Photonic crystal film and preparation method and application thereof

Abstract

The invention relates to the technical field of photonic crystals, and particularly discloses a photonic crystal film and a preparation method and application thereof. The preparation method comprises the following steps: (a) preparing a gel electrolyte precursor solution; (b) preparing Fe3O4 magnetic nano particles; (c) mixing the Fe3O4 magnetic nanoparticles with the gel electrolyte precursor solution; and (d) placing the mixed solution obtained in the step (c) in a magnetic field, and carrying out photocuring treatment to obtain the photonic crystal film. According to the preparation method of the photonic crystal thin film, Fe3O4 magnetic nanoparticles and a gel electrolyte precursor solution are mixed in a magnetic field and subjected to photocuring treatment, so that the Fe3O4 magnetic nanoparticles in the prepared photonic crystal thin film are directionally arranged to form a periodic three-dimensional structure, highly ordered arrangement is achieved, and the performance of the photonic crystal thin film is improved. And dual response of the photonic crystal film to an optical signal / electric signal of external stress can be realized.

Description

Technical Field

[0001] The present application relates to the technical field of photonic crystal materials, and in particular to a photonic crystal film and a preparation method and application thereof. Background Art

[0002] Many organisms in nature have the ability to adjust the color of their body surface according to the external environment. Organisms can convert environmental information into bioelectric signals and transmit them to the nervous system through ions passing through the cell membrane, thereby sensing external strain, touch, vibration, temperature, etc. Inspired by the regulation of body surface color by organisms, photonic crystal materials simulate biological functions realistically, providing new ideas for the field of artificial skin and flexible sensing. Related research on this material has attracted widespread attention. The crystal arrangement structure of one-dimensional photonic crystals can interact with incident light to produce visual structural colors. By adjusting the refractive index and thickness (lattice spacing) of photonic crystals, photonic crystal materials can change color in a short time. Compared with traditional dyes and pigments, the structural colors generated by the light interference of the periodic microstructure of photonic crystals have the characteristics of full color range, non-fading, and modifiable structure and function. They have broad application prospects in the fields of sensing, decoration, display, anti-counterfeiting, and biological analysis.

[0003] The combination of gel as an elastomer and photonic crystal primitive materials has been proven to be highly effective, but according to existing reports, the orderly assembly of photonic crystal primitive materials and elastomers has always been a difficult problem to solve. Common assembly methods include spin coating, 3D printing, etching, or self-assembly under solvent conditions using non-ionic surfactants, but the above schemes are difficult to achieve highly ordered arrangements, and the manufacturing steps are cumbersome and difficult to mass produce. Therefore, the existing technology needs to be improved. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the purpose of the present application is to provide a photonic crystal film and a preparation method and application thereof, aiming to solve the problem that it is difficult to achieve highly ordered arrangement of photonic crystal elementary materials and elastomers.

[0005] The technical solution of this application is as follows:

[0006] In a first aspect of the present application, a method for preparing a photonic crystal film is provided, comprising the steps of:

[0007] (a) preparing a gel electrolyte precursor solution; (b) preparing Fe3O4 magnetic nanoparticles; (c) mixing the Fe3O4 magnetic nanoparticles with the gel electrolyte precursor solution; (d) placing the mixed solution obtained in (c) in a magnetic field and performing a photocuring treatment to obtain a photonic crystal film.

[0008] Preferably, the preparation method of the gel electrolyte precursor solution comprises the steps of: (a1) mixing a solvent and a lithium salt to obtain a mixed solution; (a2) adding 4-acryloylmorpholine, a crosslinking agent, and an initiator to the mixed solution obtained in (a1), stirring and mixing, and obtaining a gel electrolyte precursor solution.

