A flexible terahertz metasurface tag, detection system and preparation method

Abstract

The application discloses a flexible terahertz super surface label, a detection system and a preparation method, the super surface label is a transmission type structure, comprising a dielectric layer and a metal pattern layer closely attached to the upper surface of the dielectric layer; the dielectric layer is made of a flexible transparent material; the metal pattern layer comprises at least one resonant ring, when there are multiple resonant rings, the multiple resonant rings are arranged in a nested mode, each resonant ring corresponds to a bit code, and the frequency domain coding information is formed by increasing or deleting the number of resonant rings; the resonant ring is a central symmetric structure; when an incident terahertz wave signal inquires the super surface label, the frequency domain coding information determined by the super surface label is excited, so that the frequency spectrum structure of the terahertz wave signal is changed. The application specifically realizes a terahertz super surface label made of a flexible material in a terahertz frequency band, and realizes a security label by using a flexible super surface device, and the maximum advantage is that the flexible super surface device can be conformal and can be covered on the surface of an irregular object, and the security is high.

Description

Technical Field

[0001] This invention relates to the field of label anti-counterfeiting technology, specifically to a flexible terahertz metasurface label, detection system, and preparation method. Background Technology

[0002] Anti-counterfeiting labeling refers to applying specific anti-counterfeiting technologies to product labels to ensure the authenticity and safety of products. The application of anti-counterfeiting labeling helps people identify the authenticity of products and trace their origin, thereby protecting and promoting product quality and safeguarding consumer rights.

[0003] Currently, the main types of labels used in anti-counterfeiting identification include QR codes, barcodes, and RFID tags. QR codes and barcodes are easily worn or contaminated, affecting readability. RFID technology can also be used for anti-counterfeiting, although RFID tags generally have good durability, they cannot be used in certain applications, such as when RF power must be limited (e.g., for containers containing explosives, strong co-location interference, or covert interrogation) or when imaging is required. Furthermore, the substrates used in RFID tags are mostly rigid materials with excellent flatness and stable performance, but their excessive rigidity lacks the excellent mechanical properties of flexible materials, such as the ability to withstand various mechanical deformations like tension, bending, folding, and torsion. Therefore, they are only suitable for objects with flat surfaces and simple, regular geometric shapes. However, in practical anti-counterfeiting applications, the target object to be marked is often complex and irregular in shape, including some shape-variable forms. This requires the label material to have mechanical flexibility, capable of changing according to the specific application.

[0004] Therefore, existing anti-counterfeiting labels (QR codes, barcodes, RFID tags, etc.) are not suitable for marking target objects with complex and irregular shapes. In particular, some shapes are variable, and they cannot conform to the shape of the object, cannot cover the surface of irregular objects, and have low label security. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that existing anti-counterfeiting labels (QR codes, barcodes, radio frequency tags, etc.) are not suitable for marking target objects with complex and irregular shapes. In particular, some shapes are variable and cannot conform to the object, cannot cover the surface of irregular objects, and have low security.

[0006] The purpose of this invention is to provide a flexible terahertz metasurface tag, detection system, and fabrication method. Specifically, it realizes a terahertz metasurface tag made of flexible materials in the terahertz frequency band. Utilizing flexible metasurface devices to realize security tags offers the greatest advantage of conformal design, allowing it to cover the surface of irregular objects. It can be used in product marking, security and anti-counterfeiting, and other fields, offering high security. This invention can be embedded under non-transparent surfaces like RFID tags, and can also be read and identified from non-transparent surfaces like visible light imaging. Therefore, it easily achieves high capacity and high security for tags, and has broad application prospects in product identification and security.

[0007] This invention is achieved through the following technical solution:

[0008] In a first aspect, the present invention provides a flexible terahertz metasurface tag, which is a transmissive structure comprising a dielectric layer and a metal pattern layer closely attached to the upper surface of the dielectric layer.

[0009] The dielectric layer is made of a flexible transparent material; the metal pattern layer includes at least one resonant ring, and when there are multiple resonant rings, the multiple resonant rings are arranged in a nested manner, and each resonant ring corresponds to a bit code. By increasing or decreasing the number of resonant rings, frequency domain coded information is formed; the resonant ring has a centrally symmetric structure.

