A method for preparing micro-nano three-dimensional metal and alloy structure

Abstract

The application provides a preparation method of a micro-nano three-dimensional metal and alloy structure. Based on a photoresist material, the application combines a photo-curing 3D printing technology, a chemical plating technology, high-temperature annealing ester removal and metallurgy technology, and invents a manufacturing method of a three-dimensional micro-nano structure of a metal and alloy structure, effectively improves metal ion concentration in an organic structure and additive manufacturing efficiency of a metal structure, and realizes high-efficiency, low-shrinkage and low-distortion additive manufacturing of a metal and alloy three-dimensional micro-nano structure.

Description

Technical Field

[0001] This invention relates to the field of metal micro-nano 3D printing technology, and in particular to a method for preparing micro-nano three-dimensional metal and alloy structures. Background Technology

[0002] Due to their small size and high specific surface area, three-dimensional metal micro- and nanostructures have become an important research direction in fields such as low-energy-consumption, high-efficiency, and high-sensitivity optoelectronic micro- and nanostructure devices and high-strength metal-based metamaterials. Macroscopic and mesoscopic metal structure 3D printing is relatively mature, such as selective laser melting (SLM) and electron beam melting. However, due to limitations such as metal powder particle size and the strong interaction between lasers or electron beams and metal particles, metal 3D printing with resolutions below 100 micrometers or even nanometers still faces significant challenges.

[0003] In the past decade, with the continuous development of micro-nano manufacturing technology and materials science, breakthroughs have been achieved in the fabrication of micro- and nano-scale metal 3D structures. For example, Chinese patent application No. 201910820833.5 proposed a method that uses a photosensitive material layer as a mask, and then combines it with subtractive methods such as dry etching to etch multiple layers of deposited metal to form a 3D structure. However, this method requires repeated steps of spin-coating photosensitive material and then photolithography to form a mask for each metal layer, resulting in low efficiency and difficulty in reproducible positioning. In 2018, the journal article "Additive manufacturing of 3D nano-architected metals" used photopolymerization micro- and nano-3D printing technology to directly print inorganic-organic hybrid photosensitive resin doped with metal ions, and then used high-temperature sintering to remove the organic components to construct the metal micro- and nano-3D structure. This method, however, requires separate preparation of photosensitive resin for each metal, which limits the types of materials available. Furthermore, due to the low concentration of metal ions, the final structure has a shrinkage rate of 70% or higher, resulting in severe shape distortion and limiting the application of metal 3D micro- and nano-structures. In 2022, the journal article "Additive manufacturing of micro-architected metals via hydrogel infusion" also utilized photopolymerization micro / nano 3D printing technology to first print hydrogel 3D microstructures, then immerse the hydrogel 3D structures in a metal ion solution, and finally remove the organic components of the hydrogel through high-temperature annealing to construct the metal micro / nano 3D structure. This method also suffers from a shrinkage rate of nearly 75%, and as the micro / nano structure shrinks further, the binding ability of the hydrogel structure to metal ions decreases, making it difficult to guarantee the printing of nanoscale metal structures. In addition, other methods, such as direct laser reduction, electrochemical in-situ deposition, and photochemical bonding, for constructing metal micro / nano 3D structures all suffer from low forming efficiency (speeds of only 10-100 micrometers per second), making it difficult to meet the needs of future large-scale applications.

[0004] In summary, current technology is not yet capable of achieving customized fabrication of complex 3D metal structures with low shrinkage rates, rapid processing, and high precision at the micro- and nano-scale. Therefore, achieving high processing efficiency and low shrinkage rates in the fabrication of micro / nano 3D metal structures is a pressing technical challenge that needs to be addressed. Summary of the Invention

[0005] In view of this, the present invention proposes a method for preparing micro / nano three-dimensional metal and alloy structures. Based on the photoresist material of the present invention, combined with photopolymerization 3D printing technology, chemical plating technology, and high-temperature annealing deesterification and metallurgical technology, the concentration of metal ions in organic structures and the additive manufacturing efficiency of metal structures are effectively improved, realizing the additive manufacturing of high-efficiency, low-shrinkage and low-distortion metal and alloy three-dimensional micro / nano structures.

[0006] The technical solution of this invention is implemented as follows: This invention provides a method for preparing micro / nano three-dimensional metal and alloy structures, comprising the following steps: S1, Preparation of photoresist material; S2, using laser two-photon polymerization 3D printing method to form photoresist material, forming a 3D organic micro-nano structure with rich and uniform nanopores, and then developing it; S3, after development, the three-dimensional micro-nano porous organic structure is subjected to amination treatment and metal seed source is introduced to obtain a 3D organic micro-nano structure enriched with metal nanoparticles. S4. The 3D organic micro-nano structure from step S3 is immersed in a chemical plating solution for chemical plating treatment to obtain a metal-organic composite three-dimensional micro-nano structure. S5, the target three-dimensional metal micro / nano structure sample is obtained through low-temperature annealing and / or high-temperature metallurgical processes.

[0007] Based on the above scheme, preferably, the photoresist material includes a pore-forming agent, which includes a mixture of dodecyl acetate and octadecyl acetate or a mixture of 1-decyl alcohol and cyclohexanol; more preferably, the pore-forming agent is a mixture of dodecyl acetate and octadecyl acetate.

[0008] Based on the above scheme, preferably, the photoresist material further includes photosensitive resin monomer, organic functional monomer, initiator and photosensitizer.

[0009] The photoresist material of the present invention has photocuring 3D printing capability, photopolymerization-induced phase separation to generate porous structure capability, and metal ion chelation and adsorption capability.

[0010] Based on the above scheme, preferably, the photosensitive resin monomer includes one or more of unsaturated acrylate, polyurethane, and epoxy resin.

[0011] The main function of the photosensitive resin monomer is to ensure that the micro-nano structure printed by photopolymerization has sufficient support strength and high-resolution forming effect; more preferably, the photosensitive resin monomer is an unsaturated acrylate, and even more preferably, the photosensitive resin monomer is a multifunctional unsaturated acrylate.

[0012] Based on the above scheme, preferably, the organic functional monomer comprises any one of 1-vinylimidazolium, methacrylic acid, acrylic acid, vinylpyrrolidone, vinylpyrimidine, acrylamide, and vinylpyrazine.

[0013] The organic functional monomer possesses both photocurable polymerization capability and the ability to adsorb metal ions. This organic functional monomer has unsaturated chemical bonds, such as C=C bonds, which can undergo free radical polymerization with photosensitive resin monomers under photoinitiation to form a copolymer crosslinking network. At the same time, the imidazole groups, pyrimidine groups, and other chemical groups in the organic functional monomer can stably adsorb metal ions in the form of coordination bonds, introducing a seed source for subsequent chemical plating processes. More preferably, the organic functional monomer is 1-vinylimidazole.

[0014] Based on the above scheme, preferably, the initiator comprises one or more of phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, 4-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone, and phenyl-(2,4,6-trimethylbenzoyl)lithium phosphate, which has a photoinitiating effect; more preferably, the initiator is phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide.

