Liquid-based electromagnetic metamaterial with tunable emissivity

Abstract

The invention belongs to the technical field of metamaterials, and particularly relates to a liquid-based electromagnetic metamaterial with tunable emissivity, which comprises a plurality of basic units in periodic array distribution, and each basic unit comprises a dielectric layer, a dielectric groove layer, a substrate and a conductive film layer which are sequentially stacked and arranged from top to bottom, a liquid cavity shaped like a Chinese character'mi 'and used for storing liquid is formed in the medium groove layer, the liquid cavity shaped like the Chinese character'mi' is formed by two cross arms which are connected in a crossed mode, each cross arm comprises two straight arms which are perpendicular to each other and equal in length, and the length ratio of the straight arms on the different cross arms is 1-1.2: 1. And the visibility of the target in the microwave remote sensing system is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of metamaterials, and in particular relates to a liquid-based electromagnetic metamaterial with tunable emissivity. Background Art

[0002] With the diversification of target detection methods and the continuous improvement of detection accuracy, microwave radiometers are playing an increasingly prominent role in modern target detection systems due to their advantages such as passive detection, high concealment, and all-day and all-weather operation. However, these advances in target detection technology have placed higher demands on the concealment of high-value ground targets. Therefore, how to effectively improve the survivability of high-value ground targets and reduce their detectability in passive remote sensing systems has become a major research topic.

[0003] Electromagnetic metamaterials, a class of materials composed of artificially designed subwavelength periodic structures, can achieve unique electromagnetic response properties that are difficult to achieve in natural materials. In recent years, they have driven significant breakthroughs in target electromagnetic stealth technology. By precisely controlling the structural design and material response of electromagnetic metamaterials, the absorption, reflection, or transmission characteristics of incident electromagnetic waves can be modulated in specific frequency bands, significantly changing the target's electromagnetic appearance in radar, infrared, and microwave remote sensing systems.

[0004] With the continuous advancement 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 offer unique advantages such as flexible reconfigurability and strong structural adjustability. They can more flexibly adapt to complex and changing electromagnetic environments, meet emerging requirements such as dynamic stealth and adaptive control, and demonstrate significant application potential in fields such as electromagnetic stealth and electronic countermeasures.

[0005] Patent application publication number CN 113991314A discloses a liquid-based ultra-wideband transparent metamaterial absorber and a preparation method thereof. The absorber comprises an array of multiple identical, cubical absorbing units. Each absorbing unit comprises, 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 an open-top cylindrical structure composed of an inner shell and an outer shell. The inner shell is an open-top cylindrical structure, coaxially arranged with the outer shell. The outer shell is an open-top cubic structure located outside the inner shell, forming a cavity between the inner and outer shells for injecting liquid. The cross-shaped resin layer is horizontally laid between the inner and outer shells. The cylindrical resin layer is located within the inner shell and horizontally laid on the bottom of the inner shell. The top of the cylindrical resin layer is flush with the top of the inner shell, and the bottom of the resin top layer is bonded to the upper side of the inner shell. The absorber unit described in this application consists of as many as seven layers, hindering the realization of a low-profile device. Its large size limits the structural refinement and integration capabilities. The liquid layer disclosed in this application utilizes a double-shell structure, achieving liquid filling through a complex multi-layer resin and embedded liquid cavity design. This results in a complex structural design and significant processing and assembly challenges. Summary of the Invention

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

[0007] An embodiment of the present invention provides a liquid-based electromagnetic metamaterial with tunable emissivity, comprising a plurality of basic units distributed in a periodic array. The basic unit comprises a dielectric layer, a dielectric slot layer, a substrate, and a conductive film layer stacked in sequence from top to bottom. A 'M'-shaped liquid cavity for storing liquid is provided in the dielectric slot layer. The 'M'-shaped liquid cavity is formed by two cross-connected cross arms. The cross arms include two mutually perpendicular straight arms of equal length, and the length ratio of the straight arms on different cross arms is 1-1.2:1.

[0008] The 'M'-shaped liquid chamber is formed by two cross-connected cross arms, each of which includes two perpendicular straight arms of equal length. The cross arm is shaped like four straight arms connected symmetrically around the center, with each pair of straight arms perpendicular to each other (i.e., two perpendicular straight arms form a cross arm). This shape is equivalent to eight short arms connected at their ends at the central origin.

