A shell-imitated mechanically reinforced photonic crystal paper, a preparation method thereof and application thereof in repeatable printing

Abstract

This invention discloses a shell-like mechanically reinforced photonic crystal paper, its preparation method, and its application in reusable printing. The photonic crystal paper is obtained by alternating arrangements of zirconium phosphate layered material and soft gel through shear force-induced self-assembly during coating. The photonic crystal paper of this invention has a shell-like brick-and-mortar structure. Simultaneously, strong hydrogen bonds exist between the zirconium phosphate and the soft gel, resulting in high tensile strength, high flexibility, high modulus, and self-supporting properties, enabling repeated printing. When inkjet printing is performed on the photonic crystal paper using an aqueous solution containing hygroscopic solutes, the gel matrix swells, increasing the lattice spacing and achieving a durable multi-color printing effect. Due to the good thermal stability of the selected zirconium phosphate layered material, and the brick-and-mortar structure reducing oxygen permeability, the photonic crystal paper possesses flame-retardant properties, improving storage safety. Because the coating method is simple and rapid, this photonic crystal paper can be produced continuously.

Description

Technical Field

[0001] This invention belongs to the technical field of rewritable photonic crystal paper materials, specifically a shell-like mechanically enhanced photonic crystal paper, its preparation method, and its reprintable applications. Background Technology

[0002] The invention of paper greatly promoted the development of human civilization. However, most printed materials are discarded after only one use, resulting in a huge waste of resources and environmental pollution. To overcome these problems, rewritable paper based on responsive photonic crystal materials has attracted widespread attention from researchers.

[0003] Photonic crystal materials are composed of periodically ordered arrangements of materials with different dielectric constants. These materials can reflect light of specific wavelengths to produce structural colors. Photonic crystal paper containing responsive gel components can be written on using aqueous solutions as ink. The writing area causes a reversible change in the lattice constant or refractive index, thus producing two contrasting colors and achieving rewriteability. This type of photonic crystal paper has great potential for compatibility with commercially available inkjet printers and writing instruments, thus demonstrating enormous commercial prospects and rapid development.

[0004] To date, related work has mainly focused on resolution, self-support, large-area manufacturing, multi-color writing, and rewritability. However, due to a lack of structural and compositional design, the mechanical properties of gel-based photonic crystal paper, such as strength, flexibility, and stiffness, are difficult to match with traditional commercial paper, making it unsuitable for ordinary inkjet printers. Furthermore, the low-throughput manufacturing of photonic crystal material assembly units and the time-consuming assembly process hinder the continuous manufacturing of gel-based photonic crystal paper. In addition, the flammability of polymers raises concerns about safe storage of gel-based photonic crystal paper. Therefore, finding a commercially viable photonic crystal assembly unit and designing an efficient and continuous preparation method to produce flame-retardant photonic crystal paper with a high strength-toughness-stiffness combination for commercial promotion is of paramount importance. Summary of the Invention

[0005] The technical problem this invention aims to solve is to overcome the low mechanical strength and complex, time-consuming preparation methods of existing photonic crystal paper, and to provide a shell-like mechanically enhanced photonic crystal paper, its preparation method, and its reusable printing applications. This invention's photonic crystal paper utilizes the swelling mechanism of a gel matrix to change the lattice spacing of the writing area, enabling repeated writing and printing. This photonic crystal paper possesses a shell-like brick-and-mortar structure and strong hydrogen bonding between the zirconium phosphate layered material and the soft gel, thus exhibiting high tensile strength, high flexibility, high modulus, and self-supporting properties. Due to the good thermal stability of the selected zirconium phosphate, and the brick-and-mortar structure reducing oxygen permeability, the photonic crystal paper possesses flame-retardant properties. The simple and rapid coating method allows for continuous production of this photonic crystal paper. When combined with water-based ink, this photonic crystal paper enables reusable writing and printing, offering advantages such as long-lasting color, cost-effectiveness, environmental friendliness, full-color writing, high-resolution printing, and strong rewritability.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention provides a method for preparing a shell-like mechanically enhanced photonic crystal paper, which is obtained by alternating arrangements of zirconium phosphate layered material and soft gel through shear force-induced self-assembly. The specific steps are as follows:

[0008] (1) Disperse zirconium phosphate (α-ZrP), non-volatile solvent, monomer, photoinitiator and crosslinking agent in water to obtain a prepolymer solution for photonic crystal paper;

[0009] (2) A certain amount of photonic crystal paper prepolymer liquid is dropped onto the substrate, and an adjustable coating tool is used to scrape the prepolymer liquid at a uniform speed to form a liquid film of a certain thickness. The shear force during the scraping process will induce zirconium phosphate to arrange in an orderly manner in the prepolymer liquid, thus obtaining a photonic crystal liquid film with obvious structural color.

