A two-photon photoresist capable of secondary engraving, its preparation method, and its applications.

Abstract

This invention discloses a two-photon photoresist capable of secondary engraving, its preparation method, and its applications, belonging to the field of polymer chemical materials technology. The two-photon photoresist provided by this invention comprises disulfide-bonded acrylate, an active crosslinking agent, a long-wavelength two-photon initiator, a single-photon photoalkali agent, dithiothreitol as a dormant reducing agent, and N,N-dimethylformamide as a solvent. It achieves subtractive processing using a second low-energy continuous 405nm laser, building upon the initial femtosecond additive manufacturing process. Under the action of the continuous laser, the single-photon photoalkali agent decomposes and releases alkaline substances, deprotonating dithiothreitol and reducing and opening the disulfide bonds in the disulfide-bonded acrylate, thereby decomposing the already crosslinked and cured photoresist and removing it during development, achieving the purpose of secondary engraving. Simultaneously, this two-photon photoresist can be quickly and easily removed in an alkaline aqueous solution, making it environmentally friendly, with a removal rate of up to 100%.

Description

Technical Field

[0001] This invention relates to the field of polymer chemical materials technology, and more specifically, to a dithiothreitol-based re-etchable two-photon photoresist, its preparation method, and its application. Background Technology

[0002] In recent years, femtosecond laser direct writing technology has developed rapidly. Leveraging its high precision and 3D processing capabilities, it has found wide application in fields such as optical devices, bioengineering, and micro / nano electromechanical systems. The principle of femtosecond laser direct writing technology is based on the nonlinear interaction between photoresist and femtosecond pulses, where the photoresist is crucial to the direct writing performance and processing capabilities of the femtosecond laser.

[0003] Femtosecond laser direct-write photoresist, also known as two-photon photoresist, is currently dominated by acrylate systems. Its composition typically includes two-photon initiators, resin, and active monomers. Recent literature has reported various two-photon initiators and two-photon photoresist formulations. For example, the paper "From Light to Structure: Photo Initiators for Radical Two Photon Polymerization" reviews multiple systems of high-performance two-photon initiators, aiming to improve the sensitivity and direct-write accuracy of photoresists. Regarding photoresist formulations, the paper "Sensitive Photoresists for Rapid Multiphoton 3D Laser Micro-and Nanoprinting" summarizes and compares numerous two-photon photoresist formulations, primarily aiming to identify which resin composition structure is more suitable for rapid direct-write processing.

[0004] For specific application scenarios, patents CN115755525A and CN114326295A report two-photon photoresists suitable for the fabrication of optical and microelectronic devices, respectively. In addition, numerous biocompatible and stimulus-responsive two-photon photoresists have also been reported.

[0005] However, currently available two-photon photoresists lack the capability for secondary engraving. This is because, after cross-linking polymerization and curing, two-photon photoresists are difficult to further undergo femtosecond laser direct writing subtractive processing, thus limiting their malleability and application in certain specialized fields. Furthermore, after most two-photon photoresists have been used, the process of removing or demolding them is often time-consuming and labor-intensive, with a low removal rate, which affects the yield of pattern transfer.

[0006] Therefore, in order to address the above problems, there is an urgent need to develop a two-photon photoresist that can be engraved a second time. This two-photon photoresist has the ability to be engraved a second time and can also be removed and demolded through alkaline treatment, thereby ensuring the yield of pattern transfer. Summary of the Invention

