SiOC ceramic and femtosecond laser preparation method thereof

Abstract

The invention relates to the technical field of ceramic printing, in particular to SiOC ceramic and a femtosecond laser preparation method thereof.The femtosecond laser preparation method of the SiOC ceramic comprises the steps that the end face of an optical fiber is cut flat through an optical fiber cutter; dropwise adding acrylate siloxane photosensitive resin to the surface of the cover glass, and vertically immersing the end face of the optical fiber which is cut flat into the acrylate siloxane photosensitive resin; the light spot position of femtosecond laser is adjusted and focused to the end face of the optical fiber; a printing model is imported, laser printing parameters are adjusted, and a pre-ceramic structure is obtained through printing; and taking down the optical fiber, washing, drying, and carrying out heat treatment to obtain the SiOC ceramic. The basic principle of the method mainly depends on a multi-photon photopolymerization reaction, and when femtosecond laser scans in photosensitive resin along a scanning path, the forming process of a 3D structure can be realized. Multi-photon polymerization is expansion of two-photon polymerization, polymerization reaction is initiated by absorbing a plurality of photons, and the method is suitable for manufacturing a more complex three-dimensional structure.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic printing, and in particular to a SiOC ceramic and a method for preparing the same by femtosecond laser. Background Art

[0002] As an important inorganic material, ceramics play an irreplaceable role in scientific research and industrial fields. Especially, SiOC ceramics are widely used in harsh engineering fields such as high temperature, high strength, corrosion resistance, and wear resistance due to their excellent oxidation resistance, thermal stability, and mechanical properties. SiOC ceramics, with their extremely high hardness, excellent thermal stability, and electrical insulation properties, play an important role in fields such as aerospace, energy, machinery, optics, and biomedicine. Especially, they have important value in micro-nano optical devices, sensors, and high-performance optical fiber communication systems.

[0003] However, due to the inherent brittleness and high hardness of SiOC ceramics themselves, traditional processing methods such as mechanical cutting, grinding, and drilling have problems such as low processing accuracy, high difficulty, easy generation of cracks, and surface damage. Traditional ceramic additive printing technologies, including stereolithography and digital light printing, although they can realize the three-dimensional forming of ceramics, their characteristic size resolution is usually limited to the millimeter and micron levels. In addition, these technologies rely on polysiloxane precursor photoresist materials and require vacuum high-temperature sintering (temperature up to above 1000 °C) to realize the transformation of SiOC precursors into continuous SiOC structures, which far exceeds the melting points of optical fiber and semiconductor substrate materials. At the same time, due to the cross-linked organic resin contained in the photoresist, the removal of organic components during the sintering process often leads to serious dimensional shrinkage, usually exceeding 50% (the minimum can reach 30%), severely limiting the application of SiOC ceramics in the field of precision integration. Especially in the precision processing of optical fiber end faces, traditional processing methods are difficult to meet the requirements of high precision, no thermal influence, and no material deformation, restricting their wide application in high-precision devices such as optical fiber sensors and optical components.

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

[0005] In view of the above deficiencies of the existing technology, the purpose of the present invention is to provide a SiOC ceramic and a method for preparing the same by femtosecond laser, aiming to solve the problem of dimensional shrinkage existing in the sintering process of the existing SiOC ceramic preparation method.

[0006] The technical solution of the present invention is as follows:

[0007] A method for preparing a SiOC ceramic by femtosecond laser, comprising the steps of:

[0008] Using an optical fiber cutting tool to flatten the end face of the optical fiber;

[0009] Drop the acrylate siloxane photosensitive resin onto the surface of the cover glass, and vertically immerse the cut end face of the optical fiber into the acrylate siloxane photosensitive resin;

[0010] Adjust the spot position of the femtosecond laser and focus it on the end face of the optical fiber;

[0011] Import the printing model, adjust the laser printing parameters, and print to obtain a pre-ceramic structure;

[0012] Remove the optical fiber, wash and dry it, and then perform heat treatment to obtain SiOC ceramic.

[0013] The method for preparing SiOC ceramic by femtosecond laser, wherein the parameters of the femtosecond laser include: wavelength is 700nm - 1100nm, repetition frequency is 1MHz - 10MHz, and pulse width is 50fs - 500fs.

[0014] The method for preparing SiOC ceramic by femtosecond laser, wherein the laser printing parameters include output power, slice spacing, fill spacing, and printing speed.

[0015] The method for preparing SiOC ceramic by femtosecond laser, wherein the heating rate of the heat treatment is 1°C / min - 3°C / min, the temperature of the heat treatment is 600°C - 700°C, the time of the heat treatment is 1h - 2h, and the cooling rate of the heat treatment is 2°C / min - 4°C / min.

[0016] The method for preparing SiOC ceramic by femtosecond laser, wherein the preparation method of the acrylate siloxane photosensitive resin includes the steps of:

[0017] Mix the silicon source, silane coupling agent and organic solvent, and add a cross-linking agent after hydrolysis and condensation reaction to obtain an acrylate siloxane solution;

[0018] Mix the photoinitiator and organic solvent to obtain a photoinitiator solution;

[0019] Mix the acrylate siloxane solution and the photoinitiator solvent to obtain a photosensitive polymer solution;

[0020] Remove the organic solvent in the photosensitive polymer solution to obtain the acrylate siloxane photosensitive resin.

