas nuclei can be inhibited, and cavitation noise can be effectively reduced. And the sailing efficiency and the mute performance of the ship can be obviously improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of underwater equipment, and in particular relates to a bionic composite drag and noise reduction layer structure and a preparation method and application thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] Ship navigation is affected by seawater resistance, which can be primarily composed of pressure resistance and viscous resistance. Pressure resistance depends on the ship's external shape; friction resistance accounts for a significant portion of viscous resistance, accounting for 60% to 80% of total resistance. For ships with the same power and range, a 10% reduction in friction resistance can save approximately 3.75% of energy. Medium- and low-speed, large transport vessels are more significantly affected by friction resistance, and reducing friction resistance presents a promising prospect. The field of ship drag reduction technology primarily encompasses active and passive approaches. Active drag reduction relies on the continuous injection of air or polymer drag reducers, which significantly increases material costs and energy consumption. Among passive drag reduction technologies, microstructured surfaces and flexible surfaces are widely used. However, due to their single mechanism of action, the drag reduction effect of a single drag reduction technology is limited. Furthermore, microstructured surfaces are highly susceptible to biofouling, and once damaged, the drag reduction effect is lost.

[0004] The radiated noise generated by ships not only seriously affects the basic life activities of marine life but also disrupts the normal work and daily lives of crew members. For underwater vehicles with specialized missions, such as submarines, noise can also reduce their stealth and survivability, affecting their sonar detection performance. Currently, ship propeller noise control primarily involves optimizing the number and structure of blades. However, due to the complexity of technical modifications, this approach is difficult to apply to noise reduction improvements on existing ships. Furthermore, there is currently no effective method for reducing flow-induced noise on the ship's surface, a problem that urgently needs to be addressed to further improve ship noise reduction performance.

[0005] During navigation, the surface of a ship will be attached by non-living substances such as proteins and polysaccharides, as well as various marine organisms such as bacteria, algae, mussels, and barnacles. These marine biofoulings attached to the ship will significantly increase its navigation resistance, reduce its speed and stealth. Marine organisms produce acidic metabolites such as sulfides and sulfates, which accelerate the corrosion of the hull and shorten the service life of the ship. The current main response method is to combine metal ions such as tin, cuprous, and zinc with organic biocides to kill marine fouling organisms to achieve a good anti-fouling effect. However, metal antifouling agents have non-targeted biological toxicity and will have a harmful impact on the marine ecosystem. They are transmitted along the food chain and may also pose a potential threat to human health. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a biomimetic composite drag and noise reduction layer structure, its preparation method, and its application. The developed "flexible layer-microtexture-polymer brush" composite layer significantly enhances drag and noise reduction. The polymer brush layer also attracts water molecules for directional alignment, forming a dense hydration layer that effectively resists the adhesion of marine organisms and maintains the integrity of the microstructure, thereby achieving long-term drag reduction.

[0007] In order to achieve the above object, the technical solution of the present invention is: In a first aspect, the present invention provides a biomimetic composite drag and noise reduction layer structure, comprising a flexible layer and a polymer brush layer, wherein the flexible layer is used to be bonded to a substrate, an array of micron-scale microstructures is provided on the surface of the flexible layer, and a polymer brush layer is connected to the surface of the flexible layer, wherein the polymer brush layer can form a hydration layer with water molecules; The flexible layer material includes one or more of polyurethane, polyurea and polydimethylsiloxane; the flexible layer contains a photoinitiator; and the polymer brush layer includes one or more of zwitterionic polymer and neutral polymer.

[0008] In a second aspect, the present invention provides a method for preparing the above-mentioned biomimetic composite drag and noise reduction layer structure, comprising the following steps: S1, processing a micro-texture array on the surface of a hard template, forming a flexible layer raw material on the hard template and then demolding it to obtain a flexible layer; S2, soaking the flexible layer in a solution containing a photoinitiator for a set time to obtain a flexible layer containing the photoinitiator; S3. Immersing the flexible layer containing a photoinitiator into a polymer monomer solution of a set concentration to initiate a photopolymerization reaction to prepare a polymer brush layer, thereby obtaining a biomimetic composite drag and noise reduction layer structure.

