Method for directly writing multiple patterns on resin surface through laser for frequency selection of surface

Abstract

The invention discloses a method for directly writing multiple patterns on a resin surface through laser for a frequency selection surface, and belongs to the technical field of electromagnetic shielding. The method comprises the following steps: designing a carbonization pattern and spacing of laser, simulating the wave absorbing performance of an array, and forming the array; selecting a resin base material and performing pretreatment; laser direct writing is carried out on the surface of the pretreated resin base material, and the surface appearance and structure of the resin base material are analyzed; laser parameters are changed, the resistance of a carbonized area is recorded and measured in real time, a mechanical property test, an electromagnetic property test, a dielectric constant test and a magnetic conductivity test are carried out on the carbonized resin base material, and a loss tangent value and reflection loss are calculated. And an energy density-carbonization morphology-multifunctional performance correlation model is established. A solution is provided for the field of electromagnetic shielding and stealth, the weight reduction requirements of aerospace equipment such as unmanned aerial vehicles and satellites can be met, the material can be applied to electromagnetic compatibility design of 5G communication equipment, the mechanical stability is high, and the material can be applied to engineering in an extreme environment.

Description

Technical Field

[0001] The invention belongs to the technical field of electromagnetic shielding, and in particular relates to a method for directly writing multiple patterns on a resin surface by laser for frequency selection of the surface. Background Art

[0002] With the rapid development of 5G communications, the Internet of Things (IoT), and wireless technologies, the sources of electromagnetic radiation in the environment have increased dramatically, including base stations, mobile devices, radar systems, and household appliances. Long-term exposure to high-intensity electromagnetic fields can negatively impact human health (such as the nervous and immune systems) and the ecological environment (such as bird migration and plant growth). Furthermore, electromagnetic interference (EMI) can degrade the performance of electronic devices, leading to signal distortion, data loss, and even system failures, particularly in highly sensitive areas such as aerospace, medical equipment, and precision instruments. Aircraft face the dual challenges of stealth and interference resistance in complex electromagnetic environments. High-performance electromagnetic shielding materials are crucial to ensuring their safety and reliability. Metamaterials are a revolutionary breakthrough in 21st-century materials science. Through artificially designed microstructures (such as periodic arrays and porous networks), they achieve the ability to manipulate electromagnetic waves, efficiently absorbing or reflecting electromagnetic radiation in specific frequency bands, thereby reducing electromagnetic pollution in the environment.

[0003] Currently, electromagnetic shielding technology or absorbing materials are commonly used to reduce or eliminate electromagnetic pollution. Absorbing materials absorb electromagnetic waves and convert them into heat energy, dissipating it and thereby reducing or weakening electromagnetic radiation and electromagnetic interference. They are the most effective method for eliminating electromagnetic pollution and have become a hot topic in current research and application. Currently, there are numerous categorizations of absorbing materials. Based on the material forming process and load-bearing capacity, absorbing materials can be divided into coated absorbing materials and structural absorbing materials. Traditional coated radar absorbing materials still face a series of challenges in practical engineering applications. For example, existing absorbing coatings have a narrow absorption band, are heavy and thick during use, limiting their use in aircraft and certain specialized components. In actual use, they also suffer from poor thermal stability, failing to meet all-weather combat requirements. Furthermore, traditional absorbing coatings are prone to shedding after prolonged use. Traditional absorbing coatings lack load-bearing capacity and have limited functionality, failing to meet the design requirements of both radar absorbing performance and aesthetics. Therefore, the research and application of structural radar absorbing materials will become a key direction for future absorbing material research and development. In the research of structural radar absorbing materials, frequency selective surfaces (FSSs), two-dimensional periodic electromagnetic structures that achieve spatial filtering of electromagnetic waves through unit resonance, have become a key technology for solving this problem. However, the practical application of FSSs still faces multiple bottlenecks, such as complex surface processing difficulties, insufficient broadband compatibility, and limited environmental stability. In contrast, structural absorbing materials, which integrate absorbing functions with load-bearing structures, are becoming a future development direction.

