Chaotic metasurface chip based on electrospun fiber surface nano-grating and method for generating and reconstructing keys by using the chip

Abstract

The application belongs to the technical field of information security device preparation, and particularly relates to a chaotic metasurface chip based on electrospun fiber surface nano-grating embossing and a method for generating and reconstructing a key by using the chip. The chaotic metasurface chip is obtained after constructing a grating metasurface on the surface of an electrospun fiber membrane, and the chaotic metasurface chip comprises, from bottom to top, a substrate layer, a reflection layer, an electrospun fiber layer, a nano-grating layer, a dye layer and a protective layer. The chip prepared by using the application can generate and reconstruct a key with high randomness and uniqueness, and the key entropy source is the joint action of two processes: the instability stretching and bending of the droplet in the electrospinning process in the electrostatic field and the micro-curved surface dependence of the conformal transfer rate in the nano-embossing process, so that a key with super-high spatial storage capacity can be generated, and the key space storage capacity can exceed 10 12 bit / cm 2 .

Description

Technical Field

[0001] This invention belongs to the field of information security device fabrication technology, specifically relating to a chaotic metasurface chip based on an imprinted nanograting on the surface of electrospun fibers, and a method for generating and reconstructing keys using this chip. Background Technology

[0002] Key generation and distribution are bottleneck challenges in information security infrastructure. Employing physical entity-based cryptographic techniques to generate and distribute keys to reduce key management risks and enhance security is currently a hot topic in international information security technology development. Typical examples of physical cryptography include quantum key distribution (QKD) and physically unclonable functions (PUFs). PUFs can be used as hash functions for product anti-counterfeiting and authentication, and as random number generators for key production. Due to their randomness, PUFs can be used to generate random numbers and then encapsulate them into various keys. Because each PUF device is unique and cannot be cloned, it functionally functions as a cryptographic algorithm with a "key" (a black box). Although neither legitimate users nor attackers can detect this "key," the party possessing the device can exclusively use the black box functionality to deploy the key.

[0003] In recent years, PUF devices can be divided into electrical SRAM-PUF and optical PUF. The former obtains a key sequence by acquiring a stable electrical noise sequence PUF, while the latter generates unique and random keys through optical response or optical image. Optical PUF keys based on unclonable patterns mainly include optical speckle (Pappu, R., Physical One-Way Functions. Science, 2002. 297(5589): p. 2026-2030.), fluorescent microparticles (Hu, YW, et al., Flexible and Biocompatible Physical Unclonable Function Anti‐Counterfeiting Label. Advanced Functional Materials, 2021. 31(34): p. 2102108.), quantum dots (CN110784312A), plasmonic nanoparticles (Smith, JD, et al., Plasmonic Anticounterfeit Tagswith High Encoding Capacity Rapidly Authenticated with Deep Machine Learning. ACS Nano, 2021. 15(2): p. 2901-2910.), and Raman responses (Gu, Y., et al., Gap-enhanced Raman tags for physically unclonable (anticounterfeitinglabels. Nature Communications, 2020. 11(1): p. 516). However, these optical speckles or particles are generated based on the Brownian motion of the dispersion liquid, and will inevitably face the problem of poor dispersion and aggregation, resulting in unstable and unrobust key generation sequences.

[0004] Some random fibers possess unique fiber distribution characteristics, such as fiber quantity, intersections, and short fiber apexes. These characteristics have gradually been applied in the field of non-cloning anti-counterfeiting, as seen in invention patent applications such as "A method and system for identifying anti-counterfeiting marks based on random fiber texture" (CN113128406A), "A fiber for random texture anti-counterfeiting and its random texture anti-counterfeiting mark" (CN107798993A), "A fragile anti-counterfeiting label of oriented randomly arranged fibers and its preparation method" (CN109461366A), "A method for constructing a database of random fiber code anti-counterfeiting based on image processing" (CN104536999A), "A method for anti-counterfeiting of randomly distributed fibers and their materials" (CN101748659A), "A sampling method for anti-counterfeiting of random fiber distribution" (CN 1591520A), and "Micro-nano optical non-cloning anti-counterfeiting marks based on electrospun nanofiber cloth and their preparation method and application" (CN 113293448A). The random fibers described above all utilize the fiber's image directly as an anti-counterfeiting identifier or code, but this remains a gap in the fields of key and random number generation. Furthermore, the use of random fibers for anti-counterfeiting and encryption relies solely on single optical responses such as reflection or fluorescence, resulting in a low level of encryption.