[0009] In a third aspect, the present invention provides applications of the above-mentioned bionic composite drag and noise reduction layer structure, including: use on the underwater surface of the hull, the propeller surface or the inner wall of the seawater circulation cooling pipe.

[0010] The beneficial effects of the present invention are: 1. The present invention creatively simulates the unique three-layer structure of sharks' "skin-scales-mucus" and develops a "flexible layer-microtexture-polymer brush" composite layer. This structural design not only simulates nature's efficient drag reduction mechanism, but also achieves an optimized combination of multiple functions through the synergistic effect of the flexible layer, microstructure and polymer brush layer. The flexible layer can absorb the turbulent kinetic energy of the flow field in the near-wall area, delay the transition of the boundary layer fluid from laminar flow to turbulent flow, reduce the resistance of seawater, and effectively absorb pressure pulsations in the flow field, reduce the excitation effect of turbulence on the hull, and reduce ship noise. The microstructure can achieve a drag reduction effect by increasing the distance between the wall and the turbulent vortex and reducing the velocity gradient in the near-wall area. The microstructure can achieve a noise reduction effect by reducing the turbulent kinetic energy in the near-wall area; the polymer brush layer can cause the fluid to slip on the wall, thereby achieving the purpose of drag reduction. The hydrophilic polymer brush layer can inhibit the formation of air cores. When used on the surface of rotating mechanical blades such as propellers, it can effectively reduce cavitation noise. In particular, the polymer brush layer can attract water molecules to form a dense hydration layer, effectively preventing the attachment of marine organisms, thereby maintaining the integrity of the microstructure and achieving a long-term drag reduction effect. This multifunctional integrated design provides a comprehensive solution for improving the comprehensive performance of ships. The flexible layer, microstructure and polymer brush layer each have different mechanisms of action, but they are independent of each other and do not interfere with each other. This synergistic effect makes the composite layer structure perform well in drag reduction and noise reduction, significantly improving the navigation efficiency and quietness of the ship.

[0011] 2. The polymer brush layer in the present invention is grafted onto the flexible layer. The hydrated layer formed due to its hydrophilic properties can exist for a long time, eliminating the need for continuous replenishment of polymer drag reducers, and significantly reducing material costs and energy consumption.

[0012] 3. Compared with traditional antifouling technologies, the composite layer of this invention avoids the use of metallic antifouling agents that are harmful to marine ecosystems, reducing negative impacts on the marine environment and meeting the requirements of sustainable development. This composite layer structure is not only suitable for new ships but can also be used to upgrade and retrofit existing ships, offering broad market application prospects and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0014] Figure 1 Schematic diagram of the structure of the shark skin surface layer and the bionic composite drag and noise reduction layer structure in Example 1 of the present invention; (a) the shark skin surface layer structure, (b) the bionic composite drag and noise reduction layer structure.

[0015] Figure 24 is a diagram showing the test results of the drag reduction effect in a specific embodiment of the present invention.

[0016] Figure 3 It is a structural schematic diagram of the experimental bench used in the noise reduction effect test process in a specific embodiment of the present invention.

[0017] Figure 4 1 is a noise reduction effect test result diagram in a specific embodiment of the present invention.

[0018] Figure 5 1 and 2 are graphs showing the antifouling performance test results of a specific embodiment of the present invention, (a) is a graph showing the test results of Comparative Example 1, and (b) is a graph showing the test results of Example 1. DETAILED DESCRIPTION

[0019] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0020] Unless otherwise defined, all professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. The reagents or raw materials used in the present invention can be purchased through conventional channels. Unless otherwise specified, the reagents or raw materials used in the present invention are used in a conventional manner in the art or according to the product instructions. In addition, any methods and materials similar to or equivalent to those described herein can be applied to the present invention. The preferred embodiments and materials described herein are for demonstration purposes only.