[0004] In recent years, laser selective carbonization (LSC) has provided an innovative solution for the efficient fabrication of FSS. This technique utilizes a high-energy laser to induce localized pyrolysis on the polymer surface, directly generating a conductive carbon structure. This technique offers nanoscale processing precision, meeting the requirements of multi-band resonant designs. Through dynamic focusing and path planning, this non-contact, flexible process can accommodate complex surfaces with a curvature radius of less than 50 mm. Given the limitations of traditional absorbing coatings and the difficulty of FSS fabrication, a new FSS fabrication technique is needed to integrate the absorbing function with the load-bearing structure, enabling the manipulation of electromagnetic waves through artificially designed microstructures. Summary of the Invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a method for laser direct writing of multiple patterns on a resin surface for frequency-selective surface, so as to solve the technical problem of how to achieve the integration of absorbing structure functions and artificially control electromagnetic waves to reduce the interface loss and process complexity caused by FSS chip resistors.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention discloses a method for directly writing multiple patterns on a resin surface by laser for frequency selection, comprising: Design the laser carbonization pattern and spacing, simulate the array's absorption properties, and form the array; select the resin substrate and perform pretreatment; Laser direct writing is performed on the surface of the pretreated resin substrate, and the surface morphology and structure of the resin substrate are analyzed; By changing the laser parameters and recording in real time, the resistance of the carbonized area is measured, and the mechanical properties, electromagnetic properties, dielectric constant and magnetic permeability of the carbonized resin substrate are tested, and the loss tangent and reflection loss are calculated.

[0007] Preferably, the carbonization pattern includes: circle, square, hexagon, cross or hollow cross.

[0008] Preferably, the size of the carbonized pattern is 5-15 mm; the spacing between the carbonized patterns is 5-20 mm.

[0009] Preferably, the resin substrate comprises epoxy resin / glass fiber composite material, polyimide film or aramid fiber cloth; the thickness of the resin substrate is 0.5-3 mm; and the carbon content of the resin substrate is 50%-80%.

[0010] Preferably, the pretreatment comprises: ultrasonically cleaning the resin substrate with acetone and ethanol in sequence for 10-30 min, drying with nitrogen, and then drying at 60-80° C. for 25-35 min.

[0011] Preferably, during laser direct writing, the laser parameters include: pulse width of 50-350 ns, frequency of 20-300 kHz, power of 1-30 W, and speed of 50-1000 mm / s.

[0012] Preferably, the surface morphology and structure of the resin substrate are analyzed by transmission electron microscopy, scanning electron microscopy, optical microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, high-resolution transmission electron microscopy, and X-ray diffraction.

[0013] Preferably, the mechanical property test includes: making a tensile test piece, changing the side length of the carbonization pattern to 5-15 mm, and changing the spacing of the carbonization pattern to 15-25 mm.

[0014] Preferably, the electromagnetic performance test includes: making an electromagnetic test piece, changing the size of the resin substrate to 10-50 cm, changing the side length of the carbonized pattern to 5-15 mm, and changing the spacing of the carbonized pattern to 15-25 mm.

[0015] Preferably, the laser carbonization pattern is designed using AutoCAD; a digital instrument is used to record and measure the resistance of the carbonized area in real time; a vector network analyzer is used to test the dielectric constant and magnetic permeability of the resin substrate, and the loss tangent value and reflection loss are calculated.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention proposes a method for laser direct writing multiple patterns onto resin surfaces for frequency-selective surfaces. This method utilizes laser direct writing technology to fabricate multidimensional frequency-selective surfaces. By combining the laser direct writing process with carbon-based metamaterial design, the method achieves efficient fabrication and performance optimization of functionalized metamaterials. Traditional carbon-based material preparation processes (such as chemical vapor deposition and template methods) suffer from complex preparation processes, low structural control precision, and limited functionality. This invention utilizes laser direct writing technology to precisely control carbon structural morphology at the micro- and nanoscale. By optimizing key parameters such as laser energy density, scanning speed, and pulse frequency, the degree of graphitization, pore distribution, and surface roughness of the carbon material can be precisely controlled. This allows the construction of three-dimensional carbon structures with gradient functional properties at the atomic scale, significantly improving the material's electromagnetic absorption efficiency and mechanical stability. A multiscale correlation model of "energy density-carbonization morphology-multifunctional performance" was established, revealing a quantitative relationship between laser parameters and the material's microstructure. The deep integration of laser direct writing technology and metamaterial design not only solves the performance limitations of traditional processes but also provides solutions for electromagnetic shielding and stealth. Its lightweight properties can meet the weight reduction needs of aerospace equipment such as drones and satellites. Its broadband wave absorption performance can be applied to the electromagnetic compatibility design of 5G communication equipment, while its excellent mechanical stability expands its engineering application potential in extreme environments. Furthermore, this method can be extended to emerging fields such as flexible electronics and intelligent sensing, showing broad prospects for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the method for laser direct writing multiple patterns on a resin surface for frequency selection disclosed in Example 1 of the present invention; Figure 2 The scanning transmission microscopy images, Raman patterns, and X-ray diffraction patterns of the laser direct writing carbonized sample disclosed in Example 2 of the present invention are shown; (a) is an XRD pattern; (b) is a Raman pattern; (c) is a 100 μm SEM pattern; and (d) is a 20 μm SEM pattern. Figure 3The X-ray photoelectron spectroscopy, scanning transmission microscopy, transmission electron microscopy, and high-resolution transmission electron microscopy images of the cross-section of the sample after laser direct writing carbonization disclosed in Example 3 of the present invention are shown; wherein (a) is an XPS spectrum; (b) is a 200 μm SEM; (c) is a 50 nm TEM; and (d) is a high-resolution transmission electron microscopy image; Figure 4 These are scanning electron microscope images of the mechanical properties test of the sample after laser direct writing carbonization disclosed in Example 5 of the present invention; among them, (a) is the SEM image after surface ablation; (b) is the SEM image of the surface without ablation; (c) is the SEM image of the cross section after ablation; and (d) is the SEM image of the cross section without ablation. DETAILED DESCRIPTION