[0009] Preferably, the concentration of lithium salt in the mixed solution obtained by (a1) is 0.2-2 mol / L, the molar percentage of the crosslinking agent relative to the elastic monomer in (a2) is 0.03-0.3 mol%, and the molar percentage of the initiator relative to the elastic monomer is 0.4-5 mol%; the solvent includes at least one of dimethyl sulfoxide, water, ethanol, methanol, chloroform, ethylene glycol, and N,N-dimethylformamide, the lithium salt includes at least one of lithium bis(trifluoromethanesulfonyl)imide and lithium chloride, the elastic monomer includes at least one of acrylamide and 4-acryloylmorpholine, the crosslinking agent includes at least one of polyethylene glycol diacrylate and N,N'-methylenebisacrylamide, and the photoinitiator includes at least one of 1-hydroxycyclohexyl phenyl ketone and ammonium persulfate.

[0010] Preferably, the specific step of mixing in (c) comprises: mixing the Fe3O4 magnetic nanoparticles with the gel electrolyte precursor solution and then dispersing them using ultrasound, wherein 2-15 mg of Fe3O4 magnetic nanoparticles are dispersed in every 10 mL of the gel electrolyte precursor solution.

[0011] Preferably, the specific step (d) includes: (d1) transferring the mixed solution obtained in (c) into a reaction container; (d2) placing the reaction container under a magnetic field for 30-120 seconds to allow the Fe3O4 magnetic nanoparticles to be arranged in an orderly manner in the mixed solution, and then performing a photocuring treatment to obtain the photonic crystal film.

[0012] Preferably, the reaction container is selected from a glass container and an acrylic container; the thickness of the wall of the reaction container is 0.2-5 mm.

[0013] Preferably, the magnetic induction intensity of the magnetic field is 150-6000Gs.

[0014] Preferably, the light curing step is to irradiate the reaction container under ultraviolet light for 3-15 minutes, the distance between the ultraviolet light source and the reaction container is 3-30 cm, the wavelength of the ultraviolet light is 365-395 nm, and the power is 15-20 W.

[0015] The second aspect of the present application provides a photonic crystal film prepared by the method for preparing a photonic crystal film in the first aspect of the present application.

[0016] The third aspect of the present application provides an application of the photonic crystal film in the second aspect of the present application in stress detection.

[0017] Compared with the prior art, this application has the following advantages:

[0018] The preparation method of the photonic crystal film in the present application is to mix Fe3O4 magnetic nanoparticles with a gel electrolyte precursor in a magnetic field and perform a photocuring treatment, so that the Fe3O4 magnetic nanoparticles are oriented to form a periodic three-dimensional structure, thereby achieving a highly ordered arrangement. In addition, the preparation method in the present application has low requirements on preparation instruments and reaction conditions, is simple, and is conducive to large-scale production.

[0019] Further, the photonic crystal film in the present application is a combination of a hydrogel matrix (gel), a photonic crystal elementary material (Fe3O4 magnetic nanoparticles), and an electrolyte (lithium salt). Among them, the Fe3O4 magnetic nanoparticles themselves have a significant difference in dielectric constant and refractive index with the surrounding medium, thereby producing a photonic bandgap structure, which has the effect of regulating light propagation. When visible light passes through the photonic crystal film, light of a specific wavelength will be modulated by the photonic bandgap structure, causing the light of a specific wavelength to not be reflected, so only its complementary color can be observed. When the photonic crystal film is in the process of stretching, the distance between the nanoparticles will change, and the modulated visible light band will also change accordingly, thereby realizing the color change of the film. In addition, during the stretching process, the resistance of the film will also increase, causing the current at both ends of the film to become smaller, realizing the dual response of the photonic crystal film to the optical signal / electrical signal of external stress (including tension, shear force, pressure, etc.). BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for describing the embodiments are briefly introduced below.

