A liquid-based electromagnetic metamaterial with tunable emissivity

Abstract

The application belongs to the technical field of metamaterials, and particularly relates to a liquid-based electromagnetic metamaterial with tunable emissivity, which comprises a plurality of periodically arrayed basic units, the basic unit comprises, from top to bottom, a dielectric layer, a dielectric slot layer, a substrate and a conductive film layer which are sequentially stacked and arranged, the dielectric slot layer is provided with a rice-shaped liquid cavity for storing liquid, the rice-shaped liquid cavity is formed by two cross-connected cross arms, the cross arm comprises two mutually perpendicular and equal-length straight arms, and the length ratio of the straight arms on different cross arms is 1-1.2:1. The application realizes flexible tuning of target emissivity under different backgrounds and reduces the visibility of the target in a microwave remote sensing system.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metamaterials, and particularly relates to a liquid-based electromagnetic metamaterial with tunable emissivity. BACKGROUND

[0002] With the diversification of target detection means and the continuous improvement of detection accuracy, the microwave radiometer has become increasingly prominent in the modern target detection system due to its advantages of passive detection, strong concealment, all-day and all-weather operation, etc. However, the progress of this target detection technology puts forward higher requirements for the concealment of ground high-value targets. Therefore, how to effectively improve the survivability of ground high-value targets and weaken the detectability of targets in passive remote sensing systems has become an important research topic.

[0003] Electromagnetic metamaterials are a kind of materials composed of artificially designed subwavelength periodic structures, which can realize the unique electromagnetic response characteristics that are difficult to achieve in natural materials. In recent years, the electromagnetic stealth technology of targets has made a major breakthrough. By accurately controlling the structural design and material response characteristics of electromagnetic metamaterials, the absorption, reflection or transmission characteristics of incident electromagnetic waves can be modulated in a specific frequency band, thereby significantly changing the electromagnetic appearance of the target in radar, infrared and microwave remote sensing systems.

[0004] With the continuous progress of electromagnetic metamaterial technology, liquid-based metamaterials have attracted widespread attention due to their unique performance advantages. Compared with traditional solid-state structures, liquid-based metamaterials have unique advantages such as flexibility, reconfigurability and strong structural tunability, which can more flexibly adapt to complex and variable electromagnetic environments, meet new demands such as dynamic stealth and adaptive regulation, and show important application potential in electromagnetic stealth, electronic countermeasures and other fields.

[0005] Patent application publication CN 113991314A discloses a liquid-based ultra-wideband transparent metamaterial wave absorber and a preparation method thereof. The liquid-based ultra-wideband transparent metamaterial wave absorber is composed of an array of multiple identical and cubic absorbing units. Each absorbing unit is composed of, from bottom to top, a resistive film bottom layer, a resin bottom layer, a liquid layer, a cross-shaped resin layer, a cylindrical resin layer, a resin top layer, and a resistive film top layer. The liquid layer is a top-opened columnar structure composed of an inner shell and an outer shell. The inner shell is a top-opened cylinder. The inner shell and the outer shell are coaxially arranged. The outer shell is a top-opened square. The outer shell is located at the periphery of the inner shell. A containing cavity is formed between the inner shell and the outer shell. The containing cavity is used to inject liquid. The cross-shaped resin layer is horizontally laid between the inner shell and the outer shell. The cylindrical resin layer is horizontally laid at the bottom of the inner shell. The top of the cylindrical resin layer is flush with the top of the inner shell. The lower side of the resin top layer is bonded to the upper side of the inner shell. The absorbing unit in the application is composed of up to seven layers of structure, which is not conducive to the realization of low profile of the device. The size is relatively large, which limits the refinement and integration capability of the structure. The liquid layer disclosed in the application adopts a double-shell structure and realizes the liquid filling function through a complex multi-layer resin and an embedded liquid cavity design. The structure design is relatively complex, and the processing and assembly difficulty is high. SUMMARY

[0006] The technical problem to be solved by the present application is to provide a liquid-based electromagnetic metamaterial with tunable emissivity, to realize flexible and tunable target emissivity in different backgrounds, and to reduce the visibility of the target in a microwave remote sensing system.

