Metal and metal oxide micro-nano structure and femtosecond laser preparation method thereof

Abstract

This invention discloses a metal and metal oxide micro / nanostructure and its femtosecond laser fabrication method, relating to the field of micro / nanostructure manufacturing. The photosensitive resin comprises the following raw materials in parts by weight: 400-450 parts of a carboxyl-containing polymeric monomer, 100-150 parts of a crosslinking agent, 80-100 parts of a dispersant, and 6-8 parts of a photoinitiator; the monomer includes at least one of acrylic acid, cinnamic acid, and crotonic acid. The photosensitive resin possesses abundant carboxyl groups and efficient metal complexing ability. After femtosecond laser printing, it is immersed in a metal salt solution, allowing metal ions to be uniformly and densely anchored to the polymer molecular chains through coordination bonds. This reduces structural cracking and collapse during subsequent heat treatment. After heat treatment, a faithful conversion from polymer micro / nanostructures to high-purity metal or metal oxide micro / nanostructures is achieved, effectively solving the problem of interference from strong oxidizing metal ions on the laser polymerization reaction, as well as the existing structural collapse problem.

Description

Technical Field

[0001] This invention relates to the field of micro / nano structure fabrication, and more particularly to a metal and metal oxide micro / nano structure and its femtosecond laser fabrication method. Background Technology

[0002] Three-dimensional metal and metal oxide micro / nanostructures have shown enormous application potential in cutting-edge technology fields such as metamaterials, nanophotonics, micro / nanorobotics, and sensing and monitoring. Due to the excellent mechanical properties, magnetic characteristics, electrical conductivity, and photoelectric response of metals and their oxides, they can achieve complex functional integration across scales, thus attracting significant attention in the field of nanoengineering. Among numerous manufacturing methods, additive manufacturing technologies based on ultrafast lasers (such as femtosecond laser direct writing) have become the core means of constructing three-dimensional submicron and even nanoscale structures due to their extremely high spatial resolution and ability to transfer high energy in an extremely short time.

[0003] However, existing methods for fabricating three-dimensional metal and oxide micro / nanostructures still face irreconcilable contradictions regarding versatility, material loading, and structural precision. Current methods mainly fall into two categories: The first involves a two-step printing process using photosensitive resins containing metal ions. This involves first forming a metal-organic composite system through two-photon polymerization (TPL), followed by heat treatment. However, this method faces significant chemical challenges: on the one hand, high concentrations of metal ions often significantly reduce the optical transparency of the resin, limiting the laser processing depth; on the other hand, many highly oxidizing metal ions quench the active free radicals generated by the photoinitiator, thus inhibiting the polymerization reaction and preventing the acquisition of initial structures with adequate mechanical strength. Therefore, this type of method is usually limited to a very small number of specific metal elements and lacks broad applicability. The second category employs a post-processing strategy of "printing the scaffold first, then loading the metal." One common approach is to use a polymer scaffold to adsorb metal nanoparticles through capillary action. However, research has found that even after hundreds of adsorption cycles, most nanoparticles only adhere to the surface of the scaffold and struggle to penetrate the interior of the structure. This results in a final structure with extremely low metal density, making it difficult to maintain complex three-dimensional morphologies. Another improved approach is hydrogel infusion additive manufacturing (HIAM), which uses a hydrogel scaffold to adsorb metal ions. However, HIAM technology has significant drawbacks when applied to femtosecond laser two-photon printing: the extremely small pore size of the scaffold generated by two-photon polymerization severely restricts the free diffusion of metal ions, resulting in low loading efficiency. More importantly, the binding force between metal ions and traditional hydrogel matrices (such as systems based on PEGDA or PETA) is weak, mainly relying on coordination of ester oxygen atoms with low electron cloud density. This weak connection not only limits the upper limit of metal ion loading but also leads to cracks or severe structural collapse during subsequent high-temperature sintering due to uneven metal atom distribution and insufficient support strength.

[0004] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0005] Based on the shortcomings of the prior art, the purpose of this invention is to provide a metal and metal oxide micro / nano structure and its femtosecond laser fabrication method, aiming to solve the problem of metal ion interference with photopolymerization in the existing two-step printing method that directly uses photosensitive resin containing metal ions, as well as the problem of structural collapse in the existing method of printing a scaffold first and then loading metal.

[0006] The technical solution of the present invention is as follows: In a first aspect, the present invention provides a photosensitive resin, wherein the photosensitive resin comprises the following raw materials in parts by weight: 400-450 parts of carboxyl-containing polymeric monomers, 100-150 parts of crosslinking agent, 80-100 parts of dispersant, and 6-8 parts of photoinitiator; The carboxyl-containing polymeric monomer includes at least one of acrylic acid, cinnamic acid, and crotonic acid.