[0021] Figure 1 This is a scanning electron microscope photo of Fe3O4 magnetic nanoparticles prepared in Example 1 of the present application;

[0022] Figure 2 This is a scanning electron microscope photo of the photonic crystal film prepared in Example 1 of the present application;

[0023] Figure 3 This is a scanning electron microscope photo of the photonic crystal film prepared in Example 2 of the present application;

[0024] Figure 4 This is an electrochemical window test diagram of the photonic crystal film prepared in Example 1 of the present application;

[0025] Figure 5 This is an AC impedance diagram of the photonic crystal film prepared in Example 1 of the present application;

[0026] Figure 6 A tensile stress-strain curve diagram of the photonic crystal film prepared in Example 1 of the present application;

[0027] Figure 7 The tensile strain-time and relative resistance-time curves of the photonic crystal film prepared in Example 1 of the present application at different frequencies;

[0028] Figure 8 The stress-strain and relative resistance-time curves of the cyclic gradual stretching of the photonic crystal film prepared in Example 1 of the present application;

[0029] Fig. 9 The stress-strain and relative resistance-time curves of the cyclic stretching of the photonic crystal film prepared in Example 1 of the present application;

[0030] Fig.10 CIE graphs of the photonic crystal film prepared in Example 1 of the present application under different tensile strains;

[0031] Fig.11 This is an electrochemical window test diagram of the photonic crystal film prepared in Example 2 of the present application;

[0032] Fig.12 This is an AC impedance diagram of the photonic crystal film prepared in Example 2 of the present application;

[0033] Fig.13 A tensile stress-strain curve diagram of the photonic crystal film prepared in Example 2 of the present application;

[0034] Fig.14 The stress-strain and relative resistance-time curves of the cyclic gradual stretching of the photonic crystal film prepared in Example 2 of the present application. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the drawings and embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present application. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0036] It should be noted that if there are descriptions involving "first", "second", etc. in the implementation of this application, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or suggesting their relative importance and implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the fact that ordinary technicians in the field can implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0037] The crystal arrangement structure of one-dimensional photonic crystals can physically interact with incident light to produce visual structural colors. Strain and tactile sensing between two color states has been developed, but because it can only switch within a limited color range, it is difficult to observe continuous intermediate states, which limits its development and application. Photonic crystal sensing materials can broaden the visual color range and achieve full-color visual sensing, which can make up for the shortcomings of traditional sensor devices with single color display.

[0038] The combination of gel as an elastomer and photonic crystal primitive material has been proven to be highly effective, but according to existing reports (Sahu RR, Ramasamy AS, Bhonsle S, et al. Single-step fabrication of liquid gallium nanoparticles via capillary interaction for dynamic structural colours [J]. Nature Nanotechnology, 2024, 19 (6): 766-774. DOI: 10.1038 / s41565-024-01625-1.), the orderly assembly of photonic crystal primitives and elastomers has always been a difficult problem to solve. Common assembly methods include spin coating, 3D printing, etching, or self-assembly under solvent conditions using non-ionic surfactants, but the above schemes are difficult to achieve highly ordered arrangements, or the manufacturing steps are cumbersome and difficult to scale up, which hinders their widespread application in industry.

[0039] Based on this, in a first aspect of an embodiment of the present application, a method for preparing a photonic crystal film is provided, comprising the following steps:

[0040] (a) preparing a gel electrolyte precursor solution;

[0041] (b) Preparation of Fe3O4 magnetic nanoparticles;

[0042] (c) mixing Fe3O4 magnetic nanoparticles with a gel electrolyte precursor solution;

[0043] (d) The mixed solution obtained in (c) is placed in a magnetic field and subjected to a photocuring treatment to obtain a photonic crystal film.

[0044] By mixing Fe3O4 magnetic nanoparticles with gel electrolyte precursor in a magnetic field and performing photocuring, the Fe3O4 magnetic nanoparticles are oriented to form a periodic three-dimensional structure, achieving a highly ordered arrangement. There is a significant difference in dielectric constant and refractive index between the Fe3O4 magnetic nanoparticles themselves and the surrounding medium, which produces a photonic bandgap structure, which has the function of regulating light propagation. When visible light passes through the photonic crystal film, light of a specific wavelength will be modulated by the photonic bandgap structure, resulting in the light of a specific wavelength not being reflected, so only its complementary color can be observed. When the photonic crystal film is stretched, the distance between the nanoparticles will change, and the modulated visible light band will also change accordingly, thereby achieving the color change of the film. In addition, during the stretching process, the resistance of the film will also increase, resulting in a decrease in the current at both ends of the film, realizing the dual response of the photonic crystal film to external stress (including tension, shear force, pressure, etc.) of optical signals / electrical signals.