[0007] 1. Technical problems to be solved

[0008] To address the problems existing in the prior art, the first objective of this invention is to provide a two-photon photoresist capable of secondary engraving, comprising disulfide acrylate, an active crosslinking agent, a long-wavelength two-photon initiator, a single-photon photoalkali agent, dithiothreitol as a dormant reducing agent, and N,N-dimethylformamide as a solvent. The second objective of this invention is to provide a method for preparing this two-photon photoresist, by fully dissolving the long-wavelength two-photon initiator, single-photon photoalkali agent, and dormant reducing agent in a solvent, then adding disulfide acrylate and the active crosslinking agent, stirring thoroughly, and filtering to remove impurities, thereby obtaining the target product, the two-photon photoresist. The third objective of this invention is to provide applications of this two-photon photoresist for femtosecond processing and secondary engraving of the two-photon photoresist, enabling the decomposition of the already crosslinked and cured photoresist and its removal during development, thereby achieving the purpose of secondary engraving. It can achieve photoresist removal and demolding through simple alkali treatment, ensuring a high yield of pattern transfer.

[0009] 2. Technical Solution

[0010] To solve the above problems, the present invention adopts the following technical solution.

[0011] A two-photon photoresist capable of secondary engraving comprises, by weight percentage, 20-50 wt% disulfide acrylate (A), 40-70 wt% active crosslinking agent (B), 0.1-1 wt% long-wavelength two-photon initiator (C), 1-5 wt% single-photon photoalkali agent (D), and 2-8 wt% dormant reducing agent (E), with the remainder being solvent (F); wherein the solvent (F) is used as a dissolving component and a solvent for adjusting the viscosity of the photoresist formulation.

[0012] Furthermore, the disulfide acrylate (A) is selected from one or both of formulas (A-1) and (A-2), the structural formulas of which are as follows:

[0013]

[0014] Furthermore, the active crosslinking agent (B) is at least one of pentaerythritol tetraacrylate (B-1) and trimethylolpropene triacrylate (B-2).

[0015] Furthermore, the long-wavelength two-photon initiator (C) is an organic molecule containing electron donor and acceptor and a conjugated structure. The long-wavelength two-photon initiator (C) is selected from one or both of formulas (C-1) and (C-2), and the structural formulas of formulas (C-1) and (C-2) are as follows:

[0016]

[0017] Furthermore, the single-photon photoalkali agent (D) is selected from one or both of tetraphenylborone quaternary ammonium salt (D-1) and aromatic ketone quaternary ammonium salt (D-2), the dormant reducing agent (E) is dithiothreitol (abbreviated as DTT), and the solvent (F) is N,N-dimethylformamide (abbreviated as DMF).

[0018] Furthermore, disulfide acrylates (A) account for 30-40 wt% of the total.

[0019] Furthermore, the active crosslinking agent (B) accounts for 50-60 wt% of the total amount.

[0020] Furthermore, the long-wavelength two-photon initiator (C) accounts for 0.2-0.5 wt% of the total.

[0021] Furthermore, single-photon photoalkali (D) accounts for 2-4 wt% of the total.

[0022] Furthermore, the dormant reducing agent (E) accounts for 4-6 wt% of the total.

[0023] Furthermore, the solvent (F) accounts for 1-8 wt% of the total.

[0024] Furthermore, the photoresist removal method includes the following steps: immersing the photoresist to be removed in a weakly alkaline aqueous solution and heating it; after immersion, removing the photoresist after removal and rinsing it clean with water.

[0025] Furthermore, in the photoresist removal method, the pH value is controlled at 7-9, the temperature is raised to 25-40℃, and the photoresist is soaked for 20-30 minutes, depending on its properties.

[0026] Furthermore, in the photoresist removal method, the pH value is 8, the temperature is raised to 30°C, and the photoresist is soaked for 30 minutes.

[0027] According to a two-photon photoresist that can be etched twice, a method for preparing a two-photon photoresist that can be etched twice includes the following steps: Step 1, dissolving a long-wavelength two-photon initiator (C), a single-photon photoalkali (D), and a dormant reducing agent (E) in a solvent (F) in a yellow light chamber according to the stated mass percentage ratio; Step 2, adding disulfide bond acrylate (A) and an active crosslinking agent (B) to the mixture obtained in Step 1 according to the stated mass percentage ratio, stirring under dark conditions, and filtering with a filter membrane after stirring to remove impurities, thereby obtaining the target product, the two-photon photoresist.