[0015] Based on the above scheme, preferably, the photosensitizer includes one or more of methylene blue, rhodamine 6G, rhodamine 123, rhodamine B, triethanolamine, and 2-phenyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone, the purpose of which is to improve the photopolymerization efficiency; more preferably, the photosensitizer is 2-phenyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone.

[0016] Based on the above scheme, preferably, the ratio of photosensitive resin monomer: porogen: organic functional monomer is 10: (1~20): (0.1~20).

[0017] The proportion of pore-forming agent not only determines the size of the nanopores in the organic structure, but is also closely related to the pore density. In practical applications, the proportion of pore-forming agent can be determined according to the actual size and characteristic dimensions of the micro / nano structure to improve the manufacturing precision and efficiency of the metal micro / nano structure. This invention provides a large amount of space for subsequent in-situ self-growth of metal through the generation of uniform and dense pores in the organic structure, which is an important aspect of realizing low-shrinkage and distortion-free three-dimensional metal structures. The proportion of organic functional monomers mainly determines the amount of metal ions that the formed organic structure can adsorb, thereby determining the concentration of the metal seed source and the time required for the subsequent chemical plating process. More preferably, the ratio of photosensitive resin monomer: pore-forming agent: organic functional monomer is 10:12:8.

[0018] Based on the above scheme, preferably, the sum of the amounts of the photoinitiator and photosensitizer is 0.1% to 10% of the total mass of the photosensitive resin monomer and the organic functional monomer. This ratio mainly determines the laser energy density and initiation efficiency required to induce photopolymerization. More preferably, the sum of the amounts of the photoinitiator and photosensitizer is 4% of the total mass of the photosensitive resin monomer and the organic functional monomer.

[0019] Based on the above scheme, preferably, the mass ratio of the photoinitiator to the photosensitizer is 1:0.1~5, and more preferably, the mass ratio of the photoinitiator to the photosensitizer is 1:1.

[0020] Based on the above scheme, preferably, a certain proportion of photosensitive resin monomers and organic functional monomers are mixed and stirred manually or magnetically until completely mixed and homogeneous. A certain proportion of photosensitizers and photoinitiators are weighed and added to the mixed adhesive. The resulting mixed precursor is ultrasonicated at a frequency of 20-50 kHz, preferably 40 kHz, for 15 minutes, until the solid initiator and photosensitizer are completely dissolved in the mixed monomers. Then, a porogen is added at a ratio of 120% of the mass of the photosensitive resin monomers. The above-mentioned precursor containing monomers, photoinitiators, photosensitizers, and porogens is magnetically stirred for 5-10 minutes until the precursor is completely mixed and homogeneous, and is in a transparent liquid state.

[0021] Based on the above scheme, in a further preferred embodiment, in step S2, a photoresist material is used to perform 3D printing using a femtosecond laser two-photon polymerization 3D printing device. Then, the formed structure is placed in a developing solution, such as an acetone solution, and soaked for 1 hour until the pore-forming agent, unpolymerized monomers, and oligomers remaining in the 3D structure are fully dissolved in the developing solution. Finally, a three-dimensional organic micro / nano structure with a certain proportion of pores can be obtained, which has porous structure, metal ion adsorption, and good forming performance.

[0022] Based on the above scheme, preferably, in step S3, the amination treatment solution is a mixed solution of ethanol and polyamine molecules with a volume ratio of 1:0.1~1, and the amination treatment time is 1~12 h; the metal seed source introduction process includes immersing the amination-treated micro-nano structure in a metal ion solution for 15~30 minutes to form a metal ion-organic porous micro-nano structure, and then using a reducing agent to reduce the metal ions to metal particles as a seed source.

[0023] Based on the above scheme, preferably, in step S3, the concentration of the metal ion solution used in the metal seed source introduction process is ≥0.1mol / L, and the reducing agent includes one or more of sodium borohydride, potassium borohydride, hydrazine and their derivatives.

[0024] Based on the above scheme, preferably, in step S3, the polyamine molecule in the amination treatment is selected from one or more of ethylenediamine, hexamethylenediamine, polyethylene polyamine, polyethyleneimine, dendritic polyamide-amine, or chitosan.

[0025] Based on the above scheme, a further preferred embodiment is that the polyamine molecule is ethylenediamine and the reducing agent is sodium borohydride.

[0026] Amination is a process of functionalizing the surface of porous micro / nano structures with amine groups, which further enhances the adsorption capacity of porous micro / nano structures for metal ions. The metal seed source is a prerequisite for subsequent chemical plating processes.

[0027] Based on the above scheme, a further optimized method involves dissolving polyamine molecules in ethanol to form a reaction system with a volume ratio of polyamine molecules to ethanol of 0.2:1. The printed and developed three-dimensional micro / nano structure is then immersed in the reaction system and allowed to stand at room temperature for 1 hour. It is then washed sequentially with ethanol and deionized water to obtain a porous micro / nano polymer structure with surface-functionalized amino groups. The amination-treated micro / nano structure is then immersed in a palladium chloride solution. A certain mass of palladium ions is adsorbed using monomers with metal ion chelating function co-polymerized within the micro / nano structure and the amination-treated polyamine molecules. The adsorption time is 15 minutes, forming a palladium ion-organic porous micro / nano structure. This porous micro / nano structure is then immersed in a 10 g / L reducing agent solution for 10 minutes to chemically reduce the palladium ions in situ to palladium nanoparticles. Repeating the adsorption step with palladium chloride solution and the reduction step with sodium borohydride solution three times further increases the number of palladium particles in the final organic structure, providing more seed sources for subsequent electroless plating and facilitating plating initiation.

[0028] Based on the above scheme, preferably, in step S4, the 3D organic micro / nano structure from step S3 is immersed in a chemical plating solution for chemical plating treatment to obtain a metal-organic composite three-dimensional micro / nano structure, wherein the volume and mass fraction of the metal reaches 50% and 80% or more, respectively; the specific chemical plating solution formula can be configured according to existing literature or commercial formulas. The chemical plating solution includes chemical copper plating solution, chemical gold plating solution, chemical silver plating solution, chemical cobalt plating solution, chemical nickel plating solution, etc., depending on the type of target metal structure. It can also realize the chemical plating solution of alloys, including copper-nickel alloy binary plating solution, nickel-cobalt-iron-cerium-lanthanum pentagonal plating solution, and other multi-element alloy plating solutions.

[0029] Based on the above scheme, preferably, in step S5, the target three-dimensional metal micro / nano structure sample is obtained by low-temperature annealing and / or high-temperature metallurgical process.

[0030] Based on the above scheme, preferably, in step S4, the temperature during in-situ metal deposition is 20~80℃ and the pH is 4~11; more preferably, the temperature is 60℃ and the pH is 8~9.

[0031] Based on the above scheme, preferably, in step S5, the low-temperature annealing process includes gradually heating from room temperature to 550~650℃ and then naturally cooling.