[0018] The technical solution of the present invention will be described clearly and completely below. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0019] In the present invention, unless otherwise specified, all the embodiments and preferred implementation methods mentioned herein can be combined with each other to form a new technical solution.

[0020] In the present invention, unless otherwise specified, all technical features and preferred features mentioned herein can be combined with each other to form a new technical solution.

[0021] In the present invention, unless otherwise specified, percentages (%) or parts refer to percentages by weight or parts by weight relative to the composition.

[0022] In the present invention, unless otherwise specified, the components involved or their preferred components can be combined with each other to form a new technical solution.

[0023] In this disclosure, unless otherwise specified, the numerical range "a-b" is an abbreviation for any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "6-22" indicates that all real numbers between "6-22" are listed herein, and "6-22" is merely an abbreviation for these numerical combinations.

[0024] The "range" disclosed in the present invention is in the form of lower limit and upper limit, which can be one or more lower limits, and one or more upper limits respectively.

[0025] In the present invention, the term "and / or" used herein refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0026] In the present invention, unless otherwise specified, each reaction or operation step can be carried out sequentially or in accordance with the order. Preferably, the reaction method herein is carried out sequentially.

[0027] Unless otherwise indicated, the professional and scientific terms used herein are the same as those familiar to those skilled in the art. In addition, any method or material similar or equivalent to the described content can also be applied to the present invention.

[0028] The present invention provides a method for directly writing multiple patterns on a resin surface by laser for frequency selection of the surface, and the method is implemented by the following steps: Step 1: Pattern design and substrate selection.

[0029] First, the laser carbonization pattern was designed using AutoCAD. The spacing and arrangement between the patterns were also designed to simulate the array's absorption properties. The array was then formed. Epoxy resin / glass fiber composite, polyimide film, and aramid fiber of varying thicknesses and materials were used as substrates. The substrates were ultrasonically cleaned with acetone and ethanol, followed by nitrogen drying and placement in a drying oven to remove any residual moisture.

[0030] In step 1, use AutoCAD to design the laser carbonization pattern. The patterns mainly include: circle, square, hexagon, cross, and hollow cross. Design the spacing and arrangement between the laser carbonization patterns. The size of the pattern is 5-15 mm, and the spacing between the patterns is 5-20 mm. Select different materials as substrates, namely epoxy resin / glass fiber composite material, polyimide film, and aramid fiber cloth. Change the thickness and carbon content of the substrate, among which the different thicknesses are 0.5-3mm and the different carbon contents are 50%-80%. Clean the surface of the substrate, ultrasonically clean it with acetone and ethanol for 10-30 minutes, blow dry it with nitrogen, and place it in a drying oven at 60-80℃ for 25-35 minutes to remove residual moisture.

[0031] Step 2: Laser direct writing and carbonization morphology and structure analysis.

[0032] Laser direct writing is performed on the substrate surface, and laser parameters such as pulse width, frequency, power, and speed are varied. The carbonized morphology and structure are characterized and analyzed, and the relationship between energy density and carbonized morphology is established.

[0033] In step 2, laser direct writing is performed on the substrate surface. Laser parameters, including pulse width of 50-350 ns, frequency of 20-300 kHz, power of 1-30 W, and speed of 50-1000 mm / s, are recorded in real time by a digital instrument to measure the resistance of the carbonized area. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), optical microscopy (OM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD) are used to characterize the carbonized morphology and structure.

[0034] Step 3: Mechanical and electromagnetic performance testing.

[0035] Silver paint was applied to both ends of the laser-written sample to serve as electrodes. Laser parameters were varied to measure the resistance of the carbonized region. Electromagnetic properties of the sample were tested using a vector network analyzer to determine the dielectric constant and permeability, and to calculate the loss tangent and reflection loss. Mechanical properties of the sample were tested using a universal materials testing machine for tensile testing.