[0010] When the incident terahertz wave signal interrogates the metasurface tag, the frequency domain coding information determined by the metasurface tag is excited, thereby changing the spectral structure of the terahertz wave signal.

[0011] Furthermore, the dielectric layer is made of polyimide with a dielectric constant of 3.5.

[0012] Furthermore, the dielectric layer is cube-shaped, with a thickness h of 47–53 μm and dimensions of 200 μm * 200 μm to 300 μm * 300 μm.

[0013] Furthermore, the material of the metal patterned layer is copper (Cu), silver (Ag), or gold (Au), with a thickness of t = 200 nm.

[0014] Furthermore, the metal pattern layer includes four equilateral octagonal resonant rings, that is, the shape adopts four nested equilateral octagonal ring resonant rings, namely: the innermost resonant ring, the second innermost resonant ring, the second outermost resonant ring, and the outermost resonant ring, and the four equilateral octagonal resonant rings are arranged in a nested manner.

[0015] Furthermore, the innermost resonant ring has a side length of 30–35 μm, a width of 3–8 μm, and a thickness of 200 nm–300 nm;

[0016] The secondary internal resonant ring has a side length of 40–45 μm, a width of 3–8 μm, and a thickness of 200 nm–300 nm.

[0017] The side length of the secondary external resonant ring is 50–55 μm, the width is 3–8 μm, and the thickness is 200 nm–300 nm.

[0018] The outermost resonant ring has a side length of 60–65 μm, a width of 3–8 μm, and a thickness of 200 nm–300 nm.

[0019] Furthermore, the distance between adjacent equilateral octagonal resonant rings is 8–10 μm.

[0020] Furthermore, when the incident terahertz wave signal interrogates the metasurface tag, the frequency domain coding information determined by the metasurface tag is excited, thereby changing the spectral structure of the terahertz wave signal, specifically:

[0021] When the incident terahertz wave signal interrogates the metasurface tag, the terahertz wave signal couples through four resonant rings to generate four relatively uniform resonant points in the range of 0 to 0.6 THz. The frequency positions of each resonant point (i.e., the frequency positions where the maximum transmission coefficient of each frequency band is located) are 0.251 THz, 0.339 THz, 0.414 THz and 0.571 THz, respectively, and the frequency position is encoded as 1111.

[0022] When a resonant ring is removed, the corresponding offset point disappears, and other adjacent frequency points will show a slight shift, which does not affect the reading of the coded data, showing good frequency selectivity.

[0023] For example, when the innermost and outermost resonant rings are removed respectively, the corresponding minimum and maximum frequencies will also disappear, and other adjacent frequencies will show slight shifts, which will not affect the reading of the coded data, showing good frequency selectivity.

[0024] Furthermore, when the incident terahertz wave is TE-polarized or TM-polarized, the metasurface tag exhibits the same spectral characteristics and is insensitive to polarization.

[0025] Secondly, the present invention provides a detection system for a flexible terahertz metasurface tag, the detection system comprising the aforementioned flexible terahertz metasurface tag, a terahertz transmitter, and a terahertz receiver; the flexible terahertz metasurface tag is attached to a target object;

[0026] The terahertz transmitter is used to transmit terahertz wave signals to the metasurface tag on the target object;

[0027] The metasurface tag is used to receive the terahertz wave signal, change the spectral structure of the terahertz wave signal, and output spectral information.

[0028] The terahertz receiver is used to receive spectrum information for subsequent analysis.

[0029] Thirdly, the present invention also provides a method for preparing a flexible terahertz metasurface tag, comprising:

[0030] Step 1: Fabricate a surface pattern on a photomask; the surface pattern includes at least one resonant ring, and when there are multiple resonant rings, the multiple resonant rings are arranged in a nested manner, and the resonant rings have a centrally symmetrical structure;

[0031] Step 2: Place the photomask in an ultrasonic cleaner containing acetone to clean it and remove surface impurities; then immerse the photomask in anhydrous ethanol and clean it with deionized water; finally, use a nitrogen gun to dry the photomask.