[0009] The length ratio of the straight arms on different cross arms is 1-1.2:1, that is, 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 basic unit is a square (preferably 4 mm), the length of the straight arm is equal to the side of the basic unit (preferably 4 mm), and the width of the straight arm is 5-20% of the side length of the basic unit.

[0011] Preferably, the width of the straight arm of the cross arm that is parallel or perpendicular to the side length of the basic 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 angle between adjacent straight arms on different cross arms is 45°.

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

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

[0016] Preferably, the material of the dielectric slot layer is PMMA, the thickness of the 'M'-shaped liquid cavity is 80-90% of the thickness of the dielectric slot layer, and the distance between the bottom of the 'M'-shaped liquid cavity and the substrate is 0.1-0.2 mm.

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

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

[0019] The beneficial effect of the present invention is that it can achieve tuning of different emissivities within a wide frequency band by injecting ethanol solutions of different concentrations into a dielectric tank structure embedded with a 'M'-shaped liquid cavity. Simulation results show that the present invention can achieve stable and flexible tuning of emissivity in the 20-55 GHz range, with a relative tuning bandwidth of 93.33%. When 25°C pure water, 25% ethanol, 50% ethanol, 75% ethanol, and 99% ethanol were injected, average emissivities of 0.93, 0.92, 0.82, 0.63, and 0.33 were achieved within the tuning band, respectively.

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

[0021] This invention simplifies the structural configuration and significantly reduces the overall thickness of the device. Its more compact unit period size effectively reduces the structural footprint while maintaining performance, enhancing its applicability in highly integrated scenarios. By directly creating a single-layer liquid cavity within the dielectric slot layer, this invention enables liquid injection and emissivity control, resulting in a simpler structure and ease of large-scale preparation and practical application. While maintaining excellent electromagnetic performance, this invention further optimizes structural complexity and volume size, resulting in greater engineering practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the overall structure of the liquid-based electromagnetic metamaterial of the present invention.

[0023] Figure 2 It is a top view of the overall structure of the liquid-based electromagnetic metamaterial of the present invention.

[0024] Figure 3 It is a side view of the overall structure of the liquid-based electromagnetic metamaterial of the present invention.

[0025] Figure 4 This is a rear view of the overall structure of the liquid-based electromagnetic metamaterial of the present invention.

[0026] Figure 5 This is the control curve for achieving different emissivity of the liquid-based electromagnetic metamaterial of the present invention.

[0027] Figure 6 This is the emissivity control curve of the liquid-based electromagnetic metamaterial of the present invention, in which the dielectric slot layer with the 'M'-shaped liquid cavity embedded therein is replaced with a dielectric slot layer with a cylindrical liquid cavity embedded therein (i.e., comparative example 1).

[0028] Figure 7 This is the emissivity control curve of the liquid-based electromagnetic metamaterial of the present invention, in which the dielectric slot layer with the 'M'-shaped liquid cavity embedded therein is replaced with a dielectric slot layer with a cross-shaped liquid cavity embedded therein (i.e., comparative example 2).

[0029] Figure 8 This is the emissivity control curve of the liquid-based electromagnetic metamaterial of the present invention, in which the dielectric slot layer with the 'M'-shaped liquid cavity embedded therein is replaced with a dielectric slot layer with an improved 'M'-like liquid cavity embedded therein (i.e., comparative example 3).

[0030] Figure 9 This is the control curve for the liquid-based electromagnetic metamaterial of the present invention to achieve the target radiation brightness temperature.

[0031] In the figure, 1 is a dielectric layer, 2 is a dielectric slot 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 following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0033] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments, but it is not intended to limit the present invention. Example 1

[0034] like Figure 1-4 As shown, the liquid-based electromagnetic metamaterial with tunable emissivity of this embodiment includes multiple basic units distributed in a periodic array. The basic units include a dielectric layer 1, a dielectric slot layer 2, a substrate 3, and a conductive film layer 4, which are stacked in sequence from top to bottom. A 'V'-shaped liquid cavity for storing liquid is provided within the dielectric slot layer 2. The 'V'-shaped liquid cavity is formed by two cross-connected cross arms, each of which includes two perpendicular straight arms of equal length. The length ratio of the straight arms on different cross arms is 1-1.2:1 (1:1 in Example 1).