[0045] In some embodiments, the method for preparing the gel electrolyte precursor solution comprises the steps of:

[0046] (a1) mixing a solvent and a lithium salt to obtain a mixed solution;

[0047] (a2) adding an elastic monomer, a crosslinking agent and an initiator to the mixed solution obtained in (a1), stirring and mixing, and obtaining a gel electrolyte precursor solution.

[0048] The concentration of lithium salt in the mixed solution obtained by (a1) is 0.2-2 mol / L. For example, the concentration of lithium salt in the mixed solution obtained by (a1) is 0.2 mol / L, 0.3 mol / L, 0.5 mol / L, 0.8 mol / L, 1 mol / L, 1.3 mol / L, 1.5 mol / L, 1.7 mol / L, 2 mol / L, etc. The concentration of lithium salt in the solvent will affect the ionic conductivity and electrochemical window of the film. If the concentration of lithium salt is high, the conductivity and electrochemical window of the photonic crystal film will deteriorate. The concentration of lithium salt is set as above so that the prepared photonic crystal film has excellent electrochemical properties.

[0049] The molar percentage of the crosslinking agent to the elastic monomer in (a2) is 0.03-0.3 mol%. For example, the molar percentage of the crosslinking agent to the elastic monomer in (a2) is 0.03 mol%, 0.05 mol%, 0.1 mol%, 0.2 mol%, 0.25 mol%, 0.3 mol%, etc. The crosslinking agent is arranged in the above manner so that the prepared photonic crystal film has better mechanical properties (elastic modulus, fracture strain, etc.).

[0050] The molar percentage of the initiator relative to the elastic monomer in (a2) is 0.4-5 mol%. For example, the molar percentage of the initiator relative to the elastic monomer in (a2) is 0.4 mol%, 0.5 mol%, 1 mol%, 1.5 mol%, 2 mol%, 2.5 mol%, 3 mol%, 3.5 mol%, 4 mol%, 4.5 mol% or 5 mol%, etc. The above-mentioned setting of the initiator can enable the photonic crystal film to complete the curing reaction as soon as possible when the curing degree is complete during the preparation process.

[0051] In some embodiments, the solvent includes at least one of dimethyl sulfoxide, water, ethanol, methanol, chloroform, ethylene glycol, and N,N-dimethylformamide. The lithium salt includes at least one of lithium bis(trifluoromethanesulfonyl)imide and lithium chloride, the elastic monomer includes at least one of acrylamide and 4-acryloylmorpholine, the crosslinking agent includes at least one of polyethylene glycol diacrylate and N,N'-methylenebisacrylamide, and the photoinitiator includes at least one of 1-hydroxycyclohexylphenyl ketone and ammonium persulfate. The concentration of the elastic monomer affects the tensile properties of the prepared photonic crystal film.

[0052] In some embodiments, the method for preparing Fe3O4 magnetic nanoparticles comprises the steps of:

[0053] (b1) dissolving tannic acid in ethylene glycol and stirring and mixing at a first temperature;

[0054] (b2) heating the mixed solution obtained in (b1) to a second temperature, adding polyvinyl pyrrolidone, and stirring to mix;

[0055] (b3) cooling the mixed solution obtained in (b2) to a third temperature, adding ferric chloride hexahydrate, and stirring to mix;

[0056] (b4) cooling the mixed solution obtained in (b3) to a fourth temperature, adding sodium acetate, and stirring to mix;

[0057] (b5) The mixed solution obtained in (b4) is heated to a fifth temperature for reaction, and washed to obtain Fe3O4 magnetic nanoparticles.

