CN113064325A - Composite photoresist for preparing multi-material three-dimensional micro-nano structure and application thereof - Google Patents
Composite photoresist for preparing multi-material three-dimensional micro-nano structure and application thereof Download PDFInfo
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- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
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Abstract
The invention belongs to the technical field of laser direct writing, and particularly relates to a composite photoresist for preparing a multi-material three-dimensional micro-nano structure and application thereof. The method comprises the steps of uniformly mixing a free radical monomer, a free radical photoinitiator, a free radical crosslinking agent, a cationic monomer and a cationic photoinitiator to obtain a composite photoresist, focusing femtosecond laser in the composite photoresist, and controlling the wavelength, power and processing speed of the femtosecond laser to respectively polymerize and crosslink a free radical system and a cationic system, thereby forming three-dimensional micro-nano structures of different materials. According to the method, high-precision material integration of multiple components in the same micro-nano structure can be realized only by using one photoresist precursor, and the method is simple in operation steps only through one development process. Meanwhile, the control method is stable and simple, other components are not required to be added, and the micro-nano laser 3D printing device can be directly applied to most micro-nano laser 3D printing devices.
Description
Technical Field
The invention belongs to the technical field of laser direct writing, and particularly relates to a composite photoresist for preparing a multi-material three-dimensional micro-nano structure and application thereof.
Background
In recent years, the demand for miniaturization and integration of photoelectric functional devices is increasing day by day, and micro-nano processing technology is developed for synthesizing, processing and assembling materials under the micro-nano scale and further integrating the materials into micro-nano devices. The existing micro-nano additive manufacturing technology comprises laser direct writing, nano imprinting, electrostatic spinning, ink-jet printing and the like, wherein the femtosecond laser two-photon polymerization direct writing technology is widely concerned by researchers at home and abroad by virtue of the advantages of high processing resolution, true three-dimensional manufacturing and the like. The femtosecond laser two-photon polymerization direct writing mechanism mainly utilizes a photoinitiator in a femtosecond laser induced precursor to carry out two-photon absorption to generate free radicals, the generated free radicals and monomers in the precursor carry out photopolymerization to form a polymer insoluble in a solvent, and the preparation of a micro-nano three-dimensional structure is realized by controlling the moving path of a laser spot. At present, the femtosecond laser two-photon polymerization direct writing technology is widely applied to the fields of photonic crystals, micro-nano sensors, cell scaffolds and the like. With the continuous research on micro-nano devices, researchers find that three-dimensional manufacturing of multiple materials is often required to be integrated in many scenes, for example, materials with different strain characteristics are required to be integrated in an intelligent responsive device to realize complex actions, different materials are required to be utilized in a cell scaffold to realize selective adsorption on specific cells, and materials in different areas are required to have different refractive indexes in a micro-nano optical device. However, similar to many three-dimensional fabrication techniques based on photopolymerization (e.g., stereolithography), even if femtosecond laser light is applied to a photoresist in which a plurality of different reactive monomers are present, radicals generated by photopolymerization may react with all the different monomers to form a copolymer cross-linked product, resulting in that only one material can be finally obtained. Although this high reactivity improves the direct writing efficiency, it also introduces an inevitable problem that it is difficult to fabricate micro-nano structures composed of a plurality of material components. Therefore, a multi-material micro-nano 3D printing and forming manufacturing method based on two-photon polymerization needs to be developed, and the application range of the method in the field of micro-nano functional devices is widened.
At present, the multi-material femtosecond laser two-photon polymerization direct writing technology mainly comprises a sequential manufacturing method, a layered stacking method and a microfluid method. The most common technique is sequential fabrication, which is based on the principle of first direct writing and developing a first photoresist, then dropping a second photoresist and three-dimensional alignment of a processing platform, and then completing the direct writing and developing of the second photoresist. Benjamin et al (Benjamin Richter et al, three-Dimensional microscopic examination affected Surface chemistry. advanced Materials 25(42)6117-6122) used this technique to prepare multi-material cell scaffolds. The technology needs to go through a plurality of direct-write manufacturing cycles, which inevitably introduces defects and impurities into the product, and at the same time, the processing efficiency is seriously reduced, and the manufacturing cost is increased; in addition, the alignment marks need to be realigned in three dimensions after each photoresist replacement, and alignment errors of the alignment marks affect the structure precision. The microfluid method is characterized in that a microfluid chamber is constructed, the chamber is combined with a gas pumping device, different types of photoresists and developing solutions are controlled to be conveyed to a direct writing area by adjusting the pressure of gas, and a multi-material structure can be obtained by direct writing and developing for multiple times. Mayer et al (Mayer F et al, multimaterial 3D laser microprocessing using an integrated microfluidic system science Advances 5(2)) use this method to eliminate errors from repeated positioning. But the microfluidic device is complicated and the technology still needs multiple times of development, which is difficult to be applied to the high-viscosity photoresist, and the material selection range of multi-material direct writing is greatly limited. The layered stacking method is to stack two kinds of photoresist together in advance, and then to directly write the photoresist of different layers, so as to obtain the structure with different materials at the upper and lower layers. Schwaerzle et al (Schwaerzle D et al. Polymer Microstructures through Two-Photon crosslinking. advanced materials 29(39)1703469.1-1703469.6) used this method to prepare hydrophilic-hydrophobic bilayer material structures. This method requires the use of a relatively viscous photoresist to form the stack in the Z-axis direction, and therefore less photoresist is used. Meanwhile, the technology can only realize dual-material integration in the Z-axis direction, and the flatness between two interfaces is difficult to control, so that the application of the technology in the field of multi-material three-dimensional integration is limited. In summary, the existing multi-material femtosecond laser two-photon polymerization direct writing technology has certain limitations on the types of photoresists or the integrated structures of multiple materials, and meanwhile, the process is complicated and the equipment is complex. At present, a process technology capable of realizing integration of a multi-material complex three-dimensional micro-nano structure in a single direct writing period is lacked.