[0032] Step 3: Clean and dry the polyimide film using acetone and alcohol;

[0033] Step 4: Select a polyimide film as the dielectric layer, and use a magnetron sputtering machine to deposit copper and titanium on both sides of the cleaned and surface-dried polyimide film to obtain the top metal film and bottom metal film of the metasurface.

[0034] Step 5: According to the surface pattern on the photomask, use a photolithography machine to perform exposure photolithography on the top metal film of the metasurface, and use a developing solution to develop the exposed top metal film of the metasurface.

[0035] Step 6: According to the developed pattern, the top metal film of the metasurface is etched using an ion beam etching machine to obtain a metal pattern layer; the metal pattern layer and the dielectric layer constitute a flexible terahertz metasurface label.

[0036] Furthermore, it also includes:

[0037] Before step 5, the process also includes: placing the sample on a spin coater for spin coating and pre-baking the spin-coated sample.

[0038] Step 6 is followed by: immersing the etched flexible terahertz metasurface label in an acetone solution, removing the photolithography machine from the surface of the flexible terahertz metasurface label using a plasma resist remover, and finally cleaning the flexible terahertz metasurface label with deionized water and air drying it.

[0039] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0040] 1. This invention discloses a flexible terahertz metasurface tag, detection system, and preparation method. Specifically, it realizes a terahertz metasurface tag made of flexible material in the terahertz frequency band. The security tag is realized by using flexible metasurface devices. Its greatest advantage is that it can be conformal and can cover the surface of irregular objects. It can be used in product marking, security anti-counterfeiting and other fields, and has high security.

[0041] 2. The present invention provides a flexible terahertz metasurface tag, detection system and preparation method, which can be directly embedded or printed on the marked object in a manner similar to optical barcodes, rather than in a tag attached to the object. The identification information comes directly from the object itself, rather than from the tag placed on the object, thus the tag has high security.

[0042] 3. The present invention provides a flexible terahertz metasurface tag, a detection system and a preparation method. Due to the rotational symmetry of its structure, the flexible terahertz metasurface tag can produce the same effect on both TE and TM polarized waves, proving the polarization insensitivity of the nested structure.

[0043] 4. The present invention provides a flexible terahertz metasurface tag, a detection system, and a preparation method. The flexible terahertz metasurface tag stores coded information in a resonant unit and transmits the coded information using electromagnetic waves. By controlling the presence or absence of resonance, the frequency point is controlled. The frequency point with a resonance peak is recorded as 1, and the frequency point without a resonance peak is recorded as 0. By controlling the presence or absence of resonance, multiple encoding states can be achieved, resulting in higher data density. Attached Figure Description

[0044] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0045] Figure 1 This is a schematic diagram of a flexible terahertz metasurface label;

[0046] Figure 2 A front view of a flexible terahertz metasurface label.

[0047] Figure 3 A side view of a flexible terahertz metasurface label;

[0048] Figure 4 This is a schematic diagram of the spectral encoding of a flexible terahertz metasurface tag.

[0049] Figure reference numerals and corresponding component names:

[0050] 1-Dielectric layer, 2-Metal pattern layer. Detailed Implementation

[0051] In the following, the terms “comprising” or “may include” as used in various embodiments of the invention indicate the presence of an inventive function, operation, or element, and do not limit the addition of one or more functions, operations, or elements. Furthermore, as used in various embodiments of the invention, the terms “comprising,” “having,” and their cognates are intended only to indicate a specific feature, number, step, operation, element, component, or combination of the foregoing, and should not be construed as primarily excluding the presence of one or more other features, numbers, steps, operations, elements, components, or combinations of the foregoing, or adding one or more combinations of the foregoing.

[0052] In various embodiments of the invention, the expression "or" or "at least one of A and / or B" includes any combination or all combinations of the words listed simultaneously. For example, the expression "A or B" or "at least one of A and / or B" may include A, may include B, or may include both A and B.

