Micro-nano transparent glass three-dimensional structure and preparation method and application thereof

Abstract

The invention provides a micro-nano transparent glass three-dimensional structure and a preparation method and application thereof. According to the preparation method, photoresponse ligand modified silicon dioxide nanoparticles are taken as raw materials, in the presence of a photoinitiator, no extra photoresponse monomer or crosslinking agent needs to be added in the subsequent laser processing process, photocrosslinking can be directly realized, and the nanoparticles in the obtained micro-nano three-dimensional glass green body are in a tight crosslinking state. Meanwhile, based on the state, the obtained micro-nano three-dimensional glass green body is sintered at the low temperature of not more than 700 DEG C, so that a glass network structure can be formed among nano particles, and finally, a transparent micro-nano glass three-dimensional structure is obtained. Tests show that the shrinkage rate of the three-dimensional structure of the micro-nano transparent glass provided by the invention is lower than 5%. Therefore, low-temperature sintering is achieved, meanwhile, the micro-nano transparent glass three-dimensional structure with the low shrinkage rate is obtained, and the problem that in the prior art, low-temperature sintering and low-shrinkage-rate micro-nano transparent glass cannot be achieved at the same time is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of glass, and particularly relates to a three-dimensional structure of micro-nano transparent glass, a preparation method thereof, and an application thereof. Background Art

[0002] Due to its excellent optical transparency, mechanical properties, thermal stability, chemical stability and other characteristics, glass is widely used in the fields of optics, biology, medicine and so on. Traditional glass forming methods are mainly based on glass blowing and die pressing, and it is difficult to manufacture complex three-dimensional (3D) structures.

[0003] At present, the forming technologies of glass three-dimensional structures are mainly divided into two categories: direct glass 3D printing technology and indirect glass 3D printing technology. Among them, direct glass 3D printing technology mainly includes Selective Laser Melting (SLM), Directed Energy Deposition (DED) and Fused Deposition Modeling (FDM). The above methods generate a temperature capable of melting silica (>1600 °C) through a super strong energy source to manufacture complex glass three-dimensional structures. However, the manufacturing temperature is too high and the processing accuracy is often at the millimeter level, and high-precision glass devices cannot be manufactured. Indirect glass 3D printing technology mainly includes Direct Ink Write (DIW), Stereo lithography Apparatus (SLA), Digital Light Processing (DLP) and Computed Axial lithography (CAL). The above methods first print a three-dimensional glass green body, and then remove the organic components in the structure through debinding and sintering, and finally obtain transparent silica glass. During this process, a certain amount of shrinkage occurs in the structure. However, the manufacturing resolution of the above methods is usually above dozens of microns, which cannot meet the requirements of high resolution and high precision of micro-nano glass devices, and seriously hinders the application of glass materials in the field of micro-nano engineering, especially in the field of micro-nano optical information.

[0004] Based on this, scholars have studied the preparation of three-dimensional micro-nano glass structures. For example, the research group of Xiewen Wen at the Hong Kong Polytechnic University used silica nanoparticles modified with polyethylene glycol and successfully achieved the printing of glass microstructures with a characteristic size of 170 nanometers after sintering at 1100 °C. The structure shrinkage rate was 14%, and the transparency exceeded 90%. However, the high sintering temperature (1100 °C) makes it difficult to integrate the manufacturing process of this three-dimensional glass structure with other heat-sensitive devices, restricting its application. The research group of J. Bauer at the Karlsruhe Institute of Technology in Germany used cage-shaped polyhedral oligomeric silsesquioxane to achieve the printing of three-dimensional glass structures with a characteristic size of 97 nanometers after low-temperature heat treatment. The structure shrinkage rate was 42%, and the transparency exceeded 95%. However, the large shrinkage (>20%) will cause strain mismatch between the structure and the substrate, easily resulting in the deformation of the three-dimensional structure. Although this defect can be offset by printing an additional sacrificial substrate, it increases the printing time and reduces the manufacturing efficiency. Therefore, the current technology still cannot achieve the manufacturing of three-dimensional micro-nano transparent glass structures with both low sintering temperature and low shrinkage rate. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a three-dimensional micro-nano transparent glass structure, its preparation method and application. The preparation method has a low sintering temperature, and the shrinkage rate of the prepared three-dimensional micro-nano transparent glass structure is low, less than 5%.

