A light-transmitting flexible metamaterial absorber with low infrared emissivity

Abstract

The present invention discloses a light-transmitting flexible metamaterial absorber with low infrared emissivity, comprising a plurality of metamaterial absorber structural units distributed in a periodic array in a two-dimensional space; the metamaterial absorber structural unit comprises a low infrared emission plate and a microwave absorption plate; the microwave absorption plate comprises a transparent medium substrate layer, a transparent flat plate layer, a transparent medium substrate layer, and a transparent reflection layer from top to bottom; the four corners of the lower end face of the infrared emission plate are vertically fixedly connected to the four corners of the upper end face of the microwave absorption plate through four plastic columns in a one-to-one correspondence, so that the infrared emission plate and the microwave absorption plate are arranged in parallel and an air layer is left in the middle. The present invention uses optically transparent, lightweight and flexible polyvinyl chloride (PVC) and polyethylene terephthalate (PET) as substrates, making them very popular in practical engineering applications, and having practical applications of multifunctional stealth technology.

Description

Technical Field

[0001] The invention relates to the field of electromagnetic waves and novel artificial electromagnetic materials, and in particular to a light-transmitting flexible metamaterial absorber with low infrared emissivity. Background Art

[0002] With the rapid development of advanced detection technology through radar, laser, infrared (IR) and visible light, improving the stealth capability of military targets has become an important issue today. Radar and infrared detection are the two most commonly used methods, so there is an urgent need to develop radar and infrared stealth compatible technology. The key technology of radar stealth is to reduce the radar echo power or deflect the echo direction to reduce the radar cross section of the target. Infrared detectors locate, track, guide and attack by detecting the infrared radiation generated by the target. Therefore, the focus of infrared stealth is to reduce or change the infrared radiation characteristics of the target. According to Kirchhoff's law, infrared stealth materials require low absorptivity and high reflectivity. However, radar stealth materials require low reflection and high absorption. It is difficult to achieve high microwave absorption and low IR emission at the same time. Under special conditions, such as windows on airplanes or cars, stealth materials should be optically transparent. Therefore, the invention of an optically transparent, flexible, ultra-wideband microwave / infrared compatible absorber has become an urgent issue at present.

[0003] Recently, artificially structured metamaterials have been proposed to control the propagation or scattering properties of electromagnetic waves. The constitutive parameters of metamaterials can be carefully designed, which greatly broadens the range of material responses found in nature and produces exotic properties such as negative refraction, perfect lenses, and invisible cloaks. Due to their excellent performance in manipulating electromagnetic waves, metamaterials have attracted great attention in stealth technology. At present, many technologies have been proposed to achieve optically transparent metamaterial absorbers and ultra-wideband absorbers, but they cannot take into account both infrared and microwave absorption; metamaterial absorbers with high microwave absorptivity and low IR emissivity have also been proposed, but they cannot achieve optical transparency or ultra-wideband microwave absorption and have high infrared emissivity, which limits their application in some devices that require high transmittance. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a light-transmitting flexible metamaterial absorber with low infrared emissivity in response to the defects involved in the background technology, which solves the problem that the current absorbers cannot achieve ultra-wideband, low infrared emissivity, flexibility and optical transparency at the same time.

[0005] The present invention adopts the following technical solutions to solve the above technical problems:

[0006] A light-transmitting flexible metamaterial absorber with low infrared emissivity, comprising a plurality of metamaterial absorber structural units distributed in a periodic array in a two-dimensional space;

[0007] The metamaterial absorber structure unit comprises a low infrared emission plate and a microwave absorption plate;

[0008] The infrared emitting plate is square and is a polyvinyl chloride medium substrate with a first transparent conductive film etched on the upper surface, wherein the first transparent conductive film comprises a plurality of square block films distributed in a periodic array;

[0009] The microwave absorption plate comprises, from top to bottom, a transparent flat plate layer, a transparent medium substrate layer, and a transparent reflection layer;