[0007] The present application provides a liquid-based electromagnetic metamaterial with tunable emissivity, which comprises a plurality of periodically arrayed basic units. Each basic unit comprises, from top to bottom, a dielectric layer, a dielectric slot layer, a substrate, and a conductive film layer. The dielectric slot layer is provided with a liquid cavity in the form of a rice character. The liquid cavity is formed by two cross-connected cross arms. Each cross arm comprises two mutually perpendicular straight arms of equal length. The length ratio of the straight arms on different cross arms is 1-1.2:1.

[0008] The liquid cavity in the form of a rice character is formed by two cross-connected cross arms. Each cross arm comprises two mutually perpendicular straight arms of equal length. The shape of each cross arm is a central symmetric connection of four straight arms. Each two straight arms are perpendicular to each other (i.e., two mutually perpendicular straight arms constitute a cross arm). The shape is equivalent to eight short arms connected at the center point.

[0009] The length ratio of the straight arms on different cross arms is 1-1.2:1, i.e., the length of the straight arm on cross arm I is 1-1.2 times the length of the straight arm on cross arm II.

[0010] Preferably, the base unit is square (preferably 4mm), the length of the straight arm is equal to the side of the base unit (preferably 4mm), and the width of the straight arm is 5-20% of the side of the base unit.

[0011] Preferably, the width of the straight arm of the cross arm parallel or perpendicular to the side of the base unit is 40-60% of the width of the straight arm of the other cross arm.

[0012] Preferably, the length ratio of the straight arms on different cross arms is 1:1.

[0013] Preferably, the included angle between adjacent straight arms on different cross arms is 45°.

[0014] Preferably, the liquid is water or an ethanol aqueous solution, and the volume concentration of the ethanol aqueous solution is 25-99%.

[0015] Preferably, the material of the dielectric layer is PMMA, the relative dielectric constant is 2.25, the loss tangent is 0.01, and the thickness is 1mm.

[0016] Preferably, the material of the dielectric groove layer is PMMA, the thickness of the me-shaped liquid cavity is 80-90% of the thickness of the dielectric groove layer, and the length of the me-shaped liquid cavity from the substrate is 0.1-0.2mm.

[0017] Preferably, the material of the substrate is PET, the relative dielectric constant is 3.2, the loss tangent is 0.003, and the thickness is 0.125mm.

[0018] Preferably, the material of the conductive film layer is an ITO conductive film, and the square resistance Rs is 6Ω / sq.

[0019] The present application has the beneficial effect that the present application can realize the tuning function of different emissivity in a wide frequency band by injecting different concentrations of ethanol solution into the dielectric groove structure with a me-shaped liquid cavity embedded inside. Simulation results show that the present application can realize stable and flexible tuning of emissivity in 20-55GHz, and the relative tuning bandwidth is 93.33%. When injecting pure water at 25℃, 25% ethanol, 50% ethanol, 75% ethanol, and 99% ethanol, the average emissivity in the tuning frequency band is 0.93, 0.92, 0.82, 0.63, and 0.33, respectively.

[0020] The emissivity-tunable liquid-based electromagnetic metamaterial designed in the present application has the characteristics of wideband stable tuning and optical transparency, and has the advantages of low profile, compact structure, easy processing, and low cost, etc., providing a new idea for the camouflage protection of high-value targets on the ground.

[0021] The application simplifies the structure configuration, significantly reduces the overall thickness of the device, has a more compact unit cycle size, can effectively compress the structure occupied area while ensuring the performance, and improves the applicability in high integration scenarios. The application realizes the injection of liquid and the regulation of emissivity by directly opening a single-layer liquid cavity in the dielectric groove layer, the structure is more simple, and large-scale preparation and practical application popularization are facilitated. On the basis of maintaining good electromagnetic performance, the application further optimizes the structure complexity and size, and has higher engineering practicability. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is the overall structure schematic diagram of the liquid-based electromagnetic metamaterial of the application.

[0023] Figure 2 is the top view of the overall structure of the liquid-based electromagnetic metamaterial of the application.

[0024] Figure 3 is the side view of the overall structure of the liquid-based electromagnetic metamaterial of the application.

[0025] Figure 4 is the rear view of the overall structure of the liquid-based electromagnetic metamaterial of the application.

[0026] Figure 5 is the regulation curve of the liquid-based electromagnetic metamaterial of the application to realize different emissivity.