[0010] (3) The photonic crystal liquid film obtained in step (2) above is peeled off from the substrate after being cured by ultraviolet light polymerization to obtain photonic crystal paper.

[0011] Preferably, in step (1), based on the total mass of the prepolymer liquid as 100%, the mass ratio of each substance in the prepolymer liquid is: zirconium phosphate 45%~60%, monomer 11%~30%, non-volatile solvent 6.7%~16%, crosslinking agent 0%~1.15%, photoinitiator 0.001%~0.1%, and the balance is water.

[0012] Photonic crystal papers of different colors can be obtained by changing the content of non-volatile solvents or zirconium phosphate. The mechanical strength can be adjusted by changing the ratio of monomers, non-volatile solvents, and crosslinking agents.

[0013] Preferably, in step (1), the zirconium phosphate has a diameter of 1-3 micrometers, a thickness of 10-100 nanometers, and a particle size dispersion index of no more than 0.4. The particle size dispersion of zirconium phosphate is reduced by gravity fractionation, thereby obtaining zirconium phosphate with a particle size dispersion index of no more than 0.4.

[0014] Preferably, in step (1), the monomers in the prepolymer solution are composed of monomer one and monomer two. Monomer one is diacetone acrylamide, accounting for 20-80% of the total mass of the monomers. Monomer two is one or a mixture of two or more of acrylamide, N-hydroxymethylacrylamide, methacrylamide, N,N-dimethylacrylamide and 4-acryloylmorpholine in any proportion. The non-volatile solvent is one or a mixture of two or more of polyethylene glycol 200, polyethylene glycol 400 and glycerol in any proportion. The crosslinking agent is one of adipate dihydrazide, N,N'-methylenebisacrylamide and polyethylene glycol diacrylate. The photoinitiator is one or a mixture of two of 2-hydroxy-2-methyl-1-phenyl-1-propanone and ethyl 2,4,6-trimethylbenzoylphenylphosphonate in any proportion.

[0015] Preferably, in step (2), the substrate is polyurethane or glass sheet.

[0016] Preferably, in step (3), the ultraviolet light polymerization and curing is achieved by irradiating with ultraviolet light with a wavelength of 350~400 nm and a power of 30~40 W for 60 seconds to 5 minutes.

[0017] Furthermore, continuous production of photonic crystal paper can be carried out on a continuous production device consisting of a scraper, injection pump, syringe, conveyor belt, ultraviolet lamp, and roll collection device.

[0018] Preferably, in continuous production, the prepolymer liquid is placed in a syringe, and the prepolymer liquid in the syringe is pushed at a constant speed by an injection pump to squeeze the prepolymer liquid onto the polyurethane substrate. Then, a scraper is immediately scraped at a constant speed to form a liquid film of a certain thickness. The conveyor belt transports the liquid film to a UV lamp for 30s~100s to complete the polymerization reaction. The polymerized photonic crystal paper is collected into a roll by a roll collection device.

[0019] The above preparation method yields a shell-like mechanically enhanced photonic crystal paper.

[0020] The aforementioned biomimetic shell-like mechanically enhanced photonic crystal paper is used as reusable printing paper or reusable writing paper.

[0021] The specific process is as follows:

[0022] (1) Use an aqueous solution containing different mass fractions of hygroscopic substances as ink to write on photonic crystal paper or add the ink to an ink cartridge, and use a commercially available inkjet printer to perform inkjet printing on photonic crystal paper;

[0023] (2) Soak the photonic crystal paper after writing or printing in a 20-30% (w / w) polyethylene glycol 200 aqueous solution for 50-200 seconds, then remove and dry it to wash away the writing or printing marks.

[0024] (3) Repeat steps (1) and (2).

[0025] Preferably, the hygroscopic substance in the ink is one or a mixture of two or more of the following in any proportion: lithium chloride, calcium chloride, magnesium chloride, zinc chloride, sodium nitrate, potassium acetate, etc.; polyethylene glycol 200; polyethylene glycol 400; glycerol; and glucose. The ink residue remains on the photonic crystal paper for 3 to 7 days.