[0006] To achieve this purpose, the present invention adopts the following technical solutions: In the first aspect, the present invention provides a preparation method for a three-dimensional micro-nano transparent glass structure, including the following steps: S1: Mix a solution of silica nanoparticles modified with a photo-responsive ligand and a photoinitiator, and then dry it to obtain a glass precursor photoresist; The photo-responsive ligand includes any one or more of methacrylic acid, methacryloxytrimethoxysilane, or styryl triethoxysilane; S2: Perform laser processing on the glass slide carrying the glass precursor photoresist to obtain a green body of three-dimensional micro-nano glass. After sintering and cooling, a three-dimensional micro-nano transparent glass structure is obtained; The temperature of the sintering does not exceed 700 °C.

[0007] Preferably, the laser processing is femtosecond laser processing.

[0008] Preferably, the exposure time of the laser in the laser processing is 400 - 1000 µs, and the power is 11 - 29 mW.

[0009] Preferably, the sintering is carried out according to the following procedure: Heat up to 160 - 240 °C and keep warm for 2 - 3 h; Heat up to 400 - 450 °C and keep the temperature for 3 - 4 h; Heat up to 650 - 700 °C and keep the temperature for 5 - 10 h.

[0010] Preferably, the heating rate during sintering is 1 - 3 °C / min.

[0011] Preferably, the mass fraction of the solute in the solution of the silica nanoparticles modified with the photo-responsive ligand is 30 - 60%.

[0012] Preferably, the particle size of the silica nanoparticles is 15 - 30 nm.

[0013] Preferably, the solvent in the solution of the silica nanoparticles modified with the photo-responsive ligand includes any one or more of propylene glycol methyl ether, ethanol, isopropanol, n-butanol, ethylene glycol or propylene glycol.

[0014] Preferably, the photoinitiator includes any one or more of tetraethyl Michler's ketone, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide or 7-diethylamino-3-thienoylcoumarin.

[0015] Preferably, the mass ratio of the photo-responsive ligand to the silica nanoparticles is 22:78 - 18:82.

[0016] Preferably, the mass ratio of the silica nanoparticles modified with the photo-responsive ligand to the photoinitiator is 20:(0.5 - 1.5).

[0017] Preferably, mix until the photoinitiator is completely dissolved.

[0018] Preferably, the drying temperature is 50 - 80 °C and the time is 10 - 30 h.

[0019] Preferably, after the micro-nano three-dimensional glass green body is developed, sintering is carried out.

[0020] Preferably, the development is carried out in an ethanol solution.

[0021] In the second aspect, the present invention provides a micro-nano transparent glass three-dimensional structure prepared by the above preparation method, and the shrinkage rate of the micro-nano transparent glass three-dimensional structure is less than 5%.

[0022] In the third aspect, the present invention provides an application of the micro-nano transparent glass three-dimensional structure prepared by the above preparation method in the preparation of optical fiber integrated devices.

[0023] Compared with the prior art, the beneficial effects of the present invention are: The present invention provides a method for preparing a micro-nano transparent glass three-dimensional structure. The method uses silica nanoparticles modified with a photo-responsive ligand as raw materials. In the presence of a photo-initiator, no additional photo-responsive monomer or cross-linking agent needs to be added during the subsequent laser processing, and photo-crosslinking can be directly achieved. The nanoparticles in the obtained micro-nano three-dimensional glass green body are in a tightly cross-linked state. At the same time, based on this state, the obtained micro-nano three-dimensional glass green body is sintered at a low temperature not exceeding 700 °C, so that a glass network structure can be formed between the nanoparticles, and finally a transparent micro-nano glass three-dimensional structure is obtained.

[0024] In the present invention, on the one hand, silica nanoparticles modified with a photo-responsive ligand are sintered at a low temperature, which is beneficial for the obtained micro-nano glass three-dimensional structure to be a porous structure; on the other hand, the photo-responsive ligand directly cross-links the silica nanoparticles, which is also beneficial for retaining some pore structures. Therefore, the micro-nano transparent glass three-dimensional structure prepared by the present invention has a porous structure, which helps to obtain a lower structural shrinkage rate. After testing, the shrinkage rate of the micro-nano transparent glass three-dimensional structure provided by the present invention is less than 5%.

