A force unclonable tag, and a preparation method and application thereof

Abstract

The application belongs to the technical field of high polymer materials, and discloses a force-induced unclonable label and a preparation method and application thereof. Negatively charged monodisperse polymer nanospheres are prepared through emulsion polymerization, and after swelling by using isooctyl acrylate monomers, the isooctyl acrylate monomers are mixed and polymerized with acrylamide and ethylene glycol dimethacrylate to form a structural color hydrogel film through light curing. The structural color hydrogel film is pressed by using a mechanical force of a hollow steel template mold, and after volatilization of the solvent, randomly distributed microcrystalline spots are obtained, and the structural color hydrogel film exhibits a force-induced color change optical property and can be quickly and effectively identified. Compared with a traditional hydrogel anti-counterfeiting label, the label has higher stability and reusability, does not need a solvent, is environmentally friendly and practical. The technology not only realizes high-level anti-counterfeiting and encryption, but also has the potential for large-scale production.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of high polymer materials, and particularly relates to a force-induced unclonable tag and a preparation method and application thereof. BACKGROUND

[0002] A photonic crystal structure is generally an ordered structure material formed by two or more than two dielectric constant media periodically alternating in a certain space. The structure also has periodicity in the control of the refractive index of light, thereby producing a photonic band gap (PHG). When the photonic band gap produced by the photonic crystal is within the visible light band range, visible light falling in the band gap is reflected due to the inability to pass through the photonic crystal, thereby forming coherent diffraction light on the surface of the photonic crystal, so as to produce structural color in the macroscopic world. The photonic band gap is the main feature of the photonic crystal, and we can control the propagation of light by adjusting the photonic band gap, which provides an important basis for the development and breakthrough of new optical devices.

[0003] A responsive photonic crystal can easily adjust its light signal through external stimulation. By combining photonic crystal microspheres with stimulus-responsive materials, the structural color can be effectively tuned under external stimulation, laying a foundation for its application in anti-counterfeiting. Stimulus-responsive photonic crystals can be constructed by two methods: using a response material as the raw material of the photonic crystal; filling the response material into the gap of the assembled periodic structure to form a composite material. When the external physical or chemical conditions change, the responsive photonic crystal can intelligently respond to the stimulus and produce a changing light signal. Due to its adjustable structural color and visual effect in response to various external stimuli, responsive photonic crystals have been widely used in advanced anti-counterfeiting.

[0004] The concept of PUF was first proposed by Ravikanth Pappu et al. in 2002, and was named physical one-way function at that time. As a physical one-way function with inherent, unique and fingerprint-like characteristics, PUF is a unique key generated based on the inherent difference of uncontrollable variability and high randomness in the manufacturing process, even in the same manufacturing process. PUF is difficult to copy, compact in essence, and resistant to tampering. From the perspective of product security, the anti-counterfeiting and authentication hardware security technology developed based on PUF has the characteristics of low hardware resource occupation, difficult to leak product identity information, and difficult to copy product credentials even after being captured, greatly improving the security of product information authentication. At present, photonic crystals are combined with PUF to prepare a physical unclonable anti-counterfeiting tag with stable structural color, rainbow characteristics and more environmental protection. SUMMARY

[0005] In order to overcome the above-mentioned prior art for anti-counterfeiting photonic crystal hydrogel only under solvent conditions, low spectral response sensitivity, complex preparation process and unstable light spot effect, the primary purpose of the present application is to provide a preparation method of force-induced unclonable tag; the method is to apply mechanical force to the hydrogel film, and the solvent is evaporated and elastically shrunk during the solvent evaporation process to form a random light spot.

[0006] Another purpose of the present application is to provide a force-induced unclonable tag prepared by the above preparation method.

[0007] Still another purpose of the present application is to provide an application of the above force-induced unclonable tag.