In addition, the existing preparation method respectively adopts cationic polymerization and free radical polymerization to obtain a three-dimensional micro-nano structure device containing two materials, the problem of poor connectivity among multiple materials of the multi-material three-dimensional micro-nano structure device still exists, and the layering phenomenon is shown among different material layers, so that the application performance of the multi-material three-dimensional micro-nano structure is influenced. In order to solve the problem, a material capable of performing both radical polymerization and cationic polymerization is usually added into a photoresist in the existing method, and the material can react during the two polymerizations and is equivalent to a linking agent, so as to solve the problem that the material performance is poor due to poor connectivity between different materials, however, due to the introduction of the linking agent material, an epoxy functional group which cannot react exists in a network during the radical polymerization, and the photocuring speed is reduced.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a preparation method of a multi-material three-dimensional micro-nano structure, and aims to solve the problems that multiple times of positioning and multiple times of developing are needed to manufacture the multi-material three-dimensional micro-nano structure, and the integrated structure is limited.
In order to achieve the aim, the invention provides a composite photoresist for preparing a multi-material three-dimensional micro-nano structure, which comprises a free radical system component and a cation system component, wherein the free radical system component comprises a free radical monomer, a free radical photoinitiator and a free radical crosslinking agent, and the cation system component comprises a cation monomer and a cation photoinitiator;
the free matrix system component and the cation system component are respectively used for polymerizing and crosslinking under the action of focused laser beams with different wavelengths to form a three-dimensional micro-nano structure containing different materials, wherein the multi-material three-dimensional micro-nano structure comprises a free radical polymer formed by polymerizing and crosslinking the free matrix system component under the action of a first focused laser beam, namely a first material; also included are copolymers formed by the polymerization crosslinking of the free radical system component and the cationic system component together under the action of a second focused laser beam, i.e., second materials.
Preferably, the free radical monomer is an acrylic resin monomer; the free radical photoinitiator is Irg.819 or a phenylphosphoryl initiator, and the free radical crosslinking agent is a multifunctional acrylate crosslinking agent or a multifunctional methacrylate crosslinking agent; the cationic monomer is epoxy cationic monomer; the cation cross-linking agent is a triaryl sulfonium hexafluoroantimonate mixture or triaryl sulfonium salt.
Preferably, the compound photoresist comprises the following components in proportion: radical monomer, radical photoinitiator, radical crosslinking agent, cationic monomer and cationic photoinitiator (0.1-0.3) ml, (5-10) mg, (0.1-0.3) ml, (0.6-0.7) g, (40-80) mu l.
Further preferably, the compound photoresist comprises the following components in proportion: radical monomer, radical photoinitiator, radical crosslinking agent, cationic monomer, cationic photoinitiator and (5-10) mg, 0.3ml, (0.6-0.7) g and (40-80) mu l. By increasing the relative content of the free radical crosslinking agent in the free matrix system components, the layering phenomenon between material interfaces caused by large difference of mechanical properties of two materials in the multi-material three-dimensional micro-nano structure is overcome, and the forming quality of the multi-material three-dimensional micro-nano structure is improved.
Preferably, the composite photoresist is prepared by fully mixing the free radical monomer, the free radical photoinitiator, the free radical crosslinking agent, the cationic monomer and the cationic photoinitiator under the condition of keeping out of the sun.
Further preferably, the sufficient mixing is magnetic stirring, the stirring condition is at least 12 hours, and the stirring speed is 600-1000 rpm/min.
According to another aspect of the invention, the composite photoresist is applied to the preparation of a multi-material three-dimensional micro-nano structure by femtosecond laser two-photon polymerization direct writing.
According to another aspect of the invention, a method for preparing a multi-material three-dimensional micro-nano structure by using the composite photoresist is provided, which comprises the following steps:
s1, spin-coating the composite photoresist on a substrate;
s2, focusing a first femtosecond laser beam on a region of the composite photoresist needing to form a first material, adjusting the wavelength and power of the laser beam to enable components of a free radical system to be polymerized and crosslinked, and directly writing to form the first material;
s3, focusing a second femtosecond laser beam on a region of the composite photoresist needing to form a second material, adjusting the wavelength and the power of the laser beam to enable a cation system component and a free radical system component to be subjected to polymerization crosslinking simultaneously, and forming the second material by direct writing;
and S4, baking and developing the composite photoresist after the direct writing is finished to obtain the multi-material three-dimensional micro-nano structure.