[0027] Figure 6 is the emissivity regulation curve of the liquid-based electromagnetic metamaterial of the application, in which the dielectric groove layer with a rice-shaped liquid cavity embedded in the inside is replaced by a dielectric groove layer with a cylindrical liquid cavity embedded in the inside (i.e. comparative example 1).

[0028] Figure 7 is the emissivity regulation curve of the liquid-based electromagnetic metamaterial of the application, in which the dielectric groove layer with a rice-shaped liquid cavity embedded in the inside is replaced by a dielectric groove layer with a cross-shaped liquid cavity embedded in the inside (i.e. comparative example 2).

[0029] Figure 8 is the emissivity regulation curve of the liquid-based electromagnetic metamaterial of the application, in which the dielectric groove layer with a rice-shaped liquid cavity embedded in the inside is replaced by a dielectric groove layer with an improved rice-shaped liquid cavity embedded in the inside (i.e. comparative example 3).

[0030] Figure 9 is the regulation curve of the liquid-based electromagnetic metamaterial of the application to realize the target radiation brightness temperature.

[0031] In the figure, 1 is a dielectric layer, 2 is a dielectric groove layer, 3 is a substrate, 21 is a cross arm I, 22 is a cross arm II, and 4 is a conductive film layer. DETAILED DESCRIPTION

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the present invention. Example 1

[0034] like Figures 1-4 As shown, the emissivity-tunable liquid-based electromagnetic metamaterial of this embodiment includes multiple periodically arrayed basic units. Each basic unit comprises, from top to bottom, a dielectric layer 1, a dielectric tank layer 2, a substrate 3, and a conductive thin film layer 4, stacked sequentially. The dielectric tank layer 2 contains a star-shaped liquid cavity for storing liquid. This star-shaped liquid cavity is formed by two intersecting cross arms. Each cross arm includes two perpendicular straight arms of equal length, with the length ratio of the straight arms on different cross arms being 1-1.2:1 (1:1 in Example 1).

[0035] The basic unit is a square with a side length of [missing information]. p It is 4mm.

[0036] The dielectric layer 1 is made of PMMA with a relative permittivity of 2.25, a loss tangent of 0.01, and a thickness of [missing information]. h 1 = 1 mm.

[0037] Dielectric layer 2 and dielectric layer 1 are made of the same material, PMMA, with a relative permittivity of 2.25, a loss tangent of 0.01, and a thickness of [missing information]. h 2 = 1mm.

[0038] The medium tank layer 2 is provided with a star-shaped liquid cavity for storing liquid, which is obtained by creating grooves in the medium material. By filling the grooves with liquid and placing the medium layer 1 on top of the medium tank layer 2, and sealing it with UV-curable adhesive, the medium layer 1 and the medium tank layer 2 are obtained. That is, the medium tank layer 2 consists of two layers: a base layer and a grooved layer. The thickness of the base layer is... t 2. The thickness of the layer with grooves is t 1.

[0039] The depth of the groove is the same as the thickness of the star-shaped liquid cavity. t 1 represents the thickness of the medium tank layer. h 2 is 80-90%, preferably 90%, i.e., 0.9mm, and the length from the bottom of the cross-shaped liquid cavity to the top of the substrate 3 is...t 2 is 0.1-0.2mm, preferably 0.1mm.

[0040] The liquid stored in the star-shaped liquid cavity is water and aqueous solutions of ethanol at different concentrations.

[0041] The star-shaped liquid cavity is formed by two intersecting cross arms, such as... Figure 2 As shown, it includes crossarm I21 and crossarm II22. Crossarm I21 includes two straight arms of equal length and perpendicularity, with the same width. The two straight arms of crossarm I21 are either parallel or perpendicular to the sides of the square of the base unit, i.e., straight arm a is parallel to side a, and straight arm b is perpendicular to side a. The connection point between straight arms a and b is the midpoint of straight arms a and b.

[0042] The width of the straight arm of the cross arm (i.e., cross arm I 21) that is parallel or perpendicular to the edge of the base unit is 40-60% of the width of the straight arm of the other cross arm (i.e., cross arm II 22). Preferably, the length of the straight arm on cross arm I 21 is... l 1 = 4mm, width w 1 = 0.3 mm.