[0010] The transparent flat layer, the transparent dielectric substrate layer, and the transparent reflective layer are all squares with the same shape as the infrared emitting plate, wherein the transparent flat layer is a polyethylene terephthalate dielectric substrate with a second transparent conductive film etched on the upper surface; the transparent dielectric substrate layer is a polyvinyl chloride dielectric substrate; the transparent reflective layer is a polyethylene terephthalate dielectric substrate with a third transparent conductive film on the upper surface, and the shape of the third transparent conductive film is the same as that of the polyethylene terephthalate dielectric substrate thereunder;

[0011] The second transparent conductive film comprises first to third ring films, the first to third rings have the same ring width, the first square ring is arranged in the second square ring, the second square ring is arranged in the third square ring, the spacing between the first square ring and the second square ring is equal to the spacing between the second square ring and the third ring, and the first to third rings are provided with openings at the midpoints of their four sides in a direction perpendicular to their side lengths;

[0012] The four corners of the lower end surface of the infrared emitting plate are vertically fixedly connected to the four corners of the upper end surface of the transparent flat plate layer of the microwave absorbing plate through four plastic columns, so that the infrared emitting plate and the microwave absorbing plate are arranged in parallel with an air layer in between.

[0013] As a further optimization solution of the low infrared emissivity metamaterial absorber of the present invention, the dielectric constant of the polyvinyl chloride dielectric substrate in the infrared emitting plate is 3, and the loss tangent is 0.06.

[0014] As a further optimization scheme of the low infrared emissivity metamaterial absorber of the present invention, the thickness of the low infrared emission plate is 0.125 mm, the thickness of the microwave absorption plate is 2 mm, and the thickness of the air layer between the low infrared emission plate and the microwave absorption plate is 1.8 mm.

[0015] As a further optimization scheme of the low infrared emissivity metamaterial absorber of the present invention, the dielectric constant of the polyvinyl chloride dielectric substrate in the transparent dielectric substrate layer is 3.07, the loss tangent is 0.014, and the thickness is 2 mm.

[0016] As a further optimization scheme of the low infrared emissivity metamaterial absorber of the present invention, the polyethylene terephthalate dielectric substrate in the transparent flat layer and the transparent reflective layer has a dielectric constant of 3, a loss tangent of 0.06, and a thickness of 0.125 mm.

[0017] As a further optimization scheme of the low infrared emissivity metamaterial absorber of the present invention, the first to third transparent conductive films are any one of indium tin oxide, fluorine-doped tin dioxide, aluminum-doped zinc oxide, and polymer-based transparent conductors.

[0018] As a further optimization scheme of a metamaterial absorber with low infrared emissivity of the present invention, the side length of the flat layer in the transparent microwave absorption plate is 13.5 mm, the opening width on the four sides of the third square ring is 0.1 mm, the opening width on the four sides of the second square ring is 0.1 mm, the opening width on the four sides of the first square ring is 0.1 mm, the outer side length of the third square ring is 13.5 mm, the outer side length of the second square ring is 9 mm, the outer side length of the first square ring is 4.5 mm, the ring widths of the first to third square rings are all 1.75 mm, and the interval between the first square ring and the second square ring is 0.5 mm.

[0019] As a further optimization scheme of the low infrared emissivity metamaterial absorber of the present invention, the thickness of the second transparent conductive film is 55nm, the thickness of the third transparent conductive film is 185nm, and the square resistance of the second and third transparent conductive films ranges from 6-300Ω / sq.

[0020] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects:

[0021] 1. The present invention rationally arranges the area ratio of low-resistance ITO in the infrared emission layer, achieving a low infrared emissivity of 0.36;

[0022] 2. The low infrared emissivity metamaterial absorber designed by the present invention has an absorption rate of more than 90% in the frequency band of 5.57 GHz to 18.87 GHz, and its relative bandwidth is 108.8%, achieving ultra-wideband microwave absorption;

[0023] 3. The low infrared emissivity metamaterial absorber designed by the present invention combines the properties of low infrared emissivity, high microwave absorptivity, ultra-wideband, optical transparency, etc., and has great application potential in military stealth. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic structural diagram of a metamaterial absorber structural unit in the present invention;

[0025] Figure 2 is a top view schematic diagram of the low infrared emission board in the present invention;

[0026] Figure 3 is a schematic top view of a microwave absorbing plate in the present invention;

[0027] Figure 4 is a side view schematic diagram of a metamaterial absorber structure unit in the present invention;

[0028] Figure 5 is a cross-sectional schematic diagram of a metamaterial absorber structural unit in the present invention;

[0029] Figure 6 is a schematic diagram of the S parameter curve of the present invention under vertical incident electromagnetic waves;

[0030] Figure 7 It is a schematic diagram of the wave absorption rate curve of the present invention under vertical incident electromagnetic waves.