[0021] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0022] One or more embodiments of the present invention provide a biomimetic composite drag and noise reduction layer structure, comprising a flexible layer and a polymer brush layer. The flexible layer is used to bond to a substrate, and an array of micron-scale microstructures is provided on the surface of the flexible layer. The polymer brush layer is connected to the surface of the flexible layer, and the polymer brush layer can form a hydration layer with water molecules. The flexible layer material includes one or more of polyurethane, polyurea and polydimethylsiloxane; the flexible layer contains a photoinitiator; and the polymer brush layer includes one or more of zwitterionic polymer and neutral polymer.

[0023] In this field, "polymer brush" is a polymer material with a special topological structure, which is composed of side chains grafted densely on the polymer main chain or the surface of the substrate, forming a brush-like extended conformation due to the steric effect.

[0024] In the above structure, the flexible layer can absorb the turbulent kinetic energy of the flow field near the wall, delay the transition of the boundary layer fluid from laminar flow to turbulent flow, and thus reduce the resistance of seawater. At the same time, the flexible layer can effectively absorb the pressure pulsation in the flow field, reduce the excitation effect of turbulence on the hull, and thus reduce the noise of the ship; the microstructure can reduce the velocity gradient in the near-wall area by increasing the distance between the wall and the turbulent vortex, thereby achieving a drag reduction effect. In addition, the microstructure can achieve a noise reduction effect by reducing the turbulent kinetic energy in the near-wall area; the polymer brush layer can cause the fluid to slip on the wall, thereby achieving the purpose of drag reduction. The hydrophilic polymer brush layer can inhibit the formation of air cores, and when used on the surface of rotating machinery blades such as propellers, it can effectively reduce cavitation noise. In addition, the polymer brush layer can attract water molecules to form a hydration layer, resist the adhesion of marine organisms, prevent the occurrence of marine fouling, ensure the integrity of the microstructure, and thus achieve the long-term effect of the composite layer structure; the flexible layer, microstructure and polymer brush layer each have different action mechanisms and work synergistically with each other. This synergistic effect enables the composite layer structure to perform well in drag reduction and noise reduction, significantly improving the navigation efficiency and quietness of the ship.

[0025] Optionally, the elastic modulus of the flexible layer is between 1.0-1.5 MPa and is flexible; the thickness of the flexible layer is 0.5~3 mm, and the thickness is determined according to the usage scenario. When used on the inner wall of the pipe, the thickness needs to be smaller to avoid reducing the pipe diameter; when used on other surfaces, the thickness can be slightly larger to improve the drag reduction effect.

[0026] Optionally, the shape of the microstructure includes one or more of protrusions, pits and grooves; the protrusions include one or more of rectangular ribs and triangular ribs; the protrusions and pits are distributed in a lattice, the length of the groove is much larger than the cross-sectional size of the groove, and it is a microstructure that penetrates within a set length on the surface of the flexible layer; the microstructure can increase the distance between the wall and the turbulent vortex to achieve a drag reduction effect, and can also achieve a noise reduction effect by reducing the turbulent kinetic energy in the near-wall area.

[0027] Optionally, the photoinitiator includes one or more of benzophenone and 2-hydroxy-2-methyl-1-phenyl-1-propanone, etc., which are used to connect the zwitterionic polymer and / or neutral polymer to the flexible layer with microstructure in a grafting manner.

[0028] Optionally, the thickness of the polymer brush layer is 10-500 nm, and the specific size is determined according to the requirements of drag reduction or anti-fouling.