[0058] In some embodiments, the concentration of tannic acid in the mixed solution obtained by (b1) is 0.3-4 g / L. For example, the concentration of tannic acid in the mixed solution obtained by (b1) is 0.3 g / L, 0.5 g / L, 0.8 g / L, 1 g / L, 1.2 g / L, 1.5 g / L, 2 g / L, 2.5 g / L, 3 g / L, 3.5 g / L, 4 g / L, etc. In the mixed solution obtained by (b2), the concentration of polyvinyl pyrrolidone is 166.7 g / L. In the mixed solution obtained by (b3), the concentration of ferric chloride hexahydrate is 17.99 g / L. In the mixed solution obtained by (b4), the concentration of sodium acetate is 93.33 g / L.

[0059] In some embodiments, the first temperature is 20-30°C. For example, the first temperature is 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C or 30°C, etc. The second temperature is 30-200°C. For example, the second temperature is 30°C, 40°C, 50°C, 60°C, 80°C, 100°C, 130°C, 150°C, 180°C or 200°C, etc. The third temperature is 30-65°C. For example, the third temperature is 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C or 65°C, etc. The fourth temperature is 30-35°C. For example, the fourth temperature is 30°C, 31°C, 32°C, 33°C, 34°C or 35°C, etc. The fifth temperature is 80-200°C. For example, the fifth temperature is 80° C., 90° C., 100° C., 120° C., 140° C., 150° C., 160° C., 180° C., or 200° C., etc.

[0060] In some embodiments, the reaction time in (b5) is 6-36 hours. For example, the reaction time in (b5) is 6 hours, 10 hours, 12 hours, 15 hours, 18 hours, 20 hours, 24 hours, 28 hours, 32 hours or 36 hours. The washing liquid for washing includes at least one of ethanol and deionized water.

[0061] In some embodiments, the specific step of mixing in (c) includes: mixing the Fe3O4 magnetic nanoparticles with the gel electrolyte precursor solution and then dispersing them using ultrasound, wherein 2-15 mg of Fe3O4 magnetic nanoparticles are dispersed in every 10 mL of the gel electrolyte precursor solution. For example, 2 mg, 3 mg, 5 mg, 7 mg, 8 mg, 10 mg, 12 mg or 15 mg of Fe3O4 magnetic nanoparticles are dispersed in every 10 mL of the gel electrolyte precursor solution.

[0062] In some embodiments, (d) specifically comprises the steps of:

[0063] (d1) transferring the mixed solution obtained in (c) into a reaction container. The reaction container is selected from a glass container and an acrylic container, and the thickness of the wall of the reaction container is 0.2-5 mm. For example, the thickness of the glass reaction chamber is 0.2 mm, 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm or 5 mm.

[0064] In some embodiments, step (d1) comprises: using a syringe to draw the mixed solution obtained in step (c) and injecting it into a 4×4 cm 2 inside the glass reaction chamber.

[0065] (d2) placing the reaction container under a magnetic field to arrange the Fe3O4 magnetic nanoparticles in an orderly manner in the mixed solution, and then performing a photocuring treatment to obtain the photonic crystal film.

[0066] In some embodiments, the magnetic field has a magnetic flux density of 150-6000 Gs. For example, the magnetic flux density of the magnetic field is 150 Gs, 500 Gs, 1000 Gs, 1500 Gs, 2000 Gs, 2500 Gs, 3000 Gs, 3500 Gs, 4000 Gs, 4500 Gs, 5000 Gs, 5500 Gs, or 6000 Gs.

[0067] In some embodiments, the step of photocuring is to irradiate the reaction container under ultraviolet light for 3-15 minutes, the distance from the ultraviolet light source to the reaction container is 3-30 cm, the wavelength of the ultraviolet light is 365 nm, and the power is 15 W. For example, the curing time of ultraviolet light is 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min or 15 min, etc. The distance from the ultraviolet light source to the glass reaction chamber is 3 cm, 5 cm, 10 cm, 15 cm, 20 cm, 25 cm or 30 cm, etc.

[0068] According to a second aspect of the embodiments of the present application, there is provided a photonic crystal film prepared by the method for preparing a photonic crystal film according to the first aspect of the embodiments of the present application.