[0028] Furthermore, in step two, the mixture is stirred in the dark for 3-5 hours, and the pore size of the filter membrane is 0.2-0.3 μm.

[0029] Furthermore, in step two, the mixture is stirred for 4 hours in the dark, and the pore size of the filter membrane is 0.25 μm.

[0030] According to a two-photon photoresist that can be engraved twice, the application of a two-photon photoresist that can be engraved twice, for femtosecond processing, and the secondary engraving of the two-photon photoresist.

[0031] Furthermore, the femtosecond processing includes the following steps: applying the photoresist to be processed onto a clean glass slide, controlling the power and speed of the femtosecond laser according to the properties of the photoresist, and performing two-photon processing on the photoresist using a femtosecond laser with a wavelength of 500-850nm.

[0032] Furthermore, in the femtosecond processing, a femtosecond laser with a wavelength of 800nm ​​is used to perform two-photon processing on the photoresist.

[0033] Furthermore, the secondary engraving adopts the following steps: First, after the primary engraving process is completed, the glass slide carrying photoresist is immersed in propylene glycol methyl ether acetate and left to stand. After standing, it is rinsed with isopropanol and dried. Second, the product obtained in the first step is kept at a water temperature and immersed in water. After immersion, it is taken out and directly engraved with a continuous laser with a wavelength of 350-450nm. Third, after the secondary engraving is completed, the obtained secondary engraved photoresist is immersed in propylene glycol methyl ether acetate and left to stand. Then it is rinsed with isopropanol and dried to obtain the secondary engraved micro-nano structure.

[0034] Furthermore, in the first step, the glass slide carrying photoresist is immersed in propylene glycol methyl ether acetate and left to stand for 5-10 minutes; in the second step, the product obtained in the first step is soaked in water for 25-40 minutes, maintaining the water temperature at 25-50℃, and then subjected to secondary engraving using a continuous laser with a wavelength of 405nm; in the third step, the obtained secondary engraved photoresist is immersed in propylene glycol methyl ether acetate and left to stand for 3-10 minutes.

[0035] Furthermore, in the first step, the glass slide carrying photoresist is immersed in propylene glycol methyl ether acetate and left to stand for 8 minutes; in the second step, the product obtained in the first step is soaked in water for 30 minutes, maintaining the water temperature at 30°C; in the third step, the obtained secondary etched photoresist is soaked in propylene glycol methyl ether acetate and left to stand for 5 minutes.

[0036] As a further explanation of the reaction route of the present invention, when the photoresist of the present invention is used for femtosecond laser direct writing, the long-wavelength two-photon initiator (C) contained in the photoresist provided by the present invention has good absorption ability for long-wavelength femtosecond lasers. Under the excitation of the long-wavelength femtosecond laser, the long-wavelength two-photon initiator (C) generates active free radicals to initiate the cross-linking and curing of disulfide acrylate (A) and active cross-linking agent (B), thereby realizing the femtosecond laser direct writing of micro and nano structures.

[0037] As a further explanation of the reaction route of the present invention, when the photoresist of the present invention is used for secondary engraving, after the first engraving, the single-photon photoalkali agent (D) contained in the photoresist provided by the present invention decomposes and releases alkaline substances under the action of continuous laser, deprotonating the dormant reducing agent (E), thereby activating the dormant reducing agent (E) and making it an activated reducing agent (E1) with greatly improved reducing properties; the activated reducing agent (E1) reduces and opens the disulfide bonds in the disulfide bond acrylate (A), thereby decomposing the already cross-linked and cured photoresist and removing it during development, thus achieving the purpose of secondary engraving.