Preferably, in step S2, the first femtosecond laser beam has a wavelength of 780 to 1030nm, a power of 6 to 100mW, and a laser processing speed of 0.01 to 20 mm/S; in the step S3, the second femtosecond laser beam has a wavelength of 690-750 nm, a power of 10-80 mW, and a laser processing speed of 0.05-20 mm/S.
Preferably, in step S1, the composite photoresist is spin-coated on a substrate and placed on a hot stage for pre-baking, wherein the pre-baking is specifically performed by baking the substrate spin-coated with the composite photoresist at 25-65 ℃ for 0-5 min, and then baking the substrate at 65-95 ℃ for 5-20 min; in the step S3, the specific method of the thermal baking is to bake the composite photoresist after the direct writing is finished for 0-5 min at 25-65 ℃, and then bake for 10-30 min at 65-95 ℃.
Generally, compared with the prior art, the above technical solution conceived by the present invention has the following beneficial effects:
(1) the invention provides a novel composite photoresist which comprises a cation system component and a free matrix system component, specifically comprises a free radical monomer, a free radical photoinitiator, a free radical crosslinking agent, a cation monomer and a cation photoinitiator, and can be used for manufacturing a multi-material three-dimensional micro-nano structure by optimizing the types and the proportions of the components to obtain a photoresist material with uniform texture and proper fluidity and viscosity.
(2) The composite photoresist for preparing the multi-material three-dimensional micro-nano structure provided by the invention is prepared from various materials, has small limitation, and greatly expands the design dimension and material range of the micro-nano structure.
(3) According to the composite photoresist for preparing the multi-material three-dimensional micro-nano structure, the free radical system and the cation system can be respectively polymerized and crosslinked under the action of focused laser beams with different wavelengths and powers to form three-dimensional structures of different materials, and the composite photoresist can integrate materials with different fluorescence absorption properties and mechanical properties into one micro-nano three-dimensional structure, so that the physicochemical properties of different areas of a forming structure can be accurately controlled.
(4) According to the preparation method of the multi-material three-dimensional micro-nano structure, selective curing forming of different product components can be achieved by controlling laser parameters, multi-component high-precision material integration can be achieved in the same micro-nano structure by only using one photoresist precursor, the operation is simple and rapid through only one developing process, the method gets rid of the limitation of a single 3D printing material, and the advantages of high precision, high efficiency and rapid forming of a complex three-dimensional structure in laser 3D printing can be fully exerted.
(5) According to the preparation method of the multi-material three-dimensional micro-nano structure, the relative content of the free radical component crosslinking agent in the composite photoresist system is increased, so that the free radical polymerization crosslinking agent exists on the surfaces of the copolymer of the free radical system and the cationic system, the copolymer can form covalent crosslinking with the first material, namely a free radical polymerization product, the layering phenomenon of the materials with larger rigidity difference of the two network structures is overcome, and the free matrix system in the method can react more completely in the polymer network without reducing the photocuring speed.
(6) The preparation method of the multi-material three-dimensional micro-nano structure provided by the invention has a stable and simple control means, does not need to add other components, and can be directly used for most micro-nano laser 3D printing devices.
Drawings
Fig. 1 is a schematic diagram of a preparation method of a multi-material three-dimensional micro-nano structure according to an embodiment of the present invention;
fig. 2 is a raman spectrum of the multi-material three-dimensional micro-nano structure prepared in example 1 of the present invention;
fig. 3 is an absorption diagram of a fluorescent dye of a multi-material tai chi structure prepared in example 2 of the present invention, wherein,
FIG. 3A is a design drawing, and FIG. 3B is a fluorescence characteristic diagram;
fig. 4 is a comparison graph of mechanical properties of a multi-material two-layer structure prepared in example 3 of the present invention, wherein fig. 4 shows a design drawing, fig. 4 shows a SEM drawing, and fig. 4 shows a graph of mechanical properties of different layers of the structure;
fig. 5, content b and content a are comparison graphs of layering phenomena between multiple materials of the multi-micro-nano structure prepared in the embodiment 4 and the embodiment 5 of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The invention provides a composite photoresist for preparing a multi-material three-dimensional micro-nano structure, which comprises a free radical system component and a cation system component, wherein the free radical system component comprises a free radical monomer, a free radical photoinitiator and a free radical crosslinking agent; the free matrix system component and the cation system component are respectively used for polymerizing and crosslinking under the action of focused laser beams with different wavelengths and powers to form a micro-nano structure containing different materials, wherein the three-dimensional micro-nano structure comprises a free radical polymer formed by polymerizing and crosslinking the free radical system component under the action of a first focused laser beam, namely a first material; also included are copolymers formed by the polymerization crosslinking of the free radical system component and the cationic system component together under the action of a second focused laser beam, i.e., second materials.
The composite photoresist provided by the invention comprises materials with different fluorescence absorption properties and mechanical properties, and is polymerized and crosslinked under the action of focused laser beams with different wavelengths and powers, so that different materials can be integrated in a three-dimensional micro-nano structure, and the physicochemical properties of different areas of a forming structure can be accurately controlled. The free radical system can independently generate polymerization crosslinking reaction to form a soft material, and the polymerization crosslinking of the cationic system can not be caused in the polymerization process; during the polymerization crosslinking process of the cationic system, the reaction of the free radical system can be simultaneously initiated, so that the cationic system and the free radical system are polymerized and crosslinked together to form a harder material. In addition, the free-radical material in the composite photoresist can absorb fluorescence, and the cationic material is difficult to absorb fluorescence, so that the three-dimensional structure obtained by preparation can be well and visually represented by fluorescent dye dyeing.
