Electromagnetic metamaterials and methods of making the same

Abstract

This invention discloses an electromagnetic metamaterial and its preparation method. The electromagnetic metamaterial comprises a flexible matrix composed of a magnetic composite material and multiple periodically arranged metamaterial periodic units embedded therein; the magnetic composite material is a composite material of a magnetic material and an adhesive; the geometric thickness of the electromagnetic metamaterial is [missing information]. t 1, the aforementioned t The value of 1 ranges from 0.5 to 2 mm; the metamaterial periodic unit is a circular or square sheet, the diameter of the circular sheet or the side length of the square sheet is less than or equal to 5 cm; the metamaterial periodic unit is composed of a flexible conductive material. The electromagnetic metamaterial of this invention possesses excellent characteristics such as low magnetic material filling ratio, thin thickness, and strong wave absorption efficiency, achieving a simultaneous reduction in the thickness and density of traditional magnetic composite materials. Furthermore, the electromagnetic metamaterial of this invention also exhibits good flexibility and large-scale continuous bending and stretching characteristics, showing promising application prospects in both military and civilian fields.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electromagnetic wave absorption, in particular to a flexible electromagnetic metamaterial and a preparation method thereof. TECHNICAL BACKGROUND

[0002] With the progress of electronic information and communication technology, various electronic and communication equipment has penetrated into all aspects of people's daily life. On the one hand, it has brought great convenience to people's life, on the other hand, the electromagnetic pollution generated by electronic equipment has affected people's health, and the electromagnetic waves generated by too many electronic equipment are also easy to interfere with each other, affecting normal use. In addition, with the development of anti-stealth technology, stealth technology has also been greatly promoted. Therefore, electromagnetic wave absorbing materials have very broad applications in both military and civilian. Traditional wave-absorbing materials mainly require strong absorption performance, but with the development of the times, more requirements are put forward for wave-absorbing materials. New wave-absorbing materials require thin, light, wide and strong characteristics to meet more complex application environments.

[0003] Among the existing types of wave-absorbing materials, magnetic materials are the earliest and most perfect type, but due to the single use of wave-absorbing mechanism, the existing magnetic materials need a high filling ratio and a large thickness to achieve strong absorption. This leads to the fact that in actual use, magnetic materials are usually thick and heavy, which greatly limits the application of electromagnetic wave absorbing materials.

[0004] Metamaterials are a class of materials that realize special physical properties through the construction of precise geometric structures and size. The electromagnetic properties of metamaterials can be represented by equivalent permeability and equivalent permittivity through the equivalent medium theory.

[0005] Traditional wave-absorbing materials, especially wave-absorbing patch materials with silica gel as the base and high-performance absorbent, realize the absorption of electromagnetic waves through high magnetic permeability and magnetic loss. However, the increase of magnetic permeability and magnetic loss is accompanied by the increase of the filling ratio of magnetic materials, and the improvement of performance sacrifices the weight of wave-absorbing materials, and the thickness is mostly thick. Taking the widely used spherical carbonyl iron as an example, to realize-20dB and stronger wave-absorbing performance in the X wave band, the mass filling ratio needs to reach more than 70%, and the thickness is about 2mm.

[0006] In summary, combining the advantages of traditional wave-absorbing materials and metamaterials, developing new electromagnetic metamaterials with thin layers and low density has important significance for radar stealth and anti-electromagnetic interference of civilian electronic equipment. SUMMARY

[0007] The application aims to provide a flexible electromagnetic metamaterial and a preparation method thereof.

[0008] The application solves the above technical problems by the technical scheme provided by the application.

[0009] A flexible electromagnetic metamaterial comprises a flexible base made of a magnetic composite material and a plurality of periodically arranged metamaterial periodic units embedded therein. t 1, wherein the value of the flexible electromagnetic metamaterial is 0.5-2 mm. t 1, wherein the value of the flexible electromagnetic metamaterial is 0.5-2 mm. The shape of the metamaterial periodic unit is a circular sheet or a square sheet, and the diameter of the circular sheet or the side length of the square sheet is less than or equal to 5 cm.

[0010] The flexible electromagnetic metamaterial prepared by the application realizes the contradiction between reducing the density and thickness of the material and ensuring strong wave absorption effect by the special electromagnetic resonance wave absorption mechanism of the metamaterial and the excellent magnetic loss performance of the magnetic material.