[0038] Dithiothreitol (DTT), which acts as a dormant reducing agent (E), has the following structural formula and mechanism of action:

[0039]

[0040] 3. Beneficial effects

[0041] Compared with the prior art, the advantages of this invention are:

[0042] (1) The present invention provides a two-photon photoresist based on dithiothreitol that can be engraved twice. It has the ability to be engraved twice. It can be further processed by using another low-energy continuous laser to perform subtractive processing on the basis of the first femtosecond additive manufacturing. Under the action of the continuous laser, the single-photon photoalkali contained in the two-photon photoresist decomposes and releases alkaline substances, which activates the dormant reducing agent. The activated reducing agent reduces and opens the disulfide bonds in the disulfide acrylate, thereby decomposing the already cross-linked and cured photoresist and removing it during development, thus achieving the purpose of secondary engraving. This gives it a unique advantage for processing special structures.

[0043] (2) The present invention provides a two-photon photoresist based on dithiothreitol that can be engraved twice, which has excellent resist removal performance. Since the photoresist provided by the present invention uses disulfide bond acrylate A, which contains a large number of disulfide bonds, it can be easily reduced to two mercapto groups by deprotonated dithiothreitol during the resist removal process, thereby quickly destroying the polymer network and achieving the purpose of resist removal. This solves the problem of difficult resist removal in traditional acrylate system and epoxy system.

[0044] (3) The present invention provides a two-photon photoresist based on dithiothreitol that can be engraved twice. During the removal process, the sample only needs to be immersed in a weakly alkaline aqueous solution. There is no need to use toxic and harmful organic solvents, nor is there any need for ultrasonic stripping or reactive ion etching. It is green, environmentally friendly, simple and easy to implement. Attached Figure Description

[0045] Figure 1 The two-photon photoresist in Embodiment 6 of the present invention is a femtosecond laser-processed line array under different laser powers and speeds;

[0046] Figure 2 The secondary engraving lines of the two-photon photoresist in Embodiment 6 of the present invention;

[0047] Figure 3 The femtosecond laser direct-write lines of the two-photon photoresist in Embodiment 6 of the present invention;

[0048] Figure 4 The image shows the morphology of the femtosecond laser direct-write lines of the two-photon photoresist in Embodiment 6 of the present invention after 10 minutes of resist removal.

[0049] Figure 5 The image shows the morphology of the femtosecond laser direct-write lines of the two-photon photoresist in Embodiment 6 of the present invention after 20 minutes of resist removal. Detailed Implementation

[0050] The present invention will be further described below with reference to specific embodiments and accompanying drawings. Those skilled in the art should understand that the specific descriptions below are illustrative rather than restrictive and should not be used to limit the scope of protection of the present invention.

[0051] Unless otherwise specified, the methods used in the following embodiments are conventional methods.

[0052] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0053] Examples 1-8: Preparation of Two-Photonic Photoresists

[0054] In a yellow light chamber, long-wavelength two-photon initiators (C), single-photon photoalkalis (D), and dithiothreitol (DTT) as a dormant reducing agent (E) were fully dissolved in N,N-dimethylformamide (DMF) as a solvent (F). Then, disulfide acrylate (A) and active crosslinking agent (B) were added in different proportions. The mixture was stirred continuously for 4 hours in the dark. The mixture was then filtered through a 0.25 μm filter membrane to remove impurities, yielding the target product, a two-photon photoresist. This dithiothreitol-based two-photon photoresist can achieve secondary engraving and easy resist removal.

[0055] Comparative Example 1:

[0056] In the photoluminescence chamber, 50g of pentaerythritol triacrylate, 49g of bisphenol A diacrylate ethoxylate, and 1g of IRGACURE 369 were mixed and stirred thoroughly. The mixture was then filtered through a 0.25μm pore size filter membrane to remove impurities, thus obtaining the photoresist.

[0057] Comparative Example 2:

[0058] Commercial epoxy photoresist SU8 2000.5 was used.