[0005] Patent application CN110784312A discloses a method for fabricating a PUF device and its key generation method. This method synthesizes PbS quantum dots using readily available and inexpensive chemical substances such as sulfur (S), lead dichloride (PbCl2), oleylamine (OLA), methanol, and toluene, and then fabricates the PUF device. The distribution of PbS quantum dots in the PUF device originates from the Brownian motion of nanoparticles in solution. The distribution of PbS quantum dots exhibits high uniqueness and randomness. Using the graythresh and im2bw functions in MATLAB software, the distribution map of PbS quantum dots inside the PUF device is converted into a black-and-white image via TEM. Pixel identification is then performed to obtain an initial key. The initial key is then processed by Von Neumann architecture to group the data into the final key. The advantages of this method are the readily available raw materials for PUF device fabrication and the ability to generate keys with high randomness and uniqueness. The disadvantages are that limitations imposed by quantum dot size, single-particle brightness, single-particle scintillation, photobleaching, and spatial positioning conditions lead to poor readability of the quantum dot PUF device. Summary of the Invention

[0006] This invention provides a chaotic metasurface chip based on an electrospun fiber surface imprinted with a nanograting, and a method for generating and reconstructing keys using this chip. The chip prepared using this invention can generate and reconstruct keys with high randomness and uniqueness. The chaotic metasurface chip is obtained by constructing a nanograting metasurface on the surface of an electrospun fiber film. The chaotic metasurface chip includes, from bottom to top, a substrate, a reflective layer, an electrospun fiber layer, a nanograting layer, a dye layer, and a protective layer. The electrospun fiber layer is made of electrospun polymers and / or semiconductor fibers; the nanograting layer is made by soft imprinting with plasmonic metals or luminescent nanoparticles; the dye layer is made of luminescent or light-absorbing materials; and the protective layer is a transparent encapsulation layer. The chip prepared using this invention can generate and reconstruct keys with high randomness and uniqueness. The key entropy source has two components: the instability, stretching, and bending of droplets in the electrostatic field during the electrospinning process, and the micro-surface dependence of the conformal transfer rate during the nanoimprinting process. This allows for the generation of keys with ultra-high spatial storage capacity, exceeding 10^64 keys. 12 bit / cm 2 .

[0007] The present invention adopts the following technical solution: The chaotic metasurface chip (electrospun paper chip) based on the imprinting of nanogratings on the surface of electrospun fiber is obtained by constructing a grating metasurface on the surface of an electrospun fiber membrane. The chaotic metasurface chip includes a substrate layer, a reflective layer, an electrospun fiber layer, a nanograting layer, a dye layer and a protective layer arranged sequentially from bottom to top. The substrate is made of a smooth (roughness Ra≤0.2μm) transparent optical material, such as glass, quartz, polyimide or polyester substrate.

[0008] The reflective layer is made of aluminum, silver or gold, with a thickness of 30-300 nm and a reflectivity of over 80%.

[0009] The electrospun fiber layer is specifically made of electrospun polymer and / or semiconductor fiber, and is prepared by electrospun process. The thickness of the electrospun fiber layer is 10-300 μm. The nanograting layer is prepared by soft imprinting of plasmonic metals or luminescent nanoparticles. The thickness of the nanograting layer is related to the number of plasmonic metal or luminescent nanoparticle layers. For example, if 1 to 3 layers of plasmonic metals or luminescent nanoparticles are used, with each layer being 50 nm, then the thickness of the nanograting obtained after conformal transfer of plasmonic metals or luminescent nanoparticles is 50 nm to 150 nm.

[0010] The dye layer is made of luminescent or light-absorbing materials, specifically organic dyes, quantum dots, carbon dots, rare earth nanoparticles, or optoelectronic polymers.

[0011] In the above-mentioned electrospun paper chips: The polymer of the electrospun fiber layer is preferably one or more of the following, which have good light transmittance: polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polymethyl methacrylate (PMMA), polystyrene (PS), polyethylene oxide (PEO), polyacrylonitrile (PAN), cellulose ester, nylon-6, polyvinyl chloride (PVC), and polylactic acid. The semiconductors in the electrospun fiber layer are preferably one or more of titanium oxide (TiO2), indium oxide (In2O3), tin oxide (SnO2), cobalt oxide (Co3O4), zinc oxide (ZnO), and barium titanate (BaTiO3), which have excellent photoelectric properties. The plasmonic metal used in the nanograting layer is preferably gold or silver; the luminescent nanoparticles are preferably rare earth nanoparticles or semiconductor nanoparticles. The organic dyes in the dye layer can be coumarin, rhodamine, anthocyanin, or fluorescein dyes; the semiconductor quantum dots can be core-shell quantum dots (QDs); the carbon dots can be citrate-urea-based carbon dots, phenylenediamine-type carbon dots, glucose-type carbon dots, or polyphenol-based carbon dots; the rare earth nanoparticles can be upconversion rare earth β-NaYF4: 18%Yb: 2%Er nanoparticles; and the photopolymer can be the red light conjugated polymer MEH-PPV. The protective layer is encapsulated using polydimethylsiloxane (PDMS), epoxy resin, or polycarbonate (PC).