The composite photoresist can select various kinds of free matrix system materials and cation system materials according to the design requirements of the micro-nano structure, and has small limitation and wide application range. For example, the free radical monomer can be acrylic resin monomer, the free radical photoinitiator can be Irg.819 or phenylphosphoryl initiator, and the free radical crosslinking agent is multifunctional acrylate crosslinking agent or multifunctional methacrylate crosslinking agent; the cationic monomer is epoxy cationic monomer; the cationic cross-linking agent is a triarylsulfonium hexafluoroantimonate mixture or triarylsulfonium salt. In some embodiments, the free radical monomer is one or more of hydroxyethyl acrylate and hydroxyethyl methacrylate, the free radical photoinitiator is irg.819, the free radical crosslinking agent is one or more of polyethylene glycol diacrylate and pentaerythritol triacrylate, the cationic monomer is one or more of 3, 4-epoxycyclohexylmethyl-3, 4-epoxycyclohexylformate and EPON SU-8 epoxy resin, and the cationic photoinitiator is a triarylsulfonium hexafluoroantimonate mixture or a triarylsulfonium salt.
In some embodiments, the compound photoresist comprises the following components in proportion: radical photoinitiator, radical crosslinking agent, cationic photoinitiator, and (0.1-0.3) ml of (5-10) mg of (0.1-0.3) ml of (0.6-0.7) g of (40-80) ul, preferably (0.1-0.3) ml of (5-10) mg of (0.6-0.7) g of (40-80) ul.
The selection of the types and the proportions of the components in the composite photoresist is particularly critical to the preparation of the multi-material three-dimensional micro-nano structure, and the forming effect and the physical and chemical properties of the micro-nano structure can be influenced. The components in the composite photoresist can be uniformly mixed together, and the composite photoresist has certain fluidity, so that a free radical system and a cation system can smoothly perform polymerization crosslinking reaction, the curing speed is high, and meanwhile, the viscosity of the composite photoresist is not too high, otherwise, the composite photoresist is not convenient to transfer, and the developing effect is not good.
In some embodiments, the composite photoresist is prepared by mixing the radical monomer, the radical photoinitiator, the radical crosslinking agent, the cationic monomer and the cationic photoinitiator under a dark condition, and then performing magnetic stirring and uniform mixing. Preferably, the magnetic stirring condition is that the magnetic stirring is carried out for at least 12 hours at room temperature, and the stirring speed is 600-1000 rpm/min. Because the components in the composite photoresist are various, the components can be well dissolved and uniformly mixed only by fully stirring, and the subsequent curing is facilitated to form an ideal multi-material three-dimensional structure.
The composite photoresist can be applied to femtosecond laser two-photon polymerization direct writing to prepare a multi-material three-dimensional micro-nano structure, the prepared 3D structure has a good forming effect, and the forming effect can be visually represented by fluorescent dyeing.
The embodiment of the invention also provides a preparation method of the multi-material three-dimensional micro-nano structure, which comprises the following steps as shown in figure 1:
s1, spin-coating the composite photoresist on a substrate;
s2, focusing a first femtosecond laser beam on a region of the composite photoresist needing to be formed with a first material, so that a free matrix is subjected to polymerization crosslinking under a first wavelength and a first power, and directly writing to form the first material;
s3, focusing a second femtosecond laser beam on a region, which is required to form a second material, in the composite photoresist, so that a cation system and a free matrix system are subjected to polymerization crosslinking at the same time under the conditions of a second wavelength and a second power, and the second material is formed by direct writing;
and S4, baking and developing the composite photoresist after the direct writing is finished to obtain the multi-material three-dimensional micro-nano structure.
In some embodiments, in step S1, the spin coating method is to spin the photoresist at a speed of 1000 to 3000rpm for 50 to 60 seconds, so that the photoresist is coated on the substrate to form a thin film, which reduces the fluidity of the photoresist and facilitates the subsequent direct writing to be more stable. Preferably, the substrate is used after being pretreated, and the pretreatment specifically comprises the following operations: and sequentially carrying out ultrasonic treatment on the substrate in deionized water and isopropanol for 15-40 min respectively, and then drying at 80-100 ℃. The substrate after being cleaned and dried is cleaner, and the influence of impurities mixed into the photoresist on the laser direct writing effect is avoided. The substrate can be a glass slide commonly used in a microscope system, and can also be a silicon wafer.
In some embodiments, in step S1, the composite photoresist is spin-coated on a substrate and placed on a hot stage for pre-baking, and the pre-baking is specifically performed by baking the substrate spin-coated with the composite photoresist at 65 ℃ for 0-5 min to evaporate low-boiling-point impurities in the photoresist, and then baking the substrate at 95 ℃ for 5-20 min, so that the photoresist and the substrate are combined more firmly, and the direct writing effect is better.