[0021] The method for preparing SiOC ceramic by femtosecond laser, wherein the silicon source is selected from one or more of them; and / or, the silane coupling agent is selected from one or more of 3-(trimethoxysilyl)propyl methacrylate, vinyltrimethoxysilane, and vinyltriethoxysilane.

[0022] The femtosecond laser preparation method of the SiOC ceramic, wherein the cross-linking agent is selected from one or more of ethoxylated trimethylolpropane triacrylate, butyl acrylate, and pentaerythritol triacrylate.

[0023] The femtosecond laser preparation method of the SiOC ceramic, wherein the photoinitiator is selected from one or more of tetraethyl rhodamine ketone, 4,4'-bis(dimethylamino)benzophenone, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone.

[0024] In the preparation method of the acrylate siloxane photosensitive resin in the femtosecond laser preparation method of the SiOC ceramic, by mass percentage, the silicon source is 65wt%-85wt%, the silane coupling agent is 5wt%-25wt%, the cross-linking agent is 7wt%-10wt%, and the photoinitiator is 0.5wt%-1.5wt%.

[0025] A SiOC ceramic prepared by using the femtosecond laser preparation method of the SiOC ceramic.

[0026] Beneficial effects: The present invention provides a SiOC ceramic and a femtosecond laser preparation method thereof. The femtosecond laser preparation method of the SiOC ceramic includes the steps of: using an optical fiber cutting knife to cut the end face of the optical fiber flat; dropping acrylate siloxane photosensitive resin onto the surface of a cover glass, and vertically immersing the cut flat end face of the optical fiber into the acrylate siloxane photosensitive resin; adjusting the spot position of the femtosecond laser and focusing it on the end face of the optical fiber; importing a printing model, adjusting the laser printing parameters, and printing to obtain a pre-ceramic structure; removing the optical fiber, washing and drying it, and then performing heat treatment to obtain the SiOC ceramic. The present invention uses acrylate siloxane photosensitive resin as the printing material, and adopts femtosecond laser multi-photon lithography technology to prepare a pre-ceramic polymer, and finally obtains the final SiOC ceramic through heat treatment. The basic principle of this technology mainly relies on the multi-photon photopolymerization reaction. The photoinitiator in the resin will simultaneously absorb multiple photons, undergo non-linear absorption, generate free radicals, thereby inducing the polymerization of acrylate groups and initiating the polymerization reaction of monomers to form micro-polymerized voxels. Compared with two-photon polymerization, the advantage of multi-photon polymerization is that the probability of two-photon absorption is proportional to the square of the light intensity, so the polymerization reaction only occurs at the laser focus, while the probability of multi-photon absorption is proportional to the high power of the light intensity, which enables this process to achieve sub-micron resolution. When the femtosecond laser scans inside the photosensitive resin along the scanning path, the precise forming of a three-dimensional structure can be achieved. Multi-photon polymerization can be regarded as an extension of two-photon polymerization. It initiates the polymerization reaction by absorbing multiple photons, so it is suitable for manufacturing more complex three-dimensional structures. In addition, this method has the characteristics of low shrinkage (<30%) and low-temperature post-treatment (<650 °C), effectively reducing the deformation risk of the material during the forming process, and can be applied to fields such as biomedicine, aerospace, and micro-electro-mechanical system sensing. That is, this photosensitive resin has high chemical stability, can effectively reduce the curing shrinkage rate, and ensure the morphology accuracy and dimensional stability of the prepared structure. Description of the Drawings

[0027] Figure 1 It is a process flow schematic diagram of a femtosecond laser preparation method of a SiOC ceramic according to the present invention;

[0028] Figure 2 It is a process flow schematic diagram of a preparation method of an acrylate siloxane photosensitive resin according to the present invention;

[0029] Figure 3 It is a physical diagram of the acrylate siloxane photosensitive resin prepared in Example 1;

[0030] Figure 4 It is a three-dimensional micro-nano structure diagram of SiOC ceramics with different structures;

[0031] Figure 5 It is a comparison diagram of SiOC ceramics before and after pyrolysis at different filling distances;

[0032] Figure 6 The pyrolysis shrinkage rate curve of SiOC ceramics at different filling distances;

[0033] Figure 7 The micrograph of the SiOC microcantilever beam at the fiber end face. Detailed implementation manners

[0034] The present invention provides a SiOC ceramic and a femtosecond laser preparation method thereof. To make the purpose, technical solution and effects of the present invention clearer and more definite, the present invention will be further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0035] Those skilled in the art of the present technology can understand that, unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as the general understanding of those of ordinary skill in the art to which the present invention belongs. It should also be understood that those terms defined in a general dictionary, should be understood to have a meaning consistent with the meaning in the context of the prior art, and will not be interpreted with an idealized or overly formal meaning unless specifically defined as here.