[0007] Optionally, the crosslinking agent includes at least one selected from pentaerythritol tetraacrylate, ethoxylated trimethylolpropane triacrylate, and pentaerythritol triacrylate; and / or, The dispersant comprises at least one of polyvinylpyrrolidone, polyethylene glycol, and polyhydroxyethyl methacrylate; and / or, The photoinitiator includes at least one of 2-benzyl-2-(dimethylamino)-4'-morpholinophenylbutanone, tetraethylmielone, and 4,4'-bis(dimethylamino)benzophenone.

[0008] A second aspect of the present invention provides a method for preparing the photosensitive resin as described above, comprising the following steps: Weigh out the carboxyl-containing polymer monomers, crosslinking agents, dispersants, and photoinitiators according to the mass proportions of each raw material of the photosensitive resin; The photosensitive resin is obtained by mixing a carboxyl-containing polymer monomer, a crosslinking agent, a dispersant, and a photoinitiator.

[0009] Optionally, the step of mixing carboxyl-containing polymeric monomers, crosslinking agents, dispersants, and photoinitiators to obtain the photosensitive resin specifically includes: A first solution is obtained by mixing a carboxyl-containing polymer monomer, a crosslinking agent, a dispersant, and a first organic solvent. The photoinitiator is mixed with a second organic solvent to obtain a second solution; The first solution and the second solution are mixed and stirred to obtain a third solution; The photosensitive resin is obtained by evaporating the first and second organic solvents in the third solution.

[0010] A third aspect of the present invention provides a method for preparing metal micro / nano structures, comprising the following steps: The photosensitive resin of the present invention as described above is placed on a substrate, and femtosecond laser printing is performed according to a preset model pattern to obtain an organic polymer micro / nano structure with a preset model pattern. The organic polymer micro / nano structure is immersed in a metal salt solution for a preset time, and then subjected to heat treatment to decompose the organic components. During the heat treatment, the metal is not oxidized, resulting in a metal micro / nano structure with a preset pattern.

[0011] A fourth aspect of the present invention provides a method for preparing metal oxide micro / nano structures, comprising the following steps: The photosensitive resin of the present invention as described above is placed on a substrate, and femtosecond laser printing is performed according to a preset model pattern to obtain an organic polymer micro / nano structure with a preset model pattern. The organic polymer micro / nano structure is immersed in a metal salt solution for a preset time, and then subjected to heat treatment to decompose the organic components. During the heat treatment, the metal is oxidized into oxides to obtain a metal oxide micro / nano structure with a preset pattern.

[0012] Optionally, the steps of obtaining organic polymer micro / nano structures with preset model patterns by femtosecond laser printing specifically include: The preset model pattern is imported into the femtosecond laser printing equipment, the printing parameters are adjusted, and femtosecond laser printing and development are performed. After drying, an organic polymer micro / nano structure with the preset model pattern is obtained.

[0013] Optionally, the concentration of the metal salt solution is 0.5~1 mol / L, and the preset time is 90~120 min.

[0014] In a fifth aspect, the present invention provides a metal micro / nano structure, wherein the structure is prepared by the preparation method described above.

[0015] In a sixth aspect, a metal oxide micro / nano structure is provided, wherein it is prepared by the preparation method described above.

[0016] Beneficial Effects: The photosensitive resin provided by this invention has abundant carboxyl groups and highly efficient metal complexing ability. After femtosecond laser printing, it forms a polymer micro / nano structure with an extremely high density of metal ion capturing sites (carboxyl sites). Therefore, when the printed polymer micro / nano structure is immersed in a metal salt solution, the metal ions can fully coordinate with the carboxyl groups, uniformly and densely anchoring them to the polymer molecular chain through coordination bonds. Furthermore, the carboxyl oxygen atoms have a higher electron density and stronger coordination bonds, which can significantly increase the upper limit of metal loading and reduce cracking during subsequent heat treatment. During the collapse, the carboxyl groups of the polymer micro / nanostructure dissociate into negatively charged carboxylate ions in the metal salt solution. The resulting electrostatic repulsion causes the polymer network to expand, allowing metal ions to better enter the polymer network and penetrate deep into the structure, distributing evenly within it, rather than just adhering to the surface. Then, through heat treatment and strong chemical bond constraints, the structure undergoes isotropic linear shrinkage during sintering, thus achieving a faithful transformation from polymer micro / nanostructures to high-purity metal or metal oxide micro / nanostructures, enabling the fabrication of complex three-dimensional morphologies. Furthermore, this invention uses the aforementioned photosensitive resin to prepare metal or its oxide micro / nano structures. Since the polymerization is achieved first through femtosecond laser printing and then the metal is loaded, it can effectively solve the problem of interference of strong oxidizing metal ions on the laser polymerization reaction (free radical quenching) in traditional methods, greatly expanding the types of metals that can be processed. In addition, the special structure of the photosensitive resin in this invention can enhance the chemical bonding force between metal ions and the polymer micro / nano structure body, overcoming the problem of structural instability of micro / nano structures during thermal conversion. This provides a general technical solution for preparing high-quality, high-resolution three-dimensional metal and metal oxide micro / nano structures, effectively solving the structural collapse problem existing in the current method of printing the scaffold first and then loading the metal. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the preparation process of photosensitive resin in an embodiment of the present invention.