[0032] Based on the above scheme, a further preferred embodiment of the low-temperature annealing process is as follows: under a pressure of 400 torr and an air intake velocity of 150 sccm, the temperature is raised to 220°C at room temperature for 2 hours, held at 220°C for 2 hours, then raised from 220°C to 550°C for 2 hours, held at 550°C for 2 hours, then raised from 550°C to 620°C for 2 hours, and finally held at 620°C for 2 hours, and finally cooled naturally to room temperature. The temperature gradient set in this process is mainly based on the decomposition and volatilization temperatures of different organic elements in the metal-organic composite structure, which can effectively improve the removal rate of organic elements, regardless of the type of metal.

[0033] Based on the above scheme, preferably, in step S5, the high-temperature metallurgical process includes heating from room temperature to 650~1100℃ at a specific rate in a mixed atmosphere of hydrogen and argon, holding at that temperature, and then cooling down to 600℃ and then naturally cooling.

[0034] Based on the above scheme, a further preferred embodiment of the high-temperature metallurgical process is as follows: under a pressure of 22 torr and an inlet gas mixture of hydrogen and argon (5% hydrogen) at a rate of 160 sccm, the temperature is increased from room temperature to 880°C at a rate of 3°C per minute, held at 880°C for 6 hours, and then slowly cooled to 600°C at a rate of 1°C per minute, finally allowing it to cool naturally to room temperature. This process mainly uses high temperature and reducing gas to reduce the sample after low-temperature annealing from the metal oxide state to the elemental metal, and by reaching the sintering temperature of the metal at high temperature, the apparent porosity can be reduced to zero, maximizing the metal density and metal properties. Since different metals have different sintering temperatures, the sintering temperature needs to be adjusted according to the specific metal type. For example, the sintering temperature of elemental copper can be set to 850℃, elemental nickel to 900℃, copper-nickel alloy to 880℃, and nickel-cobalt-iron-cerium-lanthanum multi-element alloy to 1100℃. Of course, for non-reactive metals such as gold, silver, and platinum, due to their low sintering temperature and the lack of further reduction, three-dimensional metal structure samples can be obtained after the low-temperature sintering process without the need for high-temperature metallurgical processes.

[0035] The method for preparing micro / nano three-dimensional metal and alloy structures of the present invention has the following advantages over the prior art: (1) A photoresist material that integrates photopolymerization 3D printing capability, photopolymerization-induced phase separation to generate porous structure capability, and metal ion chelation and adsorption capability is adopted. It can not only form micro-nano complex three-dimensional structures using femtosecond laser micro-nano 3D printing method, but also has nanopores for adsorbing metal ions and chemical plating filling. This brings two significant effects to the final micro-nano metal 3D printing: First, the organic photoresist-based material can be printed quickly, with a printing speed of 10~1000 mm / s, which is 1000~100000 times faster than electrochemical deposition or laser photoreduction methods, and has the advantage of high-efficiency printing; Second, by creating air holes first and then filling metal, the metal content per unit volume can be greatly increased, thereby reducing the shrinkage rate of the final structure. The minimum linear shrinkage rate can reach 15%, which is only 1 / 5~1 / 3 of the current femtosecond laser direct printing of metal ion-organic resin composite materials and similar methods, ensuring distortion-free shape preservation capability; (2) The organic functional monomers and photosensitive resin monomers in the photoresist material have a synergistic effect and can undergo free radical polymerization under photoinitiation to form a copolymer crosslinking network. At the same time, the imidazole group, pyrimidine group and other chemical groups in the organic functional monomers can stably adsorb metal ions in the form of coordination bonds, which forms a good foundation for the subsequent chemical plating process. (3) The pore-forming agent in the photoresist material undergoes phase separation during the photopolymerization reaction triggered by light. This phase separation process forms a porous structure. The subsequent chemical plating process allows metal ions to be evenly distributed in the pores, thus giving the final product the advantages of low shrinkage and low deformation. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 Flowchart of the method for manufacturing micro / nano-scale three-dimensional complex metal and alloy structures by photopolymerization printing according to the present invention; Figure 2 This is a schematic diagram of the photoresist material preparation process of the present invention; Figure 3 This is a scanning electron microscope (SEM) image of a three-dimensional organic structure with nanopores obtained by laser direct writing printing in Example 10 of the present invention. Figure 4 This diagram illustrates the additive manufacturing method and process steps for the distortion-free, low-shrinkage three-dimensional micro / nano metal structure of the present invention. Figure 5 This is a scanning electron microscope (SEM) image of the three-dimensional nickel metallic structure of Embodiment 11 of the present invention; Figure 6 This is an X-ray energy spectrum diagram of the constituent elements of the three-dimensional metallic nickel structure in Embodiment 11 of the present invention; Figure 7 This is the X-ray energy dispersive spectroscopy result of the constituent elements of the three-dimensional metallic iron-cobalt-nickel-cerium-lanthanum multi-element alloy structure in Example 14 of the present invention. Detailed Implementation

[0038] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0039] Example 1: Preparation of photoresist material Take 1 mL of pentaerythritol triacrylate and 0.8 mL of 1-vinylimidazole, and stir until they are evenly mixed. Then weigh 36 mg of photoinitiator Irg.819 (phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide) and 36 mg of photosensitizer 2-phenyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone (Irg.369), and add them to the above-mentioned evenly mixed precursor. Sonicate for 15 minutes until the photoinitiator and photosensitizer are completely dissolved. Next, measure 0.6 mL of dodecyl acetate and 0.6 mL of octadecyl acetate as mixed pore-forming agents and add them to the above-mentioned photoresist precursor. Continue stirring until evenly mixed to obtain a transparent liquid multifunctional photoresist material with photocuring ability, porous structure generation ability, and metal ion chelation ability.

[0040] Example 2: Preparation of photoresist material Take 1 mL of dipentaerythritol hexaacrylate and 0.8 mL of acrylic acid, and stir until they are evenly mixed. Then weigh 36 mg of photoinitiator LAP (phenyl-2,4,6-trimethylbenzoyl lithium phosphite) and 200 μL of photosensitizer triethanolamine, and add them to the above-mentioned evenly mixed precursor. Sonicate for 15 minutes until the photoinitiator and photosensitizer are completely dissolved. Next, measure 0.5 mL of 1-decyl alcohol and 1.25 mL of cyclohexanol as mixed pore-forming agents and add them to the above-mentioned photoresist precursor. Continue stirring until homogeneous to obtain a transparent liquid multifunctional photoresist material with photocuring ability, ability to generate porous structures, and metal ion chelation ability.

[0041] Example 3: Preparation of photoresist materials Mix 0.5 mL of dipentaerythritol hexaacrylate and 0.5 mL of trimethylolpropane triacrylate, then add 0.7 mL of vinylpyrrolidone and stir until the three are evenly mixed. Then weigh 26 mg of photoinitiator Irg.2959 (4-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone) and 17 mg of photosensitizer methylene blue, and add them to the above-mentioned evenly mixed precursor. Sonicate for 30 minutes until the photoinitiator and photosensitizer are completely dissolved to obtain a photoresist precursor with photocuring ability and metal ion chelating ability. Next, weigh 0.8 mL of dodecyl acetate and 1.5 mL of octadecyl acetate as mixed pore-forming agents and add them to the above-mentioned photoresist precursor. Stir evenly to obtain a transparent liquid multifunctional photoresist material with photocuring ability, porous structure generation ability and metal ion chelating ability.