[0036] In recent years, ultrafast laser technology has shown unique advantages in the field of material processing. As a typical ultrafast laser source, femtosecond laser has an extremely short pulse width (usually picosecond or femtosecond level), and can release high-intensity energy in an extremely short time, so as to achieve high-precision microfabrication without significantly heating the surrounding area. Through ultrafast laser processing, problems such as cracks and deformations caused by surface thermal effects of ceramic materials can be effectively reduced, so as to achieve high-precision and low-thermal-impact processing of SiOC ceramic materials. In the aspect of fiber end face processing, ultrafast laser technology can not only achieve the precise preparation of SiOC ceramic materials and form complex micro-nano structures (such as microlenses, microcantilever beams, etc.), but also concentrate the energy on the surface and near-surface regions of the material through the non-thermal action mechanism of the laser, achieving a processing accuracy of micron level or even sub-micron level, which is of great significance for improving the optical performance of the fiber end face and increasing the coupling efficiency between the fiber and the external medium. Therefore, using femtosecond laser to print and process SiOC ceramics on the fiber end face can not only overcome the limitations of traditional processing methods, but also realize innovative applications in the fields of high-precision fiber sensors, optical components and micro-robots. And it will promote the breakthrough and development of SiOC ceramics in higher precision and wider application fields, and at the same time play an important role in promoting the technological progress in the fields of optical fiber communication, sensors and biomedicine.

[0037] Based on this, as Figure 1 shown, the present invention also provides a femtosecond laser preparation method of SiOC ceramic, including the steps:

[0038] Step S100: Use an optical fiber cutter to cut the end face of the optical fiber flat and fix it.

[0039] Step S200: Drop acrylate siloxane photosensitive resin onto the surface of the cover glass, and vertically immerse the cut flat end face of the optical fiber into the acrylate siloxane photosensitive resin.

[0040] Step S300: Adjust the spot position of the femtosecond laser and focus it on the end face of the optical fiber.

[0041] Step S400: Import the printing model, adjust the laser printing parameters, and print to obtain a pre-ceramic structure.

[0042] Step S500: Remove the optical fiber, wash and dry it, and then perform heat treatment to obtain SiOC ceramic.

[0043] In this embodiment, acrylate siloxane photosensitive resin is used as the printing material, and a pre-ceramic polymer is prepared by femtosecond laser multi-photon lithography technology. Finally, the final SiOC ceramic is obtained through heat treatment. The basic principle of this technology mainly relies on the photopolymerization reaction. Generally, the photopolymerization reaction includes two-photon polymerization (TPP) and multi-photon polymerization (MPP). TPP essentially relies on the nonlinear effect of two-photon absorption to achieve precise structure preparation. Different from the common single-photon absorption mechanism, two-photon polymerization means that when a femtosecond laser with a certain intensity is focused on the organic photosensitive resin, the photoinitiator in the resin will simultaneously absorb two photons, undergo nonlinear absorption, generate free radicals, and induce the polymerization of acrylate groups, triggering the polymerization reaction of monomers to form micro-polymerized voxels. Since the probability of two-photon absorption is proportional to the square of the light intensity, the polymerization reaction only occurs at the laser focus, which enables this process to achieve sub-micron resolution. When the femtosecond laser scans inside the photosensitive resin along the scanning path, the 3D structure forming process can be realized. Multi-photon polymerization is an extension of two-photon polymerization, which initiates the polymerization reaction by absorbing multiple photons, so it is suitable for manufacturing more complex three-dimensional structures. Moreover, the advantages of multi-photon polymerization include: having a wider material adaptability; having a stronger nonlinear absorption effect and a smaller polymerization focus, which can break through the diffraction limit and achieve ultra-high resolution; low light damage; smaller light scattering; and being suitable for manufacturing more complex three-dimensional structures.

[0044] Specifically, the present invention integrates a three-dimensional SiOC ceramic micro-nano structure with special functions on the fiber end face, endowing it with characteristics such as electromagnetic interference resistance, fast response, and high sensitivity. This structure can effectively improve the stability of the fiber optic sensor in complex environments and is applicable to fields such as biological monitoring (e.g., cell analysis), medical diagnosis (e.g., real-time monitoring), and environmental monitoring (e.g., pollutant monitoring). The three-dimensional micro-nano ceramic structure on the fiber end face proposed by the present invention has the advantages of simple preparation process, low cost, high resolution, low-temperature post-treatment, and low shrinkage, and has a wide range of applications. At the same time, the SiOC material can be combined with other functional materials (such as metal oxides, polymers, etc.) to form a heterostructure, further expanding its application scope. For example, combined with optical materials, it can be used for micro-lens manufacturing; combined with piezoelectric materials, it can be used for MEMS sensors; combined with biological materials, it can be used for biomedical detection.