[0018] Figure 2 This is a schematic diagram of the fabrication process of the metal micro / nano structure in an embodiment of the present invention.

[0019] Figure 3 This is a schematic diagram of the fabrication process of metal oxide micro / nano structures in an embodiment of the present invention.

[0020] Figure 4 This is a SEM image of the organic polymer micro / nano structure from Example 1.

[0021] Figure 5The images shown are SEM (scanning electron microscope) images of different micro / nano structures prepared in Examples 1 to 4. Among them, (a) is the gold micro / nano structure prepared in Example 1, (b) is an enlarged view of Figure (a), (c) is the cobalt oxide micro / nano structure prepared in Example 2, (d) is an enlarged view of Figure (c), (e) is the nickel oxide micro / nano structure prepared in Example 3, (f) is an enlarged view of Figure (e), (g) is the chromium oxide micro / nano structure prepared in Example 4, and (h) is an enlarged view of Figure (g). Detailed Implementation

[0022] This invention provides a metal and metal oxide micro / nano structure and a femtosecond laser fabrication method thereof. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0024] If the embodiments of the present invention involve descriptions such as "first" or "second", such descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0025] This invention provides a photosensitive resin, wherein the photosensitive resin comprises the following raw materials in parts by weight: 400-450 parts of carboxyl-containing polymeric monomers, 100-150 parts of crosslinking agent, 80-100 parts of dispersant, and 6-8 parts of photoinitiator; The carboxyl-containing polymeric monomer includes at least one of acrylic acid, cinnamic acid, and crotonic acid.

[0026] In this embodiment of the invention, the carboxyl-containing polymer monomer includes at least one of acrylic acid, cinnamic acid and crotonic acid. The carboxyl oxygen atom has a high electron density and a stronger coordination bond, which can significantly increase the upper limit of metal load and reduce the cracking and collapse of the structure during heat treatment (or sintering).

[0027] The photosensitive resin provided in this invention has abundant carboxyl groups and a highly efficient metal complexing ability. After femtosecond laser printing, it forms a polymer micro / nano structure with an extremely high density of metal ion capturing sites (carboxyl sites). Therefore, when the printed polymer micro / nano structure is immersed in a metal salt solution, the metal ions can fully coordinate with the carboxyl groups and be uniformly and densely anchored to the polymer molecular chain through coordination bonds. Furthermore, the carboxyl oxygen atoms have a higher electron density and stronger coordination bonds, which can significantly increase the upper limit of metal loading and reduce cracking and collapse of the structure during subsequent heat treatment. Simultaneously, in the metal salt solution, the carboxyl groups of the polymer micro / nanostructure dissociate into negatively charged carboxylate ions. The resulting electrostatic repulsion causes the polymer network to expand, allowing metal ions to better enter the polymer network and penetrate deep into the structure, distributing evenly within it, rather than merely adhering to the surface. Then, through heat treatment and strong chemical bond constraints, the structure undergoes isotropic linear shrinkage during sintering, thus achieving a faithful transformation from polymer micro / nanostructures to high-purity metal or metal oxide micro / nanostructures, enabling the fabrication of complex three-dimensional morphologies. Furthermore, this invention uses the aforementioned photosensitive resin to prepare metal or its oxide micro / nano structures. Since the polymerization is achieved first through femtosecond laser printing and then the metal is loaded, it can effectively solve the problem of interference of strong oxidizing metal ions on the laser polymerization reaction (free radical quenching) in traditional methods, greatly expanding the types of metals that can be processed. In addition, the special structure of the photosensitive resin in this invention can enhance the chemical bonding force between metal ions and the polymer micro / nano structure body, overcoming the problem of structural instability of micro / nano structures during thermal conversion. This provides a general technical solution for preparing high-quality, high-resolution three-dimensional metal and metal oxide micro / nano structures, effectively solving the structural collapse problem existing in the current method of printing the scaffold first and then loading the metal.