[0026] This invention combines photonic crystals with a unique brick-and-mortar structure to prepare mechanically reinforced, reprintable, flame-retardant, and continuously producible photonic crystal paper.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] (1) The present invention prepares a photonic crystal paper with a shell-like brick-mud structure, which has high tensile strength, high flexibility, high modulus and self-support, and can be printed by commercially available inkjet printers;

[0029] (2) The zirconium phosphate layered material used in this invention can be commercially produced. The coating method of photonic crystal paper shortens the preparation cycle and has the value of continuous production and practical use.

[0030] (3) The zirconium phosphate selected in this invention has good thermal stability, and the brick-mud structure reduces oxygen permeability, which makes the photonic crystal paper have excellent flame retardant properties and high safe storage characteristics.

[0031] (4) The photonic crystal paper prepared by this invention can use an aqueous solution containing a hygroscopic solute as ink, and can be used to write or print words or patterns of various sizes, precisions and colors using a brush, dip pen, ink-filled marker or commercially available inkjet printer. The writing and printed patterns can last for at least a week and can be quickly erased by a polyethylene glycol aqueous solution, and can be reprinted up to hundreds of times.

[0032] (5) The strategy of using layered materials to prepare shell-like photonic crystal paper in this invention can provide new ideas for other researchers to manufacture photonic crystal materials with high mechanical strength. Attached Figure Description

[0033] Figure 1 This is a cross-sectional scanning electron microscope image of the mechanically enhanced photonic crystal paper prepared in Example 1 of the present invention.

[0034] Figure 2The stress-strain curve is shown for the mechanically enhanced photonic crystal paper prepared in Example 1 of this invention.

[0035] Figure 3 Flame retardant properties test of the mechanically reinforced photonic crystal paper prepared in Example 1 of the present invention.

[0036] Figure 4 To show text of different colors written on photonic crystal paper using calcium chloride aqueous solutions of different concentrations.

[0037] Figure 5 To obtain a photograph that is repeatedly printed 100 times on photonic crystal paper using a commercially available inkjet printer equipped with a calcium chloride aqueous solution. Detailed Implementation

[0038] The present invention will be further described below with reference to specific implementation methods. All raw materials used in the embodiments are commercially available. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are all conventional reagents, methods, and equipment within the technical field. The present invention described herein is for illustrative purposes only and is not intended to limit the scope of the invention.

[0039] Example 1

[0040] A method for preparing a shell-like mechanically enhanced photonic crystal paper, wherein the photonic crystal paper is obtained by alternating arrangements of zirconium phosphate layered material and soft gel through shear force-induced self-assembly. The specific steps are as follows:

[0041] (1) 10g of zirconium phosphate layered material (α-ZrP, diameter 1~3 μm, thickness approximately 50 nm) was dispersed in 40mL of water and allowed to stand for 48h for gravity fractionation. The supernatant was centrifuged and dried to obtain zirconium phosphate with a particle size dispersibility index (PDI) of 0.34. Based on the total mass of the prepolymer solution as 100%, the mass fractions of each substance in the prepolymer solution were as follows: 50% zirconium phosphate, 8.99% polyethylene glycol 200, 8.99% diacetone acrylamide, 17.97% acrylamide, 0~1.15% (specifically 0, 0.15%, 0.29%, 0.58%, 1.15%) adipate dihydrazide (ADH), 0.09wt% 2-hydroxy-2-methyl-1-phenyl-1-propanone, with the remainder being water. All substances were mixed evenly to obtain the prepolymer solution for photonic crystal paper.

[0042] (2) Drop 2g of photonic crystal paper prepolymer solution onto a glass plate, and use an adjustable coating tool to scrape the prepolymer solution at a uniform speed to form a liquid film with a thickness of 350μm at a speed of 6cm / s. The shear force during the scraping process will induce zirconium phosphate to arrange in an orderly manner in the prepolymer solution, thus obtaining a photonic crystal liquid film with obvious structural color.

[0043] (3) The photonic crystal liquid film obtained in step (2) above is irradiated under ultraviolet light (wavelength 365 nm, power 36 W) for 60 s to polymerize, and then peeled off from the glass plate to obtain blue photonic crystal paper. Figure 1 The SEM images show the shell-like brick-and-mortar structure of the prepared photonic crystal paper.