[0036] For the performance tests in step 3, the mechanical tensile test was conducted by fabricating tensile test specimens with the carbonized pattern length varied between 5-15 mm and the spacing between the carbonized patterns varied between 15-25 mm. For the electromagnetic test, the electromagnetic test specimens were fabricated with the substrate size varied between 10-50 cm, the carbonized pattern length varied between 5-15 mm and the spacing varied between 15-25 mm.

[0037] The application of laser selective carbonization technology to FSS using the above scheme has the following advantages: (1) Nano-scale processing accuracy, which can produce complex patterns with feature sizes as low as 50 nm (such as windmill-shaped structures, fractal structures), meeting the requirements of multi-band resonance design. (2) Non-contact flexible processing, through dynamic focusing and path planning, it can adapt to complex surfaces with a curvature radius of <50 mm, avoiding substrate damage caused by mechanical stress. (3) Multifunctional integration potential, the carbonized layer has both high conductivity and porous topology, which can simultaneously optimize conductive loss and interface polarization loss. (4) Lightweight and flexibility, using laser direct writing technology to directly generate FSS patterns on the material without the need for additional metal layers or other heavy materials. This approach not only reduces the overall weight, but also increases design flexibility, which is particularly suitable for weight-sensitive applications such as aerospace. (5) Strong customization capabilities, due to its non-contact processing method, laser selective carbonization can quickly respond to different design requirements and support highly customized FSS design. Whether it is changing the operating frequency range or optimizing performance in a specific environment, it can be flexibly responded to. (6) Broadband absorption performance. The FSS prepared by laser selective carbonization technology can effectively absorb electromagnetic waves in a wide frequency range, which is particularly important for improving the electromagnetic compatibility between electronic devices and the development of stealth technology.

[0038] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0039] Example 1 A method for laser direct writing multiple patterns on a resin surface for frequency-selective surface application comprises the following steps: (1) Pattern design and substrate selection The laser carbonization pattern was designed using AutoCAD. The pattern was circular, 5 mm in size, and 5 mm in spacing. An epoxy resin / glass fiber composite was selected as the substrate. The substrate thickness was changed to 0.5 mm and the carbon content was 50%. The substrate surface was cleaned, ultrasonically cleaned with acetone and ethanol for 10 minutes, dried with nitrogen, and then placed in a drying oven at 60°C for 25 minutes to remove any residual moisture.

[0040] (2) Laser direct writing and carbonization morphology and structure analysis Laser direct writing was performed on the substrate surface using laser parameters of 50 ns pulse width, 20 kHz frequency, 1 W power, and 50 mm / s speed. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), optical microscopy (OM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD) were used to characterize the carbonized morphology and structure.

[0041] (3) Mechanical and electromagnetic performance tests For the mechanical tensile properties test, tensile test pieces were prepared with a carbonized pattern of 5 mm on each side and 15 mm on each side. For the electromagnetic properties test, electromagnetic test pieces were prepared with a substrate size of 10 cm and a carbonized pattern of 5 mm on each side and 15 mm on each side.

[0042] See also Figure 1 This is a schematic diagram of the method for laser direct writing of multiple patterns on a resin surface for frequency-selective surface disclosed in Example 1 of the present invention; as can be seen from the figure, there are schematic diagrams of pattern design and mechanical and electromagnetic performance testing. Among them, the pattern array is designed with AutoCAD to form a laser carbonized pattern, and the spacing and arrangement between the patterns are designed at the same time to simulate the absorption performance of the array to form an array. A substrate with both laser absorption efficiency and good mechanical properties is selected, and local carbonization is induced on the resin surface under laser irradiation to form a conductive carbon nanostructure. The carbonized sample plate is subjected to an electromagnetic performance test as shown in the lower left figure and a mechanical performance test as shown in the lower right figure to measure whether its electromagnetic wave absorption performance is significantly improved after carbonization and whether its mechanical performance is significantly decreased after carbonization.

[0043] Example 2 A method for laser direct writing multiple patterns on a resin surface for frequency-selective surface application comprises the following steps: (1) Pattern design and substrate selection The laser carbonization pattern was designed using AutoCAD. The pattern was square, 10 mm in size, and 10 mm between patterns. An epoxy resin / glass fiber composite was selected as the substrate. The substrate thickness was changed to 1 mm and the carbon content was 60%. The substrate surface was cleaned, ultrasonically cleaned with acetone and ethanol for 20 minutes, dried with nitrogen, and then placed in a drying oven at 70°C for 30 minutes to remove any residual moisture.

[0044] (2) Laser direct writing and carbonization morphology and structure analysis Laser direct writing was performed on the substrate surface using the following laser parameters: a pulse width of 100 ns, a frequency of 50 kHz, a power of 10 W, and a speed of 100 mm / s. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), optical microscopy (OM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD) were used to characterize the carbonized morphology and structure.