[0069] The third aspect of the embodiment of the present application provides an application of the photonic crystal film of the second aspect of the embodiment of the present application in stress detection, wherein the stress detectable by the stress detection includes at least one of tension, shear force and pressure.

[0070] During the stretching process of the photonic crystal film, the distance between the nanoparticles will change, and the modulated visible light band will also change accordingly, thereby achieving the color change of the film. At the same time, during the stretching process, the resistance of the film will also increase, causing the current at both ends of the film to decrease, realizing the dual response of the photonic crystal film to external stress (including tension, shear force, pressure, etc.) of optical signals / electrical signals.

[0071] The following will provide further explanation through specific examples.

[0072] Example 1

[0073] (1) Dissolve 2.87 g of lithium bis(trifluoromethanesulfonyl)imide in 20 mL of propylene carbonate solvent, stir magnetically until the solution becomes clear, then add 5.72 g of 4-acryloylmorpholine, 0.198 g of polyethylene glycol diacrylate, and 0.068 g of 1-hydroxycyclohexylphenyl ketone in sequence, and stir magnetically for 30 min.

[0074] (2) Weigh 0.09g of tannic acid and dissolve it in 30mL of ethylene glycol. Stir magnetically at 30℃ for 15min. Preheat the mixed solution to 135℃. During the vigorous stirring, add 5g of polyvinyl pyrrolidone to the mixed solution and continue stirring for 20min. Cool the above solution to 65℃, add 0.54g of ferric chloride hexahydrate particles, and continue stirring for 40min. Cool the above solution to 30℃, add 2.8g of sodium acetate, and continue stirring for 30min. Transfer the above solution to a 100mL hydrothermal reactor and react at 200℃ for 12h. Collect the obtained Fe3O4 magnetic nanoparticles with a magnet, pour off the supernatant, and ultrasonically disperse with ethanol. Repeat three times. Finally, disperse in 100mL of ethanol.

[0075] (3) Take 5 mL of the ethanol dispersion of Fe3O4 magnetic nanoparticles in (2), collect the magnetic nanoparticles with a magnet, and then disperse them with 5 mL of propylene carbonate. Then, collect and remove the supernatant with a magnet.

[0076] (4) Take 5 mL of the electrolyte solution in (1) to disperse the magnetic nanoparticles in (3) and sonicate for 10 min.

[0077] (5) Use a syringe to draw up the mixed solution in (4) and inject it into a 4×4×0.8cm 3 The film was placed in a glass reaction chamber, placed in a magnetic field with a magnetic induction intensity of 800 Gs for 30 seconds, and cured under ultraviolet light at a distance of 12 cm for 5 minutes to obtain a photonic crystal film.

[0078] Example 2

[0079] (1) Dissolve 1 g of lithium chloride in 7.2 mL of deionized water and stir magnetically until the solution becomes clear. Then add 1.55 g of acrylamide, 0.005 g of ammonium persulfate, and 0.002 g of N,N'-methylenebisacrylamide in sequence and stir magnetically for 30 min.

[0080] (2) Weigh 0.09g of tannic acid and dissolve it in 30mL of ethylene glycol. Stir magnetically at 30℃ for 15min. Preheat the mixed solution to 135℃. During vigorous stirring, add 5g of polyvinyl pyrrolidone to the mixed solution and continue stirring for 20min. Cool the above solution to 65℃, add 0.54g of ferric chloride hexahydrate particles, and continue stirring for 40min. Cool the above solution to 30℃, add 2.8g of sodium acetate, and continue stirring for 30min. Transfer the above solution to a 100mL hydrothermal reactor and react at 200℃ for 12h. Collect the obtained Fe3O4 magnetic nanoparticles with a magnet, pour off the supernatant, and ultrasonically disperse with deionized water. Repeat three times. Finally, disperse in 100mL of deionized water.