[0053] The expressions used in the various embodiments of the present invention (such as "first," "second," etc.) may modify various constituent elements in the various embodiments, but do not limit the corresponding constituent elements. For example, the above expressions do not limit the order and / or importance of the elements. The above expressions are only used for the purpose of distinguishing one element from other elements. For example, a first user device and a second user device refer to different user devices, although both are user devices. For example, a first element may be referred to as a second element without departing from the scope of the various embodiments of the present invention, and similarly, a second element may also be referred to as a first element.

[0054] It should be noted that if a description is made of "connecting" one component to another, then the first component can be directly connected to the second component, and a third component can be "connected" between the first and second components. Conversely, when a component is "directly connected" to another component, it can be understood that there is no third component between the first and second components.

[0055] The terminology used in the various embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to limit the various embodiments of the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which the various embodiments of the invention pertain. The terms (such as those defined in a generally used dictionary) are to be interpreted as having the same meaning as in the context of the relevant technical field and are not to be interpreted as having an idealized or overly formal meaning, unless clearly defined in the various embodiments of the invention.

[0056] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0057] Existing anti-counterfeiting labels (QR codes, barcodes, RFID tags, etc.) are not suitable for marking target objects with complex and irregular shapes. In particular, some shapes are variable, and they cannot conform to the shape of the object, cannot cover the surface of irregular objects, and have low label security.

[0058] Therefore, tag materials need to possess mechanical flexibility, capable of adapting to specific applications. With the development of terahertz science and technology, terahertz spectroscopy and imaging technology are becoming increasingly understood. Terahertz waves possess advantages such as penetrating most non-polar materials, facilitating rapid and non-destructive testing, spectral fingerprinting, and rich information content. Terahertz-based tags can be embedded under non-transparent surfaces like RFID tags, or read and identified from non-transparent surfaces using visible light imaging. This facilitates high-capacity and high-security tag implementation, offering broad application prospects in product identification and security.

[0059] Based on the above, this invention designs a flexible terahertz metasurface tag, specifically a terahertz metasurface tag made of flexible material in the terahertz frequency band, utilizing flexible metasurface devices to realize a security tag. Compared with commonly used tag anti-counterfeiting and security detection technologies, the security tag function realized by this invention using flexible metasurface devices has the greatest advantage in that it is conformal and can cover the surface of irregular objects. This is because most objects requiring electromagnetic shielding or electromagnetic interference often have irregular surfaces, thus increasing angular incident stability and reducing the scattering cross-section. This invention can be used in product marking, security anti-counterfeiting, and other fields, offering high security.

[0060] Example 1

[0061] like Figure 1 As shown, this invention discloses a flexible terahertz metasurface tag, specifically a terahertz metasurface tag made of flexible material in the terahertz frequency band, utilizing flexible metasurface devices to realize a security tag. The metasurface tag has a transmissive structure, including a dielectric layer 1 and a metal pattern layer 2 tightly attached to the upper surface of the dielectric layer 1;

[0062] The dielectric layer 1 is made of a flexible transparent material; the metal pattern layer 2 includes at least one resonant ring. When there are multiple resonant rings, they are arranged in a nested manner. Each resonant ring corresponds to a bit code. By increasing or decreasing the number of resonant rings, frequency domain coded information is formed. The resonant ring has a centrally symmetrical structure.

[0063] When the incident terahertz wave signal interrogates the metasurface tag, the frequency domain coding information determined by the metasurface tag is excited, thereby changing the spectral structure of the terahertz wave signal.

[0064] In this embodiment, the metal pattern layer 2 includes four equilateral octagonal resonant rings, that is, the shape is formed by nesting four equilateral octagonal ring-shaped resonant rings, namely: the innermost resonant ring, the second innermost resonant ring, the second outermost resonant ring, and the outermost resonant ring, and the four equilateral octagonal resonant rings are arranged in a nested manner. Specifically, the top surface metal pattern layer is a nested octagonal ring-shaped metal strip, and the metal pattern layer is closely attached to the flexible dielectric layer 1.