[0031] In the figure, 1- low infrared emission plate, 2- microwave absorption plate, 3- air layer. DETAILED DESCRIPTION

[0032] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings:

[0033] The present invention can be implemented in many different forms and should not be considered to be limited to the embodiments described herein. On the contrary, these embodiments are provided to make this disclosure thorough and complete, and will fully express the scope of the present invention to those skilled in the art. In the accompanying drawings, components are enlarged for clarity.

[0034] It should be understood that although the terms first, second, third, etc. can be used here to describe various elements, components and / or parts, these elements, components and / or parts are not limited by these terms. These terms are only used to distinguish elements, components and / or parts from each other. Therefore, the first element, component and / or part discussed below can become the second element, component or part without departing from the teaching of the present invention.

[0035] Research shows that continuous metal is an ideal material for infrared stealth. This is because the emissivity of metal is relatively low, while the emissivity of dielectric is high. Therefore, for devices made by covering metal on dielectric, the larger the area ratio of metal, the lower its infrared emissivity. However, continuous metal sheets with a thickness greater than the skin depth will have strong reflection in the microwave frequency band. When the continuous metal plate is patterned with some gap arrays, electromagnetic waves can pass through it in the microwave frequency band. At this time, the microwave absorption layer located in the low infrared emissivity layer can achieve microwave absorption. The low-resistance ITO film is used for the metal-like equivalent of the low infrared emission layer and the microwave absorption layer backplane. The incident electromagnetic wave first passes through the low infrared emission layer. Since the high filling rate ITO film achieves low infrared emissivity, it passes through the air layer and the electromagnetic wave that arrives through the gap of the low infrared emission layer is incident on the microwave absorption layer. After the good impedance matching, ohmic loss and dielectric loss of the microwave absorption layer, ultra-wideband microwave absorption is achieved.

[0036] like Figure 1 As shown, the present invention discloses a light-transmitting flexible metamaterial absorber with low infrared emissivity, comprising a plurality of metamaterial absorber structural units distributed in a periodic array in a two-dimensional space;

[0037] The metamaterial absorber structure unit comprises a low infrared emission plate and a microwave absorption plate;

[0038] The infrared emitting plate is square and is a polyvinyl chloride medium substrate with a first transparent conductive film etched on the upper surface, wherein the first transparent conductive film comprises a plurality of square block films distributed in a periodic array;

[0039] The microwave absorption plate comprises, from top to bottom, a transparent flat plate layer, a transparent medium substrate layer, and a transparent reflection layer;

[0040] The transparent flat layer, the transparent metamaterial layer, and the transparent reflective layer are all squares with the same shape as the infrared emitting plate, wherein the transparent flat layer is a polyethylene terephthalate dielectric substrate (PET) with a second transparent conductive film etched on the upper surface; the transparent dielectric substrate layer is a polyvinyl chloride dielectric substrate (PVC); the transparent reflective layer is a polyethylene terephthalate dielectric substrate (PET) with a third transparent conductive film on the upper surface, and the shape of the third transparent conductive film is the same as that of the polyethylene terephthalate dielectric substrate thereunder;

[0041] The second transparent conductive film comprises first to third ring films, the first to third rings have the same ring width, the first square ring is arranged in the second square ring, the second square ring is arranged in the third square ring, the spacing between the first square ring and the second square ring is equal to the spacing between the second square ring and the third ring, and the first to third rings are provided with openings at the midpoints of their four sides in a direction perpendicular to their side lengths;

[0042] The four corners of the lower end surface of the infrared emitting plate are vertically fixedly connected to the four corners of the upper end surface of the transparent flat plate layer of the microwave absorbing plate through four plastic columns, so that the infrared emitting plate and the microwave absorbing plate are arranged in parallel with an air layer in between.