[0042] Example 4: Preparation of photoresist material This embodiment is the same as Example 1, except that: 0.05 mL of dodecyl acetate and 0.05 mL of octadecyl acetate are measured as mixed porogens, and 0.01 mL of 1-vinylimidazole is used as an organic functional monomer.

[0043] Example 5: Preparation of photoresist material This embodiment is the same as Example 1, except that: 1 mL of dodecyl acetate and 1 mL of octadecyl acetate are measured as mixed porogens, and 2 mL of 1-vinylimidazole is used as an organic functional monomer.

[0044] Example 6: Preparation of photoresist material This embodiment is the same as Example 1, except that: 0.9 mg of photoinitiator Irg.819 (phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide) and 0.9 mg of photosensitizer 2-phenyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone (Irg.369) are used.

[0045] Example 7: Preparation of photoresist material This embodiment is the same as Example 1, except that: 90 mg of photoinitiator Irg.819 (phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide) and 90 mg of photosensitizer 2-phenyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone (Irg.369) are used.

[0046] Example 8: Preparation of photoresist material This embodiment is the same as Example 1, except that: 36 mg of photoinitiator Irg.819 (phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide) and 3.6 mg of photosensitizer 2-phenyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone (Irg.369) were used.

[0047] Example 9: Preparation of photoresist material This embodiment is the same as Example 1, except that: 36 mg of photoinitiator Irg.819 (phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide) and 180 mg of photosensitizer 2-phenyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone (Irg.369) were used.

[0048] Example 10: Method for fabricating three-dimensional micro / nano metallic copper structures The fabrication steps for a three-dimensional micro / nano metallic copper structure are as follows: The multifunctional photoresist material prepared in Example 1 was dropped onto a surface-treated quartz substrate; Place the sample on the optical platform and use a femtosecond laser two-photon polymerization 3D printing device for 3D printing. First, locate the sample under a low-power objective lens, then switch to a high-power oil immersion lens (63×) and adjust the focus position until the sample is clear. Then turn on the laser, set the laser power and printing speed, and start laser printing. After the direct-write printing is completed, the sample is placed in acetone developer for 60 minutes to allow the unpolymerized or low-polymerized photoresist to fully dissolve in the developer, leaving only the polymerized three-dimensional porous organic structure. Figure 3 ), Figure 3 Figure (b) is Figure 3 The enlarged view of the middle (a) shows that the three-dimensional micro-nano structure is composed of densely arranged micro- and nano-pores; 4 mL of ethylenediamine was added to 20 mL of anhydrous ethanol and stirred with a glass rod to mix them thoroughly to form an amination solution. The developed three-dimensional micro-nano porous organic structure was then immersed in the amination solution and allowed to stand at room temperature for 60 minutes. After standing, the sample was removed and washed sequentially with ethanol and deionized water to obtain the surface-amine-functionalized porous micro-nano polymer structure. Next, the amination-treated micro / nanostructure was immersed in a 0.2 g / L palladium chloride solution and allowed to stand for adsorption for 15 minutes, forming a palladium ion-organic porous micro / nanostructure. The porous micro / nanostructure was then removed and immersed in a 10 g / L sodium borohydride solution for 10 minutes to chemically reduce the palladium ions in situ to palladium nanoparticles. This process of adsorption in palladium chloride solution and reduction in sodium borohydride solution was repeated three times. For the organic structure electroless plating treatment, firstly, weigh out 40 mg of anhydrous copper sulfate, 280 mg of sodium citrate dihydrate, 6 mg of nickel sulfate hexahydrate, 50 mg of ammonium chloride, 150 mg of sodium hypophosphite, 2 μL of 1.5 g / L malic acid, and 2 μL of 1 g / L polyethylene glycol-6000. Then, fully dissolve the weighed materials in 10 mL of deionized water, and adjust the pH to between 8 and 9 using sodium hydroxide solution to prepare the electroless copper plating solution. Place the treated sample in the plating solution and perform electroless plating in a water bath at 60°C for 35 min. Remove the sample and rinse it in deionized water for 5 min. Finally, a metal-organic composite three-dimensional micro / nano structure can be formed. The chemically plated metal-organic composite structure was placed in an annealing furnace. The furnace tube pressure was set to 400 torr and the air intake velocity to 150 sccm. The furnace was heated to 220°C at room temperature for 2 hours and held at 220°C for 2 hours. Then, the temperature was increased from 220°C to 550°C for 2 hours and held at 550°C for 2 hours. Next, the temperature was increased from 550°C to 620°C for 2 hours and held at 620°C for 2 hours. Finally, the furnace was allowed to cool naturally to room temperature. The structure, after low-temperature annealing, was subjected to high-temperature metallurgy. The pressure was set to 22 torr, and the gas mixture of hydrogen and argon (5% hydrogen) was introduced at a rate of 160 sccm. The temperature was increased from room temperature to 850°C at a rate of 3°C per minute, held at 850°C for 6 hours, and then slowly cooled to 600°C at a rate of 1°C per minute. Finally, it was allowed to cool naturally to room temperature, resulting in a three-dimensional micro / nano structure of metallic copper.