[0025] In summary, the present invention not only realizes low-temperature sintering, but also obtains a micro-nano transparent glass three-dimensional structure with a low shrinkage rate, solving the problem in the prior art that it is impossible to have both. Moreover, the preparation method provided by the present invention has simple steps and low cost, which is beneficial for realizing industrial or industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic flow chart of obtaining the glass precursor photoresist of the present invention; Figure 2 It is a schematic flow chart of femtosecond laser two-photon polymerization processing; Figure 3 It is a schematic diagram of 6 different designed glass three-dimensional structure models; Figure 4 It is a schematic diagram of the femtosecond laser two-photon polymerization process of the micro-nano three-dimensional glass green body; Figure 5 It is a schematic flow chart of sintering the developed sample; Figure 6 It is an SEM image of 6 different prepared glass three-dimensional structures; Figure 7 It is a size comparison diagram of glass three-dimensional structures 1 to 4 before and after sintering under different views; Figure 8 It is an optical microscope image of structure 5; Figure 9 It is a surface roughness characterization result diagram of structure 6; Figure 9 In a, it is an SEM image of structure 6 used for testing,Figure 9 In which, b is the surface contour map obtained by using an atomic force microscope, Figure 9 In which, c is the contour map extracted from the position of the white line in b; Figure 10 is the Raman spectrum of Structure 6; Figure 11 is the transmission electron microscope (TEM) image of the thin slice extracted from Structure 6 by using focused ion beam cutting. Specific Embodiments

[0027] Next, in combination with the embodiments of the present invention, the technical solutions of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0028] Aiming at the problem that the prior art cannot achieve low-temperature sintering and at the same time obtain a three-dimensional structure of micro-nano transparent glass with a low shrinkage rate, the present invention provides a method for preparing a three-dimensional structure of micro-nano transparent glass, including the following steps: S1: After mixing the silica nanoparticle solution modified with a photo-responsive ligand and a photoinitiator, drying to obtain a glass precursor photoresist; S2: Laser processing the glass slide carrying the glass precursor photoresist to obtain a green body of micro-nano three-dimensional glass, and after sintering, cooling to obtain a three-dimensional structure of micro-nano transparent glass.

[0029] In the present invention, it is first necessary to synthesize a glass precursor photoresist. The glass precursor photoresist mainly consists of silica nanoparticles modified with a photo-responsive ligand and a photoinitiator. In some embodiments of the present invention, it is preferably to mix the silica nanoparticle solution modified with a photo-responsive ligand and a photoinitiator and then dry to obtain a glass precursor photoresist.

[0030] In the present invention, if the mass fraction of the solute in the solution of the photo-responsive ligand-modified silica nanoparticles is relatively high, it will increase the risk of nanoparticle aggregation and affect the preparation of the subsequent photoresist. Therefore, the present invention preferably uses a solution of photo-responsive ligand-modified silica nanoparticles with a solute mass fraction of 30% to 60%, such as 30%, 35%, 40%, 45%, 50%, 55% or 60%, etc. Among them, the solvent in the solution of the photo-responsive ligand-modified silica nanoparticles includes any one or more of propylene glycol methyl ether, ethanol, isopropanol, n-butanol, ethylene glycol or propylene glycol, preferably propylene glycol methyl ether; the photo-responsive ligand includes any one or more of methacrylic acid, methacryloxytrimethoxysilane or styryltriethoxysilane, preferably methacrylic acid, which can not only provide high cross-linking ability, but also rapidly form a cross-linked network under the action of a photoinitiator through its double bond; the particle size of the silica nanoparticles is preferably 10 to 30 nm, such as 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, etc., which can improve the manufacturing precision. In the present invention, the solution of the photo-responsive ligand-modified silica nanoparticles can be directly purchased or prepared according to the content well-known to those skilled in the art. Among them, the mass ratio of the photo-responsive ligand to the silica nanoparticles is 22:78 to 18:82, such as 18:82, 19:81, 20:80, 21:79 or 22:78, etc.

[0031] In some specific embodiments of the present invention, it is preferred to oscillate and mix the solution of the photo-responsive ligand-modified silica nanoparticles with a photoinitiator and ultrasonically treat it until the photoinitiator is completely dissolved to obtain a light yellow transparent solution. Among them, the photoinitiator includes any one or more of tetraethyl Michler's ketone, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide or 7-diethylamino-3-thiophenecarbonylcoumarin. The mass ratio of the photo-responsive ligand-modified silica nanoparticles to the photoinitiator is 20:(0.5 to 1.5), such as 20:0.5, 20:0.8, 20:1, 20:1.2 or 20:1.5, etc. Then, the light yellow transparent solution is placed in an oven and baked at 50 to 80 °C for 10 to 30 h, preferably baked at 60 to 75 °C for 10 to 25 h, and more preferably baked in an oven at 65 °C for 20 h to reduce the solvent content in the solution and obtain a dark yellow transparent solution, that is, the glass precursor photoresist.

[0032] It should be noted that in the present invention, the silica nanoparticles are modified with a photo-responsive ligand. In the subsequent processing, photo-crosslinking can be achieved without adding additional photo-polymerizable monomers or cross-linking agents, which has the advantages of few material components, simple preparation and low cost.