[0029] Optionally, the zwitterionic polymer includes a polymer formed by one or more of phosphorylcholine, carboxylic acid betaine and sulfobetaine, preferably a polymer of methacryloylethyl sulfobetaine; the neutral polymer includes a polymer formed by one or more of polyacrylamide and polyethylene glycol; the polymer can attract water molecules to form a hydration layer, can convert solid-liquid friction into liquid-liquid friction, thereby causing the fluid to slip on the wall surface, thereby achieving a drag reduction effect; it can also inhibit the formation of gas nuclei, and when used on the surface of rotating mechanical blades such as propellers, effectively reduce cavitation noise; the hydration layer can avoid direct contact between non-biological substances such as proteins and polysaccharides and the hull material, prevent the adhesion of marine organisms and the occurrence of marine fouling, ensure the integrity of the microstructure of the bionic composite drag reduction and noise reduction layer structure, and thus achieve the long-term effect of the composite layer structure.

[0030] One or more embodiments of the present invention provide a method for preparing the above-mentioned biomimetic composite drag and noise reduction layer structure, comprising the following steps: S1, processing a micro-texture array on the surface of a hard template, forming a flexible layer raw material on the hard template and then demolding it to obtain a flexible layer; S2, soaking the flexible layer in a solution containing a photoinitiator for a set time to obtain a flexible layer containing a photoinitiator; S3. Immersing the flexible layer containing a photoinitiator into a polymer monomer solution of a set concentration to initiate a photopolymerization reaction to prepare a polymer brush layer, thereby obtaining a biomimetic composite drag and noise reduction layer structure.

[0031] In the above process, a flexible layer with a microstructure is first prepared using a template, and then a photo-initiated polymerization reaction is used to add the polymer to the surface of the flexible layer in a grafting manner, thereby realizing the direct combination of the flexible polymer material layer and the nano-thick polymer brush layer to obtain a bionic composite drag and noise reduction layer structure.

[0032] Optionally, in S1, the surface of the hard template is hydrophobically treated to facilitate demoulding of the flexible layer.

[0033] Optionally, in S1, the forming process includes: after removing bubbles by vacuum, keeping warm at 80-100°C for 1-1.5 hours to obtain a dense and uniformly thick flexible layer.

[0034] Optionally, in S2, the concentration of the solution containing the photoinitiator is 3~8wt%, the solvent is selected from one or more of n-hexane and dichloromethane, the immersion time is 2~4h, and the residual solvent on the surface is removed after immersion; so that the photoinitiator remains evenly in the flexible layer with microstructure.

[0035] Optionally, in S3, a catalyst is added to the polymer monomer solution, and the catalyst includes one or more of ammonium cerium nitrate, ammonium persulfate and hydrogen peroxide, which is used to catalyze the polymerization reaction.

[0036] Optionally, in S3, the method of initiating the photopolymerization reaction includes: irradiating with ultraviolet light for 6 to 9 hours. The method is simple and easy and will not affect the properties of the flexible layer itself.

[0037] One or more embodiments of the present invention provide applications of the above-mentioned bionic composite drag and noise reduction layer structure, including: application to the underwater surface of a hull, the surface of a propeller, or the inner wall of a seawater circulation cooling pipe.

[0038] The bionic composite drag and noise reduction layer structure avoids the use of metal antifouling agents that are harmful to the marine ecosystem, reducing the negative impact on the marine environment. It is not only suitable for newly built ships, but also for the upgrading and transformation of existing ships.

[0039] The bonding method of the bionic composite drag and noise reduction layer structure and the substrate includes: bonding with an adhesive.

[0040] Example 1 In the ocean, sharks can easily reach speeds of 60 km / h without making much noise, and are less susceptible to the attachment and colonization of marine organisms than large marine organisms such as whales. This is because the surface layer of shark skin is Figure 1 As shown in (a), the soft shark skin can suppress and absorb pressure pulsations, resulting in a delay in boundary layer transition and a drag and noise reduction effect; the structure of the shark shield scales can prevent the formation of vortices and inhibit the development of turbulence, thereby improving the stability of the boundary layer and reducing the flow noise caused by turbulence; in addition, the mucus secreted by sharks can reduce boundary friction resistance and have a drag and noise reduction effect, and can effectively prevent the attachment and colonization of marine organisms.

