Underwater visible light invisible micro-nano hollow sphere and design method thereof

Abstract

The invention discloses an underwater visible light invisible micro-nano hollow sphere and a design method thereof.The underwater visible light invisible micro-nano hollow sphere comprises a spherical shell and a cavity located in the spherical shell, the spherical shell is made of a glass material or an optical coating material, and the outer radius of the spherical shell is within the range of 1 nm to 2 microns; the inner radius, the outer radius and the dielectric constant of the spherical shell meet a preset formula. The device is simple in structure and low in manufacturing cost, a micro-nano sensor / detector can be carried, underwater invisible detection and attraction convenience is improved, and the device can be widely applied to the technical field of underwater detection.

Description

Technical Field

[0001] The present invention relates to the field of underwater detection technology, and in particular to an underwater visible light invisible micro-nano hollow sphere and a design method thereof. Background Art

[0002] Visible light stealth or stealth technology has a wide range of applications in the fields of military stealth, fun stealth toys, and beautiful stealth design. General visible light stealth is divided into active stealth and passive stealth. Active stealth relies on the light-emitting layer to actively emit light close to the background light to hide itself. Passive stealth includes electromagnetic wave absorption layers, metamaterials, complex geometric structures, coatings that are consistent with the color of the surrounding environment, camouflage layers, complex optical fiber / waveguide structures, etc. In addition to invisible visible light, invisible sound waves are usually required underwater. There are three main methods for invisible sound waves: ① Use new materials such as fiberglass, synthetic rubber, and reinforced plastics; ② Apply sound-absorbing coatings on the surface of objects; ③ Use new materials with high sound permeability to allow most of the sound waves emitted by sonar to penetrate objects.

[0003] Some stealth solutions for large-sized objects have been proposed in related technologies, but they cannot be applied to the micro-nano field. However, the research on micro-nano sensors and detectors is also very active today, and it is necessary to design a micro-nano stealth spherical shell to hide such sensors / detectors. Therefore, the research on micro-nano scale optical stealth spherical shells is very important.

[0004] Related technologies have also proposed a micro-nano optical stealth structure based on butterfly wing bionics technology, but the structure is complex to process and is only suitable for stealth in the air. It is also impossible to hide objects inside the structure to achieve stealth. Summary of the invention

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide an underwater visible light invisible micro-nano hollow sphere and a design method thereof. The underwater visible light invisible micro-nano hollow sphere has a simple structure, low production cost, and can be equipped with micro-nano sensors / detectors, thereby improving the convenience of underwater invisible detection and luring.

[0006] The first technical solution adopted by the present invention is:

[0007] An underwater visible light invisible micro-nano hollow sphere comprises a spherical shell and a cavity inside the spherical shell, wherein the spherical shell is made of glass material or optical coating material, the outer radius of the spherical shell is within the range of 1nm-2μm, and the inner radius, outer radius and dielectric constant of the spherical shell satisfy the following formula:

[0008]

[0009] Wherein, r1 represents the inner radius of the spherical shell, r2 represents the outer radius of the spherical shell, ε1 represents the dielectric constant of air, ε2 represents the dielectric constant of the spherical shell, ε m Represents the dielectric constant of the background medium.

[0010] Furthermore, the spherical shell is made of glass material, the inner radius of the spherical shell is 0.53 μm, and the outer radius of the spherical shell is 1 μm.

[0011] Furthermore, the spherical shell is made of magnesium fluoride optical coating material, the inner radius of the spherical shell is 0.72 μm, and the outer radius of the spherical shell is 1 μm.

[0012] Furthermore, the spherical shell is made of zinc sulfide optical coating material, the inner radius of the spherical shell is 0.92 μm, and the outer radius of the spherical shell is 1 μm.

[0013] Furthermore, the spherical shell is prepared by any one of a template method, a self-assembly method, a spray drying method, an emulsion polymerization method, an electric spark-ultrasonic composite processing method, a sol-gel method, and a self-reaction quenching method.

[0014] Furthermore, the spherical shell is prepared by any one of a template method, a self-assembly method, a spray drying method, an emulsion polymerization method, an electric spark-ultrasonic composite processing method, a sol-gel method, and a self-reaction quenching method.