[0045] (3) Mechanical and electromagnetic performance tests For the mechanical tensile properties test, tensile test pieces were prepared with a carbonized pattern of 10 mm on each side and 20 mm spacing between the carbonized patterns. For the electromagnetic properties test, electromagnetic test pieces were prepared with a substrate size of 20 cm and a carbonized pattern of 10 mm on each side and 20 mm spacing between the carbonized patterns.

[0046] See also Figure 2 The scanning transmission microscope image, Raman spectrum and X-ray diffraction spectrum of the sample after laser direct writing carbonization disclosed in Example 2 of the present invention; among them, (a) is the XRD spectrum; (b) is the Raman spectrum; (c) is the SEM image of 100 μm; (d) is the SEM image of 20 μm; it can be seen from (a) that XRD shows a strong (002) diffraction peak, but the half-maximum width is large, indicating that the crystallinity after carbonization is low and the conductivity is weak; it can be seen from (b) that ID / IG=0.7, the degree of graphitization is high, but the carbonization is discontinuous and incomplete; it can be seen from (c) and (d) that the carbon particles of the epoxy resin glass fiber board are loosely attached to the glass fiber surface, and SEM shows that amorphous carbon and a small amount of graphite crystals coexist.

[0047] Example 3 A method for laser direct writing multiple patterns on a resin surface for frequency-selective surface application comprises the following steps: (1) Pattern design and substrate selection The laser carbonization pattern was designed using AutoCAD. The pattern was hexagonal, with a size of 15 mm and a spacing of 20 mm between patterns. An epoxy resin / glass fiber composite was selected as the substrate. The substrate thickness was changed to 1.5 mm and the carbon content was 60%. The substrate surface was cleaned, ultrasonically cleaned with acetone and ethanol for 30 minutes, dried with nitrogen, and then placed in a drying oven at 80°C for 35 minutes to remove any residual moisture.

[0048] (2) Laser direct writing and carbonization morphology and structure analysis Laser direct writing was performed on the substrate surface using laser parameters of 150 ns pulse width, 100 kHz frequency, 15 W power, and 200 mm / s speed. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), optical microscopy (OM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD) were used to characterize the carbonized morphology and structure.

[0049] (3) Mechanical and electromagnetic performance tests For the mechanical tensile properties test, tensile test pieces were prepared with a carbonized pattern of 15 mm on each side and 25 mm spacing. For the electromagnetic properties test, electromagnetic test pieces were prepared with a substrate size of 20 cm and a carbonized pattern of 15 mm on each side and 25 mm spacing.

[0050] See also Figure 3 The following are X-ray photoelectron spectroscopy, scanning transmission microscopy, transmission electron microscopy, and high-resolution transmission electron microscopy images of a cross-section of a sample after laser direct writing carbonization, as disclosed in Example 3 of the present invention. (a) is the XPS spectrum; (b) is the 200 μm SEM; (c) is the 50 nm TEM; and (d) is the high-resolution transmission electron microscopy image. As can be seen from (a), the C1s spectrum of the sample, after fitting calculation, shows a CC content of 86.9%, a CO content of 9.4%, and a C=O content of 3.7%. The surface is primarily composed of non-polar carbon (CC). The high proportion (86.9%) indicates that the carbon structure on the material surface is intact and highly graphitized. Oxygen-containing functional groups (CO + C=O) account for only 13.1%, indicating a low degree of surface oxidation. This may be due to the sample being exposed to air during processing, resulting in slight surface oxidation and the generation of a small amount of oxygen-containing groups. (b) shows that carbon particles are generated by the pyrolysis of the epoxy resin and adhere to the glass fiber surface. The accumulation of carbon particles leads to partial degradation of the resin matrix between the glass fibers, widening the interfiber spacing and reducing interlaminar bond strength. As can be seen in (c) and (d), the carbon particles are composed of disordered amorphous carbon (predominantly sp³ hybridized) and localized graphite crystallites (sp² hybridized). High-resolution analysis of the carbonized region revealed a lattice fringe spacing of 0.34 nm, corresponding to the (002) crystal plane of graphite.

[0051] Example 4 A method for laser direct writing multiple patterns on a resin surface for frequency-selective surface application comprises the following steps: (1) Pattern design and substrate selection The laser carbonization pattern was designed using AutoCAD. The pattern was a cross, with a size of 5 mm and a spacing of 5 mm between patterns. An epoxy resin / glass fiber composite was selected as the substrate. The substrate thickness was changed to 2 mm and the carbon content was 80%. The substrate surface was cleaned, ultrasonically cleaned with acetone and ethanol for 10 minutes, dried with nitrogen, and then placed in a drying oven at 60°C for 25 minutes to remove any residual moisture.