[0011] In the magnetic composite material, the mass fraction of the magnetic material accounts for 10%-90%, and the balance is the adhesive.

[0012] The flexible base is made by bonding a first flexible base and a second flexible base, the metamaterial periodic unit is embedded on the upper surface of the first flexible base, and the vertical distance from the lower surface of the metamaterial periodic unit to the lower surface of the first flexible base is h , and the range is 0.1-1.9 mm.

[0013] The bonding is achieved by universal glue.

[0014] Since the soft magnetic material has excellent high-frequency loss characteristics, the magnetic material is preferably a soft magnetic material.

[0015] The soft magnetic material includes but is not limited to ferrite, carbonyl iron, nickel-zinc ferrite or rare earth soft magnetic material.

[0016] The adhesive includes but is not limited to paraffin, liquid silicone, polyurethane or nitrile rubber, and preferably a high-molecular material with flexible bending resistance, such as liquid silicone.

[0017] The geometric thickness of the magnetic composite material is defined as t 1, wherein the value of the flexible electromagnetic metamaterial is 0.5-2 mm. tThe value of 1 ranges from 0.5 to 2 mm.

[0018] The metamaterial periodic unit is in the shape of a circular or square sheet.

[0019] The radius of the circular piece is R The R The value range is 0.1-2mm.

[0020] The thickness of the circular sheet is t 2, the aforementioned t The value of 2 ranges from 0.05 to 0.3 mm.

[0021] The side length of the square piece is L The L The value range is 0.1-2mm.

[0022] The thickness of the square piece is t 3, the aforementioned t The value of 3 ranges from 0.05 to 0.3 mm.

[0023] The center-to-center distance between any two nearest neighbor metamaterial periodic elements is d The d The value range is 0.5-5mm.

[0024] The flexible conductive material is preferably a metal with good conductivity, including but not limited to copper, silver, gold, or liquid metal.

[0025] The flexible conductive material is preferably, and more preferably, a liquid metal with good flexibility, including but not limited to EGaIn alloy.

[0026] Furthermore, in order to obtain the optimal structural parameters, for magnetic composite materials with different ratios and different periodic unit materials, the geometric structural parameters corresponding to the required or set performance indicators are first obtained through CST simulation calculations.

[0027] The present invention also provides a method for preparing the flexible electromagnetic metamaterial, comprising the following steps:

[0028] (1) Using the line scan model in CST simulation software, the return loss of flexible electromagnetic metamaterials with different structural sizes is calculated based on the type and mass ratio of magnetic materials and adhesives in the magnetic composite material and the type of flexible conductive materials, and the structural size with the largest return loss is obtained.

[0029] The structural dimensions are the geometric thickness of the flexible electromagnetic metamaterial, the shape and thickness of the metamaterial periodic unit, the center distance between any two nearest neighbor metamaterial periodic units, and the vertical distance from the lower surface of the metamaterial periodic unit to the lower surface of the first flexible substrate.

[0030] (2) The structure size with the maximum return loss is calculated based on CST simulation software, a first flexible matrix is obtained by casting, and a vacancy with the same shape and thickness as the metamaterial periodic unit is reserved on the upper surface of the first flexible matrix;

[0031] (3) A flexible conductive material is placed in the vacancy on the upper surface of the first flexible matrix;

[0032] (4) A second flexible matrix is used to cover and bond to the first flexible matrix with the periodic unit of the metamaterial by using universal glue, and a flexible electromagnetic metamaterial is obtained.

[0033] The beneficial effects of the present application mainly include:

[0034] 1. By embedding the periodic unit of the metamaterial in the magnetic composite material, the magnetic material can also achieve strong absorption at 2-18 GHz with a low filling ratio and low thickness, and the wave absorption rate is greater than 90%.

[0035] 2. By adjusting the geometric size of the periodic unit of the metamaterial ( R , t 2 , L , t 3 ), and the spatial position of the periodic unit of the metamaterial in the magnetic composite material ( h and d ), the position and intensity of the absorption peak can be controlled.

[0036] 3. Using liquid metal as the material of the periodic unit of the metamaterial, the flexible electromagnetic metamaterial has very excellent flexibility and bendability, and can still restore the original structure after large-scale deformation without affecting the wave absorption performance.