[0015] Furthermore, the spherical shell has low sound wave reflectivity and high sound wave absorptivity / transmittance.

[0016] The second technical solution adopted by the present invention is:

[0017] A design method for underwater visible light invisible micro-nano hollow spheres comprises the following steps:

[0018] Constructing a first spherical surface and a second spherical surface of a hollow sphere, wherein the first spherical surface and the second spherical surface have the same spherical center, and the first spherical surface is located inside the second spherical surface, a uniform air medium is distributed inside the first spherical surface, a uniform first optical medium is distributed between the second spherical surface and the first spherical surface, and a uniform background medium is distributed outside the second spherical surface;

[0019] Determine a first potential field inside the first spherical surface, a second potential field between the second spherical surface and the first spherical surface, and a third potential field outside the second spherical surface;

[0020] The first potential field, the second potential field and the third potential field are set to be continuous on the first spherical surface and the second spherical surface, and the polarizability expression of the hollow sphere is obtained;

[0021] Setting the numerator of the polarizability expression equal to 0, obtaining a first relationship between the diameter of the first spherical surface, the diameter of the second spherical surface, and the dielectric constant of the first optical medium, the dielectric constant of air, and the dielectric constant of the background medium;

[0022] Determine the dielectric constants of the first optical medium and the background medium, and determine the radius of the second spherical surface, and obtain the radius of the first spherical surface by solving the first relationship;

[0023] The radius of the first spherical surface is used as an inner radius and the radius of the second spherical surface is used as an outer radius to obtain geometric parameters of a spherical shell, and the first optical medium is used as a preparation material of the spherical shell.

[0024] Further, the polarizability expression is as follows:

[0025]

[0026] Wherein, α represents the polarizability, r1 represents the radius of the first spherical surface, r2 represents the radius of the second spherical surface, ε1 represents the dielectric constant of air, ε2 represents the dielectric constant of the first optical medium, ε m Represents the dielectric constant of the background medium.

[0027] Further, the first relational equation is as follows:

[0028]

[0029] Wherein, r1 represents the radius of the first spherical surface, r2 represents the radius of the second spherical surface, ε1 represents the dielectric constant of air, ε2 represents the dielectric constant of the first optical medium, ε m Represents the dielectric constant of the background medium.

[0030] The beneficial effects of the present invention are as follows: the present invention provides an underwater visible light invisible micro-nano hollow sphere and a design method thereof, wherein the underwater visible light invisible micro-nano hollow sphere comprises a spherical shell and a cavity located inside the spherical shell, the spherical shell is made of glass material or optical coating material, the outer radius of the spherical shell is within the range of 1nm-2μm, and the inner radius, outer radius and dielectric constant of the spherical shell satisfy a preset formula. The underwater visible light invisible micro-nano hollow sphere of the present invention has a simple structure, low manufacturing cost, and can be equipped with micro-nano sensors / detectors, thereby improving the convenience of underwater invisible detection and luring. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A schematic diagram of the structure of an underwater visible light invisible micro-nano hollow sphere provided by an embodiment of the present invention;

[0032] Figure 2 A schematic diagram of an ellipsoid and its spatial coordinate system provided by an embodiment of the present invention;

[0033] Figure 3 A first schematic diagram of the refractive index of a spherical shell material provided by an embodiment of the present invention varying with the size of the inner radius;

[0034] Figure 4 A second schematic diagram of the refractive index of the spherical shell material provided by an embodiment of the present invention varying with the size of the inner radius;

[0035] Figure 5 A third schematic diagram of the variation of the refractive index of the spherical shell material with the size of the inner radius provided by an embodiment of the present invention;

[0036] Figure 6 A fourth schematic diagram of the variation of the refractive index of the spherical shell material with the size of the inner radius provided by an embodiment of the present invention;

[0037] Figure 7 A flowchart of the steps of a method for realizing underwater visible light invisible micro-nano hollow spheres provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0038] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The step numbers in the following embodiments are only provided for the convenience of explanation and description, and the order between the steps is not limited in any way. The execution order of each step in the embodiment can be adaptively adjusted according to the understanding of those skilled in the art.