[0028] In some embodiments, the crosslinking agent includes at least one of pentaerythritol tetraacrylate, ethoxylated trimethylolpropane triacrylate, and pentaerythritol triacrylate, but is not limited thereto.

[0029] In some embodiments, the dispersant includes at least one of polyvinylpyrrolidone, polyethylene glycol, and polyhydroxyethyl methacrylate, but is not limited thereto.

[0030] In some embodiments, the photoinitiator includes, but is not limited to, at least one of 2-benzyl-2-(dimethylamino)-4'-morpholinophenylbutanone, tetraethylmielone, and 4,4'-bis(dimethylamino)benzophenone.

[0031] This invention also provides a method for preparing the photosensitive resin as described above, wherein, as... Figure 1 As shown, it includes the following steps: S11. Weigh the carboxyl-containing polymer monomers, crosslinking agents, dispersants, and photoinitiators according to the mass fractions of each raw material of the photosensitive resin; S12. The carboxyl-containing polymer monomer, crosslinking agent, dispersant and photoinitiator are mixed to obtain the photosensitive resin.

[0032] The preparation method provided by this invention is simple, and the photosensitive resin prepared can be used for printing metal and metal oxide micro / nano structures with complex three-dimensional morphology and stable structure.

[0033] In step S12, in some embodiments, the step of mixing the carboxyl-containing polymer monomer, crosslinking agent, dispersant, and photoinitiator to obtain the photosensitive resin specifically includes: S121. A first solution is obtained by mixing a carboxyl-containing polymeric monomer, a crosslinking agent, a dispersant, and a first organic solvent. S122. The photoinitiator is mixed with the second organic solvent to obtain the second solution; S123. Mix the first solution with the second solution, and stir to obtain a third solution; S124. After evaporating the first and second organic solvents in the third solution, the photosensitive resin is obtained.

[0034] In this embodiment, the carboxyl-containing polymer monomer, crosslinking agent, dispersant, and first organic solvent are first mixed to obtain a first solution; then, the photoinitiator is mixed with a second organic solvent to obtain a second solution; finally, the first solution and the second solution are mixed. This method is more conducive to the rapid dissolution and uniform dispersion of each substance.

[0035] In step S121, in some embodiments, the ratio of the carboxyl-containing polymeric monomer to the first organic solvent is (400~450) mg:(0.5~1) mL, for example, it can be 400 mg:0.5 mL, 400 mg:1 mL, 420 mg:0.5 mL, 420 mg:1 mL, 450 mg:0.5 mL or 450 mg:1 mL, etc.

[0036] In step S122, in some embodiments, the ratio of photoinitiator to second organic solvent is (6~8) mg:(20~40) μL, for example, it can be 6 mg:20 μL, 6 mg:30 μL, 6 mg:40 μL, 8 mg:20 μL, 8 mg:30 μL or 8 mg:40 μL, etc.

[0037] In some embodiments, the first organic solvent and the second organic solvent each independently comprise at least one of acetone, isopropanol, and tetrahydrofuran, but are not limited thereto.

[0038] This invention also provides a method for preparing metal micro / nano structures, wherein, as shown in the embodiments, Figure 2 As shown, it includes the following steps: S21. Place the photosensitive resin (specific components and preparation method are described above) on the substrate, and perform femtosecond laser printing according to the preset model pattern to obtain an organic polymer micro / nano structure with the preset model pattern. S22. The organic polymer micro / nano structure is immersed in a metal salt solution for a preset time, and then subjected to heat treatment to decompose the organic components. During the heat treatment, the metal is not oxidized, resulting in a metal micro / nano structure with a preset pattern.

[0039] This invention also provides a method for preparing metal oxide micro / nano structures, wherein, as... Figure 3 As shown, it includes the following steps: S31. Place the photosensitive resin (specific components and preparation method are described above) on the substrate, and perform femtosecond laser printing according to the preset model pattern to obtain an organic polymer micro / nano structure with the preset model pattern. S32. The organic polymer micro / nano structure is immersed in a metal salt solution for a preset time, and then subjected to heat treatment to decompose the organic components. During the heat treatment, the metal is oxidized into oxides to obtain a metal oxide micro / nano structure with a preset pattern.

[0040] The method provided by this invention is highly versatile and applicable to printing various types of metals or metal oxides. This invention does not limit the type of metal, but as an example, it can be magnetic metals, noble metals, transition metals, or rare earth metals, etc.