[0049] Example 11: Method for fabricating three-dimensional micro / nano metallic nickel structures The fabrication steps for preparing three-dimensional micro / nano metallic nickel structures are as follows: The multifunctional photoresist material prepared in Example 1 was dropped onto a surface-treated quartz substrate; Place the sample on the optical platform and use a femtosecond laser two-photon polymerization 3D printing device for 3D printing. First, locate the sample under a low-power objective lens, then switch to a high-power oil immersion lens (63×) and adjust the focus position until the sample is clear. Then turn on the laser, set the laser power and printing speed, and start laser printing. After the direct-write printing is completed, the sample is placed in acetone developer for 10 minutes to allow the unpolymerized or low-polymerized photoresist to fully dissolve in the developer, leaving only the polymerized three-dimensional porous organic structure. Figure 4 The first step is to take an actual photograph of the porous structure under a microscope. Because of the scattering of light by the porous structure, the whole structure appears to be opaque. 4 mL of ethylenediamine was added to 20 mL of anhydrous ethanol and stirred with a glass rod to mix them thoroughly to form an amination solution. The developed three-dimensional micro-nano porous organic structure was then immersed in the amination solution and allowed to stand at room temperature for 60 minutes. After standing, the sample was removed and washed sequentially with ethanol and deionized water to obtain the surface-amine-functionalized porous micro-nano polymer structure. Next, the amination-treated micro / nanostructure was immersed in a 0.2 g / L palladium chloride solution and allowed to stand for adsorption for 15 minutes, forming a palladium ion-organic porous micro / nanostructure. The porous micro / nanostructure was then removed and immersed in a 10 g / L potassium borohydride solution for 10 minutes to chemically reduce the palladium ions in situ to palladium nanoparticles. The above steps of adsorption in palladium chloride solution and reduction in sodium borohydride solution were repeated three times. Figure 4 Step two is an actual photograph under a microscope after chemical adsorption and reduction. The porous structure is enriched with a large number of nanoparticles, and the entire three-dimensional structure appears black. For the organic structure electroless plating treatment, firstly, weigh out 50 mg of nickel sulfate hexahydrate, 20 mg of sodium citrate dihydrate, 50 mg of ammonium chloride, 50 mg of sodium hypophosphite, and 10 μL of 0.15 g / L sodium dodecyl sulfate. Then, thoroughly dissolve these materials in 10 mL of deionized water, and adjust the pH to between 8 and 9 using sodium hydroxide solution to prepare the electroless nickel plating solution. Place the treated sample in the plating solution and perform electroless plating in a water bath at 60°C for 12 minutes. Afterward, remove the sample and rinse it in deionized water for 5 minutes. Finally, a metal-organic composite three-dimensional micro / nano structure can be formed. Figure 4 Step three is an actual photograph taken under a microscope, showing that the three-dimensional structure exhibits a certain metallic color after chemical plating; The chemically plated metal-organic composite structure was placed in an annealing furnace. The furnace tube pressure was set to 400 torr and the air intake velocity to 150 sccm. The furnace was heated to 220°C at room temperature for 2 hours and held at 220°C for 2 hours. Then, the temperature was increased from 220°C to 550°C for 2 hours and held at 550°C for 2 hours. Next, the temperature was increased from 550°C to 620°C for 2 hours and held at 620°C for 2 hours. Finally, the furnace was allowed to cool naturally to room temperature. The structure, after low-temperature annealing, underwent high-temperature metallurgy. A pressure of 22 torr was set, and a hydrogen-argon mixture (5% hydrogen) was introduced at a rate of 160 sccm. The temperature was increased from room temperature to 880°C at a rate of 1°C per minute, held at 880°C for 6 hours, and then slowly cooled to 600°C at a rate of 1°C per minute. Finally, it was allowed to cool naturally to room temperature, resulting in a three-dimensional micro / nano structure of metallic nickel. Figure 4Step four involves taking microscopic images of the nickel metal after high-temperature reduction and metallurgy, revealing its bright metallic luster. The final result is a scanning electron microscope (SEM) image of the three-dimensional micro / nano structure of the nickel metal, as shown below. Figure 5 The X-ray energy spectrum results of the constituent elements are shown in the figure below. Figure 6 As shown.

[0050] Example 12: Method for fabricating three-dimensional micro / nano metallic silver structures The preparation steps for fabricating three-dimensional micro / nano metallic silver structures are as follows: Take 1 mL of pentaerythritol triacrylate and 0.7 mL of acrylic acid, and stir until they are evenly mixed. Then weigh 34 mg of photoinitiator Irg.819 (phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide) and 34 mg of photosensitizer 2-phenyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone (Irg.369), and add them to the above-mentioned evenly mixed precursor. Sonicate for 15 minutes until the photoinitiator and photosensitizer are completely dissolved. Next, measure 0.7 mL of dodecyl acetate and 0.7 mL of octadecyl acetate as mixed pore-forming agents and add them to the above-mentioned photoresist precursor. Continue stirring until evenly mixed to obtain a transparent liquid multifunctional photoresist material with photocuring ability, ability to generate porous structures, and metal ion chelating ability. The pre-prepared multifunctional photoresist material is dropped onto a surface-treated quartz substrate. Place the sample on the optical platform and use a femtosecond laser two-photon polymerization 3D printing device for 3D printing. First, locate the sample under a low-power objective lens, then switch to a high-power oil immersion lens (63×) and adjust the focus position until the sample is clear. Then turn on the laser, set the laser power and printing speed, and start laser printing. After the direct-write printing is completed, the sample is placed in acetone developer for 30 minutes to allow the unpolymerized or low-polymerized photoresist to fully dissolve in the developer, leaving only the polymerized three-dimensional porous organic structure. 4 mL of ethylenediamine was added to 20 mL of anhydrous ethanol and stirred with a glass rod to mix them thoroughly to form an amination solution. The developed three-dimensional micro-nano porous organic structure was then immersed in the amination solution and allowed to stand at room temperature for 60 minutes. After standing, the sample was removed and washed sequentially with ethanol and deionized water to obtain the surface-amine-functionalized porous micro-nano polymer structure. Next, the amination-treated micro / nanostructure was immersed in a 1 g / L silver nitrate solution and allowed to stand for adsorption for 15 minutes, forming a silver ion-organic porous micro / nanostructure. The porous micro / nanostructure was then removed and immersed in a 10 g / L sodium borohydride solution for 10 minutes to chemically reduce the silver ions in situ to silver nanoparticles. This process of adsorption in silver nitrate solution and reduction in sodium borohydride solution was repeated four times. For the organic structure electroless plating treatment, first weigh 10 mg of silver nitrate, 50 mg of potassium sodium tartrate, and 20 μL of ammonia solution with a pH between 4 and 5. Then, fully dissolve the weighed materials in 1 mL of deionized water to prepare an electroless silver plating solution. Place the treated sample in the plating solution and perform electroless plating at 25°C for 15 min. After that, remove the sample and place it in deionized water for 5 min to clean it. Finally, a metal-organic composite three-dimensional micro-nano structure can be formed. The chemically plated metal-organic composite structure is placed in an annealing furnace. The furnace tube pressure is set to 400 torr, the air intake velocity is 150 sccm, and the temperature is increased to 220°C at room temperature for 2 hours. The temperature is then held at 220°C for 2 hours, then increased to 550°C for 2 hours, and held at 550°C for 2 hours. The temperature is then increased to 600°C for 2 hours, and held at 600°C for 2 hours. Finally, the structure is allowed to cool naturally to room temperature to obtain a three-dimensional micro / nano structure of metallic silver.