[0039] In the description of the present invention, the meaning of "a plurality" is more than two. If there is a description of "a first" or "a second", it is only used to distinguish the technical features, and it cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features. In addition, unless otherwise defined, all technical and scientific terms used in this article have the same meaning as those commonly understood by those skilled in the art. The terms used in this specification are only for describing specific embodiments, not for limiting the present invention.

[0040] Reference Figure 1 The embodiment of the present invention provides an underwater visible light invisible micro-nano hollow sphere, comprising a spherical shell 2 and a cavity 1 located inside the spherical shell. The spherical shell 2 is made of glass material or optical coating material. The outer radius of the spherical shell 2 is in the range of 1nm-2μm. The inner radius, outer radius and dielectric constant of the spherical shell 2 satisfy the following formula:

[0041]

[0042] Among them, r1 represents the inner radius of the spherical shell, r2 represents the outer radius of the spherical shell, ε1 represents the dielectric constant of air, ε2 represents the dielectric constant of the spherical shell, and ε m Represents the dielectric constant of the background medium.

[0043] The micro-nano hollow sphere proposed in the embodiment of the present invention is a simple spherical shell structure, and the material used is glass material or conventional optical coating material, etc., so the processing and manufacturing cost is low; the hollow sphere structure can be applied to the design and production of underwater invisible toys; in addition, the cavity inside the structure can also hide micro-nano level detectors / sensors / bait agents, etc., so underwater invisible detection and lure can be achieved. In summary, the underwater visible light invisible micro-nano hollow sphere of the embodiment of the present invention is simple to process, low in manufacturing cost, and has certain application value.

[0044] The stealth principle of the underwater visible light invisible micro-nano hollow sphere according to the embodiment of the present invention is introduced and explained below.

[0045] The entire theoretical analysis in this section is based on the assumption that the radius of the sphere is less than or approximately equal to the wavelength of the light wave. First, establish the coordinate system used to study electromagnetic wave scattering problems. A typical smooth, cornerless, and angular shape is an ellipse, such as Figure 2 shown. Figure 2 The three semi-axes of the ellipse in are a, b, c, and we stipulate that a>b>c. The surface of the ellipsoid is determined by the following equation (1).

[0046]

[0047] In order to describe the polarization problem of ellipsoidal particles under an external electrostatic field with a formula, an ellipsoidal coordinate system (ξ, η, ζ) is required, which is determined by the following formula.

[0048]

[0049] In this formula, ξ=constant represents the confocal ellipsoid, ξ=0 represents the ellipsoid under study, η=constant represents a single-leaf hyperboloid, and ζ=constant represents a double-leaf hyperboloid. Next, on this basis, we will study the electromagnetic wave scattering problem of an ellipsoid with a covering layer. When generalizing the electromagnetic wave scattering problem of an ellipsoid to a multi-layer ellipsoid, there is no need to add additional new concepts. We assume that the three semi-axes of the inner ellipsoid are a1, b1, and c1, and the relative dielectric constant of its medium is ε1. The entire ellipsoid covered by a coating has three semi-axes a2, b2, and c2, and the relative dielectric constant of the covering layer medium is ε2. We call the covering layer of this ellipsoid the outer ellipsoid. The dielectric constant of the background material is ε m, the background is usually air or water. Similar to the previous discussion, the ellipsoid coordinate system (ξ,η,ζ) is introduced:

[0050]

[0051] For η and ζ, there are similar expressions. ξ=0 represents the surface of the inner ellipsoid, ξ=t represents the surface of the outer ellipsoid, where We assume that the external electric field is parallel to the z-axis, and the corresponding potential field is shown in equation (4a):

[0052] Φ0=-E0z=-E0F1(ξ)G(η,ζ)(4a)

[0053] Where:

[0054]

[0055] Assume that the potential fields in the inner ellipsoid and the outer ellipsoid are Φ1 and Φ2 respectively, as shown in equation (5a):

[0056]

[0057] Where:

[0058]

[0059] The potential field Φ3 in the background medium is the sum of Φ0 and Φ p The sum of. Among them, Φ p is the disturbance potential field of the ellipsoidal particle, as shown below:

[0060] Φ p =C4F2(ξ)G(η,ζ) (6)

[0061] According to equations (4a), (5a) and (6), combining Φ and The continuous boundary conditions on each interface of the ellipsoid can obtain four unknown constants C1, C2, C3, and C4, and thus the solution of the scattered field can be obtained. The solution satisfies the polarizability shown in the following equation.