[0041] This invention provides a specific photosensitive resin system with highly efficient complexing capabilities. It utilizes femtosecond lasers to precisely fabricate organic polymer micro / nanostructures with a three-dimensional framework (i.e., organic polymer scaffolds). Subsequently, metal ions are uniformly and densely anchored onto the polymer molecular chains through chemical bonding. Finally, a sintering process removes the organic components and induces the transformation of inorganic precursors. This invention effectively solves the problem of metal ion interference with laser polymerization in traditional methods and overcomes the structural instability problem of micro / nanostructures during thermal conversion by enhancing the chemical bonding force between ions and organic polymer micro / nanostructures. It provides a general technical solution for preparing high-quality, high-resolution three-dimensional metal and metal oxide micro / nanostructures.

[0042] Specifically, the photosensitive resin provided by this invention has abundant carboxyl groups and possesses highly efficient metal complexing capabilities. After femtosecond laser printing, it forms a polymer micro / nano structure with an extremely high density of metal ion capturing sites (carboxyl sites). Therefore, when the printed polymer micro / nano structure is immersed in a metal salt solution, metal ions can fully coordinate with the carboxyl groups, uniformly and densely anchoring them to the polymer molecular chain through coordination bonds. Furthermore, the carboxyl oxygen atoms have a higher electron density and stronger coordination bonds, which can significantly increase the upper limit of metal loading and reduce structural cracking during subsequent heat treatment. During the collapse, the carboxyl groups of the polymer micro / nanostructure dissociate into negatively charged carboxylate ions in the metal salt solution. The resulting electrostatic repulsion causes the polymer network to expand, allowing metal ions to better enter the polymer network and penetrate deep into the structure, distributing evenly within it, rather than just adhering to the surface. Then, through heat treatment and strong chemical bond constraints, the structure undergoes isotropic linear shrinkage during sintering, thus achieving a faithful transformation from polymer micro / nanostructures to high-purity metal or metal oxide micro / nanostructures, enabling the fabrication of complex three-dimensional morphologies. Furthermore, this invention uses the aforementioned photosensitive resin to prepare metal or its oxide micro / nano structures. Since the polymerization is achieved first through femtosecond laser printing and then the metal is loaded, it can effectively solve the problem of interference of strong oxidizing metal ions on the laser polymerization reaction (free radical quenching) in traditional methods, greatly expanding the types of metals that can be processed. In addition, the special structure of the photosensitive resin in this invention can enhance the chemical bonding force between metal ions and the polymer micro / nano structure body, overcoming the problem of structural instability of micro / nano structures during thermal conversion. This provides a general technical solution for preparing high-quality, high-resolution three-dimensional metal and metal oxide micro / nano structures, effectively solving the structural collapse problem existing in the current method of printing the scaffold first and then loading the metal.

[0043] In steps S21 and S31, in some embodiments, the step of performing femtosecond laser printing according to a preset model pattern to obtain an organic polymer micro / nano structure with a preset model pattern specifically includes: The preset model pattern is imported into the femtosecond laser printing equipment, the printing parameters are adjusted, and femtosecond laser printing and development are performed. After drying, an organic polymer micro / nano structure with the preset model pattern is obtained.

[0044] In steps S22 and S32, after the carboxyl-containing polymer monomer and the crosslinking agent undergo photopolymerization, the polymer network has nanopores. When immersed in a metal salt solution, the carboxyl groups ionize, the polymer network swells, the pore channels become larger, and metal ions can diffuse and permeate from the outside to the inside along the network pores.

[0045] In some embodiments, the concentration of the metal salt solution is 0.5~1 mol / L (e.g., 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, or 1 mol / L, etc.), and the preset time is 90~120 min (e.g., 90 min, 100 min, 110 min, or 120 min, etc.). This ensures that the carboxyl groups of the carboxyl-containing polymer monomers are fully bonded and coordinated with the metal ions, thus guaranteeing structural stability.

[0046] In this embodiment, the metal salt solution can be soaked once or in multiple cycles.

[0047] In some embodiments, the organic polymer micro / nanostructure is immersed in a metal salt solution at a temperature of 80-85°C (e.g., 80°C, 81°C, 82°C, 83°C, 84°C, or 85°C). This higher temperature significantly increases the diffusion rate of metal ions in the aqueous solution, allowing ions to penetrate more quickly into the scaffold of the organic polymer micro / nanostructure. At 85°C, close to the boiling point but without violent boiling, the high temperature is retained while avoiding the impact of boiling and potential damage to the delicate organic polymer micro / nanostructure.