[0041] This embodiment provides a bionic composite drag and noise reduction layer structure based on the bionic design of shark skin. The preparation method includes: S1. Use nano-laser processing equipment to process micro-texture arrays on opaque metals (such as aluminum alloys, stainless steel, titanium alloys, etc.) or plastics (acrylic, Teflon, etc.). The height of the microstructure is changed by changing the number of processing times and pulse width, thereby completing the processing of the microstructure template. In this embodiment, a black acrylic sheet template is used. The processed micro-texture shape is a spike-like micro-protrusion structure. The flow direction spacing and span direction spacing of the micro-protrusions are both 300 microns. The micro-texture template is immersed in octadecyltriethoxysilane for hydrophobic treatment to facilitate subsequent demolding. Polydimethylsiloxane (PDMS) is used as the raw material for preparing the flexible material. A commercially available product (model: Sylgard) is used. 184), according to the preparation method of PDMS, component A (PDMS) and component B (curing agent) were mixed in a ratio of 10:1 and poured into the microstructure template, and then a vacuum pump was used to evacuate the air to remove the bubbles in the PDMS; the microstructure template with PDMS was then heated at 80°C for 1h, and after demolding, a flexible layer with a microstructure array was obtained, and the shape / array density of the microstructure was consistent with the microtexture on the template.

[0042] S2. Use benzophenone as a photoinitiator and n-hexane as a solvent to prepare a benzophenone solution with a concentration of 5wt%. Soak the flexible layer prepared in S1 in the benzophenone solution for 2 hours to allow the benzophenone to evenly penetrate into the PDMS flexible layer, providing active ingredients for subsequent photoinitiated polymerization. After the soaked flexible layer is taken out, it is cleaned with organic solvents such as ethanol to remove residual n-hexane and other impurities on the surface. After cleaning, the flexible layer is dried to ensure that the organic solvent on the surface and inside of the sample is completely volatilized, thereby obtaining a PDMS flexible layer containing a photoinitiator.

[0043] S3. Utilize the sub-surface initiation process and adopt the "grafting-from" method to use methacryloylethyl sulfobetaine as the polymer monomer, and polymerize under ultraviolet light initiation conditions to form a hydrophilic polymer brush layer, specifically including: mixing the polymer monomer and deionized water in a ratio of 1g:10mL, and adding ammonium cerium nitrate as a catalyst at a ratio of 1% of the mass of the polymer monomer to prepare a polymer monomer solution; immerse the PDMS flexible layer containing the photoinitiator obtained in S2 in the polymer monomer solution, and irradiate it with ultraviolet light with a wavelength of 365nm for 6h. During this process, the photoinitiator initiates the polymerization reaction under the action of ultraviolet light, so that the polymer monomer is polymerized on the microstructure surface of the PDMS flexible layer. After the reaction is completed, the sample is taken out from the reaction solution and washed with deionized water several times to remove the reaction solution and other impurities remaining on the surface. After washing, the sample is dried to obtain the following. Figure 1 The bionic composite drag and noise reduction layer shown in (b) is referred to as "composite coating" in the following performance tests.

[0044] After testing, it was found that the thickness of the flexible layer of the obtained bionic composite drag and noise reduction layer was 2 mm, the elastic modulus was 1.2 MPa, and the thickness of the polymer brush layer was 200 nm.

[0045] With copper alloy as the substrate and epoxy resin as the adhesive, the bionic composite drag and noise reduction layer is attached to the surface of the copper alloy.

[0046] Example 2 A bionic composite drag and noise reduction layer structure is provided, which differs from Example 1 in that polyacrylamide is used as a neutral polymer monomer to prepare the polymer brush layer, and other raw materials and preparation methods are the same as those in Example 1.