[0043] Cross arm II 22 comprises two perpendicular straight arms of equal length and width. The two straight arms of cross arm II 22 intersect and connect with cross arm I 21. The angle between adjacent straight arms on different cross arms is 45°, that is, the angle between the straight arm on adjacent cross arm I 21 and the straight arm on cross arm II 22 is 45°. The length of the straight arm on cross arm II 22... l 2 = 4mm, width w 2 = 0.56 mm.

[0044] The structure of cross arms I21 and II22 being intersected is equivalent to the ends of eight short arms being connected to the central origin, with the included angle between adjacent short arms being 45°.

[0045] The substrate 3 is made of PET, with a relative permittivity of 3.2, a loss tangent of 0.003, and a thickness of [missing information]. h 3 = 0.125 mm.

[0046] A low-resistance conductive thin film layer 4 (i.e., ITO conductive thin film) is disposed on the lower surface of substrate 3. For example... Figure 4 As shown, the conductive thin film layer 4 is a rectangular ITO thin film with a sheet resistance of Rs=6Ω / sq, and its side length is consistent with the side length of the metamaterial basic unit, completely covering the lower surface of the substrate. Example 2

[0047] like Figure 5 The image shows the use of Figure 1The emissivity of the shown liquid-based electromagnetic metamaterial at 20-55 GHz simulated by commercial electromagnetic simulation software CST Studio Suite is shown, in which the horizontal axis represents frequency and the vertical axis represents emissivity. It can be seen from the figure that when pure water at 25°C is injected into the medium groove layer with the embedded rice-shaped liquid cavity, the average emissivity is 0.93 within 20-55 GHz; when 25% ethanol (volume concentration, the same below) is injected, the average emissivity is 0.92; when 50% ethanol is injected, the average emissivity is 0.82; when 75% ethanol is injected, the average emissivity is 0.63; and when 99% ethanol is injected, the average emissivity is 0.33.

[0048] The simulation results show that the present application can realize stable and flexible tuning of emissivity at 20-55 GHz, and the relative tuning bandwidth is 93.33%. At the same time, since the rice-shaped liquid cavity structure is used to store the solution, the structure has the characteristics of axial symmetry, and therefore has the polarization-insensitive characteristic.

[0049] Comparative Example 1

[0050] On the basis of the above embodiment, the rice-shaped liquid cavity structure is replaced by a medium groove layer with an embedded cylindrical liquid cavity, which is used to store ethanol solutions with different concentrations, namely Comparative Example 1. The radius of the cylindrical liquid cavity is 0.5 mm, and the thickness is consistent with that of the rice-shaped liquid cavity structure, i.e. t 1=0.9mm. Figure 6 The emissivity of the medium groove layer with the embedded cylindrical liquid cavity at 20-55 GHz is shown, in which the horizontal axis represents frequency and the vertical axis represents emissivity. It can be seen from the figure that when pure water at 25°C is injected, the average emissivity is 0.33 within 20-55 GHz; when 25% ethanol is injected, the average emissivity is 0.29; when 50% ethanol is injected, the average emissivity is 0.25; when 75% ethanol is injected, the average emissivity is 0.20; and when 99% ethanol is injected, the average emissivity is 0.16.

[0051] It can be seen that when the medium groove layer with the embedded cylindrical liquid cavity is used, the structure emissivity gradually decreases with the increase of the injected ethanol concentration, but the change range is relatively limited, and it is difficult to be applied to the flexible regulation of the target radiation characteristics under different emissivity backgrounds.

[0052] Comparative Example 2

[0053] On the basis of the above embodiment, the rice-shaped liquid cavity structure is replaced by a medium groove layer with an embedded cross-shaped liquid cavity, which is used to store ethanol solutions with different concentrations, namely Comparative Example 2. The length of the cross-shaped liquid cavity is 2 mm, the width is 0.28 mm, and the thickness is consistent with that of the rice-shaped liquid cavity structure, i.e. t 1=0.9mm, the structure is 0.1mm away from the top of the substrate t 2=0.1mm. Figure 7The emissivity of the medium groove layer with the cross-shaped liquid cavity embedded inside at 20-55 GHz is shown, the abscissa represents the frequency, and the ordinate represents the emissivity. As can be seen from the figure, when injecting 25℃ pure water at 20-55 GHz, the average emissivity is 0.56; when injecting 25% ethanol, the average emissivity is 0.40; when injecting 50% ethanol, the average emissivity is 0.31; when injecting 75% ethanol, the average emissivity is 0.23; and when injecting 99% ethanol, the average emissivity is 0.16.