[0059] Experimental Examples 1-8: Femtosecond Laser Processing and Secondary Engraving

[0060] Using the two-photon photoresists obtained in Examples 1-8, the photoresist to be processed was drop-coated onto a clean glass slide, and two-photon processing was performed using an 800nm ​​femtosecond laser. After the femtosecond processing, the glass slide carrying the photoresist was immersed in propylene glycol methyl ether acetate and left to stand for 8 minutes, then rinsed with isopropanol and dried. Then it was soaked in water for 30 minutes, maintaining a water temperature of 30°C. After soaking, it was removed and directly engraved using a 405nm continuous laser. After engraving, it was immersed in propylene glycol methyl ether acetate and left to stand for 5 minutes, then rinsed with isopropanol and dried to obtain the micro-nano structure of the two-photon photoresist with secondary engraving.

[0061] Compare with Example 1-2:

[0062] The photoresists used in Comparative Examples 1 and 2 were drop-coated onto clean glass slides and processed using an 800nm ​​femtosecond laser. After the femtosecond processing, the glass slides containing the photoresist were immersed in propylene glycol methyl ether acetate and left to stand for 8 minutes, then rinsed with isopropanol and dried. After that, they were soaked in water for 30 minutes at a temperature of 30°C. After soaking, they were removed and directly engraved using a 405nm continuous laser. After engraving, they were immersed in propylene glycol methyl ether acetate and left to stand for 5 minutes, then rinsed with isopropanol and dried.

[0063] Experimental Example 9-16: Test of the resist removal performance of two-photon photoresist

[0064] The two-photon photoresists obtained in Examples 1-8 were spin-coated onto glass slides at 200 r / min, and then dried on a hot stage at 50°C for 5 min. The mass was recorded as M1 using an analytical balance. The two-photon photoresist was then immersed in a weakly alkaline aqueous solution with the pH value controlled at 8, heated to 30°C, and soaked for 30 min. After soaking, the slides were removed, rinsed with clean water, dried, and then dried on a hot stage at 80°C for 10 min. The mass was recorded as M2 using an analytical balance. The resist removal rate Rp = (M1-M2) / M1 was calculated.

[0065] Compare with Example 3-4:

[0066] The photoresists used in Comparative Examples 1-2 were spin-coated onto glass slides at 200 r / min, then dried on a hot stage at 50℃ for 5 min, and the mass was recorded as M1 using an analytical balance. The slides were then immersed in an alkaline aqueous solution with the pH value controlled at 8, heated to 30℃, and soaked for 30 min. After soaking, the slides were removed, rinsed with clean water, dried, and then dried on a hot stage at 80℃ for 10 min, and the mass was recorded as M2 using an analytical balance. The photoresist removal rate Rp = (M1-M2) / M1 was calculated.

[0067] The composition ratios of the photoresists obtained in Examples 1-8, the secondary engraving capabilities measured in Examples 1-8, and the resist removal rates Rp measured in Examples 9-16, as well as the composition ratios of the photoresists obtained in Comparative Examples 1-2, the secondary engraving capabilities measured in Comparative Examples 1-2, and the resist removal rates Rp measured in Comparative Examples 3-4, are combined to form the table: Composition Ratios and Technical Indicators of Two-Photonic Photoresists (the "+" in the table indicates that the photoresist has secondary engraving capabilities, and the more "+" signs, the stronger the secondary engraving capabilities).

[0068]

[0069]

[0070] Table: Composition and Technical Specifications of Two-Photonic Photoresists

[0071] The results show that, by arbitrarily adjusting the content of each component in Examples 1-8, the obtained two-photon photoresists can all undergo femtosecond laser processing and secondary engraving, proving the effectiveness of the technology provided by the present invention. Among them, the femtosecond laser processing capability of the two-photon photoresist obtained in Example 6 under different laser powers and speeds is as follows: Figure 1 As shown; Figure 1Images were taken using an electron microscope manufactured by ZEISS. Detailed parameters: accelerating voltage (EHT) = 3.00 kV, working distance (WD) = 4.4 mm, magnification (Mag) = 400X, electron beam scanning area width (Width) = 285.8 μm, detector (Signal A) = SE2.