[0047] Comparative Example 1 This comparative example directly uses the copper alloy used as the substrate in Example 1, and its surface roughness Ra is 0.6 μm.

[0048] Comparative Example 2 In this comparative example, the raw materials of the flexible layer in Example 1 and the vacuum and heat curing method are used to prepare a comparative flexible layer without microstructure, referred to as the "flexible layer" in the following performance tests. The thickness is the same as that of the flexible layer in Example 1, and it is combined with a substrate.

[0049] Comparative Example 3 In this comparative example, the method of S1 in Example 1 was used to prepare a flexible layer with a microstructure array, and the flexible layer was combined with a substrate, referred to as "microstructure" in the following performance tests.

[0050] Comparative Example 4 In this comparative example, the same raw materials as in Example 1 were used to prepare a polymer brush layer on a substrate. The method included two steps: introduction of grafting sites and grafting of polymer brushes. The details are as follows: After the copper alloy sheet was plasma treated for 10 minutes, it was immersed in a 1% by mass KH570 ethanol aqueous solution (90% by volume of ethanol) for reaction for 15 minutes; the reacted copper alloy sample was washed with deionized water and ethanol, and then a polymer brush layer was prepared using the same steps as in Example S3. The thickness of the obtained polymer brush layer was the same as that in Example 1, and it is referred to as "polymer brush" in the following performance tests.

[0051] Performance Testing The drag reduction effect test method includes: using a high-precision rheometer to test the drag reduction effect, respectively attaching the samples of Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4 to the bottom surface of the container facing the rheometer turntable, and controlling the distance between the sample surface and the rheometer turntable to be 2mm; then increasing the speed of the turntable from 0 to 1500 rpm and maintaining the speed of 1500 rpm for 60 seconds, and after the torque value reaches stability, testing the torque applied to the turntable during this process. By comparing the samples with different layer structures with the blank substrate of Comparative Example 1, the drag reduction effect of the different layer structures is obtained, and the results are as follows: Figure 2 As shown, the bionic composite layer structure developed in the present invention has the smallest torque compared with the single flexible layer, microstructure layer and polymer brush layer, proving that the bionic composite layer structure can achieve better drag reduction effect through the synergistic effect of multiple drag reduction mechanisms.

[0052] Noise reduction effect test, the method includes: using Figure 3 The experimental bench shown in the figure tests the noise reduction effect of different surfaces. Cast iron is used as the base material. Pipe replacement sections are prepared according to the methods of Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4, and the prepared pipe replacement sections are placed on the Figure 3 The position shown in Figure 3 The two replacement sections used the same pipe material, and four hydrophones were installed at the locations shown in the figure. The entire test pipe was pressurized to 2 MPa to eliminate the influence of cavitation noise. The circulation pump was turned on to increase the flow rate of the water in the pipe to 3 m / s. After the flow field stabilized, the hydrophone data was collected and processed. The noise reduction performance of different samples was evaluated by comparing them with a blank cast iron substrate. The results are shown in Figure 2. Figure 4 As shown, the bionic composite layer structure developed in the present invention has the lowest sound pressure level compared with the single flexible layer, microstructure layer and polymer brush layer, proving that the bionic composite layer structure can achieve better noise reduction effect through the synergistic effect of multiple noise reduction mechanisms.

[0053] Antifouling performance test, the method includes: using the anti-diatom adhesion test to test the antifouling performance, the concentration of the preparation is 1.5×10 6 cells / mL of diatom suspension, using the products in Example 1 and Comparative Example 1 as the test samples, the test samples were completely immersed in the suspension, placed at a constant temperature of 20°C, and continuously shaken on a shaker at a speed of 100 rpm for 7 days; the samples were then thoroughly rinsed with deionized water to remove algal cells attached to the surface; the samples were then placed in a 2.5% glutaraldehyde solution and fixed at 4°C for 4 hours. The fixed samples were dehydrated in different concentrations of ethanol aqueous solution (70%, 80%, 90% and 100% v / v) in sequence, with each step processing time being 30 minutes; after dehydration, the samples were air-dried, and the sample surface was observed and analyzed using a scanning electron microscope. The results are shown as follows Figure 5 As shown in the figure, compared with the blank substrate, the amount of diatom adhesion on the substrate surface with the bionic composite layer is significantly reduced. The surface bionic composite layer has a good anti-fouling effect, can ensure the integrity of the microstructure, and improve the durability of the bionic composite drag and noise reduction layer structure.