[0052] (2) Laser direct writing and carbonization morphology and structure analysis The substrate surface was processed using a laser direct writing method. The laser parameters during direct writing were a pulse width of 200 ns, a frequency of 150 kHz, a power of 20 W, and a speed of 300 mm / s. The carbonized morphology and structure were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), optical microscopy (OM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD).

[0053] (3) Mechanical and electromagnetic performance tests For the mechanical tensile properties test, tensile test pieces were prepared with a carbonized pattern of 5 mm on each side and 15 mm on each side. For the electromagnetic properties test, electromagnetic test pieces were prepared with a substrate size of 30 cm and a carbonized pattern of 5 mm on each side and 15 mm on each side.

[0054] Example 5 A method for laser direct writing multiple patterns on a resin surface for frequency-selective surface application comprises the following steps: (1) Pattern design and substrate selection The laser carbonization pattern was designed using AutoCAD. It was a hollow cross with a 10 mm pattern size and 10 mm spacing between patterns. An epoxy resin / glass fiber composite was selected as the substrate. The substrate thickness was changed to 2.5 mm and the carbon content was 80%. The substrate surface was cleaned, ultrasonically cleaned with acetone and ethanol for 20 minutes, dried with nitrogen, and then placed in a drying oven at 70°C for 30 minutes to remove any residual moisture.

[0055] (2) Laser direct writing and carbonization morphology and structure analysis Laser direct writing was performed on the substrate surface using the following laser parameters: a pulse width of 250 ns, a frequency of 200 kHz, a power of 25 W, and a speed of 400 mm / s. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), optical microscopy (OM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD) were used to characterize the carbonized morphology and structure.

[0056] (3) Mechanical and electromagnetic performance tests For the mechanical tensile properties test, tensile test pieces were prepared with a carbonized pattern of 10 mm side length and 15 mm spacing. For the electromagnetic properties test, electromagnetic test pieces were prepared with a substrate size of 40 cm, a carbonized pattern of 10 mm side length and 20 mm spacing.

[0057] See also Figure 4 Scanning electron microscope images of the mechanical properties test of the sample after laser direct writing carbonization disclosed in Example 5 of the present invention; wherein, (a) is the SEM image after surface ablation; (b) is the SEM image of the surface without ablation; (c) is the SEM image of the cross section after ablation; (d) is the SEM image of the cross section without ablation; as can be seen from (a) and (b), the glass fibers in the ablated area are more loosely arranged compared to the unablated area, while the glass fibers in the unablated area are more tightly arranged. As can be seen from (c) and (d), similarly, the cross section can be more clearly seen that the fracture surface is relatively flat, and the glass fibers in the ablated area are more loosely arranged compared to the unablated area, while the glass fibers in the unablated area are more tightly arranged.

[0058] Example 6 A method for laser direct writing multiple patterns on a resin surface for frequency-selective surface application comprises the following steps: (1) Pattern design and substrate selection The laser carbonization pattern was designed using AutoCAD. The pattern was circular, 15 mm in size, and 20 mm between patterns. A polyimide film was selected as the substrate. The thickness was changed to 3 mm, and the carbon content was 50%. The substrate surface was cleaned, ultrasonically cleaned with acetone and ethanol for 30 minutes, dried with nitrogen, and then placed in a drying oven at 80°C for 35 minutes to remove any residual moisture.

[0059] (2) Laser direct writing and carbonization morphology and structure analysis The substrate surface was processed using a laser direct writing method. The laser parameters during direct writing were a pulse width of 300 ns, a frequency of 250 kHz, a power of 30 W, and a speed of 500 mm / s. The carbonized morphology and structure were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), optical microscopy (OM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD).

[0060] (3) Mechanical and electromagnetic performance tests For the mechanical tensile properties test, tensile test pieces were prepared with a carbonized pattern of 15 mm on each side and 25 mm on each side. For the electromagnetic properties test, electromagnetic test pieces were prepared with a substrate size of 50 cm and a carbonized pattern of 15 mm on each side and 25 mm on each side.

[0061] Example 7 A method for laser direct writing multiple patterns on a resin surface for frequency-selective surface application comprises the following steps: (1) Pattern design and substrate selection The laser carbonization pattern was designed using AutoCAD. The pattern was square, 5 mm in size, and 5 mm between patterns. A polyimide film was selected as the substrate. The thickness was changed to 0.5 mm, and the carbon content was 60%. The substrate surface was cleaned, ultrasonically cleaned with acetone and ethanol for 10 minutes, dried with nitrogen, and then placed in a drying oven at 60°C for 25 minutes to remove any residual moisture.