[0008] The purpose of the present application is achieved by the following technical solutions:

[0009] A preparation method of a force-induced unclonable tag, comprising the following operation steps:

[0010] (1) Add an emulsifier to ultrapure water and stir until dissolved, heat to 60℃, then add butyl acrylate, methyl methacrylate and acrylamide in sequence, continue to stir and heat to 78℃, drop the aqueous solution of initiator into the reaction system drop by drop, and polymerize for 8-10h under the condition of 78℃ to obtain electronegative polybutyl acrylate colloidal microsphere emulsion;

[0011] (2) Add an emulsifier to the electronegative polybutyl acrylate colloidal microsphere emulsion obtained in step (1), and add an organic solvent for stirring and dissolution, heat to 40℃, then add oil-soluble monomers, the oil-soluble monomers are isooctyl acrylate and / or isooctyl methacrylate, and stir for 12h under the condition of 40℃; dialyze the mixed solution in ultrapure water to separate the unreacted polymer monomers, and obtain a colloidal crystal emulsion;

[0012] (3) Dissolve acrylamide, ethylene glycol dimethacrylate, N, N'-methylene bisacrylamide and polyethylene glycol diacrylate in the colloidal crystal emulsion obtained in step (2), and then add initiator 2-hydroxy-2-methylbenzene propyl ketone, and fully stir under light-proof condition to obtain a photonic crystal hydrogel precursor solution; polymerize the photonic crystal hydrogel precursor solution under ultraviolet light for 30min to obtain a structural color photonic crystal hydrogel film;

[0013] (4) Use a patterned hollow steel template to press the structural color photonic crystal hydrogel film obtained in step (3); the template is fixed by clamps around the template, and then placed in an 80℃ oven for drying for 8h, so that the solvent is completely evaporated, and a force-induced unclonable tag is obtained.

[0014] The weight fraction of the butyl acrylate in step (1) is 8-15 parts, the weight fraction of the methacrylic acid is 0.2-2 parts, the weight fraction of the acrylamide is 0.1-0.5 parts, the weight fraction of the emulsifier is 0-0.2 parts, and the weight fraction of the ultrapure water is 60-150 parts; the aqueous solution of the initiator is a 5-50% mass fraction potassium persulfate aqueous solution, and the weight fraction of the aqueous solution of the initiator is 1-3 parts.

[0015] More preferably, the weight fraction of the butyl acrylate in step (1) is 10 parts, the weight fraction of the methacrylic acid is 1.7 parts, and the weight fraction of the acrylamide is 0.3 parts; the aqueous solution of the initiator is a 33% mass fraction potassium persulfate aqueous solution, and the weight fraction is 1 part.

[0016] The weight fraction of the emulsifier in step (2) is 0.02-0.03 parts; the weight fractions of the electropositive polybutyl acrylate colloidal microsphere emulsion, the organic solvent, and the oil-soluble monomer are 6-9 parts, 1-4 parts, and 0.2-1 part, respectively, and are preferably 8 parts, 2 parts, and 0.8 parts, respectively. The organic solvent is anhydrous ethanol.

[0017] In step (3), the weight fractions of the acrylamide, ethylene glycol dimethacrylate, N, N'-methylene bisacrylamide, polyethylene glycol diacrylate, and colloidal crystal emulsion are 0.5-2 parts, 0.1-0.5 parts, 0.02-0.6 parts, 0.01-0.1 parts, and 0.2-0.8 parts, respectively, and are preferably 0.2 parts, 0.02 parts, 0.1 parts, 0.05 parts, 0.5 parts, and 0.8 parts, respectively; the initiator is 2-hydroxy-2-methylpropiophenone; and the total mass of the acrylamide, ethylene glycol dimethacrylate, N, N'-methylene bisacrylamide, and polyethylene glycol diacrylate, and the mass of the initiator, are in a ratio of 100:(0.5-2), and preferably 100:1.

[0018] The emulsifier in step (1) or step (2) is sodium dodecyl sulfate or sodium dodecylbenzenesulfonate; and the particle size of the electropositive polybutyl acrylate colloidal microsphere emulsion obtained in step (1) is 130-230 nm.

[0019] In step (4), the size of the patterned hollow steel template is 1.5×1.5×0.1 mm.