[0012] The above-mentioned method for preparing electrospun paper chips includes the following steps: (1) Preparation of reflective layer: A reflective layer is formed by uniformly depositing a metal such as aluminum, silver, or gold on a glass, quartz, polyimide, or polyester substrate using vacuum evaporation, magnetron sputtering, electroplating, or chemical deposition methods.

[0013] (2) Preparation of electrospun fiber layer: Electrospun fiber layers are prepared by electrospun polymers and / or semiconductor nanofibers using an electrospun process.

[0014] The following options are included: The electrospinning polymer was dissolved in a solvent and then stirred vigorously at 40°C for 5 h to obtain an electrospinning solution. The final polymer concentration was between 0.1% and 3 wt%. The solvent was a liquid capable of dissolving the corresponding polymer, such as phosphoric acid and acetic acid for nylon-6, DMSO and trifluoroacetic acid for PAN, hexafluoroisopropanol for PCL, water for PEO, DMF and chloroform for PLA, THF and DMF for PLGA, DMF and toluene for PS, THF and DMF for PVC, and ethanol and water for PVP. The spinning solution was then injected into a syringe, a needle was attached, and fixed to a push pump. The substrate / reflective layer obtained in step (1) was used as the receiving substrate. The distance between the needle and the receiving substrate was controlled to be 20 cm, the voltage to be 14 kV, the push pump speed to be 12 mL / h, and the spinning time to be 6 h. The substrate / reflective layer / electrospinned fiber layer device was obtained by electrospinning technology.

[0015] Alternatively, using the substrate / reflective layer obtained in step (1) above as the receiving substrate, a composite nanofiber membrane is prepared by electrospinning of the polymer and semiconductor fiber mixture. The prepared composite nanofiber membrane is then heat-treated to obtain a substrate / reflective layer / electrospinned fiber layer device. The polymer mentioned above is a polymer composite fiber doped with a high concentration of semiconductors. Due to the high concentration of semiconductors doped in the polymer (10wt%~35wt%), the composite fiber still possesses semiconductor properties.

[0016] Alternatively, using the substrate / reflective layer obtained in step (1) above as the receiving substrate, a substrate / reflective layer / electrospun fiber layer device can be prepared by electrospinning semiconductor nanofibers.

[0017] (3) Conformal transfer nanograting metasurface on fiber paper surface: The nanoparticle thin film assembly-conformal transfer technology is used to first assemble plasmonic metal nanoparticles or luminescent nanoparticles into a thin film through the interface, and then the nanoparticle thin film is conformally transferred from the water surface to the surface of the electrospun nanofiber layer described in (2) through a micro-nano structure PDMS stamp to form a nano grating layer.

[0018] (4) A dye layer is prepared on the surface of the nanograting layer by electrostatic adsorption; (5) Protective layer encapsulation: A layer of PDMS or epoxy resin encapsulant is encapsulated on top of the dye layer described in (4) by homogenization.

[0019] The method for generating keys using the above-mentioned electrospun paper chip includes the following: (1) Feature extraction: Microscopic optical images of the electrospun paper security chip were acquired using dark-field optical microscopy, upright / inverted fluorescence microscopy, laser confocal fluorescence microscopy, and laser confocal Raman microscopy. The images were then preprocessed, including segmentation, standardization, and enhancement.

[0020] (2) Key generation: Keys can be generated using perceptual hashing, differential hashing, mean hashing, Gabor transform, Hough transform, or machine learning.

[0021] The beneficial effects of this invention are as follows: The key generation method of the present invention has the advantage that it utilizes electrospun random nanofibers and their surface conformally transferred nanogratings to construct a chaotic metasurface, and extracts the intrinsic entropy of the chaotic device through an optical microscope to generate an encryption key with high randomness, strong uniqueness and high storage density.