[0062] (2) Laser direct writing and carbonization morphology and structure analysis Laser direct writing was performed on the substrate surface using the following laser parameters: a pulse width of 350 ns, a frequency of 300 kHz, a power of 1 W, and a speed of 600 mm / s. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), optical microscopy (OM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD) were used to characterize the carbonized morphology and structure.

[0063] (3) Mechanical and electromagnetic performance tests For the mechanical tensile properties test, tensile test pieces were prepared with a carbonized pattern of 5 mm on each side and 15 mm on each side. For the electromagnetic properties test, electromagnetic test pieces were prepared with a substrate size of 10 cm and a carbonized pattern of 5 mm on each side and 15 mm on each side.

[0064] Example 8 A method for laser direct writing multiple patterns on a resin surface for frequency-selective surface application comprises the following steps: (1) Pattern design and substrate selection The laser carbonization pattern was designed using AutoCAD. The pattern was square, 10 mm in size, and 15 mm between patterns. Aramid fiber cloth was selected as the substrate. The thickness was changed to 1 mm, and the carbon content was 65%. The substrate surface was cleaned, ultrasonically cleaned with acetone and ethanol for 20 minutes, dried with nitrogen, and then placed in a drying oven at 70°C for 30 minutes to remove any residual moisture.

[0065] (2) Laser direct writing and carbonization morphology and structure analysis The substrate surface was processed using a laser direct writing method. The laser parameters during direct writing were a pulse width of 50 ns, a frequency of 20 kHz, a power of 10 W, and a speed of 700 mm / s. The carbonized morphology and structure were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), optical microscopy (OM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD).

[0066] (3) Mechanical and electromagnetic performance tests For the mechanical tensile properties test, tensile test pieces were prepared with a carbonized pattern of 10 mm on each side and 20 mm spacing between the carbonized patterns. For the electromagnetic properties test, electromagnetic test pieces were prepared with a substrate size of 30 cm and a carbonized pattern of 10 mm on each side and 20 mm spacing between the carbonized patterns.

[0067] Example 9 A method for laser direct writing multiple patterns on a resin surface for frequency-selective surface application comprises the following steps: (1) Pattern design and substrate selection The laser carbonization pattern was designed using AutoCAD. The pattern was square, 15 mm in size, and 20 mm between patterns. Aramid fiber cloth was selected as the substrate. The thickness was changed to 3 mm and the carbon content was 80%. The substrate surface was cleaned, ultrasonically cleaned with acetone and ethanol for 30 minutes, dried with nitrogen, and then placed in a drying oven at 80°C for 35 minutes to remove any residual moisture.

[0068] (2) Laser direct writing and carbonization morphology and structure analysis Laser direct writing was performed on the substrate surface using the following laser parameters: a pulse width of 350 ns, a frequency of 300 kHz, a power of 30 W, and a speed of 1000 mm / s. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), optical microscopy (OM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD) were used to characterize the carbonized morphology and structure.

[0069] (3) Mechanical and electromagnetic performance tests For the mechanical tensile properties test, tensile test pieces were prepared with a carbonized pattern of 15 mm on each side and 25 mm on each side. For the electromagnetic properties test, electromagnetic test pieces were prepared with a substrate size of 50 cm and a carbonized pattern of 15 mm on each side and 25 mm on each side.

[0070] Example 10 A method for laser direct writing multiple patterns on a resin surface for frequency-selective surface application comprises the following steps: (1) Pattern design and substrate selection The laser carbonization pattern was designed using AutoCAD. The pattern was square, 10 mm in size, and 5 mm between patterns. An epoxy resin / glass fiber composite was selected as the substrate. The substrate thickness was changed to 1 mm and the carbon content was 60%. The substrate surface was cleaned, ultrasonically cleaned with acetone and ethanol for 20 minutes, dried with nitrogen, and then placed in a drying oven at 65°C for 30 minutes to remove any residual moisture.

[0071] (2) Laser direct writing and carbonization morphology and structure analysis The substrate surface was processed using a laser direct writing method. The laser parameters during direct writing were a pulse width of 100 ns, a frequency of 20 kHz, a power of 10 W, and a speed of 500 mm / s. The carbonized morphology and structure were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), optical microscopy (OM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD).

[0072] (3) Mechanical and electromagnetic performance tests For the mechanical tensile properties test, tensile test pieces were prepared with a carbonized pattern of 10 mm on each side and 20 mm spacing between the carbonized patterns. For the electromagnetic properties test, electromagnetic test pieces were prepared with a substrate size of 30 cm and a carbonized pattern of 10 mm on each side and 20 mm spacing between the carbonized patterns.