[0020] The electro-negative polybutyl acrylate colloidal microsphere emulsion in step (1) is any one or more of poly(butyl acrylate-methacrylic acid-acrylamide) nanospheres, poly(methyl methacrylate-butyl acrylate-acrylic acid) nanospheres, poly(styrene-butyl acrylate-methacrylic acid) nanospheres, poly(methyl methacrylate-methyl acrylate-acrylic acid) nanospheres, poly(styrene-acrylic acid) nanospheres, poly(styrene-methyl methacrylate-methacrylic acid) nanospheres, and preferably poly(butyl acrylate-methacrylic acid-acrylamide) nanospheres.

[0021] A force-induced unclonable tag prepared by the preparation method.

[0022] The force-induced unclonable tag is used in the fields of optical encryption anti-counterfeiting and rapid identification, force-induced sensor, and structural color patterned.

[0023] Principle of the application:

[0024] The force-induced unclonable tag is prepared by using electro-negative monodisperse polymer nanospheres as the construction unit of the microcrystal region.

[0025] Compared with the prior art, the application has the following advantages and effects:

[0026] (1) In the preparation method, the oil-soluble monomer in the microspheres participates in the polymerization of the water-soluble monomer in the hydrogel polymerization process, forming a polymer network structure penetrating through the oil-water two phases, thereby obtaining a strong interaction force between the microspheres and the base hydrogel, and realizing good mechanical properties with high tensile strength and high strength.

[0027] (2) The preparation method is simple in process, mild and controllable in condition, and can produce high-strength photonic crystal hydrogel material with excellent optical properties and tensile property, and is suitable for popularization and application in the field of high polymer materials.

[0028] (3) The high-strength photonic crystal hydrogel prepared by the method has the optical property of force-induced color change, and can randomly generate bright and stable light spots and be applied to optical encryption and anti-counterfeiting. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 It is a scanning electron microscope image of the force-induced unclonable tag of examples 1-3, wherein a-c are surface morphology images of examples 1-3 under different magnifications of the scanning electron microscope.

[0030] Figure 2 It is an atomic force microscope image of the force-induced unclonable tag of examples 1-3, wherein a is a surface morphology image of example 1, c is an atomic force microscope morphology image of the junction of red and green color light spots, b is a local magnification atomic force microscope morphology image of the red light spot, and d is a local magnification atomic force microscope morphology image of the green light spot.

[0031] Figure 3 It is a light spot microscope magnification image of the force-induced unclonable tag of examples 1-3 in a completely dry state, wherein a-c are circular patterns on the force-induced unclonable tag, and d-f are U-shaped patterns on the force-induced unclonable tag.

[0032] Figure 4 It is a reflection spectrum image of the force-induced unclonable tag of examples 1-3.

[0033] Figure 5 It is a stress-strain curve image of the force-induced unclonable tag of examples 1-3.

[0034] Figure 6 It is different patterning of the force-induced unclonable tag of examples 1-3, wherein a and d are structural color photonic crystal hydrogel films obtained under ultraviolet light polymerization, b and e are two patterned force-induced unclonable tags with complete solvent evaporation, c and f are corresponding local magnification images. DETAILED DESCRIPTION

[0035] The content of the present application will be further illustrated in combination with specific examples, but should not be understood as a limitation to the present application.

[0036] The experimental methods used in the following examples are conventional methods unless otherwise specified; and the materials, reagents, etc. used are reagents and materials that can be obtained commercially unless otherwise specified.

[0037] The parts in the following examples are all parts by weight.

[0038] Example 1

[0039] A method for preparing a force-unclonable tag, comprising the following steps:

[0040] (1) Preparation of poly(butyl acrylate-methacrylic acid-acrylamide) nanospheres: 0.012 parts of sodium dodecyl sulfate was added to 150 parts of deionized water and stirred to dissolve, the stirring speed was set to 2000 r / min, inert gas was introduced for 30 min, and then 15 parts of butyl acrylate, 1.5 parts of methacrylic acid and 0.5 parts of acrylamide were added in sequence after heating to 60℃, and the stirring was continued until the temperature reached 78℃, then 1 part of 33% mass concentration of potassium persulfate aqueous solution was added, and the uniform stirring was maintained at 78℃ for 8 h, and the obtained poly(butyl acrylate-methacrylic acid-acrylamide) nanospheres were the electropositive polybutyl acrylate colloidal microsphere emulsion.