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

[0036] The material of dielectric layer 1 is PMMA, with relative dielectric constant of 2.25, loss tangent of 0.01 and thickness of h 1=1mm.

[0037] The material of dielectric slot layer 2 is the same as that of dielectric layer 1, which is PMMA with a relative dielectric constant of 2.25, a loss tangent of 0.01, and a thickness of h 2=1mm.

[0038] The dielectric slot layer 2 is provided with a crisscross liquid cavity for storing liquid, which is obtained by opening a groove on the dielectric material. By filling the groove with liquid, placing the dielectric layer 1 on the dielectric slot layer 2, and sealing them with UV shadowless glue, the dielectric layer 1 and the dielectric slot layer 2 can be obtained. That is, the dielectric slot layer 2 includes two layers, namely the base layer and the layer with the groove. 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 thickness of the M-shaped liquid cavity. t 1 is the thickness of dielectric slot layer 2 h 2 is 80-90%, preferably 90%, that is, 0.9 mm. The distance between the bottom of the M-shaped liquid chamber and the top of the substrate 3 ist 2 is 0.1-0.2 mm, preferably 0.1 mm.

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

[0041] The M-shaped liquid chamber is formed by two cross-connected cross arms, such as Figure 2 As shown, it includes cross arm I 21 and cross arm II 22. Cross arm I 21 includes two mutually perpendicular straight arms of equal length and the same width. The two straight arms of cross arm I 21 are respectively parallel or perpendicular to the sides of the square of the basic unit, that is, straight arm a is parallel to side a, and straight arm b is perpendicular to side a. The connection point of 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) 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 (i.e., cross arm II 22). Preferably, the length of the straight arm on the cross arm I 21 is l 1=4mm, width w 1=0.3mm.

[0043] Cross arm II 22 includes two straight arms of equal length and perpendicular to each other. The two straight arms of cross arm II 22 are also of the same width. The two straight arms of cross arm II 22 are cross-connected with cross arm I 21. The angle between adjacent straight arms on different cross arms is 45 degrees, that is, the angle between the adjacent straight arms on cross arm I 21 and the straight arms on cross arm II 22 is 45 degrees. The length of the straight arms on cross arm II 22 l 2=4mm, width w 2=0.56mm.

[0044] The cross-arm I 21 and the cross-arm II 22 are cross-connected in a structure that is equivalent to eight short arms having their ends connected at a central origin, with an angle of 45° between adjacent short arms.

[0045] The material of substrate 3 is PET, with a relative dielectric constant of 3.2, a loss tangent of 0.003, and a thickness of h 3=0.125mm.

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

[0047] like Figure 5 Shown is the use of Figure 1The emissivity of the liquid-based electromagnetic metamaterial shown in the figure is simulated in the 20–55 GHz range using the commercial electromagnetic simulation software CSTStudio Suite. The horizontal axis represents frequency, and the vertical axis represents emissivity. The figure shows that within the 20–55 GHz range, when pure water at 25°C is injected into the dielectric slot layer with the internally embedded 'P'-shaped liquid cavity, the average emissivity is 0.93; 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] Simulation results show that the present invention can achieve stable and flexible tuning of the emissivity from 20 to 55 GHz, with a relative tuning bandwidth of 93.33%. Furthermore, due to the use of a 'Piezo' liquid cavity structure to store the solution, the structure is axisymmetric and therefore polarization-insensitive.

[0049] Comparative Example 1

[0050] On the basis of the above embodiment, the 'M'-shaped liquid cavity structure is replaced by a dielectric tank layer with a cylindrical liquid cavity embedded inside, which is used to store ethanol solutions of different concentrations, i.e., Comparative Example 1. The radius of the cylindrical liquid cavity is 0.5 mm, and the thickness is consistent with the 'M'-shaped liquid cavity structure, i.e. t 1=0.9mm. Figure 6 The emissivity of a dielectric slot layer embedded with a cylindrical liquid cavity at 20–55 GHz is shown, with frequency on the horizontal axis and emissivity on the vertical axis. The figure shows that, when injected with 25°C pure water, the average emissivity is 0.33; when injected with 25% ethanol, the average emissivity is 0.29; when injected with 50% ethanol, the average emissivity is 0.25; when injected with 75% ethanol, the average emissivity is 0.20; and when injected with 99% ethanol, the average emissivity is 0.16.