[0037] 4. The present application has the characteristics of simple structure, light weight, small thickness and deformation resistance, and can be attached to the surface of the application object, and has certain application potential in military and civilian fields. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 The wave absorption effect schematic diagram of the electromagnetic metamaterial prepared in Example 1.

[0039] Figure 2 The wave absorption effect schematic diagram of the electromagnetic metamaterial prepared in Example 2.

[0040] Figure 3 The wave absorption effect schematic diagram of the electromagnetic metamaterial prepared in Example 3.

[0041] Figure 4 The wave absorption effect schematic diagram of the electromagnetic metamaterial prepared in Example 4.

[0042] Figure 5 Schematic diagram of wave absorption effect of electromagnetic metamaterial prepared for example 5.

[0043] Figure 6 Schematic diagram of wave absorption effect of electromagnetic metamaterial prepared for example 6.

[0044] Figure 7 Schematic diagram of structure of electromagnetic metamaterial. DETAILED DESCRIPTION

[0045] The above description of the embodiments of the present application enables a person skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

[0046] Example 1:

[0047] (1) By using a line scanning model in CST simulation software, the filling mass ratio of the magnetic material in the magnetic composite material is set to 25%, in which nickel-zinc ferrite is selected as the magnetic material, polyurethane is set as the adhesive, and copper is set as the periodic unit material. The return loss of the flexible electromagnetic metamaterial with different structure sizes is calculated to obtain the structure size with the maximum return loss.

[0048] The optimal parameter of the structure size is the geometric thickness of the magnetic composite material t 1=0.9 mm, the shape of the metamaterial periodic unit is circular, R =1.4 mm, the thickness t 2=0.1 mm, the center distance between any two nearest neighbor metamaterial periodic units d =2.0 mm, the vertical distance from the center of the metamaterial periodic unit to the surface of the first flexible matrix h =0.7 mm.

[0049] (2) Based on the structure size with the maximum return loss calculated by the CST simulation software, the magnetic material and the adhesive are mechanically stirred and mixed uniformly to obtain the first flexible matrix by casting. The first flexible matrix has a vacancy with the same shape and depth as the metamaterial periodic unit.

[0050] (3) The flexible conductive material is placed in the vacancy.

[0051] (4) covering the first flexible substrate with the second flexible substrate and bonding to the first flexible substrate embedding the periodic unit by using the universal adhesive to obtain the flexible electromagnetic super thin material 1.

[0052] The magneto-electric parameters of the flexible electromagnetic super thin material 1 are tested by a vector network analyzer, and the wave absorption performance is shown in Figure 1 The total thickness of the electromagnetic super thin material is 0.9 mm, the filling ratio is lower than that of the traditional magnetic composite material, and the electromagnetic wave absorption intensity is obviously enhanced compared with the comparative example 1 and the comparative example 2.

[0053] Example 2:

[0054] (1) By using the line scanning model in the CST simulation software, the filling mass ratio of the magnetic material in the magnetic composite material is set to 30%, the spherical carbonyl iron is selected as the magnetic material, the liquid silicone is set as the adhesive, and the metal silver is set as the periodic unit material, the return loss of the flexible electromagnetic super thin material with different structure sizes is calculated, and the structure size with the maximum return loss is obtained.

[0055] The optimal parameters of the structure size are the geometric thickness of the magnetic composite material t 1=0.9 mm, the periodic unit shape is a square, L =1.6 mm, the thickness t 3=0.1 mm, the center distance between any two nearest neighbor super thin material periodic units d =2.0 mm, the vertical distance from the center of the super thin material periodic unit to the magnetic composite material h =0.6 mm.

[0056] (2) Based on the structure size with the maximum return loss calculated by the CST simulation software, the magnetic material and the adhesive are mechanically stirred and mixed uniformly, the first flexible substrate is obtained by casting, and the first flexible substrate surface is reserved with a vacancy with the same shape and depth as the super thin material periodic unit.

[0057] (3) The flexible conductive material is placed in the vacancy.

[0058] (4) covering the first flexible substrate with the second flexible substrate and bonding to the first flexible substrate embedding the periodic unit by using the universal adhesive to obtain the flexible electromagnetic super thin material 2.