[0065] In this embodiment, the dielectric layer 1 is made of polyimide with a dielectric constant of 3.5. The dielectric layer 1 is cubic in shape, with a thickness h = 50 μm and dimensions P = 200 μm * 200 μm.

[0066] In this embodiment, the metal pattern layer 2 is made of copper (Cu), has a thickness of 0.2 μm, and has an electrical conductivity of 5.96 × 10⁻⁶. 7 S / m.

[0067] In this embodiment, as Figure 2 and Figure 3 As shown, the specific dimensions of the metasurface tag are as follows: P = 220 μm, d = 50 μm, the side length of the innermost resonant ring W1 = 60 μm, the side length of the second inner resonant ring W2 = 50 μm, the side length of the second outer resonant ring W3 = 40 μm, the side length of the outermost resonant ring W4 = 30 μm, the distance between the four adjacent equilateral octagonal resonant rings l1 = 8 μm, the width of the resonant ring l2 = 4 μm, and the thickness of the resonant ring t = 0.3.

[0068] In practical implementation, the metasurface tag exhibits the same spectral characteristics and is insensitive to polarization when the incident terahertz wave is TE-polarized or TM-polarized. When a TE-polarized or TM-polarized terahertz wave is incident perpendicularly onto the metasurface tag along the -z-axis, the tag's transmission coefficient is S. 21 =E t / E i E t It is the energy amplitude of the transmitted electromagnetic wave, E i This is the energy amplitude of the incident electromagnetic wave. The structure was simulated using the commercial simulation software CST MICROWAVE STUDIO 2022.

[0069] like Figure 4As shown, this invention designs a flexible terahertz metasurface tag. The designed 4-bit tag is made of 0 to 4 resonant rings arranged together, with each resonant ring corresponding to a bit encoding. By increasing or decreasing the number of resonant rings, frequency domain encoding information is formed. When an incident terahertz wave signal interrogates the metasurface tag, the frequency domain encoding information determined by the metasurface tag is excited, thereby changing the spectral structure of the terahertz wave signal. A transmission spectrum exists in the range of 0–0.6 THz, coupling to generate four relatively uniform resonant points. The frequency positions of each resonant point are 0.251 THz, 0.339 THz, 0.414 THz, and 0.571 THz, respectively, and are encoded as 1111. When the innermost resonant ring is removed, the resonant peak of the outermost frequency point disappears, so it is encoded as 1110. When the outermost resonant ring is removed again, the resonant peak of the innermost frequency point disappears, so it is encoded as 0111. After further removal of the resonant rings, the frequencies generated by adjacent resonants will have a small shift, which does not affect the reading of the encoded data. Figure 4 As shown.

[0070] Due to its rotationally symmetric structure, the tag of this invention exhibits the same spectral characteristics for TM incident polarized waves as for TE incident polarized waves. Therefore, the reading of tag data is independent of the polarization direction of the incident wave, resulting in better stability.

[0071] This invention has the following advantages:

[0072] 1. This invention provides a flexible terahertz metasurface tag, specifically a terahertz metasurface tag made of flexible material in the terahertz frequency band. It utilizes flexible metasurface devices to realize security tags, and its greatest advantage is that it can conform to the surface of irregular objects. It can be used in product marking, security and anti-counterfeiting fields, and has high security.

[0073] 2. The present invention provides a flexible terahertz metasurface label that can be directly embedded or printed on the marked object in a manner similar to optical barcodes, rather than being attached to a label on the object. The identification information comes directly from the object itself, rather than from the label placed on the object, thus the label has high security.

[0074] 3. The present invention provides a flexible terahertz metasurface tag, which, due to the rotational symmetry of its structure, can produce the same effect on both TE and TM polarized waves, proving the polarization insensitivity of the nested structure.

[0075] 4. The present invention provides a flexible terahertz metasurface tag that stores encoded information in a resonant unit and transmits the encoded information using electromagnetic waves. By controlling the presence or absence of resonance, the frequency point is controlled. The frequency point with a resonance peak is recorded as 1, and the frequency point without a resonance peak is recorded as 0. By controlling the presence or absence of resonance, multiple encoding states can be achieved, resulting in higher data density.