[0022] Compared to previously reported nano-PUF devices, the entropy originates from high-dimensional features, resulting in a larger key space, reaching 5. 300 The above; compared with the applicant's previous patent (application publication number CN 113293448A), the storage density has also been greatly improved, from less than 0.1 Tbit / mm². 3 Increased to 10Tbit / mm 3 The above achieves laser reading and integrability. Attached Figure Description

[0023] Figure 1 A schematic diagram of the structure of an electrospun paper chip; Figure 2 This is a picture of an actual electrospun paper chip; Figure 3 It is a scanning microscope image of a single fingerprint on an electrospun paper chip; Figure 4 This is a dark-field optical microscope image of a single fingerprint on an electrospun paper chip; Figure 5 It is a two-dimensional random key obtained by a feature extraction algorithm; Figure 6 It is the intra-chip and inter-chip Hamming distance distribution of the 20 sets of one-dimensional random keys in step 6 of the embodiment. Detailed Implementation

[0024] The present invention will now be described in more detail through specific embodiments to facilitate understanding of the technical solution of the present invention, but this is not intended to limit the scope of protection of the present invention.

[0025] The silver nanocubes, electrospinning polymers, and dyes used in the following examples are all commercially available products.

[0026] The method for fabricating chaotic metasurface chips (electrospun paper chips) based on nanogratings imprinted on the surface of electrospun fibers includes: (1) Conformal transfer of metal nanogratings on the surface of electrospun nanofibers: First, a substrate with a metal reflective layer is fixed to one end of the receiver of an electrospinning apparatus. An electrospun fiber film is then fabricated on the surface of the metal reflective layer using an electrospinning process. A nanograting is then fabricated on the surface of the electrospun fiber layer using a thin-film assembly-transfer process, completing the core fabrication of the electrospun paper chip (chaotic metasurface chip).

[0027] (2) Dye layer adsorption: A dye layer is prepared on the surface of a nanograting layer by electrostatic adsorption. The dye layer is made of organic dyes, quantum dots, carbon dots, rare earth nanoparticles or optopolymers.

[0028] (3) Packaging: Finally, the entire device is encapsulated and protected with transparent encapsulating adhesive.

[0029] The specific fabrication steps for the electrospun paper chip are as follows: Step 1: Preparation of the electrospun fiber layer: Option 1: Preparation of PVP / PAN electrospun fiber layer (1) Cut a 0.7 mm thick PET film into a 2.5 cm x 2.5 cm sheet. Use vacuum evaporation technology to deposit a 100 nm thick aluminum reflective layer on the surface of the sheet to obtain a receiving substrate. Fix the receiving substrate on the receiver of the electrospinning machine and wait for spinning.

[0030] (2) Weigh 0.25g of polyvinylpyrrolidone (PVP) (K30, 1300kDa) and 0.75g of polyacrylonitrile, and dissolve them in 9mL of dimethyl sulfoxide (DMF). Stir vigorously at 40℃ for 5 h to mix them evenly and obtain the spinning solution.

[0031] (3) Inject the spinning solution into a 5mL syringe, attach a No. 21 needle, and then fix it on the push pump. Adjust the distance between the needle and the substrate receiving the above (1) to 20cm, the voltage to 14kV, the push speed of the push pump to 12mL / h, and the spinning time to 6h. Use electrospinning process to obtain electrospinned nanofiber membrane: PVP / PAN fiber membrane. (4) Place the PVP / PAN fiber membrane on a heating table and heat the table to 90 °C. Spray a 1 wt% ammonium persulfate aqueous solution evenly onto the fiber membrane. Then dry the fiber membrane in a drying oven at 80 °C for 6 h. The ammonium persulfate is a crosslinking agent used to crosslink PVP / PAN, enhancing mechanical strength and thermal stability.

[0032] Option 2: Preparation of PVA / PEO electrospun fiber layer PVA and PEO were dissolved in distilled water at 95℃ to prepare a 16 wt% PVA / PEO aqueous solution. The weight ratio of PVA / PEO was 90 / 10 to 50 / 50. The PVA / PEO mixed solution was injected into a 5 mL syringe, a No. 21 needle was attached, and then fixed to a push pump. The distance between the needle and the receiving substrate was adjusted to 20 cm, the voltage was 14 kV, the push pump speed was 12 mL / h, and the spinning time was 6 h. Electrospinning was used to obtain an electrospun nanofiber membrane: PVA / PEO fiber membrane. Option 3: Preparation of Semiconductor Electrospun Fiber Layer A: Preparation of TiO2 semiconductor electrospun fiber layer: 15 ml of dimethylformamide, 13 ml of ethanol, 0.5 g of urea, and 1.2 g of acetic acid were mixed thoroughly to form a mixed solvent. Then, 1.5 g of PVP was added and mixed. After the mixture became clear and transparent, 3 g of tetrabutyl titanate was added and mixed thoroughly for 2 hours. The mixture was injected into a 5 mL syringe, fitted with a No. 21 needle, and then fixed to a feed pump. The distance between the needle and the receiving substrate was adjusted to 15 cm, the voltage to 15 kV, the feed pump speed to 12 mL / h, and the spinning time to 6 h. After electrospinning, multilayer white fibers were obtained, which were calcined at 550 °C with a temperature rise of 5 °C / min for 2 h to obtain TiO2 semiconductor fibers.