[0059] The magneto-electric parameters of the flexible electromagnetic super thin material 2 are tested by a vector network analyzer, and the wave absorption performance is shown in Figure 2 The total thickness of the electromagnetic super thin material is 0.9 mm, the filling ratio is lower than that of the traditional magnetic composite material, and the electromagnetic wave absorption intensity is obviously enhanced compared with the comparative example 1 and the comparative example 2.

[0060] Example 3

[0061] (1) By CST simulation software using line-scan model, set the filling mass ratio of magnetic material in the magnetic composite material to be 30%, in which spherical carbonyl iron is selected as the magnetic material, set polyurethane as the adhesive, and liquid metal (EGaIn) as the periodic unit material, calculate the return loss of flexible electromagnetic metamaterials with different structure sizes, and obtain the structure size with the maximum return loss.

[0062] The optimal parameters of the structure size are the geometric thickness of the magnetic composite material t 1=0.9 mm, the periodic unit shape is a square, L =1.6 mm, the thickness t 3=0.1 mm, the center distance between any two nearest neighbor metamaterial periodic units d =2.0 mm, the vertical distance from the center of the metamaterial periodic unit to the first flexible matrix surface h =0.7 mm.

[0063] (2) Based on the structure size with the maximum return loss calculated by the CST simulation software, the magnetic material and the adhesive are mechanically stirred and mixed uniformly, and the first flexible matrix is obtained by casting. The first flexible matrix has a vacancy with the same shape and depth as the metamaterial periodic unit on the surface.

[0064] (3) The flexible conductive material is placed in the vacancy.

[0065] (4) The second flexible matrix is used to cover and adhere to the first flexible matrix with the embedded periodic unit by using universal adhesive to obtain a flexible ultrathin flexible electromagnetic metamaterial 3.

[0066] The magneto-electric parameters of the flexible electromagnetic metamaterial 3 are tested by a vector network analyzer, and the wave absorption performance is as shown in Figure 3 . The total thickness of the electromagnetic metamaterial is 0.9 mm, and the filling ratio is lower than that of the traditional magnetic composite material, and it has a strong absorption peak near 16 GHz. The wave absorption performance is much better than that of the traditional magnetic composite material of Comparative Example 1 and the pure metamaterial of Comparative Example 4. Due to the flexibility of polyurethane and liquid metal, the wave absorption material of the present embodiment has better flexibility and bending resistance compared to Example 1 and Example 2.

[0067] Example 4

[0068] (1) CST simulation software is used to calculate the return loss of the flexible electromagnetic metamaterial with different structure sizes by setting the filling mass ratio of the magnetic material in the magnetic composite material to 25%, selecting spherical carbonyl iron as the magnetic material, setting liquid silicone as the adhesive, and setting liquid metal (EGaIn) as the periodic unit material.

[0069] The optimal parameters of the structure size are the geometric thickness of the magnetic composite material t 1=0.9mm, the periodic unit shape is a circular sheet, R =1.8mm, the thickness t 2=0.1mm, the center distance between any two nearest neighbor metamaterial periodic units d =2.0mm, the vertical distance from the center of the metamaterial periodic unit to the first flexible matrix h =0.7mm.

[0070] (2) Based on the structure size with the maximum return loss calculated by the CST simulation software, the magnetic material and the adhesive are mechanically stirred and mixed uniformly to obtain the first flexible matrix by casting. The first flexible matrix has a vacancy with the same shape and depth as the metamaterial periodic unit on the surface.

[0071] (3) The flexible conductive material is placed in the vacancy.

[0072] (4) The second flexible matrix is used to cover and bond to the first flexible matrix with the embedded periodic unit by using universal adhesive to obtain the flexible ultrathin flexible electromagnetic metamaterial 3.

[0073] The magneto-electric parameters of the flexible electromagnetic metamaterial 3 are tested by a vector network analyzer, and the wave absorption performance is as shown in Figure 4 The total thickness of the electromagnetic metamaterial is 0.9 mm, the filling ratio is lower than that of the traditional magnetic composite material, and there is a strong absorption peak near 13 GHz. The wave absorption performance is much better than that of the traditional magnetic composite material of Comparative Example 1 and the pure metamaterial of Comparative Example 5. In addition, due to the flexibility of the liquid silicone and the liquid metal, the wave absorption material of the present embodiment has better flexibility and bending resistance than Examples 1 and 2.