[0054] Therefore, when the medium groove layer with the cross-shaped liquid cavity embedded inside is used, the structural emissivity gradually decreases with the increase of the ethanol concentration, but the change range is also relatively limited. At the same time, since the maximum average emissivity of the structure is only 0.56, it is difficult to be applied to the case where the target is in a high emissivity background. Therefore, by comparing with the design of the invented “rice”-shaped liquid cavity structure, it can be seen that the tunable emissivity of the comparative example is limited, and it is difficult to be applied to the regulation of the radiation characteristics of the low emissivity target in a high emissivity background.

[0055] Comparative Example 3

[0056] On the basis of the above embodiment, the “rice”-shaped liquid cavity structure is replaced by a medium groove layer with an improved “rice”-shaped liquid cavity embedded inside, that is, the length of the central cross arm is shortened, and it is used to store different concentrations of ethanol solution, that is, Comparative Example 3. The length of the central cross arm of the improved “rice”-shaped liquid cavity is 1.4 mm, the width is 0.2 mm, and the thickness is 0.9 mm; the length of the cross diagonal cross (and the included angle with the side of the basic unit is 45°) is 2.6 mm, the width is 0.28 mm, and the thickness is 0.9 mm. The overall structure is 0.1 mm away from the top of the substrate, and the thickness of the dielectric layer is 1.0 mm.

[0057] Figure 8 The emissivity of the medium groove layer with the improved “rice”-shaped liquid cavity embedded inside at 20-55 GHz is shown, the abscissa represents the frequency, and the ordinate represents the emissivity. As can be seen from the figure, when injecting 25℃ pure water at 20-55 GHz, the average emissivity is 0.75; when injecting 25% ethanol, the average emissivity is 0.56; when injecting 50% ethanol, the average emissivity is 0.42; when injecting 75% ethanol, the average emissivity is 0.29; and when injecting 99% ethanol, the average emissivity is 0.19.

[0058] Therefore, compared with the improved type of "rice" liquid cavity structure, the rice type liquid cavity structure proposed in the present application shows stronger adaptability and practical value in the regulation ability and application scenarios. The improved type of "rice" liquid cavity structure is difficult to meet the demand of low emissivity target in complex background for the regulation of radiation characteristics. Example 3

[0059] Figure 9 An example of using the emissivity tunable liquid-based electromagnetic metamaterial (the dielectric slot layer embedded with the rice type liquid cavity) of the proposed embodiment 1 to regulate the brightness temperature characteristics of the ground metal target is shown.

[0060] In the simulation, the brightness temperature of the sky and the environment is assumed to be 55K and 300K respectively, and since the metal target only reflects the radiation from the sky, the brightness temperature of the metal target is also set to 55K; the working frequency of the microwave radiometer is set to 37GHz, so the emissivity of the metamaterial at 37GHz when injecting different liquids is taken for calculation. At 37GHz, when the liquid-based metamaterial is placed on the ground metal target, when injecting pure water, its emissivity is 0.96, so its brightness temperature is 290.2K; when injecting 25% ethanol, its emissivity is 0.93, so its brightness temperature is 282.85K; when injecting 50% ethanol, its emissivity is 0.81, so its brightness temperature is 253.45K; when injecting 75% ethanol, its emissivity is 0.59, so its brightness temperature is 199.55K; when injecting 99% ethanol, its emissivity is 0.31, so its brightness temperature is 130.95K.