[0033] B: Preparation of zinc oxide semiconductor electrospun fiber layer: Solutions of PVP (molecular weight = 1.3 million) and zinc diacetate (Zn(CH3COO)2·H2O) were prepared in dimethylformamide (DMF) using zinc acetate and PVP at different concentrations. All reagents were purchased from Sigma-Aldrich. The above mixture was injected into a 5 mL syringe, fitted with a No. 21 needle, and then fixed to a feed pump. The distance between the needle and the receiving substrate was adjusted to 15 cm, the voltage to 15 kV, the feed pump speed to 12 mL / h, and the spinning time to 6 h. After electrospinning, the composite fibers were annealed in an oxygen atmosphere (O2 flow rate: 2.5 L / min) in a carbonization furnace at different temperatures from 350 to 650 °C for 1 h to obtain ZnO nanofiber layers.

[0034] Option 4: Preparation of Polymer Semiconductor Composite Electrospun Fiber Layer Polyvinylidene fluoride (PVDF) / polyacrylonitrile (PAN) powders were dispersed in DMF at a mass ratio of 3:1 and a concentration of 8%. The mixture was magnetically stirred at 85°C for 2 h, followed by the addition of 3% zinc acetate (Zn(Ac)₂) powder and ultrasonication for 1 h to obtain a homogeneous mixture. After cooling the solution to room temperature, PVDF / PAN / Zn(Ac)₂ composite nanofibers were prepared by electrospinning using a substrate with a metal reflective layer as the receiving substrate, under an applied voltage of 20 kV, a receiving distance of 15 cm, and a spinning speed of 1 mL / h. The obtained substrate / reflective layer / PVDF / PAN / Zn(Ac)2 nanofiber device was first heat-treated at 140°C for 14 h, and then placed in a growth solution containing 0.1 mmol zinc chloride (ZnCl2), 0.1 mmol hexamethylenetriamine (HMTA), 3 mmol ammonia, and 20 mL water in a 50 mL autoclave for hydrothermal reaction at 100°C for 6 hours. Finally, the nanofibers were repeatedly washed and dried with deionized water to obtain ZnO@PVDF / PAN semiconductor composite nanofibers.

[0035] Step 2: Conformal Imprinting of Nanogratings: Option 1: Silver Nanograting (1) Take 0.12g of silver nano cubes, dilute with water to 50mL, sonicate for 20min, then add 0.0018g of cetyltrimethylammonium bromide, stir magnetically for 4h to obtain silver nanoparticle solution; (2) Weigh 0.245 g of 1H, 1H, 2H, 2H-perfluorodecyl mercaptan, add 50 mL of hexane and anhydrous ethanol solvent according to the volume ratio of hexane to anhydrous ethanol = 1:2, sonicate for 15 min, then add the silver nanoparticle solution from step (1), let stand for 15 s to form a silver film. (3) Using DVD discs (Kodak) ® Using the microstructured polycarbonate layer peeled off from the DVD-R as a template, the PDMS film matrix (Dow Corning Sylgard 184A adhesive) and curing agent (Dow Corning Sylgard 184B adhesive) were mixed at a mass ratio of 10:1 and cast onto the polycarbonate layer template on the surface of the optical disc. After vacuum drying, a PDMS soft template with a micro-nano grating structure was obtained. (4) Use tweezers to hold the dry and clean micro-nano grating structure PDMS soft template, gently touch the assembled silver film (2), and transfer the silver film onto the PDMS soft template; then conformally bond the PDMS soft template carrying the silver film to the surface of the PVP-PAN fiber film, and place them together on a small hot press machine. The hot pressing temperature is 180℃, the pressure is 2N, and the pressing time is 10s; after cooling, gently peel the PDMS soft template off the PVP-PAN fiber film. The silver on the PVP-PAN fiber film has the grating structure of the PDMS soft template, and the structural color can be observed at a suitable angle.