[0074] Example 5:

[0075] (1) CST simulation software is used to calculate the return loss of the flexible electromagnetic metamaterial with different structure sizes by setting the filling mass ratio of the magnetic material in the magnetic composite material to 25%, selecting spherical carbonyl iron as the magnetic material, setting liquid silicone as the adhesive, and setting liquid metal (EGaIn) as the periodic unit material.

[0076] the optimal parameter of the structure size is the geometric thickness of the magnetic composite material t 1=0.9mm, the periodic unit shape is a circular sheet, R =1.8mm, the thickness t 2=0.1mm, the center distance between any two nearest neighbor metamaterial periodic units d =2.0mm, the vertical distance from the center of the metamaterial periodic unit to the lower surface of the first flexible matrix h =0.7mm.

[0077] (2) The structure size with the maximum return loss is calculated based on the CST simulation software, the magnetic material and the adhesive are uniformly mixed by mechanical stirring, the first flexible matrix is obtained by casting, and the first flexible matrix has a vacancy with the same shape and depth as the metamaterial periodic unit.

[0078] (3) The flexible conductive material is placed in the vacancy.

[0079] (4) The second flexible matrix is used to cover and bond to the first flexible matrix with the embedded periodic unit by using the universal adhesive to obtain the flexible electromagnetic metamaterial 5.

[0080] The magneto-electric parameters of the flexible electromagnetic metamaterial 5 are tested by a vector network analyzer, and the wave absorption performance is as shown in Figure 5 The total thickness of the electromagnetic metamaterial is 0.9 mm, the filling ratio is lower than that of the traditional magnetic composite material, and there is a strong absorption peak near 14 GHz. The wave absorption performance is much better than that of the traditional magnetic composite material of Comparative Example 1 and the pure metamaterial of Comparative Example 6. In addition, due to the flexibility of the liquid silicone and the liquid metal, the wave absorption material of the present embodiment has better flexibility and bending resistance than Examples 1 and 2.

[0081] Example 6:

[0082] (1) The line sweep model in the CST simulation software is used to set the filling mass ratio of the magnetic material in the magnetic composite material to be 60%, the rare earth soft magnetic yttrium cobalt iron is selected as the magnetic material, the liquid silicone is selected as the adhesive, the liquid metal (EGaIn) is selected as the periodic unit material, the return loss of the flexible electromagnetic metamaterial with different structure sizes is calculated, and the structure size with the maximum return loss is obtained.

[0083] the optimal parameter of the structure size is the geometric thickness of the magnetic composite material t 1=0.9mm, the periodic unit shape is a circular sheet, R =1.8mm, the thickness t 2=0.1mm, the center distance between any two nearest neighbor metamaterial periodic unitsd = 2.0 mm, vertical distance from the lower surface of the metamaterial periodic unit to the lower surface of the first flexible matrix of the magnetic composite material h = 0.7 mm.

[0084] (2) The structure size with the maximum return loss calculated based on the CST simulation software is mixed evenly with the magnetic material and the adhesive by mechanical stirring, and the first flexible matrix is obtained by casting. The first flexible matrix has a vacancy with the same shape and depth as the metamaterial periodic unit on the surface;

[0085] (3) The flexible conductive material is placed in the vacancy.

[0086] (4) The second flexible matrix is used to cover and bond to the first flexible matrix with the embedded periodic unit by using the universal adhesive to obtain the flexible ultrathin flexible electromagnetic metamaterial 6.

[0087] The magneto-electric parameters of the flexible electromagnetic metamaterial 6 are tested by a vector network analyzer, and the wave absorption performance is as shown in Figure 6 The total thickness of the electromagnetic metamaterial is 0.9 mm, and the filling ratio is lower than that of the traditional magnetic composite material. It has a strong absorption peak near 10 GHz. The wave absorption performance is much better than that of the traditional magnetic composite material of Comparative Example 1 and the pure metamaterial of Comparative Example 7. In addition, due to the flexibility of liquid silicone and liquid metal, the wave absorbing material of the present embodiment has better flexibility and bending resistance than Examples 1 and 2.