[0045] Furthermore, the three-dimensional micro-nano ceramic on the fiber end face is prepared by femtosecond laser multi-photon lithography technology. This method can achieve a ceramic structure with high resolution and low shrinkage by selecting other functional ceramic materials or designing different three-dimensional micro-nano structures (such as cantilever beams, micro-lenses, micro-resonators, etc.) and combining with a low-temperature sintering process. In addition, the SiOC ceramic can be replaced by other ceramic materials (such as alumina, silicon nitride, etc.) to prepare sensors with various properties (such as temperature, pressure, humidity, etc.). This flexibility enables it to meet more diverse application requirements, such as pressure sensing in high-temperature environments and humidity monitoring in high-humidity environments.

[0046] In some embodiments, the parameters of the femtosecond laser include: wavelength of 700 nm - 1100 nm, repetition frequency of 1 MHz - 10 MHz, and pulse width of 50 fs - 500 fs.

[0047] In some embodiments, the laser printing parameters include output power, slice spacing, fill spacing, and printing speed.

[0048] In some embodiments, the output power is 1 mW - 40 mW; the slice spacing is 100 nm - 300 nm; the fill distance is 50 nm - 400 nm; the printing speed is 4 mm / s - 20 mm / s.

[0049] In a preferred embodiment, the slice spacing is 300 nm; the fill distance is 300 nm. For solid structures, the fill spacing should not exceed 300 nm to avoid layer defect; the printing speed is 8 mm / s.

[0050] In some embodiments, the heating rate of the heat treatment is 1 °C / min - 3 °C / min, the temperature of the heat treatment is 600 °C - 700 °C, the time of the heat treatment is 1 h - 2 h, and the cooling rate of the heat treatment is 2 °C / min - 4 °C / min. Through the heat treatment, the organic components in the pre-ceramic structure are decomposed to form a dense SiOC ceramic structure.

[0051] In a preferred embodiment, the heating rate of the heat treatment is 1 °C / min, the temperature of the heat treatment is 600 °C, the time of the heat treatment is 2 h, and the cooling rate of the heat treatment is 3 °C / min.

[0052] Specifically, the steps of fabricating the SiOC ceramic structure using ultrafast laser 3D printing include the following:

[0053] 1) Fiber end face treatment. Use a fiber optic cutter to cut the fiber end face flat, ensure that the end face is smooth and undamaged, and fix it on a three-axis displacement platform through a fiber optic fixture to ensure stability during the printing process;

[0054] 2) Photosensitive polymer dropping. Drop a small amount of acrylate siloxane photosensitive resin onto the fixed cover glass to form a uniform photosensitive polymer droplet, and vertically immerse the fiber end face into the resin;

[0055] 3) Laser focusing. Drop a small amount of refractive index modulation oil onto the 40x objective lens. Under the monitoring of a CCD camera, adjust the position of the femtosecond laser (1030 nm, 1 MHz, 300 fs) spot and directly focus it on the core of the fiber end face to ensure that the laser energy is concentrated and accurate;

[0056] 4) Model printing. Import the STL format printing model file, adjust the laser printing parameters (including output power, slice spacing, fill spacing, printing speed, etc.), and print a specific pre-ceramic structure. During the printing process, it is necessary to monitor the laser power and focusing status in real time to ensure printing accuracy;

[0057] 5) Post-treatment cleaning. Remove the fiber, dissolve the uncured photosensitive polymer on the fiber end face in acetone (1 - 3 min) and isopropyl alcohol (1 - 3 min) solutions in sequence to remove the unreacted polymer, and dry it in the air;

[0058] 6) Heat treatment. Place the fiber in a vacuum tube furnace for heat treatment, with a heating rate of 1 °C / min, hold at 600 °C for 2 h, and a cooling rate of 3 °C / min. During the heat treatment, the organic components are decomposed to form a dense SiOC ceramic structure.

[0059] In some embodiments, as Figure 2 shown, the preparation method of the acrylate siloxane photosensitive resin includes the steps:

[0060] Step S10: Mix a silicon source, a silane coupling agent and an organic solvent, add a crosslinking agent after a hydrolysis and condensation reaction to obtain an acrylate siloxane solution;

[0061] Step S20: Mix a photoinitiator and an organic solvent to obtain a photoinitiator solution;

[0062] Step S30: Mix the acrylate siloxane solution and the photoinitiator solvent to obtain a photosensitive polymer solution;

[0063] Step S40: Remove the organic solvent from the photosensitive polymer solution to obtain an acrylate siloxane photosensitive resin.

[0064] In this embodiment, the preparation process of the acrylate siloxane photosensitive resin mainly involves a hydrolysis and condensation reaction. The silicon source serves as the basic framework, and its siloxane groups (Si-O-Si) and the methoxy (-OCH3) groups at one end of the silane coupling agent form a crosslinked network of monomers containing siloxane functional groups through a hydrolysis and condensation reaction. The carbon-carbon double bond (C=C) of the acrylate group carried at the other end of the silane coupling agent endows the resin with the ability of photopolymerization, ensuring the formation of a high-resolution three-dimensional structure during the photolithography process. At the same time, this photosensitive resin has excellent optical transparency, mechanical strength and thermal stability, and can achieve sub-micron resolution under the action of femtosecond laser. In addition, this technology has the characteristics of low shrinkage (<30%) and low-temperature post-treatment (<650 °C), effectively reducing the deformation risk of the material during the molding process, and can be applied to fields such as biomedicine, aerospace and microelectromechanical system sensing. That is, this photosensitive resin has high chemical stability, can effectively reduce the curing shrinkage rate, and ensure the morphological accuracy and dimensional stability of the prepared structure.