[0081] (3) Take 5 mL of the deionized water dispersion of Fe3O4 magnetic nanoparticles in (2), collect the magnetic nanoparticles with a magnet, and then disperse them with 5 mL of propylene carbonate. Then collect and remove the supernatant with a magnet.

[0082] (4) Take 5 mL of the electrolyte solution in (1) to disperse the magnetic nanoparticles in (3) and sonicate for 10 min.

[0083] (5) Use a syringe to draw up the mixed solution in (4) and inject it into a 4×4×0.8cm 3 The film was placed in a glass reaction chamber, placed in a magnetic field with a magnetic induction intensity of 800 Gs for 30 seconds, and cured under ultraviolet light at a distance of 12 cm for 5 minutes to obtain a photonic crystal film.

[0084] Test Example 1

[0085] (1) The morphology of the magnetic nanoparticles prepared in Example 1 of the present application was characterized. The results were as follows: Figure 1 ,Depend on Figure 1 It can be seen that the average particle size of the prepared magnetic nanoparticles is 150nm. The morphology of the prepared photonic crystal film is characterized by referring to Figure 2 .Depend on Figure 2 It can be seen that magnetic nanoparticles can form photonic crystal films in different gel electrolyte systems.

[0086] (2) The optical and electrical signals of the photonic crystal film prepared in Example 1 of the present application were characterized. Potential Window (electrochemical window) and EIS (electrochemical impedance spectroscopy) were characterized. The test instrument was Shanghai Chenhua electrochemical workstation CHI760E. The results were referenced to Figure 4-5.from Figure 4-5 It can be seen that the film has a wide electrochemical window and high ion mobility.

[0087] (3) The tensile stress-strain curve of the photonic crystal film prepared in Example 1 of the present application was tested using a universal testing machine Instron AVE 68TM-30. The results are shown in Table 1. Figure 6 .from Figure 6 It can be seen that the photonic crystal film has good elasticity.

[0088] (4) The electrical signal response of the photonic crystal film prepared in Example 1 of the present application under tensile stress was tested using a KEITHLEY 2450 Source Meter. The results were obtained by referring to Figure 7-9 .from Figure 7-9 It can be seen that the prepared photonic crystal film has sensitive sensing performance and excellent cycle life.

[0089] (5) The CIE graph of the photonic crystal film prepared in Example 1 of the present application under different tensile strains was tested using a 3nh desktop spectrophotometer YS6060. Fig.10 .from Fig.10 It can be seen that the photonic crystal film covers multiple color bands under tensile strain conditions, realizing multi-color sensing.

[0090] Test Example 2

[0091] (1) The morphology of the photonic crystal film prepared in Example 2 of the present application was characterized. The results are shown in Table 1. Figure 3 ,Depend on Figure 3 It can be seen that magnetic nanoparticles can form photonic crystal films in different gel electrolyte systems.

[0092] (2) The optical and electrical signals of the photonic crystal film prepared in Example 2 of the present application were characterized. Potential Window (electrochemical window) and EIS (electrochemical impedance spectroscopy) were characterized. The test instrument was Shanghai Chenhua electrochemical workstation CHI760E. The results were referenced to Figure 11-12 .from Figure 11-12 It can be seen that the film has a wide electrochemical window and high ion mobility.

[0093] (3) The tensile stress-strain curve of the photonic crystal film prepared in Example 2 of the present application was tested using a universal testing machine Instron AVE 68TM-30. The results are shown in Table 1. Fig.13 ,from Fig.13 It can be seen that the photonic crystal film has good elasticity.

[0094] (4) The electrical signal response of the photonic crystal film prepared in Example 2 of the present application under tensile stress was tested using a KEITHLEY 2450 Source Meter. The results were obtained by referring to Fig.14 ,from Fig.14 It can be seen that the prepared photonic crystal film has sensitive sensing performance.