[0073] The present invention discloses a method for directly writing multiple patterns on a resin surface by laser for frequency-selective surface, comprising: controllably constructing a carbon nanostructure on the surface of a resin substrate by laser direct writing, exploring the regulation mechanism of carbonization morphology, electrical, electromagnetic and mechanical properties by changing the speed, frequency, power and pulse width of the laser, and establishing an "energy density-carbonization morphology-multifunctional performance" correlation model. The present invention is used for electromagnetic shielding and provides a solution for the fields of electromagnetic shielding and stealth. Its lightweight characteristics can meet the weight reduction needs of aerospace equipment such as drones and satellites. Its broadband wave-absorbing performance can be applied to the electromagnetic compatibility design of 5G communication equipment. Its excellent mechanical stability expands its engineering application potential in extreme environments. In addition, this method can also be extended to emerging fields such as flexible electronic devices and intelligent sensors, and has broad prospects for industrial application.

[0074] In summary, this study aims to achieve the controllable fabrication of carbon nanostructures on resin surfaces through laser direct writing technology. The study systematically reveals how laser parameters regulate the material's multiscale structure and its electrical, electromagnetic, and mechanical properties. Under optimized parameters, the carbonized layer exhibits a composite structure of graphite crystallites (sp²) and amorphous carbon (sp³). Its low electrical resistance and electromagnetic losses stem from the synergistic effect of the conductive network and the porous polarization effect. The nonlinear relationship between laser parameters and θ is revealed. The proposed laser direct writing process combines high efficiency and low cost, making it suitable for applications such as 5G shielding and drone stealth skins.

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for laser direct writing multiple patterns on a resin surface for frequency selection, characterized in that: include: Design the laser carbonization pattern and spacing, simulate the array's absorption performance, and form the array; Select the resin substrate and pre-treat it; Laser direct writing is performed on the surface of the pretreated resin substrate, and the surface morphology and structure of the resin substrate are analyzed; By changing the laser parameters and recording in real time, the resistance of the carbonized area is measured, and the mechanical properties, electromagnetic properties, dielectric constant and magnetic permeability of the carbonized resin substrate are tested, and the loss tangent and reflection loss are calculated.

2. The method for laser direct writing multiple patterns on a resin surface for frequency selection according to claim 1, characterized in that: The carbonization pattern includes: circle, square, hexagon, cross or hollow cross.

3. The method for laser direct writing multiple patterns on a resin surface for frequency selection according to claim 1, characterized in that: The size of the carbonized pattern is 5-15 mm; the spacing between the carbonized patterns is 5-20 mm.

4. The method for laser direct writing multiple patterns on a resin surface for frequency selection according to claim 1, characterized in that: The resin substrate comprises an epoxy resin / glass fiber composite material, a polyimide film or an aramid fiber cloth; the thickness of the resin substrate is 0.5-3 mm; and the carbon content of the resin substrate is 50%-80%.

5. The method for laser direct writing multiple patterns on a resin surface for frequency selection according to claim 1, characterized in that: The pretreatment comprises: ultrasonically cleaning the resin substrate with acetone and ethanol in sequence for 10-30 minutes, drying with nitrogen, and then continuing to dry at 60-80° C. for 25-35 minutes.

6. The method for laser direct writing multiple patterns on a resin surface for frequency selection according to claim 1, characterized in that: During the laser direct writing, the laser parameters include: pulse width of 50-350 ns, frequency of 20-300 kHz, power of 1-30 W, and speed of 50-1000 mm / s.

7. The method for laser direct writing multiple patterns on a resin surface for frequency selection according to claim 1, characterized in that: The surface morphology and structure of the resin substrate were analyzed by transmission electron microscopy, scanning electron microscopy, optical microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, high-resolution transmission electron microscopy and X-ray diffraction.

8. The method for laser direct writing multiple patterns on a resin surface for frequency selection according to claim 1, characterized in that: The mechanical property test includes: making a tensile test piece, changing the side length of the carbonization pattern to 5-15 mm, and changing the spacing of the carbonization pattern to 15-25 mm.

9. The method for laser direct writing multiple patterns on a resin surface for frequency selection according to claim 1, characterized in that: The electromagnetic performance test includes: making an electromagnetic test piece, changing the size of the resin substrate to 10-50 cm, changing the side length of the carbonized pattern to 5-15 mm, and changing the spacing of the carbonized pattern to 15-25 mm.

10. The method for laser direct writing multiple patterns on a resin surface for frequency selection according to claim 1, characterized in that: The laser carbonization pattern was designed using AutoCAD; a digital instrument was used to record and measure the resistance of the carbonized area in real time; a vector network analyzer was used to test the dielectric constant and magnetic permeability of the resin substrate, and to calculate the loss tangent and reflection loss.

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