[0065] Specifically, the carbon-carbon double bond (C═C) of the acrylate group in the acrylate siloxane photosensitive resin endows it with photopolymerization ability, enabling it to be applicable to various lithography techniques such as two-photon polymerization, multi-photon polymerization, and single-photon ultraviolet lithography, thereby realizing the fabrication of 3D structures with sub-micron or even nano-scale precision, and it can be widely used in optoelectronic devices, microelectromechanical systems (MEMS), microfluidics, biomedicine and other fields; in addition, due to the matrix material silicon source having a siloxane backbone (Si-O-Si), the resin has high mechanical strength and excellent heat resistance after curing. After heat treatment, the resin can be transformed into a SiOC ceramic material, further improving its high-temperature resistance, corrosion resistance, and oxidation resistance, and being suitable for extreme environment applications; moreover, traditional photosensitive resins may cause microstructural deformation due to shrinkage during photocuring and heat treatment, while the siloxane groups (Si-O-Si) of the acrylate siloxane photosensitive resin have high chemical stability, which can effectively reduce the curing shrinkage rate and ensure the morphological accuracy and dimensional stability of the fabricated structure. At the same time, the acrylate siloxane photosensitive resin has good optical transparency, which can reduce the scattering of laser light inside the material and improve the effective utilization rate of laser energy at the focus; it can also optimize the material properties by adjusting the formulations of photoinitiators, crosslinking agents, etc., to adapt to different laser wavelengths, processing conditions, and application requirements.

[0066] In some embodiments, the silicon source is selected from but not limited to one or more of

[0067] It should be noted that all come from WakerChemie AG, Germany.

[0068] Generally, a photosensitive resin system is mainly composed of functional monomers, photoinitiators, and other additives. In order to obtain a SiOC ceramic material in the present invention, the precursor of the photosensitive resin needs to contain a siloxane backbone structure to ensure that a SiOC material can be formed after high-temperature pyrolysis. Selecting the above silicon source can undergo a hydrolysis reaction with a silane coupling agent; after the hydrolysis reaction, a silicon-oxygen functional monomer is formed, which together with the photoinitiator and crosslinking agent constitutes a photosensitive resin system, thereby improving the crosslinking degree of the resin during the subsequent photocuring process. Compared with the resin system prepared only using the silicon source, the resin system formed by adding a silane coupling agent exhibits a lower heat treatment shrinkage rate after photocuring.

[0069] In some embodiments, the silane coupling agent is selected from but not limited to one or more of 3-(trimethoxysilyl)propyl methacrylate (TMSPM), vinyltrimethoxysilane (VTMO), and vinyltriethoxysilane (VTEO). After mixing the above silane coupling agent with the silicon source, the formed resin system can exhibit a lower heat treatment shrinkage rate after photocuring.

[0070] In some embodiments, the crosslinking agent is selected from, but not limited to, one or more of ethoxylated trimethylolpropane triacrylate (ETPTA), butyl acrylate (BA), and pentaerythritol triacrylate (PETA). The role of the crosslinking agent is to form chemical bonds between the resin chains of the acrylate siloxane photosensitive resin, causing the resin monomer molecules to crosslink with each other to form a three-dimensional network structure, thereby achieving the purpose of increasing the strength of the polymerization structure.

[0071] In a preferred embodiment, the crosslinking agent is ethoxylated trimethylolpropane triacrylate (ETPTA), which can enhance the mechanical strength and photocuring performance of the polymer.

[0072] In some embodiments, the photoinitiator is selected from one or more of ethyl acetoacetate ethyl ester (EAB), 4,4'-bis(dimethylamino)benzophenone (BDEBP), phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO, Irgacure 819), and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone (Irgacure 369). When the above photoinitiator is added to the resin system, when a femtosecond laser with a certain intensity is focused on the organic photosensitive resin, the photoinitiator in the resin will simultaneously absorb multiple photons, undergo non-linear absorption, generate free radicals, and induce the polymerization of acrylate groups, initiating the polymerization reaction of the monomers to form micro-polymerized voxels.

[0073] In some embodiments, in the preparation method of the acrylate siloxane photosensitive resin, by mass percentage, the silicon source is 65wt% - 85wt%, the silane coupling agent is 5wt% - 25wt%, the crosslinking agent is 7wt% - 10wt%, and the photoinitiator is 0.5wt% - 1.5wt%.

[0074] In a preferred embodiment, in the preparation method of the acrylate siloxane photosensitive resin, by mass percentage, the silicon source is 70wt%, the silane coupling agent is 20wt%, the crosslinking agent is 9wt%, and the photoinitiator is 1wt%.