[0076] Example 2

[0077] The difference between this embodiment and Embodiment 1 is that this embodiment provides a detection system for a flexible terahertz metasurface tag. The detection system includes a flexible terahertz metasurface tag, a terahertz transmitter, and a terahertz receiver as described in Embodiment 1; the flexible terahertz metasurface tag is attached to the target object.

[0078] The terahertz transmitter is used to transmit terahertz wave signals to the metasurface tag on the target object;

[0079] The metasurface tag is used to receive the terahertz wave signal, change the spectral structure of the terahertz wave signal, and output spectral information.

[0080] The terahertz receiver is used to receive spectrum information for subsequent analysis.

[0081] Example 3

[0082] The difference between this embodiment and Embodiment 1 is that this embodiment provides a method for fabricating a flexible terahertz metasurface tag, which uses standard semiconductor micro / nano fabrication technology to fabricate a flexible terahertz metasurface tag, including:

[0083] Step 1: Fabricate a surface pattern on a photomask; the surface pattern includes at least one resonant ring, and when there are multiple resonant rings, the multiple resonant rings are arranged in a nested manner, and the resonant rings are centrally symmetrical structures; in this embodiment, a nested octagonal ring structure is adopted. The nested ring structure generates four resonant points due to the coupling of the incident terahertz wave signal, so the flexible terahertz metasurface label adopts a nested frequency selective label.

[0084] Step 2: Place the photomask in an ultrasonic cleaner containing acetone to clean it and remove surface impurities; then immerse the photomask in anhydrous ethanol and clean it with deionized water; finally, use a nitrogen gun to dry the photomask.

[0085] Step 3: Clean and dry the polyimide film with acetone and alcohol; the purpose is to ensure the uniformity of copper plating and the adhesion between the substrate and the metal.

[0086] Step 4: Select a polyimide film as the dielectric layer, and use a magnetron sputtering machine (FHR) to deposit a 200 nm thick copper film and a 10 nm thick titanium film on both sides of the cleaned and dried polyimide film to obtain a top metal film and a bottom metal film of the metasurface; titanium is added to increase the adhesion between the metal and the polyimide film.

[0087] Step 5: According to the surface pattern on the photomask, use a photolithography machine to perform exposure photolithography on the top metal film of the metasurface, and use a developing solution to develop the exposed top metal film of the metasurface.

[0088] Step 6: According to the developed pattern, the top metal film of the metasurface is etched using an ion beam etching machine to obtain a metal pattern layer; the metal pattern layer and the dielectric layer constitute a flexible terahertz metasurface label.

[0089] As a further implementation, it also includes:

[0090] Before step 5, the process also includes: placing the sample (i.e., the polyimide film after step 4) on a spin coater for spin coating, and pre-baking the spin-coated sample.

[0091] Step 6 is followed by: immersing the etched flexible terahertz metasurface label in an acetone solution, removing the photolithography machine from the surface of the flexible terahertz metasurface label using a plasma resist remover, and finally cleaning the flexible terahertz metasurface label with deionized water and air drying it.