[0095] In summary, the preparation method of the photonic crystal film in the present application is to mix Fe3O4 magnetic nanoparticles with a gel electrolyte precursor in a magnetic field and perform a photocuring process so that the Fe3O4 magnetic nanoparticles are oriented to form a periodic three-dimensional structure, thereby achieving a highly ordered arrangement. Further, there is a significant difference in dielectric constant and refractive index between the Fe3O4 magnetic nanoparticles themselves and the surrounding medium, thereby generating a photonic bandgap structure, which has the effect of regulating light propagation. When visible light passes through the photonic crystal film, light of a specific wavelength will be modulated by the photonic bandgap structure, resulting in light of a specific wavelength not being reflected, so only its complementary color can be observed. When the photonic crystal film is in the process of stretching, the distance between the nanoparticles will change, and the modulated visible light band will also change accordingly, thereby achieving a change in film color. In addition, during the stretching process, the resistance of the film will also increase, resulting in a decrease in the current at both ends of the film, thereby achieving a dual response of the photonic crystal film to the optical signal / electrical signal of external stress (including tension, shear force, pressure, etc.).

[0096] It should be understood that the application of the present application is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to this application.

Claims

1. A method for preparing a photonic crystal film, characterized in that: The preparation method comprises the steps of: (a) preparing a gel electrolyte precursor solution; (b) Preparation of Fe3O4 magnetic nanoparticles; (c) mixing Fe3O4 magnetic nanoparticles with a gel electrolyte precursor solution; (d) The mixed solution obtained in (c) is placed in a magnetic field and subjected to a photocuring treatment to obtain a photonic crystal film.

2. The preparation method according to claim 1, characterized in that: The preparation method of the gel electrolyte precursor solution comprises the steps of: (a1) mixing a solvent and a lithium salt to obtain a mixed solution; (a2) adding an elastic monomer, a crosslinking agent and an initiator to the mixed solution obtained in (a1), stirring and mixing, and obtaining a gel electrolyte precursor solution.

3. The preparation method according to claim 2, characterized in that: The concentration of lithium salt in the mixed solution obtained in (a1) is 0.2-2 mol / L, the molar percentage of the crosslinking agent relative to the elastic monomer in (a2) is 0.03-0.3 mol%, and the molar percentage of the initiator relative to the elastic monomer is 0.4-5 mol%; The solvent includes at least one of dimethyl sulfoxide, water, ethanol, methanol, chloroform, ethylene glycol, and N,N-dimethylformamide; the lithium salt includes at least one of lithium bis(trifluoromethanesulfonyl)imide and lithium chloride; the elastic monomer includes at least one of acrylamide and 4-acryloylmorpholine; the cross-linking agent includes at least one of polyethylene glycol diacrylate and N,N-methylenebisacrylamide; and the photoinitiator includes at least one of 1-hydroxycyclohexyl phenyl ketone and ammonium persulfate.

4. The preparation method according to claim 1, characterized in that: The specific steps of mixing in (c) include: The Fe3O4 magnetic nanoparticles are mixed with a gel electrolyte precursor solution and ultrasonically dispersed, wherein 2-15 mg of the Fe3O4 magnetic nanoparticles are dispersed in every 10 mL of the gel electrolyte precursor solution.

5. The preparation method according to claim 1, characterized in that: The specific steps of (d) include: (d1) transferring the mixed solution obtained in (c) into a reaction container; (d2) placing the reaction container under a magnetic field for 30-120 seconds to allow the Fe3O4 magnetic nanoparticles to be orderly arranged in the mixed solution, followed by photocuring to obtain the photonic crystal film.

6. The preparation method according to claim 5, characterized in that: The reaction container is selected from a glass container and an acrylic container; the thickness of the wall of the reaction container is 0.2-5 mm.

7. The preparation method according to claim 5, characterized in that: The magnetic induction intensity of the magnetic field is 150-6000Gs.

8. The preparation method according to claim 5, characterized in that: The light curing step is to irradiate the reaction container under ultraviolet light for 3-15 minutes, the distance between the ultraviolet light source and the reaction container is 3-30 cm, the wavelength of the ultraviolet light is 365-395 nm, and the power is 15-20 W.

9. A photonic crystal film prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the photonic crystal film according to claim 9 in stress detection.

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