[0075] Specifically, in the formulation design of the photosensitive resin, to ensure the transparency and uniformity of the lithography material and to have suitable rheological properties, it is necessary to reasonably control the proportion of each component; the photosensitive resin obtained by mixing according to the above mass percentages is in a clear and transparent state and has a moderate viscosity, neither too viscous to affect the printing accuracy nor too thin to cause a decrease in curing stability. Moreover, the appropriate mass ratio plays a decisive role in the transparency and flow characteristics of the resin system, ensuring that it meets the processing requirements of femtosecond laser multi-photon lithography. In addition, the increase in the content of the silane coupling agent can not only reduce the shrinkage rate of the resin system, improve the morphological integrity of the printed structure after heat treatment, but also improve the mechanical properties and stability of the final structure. In practical applications, it is necessary to optimize the ratio of the silane coupling agent to the silicon source according to specific lithography process parameters and final material property requirements to obtain the best printing effect.

[0076] In some embodiments, the organic solvent is one or more of, but not limited to, acetone, isopropyl alcohol, and tetrahydrofuran.

[0077] Specifically, the preparation method of the acrylate siloxane photosensitive resin includes the steps of: slowly adding a silicon source to a silane coupling agent, adding an organic solvent to promote dissolution, and fully stirring with a stirrer for 12 h to ensure that the silicon source reacts fully with the coupling agent, then adding a crosslinking agent to obtain an acrylate siloxane solution; under an ultraviolet protection environment, dissolving a photoinitiator in an organic solvent and performing ultrasonic treatment for 3 - 5 min to obtain a photoinitiator solution, ensuring that the photoinitiator is evenly dispersed; mixing the photoinitiator solution with the acrylate siloxane solution and stirring evenly for 5 - 8 min to form a uniform photosensitive polymer solution; evaporating the photosensitive polymer solution in a fume hood for 3 - 5 h to remove 80% of the solvent to obtain a high-concentration acrylate siloxane photosensitive resin; to ensure long-term stability, storing the preparation in a light-shielded and room-temperature environment to avoid premature decomposition of the photoinitiator.

[0078] In addition, the present invention also provides an acrylate siloxane photosensitive resin prepared by using the preparation method of the acrylate siloxane photosensitive resin.

[0079] In this embodiment, the photosensitive resin prepared by using this preparation method has excellent optical transparency, mechanical strength, and thermal stability, and can achieve sub-micron resolution under the action of femtosecond laser. In addition, this technology has the characteristics of low shrinkage (<30%) and low-temperature post-treatment (<650 °C), effectively reducing the deformation risk of the material during the forming process, and can be applied to fields such as biomedicine, aerospace, and microelectromechanical system sensing. That is, this photosensitive resin has high chemical stability, can effectively reduce the curing shrinkage rate, and ensure the morphological accuracy and dimensional stability of the prepared structure.

[0080] Finally, the present invention also provides a SiOC ceramic prepared by using the femtosecond laser preparation method of the SiOC ceramic.

[0081] The following are further examples to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention all fall within the protection scope of the present invention.

[0082] Example 1

[0083] This example provides an acrylate siloxane photosensitive resin, and the specific preparation steps are as follows:

[0084] 1) Dissolve the silicon source. Slowly add 2 g 604 silicon source to 0.6 g of silane coupling agent TMSPM, add 2 mL of acetone to promote dissolution, and stir thoroughly with a stirrer for 12 h to ensure that the silicon source and the coupling agent react fully;

[0085] 2) Add the monomer. Add 250 mg of ethoxylated trimethylolpropane triacrylate ETPTA monomer to the above mixture to obtain an acrylate siloxane solution; ETPTA, as a crosslinking agent, can enhance the mechanical strength and photocuring performance of the polymer;

[0086] 3) Dissolve the photoinitiator. Under an ultraviolet protection environment, dissolve 30 mg of tetraethyl Michler's ketone EAB photoinitiator in 100 μL of acetone and ultrasonically treat for 4 min to ensure that the photoinitiator is evenly dispersed;

[0087] 4) Mix the solutions. Mix the photoinitiator solution and the acrylate siloxane solution, and stir evenly for 6 min to form a uniform photosensitive polymer solution;

[0088] 5) Evaporate the solvent. Evaporate for 4 h in a fume hood to remove about 80% of the solvent and obtain a high-concentration acrylate siloxane photosensitive resin.

[0089] 6) Preserve the preparation. To ensure long-term stability, preserve the preparation in a light-proof and room-temperature environment to avoid premature decomposition of the photoinitiator.

[0090] The physical diagram of the acrylate siloxane photosensitive resin prepared in this example is as Figure 3 shown.