[0041] (2) 0.025 parts of sodium dodecyl sulfate was added to 10 parts of the electropositive polybutyl acrylate colloidal microsphere emulsion prepared in step (1) and 1.5 parts of anhydrous ethanol mixed solution and stirred to dissolve, the stirring speed was set to 800 r / min, and then 0.9 parts of isooctyl acrylate was added after heating to 40℃, and the uniform stirring was maintained at 40℃ for 12 h; then the obtained solution was dialyzed in deionized water for 48 h to remove organic solvents and small molecule substances, and an oil-soluble monomer-swollen colloidal crystal emulsion with a diameter of 180 nm was obtained;

[0042] (3) 0.5 parts of acrylamide was dissolved in 0.56 parts of the colloidal crystal emulsion prepared in step (2), and then 0.02 parts of ethylene glycol dimethacrylate, 0.02 parts of N, N'-methylenebisacrylamide and 0.1 parts of polyethylene glycol diacrylate were added, and 0.0015 parts of initiator 2-hydroxy-2-methylpropionphenone was added, and the mixture was stirred under light-proof conditions to obtain a photonic crystal hydrogel precursor solution; the precursor solution was injected into a sandwich mold with a spacing of 0.5 mm, and the polymerization reaction was carried out under a UV lamp for 30 min, and then the mold was removed to obtain a structural color photonic crystal hydrogel film;

[0043] (4) The structural color photonic crystal hydrogel film obtained in step (3) was pressed using a patterned hollow steel template (with a size of 1.5×1.5×0.1 mm); the template was fixed by clamps around the template, and then placed in an 80℃ oven for drying for 8 h, so that the solvent was completely volatilized, and a force-unclonable tag was obtained.

[0044] Example 2

[0045] A method for preparing a force-unclonable tag, comprising the following steps:

[0046] (1) Preparation of poly(butyl acrylate-methyl methacrylate) nanospheres: 0.01 parts of sodium dodecyl sulfate was added to 80 parts of deionized water and 25 parts of anhydrous ethanol and stirred to dissolve, the stirring speed was set to 2000 r / min, inert gas was introduced for 30 min, heated to 60℃, then 10 parts of butyl acrylate and 1 part of methyl methacrylate were added in turn, and the stirring was continued until the temperature reached 78℃, then 1 part of 33% mass concentration of potassium persulfate aqueous solution was added, and the uniform stirring was maintained at 78℃ for 8h to obtain a polymer colloidal crystal emulsion.

[0047] (2) 0.025 parts of sodium dodecyl sulfate was added to 10 parts of the electropositive polybutyl acrylate colloidal microsphere emulsion prepared in step (1) and 1.5 parts of anhydrous ethanol mixed solution and stirred to dissolve, the stirring speed was set to 800 r / min, heated to 40℃, then 0.9 parts of isooctyl acrylate was added, and the uniform stirring was maintained at 40℃ for 12h; the obtained solution was dialyzed in deionized water for 48h to remove organic solvents and small molecule substances, and an oil-soluble monomer-swollen colloidal crystal emulsion with a diameter of 210nm was obtained;

[0048] (3) 0.1 parts of acrylamide was dissolved in 0.56 parts of the colloidal crystal emulsion prepared in step (2), then 0.02 parts of ethylene glycol dimethacrylate, 0.01 parts of N,N'-methylenebisacrylamide and 0.02 parts of polyethylene glycol diacrylate were added, and 0.0015 parts of initiator 2-hydroxy-2-methylpropiophenone was added, and the mixture was stirred under light-proof conditions to obtain a photonic crystal hydrogel precursor solution; the precursor solution was injected into a sandwich mold with a spacing of 0.5mm, and the polymerization reaction was carried out under a UV lamp for 30min, and after demolding, a structural color photonic crystal hydrogel film was obtained;

[0049] (4) The structural color photonic crystal hydrogel film obtained in step (3) was pressed using a patterned hollow steel template (size 1.5×1.5×0.1mm); the template was fixed around the four corners with a clamp and placed in an 80℃ oven for drying for 8h, so that the solvent was completely volatilized, and a force-induced unclonable tag was obtained.