[0072] As can be seen from Examples 1-8, the secondary etching capability of two-photon photoresist is mainly determined by the content of disulfide bond acrylate A, single-photon photoalkali agent D, and dithiothreitol E:

[0073] As the total content of disulfide bond acrylate A increases, the disulfide bond content in the cured structure increases. Under the action of continuous laser, the single-photon photoalkali agent D decomposes and releases alkaline substances, deprotonates dithiothreitol (DTT), thereby reducing and opening the disulfide bonds in disulfide bond acrylate A, making the cured structure more susceptible to damage and thus removed by secondary development to obtain better secondary engraving ability.

[0074] Among them, the single-photon photoalkali agent D is a prerequisite for ensuring the activation of dithiothreitol (DTT). A low total content of single-photon photoalkali agent D will result in the inability of dithiothreitol (DTT) to be completely deprotonated, thus making it difficult to fully exert the effect of reducing disulfide bond acrylate A. As can be seen from Examples 1-8, the amount of single-photon photoalkali agent D must be increased in sync with dithiothreitol (DTT) in order to improve the secondary engraving ability of the formulation. However, the traditional two-photon photoresists given in Comparative Examples 1-2 do not have the secondary engraving ability.

[0075] Using the preferred embodiment 6 as the research object, a secondary engraving technique was used to perform subtractive processing on the cured lines. A 405nm continuous laser was used to scan the edges of the cured lines. Figure 2 As can be seen, the width of the lines is significantly reduced after the second engraving, which proves that the photoresist formula provided by this invention has excellent secondary engraving capabilities.

[0076] Furthermore, as can be seen from Examples 1-8, the two-photon photoresist provided by the present invention has excellent resist removal performance, with the optimal formulation achieving a resist removal rate of 100%. Compared to the traditional two-photon photoresist with a resist removal rate Rp of 0 provided by Comparative Examples 1-2, the two-photon photoresist provided by the present invention is prepared using disulfide bond acrylate A. Since disulfide bond acrylate A contains a large number of disulfide bonds, it can be easily reduced to two thiol groups by deprotonated dithiothreitol (DTT) during the resist removal process, thereby rapidly destroying the polymer network and achieving the purpose of resist removal.

[0077] like Figure 3-5 As shown, the formulation of preferred embodiment 6 is used as the research object. Figure 3 The lines obtained by direct writing of two-photon photoresist using a femtosecond laser in Example 6 are shown. Figure 3 Images were taken using an electron microscope manufactured by ZEISS. Detailed parameters: accelerating voltage (EHT) = 2.00 kV, working distance (WD) = 5.4 mm, magnification (Mag) = 11.86 KX, electron beam scanning area width (Width) = 9.636 μm, detector (SignalA) = SE2.

[0078] After 10 minutes of desizing, the lines gradually become thinner. Figure 4 ), Figure 4 Images were taken using an electron microscope manufactured by ZEISS. Detailed parameters: accelerating voltage (EHT) = 2.00 kV, working distance (WD) = 5.4 mm, magnification (Mag) = 12.63 KX, electron beam scanning area width (Width) = 9.053 μm, detector (SignalA) = SE2.

[0079] After 20 minutes of adhesive removal, the linear structure was almost completely destroyed. Figure 5 ), and completely remove it after 30 minutes of desizing. Figure 5 Images were taken using an electron microscope manufactured by ZEISS. Detailed parameters: accelerating voltage (EHT) = 2.00 kV, working distance (WD) = 5.4 mm, magnification (Mag) = 10.80 KX, electron beam scanning area width (Width) = 10.58 μm, detector (Signal A) = InLens.