[0044] (4) Figure 2 The tunable mechanical properties of the aforementioned photonic crystal paper were demonstrated. As the mass fraction of adipic acid dihydrazide increased from 0 to 1.15%, the tensile strength of the photonic crystal paper correspondingly increased to approximately 11.6 MPa, 15.6 MPa, 17.8 MPa, 20.3 MPa, and 24.2 MPa, respectively; the toughness correspondingly increased to approximately 13.1 MJ / m³, 9.8 MJ / m³, 9.7 MJ / m³, 5.5 MJ / m³, and 4.2 MJ / m³, respectively; and the modulus correspondingly increased to approximately 94.4 MPa, 152.4 MPa, 225.9 MPa, 317.6 MPa, and 501.1 MPa, respectively. The tensile strength of the photonic crystal paper is obtained from pure poly(diacetone-acrylamide). co - The polyacrylamide gel matrix (i.e., the zirconium phosphate is omitted in step (1), and everything else is the same as the gel matrix obtained in steps (1) to (3)) is 200 to 300 times larger. After being continuously ignited with an open flame for 10 seconds and then the flame source is removed, the prepared photonic crystal paper self-extinguishes within 1 second, exhibiting flame retardancy. See Figure 3 .

[0045] Example 2

[0046] A method for preparing a shell-like mechanically enhanced photonic crystal paper, wherein the photonic crystal paper is obtained by alternating arrangements of zirconium phosphate layered material and soft gel through shear force-induced self-assembly. The specific steps are as follows:

[0047] (1) 10g of zirconium phosphate layered material (α-ZrP, diameter 1~3 μm, thickness approximately 50 nm) was dispersed in 40mL of water and allowed to stand for 48h for gravity fractionation. The supernatant was then centrifuged and dried to obtain zirconium phosphate with a particle size dispersibility index (PDI) of 0.34. Based on the total mass of the prepolymer solution as 100%, the mass fractions of each substance in the prepolymer solution were as follows: 50% zirconium phosphate, 6.73%~15.7% glycerol (specifically 6.73%, 8.97%, 11.21%, 13.46%, and 15.70% respectively), 17.97% diacetone acrylamide, 8.99% 4-acryloylmorpholine, 0.58% N,N'-methylenebisacrylamide, 0.09% ethyl 2,4,6-trimethylbenzoylphenylphosphonate, with the remainder being water. All substances were mixed thoroughly to obtain the prepolymer solution for photonic crystal paper.

[0048] (2) Drop 2g of photonic crystal paper prepolymer solution onto a glass plate, and use an adjustable coating tool to scrape the prepolymer solution at a uniform speed to form a liquid film with a thickness of 350μm at a speed of 6cm / s. The shear force during the scraping process will induce zirconium phosphate to arrange in an orderly manner in the prepolymer solution, thus obtaining a photonic crystal liquid film with obvious structural color.

[0049] (3) The photonic crystal liquid film obtained in step (2) above is irradiated under ultraviolet light (wavelength 365 nm, power 36 W) for 60 s to polymerize, and then peeled off from the substrate to obtain blue, cyan, green, yellow and red photonic crystal paper;

[0050] (4) As the glycerol content decreased from 15.7% to 6.73%, the tensile strength of the photonic paper was 12.4 MPa, 14.3 MPa, 18.9 MPa, 21.6 MPa, and 25.1 MPa, respectively; the toughness was 4.1 MJ / m³, 3.5 MJ / m³, 2.7 MJ / m³, 1.9 MJ / m³, and 1.4 MJ / m³, respectively; and the modulus was 15.4 MPa, 30.3 MPa, 535.1 MPa, 826.3 MPa, and 1271.9 MPa, respectively. The tensile strength of the photonic crystal paper is that of pure poly(diacetone-acrylamide) co - The polyacrylamide gel matrix (i.e., the zirconium phosphate is omitted in step (1), and the rest is the same as the gel matrix obtained in steps (1) to (3)) is 200 to 300 times larger. After being continuously ignited with an open flame for 10 seconds and then the flame source is removed, the prepared photonic crystal paper self-extinguishes within 1 second and has flame retardancy.

[0051] Example 3

[0052] A method for preparing a shell-like mechanically enhanced photonic crystal paper, wherein the photonic crystal paper is obtained by alternating arrangements of zirconium phosphate layered material and soft gel through shear force-induced self-assembly. The specific steps are as follows:

[0053] (1) 10g of zirconium phosphate layered material (α-ZrP, diameter 1~3 μm, thickness approximately 50 nm) was dispersed in 40mL of water and allowed to stand for 48h for gravity fractionation. The supernatant was then centrifuged and dried to obtain zirconium phosphate with a particle size dispersibility index (PDI) of 0.34. Based on the total mass of the prepolymer solution as 100%, the mass fractions of each substance in the prepolymer solution were as follows: 45%~60% zirconium phosphate (specifically 45%, 50%, 55%, and 60% respectively), 8.99% polyethylene glycol 200, 17.97% diacetone acrylamide, 8.99% acrylamide, 0.58% N,N'-methylenebisacrylamide, 0.09% ethyl 2,4,6-trimethylbenzoylphenylphosphonate, with the remainder being water. All substances were mixed thoroughly to obtain the prepolymer solution for photonic crystal paper.