[0043] The first to third transparent conductive films are made of any one of indium tin oxide, fluorine-doped tin dioxide, aluminum-doped zinc oxide, and polymer-based transparent conductors, and preferably indium tin oxide (ITO) transparent conductive film.

[0044] The thickness of the second transparent conductive film is 55 nm, the thickness of the third transparent conductive film is 185 nm, and the square resistance of the second and third transparent conductive films ranges from 6 to 300 Ω / sq.

[0045] Figure 2 The top view of the unit structure of the low infrared emission plate of the low infrared emissivity metamaterial absorber. The first transparent conductive film is made of indium tin oxide transparent conductive film (ITO), and the structural dimensions are as follows: 1 =13.5mm, a=1.58mm, g=0.4mm, low infrared emissivity can be obtained by using a low-resistance conductive film material with a high filling rate in the structure. Specifically, the emissivity u can be calculated as u=u m f m +u d (1-f m ), where u is the emissivity of the structure, u m and u d are the emissivity of the low-resistance conductive film material and the dielectric substrate, respectively, m is the filling rate of low resistance conductive film material (area of ​​low resistance conductive film material / total area, where low resistance (R 1 =6Ω / sq) The emissivity of ITO is 0.1, the emissivity of the PVC dielectric substrate is 0.9, the thickness of the PVC dielectric substrate is 0.125mm, its dielectric constant is 3, the loss tangent is 0.06, and the calculated infrared emissivity is 0.36.

[0046] Figure 3 The unit structure of the microwave absorption plate of the low infrared emissivity metamaterial absorber is shown in the top view. Its dimensions are as follows: 2 =13.5mm, a 1 =2.2mm, a 2 =4.45mm, a 3 =6.7mm, b 1 =0.1mm, b 2 =0.1mm, b 3=0.1mm, w=0.5mm, v=1.75mm. That is, the side length of the transparent metamaterial layer is 15mm, the opening width on the four sides of the third square ring is 0.8mm, the opening width on the four sides of the second square ring is 0.6mm, the opening width on the four sides of the first square ring is 0.35mm, the outer side length of the third square ring is 13.5mm, the outer side length of the second square ring is 9mm, the outer side length of the first square ring is 4.5mm, the ring widths of the first to third square rings are all 1.75mm, and the interval between the first square ring and the second square ring is 0.5mm.

[0047] Figure 4 The side view of the unit structure of the low infrared emissivity metamaterial absorber, the thickness of the air layer is t k =1.8mm, the thickness of the microwave absorbing plate is t w =2.25mm.

[0048] Figure 5 The structure side view of the microwave absorption plate has the following structural dimensions: it includes the top patterned PET-ITO thin film resistor layer, the middle dielectric substrate layer and the bottom continuous PET-ITO thin film resistor layer. The middle dielectric substrate layer is PVC with a thickness of t pvc =2mm, its dielectric constant is 3.07, and its loss tangent is 0.014. The thickness of the PET substrate for etching ITO is t pet =0.125mm, patterned ITO film resistance R 2 =100Ω / sq, the resistance of the bottom continuous ITO film is R 3 =6Ω / sq, the thickness of the patterned ITO film is 55nm, and the thickness of the continuous ITO film is 185nm.

[0049] The dielectric constant of the polyvinyl chloride dielectric substrate in the transparent metamaterial layer is 3.07, the loss tangent is 0.014, and the thickness is 2 mm.

[0050] Figure 6 This is the S parameter curve of the low infrared emissivity metamaterial absorber. The corresponding S parameters were obtained using the frequency domain solver of the electromagnetic simulation software CST. The absorptivity is above 90% in the range of 5.57~18.87 GHz, and the absorption bandwidth is 108.8%.

[0051] Figure 7 This is a graph showing the absorption rate of a low infrared emissivity metamaterial absorber under vertically incident electromagnetic waves.

[0052] Will Figure 6 The obtained S parameters are then calculated using the formula A(ω)=1-R(ω)-T(ω)=1-|S 11 | 2 -|S 21 | 2The absorption rate curve was obtained, and the absorption rate was above 90% in the range of 5.57~18.87 GHz, and the absorption bandwidth was 108.8%.