[0048] In some embodiments, the heating rate before heat treatment is 0.8~1 °C / min.

[0049] This invention also provides a metal micro / nano structure, which is prepared using the preparation method described above.

[0050] The metal micro / nano structure provided by this invention has a stable structure and is expected to be used as a functional material, catalytic material, sensing material, energy storage material, optical material or biomedical material.

[0051] In addition, the metal can be magnetic metal, precious metal, transition metal or rare earth metal, etc.

[0052] This invention also provides a metal oxide micro / nano structure, which is prepared using the preparation method described above.

[0053] The metal oxide micro / nano structure provided by this invention has a stable structure and is expected to be used as a functional material, catalytic material, sensing material, energy storage material, optical material or biomedical material.

[0054] In addition, the metal oxides can be magnetic metal oxides, noble metal oxides, transition metal oxides, or rare earth metal oxides, etc.

[0055] The present invention will be further described below through specific embodiments.

[0056] Unless otherwise specified, the raw materials and equipment used in the following embodiments are all commercially available products.

[0057] The femtosecond laser printing equipment used in the following embodiments was purchased from Anyang Laser Technology Co., Ltd., and the model is FemtoY.

[0058] Example 1 This embodiment provides a method for preparing gold micro / nano structures, including the following steps: (1) Preparation of acrylic photosensitive resin: 420 mg acrylic acid, 120 mg pentaerythritol tetraacrylate, 100 mg polyvinylpyrrolidone and 0.5 mL acetone were mixed and ultrasonically dispersed until the system was homogeneous to obtain the first solution; 8 mg of 2-benzyl-2-(dimethylamino)-4'-morpholinophenylbutanone was mixed with 40 μL of acetone and stirred until completely dissolved to obtain a second solution; The first solution and the second solution were mixed and stirred for 10 minutes until all components were homogeneous and compatible, thus obtaining a photosensitive resin solution. After waiting for the acetone in the photosensitive resin solution to evaporate in a fume hood, an acrylic-based photosensitive resin is obtained.

[0059] (2) Sample preparation: Place the quartz slide on the glass slide and fix it on both sides with two layers of tape. Add acrylic photosensitive resin to the quartz slide, then cover it with a coverslip and fix it on both sides with a layer of tape. Then fix it on the three-dimensional displacement platform.

[0060] (3) Laser focusing: Add a small amount of refractive index modulated oil droplet to the 40x objective lens and adjust the position of the femtosecond laser (1030 nm, 1 MHz, 300 fs) focused spot after passing through the 40x objective lens to the surface of the quartz plate.

[0061] (4) Printing Structure: Import the model to be printed, adjust the laser printing parameters (output power of 40 mW, slice spacing of 300 nm, fill spacing of 300 nm, printing speed of 10 mm / s), and after printing, development (acetone and isopropanol mixed in a 1:3 ratio for 50 s) and drying, obtain the organic polymer micro / nano structure (e.g. Figure 4 (As shown).

[0062] (5) Post-processing: The organic polymer micro-nano structure was immersed in a 0.5 mol / L chloroauric acid solution and heated at 85°C for 2 h to allow the carboxyl groups of acrylic acid and metal ions in the structure to fully undergo coordination reaction. Then, the excess metal ions were washed away with deionized water to load the metal into the organic polymer micro-nano structure, thus obtaining an organic-metal composite micro-nano structure.

[0063] (6) Heat treatment: The organic-metal composite structure was placed in a tube furnace for heat treatment in an air atmosphere. The temperature was increased to 550 °C at a heating rate of 1 °C / min and held at 550 °C for 2 h, followed by natural cooling. During the heat treatment, the organic components were decomposed, and the gold was not oxidized, resulting in a dense gold micro / nano structure. The specific morphology of the structure is as follows: Figure 5 As shown in (a) and (b) in the figure.

[0064] Example 2 This embodiment provides a method for preparing cobalt oxide micro / nano structures, which is basically the same as the preparation method in Example 1, with the only difference being: In step (5), the organic polymer micro / nano structure is immersed in a cobalt nitrate solution with a concentration of 0.5 mol / L; In step (6), during the heat treatment process, the organic components are decomposed, and cobalt is oxidized to cobalt oxide, ultimately yielding a dense cobalt oxide micro / nano structure, the specific structural morphology of which is as follows: Figure 5 As shown in (c) and (d) in the figure.

[0065] Example 3 This embodiment provides a method for preparing nickel oxide micro / nano structures, which is basically the same as the preparation method in Example 1, with the only difference being: In step (5), the organic polymer micro / nano structure is immersed in a nickel nitrate solution with a concentration of 0.5 mol / L; In step (6), during the heat treatment process, the organic components are decomposed, and nickel is oxidized to nickel oxide, ultimately yielding a dense nickel oxide micro / nano structure, the specific structural morphology of which is as follows: Figure 5 As shown in (e) and (f) in the figure.