[0091] Example 2

[0092] Using the acrylate siloxane photosensitive resin prepared in Example 1 as the printing material, use ultrafast laser 3D printing technology to prepare SiOC ceramic structures with different structures and different filling distances. The specific steps are as follows:

[0093] 1) Fiber end face treatment. Use a fiber cleaver to cut the fiber end face flat, ensure that the end face is smooth and undamaged, and fix it on a three-axis displacement platform through a fiber fixture to ensure stability during the printing process;

[0094] 2) Photosensitive polymer dripping. Drop a small amount of acrylate siloxane photosensitive resin onto the fixed cover glass to form a uniform photosensitive polymer droplet, and vertically immerse the fiber end face into the resin;

[0095] 3) Laser focusing. Drop a small amount of refractive index modulation oil onto the 40x objective lens. Under the monitoring of a CCD camera, adjust the position of the femtosecond laser (1030nm, 1MHz, 300fs) spot and directly focus it on the core of the fiber end face to ensure that the laser energy is concentrated and accurate;

[0096] 4) Model printing. Import the STL format printing model file, adjust the laser printing parameters (including output power, slice spacing, fill spacing, printing speed, etc.), and print a specific pre-ceramic structure. During the printing process, it is necessary to monitor the laser power and focusing state in real time to ensure printing accuracy;

[0097] 5) Post-processing cleaning. Remove the fiber, dissolve the uncured photosensitive polymer on the fiber end face in acetone (1 - 3min) and isopropyl alcohol (1 - 3min) solutions in sequence to remove the unreacted polymer, and dry it in the air;

[0098] 6) Heat treatment. Place the fiber in a vacuum tube furnace for heat treatment, with a heating rate of 1℃ / min, hold at 600℃ for 2h, and a cooling rate of 3℃ / min. During the heat treatment process, the organic components are decomposed to form a dense SiOC ceramic structure.

[0099] Three-dimensional micro-nano structure diagrams of SiOC ceramics with different structures are shown as Figure 4 shown, where Figure 4 (a)-(c) in are solid structures, and (d)-(f) are hollow structures. All samples are not heat-treated and are mainly used to evaluate the printability of the selected photosensitive resin and its adaptability to various structural forms. In terms of printing parameters, key factors such as output power, slice spacing, fill spacing, and printing speed are mainly considered.

[0100] The results show that the resin can achieve stable printing within the output power range of 1mW - 40mW, the adjustable range of slice spacing is 100nm - 300nm, the fill spacing is between 50nm - 400nm, and the printing speed can be set to 4mm / s - 20mm / s. As can be seen from Figure 4 it, the photosensitive resin prepared in Example 1 has excellent printability, can successfully manufacture various three-dimensional micro-nano structures, and the printing morphology is complete and of high quality.

[0101] The comparison diagrams of SiOC ceramics before and after pyrolysis at different filling distances are as follows Figure 5 As shown, in this embodiment, the woodpile photonic crystal structure is selected as the research object, and the control variable method is used. On the premise of a constant output power of 8 mW, a slice spacing of 300 nm, and a printing speed of 8 mm / s, the influence of the filling spacing on the structural stability is investigated. The filling spacing is set to 100 nm - 400 nm (step size 100 nm), and a total of four groups of experimental data are obtained. Figure 5 In (a)-(d) are the pre-ceramic structures before pyrolysis, and the corresponding (e)-(h) are the SiOC ceramic structures after pyrolysis, where (a) and (e), (b) and (f), (c) and (g), (d) and (h) are in a corresponding relationship.

[0102] The results show that under different filling spacing conditions, the prepared woodpile photonic crystal structures can be successfully printed, and the morphology before and after pyrolysis is well maintained with little shape change.

[0103] Based on Figure 5 the experimental conditions, on the premise of ensuring the consistency of the output power, slice spacing, and printing speed, the size shrinkage during the pyrolysis process is studied. The filling spacing is set to 100 nm - 400 nm (step size 50 nm), and a total of eight groups of printing data are obtained. The length and width of each sample are measured before and after pyrolysis, and their shrinkage rates are calculated. Finally, the shrinkage rate curve diagrams of SiOC ceramics at different filling distances as shown in Figure 6 are drawn. The data shows that the ceramic structure undergoes obvious size shrinkage after pyrolysis, and the overall shrinkage rate remains within the range of 24% - 28%, indicating that the shrinkage behavior under these process conditions has good controllability.

[0104] To verify the manufacturability of the SiOC ceramic three-dimensional micro-nano structure on the fiber end face. The SiOC microcantilever beam diagram on the fiber end face is as shown in Figure 7 . The results show that by optimizing the printing parameters, a microcantilever beam structure can be successfully constructed on the fiber end face, further expanding the application potential of this technology in the manufacture of fiber integrated microstructures.