[0033] According to the present invention, after obtaining the glass precursor photoresist, it is preferably to use a pipette to take a part of the glass precursor photoresist and drop it on a glass slide to obtain a glass slide carrying the glass precursor photoresist, and then perform laser processing. Among them, the glass slide is preferably a quartz glass slide that can withstand a high temperature of nearly 1000 °C, and the specifications of the glass slide can be designed according to needs, such as a 2 cm × 2 cm × 200 μm glass slide.

[0034] In some embodiments of the present invention, it is preferred to heat the glass slide carrying the glass precursor photoresist on a hot plate at about 100 °C for 60 - 120 s, preferably 90 s, to remove most of the volatile solvents, and then perform laser processing.

[0035] In some embodiments of the present invention, the laser processing is femtosecond laser processing. The present invention does not particularly limit the technical means of femtosecond laser processing, and it can be operated according to the content well-known to those skilled in the art.

[0036] In some specific embodiments of the present invention, the schematic diagram of the processing optical path of the femtosecond laser processing is as Figure 2 shown. It is preferred to place the glass slide carrying the glass precursor photoresist (i.e., the sample) on the Z-direction nano piezostage in the direction of the oil immersion objective lens side. The femtosecond laser is emitted by a titanium sapphire laser, and after passing through a half-wave plate, a polarization beam splitter, and a beam expander, it is incident on the scanning galvanometer. The scanning galvanometer controls the reflection angle of the reflecting mirror, thereby achieving the deflection of the laser beam and completing the movement of the laser in the XY two-dimensional plane. After the laser exits from the scanning galvanometer, it enters the oil immersion objective lens (60×, 1.4 NA) through a 4f lens group and a reflecting mirror, and the laser beam is focused inside the glass precursor photoresist through the oil immersion objective lens. Manually coarsely adjust the Z-direction position of the sample so that the initial light spot is located at the interface between the quartz glass slide and the glass precursor photoresist. Subsequently, the three-dimensional structure model to be processed is imported into the processing software in sequence, and the laser exposure time is set to 400 - 1000 μs, such as 400 μs, 500 μs, 600 μs, 700 μs, 800 μs, 900 μs, or 1000 μs, etc.; the processing power of the laser is adjusted to 11 - 29 mW through an attenuation sheet, such as 11 mW, 13 mW, 15 mW, 17 mW, 20 mW, 23 mW, 25 mW, 27 mW, or 29 mW, etc.; finally, by combining the Z-direction movement of the nano piezostage and the X-direction and Y-direction scanning of the scanning galvanometer, the efficient processing of the micro-nano three-dimensional glass green body is realized. It should be noted that the above exposure time and processing power are the selections after screening and optimization in the present invention. If the exposure time is too short and the processing power is too low, the forming cannot be achieved; on the contrary, if it is too high, the structure will be too large and deviate from the design size.

[0037] In the present invention, during the above-mentioned femtosecond laser processing, even without adding additional photo-crosslinkable monomers or crosslinking agents, the presence of the photo-responsive ligands modified on the surface of the silica nanoparticles can achieve photopolymerization, enabling the nanoparticles to directly crosslink. Therefore, the silica nanoparticles modified with photo-responsive ligands in the glass precursor photoresist undergo direct photo-crosslinking under the action of femtosecond laser two-photon polymerization and ultimately form a three-dimensional structure according to the laser scanning trajectory.

[0038] Schematically, the femtosecond laser two-photon polymerization process of the micro-nano three-dimensional glass green body with tightly crosslinked nanoparticles is as Figure 4 shown.

[0039] According to the present invention, after obtaining the micro-nano three-dimensional glass green body, it is subjected to low-temperature sintering and then cooled to room temperature to obtain a micro-nano transparent glass three-dimensional structure.

[0040] In the present invention, the low-temperature sintering is preferably carried out in a muffle furnace, and the sintering temperature does not exceed 700 °C. Specifically, in some embodiments of the present invention, the sintering is carried out according to the following procedure: Heat up to 160 - 240 °C and hold for 2 - 3 h; Heat up to 400 - 450 °C and hold for 3 - 4 h; Heat up to 650 - 700 °C and hold for 5 - 10 h.

[0041] Exemplarily, it can be any one of the following procedures: Procedure 1: Heat up to 200 °C and hold for 2 h; Heat up to 400 °C and hold for 3 h; Heat up to 650 °C and hold for 5 h.

[0042] Procedure 2: Heat up to 180 °C and hold for 2.5 h; Heat up to 420 °C and hold for 3 h; Heat up to 680 °C and hold for 6 h.

[0043] Procedure 3: Heat up to 220 °C and hold for 3 h; Heat up to 450 °C and hold for 3 h; Heat up to 700 °C and hold for 8 h.