[0054] (2) Drop 2g of photonic crystal paper prepolymer solution onto a glass plate, and use an adjustable coating tool to scrape the prepolymer solution at a uniform speed to form a liquid film with a thickness of 350μm at a speed of 6cm / s. The shear force during the scraping process will induce zirconium phosphate to arrange in an orderly manner in the prepolymer solution, thus obtaining a photonic crystal liquid film with obvious structural color.

[0055] (3) The photonic crystal liquid film obtained in step (2) above is irradiated under ultraviolet light (wavelength 365 nm, power 36 W) for 60 s to polymerize, and then peeled off from the substrate to obtain yellow, green, cyan and blue photonic crystal paper;

[0056] (4) As the zirconium phosphate content increased from 45% to 60%, the tensile strength of the photonic paper was 17.3 MPa, 19.6 MPa, 23.2 MPa, and 25.6 MPa, respectively; the toughness was 6.3 MJ / m³, 5.8 MJ / m³, 5.1 MJ / m³, and 4.8 MJ / m³, respectively; and the modulus was 280.1 MPa, 300.5 MPa, 366.8 MPa, and 420.6 MPa, respectively. The tensile strength of the photonic crystal paper is that of pure poly(diacetone-acrylamide) co - The polyacrylamide gel matrix (i.e., the zirconium phosphate is omitted in step (1), and the rest is the same as the gel matrix obtained in steps (1) to (3)) is 200 to 300 times larger. After being continuously ignited with an open flame for 10 seconds and then the flame source is removed, the prepared photonic crystal paper self-extinguishes within 1 second and has flame retardancy.

[0057] Example 4

[0058] Mechanically enhanced photonic crystal paper offers multi-color writing and reprintability:

[0059] (1) Calcium chloride with a mass fraction of 15%-30% was dissolved in water to serve as ink. Then, markers filled with ink of different calcium chloride concentrations were used to write on blue photonic crystal paper with a mass fraction of 0.58% adipic acid dihydrazide in Example 1. As the calcium chloride concentration increased, the gel swelling degree of the writing area gradually increased, and the red shift of the photonic crystal paper increased, ultimately producing cyan-green to orange-yellow characters, achieving multi-color writing. See [link to example]. Figure 4 The calcium chloride concentrations from top to bottom are 15%, 20%, 25%, and 30%.

[0060] (2) Fill the empty ink cartridge of a commercially available HP inkjet printer with 20wt% calcium chloride ink from step (1), and then inkjet print the blue photonic crystal paper with a mass fraction of 0.58% adipic acid dihydrazide from Example 1 to obtain clear fonts or patterns.

[0061] (3) Immerse the photonic crystal paper with the printed information from step (2) in a 25% (w / w) aqueous solution of polyethylene glycol 200 for 90 seconds, then remove it and dry it at 60°C for 2 minutes. As the salt ink is washed out, the printed information will disappear, thus erasing the information. The erased photonic crystal paper can then be inkjet printed again. This "print-erasure-print" process can be repeated hundreds of times. For details, see [link to documentation]. Figure 5 .

[0062] Example 5

[0063] Demonstration of continuous production of mechanically reinforced photonic crystal paper:

[0064] (1) 1000g of zirconium phosphate layered material (α-ZrP, diameter 1~3 μm, thickness approximately 50 nm) was dispersed in 4000mL of water and allowed to stand for 48h before gravity fractionation. The supernatant was then centrifuged and dried to obtain zirconium phosphate with a particle size dispersibility index (PDI) of 0.34. Based on the total mass of the prepolymer solution as 100%, the mass fractions of each substance in the prepolymer solution were as follows: 50% zirconium phosphate, 8.99% polyethylene glycol 200, 8.99% diacetone acrylamide, 17.97% acrylamide, 0.58% adipate dihydrazide, 0.09% 2-hydroxy-2-methyl-1-phenyl-1-propanone, with the remainder being water. All substances were mixed thoroughly to obtain the prepolymer solution for photonic crystal paper.