[0051] It can be concluded that when a dielectric slot layer with a cylindrical liquid cavity embedded inside is used, the structural emissivity shows a gradual downward trend with the increase of the injected ethanol concentration, but the range of change is relatively limited, which makes it difficult to apply it 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 'M'-shaped liquid cavity structure is replaced by a dielectric tank layer with a cross-shaped liquid cavity embedded therein, which is used to store ethanol solutions of different concentrations, i.e., Comparative Example 2. The cross-shaped liquid cavity is 2 mm long, 0.28 mm wide, and has the same thickness as the 'M'-shaped liquid cavity structure, i.e. t 1=0.9mm, the distance between the structure and the top of the substrate t 2=0.1mm. Figure 7The emissivity of a dielectric slot layer embedded with a cross-shaped liquid cavity at 20–55 GHz is shown, with frequency on the horizontal axis and emissivity on the vertical axis. The figure shows that, when injected with 25°C pure water, the average emissivity is 0.56; when injected with 25% ethanol, the average emissivity is 0.40; when injected with 50% ethanol, the average emissivity is 0.31; when injected with 75% ethanol, the average emissivity is 0.23; and when injected with 99% ethanol, the average emissivity is 0.16.

[0054] As can be seen, when using a dielectric slot layer with an embedded cross-shaped liquid cavity, the structural emissivity also shows a gradual downward trend with increasing ethanol concentration, but the magnitude of the change is also relatively limited. Furthermore, since the maximum average emissivity of this structure is only 0.56, it is not suitable for use when the target is located in a high-emissivity background. Therefore, by comparison with the cross-shaped liquid cavity structure designed in the present invention, the achievable tunable emissivity of this comparative example is limited, making it difficult to apply to the radiation characteristics of low-emissivity targets in a high-emissivity background.

[0055] Comparative Example 3

[0056] Based on the above example, the 'R'-shaped liquid cavity structure was replaced with a dielectric slot layer embedded with an improved 'R'-shaped liquid cavity. This structure, with the central cross arm shortened, was used to store ethanol solutions of varying concentrations, namely Comparative Example 3. The central cross arm of the improved 'R'-shaped liquid cavity is 1.4 mm long, 0.2 mm wide, and 0.9 mm thick; the cross (forming a 45° angle with the sides of the base unit) is 2.6 mm long, 0.28 mm wide, and 0.9 mm thick. The overall structure is 0.1 mm from the top of the substrate, and the dielectric layer is 1.0 mm thick.

[0057] Figure 8 The emissivity of a dielectric slot layer embedded with an improved "M"-shaped liquid cavity is shown in the 20–55 GHz range. The horizontal axis represents frequency, and the vertical axis represents emissivity. The figure shows that when injected with 25°C pure water, the average emissivity is 0.75; when injected with 25% ethanol, the average emissivity is 0.56; when injected with 50% ethanol, the average emissivity is 0.42; when injected with 75% ethanol, the average emissivity is 0.29; and when injected with 99% ethanol, the average emissivity is 0.19.

[0058] It can be concluded that when the dielectric slot layer of the improved "M"-shaped liquid cavity is used, as the concentration of the injected ethanol continues to increase, the emissivity of the structure shows a certain degree of decreasing trend, but the overall control range is still relatively limited. In addition, the maximum average emissivity that can be achieved by this structure within the tuning frequency band is only 0.86, which is lower than the requirements of the high-emissivity background environment. Therefore, compared with the improved "M"-shaped liquid cavity structure, the "M"-shaped liquid cavity structure proposed in the present invention shows stronger adaptability and practical value in terms of control ability and applicable scenarios. The improved "M"-shaped liquid cavity structure is difficult to meet the needs of controlling the radiation characteristics of low-emissivity targets under complex backgrounds. Example 3