The embodiment of the invention adopts a femtosecond laser two-photon polymerization direct writing system, and the control of the wavelength and the power of the femtosecond laser is crucial in the process of directly writing the multi-material three-dimensional micro-nano structure. In some embodiments, in step S2, the first wavelength is controlled to be not less than 780nm, and the first power is controlled to be 6 to 100mW, preferably 10 to 30mW, so that only the radical system is polymerized and crosslinked, and the cationic system is not polymerized and crosslinked. In the first wavelength range, if the laser power is too high, it is found that a serious thermal effect is generated, and the photoresist is ablated and cannot be polymerized normally. And controlling the second wavelength to be 690-750 nm, the second power to be 10-80 mW, preferably 10-30 mW, so that the cationic system is subjected to polymerization crosslinking, but under the condition, the free radical system can also undergo polymerization crosslinking reaction.
In the laser direct writing process, besides controlling the wavelength and power of the femtosecond laser, the processing speed should be reasonably controlled to ensure the accuracy of the scanning range as much as possible, thereby ensuring good forming effect. In some embodiments, in step S2, during the polymerization crosslinking process of the free radical system only, i.e. when the wavelength and the power of the femtosecond laser are adjusted to the first wavelength and the first power, respectively, the processing speed is controlled to be 0.01-20 mm/S, preferably 0.5-5 mm/S; in the polymerization crosslinking process of both the cation system and the free radical system, namely when the wavelength and the power of the laser femtosecond laser are respectively adjusted to be the second wavelength and the second power, the processing speed is controlled to be 0.05-20 mm/s, preferably 0.5-5 mm/s.
In the process of processing the three-dimensional micro-nano structures of the two materials by adopting the method provided by the embodiment of the invention, the first material formed by direct-writing polymerization of the free matrix system has low network structure rigidity. The second material formed by the co-direct-writing polymerization of the free radical system and the cationic system has high rigidity of a network structure. The difference in mechanical properties is large, and in some embodiments, the difference between the mechanical stiffness of the first material and the mechanical stiffness of the second material is dozens of times. Experiments show that if the control is not good, two materials in the micro-nano structure can have obvious layering phenomenon. By increasing the amount of the free radical component crosslinking agent in the composite photoresist system, the free radical polymeric crosslinking agent exists on the surface of the copolymer of the free radical system and the cationic system, so that the copolymer can form covalent crosslinking with a first material, namely a free radical polymerization product, and the delamination phenomenon of the two materials is overcome.
In some embodiments, in step S3, the post-baking method includes baking the direct-writing composite photoresist at 65 ℃ for 0-5 min, and then baking at 95 ℃ for 10-30 min. The post-baking process promotes the photoresist material to be more fully crosslinked and better shaped. And then, after cooling to room temperature, placing the multi-material three-dimensional micro-nano structure in a developing solution for developing for 0.5-10 min, taking out the multi-material three-dimensional micro-nano structure and drying the multi-material three-dimensional micro-nano structure by using nitrogen.
As shown in fig. 1, monomers of a cation system and a radical system, an initiator and a cross-linking agent are added into a brown reagent bottle, the mixture is uniformly mixed by magnetic stirring to obtain a composite photoresist, the obtained photoresist is spin-coated on a pretreated substrate, and then the substrate is placed on a hot stage for pre-baking. Then, putting the sample obtained by pre-baking into a sample clamp of a femtosecond laser two-photon polymerization direct writing device, adjusting the focal length to focus the femtosecond laser in the photoresist, and setting the laser wavelength, power and processing speed to polymerize and crosslink the free matrix system to form a soft material; the laser wavelength, power and processing speed are reset to enable the free radical system and the cation system to be polymerized and crosslinked to form a hard material. The order of the two crosslinking processes can be changed, and the free radical system and the cation system can be polymerized and crosslinked firstly, and then the free matrix system is polymerized and crosslinked. And then, placing the directly written compound photoresist on a hot table, baking, and finally developing to obtain the target multi-material structure.
The invention relates to a method for preparing an ideal multi-material three-dimensional micro-nano structure, which comprises the steps of optimizing and searching process conditions and parameters for many times and verifying a large number of experiments in order to obtain the ideal multi-material three-dimensional micro-nano structure. According to the preparation method of the multi-material three-dimensional micro-nano structure provided by the embodiment of the invention, multiple materials are prepared in one photoresist through the photo-controlled polymerization reaction, only one step of development is needed, the steps are simple, and the finally obtained three-dimensional micro-nano structure is good in forming effect.
The above technical solution is described in detail below with reference to specific examples.
Example 1
0.3ml of hydroxyethyl acrylate, 0.1ml of polyethylene glycol diacrylate, 10mg of Irg.819, 0.6g of 3, 4-epoxy cyclohexyl methyl-3, 4-epoxy cyclohexyl formate and 50 mu l of a mixture of triaryl sulfonium hexafluoroantimonate are added into a brown reagent bottle and are magnetically stirred at the temperature of 40 ℃ at the speed of 800rpm/min for 24 hours to obtain a uniform photoresist solution. Sequentially carrying out ultrasonic treatment on the substrate in deionized water and isopropanol for 15min respectively, and then drying at 80 ℃. The photoresist was dropped on the dried substrate and the photoresist was spun for 50s at 1000 rpm. And (3) placing the substrate coated with the photoresist on a hot bench, baking at 65 ℃ for 5min, and then baking at 95 ℃ for 10 min. Putting the sample obtained by pre-baking into a sample clamp of a laser direct writing platform, adjusting the focal length to focus femtosecond laser in photoresist, and setting the laser wavelength to 780nm, the power to 22.9mW and the processing speed to 2mm/s to enable a free matrix system to be polymerized and crosslinked to form a soft material; setting the laser wavelength at 690nm, the power at 16.6mW and the processing speed at 0.5mm/s allows both free radical and cationic systems to polymerize and crosslink to form rigid materials. Placing the substrate on a hot table, firstly baking at 65 ℃ for 5min, and then baking at 95 ℃ for 20 min; after cooling to room temperature, the solution was placed in a propylene glycol methyl ether acetate developing solution for 5min, and then taken out and dried with nitrogen.