[0050] Example 3

[0051] (1) Preparation of poly(butyl acrylate-methyl methacrylate) nanospheres: 0.01 parts of sodium dodecyl sulfate was added to 80 parts of deionized water and 25 parts of anhydrous ethanol and stirred to dissolve, the stirring speed was set to 2000 r / min, inert gas was introduced for 30 min, heated to 60℃, then 10 parts of butyl acrylate and 1 part of methyl methacrylate were added in turn, and the stirring was continued until the temperature reached 78℃, then 1 part of 33% mass concentration of potassium persulfate aqueous solution was added, and the uniform stirring was maintained at 78℃ for 8h to obtain a polymer colloidal crystal emulsion.

[0052] (2) 0.03 parts of sodium dodecyl sulfate was added into 12 parts of the electropositive polybutyl acrylate colloidal microsphere emulsion prepared in step (1) and 1.5 parts of anhydrous ethanol mixed solution, and stirred and dissolved, the stirring speed was set to 800 r / min, after heating to 40℃, 0.9 parts of isooctyl acrylate was added, and kept at 40℃ for 12 hours of uniform stirring; then the obtained solution was dialyzed in deionized water for 48 hours to remove organic solvents and small molecule substances, and an oil-soluble monomer swollen colloidal crystal emulsion with a diameter of 200 nm was obtained;

[0053] (3) 0.05 parts of acrylamide was dissolved into 0.56 parts of the colloidal crystal emulsion prepared in step (2), then 0.02 parts of ethylene glycol dimethacrylate, 0.01 parts of N, N'-methylene bisacrylamide and 0.02 parts of polyethylene glycol diacrylate were added, and 0.0015 parts of initiator 2-hydroxy-2-methylpropiophenone was added, and stirred under light-proof condition, to obtain a photonic crystal hydrogel precursor solution; the precursor solution was injected into a sandwich mold with a spacing of 0.5 mm, and polymerized under ultraviolet lamp for 30 min, and after demolding, a structural color photonic crystal hydrogel film was obtained;

[0054] (4) The structural color photonic crystal hydrogel film obtained in step (3) was pressed using a patterned hollow steel template (size 1.5×1.5×0.1 mm), and the four sides were fixed with clamps, then placed in an oven at 80℃, and dried for 8 hours, and then demolded to obtain a force-induced unclonable tag.

[0055] Comparative Example 1

[0056] (1) Preparation of poly (polystyrene-methyl methacrylate) nanospheres: 0.012 parts of sodium dodecyl sulfate was added into 85 parts of deionized water and stirred and dissolved, the stirring speed was set to 2000 r / min, and inert gas was introduced for 30 min, and then 15 parts of styrene and 1.5 parts of methyl methacrylate were added after heating to 60℃, and 0.1 parts of 33% mass concentration of potassium persulfate aqueous solution was added when the temperature was kept at 78℃, and the uniform stirring was kept for 8 hours, and a polymer colloidal crystal emulsion was obtained.

[0057] (2) 0.5 parts of acrylamide was dissolved into 0.56 parts of the electropositive polybutyl acrylate colloidal microsphere emulsion prepared in step (2), then 0.02 parts of ethylene glycol dimethacrylate, 0.01 parts of N, N'-methylene bisacrylamide and 0.02 parts of polyethylene glycol diacrylate were added, and 0.0015 parts of initiator 2-hydroxy-2-methylpropiophenone was added, and stirred under light-proof condition, to obtain a photonic crystal hydrogel precursor solution; the precursor solution was injected into a sandwich mold with a spacing of 0.5 mm, and polymerized under ultraviolet lamp for 30 min, and after demolding, a structural color photonic crystal hydrogel film was obtained;

[0058] (3) Using a patterned hollow steel template (1.5 x 1.5 x 0.1 mm in size) to press the structural color photonic crystal hydrogel film obtained in step (2); the template was fixed by clamps around the four sides and placed in an 80°C oven to dry for 8 h, so that the solvent was completely volatilized, thereby obtaining the force-induced unclonable tag.