[0044] However, in the present invention, the sintering procedure is not limited to the above three procedures, and as long as the temperature and time set in the above sintering procedure are satisfied, it can be carried out.

[0045] During the above sintering process, the heating rate is 1-3 °C / min. For example, it can be 1 °C / min, 1.5 °C / min, 2 °C / min, 2.5 °C / min or 3 °C / min, etc. The heating rate generally cannot be too high or too low. If it is too low, it will lead to too long a structure preparation time and waste of energy. If it is too high, it will cause rapid combustion of the organic matter inside the structure and reduce the forming quality of the structure.

[0046] It should be noted that in the present invention, heating to 160-240 °C and holding for 2-3 h is to remove the residual solvent and moisture in the structure; heating to 400-450 °C and holding for 3-4 h is to remove the organic matter in the structure; finally, heating to 650-700 °C and holding for 5-10 h, and waiting for natural cooling to room temperature. During this process, a glass network structure is formed between the light-responsive ligand-modified silica nanoparticles, and finally a transparent micro-nano glass three-dimensional structure is obtained. At the same time, since the nanoparticles in the three-dimensional glass green body are in a tightly cross-linked state after the laser processing is completed, the nanoparticles are closely packed and arranged after the organic matter is removed. By setting a suitable heating curve and holding time, after sintering at a lower temperature (650-700 °C), a transparent, low-structure shrinkage rate and high-fidelity micro-nano glass three-dimensional structure can be obtained. It should be noted that if the temperature in the last step is lower than 650-700 °C, it will lead to incomplete removal of the organic residue.

[0047] In some preferred embodiments of the present invention, after the micro-nano three-dimensional glass green body is developed, it is then sintered. Exemplarily, the sample after femtosecond laser processing is placed in an ethanol solution for about 20-50 min, preferably 30 min, to remove the uncross-linked nanoparticles and only retain the formed three-dimensional glass green body structure.

[0048] The present invention uses a scanning electron microscope (SEM) to characterize the micro-nano transparent glass three-dimensional structure prepared by the above preparation method, and finds that its three-dimensional forming effect is good and the fidelity is high. After measurement, the structure shrinkage rate generated by low-temperature sintering is extremely small, and the linear shrinkage rate is less than 5%. Using a transmission electron microscope (TEM) to detect the inside of the structure, the results show that there are nano-pores inside the micro-nano transparent glass three-dimensional structure after low-temperature sintering, and the average diameter is about 6 nm.

[0049] The present invention also proves the transparency of the micro-nano glass three-dimensional structure through an optical microscope, and the results show that the transparency of the micro-nano glass structure is high.

[0050] The above results show that the micro-nano transparent glass three-dimensional structure provided by the present invention is a transparent nano-porous glass, which not only has a low sintering temperature, but also has a low shrinkage rate and high transparency.

[0051] In summary, for the above preparation method provided by the present invention, first, a glass precursor photoresist that can be directly cross-linked by femtosecond laser two-photon polymerization of silica nanoparticles is provided. The material configuration is simple and the cost is low. It realizes the low-temperature and low-shrinkage processing of three-dimensional transparent glass with a feature size of hundreds of nanometers, providing a reference for the development of various glass precursor photoresists. Then, the femtosecond laser with high processing precision is used to process the micro-nano three-dimensional glass green body with closely cross-linked nanoparticles. The three-dimensional forming effect is good, breaking through the limit of the existing glass manufacturing process. Finally, a low-temperature sintering post-treatment process is adopted. By setting a suitable heating curve and holding time, the structure can be sintered transparently at low temperature, and finally a three-dimensional structure of micro-nano glass with high transparency is obtained. During the sintering process, the structure only produces a linear shrinkage of less than 5%, and the fidelity is high.

[0052] The above preparation method and the prepared three-dimensional structure of micro-nano transparent glass have great application value in many application fields such as optics, biology, and medicine.

[0053] To further illustrate the present invention, the following examples are used for detailed description. The solution of methacrylic acid-modified silica nanoparticles used in the following examples of the present invention was purchased from Shanghai Jiute Nano Materials Technology Co., Ltd., with the model of methacrylic acid-modified nano-silica sol (40 wt%, solvent: propylene glycol methyl ether). Among them, the mass ratio of methacrylic acid to silica nanoparticles (particle size of 20 nm) is 22:78.