The directly written sample was subjected to Raman spectroscopy, the result of which is shown in FIG. 2, 790cm-1Is characterized by the peak of 1639cm of epoxy functional group in the cationic monomer-1The peak is a characteristic peak of a carbon-carbon double bond in a free radical monomer, and 1720 is a carbonyl reference peak contained in both the monomers. The samples directly written under 690nm laser show both the epoxy peak and the carbon-carbon double bond peakCertain strength is shown, which indicates that the epoxy monomer and the acrylate are polymerized to form a cationic material; the sample directly written under 780nm laser has no two peaks, which indicates that only acrylate is polymerized to form a free-radical material, so that different material components are directly written under different laser parameters.
Example 2
0.2ml of hydroxyethyl acrylate, 0.2ml of polyethylene glycol diacrylate, 5mg of Irg.819, 0.1g of 3, 4-epoxycyclohexylmethyl-3, 4-epoxycyclohexyl formate, 0.6g of EPON SU-8 epoxy resin and 50. mu.l of a mixture of triarylsulfonium hexafluoroantimonate are added into a brown reagent bottle and stirred magnetically at the speed of 800rpm/min at the temperature of 40 ℃ for 24 hours to obtain a uniform photoresist solution. Sequentially carrying out ultrasonic treatment on the substrate in deionized water and isopropanol for 15min respectively, and then drying at 80 ℃. The photoresist was dropped on the dried substrate and the photoresist was spun for 50s at 2000 rpm. And (3) placing the substrate coated with the photoresist on a hot bench, baking at 65 ℃ for 5min, and then baking at 95 ℃ for 10 min. Loading the sample obtained by pre-baking into a sample clamp of a laser direct writing platform, adjusting the focal length to focus femtosecond laser in photoresist, and directly writing a multi-material Taiji structure shown as a design drawing of a content a in figure 3, wherein the white part in the drawing is set to be 850nm of laser wavelength, 22.1mW of power and 2mm/s of processing speed, so that a free matrix system is polymerized and crosslinked to form a soft material; the black part was set to a laser wavelength of 720nm, a power of 18.0mW and a processing speed of 0.5mm/s, so that both free-radical and cationic systems polymerized and crosslinked to form a rigid material. Placing the substrate on a hot table, firstly baking at 65 ℃ for 5min, and then baking at 95 ℃ for 10 min; after cooling to room temperature, the solution was placed in a propylene glycol methyl ether acetate developing solution for 5min, and then taken out and dried with nitrogen.
And immersing the dried sample into an aqueous solution containing a fluorescent dye rhodamine B, taking out the sample after immersing for 2min, washing the sample with water, drying the sample with nitrogen, and observing the sample by using a two-photon fluorescence microscope. FIG. 3b is a graph showing the fluorescence characteristics of the direct-written structure of this example, wherein the fluorescent dye is absorbed by the direct-written free-radical material under 850nm laser, and is not easily absorbed by the direct-written cationic material under 720nm laser.
Example 3
0.1ml of hydroxyethyl methacrylate, 0.3ml of polyethylene glycol diacrylate, 5mg of Irg.819, 0.1g of 3, 4-epoxycyclohexylmethyl-3, 4-epoxycyclohexyl formate, 0.6g of EPON SU-8 epoxy resin and 60. mu.l of a mixture of triarylsulfonium hexafluoroantimonate are added into a brown reagent bottle and magnetically stirred at 40 ℃ and 800rpm/min for 24 hours to obtain a uniform photoresist solution. Sequentially carrying out ultrasonic treatment on the substrate in deionized water and isopropanol for 15min respectively, and then drying at 80 ℃. The photoresist was dropped on the dried substrate and the photoresist was spun for 50s at 1500 rpm. And (3) placing the substrate coated with the photoresist on a hot bench, baking at 65 ℃ for 5min, and then baking at 95 ℃ for 5 min. Loading the sample obtained by prebaking into a sample clamp of a laser direct writing platform, adjusting the focal length to focus femtosecond laser in photoresist, and directly writing a multi-material double-layer structure shown as a design drawing of a content a in figure 4, wherein the white part of the inner layer in the drawing is set to be 780nm of laser wavelength, 14.0mW of power and 1mm/s of processing speed, so that a free matrix system is polymerized and crosslinked to form a soft material; the black part of the outer layer was set to a laser wavelength of 690nm, a power of 16.0mW and a processing speed of 0.5mm/s, so that both free radical and cationic systems polymerized and crosslinked to form a rigid material. Placing the substrate on a hot table, firstly baking at 65 ℃ for 5min, and then baking at 95 ℃ for 10 min; after cooling to room temperature, the solution was placed in a propylene glycol methyl ether acetate developing solution for 5min, and then taken out and dried with nitrogen.