[0051] Example 13: Method for fabricating three-dimensional micro / nano copper-nickel alloy structures The preparation steps for fabricating three-dimensional micro / nano-micro copper-nickel alloy structures are as follows: Take 1 mL of pentaerythritol triacrylate and 0.8 mL of 1-vinylimidazole, and stir until they are evenly mixed. Then weigh 36 mg of photoinitiator Irg.819 (phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide) and 36 mg of photosensitizer 2-phenyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone (Irg.369), and add them to the above-mentioned evenly mixed precursor. Sonicate for 15 minutes until the photoinitiator and photosensitizer are completely dissolved. Next, measure 0.6 mL of dodecyl acetate and 0.6 mL of octadecyl acetate as mixed pore-forming agents and add them to the above-mentioned photoresist precursor. Continue stirring until evenly mixed to obtain a transparent liquid multifunctional photoresist material with photocuring ability, ability to generate porous structures, and metal ion chelating ability. The pre-prepared multifunctional photoresist material is dropped onto a surface-treated quartz substrate. Place the sample on the optical platform and use a femtosecond laser two-photon polymerization 3D printing device for 3D printing. First, locate the sample under a low-power objective lens, then switch to a high-power oil immersion lens (63×) and adjust the focus position until the sample is clear. Then turn on the laser, set the laser power and printing speed, and start laser printing. After the direct-write printing is completed, the sample is placed in acetone developer for 90 minutes to allow the unpolymerized or low-polymerized photoresist to fully dissolve in the developer, leaving only the polymerized three-dimensional porous organic structure. 4 mL of ethylenediamine was added to 20 mL of anhydrous ethanol and stirred with a glass rod to mix them thoroughly to form an amination solution. The developed three-dimensional micro-nano porous organic structure was then immersed in the amination solution and allowed to stand at room temperature for 60 minutes. After standing, the sample was removed and washed sequentially with ethanol and deionized water to obtain the surface-amine-functionalized porous micro-nano polymer structure. Next, the amination-treated micro / nanostructure was immersed in a 0.2 g / L palladium chloride solution and allowed to stand for adsorption for 15 minutes, forming a palladium ion-organic porous micro / nanostructure. The porous micro / nanostructure was then removed and immersed in a 10 g / L sodium borohydride solution for 10 minutes to chemically reduce the palladium ions in situ to palladium nanoparticles. This process of adsorption in palladium chloride solution and reduction in sodium borohydride solution was repeated three times. For the organic structure electroless plating treatment, firstly, weigh out 100 mg of anhydrous copper sulfate, 50 mg of nickel sulfate hexahydrate, 240 mg of sodium citrate dihydrate, 300 mg of sodium hypophosphite, and 300 mg of boric acid. Then, fully dissolve the weighed materials in 10 mL of deionized water and adjust the pH to between 8 and 9 using sodium hydroxide solution to prepare an electroless copper-nickel plating solution. Place the treated sample in the plating solution and perform electroless plating in a water bath at 60°C for 30 min. Remove the sample and rinse it in deionized water for 5 min. Finally, a metal-organic composite three-dimensional micro / nano structure can be formed. The chemically plated metal-organic composite structure was placed in an annealing furnace. The furnace tube pressure was set to 400 torr and the air intake velocity to 150 sccm. The furnace was heated to 220°C at room temperature for 2 hours and held at 220°C for 2 hours. Then, the temperature was increased from 220°C to 550°C for 2 hours and held at 550°C for 2 hours. Next, the temperature was increased from 550°C to 620°C for 2 hours and held at 620°C for 2 hours. Finally, the furnace was allowed to cool naturally to room temperature. The structure, after low-temperature annealing, was subjected to high-temperature metallurgy. The pressure was set to 22 torr, and the gas mixture of hydrogen and argon (5% hydrogen) was introduced at a rate of 160 sccm. The temperature was increased from room temperature to 880°C at a rate of 10°C per minute, held at 880°C for 6 hours, and then slowly cooled to 600°C at a rate of 30°C per minute. Finally, it was allowed to cool naturally to room temperature, resulting in a three-dimensional micro / nano structure of metallic copper-nickel.

[0052] Example 14: Method for fabricating three-dimensional micro / nano metallic pentagonal alloy structures of iron-cobalt-nickel-cerium-lanthanum The preparation steps for the fabrication of a three-dimensional micro / nano metallic pentagonal alloy structure of iron-cobalt-nickel-cerium-lanthanum are as follows: Take 1 mL of pentaerythritol triacrylate and 0.7 mL of acrylic acid, and stir until they are evenly mixed. Then weigh 34 mg of photoinitiator Irg.819 (phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide) and 34 mg of photosensitizer 2-phenyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone (Irg.369), and add them to the above-mentioned evenly mixed precursor. Sonicate for 15 minutes until the photoinitiator and photosensitizer are completely dissolved. Next, measure 0.7 mL of dodecyl acetate and 0.7 mL of octadecyl acetate as mixed pore-forming agents and add them to the above-mentioned photoresist precursor. Continue stirring until evenly mixed to obtain a transparent liquid multifunctional photoresist material with photocuring ability, ability to generate porous structures, and metal ion chelating ability. The pre-prepared multifunctional photoresist material is dropped onto a surface-treated quartz substrate. Place the sample on the optical platform and use a femtosecond laser two-photon polymerization 3D printing device for 3D printing. First, locate the sample under a low-power objective lens, then switch to a high-power oil immersion lens (63×) and adjust the focus position until the sample is clear. Then turn on the laser, set the laser power and printing speed, and start laser printing. After the direct-write printing is completed, the sample is placed in acetone developer for 120 minutes to allow the unpolymerized or low-polymerized photoresist to fully dissolve in the developer, leaving only the polymerized three-dimensional porous organic structure. 4 mL of ethylenediamine was added to 20 mL of anhydrous ethanol and stirred with a glass rod to mix them thoroughly to form an amination solution. The developed three-dimensional micro-nano porous organic structure was then immersed in the amination solution and allowed to stand at room temperature for 60 minutes. After standing, the sample was removed and washed sequentially with ethanol and deionized water to obtain the surface-amine-functionalized porous micro-nano polymer structure. Next, the amination-treated micro / nanostructure was immersed in a 0.2 g / L palladium chloride solution and allowed to stand for adsorption for 15 minutes, forming a palladium ion-organic porous micro / nanostructure. The porous micro / nanostructure was then removed and immersed in a 10 g / L sodium borohydride solution for 10 minutes to chemically reduce the palladium ions in situ to palladium nanoparticles. This process of adsorption in palladium chloride solution and reduction in sodium borohydride solution was repeated three times. For the organic structure electroless plating treatment, firstly, weigh out 250 mg of nickel sulfate hexahydrate, 150 mg of cobalt sulfate hexahydrate, 100 mg of ferrous chloride, 14 mg of cerium nitrate, 14 mg of lanthanum nitrate, 400 mg of sodium citrate dihydrate, 300 mg of sodium hypophosphite, 120 mg of malic acid, and 450 mg of ammonium chloride. Then, fully dissolve the weighed materials in 10 mL of deionized water, and adjust the pH to between 10 and 11 using sodium hydroxide solution to prepare the electroless plating solution for a five-element alloy. Place the treated sample in the plating solution and perform electroless plating at 80°C for 60 min. After that, remove the sample and rinse it in deionized water for 5 min. Finally, a metal-organic composite three-dimensional micro / nano structure can be formed. The chemically plated metal-organic composite structure was placed in an annealing furnace. The furnace tube pressure was set to 400 torr and the air intake speed to 150 sccm. The temperature was increased to 220°C at room temperature for 2 hours and held at 220°C for 2 hours. Then, the temperature was increased from 220°C to 550°C for 2 hours and held at 550°C for 2 hours. Then, the temperature was increased from 550°C to 620°C for 2 hours and held at 620°C for 2 hours. Finally, the temperature was allowed to cool naturally to room temperature to obtain the three-dimensional micro-nano structure of the pentagonal alloy of iron, cobalt, nickel, cerium and lanthanum. The structure, after low-temperature annealing, was subjected to high-temperature metallurgy. A pressure of 22 torr was set, and a hydrogen-argon mixture (5% hydrogen) was introduced at a rate of 160 sccm. The temperature was increased from room temperature to 1100℃ at a rate of 20℃ per minute, held at 1100℃ for 6 hours, and then slowly cooled to 600℃ at a rate of 50℃ per minute, followed by natural cooling to room temperature. This resulted in a three-dimensional micro / nano structure of a pentagonal alloy of iron, cobalt, nickel, cerium, and lanthanum. The X-ray energy dispersive spectroscopy (EDS) results of its constituent elements are shown in the figure below. Figure 7 As shown.