[0080] In summary, the two-photon photoresist based on dithiothreitol provided by this invention, which is capable of secondary engraving and easy to remove resist, utilizes dithiothreitol acrylate containing a large number of dithio bonds, combined with a single-photon photoalkali agent and dithiothreitol, to enable it to be engraved twice. At the same time, it can achieve resist removal and demolding through alkali treatment, thereby ensuring the yield of pattern transfer and showing great application prospects.

[0081] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A two-photon photoresist that is twice writable, characterized by: The composition, by mass percentage, includes 20-50 wt% disulfide acrylate (A), 40-70 wt% active crosslinking agent (B), 0.1-1 wt% long-wavelength two-photon initiator (C), 1-5 wt% single-photon photoalkali agent (D), and 2-8 wt% dormant reducing agent (E), with the remainder being solvent (F). The solvent (F) is used as a dissolving component and a solvent to adjust the viscosity of the photoresist formulation. The disulfide acrylate (A) is selected from one or both of formulas (A-1) and (A-2), the structural formulas of which are as follows: ； The single-photon photoalkali agent (D) is selected from one or both of tetraphenylborone quaternary ammonium salt (D-1) and aromatic ketone quaternary ammonium salt (D-2), and the dormant reducing agent (E) is dithiothreitol.

2. The two-time writable two-photon photoresist according to claim 1, wherein: The active crosslinking agent (B) is at least one of pentaerythritol tetraacrylate (B-1) and trimethylolpropene triacrylate (B-2).

3. The two-photon photoresist capable of secondary engraving according to claim 1, characterized in that: The long-wavelength two-photon initiator (C) is an organic molecule containing an electron donor and acceptor and a conjugated structure. The long-wavelength two-photon initiator (C) is selected from one or both of formulas (C-1) and (C-2). The structural formulas of formulas (C-1) and (C-2) are as follows: 。 4. The two-photon photoresist capable of secondary engraving according to claim 1, characterized in that: The solvent (F) is N,N-dimethylformamide.

5. The two-photon photoresist capable of secondary engraving according to claim 1, characterized in that: The photoresist removal method includes the following steps: Immerse the photoresist to be removed in a weakly alkaline aqueous solution and heat it. After immersion, remove the photoresist and rinse it with clean water.

6. A method for preparing a two-photon photoresist capable of secondary engraving according to any one of claims 1-5, characterized in that: Includes the following steps: Step 1: Dissolve the long-wavelength two-photon initiator (C), single-photon photoalkali (D), and dormant reducing agent (E) in solvent (F) in the yellow light chamber according to the stated mass percentage ratio. Step 2: Add disulfide acrylate (A) and active crosslinking agent (B) to the mixture obtained in Step 1 according to the mass percentage ratio, stir under dark conditions, and filter with a filter membrane to remove impurities after stirring to obtain the target product, two-photon photoresist.

7. The application of a two-photon photoresist capable of secondary engraving according to any one of claims 1-5, characterized in that: Used for femtosecond processing and secondary engraving of two-photon photoresist.

8. The application of the two-photon photoresist capable of secondary engraving according to claim 7, characterized in that: The femtosecond processing includes the following steps: The photoresist to be processed is dropped onto a clean glass slide. The power and speed of the femtosecond laser are controlled according to the properties of the photoresist used, and the photoresist is processed by two-photon processing using a femtosecond laser with a wavelength of 500-850nm.

9. The application of the two-photon photoresist capable of secondary engraving according to claim 7, characterized in that: The secondary engraving process involves the following steps: The first step is to immerse the glass slide containing photoresist in propylene glycol methyl ether acetate and let it stand. After standing, rinse it with isopropanol and blow it dry. The second step is to keep the product obtained in the first step in water at a constant temperature and then remove it and use a continuous laser with a wavelength of 350-450nm for secondary engraving. The third step is to immerse the obtained photoresist in propylene glycol methyl ether acetate and let it stand. Then rinse it with isopropanol and blow it dry to obtain the micro-nano structure etched in the second step.

Images