[0036] Option 2: Gold nanograting (1) Take a 1 mg / mL solution of gold nanospheres; (2) Weigh 0.245 g of 1H, 1H, 2H, 2H-perfluorodecylthiol, add 50 mL of hexane and anhydrous ethanol solvent according to the volume ratio of hexane to anhydrous ethanol = 1:2, sonicate for 15 min, then add the gold nanosphere solution from step (1), let stand for 15 s to form a gold particle film. (3) Using DVD discs (Kodak) ® Using the microstructured polycarbonate layer peeled off from the DVD-R as a template, the PDMS film matrix (Dow Corning Sylgard 184A adhesive) and curing agent (Dow Corning Sylgard 184B adhesive) were mixed at a mass ratio of 10:1 and cast onto the polycarbonate layer template on the surface of the optical disc. After vacuum drying, a PDMS soft template with a micro-nano grating structure was obtained. (4) Use tweezers to hold the dry and clean micro-nano grating structure PDMS soft template, gently touch the gold particle film assembled in (2), and transfer the gold film onto the PDMS soft template; then conformally bond the PDMS soft template carrying the gold film to the surface of the PVP-PAN fiber film, and place them together on a small hot press machine. The hot pressing temperature is 160℃, the pressure is 1N, and the pressing time is 5s; after cooling, gently peel the PDMS soft template off the PVP-PAN fiber film. The gold left on the PVP-PAN fiber film has the grating structure of the PDMS soft template, and the structural color can be observed at a suitable angle.

[0037] Option 3: Rare Earth Nanoparticle Grating (1) Take a 1 mg / mL solution of NaYF4∙2%Tm upconversion rare earth nanoparticles; (2) Prepare n-hexane: anhydrous ethanol volume ratio = 1:2, volume 50mL, add 1mmol sodium dodecyl sulfate (SDS), add the upconversion rare earth nanoparticle solution from step (1), let stand for 15s to form an upconversion nanoparticle film; (3) Using DVD discs (Kodak) ®Using the microstructured polycarbonate layer peeled off from the DVD-R as a template, the PDMS film matrix (Dow Corning Sylgard 184A adhesive) and curing agent (Dow Corning Sylgard 184B adhesive) were mixed at a mass ratio of 10:1 and cast onto the polycarbonate layer template on the surface of the optical disc. After vacuum drying, a PDMS soft template with a micro-nano grating structure was obtained. (4) Use tweezers to hold the dry and clean micro-nano grating structure PDMS soft template and gently touch the (2) assembled upconversion nanoparticle film to transfer the rare earth particle film onto the PDMS soft template; then conformally bond the PDMS soft template carrying the rare earth particle film to the surface of the PVP-PAN fiber film and place them together on a small hot press machine. The hot pressing temperature is 160℃, the pressure is 1N, and the pressing time is 5s; after cooling, gently peel the PDMS soft template off the PVP-PAN fiber film. The rare earth particle film left on the PVP-PAN fiber film has the grating structure of the PDMS soft template, and the structural color can be observed at a suitable angle.

[0038] Option 4: Semiconductor Nanoparticle Grating (1) Take a 1 mg / mL ZnO nanoparticle solution; the ZnO nanoparticle size is 50 nm.

[0039] (2) Prepare n-hexane: anhydrous ethanol volume ratio = 1:2, volume 50mL, add 1mmol sodium dodecyl sulfate (SDS), then add the ZnO nanoparticle solution from step (1), let stand for 15s to form a ZnO nanoparticle film; (3) Using DVD discs (Kodak) ® Using the microstructured polycarbonate layer peeled off from the DVD-R as a template, the PDMS film matrix (Dow Corning Sylgard 184A adhesive) and curing agent (Dow Corning Sylgard 184B adhesive) were mixed at a mass ratio of 10:1 and cast onto the polycarbonate layer template on the surface of the optical disc. After vacuum drying, a PDMS soft template with a micro-nano grating structure was obtained. (4) Use tweezers to hold the dry and clean micro-nano grating structure PDMS soft template and gently touch the assembled ZnO nanoparticle film (2) to transfer the ZnO particle film onto the PDMS soft template; then conformally bond the PDMS soft template carrying the ZnO particle film to the surface of the PVP-PAN fiber film and place them together on a small hot press machine. The hot pressing temperature is 160℃, the pressure is 1N, and the pressing time is 5s; after cooling, gently peel the PDMS soft template off the PVP-PAN fiber film. The ZnO particle film left on the PVP-PAN fiber film has the grating structure of the PDMS soft template, and the structural color can be observed at a suitable angle.

[0040] Step 3: Dye layer adsorption: Option 1: Rhodamine B was dissolved in a 1 wt%, 5 mL solution of polymethyl methacrylate (PMMA, 1000 kDa) in toluene, and then stirred vigorously at 40 °C for 5 h to obtain a mixed solution of PMMA and Rhodamine B. The concentration of Rhodamine B in the PMMA solution was 1 mM. The mixed solution was spin-coated onto the surface of the device obtained in step 2 at 3000 rpm for 50 s.