[0053] Comparative Example 1: Preparation method similar to femtosecond laser direct printing of metal ion-organic resin composite materials Andrey Vyatskikh of the Department of Engineering and Applied Sciences at Caltech proposed a femtosecond laser-based direct printing method for metal-ion-organic resin composites (Additive manufacturing of 3D nano-architected metals, Nature Communications volume 9, Article number: 593 (2018)). This method utilizes a ligand exchange reaction between nickel alkyd and acrylic acid to synthesize nickel acrylate, which is then combined with another acrylic monomer, pentaerythritol triacrylate, and the photoinitiator 7-diethylamino-3-aminocoumarin. Femtosecond laser 3D printing is then employed, followed by pyrolysis of the independent cross-linked polymer nanostructure to volatilize the organic components. This process produces a replica of the original 3D structure with a linear shrinkage rate of 80%.

[0054] Comparative Example 2: Three-dimensional micro / nano metal fabrication method based on photoresist materials lacking photosensitizers 1. Take 1 mL of pentaerythritol triacrylate and 0.8 mL of 1-vinylimidazole, and stir until they are evenly mixed. Then weigh 36 mg of photoinitiator Irg.819 (phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide) and add it to the above-mentioned evenly mixed precursor. Do not add photosensitizer. Then sonicate for 15 minutes until the photoinitiator is completely dissolved. Next, measure 0.6 mL of dodecyl acetate and 0.6 mL of octadecyl acetate as mixed pore-forming agents and add them to the above-mentioned photoresist precursor. Continue stirring until evenly mixed to obtain a transparent liquid material.

[0055] 2. The pre-prepared multifunctional photoresist material is dropped onto a surface-treated quartz substrate; 3. Place the sample on the optical platform and use the femtosecond laser two-photon polymerization 3D printing device for 3D printing. First, locate the sample under the low magnification objective lens, then switch to the high magnification oil immersion lens (63×) and adjust the focus position until the sample is clear. Then turn on the laser, set the laser power and printing speed, and start laser printing. 4. Due to the lack of photosensitizer, the prepared photoresist material is difficult to polymerize during laser printing. Even with increased laser exposure power density, it is impossible to print the pre-designed three-dimensional micro-nano organic structure. Therefore, it does not meet the three-dimensional template structure requirements of subsequent process steps and cannot obtain the final metal micro-nano structure.

[0056] Comparative Example 3: Three-dimensional micro / nano metal fabrication method based on photoresist materials lacking pore-forming agents 1. Take 1 mL of pentaerythritol triacrylate and 0.8 mL of 1-vinylimidazole, stir until they are evenly mixed, then weigh 36 mg of photoinitiator Irg.819 (phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide) and 36 mg of photosensitizer 2-phenyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone (Irg.369), add them to the above-mentioned evenly mixed precursor, and sonicate for 15 minutes until the photoinitiator and photosensitizer are completely dissolved to obtain a transparent liquid multifunctional photoresist material with photocuring ability and metal ion chelating ability, but it cannot produce a porous structure.

[0057] 2. The pre-prepared multifunctional photoresist material is dropped onto a surface-treated quartz substrate; 3. Place the sample on the optical platform and use the femtosecond laser two-photon polymerization 3D printing device for 3D printing. First, locate the sample under the low magnification objective lens, then switch to the high magnification oil immersion lens (63×) and adjust the focus position until the sample is clear. Then turn on the laser, set the laser power and printing speed, and start laser printing. 4. Place the sample after direct writing printing in acetone developer for 10 minutes to allow the unpolymerized or low-polymerized photoresist to fully dissolve in the developer. 5. Measure 4 mL of ethylenediamine and add it to 20 mL of anhydrous ethanol. Stir with a glass rod to mix the two thoroughly to form an amination solution. Then, immerse the developed three-dimensional micro / nano organic structure in the above amination solution and let it stand at room temperature for 60 minutes. After standing, take out the sample and wash it sequentially with ethanol and deionized water to obtain the surface-amine-functionalized micro / nano polymer structure. 6. Next, the amination-treated micro / nanostructure was immersed in a 0.2 g / L palladium chloride solution and allowed to stand for adsorption for 15 minutes to form a palladium ion-organic micro / nanostructure. The micro / nanostructure was then removed and immersed in a 10 g / L potassium borohydride solution for 10 minutes to chemically reduce the palladium ions in situ to palladium nanoparticles. The above steps of adsorption in palladium chloride solution and reduction in sodium borohydride solution were repeated three times. 7. Organic structure electroless plating treatment: First, weigh out 50 mg of nickel sulfate hexahydrate, 20 mg of sodium citrate dihydrate, 50 mg of ammonium chloride, 50 mg of sodium hypophosphite, and 10 μL of 0.15 g / L sodium dodecyl sulfate. Then, fully dissolve the weighed materials in 10 mL of deionized water and adjust the pH to between 8 and 9 using sodium hydroxide solution to prepare an electroless nickel plating solution. Place the treated sample in the plating solution and perform electroless plating in a water bath at 60°C for 12 min. Remove the sample and rinse it in deionized water for 5 min. Finally, a metal-organic composite three-dimensional micro / nano structure can be formed. 8. Place the chemically plated metal-organic composite structure into an annealing furnace. Set the furnace tube pressure to 400 torr and the air intake speed to 150 sccm. Heat the furnace to 220°C at room temperature for 2 hours and hold at 220°C for 2 hours. Then, raise the temperature from 220°C to 550°C for 2 hours and hold at 550°C for 2 hours. Next, raise the temperature from 550°C to 620°C for 2 hours and hold at 620°C for 2 hours. Finally, allow the furnace to cool naturally to room temperature. 9. The structure after low-temperature annealing was subjected to high-temperature metallurgy. The pressure was set to 22 torr, and the gas flow rate of the hydrogen and argon mixture (5% hydrogen) was 160 sccm. The temperature was increased from room temperature to 880℃ at a rate of 1℃ per minute. The temperature was held at 880℃ for 6 hours, and then slowly cooled to 600℃ at a rate of 1℃ per minute. Finally, it was allowed to cool naturally to room temperature, and the three-dimensional micro-nano structure of metallic nickel was obtained.