[0054] Example 1 1) Material preparation: As Figure 1 shown, 2 g of the solution containing methacrylic acid-modified silica nanoparticles (mass fraction of methacrylic acid-modified silica nanoparticles: 40%; solvent is propylene glycol methyl ether) was oscillated and mixed with 40 mg of tetraethyl rhodamine ketone (photoinitiator), and ultrasonicated until tetraethyl rhodamine ketone was completely dissolved. Subsequently, the obtained solution was baked in an oven at 65 °C for 20 h to reduce the solvent content in the solution, and a glass precursor photoresist was obtained.

[0055] 2) Femtosecond laser two-photon polymerization: a. Coating: 10 μL of the glass precursor photoresist was pipetted onto a quartz glass slide; b. Baking the photoresist: The glass slide was heated on a hot plate at 100 °C for 90 s; c. Processing: Using as Figure 2The femtosecond laser two-photon polymerization processing system places the baked glass slide as a sample on the Z-axis piezostage and fixes it, with the glass slide facing the side of the oil immersion objective lens. The femtosecond laser is emitted by a titanium sapphire laser, and after passing through a half-wave plate, a polarization beam splitter, and a beam expander, it is incident on the scanning galvanometer. The scanning galvanometer controls the reflection angle of the mirror to achieve the deflection of the laser beam and complete the movement of the laser in the XY two-dimensional plane. After the laser exits the scanning galvanometer, it enters the oil immersion objective lens (60×, 1.4 NA) through a 4f lens group and a mirror, and the laser beam is focused inside the glass precursor photoresist. Manually coarsely adjust the Z-axis position of the sample so that the initial light spot is located at the interface between the quartz glass slide and the glass precursor photoresist. Structures such as Figure 3 The six different glass three-dimensional structure models shown are imported into the processing software in sequence. After adjusting the processing parameters (single-point exposure time: 800 µs, processing power: 20 mW), the processing is carried out. Among them, during the above processing process, the femtosecond laser two-photon polymerization process of the micro-nano three-dimensional glass green body is as shown in Figure 4 Shown.

[0056] 3) Development: After the processing is completed, remove the sample and place it in an ethanol solution for inverted development for 30 min.

[0057] 4) Low-temperature sintering: As shown in Figure 5 Shown, place the developed sample in a muffle furnace, raise the temperature to 200 °C at a heating rate of 1 °C / min and hold for 2 h to remove the residual solvent in the structure, then raise the temperature to 400 °C at a heating rate of 1 °C / min and hold for 3 h to remove the organic substances in the structure, then raise the temperature to 650 °C at a heating rate of 1 °C / min and hold for 5 h, and finally cool naturally to room temperature to finally obtain a transparent micro-nano glass three-dimensional structure.

[0058] Characterization Use SEM to characterize the morphology of the glass three-dimensional structure after low-temperature sintering. As shown in Figure 6 Shown, indicating that the morphology is controllable and the fidelity is high.

[0059] Characterize the shrinkage rate of the obtained different glass three-dimensional structures. As shown in Figure 7 Shown, where Structure 1: The shrinkage in the X direction is 4.10%, the shrinkage in the Y direction is 4.27%, and the shrinkage in the Z direction is 4.27%; Structure 2: The shrinkage in the X direction is 4.55%, the shrinkage in the Y direction is 4.44%, and the shrinkage in the Z direction is 4.86%; Structure 3: The shrinkage in the X direction is 4.85%, the shrinkage in the Y direction is 4.56%, and the shrinkage in the Z direction is 4.86%; Structure 4: The shrinkage in the X direction is 4.87%, the shrinkage in the Y direction is 4.31%, and the shrinkage in the Z direction is 4.42%; As shown in Figure 7 Shown.

[0060] Characterize the transparency of the low-temperature sintered glass. The test structure is Structure 5, and the results are as Figure 8 shown. Through an optical microscope, the letters under the square can be clearly seen, indicating that the low-temperature sintered glass has excellent transparency.

[0061] Characterize the roughness of the low-temperature sintered glass. The test structure is Structure 6, and the characterization is carried out on the surface of the micro-square. The results are as Figure 9 shown, where Figure 9 a in is the SEM image of Structure 6 used in the test, Figure 9 b in is the surface profile map obtained by an atomic force microscope, Figure 9 c in is the profile map extracted from the position of the white line in b. The arithmetic mean deviation of the profile (Ra) is 5.6 nm, indicating good surface quality.

[0062] Carry out Raman spectroscopy characterization on the low-temperature sintered glass. The test structure is Structure 6, and the test results are as Figure 10 shown, where ω1 and ω3 bands correspond to the bending vibration of the Si(O 1 / 2 )4 tetrahedral Si-O-Si bridges, and the ω4 band is attributed to the stretching motion of the Si-O bond. The D1 and D2 lines correspond to the symmetric stretching of the siloxane ring molecules. An additional peak appears at 982 cm -1 , indicating the presence of Si-OH in the structure. The Raman spectrum shows that the silica nanoparticles are sintered to form a continuous silica network inside the glass.