[0041] Option 2: Upconversion rare earth β-NaYF4: 18%Yb: 2%Er nanoparticles were dissolved in an aqueous solution of polyvinyl alcohol (PVA) (1wt%, 5 mL), and then stirred vigorously at 40℃ for 5 h to obtain a mixed solution of PVA and upconversion rare earth nanoparticles. The concentration of upconversion rare earth nanoparticles in the PVA solution was approximately 1 mM. The mixed solution was spin-coated onto the surface of the device obtained in step 2 at 3000 rpm for 50 s.

[0042] Option 3: Core-shell quantum dots (QDs) were dissolved in a toluene solution (5 wt%, 5 mL) of polystyrene (PS), and then stirred vigorously at 40 °C for 5 h to obtain a mixed solution of PS and quantum dots for electrospinning. The concentration of quantum dots in the PVA solution was between 1 mM. The mixed solution was spin-coated onto the surface of the device obtained in step 2 at 3000 rpm for 50 s.

[0043] Option 4: Citric acid-urea-based carbon dots (synthesized as described in the reference (Zhi, B., et al., Multicolor polymericcarbon dots: synthesis, separation and polyamide-supported molecular fluorescence. Chemical Science, 2021. 12(7): p. 2441-2455.), with adjustable red, green and blue luminescence colors) were dissolved in an aqueous solution of polyvinylpyrrolidone (PVP) (5wt%, 5 mL), and then stirred vigorously at 40 °C for 5 h to obtain a mixed solution of PVP and carbon dots for electrospinning. The concentration of carbon dots in the PVP solution was 10 mg / mL. The mixed solution was spin-coated onto the surface of the device obtained in step 2 at 3000 rpm for 50 s.

[0044] Option 5: The red-light conjugated polymer MEH-PPV (purchased from Xi'an Baolai Optoelectronics Technology Co., Ltd., MW=1000kDa) was dissolved in a toluene solution of polystyrene (PS) (5wt%, 5 mL), and then stirred vigorously at 40°C for 5 h to obtain a mixed solution of PS and MEH-PPV for electrospinning. The concentration of MEH-PPV in the PVP solution was between 0.01 and 1 mM. The mixed solution was spin-coated onto the surface of the device obtained in step 2 at 3000 rpm for 50 s.

[0045] Step 4: Packaging: The above-mentioned devices are encapsulated with silicone sealant, polydimethylsiloxane, or epoxy resin to obtain weather-resistant and wear-resistant PUF devices, i.e., electrospun paper chips. A schematic diagram of the final device structure is shown below. Figure 1 As shown; actual product image as shown Figure 2 As shown; Scanning electron microscope image before packaging is shown. Figure 3 As shown; Step 5: Imaging Option 1: The PUF device prepared in step 4 was read using a bright-field and dark-field optical microscope. The imaging parameters were as follows: light source: LED white light, halogen lamp, or xenon lamp; camera: CCD or CMOS; objective lens: 20–100x; eyepiece: 10x; image resolution: 512×512 or 1080×2160; exposure time: automatic. Bright-field optical microscope images are shown below. Figure 4 As shown.

[0046] Option 2: Fluorescence images of fibers were acquired using a (confocal) fluorescence microscope. The imaging parameters were as follows: the light source was a mercury lamp or a 405nm laser; a CCD or CMOS camera was used; the objective lens was 20-100x; the eyepiece was 10x; the image resolution was 512x512 or 1080x2160; and the exposure time was automatic.

[0047] Step 6: Feature extraction and key generation: Generate a 128-bit key from the image using the mean hash method, such as Figure 5 As shown. Image hashing involves segmentation, normalization, and enhancement preprocessing of the fluorescence intensity image. The fluorescence intensity image is used to generate a fingerprint through mean hashing. Specifically, the fluorescence intensity image is converted into binary data using the `graythresh` and `im2bw` functions in MATLAB, which becomes the initial key data. The initial key data is then processed using von Neumann architecture to remove redundant data, ultimately yielding the binary key. The robustness and uniqueness of the generated key are measured using the Hamming distance distribution. Figure 6 The Hamming distance distribution shows that the intra-slice Hamming distance is approximately 0.19, and the inter-slice Hamming distance is approximately 0.50.

[0048] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Therefore, all equivalent changes or modifications made to the structure, features and principles described in the claims of the present invention should be included within the scope of the present invention.