[0058] Since no pore-forming agent is added, a metal shell of hundreds of nanometers thickness will be uniformly deposited on the outside of the organic micro-nano structure during the subsequent chemical plating process. Under high-temperature annealing and metallurgical post-treatment, the volatilization of organic elements will still lead to a large structural shrinkage, with a linear shrinkage rate of more than 50%.

[0059] Comparative Example 4: A method for preparing three-dimensional micro / nano metals without a chemical plating step. The preparation steps are as follows: 1. The multifunctional photoresist material prepared in Example 1 is dropped onto a surface-treated quartz substrate; 2. Place the sample on the optical platform and use the femtosecond laser two-photon polymerization 3D printing device for 3D printing. First, locate the sample under the low magnification objective lens, then switch to the high magnification oil immersion lens (63×) and adjust the focus position until the sample is clear. Then turn on the laser, set the laser power and printing speed, and start laser printing. 3. Place the sample after direct writing printing in acetone developer for 10 minutes to allow the unpolymerized or low-polymerized photoresist to fully dissolve in the developer, leaving only the polymerized three-dimensional porous organic structure. 4. Measure 4 mL of ethylenediamine and add it to 20 mL of anhydrous ethanol. Stir with a glass rod to mix the two thoroughly to form an amination solution. Then, immerse the developed three-dimensional micro-nano porous organic structure in the above amination solution and let it stand at room temperature for 60 minutes. After standing, take out the sample and wash it in sequence with ethanol and deionized water to obtain the surface amino-functionalized porous micro-nano polymer structure. 5. Next, the amination-treated micro / nanostructure was immersed in a 0.2 g / L palladium chloride solution and allowed to stand for adsorption for 15 minutes, forming a palladium ion-organic porous micro / nanostructure. The porous micro / nanostructure was then removed and immersed in a 10 g / L potassium borohydride solution for 10 minutes to chemically reduce the palladium ions in situ to palladium nanoparticles. The above steps of adsorption in palladium chloride solution and reduction in sodium borohydride solution were repeated three times. 6. Place the above-treated composite structure into an annealing furnace, set the furnace tube pressure to 400 torr, the air intake velocity to 150 sccm, heat to 220℃ at room temperature for 2 hours, hold at 220℃ for 2 hours, then raise the temperature from 220℃ to 550℃ for 2 hours, hold at 550℃ for 2 hours, then continue to raise the temperature from 550℃ to 620℃ for 2 hours, then hold at 620℃ for 2 hours, and finally allow it to cool naturally to room temperature. 7. The structure after low-temperature annealing was subjected to high-temperature metallurgy. A pressure of 22 torr was set, and a hydrogen-argon mixture (5% hydrogen) was introduced at a rate of 160 sccm. The temperature was increased from room temperature to 880℃ at a rate of 1℃ per minute, held at 880℃ for 6 hours, and then slowly cooled to 600℃ at a rate of 1℃ per minute, followed by natural cooling to room temperature. Due to the lack of a chemical plating step, nearly 40% of the volume space in the organic porous structure is metal-free, and the metallic phase in the organic structure only originates from the adsorption of palladium by imidazole groups. The majority of the structure remains organic. Therefore, after high-temperature annealing and reduction, the linear shrinkage rate of the structure reaches over 95%, making it impossible to guarantee metal formation.

[0060] The shrinkage rate data of the materials prepared in Examples 10-14 and Comparative Examples 1-4 are shown in Table 1: Table 1. Shrinkage data of materials prepared in Examples 10-14 and Comparative Examples 1-4

[0061] Note: The range of recovery rates is due to consideration of errors and process condition stability.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing micro / nano three-dimensional metal and alloy structures, characterized in that, Includes the following steps: S1, Preparation of photoresist material; S2, using laser two-photon polymerization 3D printing method to form photoresist material, forming a 3D organic micro-nano structure with rich and uniform nanopores, and then developing it; S3, after development, the three-dimensional micro-nano porous organic structure is subjected to amination treatment and metal seed source is introduced to obtain a 3D organic micro-nano structure enriched with metal nanoparticles. S4. The 3D organic micro-nano structure from step S3 is immersed in a chemical plating solution for chemical plating treatment to obtain a metal-organic composite three-dimensional micro-nano structure. S5, the target three-dimensional metal micro / nano structure sample is obtained through low-temperature annealing and / or high-temperature metallurgical processes.

2. The preparation method according to claim 1, characterized in that, In step S1, the photoresist material contains a pore-forming agent, which contains a mixture of dodecyl acetate and octadecyl acetate or a mixture of 1-decyl alcohol and cyclohexanol.

3. The preparation method according to claim 1, characterized in that, In step S1, the photoresist material further includes photosensitive resin monomers, organic functional monomers, initiators, and photosensitizers.

4. The preparation method according to claim 3, characterized in that, In step S1, the organic functional monomer comprises any one of 1-vinylimidazolium, methacrylic acid, acrylic acid, vinylpyrrolidone, vinylpyrimidine, acrylamide, and vinylpyrazine; the photosensitizer resin monomer comprises one or more of unsaturated acrylate, polyurethane, and epoxy resin.

5. The preparation method according to claim 3, characterized in that, In step S1, the photoresist material further includes a pore-forming agent, wherein the ratio of photosensitive resin monomer: pore-forming agent: organic functional monomer is 10: (1~20): (0.1~20).

6. The preparation method according to claim 3, characterized in that, In step S1, the combined amount of the photoinitiator and photosensitizer is 0.1% to 10% of the combined amount of the photosensitive resin monomer and the organic functional monomer, wherein the mass ratio of the photoinitiator to the photosensitizer is 1:0.1 to 5.

7. The preparation method according to claim 1, characterized in that, In step S3, the amination treatment solution is a mixed solution of ethanol and polyamine molecules with a volume ratio of 1:0.1~1, and the amination treatment time is 1~12 h; the metal seed source introduction process includes immersing the amination-treated micro-nano structure in a metal ion solution for 15~30 minutes to form a metal ion-organic porous micro-nano structure, and then using a reducing agent to reduce the metal ions to metal particles as a seed source.

8. The preparation method according to claim 7, characterized in that, The concentration of the metal ion solution used in the metal seed source introduction process is ≥0.1mol / L, and the reducing agent includes one or more of sodium borohydride, potassium borohydride, hydrazine and their derivatives.

9. The preparation method according to claim 1, characterized in that, In step S4, the temperature of the electroless plating is 20~80℃ and the pH is 4~11; in step S2, the development time is 10~120 min.

10. The preparation method according to claim 1, characterized in that, In step S5, the low-temperature annealing process includes gradually heating from room temperature to 550~650℃ and then naturally cooling; the high-temperature metallurgical process includes heating from room temperature to 650~1100℃ in a mixed atmosphere of hydrogen and argon, holding at that temperature, and then cooling down to 600℃ and then naturally cooling; the heating rate in the high-temperature metallurgical process is between 1~20℃ / min, and the cooling rate is between 1~50℃ / min.

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