[0061] Therefore, by adjusting the concentration of ethanol solution in the liquid-based metamaterial, the emissivity of the metamaterial can be effectively controlled, so as to realize flexible regulation of the brightness temperature of the ground metal target. This characteristic makes the liquid-based electromagnetic metamaterial have important application potential in the field of passive microwave remote sensing camouflage: when the target is in a high brightness temperature background, a liquid with high emissivity, such as pure water or 25% ethanol, can be injected to make the brightness temperature close to the background and reduce the target contrast; while in a low brightness temperature background, the brightness temperature can be significantly reduced by injecting high-concentration ethanol, so as to realize the brightness temperature matching of the target and the environment. In this way, the target will exhibit similar microwave radiation characteristics to the background in passive microwave remote sensing imaging, thereby reducing its detectability. The proposed liquid-based electromagnetic metamaterial design with tunable emissivity has the advantages of flexible regulation, optical transparency, low cost, easy processing, etc., and is especially suitable for scenarios where the target and the background present high brightness temperature contrast, to realize effective brightness temperature camouflage and radiation stealth. It provides a new technical solution and development approach for the radiation stealth technology of ground high-value targets, and has important practical application value for promoting the innovative development of electromagnetic stealth technology.

[0062] It should be understood by those of ordinary skill in the art that the above discussion of any embodiment is only exemplary and is not intended to imply that the scope of protection of the present application is limited to these examples; under the idea of the present application, the above embodiments or technical features in different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes of different aspects of one or more embodiments of the present application as described above. In order to be brief, they are not provided in details.

[0063] One or more embodiments of the present application are intended to cover all such alternatives, modifications and variations falling within the broad scope of the present application. Therefore, any omissions, modifications, equivalent replacements, improvements, etc. made in the spirit and principles of one or more embodiments of the present application should be included in the scope of protection of the present application.

Claims

1. A liquid-based electromagnetic metamaterial with tunable emissivity, characterized in that, The application relates to a substrate unit for a liquid crystal display, which comprises a plurality of periodically arranged basic units, wherein the basic unit comprises a medium layer (1), a medium groove layer (2), a substrate (3) and a conductive film layer (4) which are arranged in sequence from top to bottom, the medium groove layer (2) is provided with a liquid chamber in the shape of a Chinese character'mi' for storing liquid, the liquid chamber in the shape of a Chinese character'mi' is formed by two cross-connected cross arms, the cross arm comprises two mutually perpendicular straight arms, the straight arms on each cross arm are equal in length, the length ratio of the straight arms on the two cross-connected cross arms is 1-1.2:1, and the liquid stored in the liquid chamber in the shape of a Chinese character'mi' is an ethanol aqueous solution with different concentrations.

2. The liquid-based electromagnetically metamaterial with tunable emissivity of claim 1, wherein, The basic unit is square, the length of the straight arm is equal to the side length of the basic unit, and the width of the straight arm is 5-20% of the side length of the basic unit.

3. The liquid-based electromagnetically metamaterial with tunable emissivity of claim 2, wherein, The width of the straight arm of the cross arm parallel or perpendicular to the side of the basic unit is 40-60% of the width of the straight arm of the other cross arm.

4. The liquid-based electromagnetically metamaterial with tunable emissivity according to any one of claims 1-3, characterized in that, The length ratio of the straight arms on different cross arms is 1:

1.

5. The liquid-based electromagnetically metamaterial with tunable emissivity according to any one of claims 1-3, characterized in that, The included angle between the adjacent straight arms on different cross arms is 45 DEG.

6. The emissivity-tunable liquid-based electromagnetic metamaterial according to any one of claims 1-3, characterized in that, The material of the medium layer (1) is PMMA, the relative dielectric constant is 2.25, the loss tangent is 0.01, and the thickness is 1 mm.

7. The emissivity-tunable liquid-based electromagnetic metamaterial according to any one of claims 1-3, characterized in that, The material of the medium groove layer (2) is PMMA, the thickness of the liquid chamber in the shape of a Chinese character'mi' is 80-90% of the thickness of the medium groove layer (2), and the length from the bottom of the liquid chamber in the shape of a Chinese character'mi' to the substrate (3) is 0.1-0.2 mm.

8. The emissivity-tunable liquid-based electromagnetic metamaterial according to any one of claims 1-3, characterized in that, The material of the substrate (3) is PET, the relative dielectric constant is 3.2, the loss tangent is 0.003, and the thickness is 0.125 mm.

9. The emissivity-tunable liquid-based electromagnetic metamaterial according to any one of claims 1-3, characterized in that, The material of the conductive film layer (4) is ITO conductive film, and the square resistance Rs is 6 Omega / sq.

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