Claims

1. A chaotic metasurface chip based on imprinted nanogratings on the surface of electrospun fibers, characterized in that, It includes, from bottom to top, a substrate layer, a reflective layer, an electrospun fiber layer, a nanograting layer, a dye layer, and a protective layer; The substrate layer is made of a transparent optical material with a roughness Ra≤0.2μm; The reflective layer is made of metal and has a reflectivity of over 80%. The electrospun fiber layer is prepared by electrospun polymer and / or semiconductor fiber through an electrospun process. The nanograting layer is prepared by soft imprinting of plasmonic metals or luminescent nanoparticles. The dye layer is made of luminescent or light-absorbing material; The protective layer is encapsulated on top of the dye layer using transparent encapsulating adhesive.

2. The chaotic metasurface chip according to claim 1, characterized in that, The polymer used in the electrospun fiber layer is selected from one or more of polyvinyl alcohol, polyvinylpyrrolidone, polymethyl methacrylate, polystyrene, polyethylene oxide, polyacrylonitrile, cellulose ester, nylon-6, polyvinyl chloride, or polylactic acid.

3. The chaotic metasurface chip according to claim 1, characterized in that, The semiconductor fibers used in the electrospun fiber layer are selected from one or more of titanium oxide, indium oxide, tin oxide, cobalt oxide, zinc oxide, or barium titanate.

4. The chaotic metasurface chip according to claim 1, characterized in that, The plasmonic metal used in the nanograting layer is gold or silver; the luminescent nanoparticles are rare earth nanoparticles.

5. The chaotic metasurface chip according to claim 1, characterized in that, The luminescent nanoparticles are semiconductor nanoparticles.

6. The chaotic metasurface chip according to claim 1, characterized in that, The dye layer is prepared using organic dyes, quantum dots, or upconversion rare earth β-NaYF4:18%Yb:2%Er nanoparticles.

7. The chaotic metasurface chip according to claim 1, characterized in that, The protective layer is formed by encapsulating the dye layer with polydimethylsiloxane, epoxy resin, or polycarbonate.

8. The method for fabricating the chaotic metasurface chip according to claim 1, characterized in that, Includes the following steps: (1) Preparation of reflective layer: A reflective layer is formed by uniformly depositing a metal layer on a substrate using vacuum evaporation, magnetron sputtering, electroplating, or chemical deposition methods. (2) Preparation of electrospun fiber layer: Electrospun fiber layers are prepared by electrospun polymers and / or semiconductor nanofibers using an electrospun process. (3) Conformal transfer nanograting metasurface on fiber paper surface: The nanoparticle film assembly-conformal transfer technology is used to first assemble plasmonic metal nanoparticles or luminescent nanoparticles into a thin film through the interface, and then the nanoparticle film is conformally transferred from the water surface to the surface of the electrospun nanofiber layer described in (2) through the micro-nano structure PDMS stamp to form a nano grating layer. (4) Preparation of dye layer: A dye layer was prepared on the surface of a nanograting layer by electrostatic adsorption. (5) Protective layer encapsulation: A protective layer is encapsulated on top of the dye layer described in (4) by homogenization.

9. The method according to claim 8, characterized in that, Step (2) is as follows: The polymer is dissolved in a solvent and then stirred vigorously at 40°C for 5 h to obtain an electrospinning solution. The final polymer concentration is between 0.1 and 3 wt%. Then, using the substrate / reflective layer obtained in step (1) as the receiving substrate, an electrospinning technique is used to obtain a substrate / reflective layer / electrospinning fiber layer device. Alternatively, using the substrate / reflective layer obtained in step (1) as the receiving substrate, polymer and semiconductor fibers are prepared into a composite nanofiber membrane by electrospinning technology, and the prepared composite nanofiber membrane is heat-treated to obtain a substrate / reflective layer / electrospinned fiber layer device. Alternatively, using the substrate / reflective layer obtained in step (1) above as the receiving substrate, semiconductor nanofibers can be prepared into a substrate / reflective layer / electrospun fiber layer device by electrospinning technology.

10. The method according to claim 9, characterized in that, When preparing composite nanofiber membranes, the concentration of semiconductor fibers is 10wt% to 35wt%.

11. A method for generating keys using a chaotic metasurface chip according to any one of claims 1 to 7, characterized in that, Includes the following: (1) Feature extraction: Microscopic optical images of the electrospun paper security chip were obtained using dark-field optical microscopy, laser confocal fluorescence microscopy, and laser confocal Raman microscopy. The images were then segmented, standardized, and enhanced. (2) Key generation: Keys are generated using perceptual hashing or machine learning.

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