[0065] (2) A miniature continuous production device is assembled from a scraper, injection pump, syringe, conveyor belt, ultraviolet lamp, and roll collection device to demonstrate the continuous production of photonic crystal paper.

[0066] (3) 100g of prepolymer solution for photonic crystal paper is injected into a syringe, and the syringe is pushed at a constant speed by the syringe to squeeze the prepolymer solution onto the polyurethane substrate. At the same time, the conveyor belt moves the polyurethane at a speed of 1cm / s, which generates relative motion with the doctor blade of the coating device. The resulting shear force induces zirconium phosphate to arrange in an orderly manner in the prepolymer solution, thus obtaining a continuous photonic crystal liquid film with obvious structural color. The photopolymerized photonic crystal paper is continuously irradiated under a UV lamp above the conveyor belt for photocuring. At the end of the conveyor belt, the polymerized photonic crystal paper is collected into a roll by a roll-up collection device.

[0067] The above description is merely an embodiment of the present invention and is not intended to limit the present invention in any other way. Any simple modifications, equivalent changes, and improvements made by those skilled in the art to the above embodiments without departing from the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a shell-like mechanically enhanced photonic crystal paper, characterized in that, The specific steps are as follows: (1) Disperse zirconium phosphate, non-volatile solvent, monomer, photoinitiator and crosslinking agent in water to obtain a prepolymer solution for photonic crystal paper. Based on the total mass of the prepolymer solution as 100%, the mass ratio of each substance in the prepolymer solution is: zirconium phosphate 45%~60%, monomer 11%~30%, non-volatile solvent 6.7%~16%. The crosslinking agent is 0%~1.15%, the photoinitiator is 0.001%~0.1%, and the balance is water; the monomers in the prepolymer solution are composed of monomer one and monomer two, monomer one is diacetone acrylamide, accounting for 20~80% of the total monomer mass; monomer two is one or a mixture of two or more of acrylamide, N-hydroxymethylacrylamide, methacrylamide, N,N-dimethylacrylamide and 4-acryloylmorpholine in any proportion; the non-volatile solvent is one or a mixture of two or more of polyethylene glycol 200, polyethylene glycol 400 and glycerol in any proportion; the crosslinking agent is one of adipic acid dihydrazide, N,N'-methylenebisacrylamide and polyethylene glycol diacrylate; the zirconium phosphate has a diameter of 1~3 micrometers, a thickness of 10~100 nanometers, and a particle size dispersion index of not more than 0.4; (2) The prepolymer liquid of the photonic crystal paper is coated onto the substrate to obtain a photonic crystal liquid film; (3) The photonic crystal liquid film obtained in step (2) above is peeled off from the substrate after being cured by ultraviolet light polymerization to obtain photonic crystal paper.

2. The preparation method according to claim 1, characterized in that, In step (1), the photoinitiator is one or a mixture of two of 2-hydroxy-2-methyl-1-phenyl-1-propanone and ethyl 2,4,6-trimethylbenzoylphenylphosphonate in any proportion.

3. The preparation method according to claim 1, characterized in that, In step (2), the substrate is polyurethane or glass sheet.

4. The preparation method according to claim 1, characterized in that, In step (3), ultraviolet light polymerization and curing is achieved by irradiating with ultraviolet light with a wavelength of 350~400 nm and a power of 30~40 W for 60 seconds to 5 minutes.

5. The shell-like mechanically enhanced photonic crystal paper prepared by the preparation method according to any one of claims 1 to 4.

6. The application of the shell-like mechanically enhanced photonic crystal paper of claim 5 as reusable printing paper or reusable writing paper.

7. The application according to claim 6, characterized in that, The process is as follows: (1) Use an aqueous solution containing different mass fractions of hygroscopic substances as ink to write on photonic crystal paper or add the ink to an ink cartridge, and use a commercially available inkjet printer to perform inkjet printing on photonic crystal paper; (2) Soak the photonic crystal paper after writing or printing in a 20-30% (w / w) polyethylene glycol 200 aqueous solution for 50-200 seconds, then remove and dry it to wash away the writing or printing marks. (3) Repeat steps (1) and (2).

8. The application according to claim 7, characterized in that, In step (1), the hygroscopic substance in the ink is one or more of lithium chloride, calcium chloride, magnesium chloride, zinc chloride, sodium nitrate, potassium acetate, polyethylene glycol 200, polyethylene glycol 400, glycerol and glucose in any proportion.

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