Fig. 4, content b, is an SEM image of a multi-material bi-layer structure, and fig. 4, content c, is a graph of the mechanical properties of the different layers of the structure, as can be seen from fig. 4, the mechanical stiffness of the two materials in the structure is about 13 times different, and the present invention has the ability to integrate materials with different mechanical properties.
Example 4
0.1ml of hydroxyethyl methacrylate, 0.3ml of polyethylene glycol diacrylate, 5mg of Irg.819, 0.1g of 3, 4-epoxycyclohexylmethyl-3, 4-epoxycyclohexyl formate, 0.6g of EPON SU-8 epoxy resin and 50. mu.l of a mixture of triarylsulfonium hexafluoroantimonate are added into a brown reagent bottle and magnetically stirred at 40 ℃ and 800rpm/min for 24 hours to obtain a uniform photoresist solution. Sequentially carrying out ultrasonic treatment on the substrate in deionized water and isopropanol for 15min respectively, and then drying at 80 ℃. The photoresist was dropped on the dried substrate and the photoresist was spun for 50s at 2000 rpm. And (3) placing the substrate coated with the photoresist on a hot bench, baking at 65 ℃ for 5min, and then baking at 95 ℃ for 10 min. Loading the sample obtained by pre-baking into a sample clamp of a laser direct writing platform, adjusting the focal length to focus femtosecond laser in photoresist, and directly writing a multi-material Taiji structure shown as a design drawing of content b in figure 5, wherein one part of the drawing is set to have the laser wavelength of 850nm, the power of 22.1mW and the processing speed of 2mm/s, so that a free matrix system is polymerized and crosslinked to form a soft material; the other part was set to a laser wavelength of 720nm, a power of 18.0mW and a processing speed of 0.5mm/s, so that both free-radical and cationic systems polymerized and crosslinked to form a rigid material. Placing the substrate on a hot table, firstly baking at 65 ℃ for 5min, and then baking at 95 ℃ for 10 min; after cooling to room temperature, the solution was placed in a propylene glycol methyl ether acetate developing solution for 5min, and then taken out and dried with nitrogen.
Example 5
0.3ml of hydroxyethyl methacrylate, 0.1ml of polyethylene glycol diacrylate, 5mg of Irg.819, 0.1g of 3, 4-epoxycyclohexylmethyl-3, 4-epoxycyclohexyl formate, 0.6g of EPON SU-8 epoxy resin and 50. mu.l of a mixture of triarylsulfonium hexafluoroantimonate are added into a brown reagent bottle and magnetically stirred at 40 ℃ and 800rpm/min for 24 hours to obtain a uniform photoresist solution. Sequentially carrying out ultrasonic treatment on the substrate in deionized water and isopropanol for 15min respectively, and then drying at 80 ℃. The photoresist was dropped on the dried substrate and the photoresist was spun for 50s at 2000 rpm. And (3) placing the substrate coated with the photoresist on a hot bench, baking at 65 ℃ for 5min, and then baking at 95 ℃ for 10 min. Loading the sample obtained by pre-baking into a sample clamp of a laser direct writing platform, adjusting the focal length to focus femtosecond laser in photoresist, and directly writing a multi-material Tai Ji structure shown as content a in figure 5, wherein one part of the structure is set to have the laser wavelength of 850nm, the power of 22.1mW and the processing speed of 2mm/s, so that a free matrix system is polymerized and crosslinked to form a soft material; the other part was set to a laser wavelength of 720nm, a power of 18.0mW and a processing speed of 0.5mm/s, so that both free-radical and cationic systems polymerized and crosslinked to form a rigid material. Placing the substrate on a hot table, firstly baking at 65 ℃ for 5min, and then baking at 95 ℃ for 10 min; after cooling to room temperature, the solution was placed in a propylene glycol methyl ether acetate developing solution for 5min, and then taken out and dried with nitrogen.
FIG. 5, item a, is an optical micrograph of the multi-material Tai Ji structure prepared in example 5, wherein the photoresist free radical component used is 0.3ml of hydroxyethyl methacrylate and 0.1ml of polyethylene glycol diacrylate, and it can be found that there is significant delamination between the two materials. FIG. 5, item b, is an optical micrograph of the multi-material Tai Ji structure prepared in example 4, wherein the photoresist free radical component used in the preparation is 0.1ml of hydroxyethyl methacrylate and 0.3ml of polyethylene glycol diacrylate, it can be seen that the delamination phenomenon is substantially eliminated by the addition of the free radical crosslinker component.
Of course, the preparation method of the multi-material three-dimensional micro-nano structure of the invention can also have various changes and modifications, and is not limited to the specific structure of the above embodiment.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. A composite photoresist for preparing a multi-material three-dimensional micro-nano structure is characterized in that: the composition comprises a free radical system component and a cationic system component, wherein the free radical system component comprises a free radical monomer, a free radical photoinitiator and a free radical crosslinking agent, and the cationic system component comprises a cationic monomer and a cationic photoinitiator;
the free matrix system component and the cation system component are respectively used for polymerizing and crosslinking under the action of focused laser beams with different wavelengths to form a three-dimensional micro-nano structure containing different materials, wherein the multi-material three-dimensional micro-nano structure comprises a free radical polymer formed by polymerizing and crosslinking the free matrix system component under the action of a first focused laser beam, namely a first material; also included are copolymers formed by the polymerization crosslinking of the free radical system component and the cationic system component together under the action of a second focused laser beam, i.e., second materials.