[0059] Test Example 1

[0060] 1. Scanning Electron Microscope

[0061] Experimental procedure: The force-induced unclonable tags of Examples 1-3 were broken by liquid nitrogen and then pasted on the electron microscope stage with conductive glue, dried in an 80°C oven for 12 h, and finally observed under a field emission scanning electron microscope to observe the micro-morphology of the tags (magnification 20K).

[0062] Result analysis: The surface morphology of the force-induced unclonable tags of Examples 1-3 is shown in Figure 1 As can be seen from Figure 1 , the microspheres in the force-induced unclonable tag have regular morphology, uniform particle size, and are arranged in order.

[0063] 2. Atomic Force Microscope

[0064] Experimental procedure: The force-induced unclonable tags of Examples 1-3 were cut to the appropriate size after drying in an 80°C oven and pasted on a glass sheet, and finally observed under an atomic force microscope to observe the micro-morphology of the tags.

[0065] Result analysis: The micro-morphology of the force-induced unclonable tags of Examples 1-3 was photographed using an atomic force microscope, as shown in Figure 2 As can be seen from Figure 2 , the microspheres in the force-induced unclonable tag have regular morphology, uniform particle size, and are arranged in order. As can be seen from , the force-induced unclonable tag produces color spots of different colors due to mechanical force, and the distance between the microspheres corresponds to the color thereof by the Bragg diffraction formula.

[0066] 3. Spot effect diagram

[0067] Experimental procedure: The completely dried force-induced unclonable tags of Examples 1-3 were placed under an optical microscope, and photographs were taken using the microscope under the irradiation of a 45° light beam.

[0068] Figure 3 Result analysis: The force-induced unclonable tags of Examples 1-3 were photographed using an optical microscope, and the photographs obtained are shown in Figure 3 As can be seen from Figure 3 , the force-induced unclonable tags of Examples 1-3 were prepared. As can be seen from , the polymer film of Examples 1-3 was subjected to mechanical force, and after the solvent was volatilized, a plurality of color spots of different colors appeared, and the size of the force-induced unclonable tags prepared was uniform.

[0069] 4. Reflectance Spectrum Test

[0070] Experimental procedure: The force-induced non-cloning tag from Example 1 was placed on the sample stage and tested using a high-performance spectrophotometer.

[0071] Results Analysis: The reflectance spectrum of the force-induced non-clonable tag in Example 1 is shown below. Figure 4 As shown, under the condition that the force-induced non-cloneable label is kept completely dry, different wavelengths of reflection peaks can be measured at different locations in a sample, proving that different locations in the force-induced non-cloneable label possess different colors. The disordered light spot pattern endows the photonic crystal film anti-counterfeiting label with the property of being non-cloneable, and combined with artificial intelligence, the anti-counterfeiting label can be identified and its information read.

[0072] 5. Universal testing machine

[0073] Experimental procedure: Place the force-induced non-cloning label from Example 1 on a multi-testing machine and test it using the multi-testing machine.

[0074] Results Analysis: The stress-strain curve of the force-induced non-clonable tag in Example 1 is as follows: Figure 5 As shown. Under the condition of keeping the force-induced non-clonable tag completely dry, the sample possesses certain mechanical properties and can be used in a variety of environments and scenarios.

[0075] 6. Patterned effect image

[0076] Experimental procedure: Place the undried and fully dried force-induced non-cloneable tags of Examples 1 to 3 under an optical microscope, and take pictures and store them under a 45° light beam.

[0077] Results Analysis: The formation process of the force-induced non-clonable tags obtained in Examples 1-3 was photographed using an optical microscope. The resulting images are shown below. Figure 6 As shown in the figures, Figures a and d are structural color photonic crystal hydrogel films obtained under ultraviolet light polymerization, Figures b and e are two patterned force-induced non-cloning tags after the solvent has completely evaporated under mechanical force, and Figures c and f are corresponding magnified views. It can be seen that under the continuous action of mechanical force, the force-induced non-cloning tags produce random multi-colored light spots after the solvent evaporates.