[0066] Example 4 This embodiment provides a method for preparing chromium oxide micro / nano structures, which is basically the same as the preparation method in Example 1, with the only difference being: In step (5), the organic polymer micro / nano structure is immersed in a 0.5 mol / L chromium nitrate solution; In step (6), during the heat treatment process, the organic components are decomposed, and chromium is oxidized to chromium oxide, ultimately yielding a dense chromium oxide micro / nano structure, the specific structural morphology of which is as follows: Figure 5 As shown in (g) and (h).

[0067] Example 5 This embodiment provides a method for preparing gold micro / nano structures, including the following steps: (1) Preparation of acrylic photosensitive resin: 450 mg cinnamic acid, 150 mg ethoxylated trimethylolpropane triacrylate, 80 mg polyethylene glycol and 1 mL acetone were mixed and ultrasonically dispersed until the system was homogeneous to obtain the first solution; Mix 6 mg of tetraethylmielone with 20 μL of acetone and stir until completely dissolved to obtain a second solution; The first solution and the second solution were mixed and stirred for 10 minutes until all components were homogeneous and compatible, thus obtaining a photosensitive resin solution. After waiting for the acetone in the photosensitive resin solution to evaporate in a fume hood, cinnamic acid-based photosensitive resin is obtained.

[0068] (2) Sample preparation: Same as step (2) in Example 1.

[0069] (3) Laser focusing: Same as step (3) in Example 1.

[0070] (4) Printing structure: It is basically the same as step (4) in Example 1, except that the output power is 35 mW.

[0071] (5) Post-processing: Same as step (5) in Example 1.

[0072] (6) Heat treatment: Same as step (6) in Example 1, finally a dense gold micro-nano structure is obtained, and its structural morphology is the same as that in Example 1.

[0073] Example 6 This embodiment provides a method for preparing cobalt oxide micro / nano structures, including the following steps: (1) Preparation of acrylic photosensitive resin: 400 mg of crotonic acid, 100 mg of pentaerythritol triacrylate, 90 mg of polyvinylpyrrolidone and 0.5 mL of acetone were mixed and ultrasonically dispersed until the system was homogeneous to obtain the first solution; 7 mg of 4,4'-bis(dimethylamino)benzophenone was mixed with 30 μL of acetone and stirred until completely dissolved to obtain a second solution; The first solution and the second solution were mixed and stirred for 10 minutes until all components were homogeneous and compatible, thus obtaining a photosensitive resin solution. After waiting for the acetone in the photosensitive resin solution to evaporate in a fume hood, crotonic acid-based photosensitive resin is obtained.

[0074] (2) Sample preparation: Same as step (2) in Example 2.

[0075] (3) Laser focusing: Same as step (3) in Example 2.

[0076] (4) Printing structure: It is basically the same as step (4) in Example 2, except that the output power is 33 mW.

[0077] (5) Post-processing: Same as step (5) in Example 2.

[0078] (6) Heat treatment: Same as step (6) in Example 2, and finally a dense cobalt oxide micro-nano structure with the same structural morphology as in Example 2 is obtained.

[0079] In summary, this invention provides a metal and metal oxide micro / nanostructure and its femtosecond laser fabrication method. The photosensitive resin provided by this invention has abundant carboxyl groups and possesses highly efficient metal complexing ability. After femtosecond laser printing, a polymer micro / nanostructure is formed, which has an extremely high density of metal ion capturing sites (carboxyl sites). Therefore, after immersing the printed polymer micro / nanostructure in a metal salt solution, metal ions can fully coordinate with the carboxyl groups and be uniformly and densely anchored to the polymer molecular chain through coordination bonds. Furthermore, the carboxyl oxygen atoms have a higher electron density and stronger coordination bonds, which can significantly increase the upper limit of metal loading. This method reduces cracking and collapse of the structure during subsequent heat treatment. Simultaneously, in the metal salt solution, the carboxyl groups of the polymer micro / nanostructure dissociate into negatively charged carboxylate ions. The resulting electrostatic repulsion causes the polymer network to expand, allowing metal ions to better penetrate and uniformly distribute within the deep layers of the structure, rather than merely adhering to the surface. Following heat treatment, the structure undergoes isotropic linear shrinkage during sintering due to strong chemical bond constraints, achieving a faithful transformation from polymer micro / nanostructures to high-purity metal or metal oxide micro / nanostructures. This enables the fabrication of complex three-dimensional morphologies. Furthermore, this invention uses the aforementioned photosensitive resin to prepare metal or its oxide micro / nanostructures. Because the polymerization is achieved first using femtosecond laser printing, followed by metal loading, the interference of strong oxidizing metal ions on the laser polymerization reaction (free radical quenching) in traditional methods is effectively solved. This greatly expands the types of metals that can be processed, while also ensuring precise laser focusing on the photoresist. Furthermore, the special structure of the photosensitive resin in this invention can enhance the chemical bonding force between metal ions and the polymer micro / nano structure, overcoming the problem of structural instability of micro / nano structures during thermal conversion. This provides a general technical solution for preparing high-quality, high-resolution three-dimensional metal and metal oxide micro / nano structures, effectively solving the structural collapse problem existing in the current method of printing the scaffold first and then loading the metal.