[0063] Carry out TEM detection on the inside of the structure of the low-temperature sintered glass. The test structure is a thin slice extracted from Structure 6 by focused ion beam cutting. The results show that there are nano-pores inside the low-temperature sintered glass, with an average diameter of 6 nm, as Figure 11 shown.

[0064] The above characterization results can prove that the three-dimensional microstructure obtained by using the preparation method provided by the present invention is transparent silica glass, which not only can achieve a low sintering temperature, but also has a low shrinkage rate and high transparency.

[0065] Example 2 1) Prepare materials: As Figure 1 shown, 3 g of a solution containing methacrylic acid-modified silica nanoparticles (mass fraction of methacrylic acid-modified silica nanoparticles: 40%; solvent is propylene glycol methyl ether) is oscillated and mixed with 60 mg of tetraethyl rhodamine (photoinitiator), and ultrasonicated until tetraethyl rhodamine is completely dissolved. Subsequently, the obtained solution is baked in an oven at 75 °C for 16 h to reduce the solvent content in the solution.

[0066] 2) Femtosecond laser two-photon polymerization: a. Glue application: Use a pipette to take 10 µL of the glass precursor photoresist and drop it onto a quartz glass slide. b. Baking the photoresist: Place the glass slide on a hot plate at 100 °C and heat for 70 s. c. Processing: Use a femtosecond laser two-photon polymerization processing system as Figure 2 . Place the baked glass slide as a sample on the Z-axis piezostage and fix it, with the glass slide facing the oil immersion objective lens side. The femtosecond laser is emitted by a titanium sapphire laser, and after passing through a half-wave plate, a polarization beam splitter, and a beam expander, it is incident on the scanning galvanometer. The scanning galvanometer controls the reflection angle of the mirror to deflect the laser beam and complete the movement of the laser in the XY two-dimensional plane. After the laser beam exits the scanning galvanometer, it passes through a 4f lens group and a mirror and then enters the oil immersion objective lens (60×, 1.4 NA). The laser beam is focused inside the glass precursor photoresist by the oil immersion objective lens. Manually coarsely adjust the Z-axis position of the sample so that the initial light spot is located at the interface between the quartz glass slide and the glass precursor photoresist. Import the 6 different three-dimensional structure models as Figure 3 shown into the processing software in sequence. After adjusting the processing parameters (single-point exposure time: 1000 µs, processing power: 17 mW), start the processing. Among them, during the above processing process, the femtosecond laser two-photon polymerization process of the micro-nano three-dimensional glass green body is as Figure 4 shown.

[0067] 3) Development: After the processing is completed, remove the sample and place it in an ethanol solution for inverted development for 20 min.

[0068] 4) Low-temperature sintering: As Figure 5 shown, place the developed sample in a muffle furnace. Raise the temperature to 180 °C at a heating rate of 2 °C / min and hold for 2.5 h to remove the residual solvent in the structure. Then raise the temperature to 420 °C at a heating rate of 2 °C / min and hold for 3 h to remove the organic substances in the structure. Subsequently, raise the temperature to 680 °C at a heating rate of 2 °C / min and hold for 6 h. Finally, let it cool naturally to room temperature to obtain a transparent micro-nano glass three-dimensional structure.

[0069] Characterization refers to Example 1, and the results are the same as those in Example 1.

[0070] Example 3 1) Preparation of materials: As Figure 1 shown, mix 1 g of a solution containing methacrylic acid-modified silica nanoparticles (mass fraction of methacrylic acid-modified silica nanoparticles: 40%; solvent is propylene glycol methyl ether) with 20 mg of tetraethyl rhodamine ketone (photoinitiator) by oscillation, and ultrasonicate until the tetraethyl rhodamine ketone is completely dissolved. Subsequently, bake the obtained solution in an oven at 60 °C for 18 h to reduce the solvent content in the solution.