[0078] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method of preparing a physically unclonable tag, characterized by The method comprises the following steps: (1) adding an emulsifier into ultrapure water and stirring until dissolved, then adding butyl acrylate, methacrylic acid and acrylamide in sequence after heating to 60℃, continuing to stir and heat to 78℃, adding an aqueous initiator solution drop by drop into the reaction system, and polymerizing for 8-10 hours at 78℃ to obtain an electropositive polybutyl acrylate colloidal microsphere emulsion; (2) adding an emulsifier into the electropositive polybutyl acrylate colloidal microsphere emulsion obtained in step (1) and stirring to dissolve after adding an organic solvent, then adding an oil-soluble monomer after heating to 40℃, the oil-soluble monomer being isooctyl acrylate and / or isooctyl methacrylate, and stirring for 12 hours at 40℃; placing the mixed solution in ultrapure water for dialysis to separate unreacted polymer monomers, and obtaining a colloidal crystal emulsion; (3) dissolving acrylamide, ethylene glycol dimethacrylate, N,N'-methylene bisacrylamide and polyethylene glycol diacrylate in the colloidal crystal emulsion obtained in step (2), then adding an initiator 2-hydroxy-2-methylpropiophenone, and fully stirring under light shielding conditions to obtain a photonic crystal hydrogel precursor solution; polymerizing the photonic crystal hydrogel precursor solution under ultraviolet light for 30 minutes to obtain a structural color photonic crystal hydrogel film; (4) pressing the structural color photonic crystal hydrogel film obtained in step (3) using a patterned hollow steel template; fixing the template around with a clamp, placing it in an oven at 80℃ for drying for 8 hours to completely evaporate the solvent, and obtaining a force-induced unclonable tag.

2. A method of preparing a force-unclonable tag according to claim 1, characterized in that: In step (1), the weight fraction of butyl acrylate is 8-15 parts, the weight fraction of methacrylic acid is 0.2-2 parts, the weight fraction of acrylamide is 0.1-0.5 parts, the weight fraction of the emulsifier is 0-0.2 parts, and the weight fraction of ultrapure water is 60-150 parts; the aqueous initiator solution is a 5-50% potassium persulfate aqueous solution, and the weight fraction of the aqueous initiator solution is 1-3 parts.

3. The method of claim 1, wherein the method comprises: In step (2), the weight fraction of the emulsifier is 0.02-0.03 parts; the weight fractions of the electropositive polybutyl acrylate colloidal microsphere emulsion, the organic solvent and the oil-soluble monomer are 6-9 parts, 1-4 parts and 0.2-1 part respectively.

4. The method of claim 1, wherein: In step (3), the weight fractions of acrylamide, ethylene glycol dimethacrylate, N,N'-methylene bisacrylamide, polyethylene glycol diacrylate and the colloidal crystal emulsion are 0.5-2 parts, 0.1-0.5 parts, 0.02-0.6 parts, 0.01-0.1 parts and 0.2-0.8 parts respectively; the total mass of acrylamide, ethylene glycol dimethacrylate, N,N'-methylene bisacrylamide and polyethylene glycol diacrylate is 100: (0.5-2) of the mass of the initiator.

5. The method of claim 1, wherein: In step (1) or step (2), the emulsifier is sodium dodecyl sulfate or sodium dodecylbenzenesulfonate; the particle size of the electropositive polybutyl acrylate colloidal microsphere emulsion obtained in step (1) is 130-230 nm.

6. The method of claim 1, wherein: In step (4), the size of the patterned hollow steel template is 1.5×1.5×0.1 mm.

7. A force-induced unclonable tag prepared by the method of any one of claims 1-6.

8. Use of the force-induced unclonable tag of claim 7 in the field of optical encryption anti-counterfeiting and rapid identification, the field of force-induced sensors, and the field of structural color modulation patterning.

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