[0054] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A bionic composite drag and noise reduction layer structure, characterized in that: The flexible layer comprises a flexible layer and a polymer brush layer, wherein the flexible layer is used to bond with a substrate, an array of micron-scale microstructures is provided on the surface of the flexible layer, and a polymer brush layer is connected to the surface of the flexible layer, and the polymer brush layer can form a hydration layer with water molecules; The flexible layer material includes one or more of polyurethane, polyurea and polydimethylsiloxane; the flexible layer contains a photoinitiator; and the polymer brush layer includes one or more of zwitterionic polymer and neutral polymer.

2. The bionic composite drag and noise reduction layer structure according to claim 1, characterized in that: The elastic modulus of the flexible layer is 1.0-1.5 MPa, and the thickness of the flexible layer is 0.5-3 mm; Alternatively, the thickness of the polymer brush layer is 10-500 nm.

3. The bionic composite drag and noise reduction layer structure according to claim 1, characterized in that: The photoinitiator includes one or more of benzophenone and 2-hydroxy-2-methyl-1-phenyl-1-propanone.

4. The bionic composite drag and noise reduction layer structure according to claim 1, characterized in that: The zwitterionic polymer includes a polymer formed from one or more of phosphorylcholine, carboxylic acid betaine, and sulfobetaine; and the neutral polymer includes a polymer formed from one or more of polyacrylamide and polyethylene glycol.

5. The bionic composite drag and noise reduction layer structure according to claim 4, characterized in that: The zwitterionic polymer is a polymer of methacryloylethyl sulfobetaine.

6. A method for preparing the bionic composite drag and noise reduction layer structure according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1, processing a micro-texture array on the surface of a hard template, forming a flexible layer raw material on the hard template and then demolding it to obtain a flexible layer; S2, soaking the flexible layer in a solution containing a photoinitiator for a set time to obtain a flexible layer containing a photoinitiator; S3. Immersing the flexible layer containing a photoinitiator into a polymer monomer solution of a set concentration to initiate a photopolymerization reaction to prepare a polymer brush layer, thereby obtaining a biomimetic composite drag and noise reduction layer structure.

7. The method for preparing the bionic composite drag and noise reduction layer structure according to claim 6, characterized in that: In S1, the surface of the hard template is hydrophobically treated to facilitate demoulding of the flexible layer; Alternatively, in S1, the forming process includes: after vacuum removal of bubbles, maintaining the temperature at 80-100°C for 1-1.5 hours to obtain a dense and uniformly thick flexible layer.

8. The method for preparing the bionic composite drag and noise reduction layer structure according to claim 6, characterized in that: In S2, the concentration of the solution containing the photoinitiator is 3-8 wt %, the solvent is selected from one or more of n-hexane and dichloromethane, and the immersion time is 2-4 h.

9. The method for preparing the bionic composite drag and noise reduction layer structure according to claim 6, characterized in that: In S3, a catalyst is added to the polymer monomer solution, wherein the catalyst includes one or more of cerium ammonium nitrate, ammonium persulfate and hydrogen peroxide, for catalyzing the polymerization reaction; Alternatively, in S3, the method of initiating the photopolymerization reaction comprises: irradiating with ultraviolet light for 6 to 9 hours.

10. An application of the bionic composite drag and noise reduction layer structure according to any one of claims 1 to 5, characterized in that: include: Used for underwater surface of hull, propeller surface or inner wall of seawater circulation cooling pipe.

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