[0105] In summary, a SiOC ceramic and a femtosecond laser preparation method thereof provided by the present invention. The femtosecond laser preparation method of the SiOC ceramic includes the steps of: using an optical fiber cutting knife to cut the end face of the optical fiber flat; dropping acrylate silicone oxygen alkane photosensitive resin onto the surface of a cover glass, and vertically immersing the cut flat end face of the optical fiber into the acrylate silicone oxygen alkane photosensitive resin; adjusting the spot position of the femtosecond laser and focusing it on the end face of the optical fiber; importing a printing model, adjusting the laser printing parameters, and printing to obtain a pre-ceramic structure; removing the optical fiber, washing and drying it, and then performing heat treatment to obtain the SiOC ceramic. The present invention uses acrylate silicone oxygen alkane photosensitive resin as the printing material, and adopts femtosecond laser multi-photon lithography technology to prepare a pre-ceramic polymer, and finally obtains the final SiOC ceramic through heat treatment. The basic principle of this technology mainly relies on the multi-photon photopolymerization reaction. The photoinitiator in the resin will simultaneously absorb multiple photons, undergo non-linear absorption, generate free radicals, thereby inducing the polymerization of acrylate groups and initiating the polymerization reaction of monomers to form micro-polymerized voxels. Compared with two-photon polymerization, the advantage of multi-photon polymerization is that the probability of two-photon absorption is proportional to the square of the light intensity, so the polymerization reaction only occurs at the laser focus, while the probability of multi-photon absorption is proportional to the high power of the light intensity, which enables this process to achieve sub-micron resolution. When the femtosecond laser scans inside the photosensitive resin along the scanning path, the precise forming of a three-dimensional structure can be achieved. Multi-photon polymerization can be regarded as an extension of two-photon polymerization. It initiates the polymerization reaction by absorbing multiple photons, so it is suitable for manufacturing more complex three-dimensional structures. In addition, this method has the characteristics of low shrinkage (<30%) and low-temperature post-treatment (<650 °C), effectively reducing the deformation risk of the material during the forming process, and can be applied to fields such as biomedicine, aerospace, and micro-electromechanical system sensing. That is, this photosensitive resin has high chemical stability, can effectively reduce the curing shrinkage rate, and ensure the morphology accuracy and dimensional stability of the prepared structure.

[0106] It should be understood that the application of the present invention is not limited to the above examples. For those of ordinary skill in the art, improvements or transformations can be made according to the above description, and all such improvements and transformations should fall within the protection scope of the appended claims of the present invention.

Claims

1. A femtosecond laser preparation method for SiOC ceramics, characterized in that, Including the steps: Using an optical fiber cutter to cut the end face of the optical fiber flat; Dropping acrylate siloxane photosensitive resin onto the surface of the cover glass, and vertically immersing the cut flat end face of the optical fiber into the acrylate siloxane photosensitive resin; Adjusting the spot position of the femtosecond laser and focusing it on the end face of the optical fiber; Importing a printing model, adjusting the laser printing parameters, and printing to obtain a pre-ceramic structure; Removing the optical fiber, washing and drying it, and then performing heat treatment to obtain SiOC ceramic.

2. The femtosecond laser preparation method of the SiOC ceramic according to claim 1, wherein The parameters of the femtosecond laser include: wavelength of 700 nm - 1100 nm, repetition frequency of 1 MHz - 10 MHz, and pulse width of 50 fs - 500 fs.

3. The femtosecond laser preparation method of the SiOC ceramic according to claim 1, characterized in that, The laser printing parameters include output power, slice spacing, fill spacing, and printing speed.

4. The femtosecond laser preparation method of the SiOC ceramic according to claim 1, characterized in that, The heating rate of the heat treatment is 1 °C / min - 3 °C / min, the temperature of the heat treatment is 600 °C - 700 °C, the time of the heat treatment is 1 h - 2 h, and the cooling rate of the heat treatment is 2 °C / min - 4 °C / min.

5. The femtosecond laser preparation method of SiOC ceramics according to claim 1, characterized in that, The preparation method of the acrylate siloxane photosensitive resin includes the steps: Mixing a silicon source, a silane coupling agent and an organic solvent, adding a crosslinking agent after hydrolysis and condensation reaction to obtain an acrylate siloxane solution; Mixing a photoinitiator and an organic solvent to obtain a photoinitiator solution; Mixing the acrylate siloxane solution and the photoinitiator solvent to obtain a photosensitive polymer solution; Removing the organic solvent in the photosensitive polymer solution to obtain acrylate siloxane photosensitive resin.

6. The femtosecond laser preparation method of the SiOC ceramic according to claim 5, characterized in that The silicon source is selected from 604, 610, one or more of MK; and / or, the silane coupling agent is selected from one or more of 3-(trimethoxysilyl)propyl methacrylate, vinyltrimethoxysilane, and vinyltriethoxysilane.

7. The femtosecond laser preparation method of the SiOC ceramic according to claim 5, characterized in that, The crosslinking agent is selected from one or more of ethoxylated trimethylolpropane triacrylate, butyl acrylate, and pentaerythritol triacrylate.

8. The femtosecond laser preparation method of the SiOC ceramic according to claim 5, characterized in that, The photoinitiator is selected from one or more of tetraethyl rhodamine ketone, 4,4'-bis(dimethylamino)benzophenone, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone.

9. The method for preparing SiOC ceramics by femtosecond laser according to claim 5, wherein, In the preparation method of the acrylate siloxane photosensitive resin, by mass percentage, the silicon source is 65 wt% - 85 wt%, the silane coupling agent is 5 wt% - 25 wt%, the crosslinking agent is 7 wt% - 10 wt%, and the photoinitiator is 0.5 wt% - 1.5 wt%.

10. A SiOC ceramic, characterized in that, Prepared by using the femtosecond laser preparation method of SiOC ceramic according to any one of claims 1 - 9.

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