[0071] 2) Femtosecond laser two-photon polymerization: a. Coating: Use a pipette to take 10 µL of glass precursor photoresist and drop it on a quartz glass slide. b. Baking the photoresist: Place the glass slide on a hot plate at 100 °C and heat for 100 s. c. Processing: Use a femtosecond laser two-photon polymerization processing system such as Figure 2 . Place the baked glass slide as a sample on the Z-axis piezoelectric stage and fix it, with the glass slide facing the side of the oil immersion objective lens. The femtosecond laser is emitted by a titanium-sapphire laser, and after passing through a half-wave plate, a polarization beam splitter, and a beam expander, it is incident on the scanning galvanometer. The scanning galvanometer controls the reflection angle of the mirror, thereby achieving the deflection of the laser beam and completing the movement of the laser in the XY two-dimensional plane. After the laser beam exits the scanning galvanometer, it enters the oil immersion objective lens (60×, 1.4 NA) through a 4f lens group and a mirror. The laser beam is focused inside the glass precursor photoresist by the oil immersion objective lens. Manually and roughly adjust the Z-axis position of the sample so that the initial light spot is located at the interface between the quartz glass slide and the glass precursor photoresist. Import the 6 different three-dimensional structure models shown in Figure 3 into the processing software in sequence. After adjusting the processing parameters (single-point exposure time: 600 µs, processing power: 23 mW), perform the processing. Among them, during the above processing process, the femtosecond laser two-photon polymerization process of the micro-nano three-dimensional glass green body is as shown in Figure 4 .

[0072] 3) Development: After the processing is completed, remove the sample and place it in an ethanol solution for inverted development for 40 min.

[0073] 4) Low-temperature sintering: As shown in Figure 5 , place the developed sample in a muffle furnace. Raise the temperature to 220 °C at a heating rate of 1.5 °C / min and hold for 3 h to remove the residual solvent in the structure. Then raise the temperature to 450 °C at a heating rate of 1.5 °C / min and hold for 3 h to remove the organic substances in the structure. Subsequently, raise the temperature to 700 °C at a heating rate of 1.5 °C / min and hold for 8 h. Finally, let it cool naturally to room temperature to finally obtain a transparent micro-nano glass three-dimensional structure.

[0074] The characterization refers to Example 1, and the results are consistent with those of Example 1.

[0075] The foregoing description of the disclosed embodiments enables those skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A preparation method of a three-dimensional structure of micro-nano transparent glass, characterized in that, It includes the following steps: S1: After mixing the solution of silica nanoparticles modified with a photo-responsive ligand and a photoinitiator, drying is carried out to obtain a glass precursor photoresist. The photo-responsive ligand includes any one or more of methacrylic acid, methacryloxytrimethoxysilane or styryl triethoxysilane. S2: The glass slide carrying the glass precursor photoresist is subjected to laser processing to obtain a micro-nano three-dimensional glass green body. After sintering, it is cooled to obtain a micro-nano transparent glass three-dimensional structure. The temperature of the sintering does not exceed 700 °C.

2. The preparation method according to claim 1, characterized in that, The laser processing is femtosecond laser processing. In the laser processing, the exposure time of the laser is 400 - 1000 µs and the power is 11 - 29 mW.

3. The preparation method according to claim 1 or 2, characterized in that, The sintering is carried out according to the following procedure: Heat up to 160 - 240 °C and keep warm for 2 - 3 h. Heat up to 400 - 450 °C and keep warm for 3 - 4 h. Heat up to 650 - 700 °C and keep warm for 5 - 10 h.

4. The preparation method according to claim 1, wherein, The heating rate during the sintering is 1 - 3 °C / min.

5. The preparation method according to claim 1, characterized in that The mass fraction of the solute in the solution of silica nanoparticles modified with a photo-responsive ligand is 30 - 60%. The particle size of the silica nanoparticles is 15 - 30 nm. The solvent in the solution of silica nanoparticles modified with a photo-responsive ligand includes any one or more of propylene glycol monomethyl ether, ethanol, isopropanol, n-butanol, ethylene glycol or propylene glycol. The photoinitiator includes any one or more of tetraethyl Michler's ketone, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide or 7-diethylamino-3-thienoylcoumarin.

6. The preparation method according to claim 1, wherein, The mass ratio of the photo-responsive ligand to the silica nanoparticles is 22:78 - 18:

82. The mass ratio of the silica nanoparticles modified with a photo-responsive ligand to the photoinitiator is 20:(0.5 - 1.5).

7. The preparation method according to claim 1, characterized in that, The mixing is carried out until the photoinitiator is completely dissolved. The temperature of the drying is 50 - 80 °C and the time is 10 - 30 h.

8. The preparation method according to claim 1, characterized in that, After the micro-nano three-dimensional glass green body is developed, sintering is carried out. The development is carried out in an ethanol solution.

9. The micro-nano transparent glass three-dimensional structure prepared by the preparation method according to any one of claims 1 to 8, characterized in that, The shrinkage rate of the micro-nano transparent glass three-dimensional structure is lower than 5%.

10. Application of the micro-nano transparent glass three-dimensional structure prepared by the preparation method according to any one of claims 1 - 8 in the preparation of optical fiber integrated devices.

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