[0088] Comparative Example 1:

[0089] In this comparative example, a magnetic material composite material without embedding a metamaterial periodic unit is selected as a comparison. In the composite material, spherical carbonyl iron is selected as the magnetic material, and the filling mass ratio is 30%, and silicone is selected as the adhesive. An electromagnetic wave absorbing sheet with a thickness of 0.9 mm is obtained by casting. The magneto-electric parameters are measured by a vector network analyzer, and the wave absorption performance in the range of 2 GHz to 18 GHz is calculated.

[0090] Comparative Examples 2-7:

[0091] In this comparative example, a pure metamaterial periodic unit is selected as a comparison. In the metamaterial periodic unit, the metal material and geometric structure parameters of the metamaterial periodic unit of Comparative Examples 2-7 are consistent with the materials used in Examples 1-6, respectively. The magneto-electric parameters are measured by a vector network analyzer, and the return loss in the range of 2 GHz to 18 GHz is calculated.

Claims

1. Electromagnetic metamaterial, comprising a flexible substrate composed of a magnetic composite material and a plurality of periodically arranged metamaterial periodic units embedded therein, the magnetic composite material being a composite material of a soft magnetic magnetic material and a binder, wherein the mass fraction of the magnetic material is 25% to 30%; the geometric thickness of the electromagnetic metamaterial is 0.9 mm; the shape of the metamaterial periodic unit is a circular sheet, the metamaterial periodic unit is composed of a flexible conductive material, the radius of the circular sheet is 1.8 mm, the thickness of the metamaterial periodic unit is 0.05 to 0.3 mm, the center distance between any two nearest neighbor metamaterial periodic units is 2 mm, the embedded metamaterial periodic unit is on the first flexible substrate upper surface of the flexible substrate, and the vertical distance h between the lower surface of the metamaterial periodic unit and the lower surface of the first flexible substrate is 0.7 mm. t 1 R 2 d 2 d ​ 2. The electromagnetic metamaterial of claim 1, wherein, The flexible matrix of the magnetic composite material further comprises a second flexible matrix.

3. The electromagnetic metamaterial of claim 2, wherein, The second flexible matrix is bonded to the first flexible matrix.

4. The electromagnetic metamaterial of claim 3, wherein, The bonding is achieved by universal glue.

5. The electromagnetic metamaterial of any preceding claim, wherein, The magnetic material is a metallic magnetic material or a ferrite.

6. The electromagnetic metamaterial of claim 5, wherein, The metallic magnetic material is carbonyl iron or a rare earth soft magnetic material, and the ferrite is a nickel-zinc ferrite.

7. The electromagnetic metamaterial of claim 1, wherein, The adhesive is paraffin, liquid silicone, polyurethane or nitrile rubber.

8. The electromagnetic metamaterial of claim 7, wherein, The adhesive is a high polymer material with flexible bending resistance.

9. The electromagnetic metamaterial of claim 1, wherein, The flexible conductive material is a metal with good conductivity.

10. The electromagnetic metamaterial of claim 9, wherein, The metal is copper, silver, gold or liquid metal.

11. The electromagnetic metamaterial of claim 9, wherein, The metal is an EGaIn alloy.

12. A method for preparing the electromagnetic metamaterial of any preceding claim, comprising the following steps: (1) calculating the return loss of electromagnetic metamaterials with different structural sizes according to the types of magnetic material and adhesive in the magnetic composite material, the mass fraction of the magnetic material and the type of flexible conductive material by CST simulation software, to obtain the structural size with the maximum return loss; the structural size is the geometric thickness of the electromagnetic metamaterial, the shape and thickness of the metamaterial periodic unit, the center distance between any two nearest neighbor metamaterial periodic units, and the vertical distance from the lower surface of the metamaterial periodic unit to the lower surface of the first flexible matrix; (2) based on the structural size with the maximum return loss calculated by the CST simulation software, casting the first flexible matrix, and the upper surface of the first flexible matrix is reserved with a vacancy with the same shape and depth as the metamaterial periodic unit; (3) placing the flexible conductive material in the vacancy on the upper surface of the first flexible matrix; (4) covering the first flexible matrix with the second flexible matrix and bonding it to the first flexible matrix by universal glue to obtain the electromagnetic metamaterial.

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