[0092] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A flexible terahertz metasurface tag, characterized in that, The metasurface label has a transmissive structure, including a dielectric layer (1) and a metal pattern layer (2) that is closely attached to the upper surface of the dielectric layer (1). The dielectric layer (1) is made of a flexible transparent material; the metal pattern layer (2) includes at least one resonant ring. When there are multiple resonant rings, they are arranged in a nested manner. Each resonant ring corresponds to a bit code. By increasing or decreasing the number of resonant rings, frequency domain coding information is formed; the resonant ring has a centrally symmetrical structure. When the incident terahertz wave signal interrogates the metasurface tag, the frequency domain coding information determined by the metasurface tag is excited, thereby changing the spectral structure of the terahertz wave signal. The metal pattern layer (2) includes four equilateral octagonal resonant rings, namely: the innermost resonant ring, the second innermost resonant ring, the second outermost resonant ring and the outermost resonant ring, and the four equilateral octagonal resonant rings are arranged in a nested manner. The innermost resonant ring has a side length of 30~35μm, a width of 3~8μm, and a thickness of 200nm~300nm; The secondary internal resonant ring has a side length of 40~45μm, a width of 3~8μm, and a thickness of 200nm~300nm; The secondary external resonant ring has a side length of 50~55μm, a width of 3~8μm, and a thickness of 200nm~300nm; The outermost resonant ring has a side length of 60~65μm, a width of 3~8μm, and a thickness of 200nm~300nm; The distance between the four adjacent equilateral octagonal resonant rings is 8~10µm; When an incident terahertz wave signal interrogates the metasurface tag, the frequency domain coding information determined by the metasurface tag is excited, thereby changing the spectral structure of the terahertz wave signal, specifically: When the incident terahertz wave signal interrogates the metasurface tag, the terahertz wave signal couples through four resonant rings to generate four uniform resonant points between 0 and 0.6 THz. The frequency points of each resonant point are 0.251 THz, 0.339 THz, 0.414 THz and 0.571 THz, respectively, and the frequency point position is encoded as 1111. When a resonant ring is removed, the corresponding offset point will disappear, and other adjacent frequency points will shift, but this will not affect the reading of the coded data.

2. The flexible terahertz metasurface tag according to claim 1, characterized in that, The dielectric layer (1) is made of polyimide with a dielectric constant of 3.5; The material of the metal pattern layer (2) is copper, silver or gold.

3. The flexible terahertz metasurface tag according to claim 2, characterized in that, The dielectric layer (1) is cubic in shape, and its thickness is 47~53μm. The dimensions of the dielectric layer (1) are... .

4. The flexible terahertz metasurface tag according to claim 1, characterized in that, When the incident terahertz wave is TE-polarized or TM-polarized, the spectral characteristics of the metasurface tag are the same, and it is insensitive to polarization.

5. A detection system for a flexible terahertz metasurface tag, characterized in that, The detection system includes a flexible terahertz metasurface tag, a terahertz transmitter, and a terahertz receiver as described in any one of claims 1 to 4; the flexible terahertz metasurface tag is attached to the target object. The terahertz transmitter is used to transmit terahertz wave signals to the metasurface tag on the target object; The metasurface tag is used to receive the terahertz wave signal, change the spectral structure of the terahertz wave signal, and output spectral information. The terahertz receiver is used to receive spectrum information for subsequent analysis.

6. A method for preparing the label according to any one of claims 1 to 4, characterized in that, include: Step 1: Fabricate a surface pattern on a photomask; the surface pattern includes at least one resonant ring, and when there are multiple resonant rings, the multiple resonant rings are arranged in a nested manner, and the resonant rings have a centrally symmetrical structure; Step 2: Place the photomask in an ultrasonic cleaner containing acetone to clean it and remove surface impurities; then immerse the photomask in anhydrous ethanol and clean it with deionized water; finally, use a nitrogen gun to dry the photomask. Step 3: Clean and dry the polyimide film using acetone and alcohol; Step 4: Select a polyimide film as the dielectric layer, and use a magnetron sputtering machine to deposit copper and titanium on both sides of the cleaned and surface-dried polyimide film to obtain the top metal film and bottom metal film of the metasurface. Step 5: According to the surface pattern on the photomask, use a photolithography machine to perform exposure photolithography on the top metal film of the metasurface, and use a developing solution to develop the exposed top metal film of the metasurface. Step 6: According to the developed pattern, the top metal film of the metasurface is etched using an ion beam etching machine to obtain a metal pattern layer; the metal pattern layer and the dielectric layer constitute a flexible terahertz metasurface label.

7. The preparation method according to claim 6, characterized in that, Also includes: Before step 5, the process also includes: placing the sample on a spin coater for spin coating and pre-baking the spin-coated sample; Step 6 is followed by: immersing the etched flexible terahertz metasurface label in an acetone solution, removing the photolithography machine from the surface of the flexible terahertz metasurface label using a plasma resist remover, and finally cleaning the flexible terahertz metasurface label with deionized water and air drying it.

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