[0053] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as herein.

[0054] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A light-transmitting flexible metamaterial absorber with low infrared emissivity, characterized in that: It comprises a plurality of metamaterial absorber structure units which are distributed in a periodic array in a two-dimensional space; The metamaterial absorber structure unit comprises a low infrared emission plate and a microwave absorption plate; The infrared emitting plate is square and is a polyvinyl chloride medium substrate with a first transparent conductive film etched on the upper surface, wherein the first transparent conductive film comprises a plurality of square block films distributed in a periodic array; The microwave absorption plate comprises, from top to bottom, a transparent flat plate layer, a transparent medium substrate layer, and a transparent reflection layer; The transparent flat layer, the transparent dielectric substrate layer, and the transparent reflective layer are all squares with the same shape as the infrared emitting plate, wherein the transparent flat layer is a polyethylene terephthalate dielectric substrate with a second transparent conductive film etched on the upper surface; the transparent dielectric substrate layer is a polyvinyl chloride dielectric substrate; the transparent reflective layer is a polyethylene terephthalate dielectric substrate with a third transparent conductive film on the upper surface, and the shape of the third transparent conductive film is the same as that of the polyethylene terephthalate dielectric substrate thereunder; The second transparent conductive film comprises first to third ring films, the first to third rings have the same ring width, the first square ring is arranged in the second square ring, the second square ring is arranged in the third square ring, the spacing between the first square ring and the second square ring is equal to the spacing between the second square ring and the third ring, and the first to third rings are provided with openings at the midpoints of their four sides in a direction perpendicular to their side lengths; The four corners of the lower end surface of the infrared emitting plate are vertically fixedly connected to the four corners of the upper end surface of the transparent flat plate layer of the microwave absorbing plate through four plastic columns, so that the infrared emitting plate and the microwave absorbing plate are arranged in parallel with an air layer in between.

2. The light-transmitting flexible metamaterial absorber with low infrared emissivity according to claim 1, characterized in that: The dielectric constant of the polyvinyl chloride dielectric substrate in the infrared emitting board is 3, and the loss tangent is 0.

06.

3. The light-transmitting flexible metamaterial absorber with low infrared emissivity according to claim 1, characterized in that: The thickness of the low infrared emission plate is 0.125 mm, the thickness of the microwave absorption plate is 2 mm, and the thickness of the air layer between the low infrared emission plate and the microwave absorption plate is 1.8 mm.

4. The light-transmitting flexible metamaterial absorber with low infrared emissivity according to claim 1, characterized in that: The dielectric constant of the polyvinyl chloride dielectric substrate in the transparent dielectric substrate layer is 3.07, the loss tangent is 0.014, and the thickness is 2 mm.

5. The light-transmitting flexible metamaterial absorber with low infrared emissivity according to claim 1, characterized in that: The dielectric constant of the polyethylene terephthalate medium substrate in the transparent flat layer and the transparent reflective layer is 3, the loss tangent is 0.06, and the thickness is 0.125 mm.

6. The light-transmitting flexible metamaterial absorber with low infrared emissivity according to claim 1, characterized in that: The first to third transparent conductive films are any one of indium tin oxide, fluorine-doped tin dioxide, aluminum-doped zinc oxide, and polymer-based transparent conductors.

7. The light-transmitting flexible metamaterial absorber with low infrared emissivity according to claim 1, characterized in that: The side length of the flat layer in the microwave absorption plate is 13.5 mm, the opening width on the four sides of the third square ring is 0.1 mm, the opening width on the four sides of the second square ring is 0.1 mm, the opening width on the four sides of the first square ring is 0.1 mm, the outer side length of the third square ring is 13.5 mm, the outer side length of the second square ring is 9 mm, the outer side length of the first square ring is 4.5 mm, the ring widths of the first to third square rings are all 1.75 mm, and the interval between the first square ring and the second square ring is 0.5 mm.

8. The light-transmitting flexible metamaterial absorber with low infrared emissivity according to claim 1, characterized in that: The thickness of the second transparent conductive film is 55 nm, the thickness of the third transparent conductive film is 185 nm, and the square resistance of the second and third transparent conductive films ranges from 6 to 300 Ω / sq.

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