2. A composite photoresist according to claim 1, wherein: the free radical monomer is acrylic resin monomer; the free radical photoinitiator is Irg.819 or a phenylphosphoryl initiator, and the free radical crosslinking agent is a multifunctional acrylate crosslinking agent or a multifunctional methacrylate crosslinking agent; the cationic monomer is epoxy cationic monomer; the cation cross-linking agent is a triaryl sulfonium hexafluoroantimonate mixture or triaryl sulfonium salt.
3. The composite photoresist according to claim 2, wherein the ratio of each component in the composite photoresist is: radical monomer, radical photoinitiator, radical cross-linking agent, cationic monomer, cationic photoinitiator and (0.1-0.3) ml, (5-10) mg, (0.1-0.3) ml, (0.6-0.7) g, (40-80) mu l; preferably (0.1-0.3) ml, (5-10) mg, (0.3) ml, (0.6-0.7) g, (40-80) μ l.
4. A composite photoresist according to claim 1, wherein: the compound photoresist is prepared by fully mixing the free radical monomer, the free radical photoinitiator, the free radical crosslinking agent, the cationic monomer and the cationic photoinitiator under the condition of keeping out of the sun.
5. The composite photoresist according to claim 4, wherein: the sufficient mixing is magnetic stirring, the stirring condition is that the stirring is carried out for at least 12 hours, and the stirring speed is 600-1000 rpm/min.
6. The application of the composite photoresist according to any one of claims 1 to 5 in the preparation of multi-material three-dimensional micro-nano structures by femtosecond laser two-photon polymerization direct writing.
7. A method for preparing a multi-material three-dimensional micro-nano structure by using the compound photoresist of any one of claims 1 to 5 is characterized by comprising the following steps:
s1, spin-coating the composite photoresist on a substrate;
s2, focusing a first femtosecond laser beam on a region of the composite photoresist needing to form a first material, adjusting the wavelength and power of the laser beam to enable components of a free radical system to be polymerized and crosslinked, and directly writing to form the first material;
s3, focusing a second femtosecond laser beam on a region of the composite photoresist needing to form a second material, adjusting the wavelength and the power of the laser beam to enable a cation system component and a free radical system component to be subjected to polymerization crosslinking simultaneously, and forming the second material by direct writing;
and S4, baking and developing the composite photoresist after the direct writing is finished to obtain the multi-material three-dimensional micro-nano structure.
8. The method of claim 7, wherein: in the step S2, the first femtosecond laser beam has the wavelength of 780-1030 nm, the power of 6-100 mW and the laser processing speed of 0.01-20 mm/S; in the step S3, the second femtosecond laser beam has a wavelength of 690-750 nm, a power of 10-80 mW, and a laser processing speed of 0.05-20 mm/S.
9. The method of claim 7, wherein: the compound photoresist comprises the following components in percentage by weight: radical monomer, radical photoinitiator, radical cross-linking agent, cationic monomer, cationic photoinitiator and (0.1-0.3) ml, (5-10) mg, (0.1-0.3) ml, (0.6-0.7) g, (40-80) mu l; preferably (0.1-0.3) ml, (5-10) mg, (0.3) ml, (0.6-0.7) g, (40-80) μ l.
10. The method of claim 7, wherein: in the step S1, the composite photoresist is spin-coated on a substrate and placed on a hot stage for prebaking, wherein the prebaking method specifically comprises the steps of baking the substrate spin-coated with the composite photoresist for 0-5 min at 25-65 ℃, and then baking for 5-20 min at 65-95 ℃; in the step S3, the specific method of the thermal baking is to bake the composite photoresist after the direct writing is finished for 0-5 min at 25-65 ℃, and then bake for 10-30 min at 65-95 ℃.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114488692A (en) * | 2022-04-15 | 2022-05-13 | 之江实验室 | Photoresist composition and system based on two-photon absorption effect |
| CN114527630A (en) * | 2022-04-21 | 2022-05-24 | 之江实验室 | Femtosecond laser direct writing method for zirconium dioxide micro-nano pattern |
| CN115106537A (en) * | 2022-06-19 | 2022-09-27 | 华中科技大学 | Metal micro-nano 3D printing method based on laser direct writing |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114488692A (en) * | 2022-04-15 | 2022-05-13 | 之江实验室 | Photoresist composition and system based on two-photon absorption effect |
| CN114527630A (en) * | 2022-04-21 | 2022-05-24 | 之江实验室 | Femtosecond laser direct writing method for zirconium dioxide micro-nano pattern |
| CN114527630B (en) * | 2022-04-21 | 2022-08-05 | 之江实验室 | Femtosecond laser direct writing method for zirconium dioxide micro-nano pattern |
| CN115106537A (en) * | 2022-06-19 | 2022-09-27 | 华中科技大学 | Metal micro-nano 3D printing method based on laser direct writing |
| CN115106537B (en) * | 2022-06-19 | 2024-02-09 | 华中科技大学 | Metal micro-nano 3D printing method based on laser direct writing |
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