[0080] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A photosensitive resin, characterized in that, The photosensitive resin comprises the following raw materials in parts by weight: 400-450 parts of carboxyl-containing polymeric monomers, 100-150 parts of crosslinking agent, 80-100 parts of dispersant, and 6-8 parts of photoinitiator; The carboxyl-containing polymeric monomer includes at least one of acrylic acid, cinnamic acid, and crotonic acid.

2. The photosensitive resin according to claim 1, characterized in that, The crosslinking agent includes at least one selected from pentaerythritol tetraacrylate, ethoxylated trimethylolpropane triacrylate, and pentaerythritol triacrylate; and / or, The dispersant comprises at least one of polyvinylpyrrolidone, polyethylene glycol, and polyhydroxyethyl methacrylate; and / or, The photoinitiator includes at least one of 2-benzyl-2-(dimethylamino)-4'-morpholinophenylbutanone, tetraethylmielone, and 4,4'-bis(dimethylamino)benzophenone.

3. A method for preparing the photosensitive resin according to any one of claims 1-2, characterized in that, The steps include the following: Weigh out the carboxyl-containing polymer monomers, crosslinking agents, dispersants, and photoinitiators according to the mass proportions of each raw material of the photosensitive resin; The photosensitive resin is obtained by mixing a carboxyl-containing polymer monomer, a crosslinking agent, a dispersant, and a photoinitiator.

4. The preparation method according to claim 3, characterized in that, The specific steps of mixing carboxyl-containing polymeric monomers, crosslinking agents, dispersants, and photoinitiators to obtain the photosensitive resin include: A first solution is obtained by mixing a carboxyl-containing polymer monomer, a crosslinking agent, a dispersant, and a first organic solvent. The photoinitiator is mixed with a second organic solvent to obtain a second solution; The first solution and the second solution are mixed and stirred to obtain a third solution; The photosensitive resin is obtained by evaporating the first and second organic solvents in the third solution.

5. A method for preparing a metal micro / nano structure, characterized in that, The steps include the following: The photosensitive resin described in any one of claims 1-2 is placed on a substrate, and femtosecond laser printing is performed according to a preset model pattern to obtain an organic polymer micro / nano structure with a preset model pattern. The organic polymer micro / nano structure is immersed in a metal salt solution for a preset time, and then subjected to heat treatment to decompose the organic components. During the heat treatment, the metal is not oxidized, resulting in a metal micro / nano structure with a preset pattern.

6. A method for preparing metal oxide micro / nano structures, characterized in that, The steps include the following: The photosensitive resin described in any one of claims 1-2 is placed on a substrate, and femtosecond laser printing is performed according to a preset model pattern to obtain an organic polymer micro / nano structure with a preset model pattern. The organic polymer micro / nano structure is immersed in a metal salt solution for a preset time, and then subjected to heat treatment to decompose the organic components. During the heat treatment, the metal is oxidized into oxides to obtain a metal oxide micro / nano structure with a preset pattern.

7. The preparation method according to claim 5 or 6, characterized in that, The specific steps involved in obtaining organic polymer micro / nano structures with preset model patterns through femtosecond laser printing include: The preset model pattern is imported into the femtosecond laser printing equipment, the printing parameters are adjusted, and femtosecond laser printing and development are performed. After drying, an organic polymer micro / nano structure with the preset model pattern is obtained.

8. The preparation method according to claim 5 or 6, characterized in that, The concentration of the metal salt solution is 0.5~1 mol / L, and the preset time is 90~120 min.

9. A metallic micro / nano structure, characterized in that, It was prepared using the preparation method described in claim 5.

10. A metal oxide micro / nano structure, characterized in that, It was prepared using the preparation method described in claim 6.

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