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

[0060] The simulation assumes the brightness temperatures of the sky and the environment are 55K and 300K, respectively. Since the metal target only reflects radiation from the sky, its brightness temperature is also set to 55K. The microwave radiometer operates at 37 GHz, so the emissivity of the metamaterial at 37 GHz when injected with different liquids is used for calculation. At 37 GHz, when the liquid-based metamaterial is placed on a ground-based metal target, its emissivity is 0.96 when injected with pure water, resulting in a brightness temperature of 290.2K; when injected with 25% ethanol, its emissivity is 0.93, resulting in a brightness temperature of 282.85K; when injected with 50% ethanol, its emissivity is 0.81, resulting in a brightness temperature of 253.45K; when injected with 75% ethanol, its emissivity is 0.59, resulting in a brightness temperature of 199.55K; and when injected with 99% ethanol, its emissivity is 0.31, resulting in a brightness temperature of 130.95K.

[0061] It can be concluded that by adjusting the concentration of the ethanol solution in the liquid-based metamaterial, the metamaterial's emissivity can be effectively controlled, thereby achieving flexible control of the brightness temperature of ground metal targets. This property makes liquid-based electromagnetic metamaterials have significant application potential in passive microwave remote sensing camouflage. When the target is in a high brightness temperature background, the injection of a high-emissivity liquid, such as pure water or 25% ethanol, can bring its brightness temperature close to the background, reducing the target contrast. Conversely, in a low brightness temperature background, the injection of high-concentration ethanol can significantly reduce the brightness temperature, achieving brightness temperature matching between the target and the environment. In this way, the target will exhibit microwave radiation characteristics similar to those of the background in passive microwave remote sensing imaging, reducing its detectability. The proposed design of a liquid-based electromagnetic metamaterial with tunable emissivity offers advantages such as flexible control, optical transparency, low cost, and easy processing. It is particularly suitable for scenarios with high brightness temperature contrast between the target and the background, achieving effective brightness temperature camouflage and radiation stealth. This provides a new technical solution and development path for radiation stealth technology for high-value ground targets and has important practical application value in promoting the innovative development of electromagnetic stealth technology.

[0062] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of protection of the present application is limited to these examples. In line with the present application, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of different aspects of one or more embodiments of the present application as described above, which are not provided in detail for the sake of simplicity.

[0063] The one or more embodiments of this application are intended to encompass all such substitutions, modifications, and variations that fall within the broad scope of this application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of one or more embodiments of this application should be included in the scope of protection of this application.

Claims

1. A liquid-based electromagnetic metamaterial with tunable emissivity, characterized in that: The invention comprises a plurality of basic units distributed in a periodic array, wherein the basic units comprise a dielectric layer (1), a dielectric slot layer (2), a substrate (3) and a conductive film layer (4) which are stacked in sequence from top to bottom, wherein a 'M'-shaped liquid cavity for storing liquid is provided in the dielectric slot layer (2), wherein the 'M'-shaped liquid cavity is formed by two cross-connected cross arms, wherein the cross arms comprise two mutually perpendicular straight arms of equal length, and the length ratio of the straight arms on different cross arms is 1-1.2:

1.

2. The liquid-based electromagnetic metamaterial with tunable emissivity according to claim 1, wherein: The basic unit is a 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 electromagnetic metamaterial with tunable emissivity according to claim 2, wherein: The width of the straight arm of the cross arm parallel to or perpendicular to the side of the base unit is 40-60% of the width of the straight arm of the other cross arm.

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

1.

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

6. The liquid-based electromagnetic metamaterial with tunable emissivity according to any one of claims 1 to 3, characterized in that: The liquid is water or ethanol aqueous solution.

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

8. The liquid-based electromagnetic metamaterial with tunable emissivity according to any one of claims 1 to 3, characterized in that: The material of the dielectric slot layer (2) is PMMA, the thickness of the 'M'-shaped liquid cavity is 80-90% of the thickness of the dielectric slot layer (2), and the distance between the bottom of the 'M'-shaped liquid cavity and the substrate (3) is 0.1-0.2 mm.

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

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

Images