[0062]

[0063] In the formula, v and f are the volumes of the entire ellipsoid including the covering layer, and the internal ellipsoid occupies the volume of the entire ellipsoid. The expression is as follows:

[0064] v=4πa2b2c2 / 3(7b)

[0065] f=a1b1c1 / a2b2c2(7c)

[0066] In the formula and Represent the shape factors of the inner ellipsoid and the outer ellipsoid, respectively, as shown in the following formula:

[0067]

[0068] When ε1 = ε2, equation (7a) is simplified to the polarizability expression of the ellipsoidal particle without a covering layer. When the external electrostatic field vector is along the x or y axis, a similar analysis can be done.

[0069] The above is an analysis of ellipsoidal particles. Applying the above theory to the analysis of spherical particles, let a1=b1=c1=r1, a2=b2=c2=r2, when the following conditions are met:

[0070]

[0071] We can obtain: α1=α2=α3=α and the following expressions.

[0072]

[0073] It can be seen from formula (9) that when the numerator of the formula is equal to 0, the polarizability is equal to 0, which means Φ3 = Φ0. Therefore, this uniform spherical particle with a coating is invisible, that is, it has achieved invisibility. The numerator of formula (9) is equal to 0, which is equivalent to:

[0074]

[0075] Formula (10) is the theoretical basis for designing micro-nano invisible hollow spheres, where

[0076] As a further optional implementation, the spherical shell is made of glass material, the inner radius of the spherical shell is 0.53 μm, and the outer radius of the spherical shell is 1 μm.

[0077] As a further optional implementation, the spherical shell is made of magnesium fluoride optical coating material, the inner radius of the spherical shell is 0.72 μm, and the outer radius of the spherical shell is 1 μm.

[0078] As a further optional implementation, the spherical shell is made of zinc sulfide optical coating material, the inner radius of the spherical shell is 0.92 μm, and the outer radius of the spherical shell is 1 μm.

[0079] The structure of the underwater visible light invisible micro-nano hollow sphere is explained below. Figure 1 As shown, r1 and r2 are the inner radius and outer radius respectively, ε1 = 1 represents the dielectric constant of air, ε m =1.33 2 Represents the dielectric constant of water (background medium).

[0080] According to formula (10), the refractive index of invisible hollow spheres changes with the size of the inner radius. As analyzed above, the present invention studies micro-nano spheres, and the size of the spheres is smaller than or similar to the wavelength of visible light. The wavelength of visible light is about 400-700nm, so the radius of the micro-nano spheres is in the range of 1nm-2μm, and this theory is applicable. Here, we fix r2=1μm and explore the change of the refractive index of the spherical shell material with the size of the inner radius r1, as shown in Figures 3 to 6 As shown, Figure 3 In the case of r1, it is in the range of [0.1, 0.3] μm. Figure 4 In the case of r1, it is in the range of [0.3, 0.6] μm. Figure 5 In the case of r1, it is in the range of [0.6, 0.85] μm. Figure 6 In the figure, r1 is in the range of [0.85, 0.99] μm. When the outer radius is other values, Figures 3 to 6 The specific size of r1 can be changed proportionally according to the calculation result.

[0081] Figure 4 , 5 In Figures 1 and 6, we can see a refractive index point of interest, which are 1.38 for magnesium fluoride, 1.52 for glass, and 2.38 for zinc sulfide. Their corresponding inner radius sizes are 0.53 μm, 0.72 μm, and 0.92 μm, respectively. By selecting these three materials and using the corresponding inner radius size and other parameters, we can prepare underwater micro-nano stealth spherical shells.

[0082] As a further optional embodiment, the spherical shell is prepared by any one of a template method, a self-assembly method, a spray drying method, an emulsion polymerization method, an electrospark-ultrasonic composite processing method, a sol-gel method, and a self-reaction quenching method.

[0083] Specifically, currently commonly used methods for preparing micro-nano hollow spheres include: template method, self-assembly method, spray drying method, emulsion polymerization method, electric spark-ultrasonic composite processing method, sol-gel method, and self-reaction quenching method, etc. Any of the above processes can be used to prepare the underwater visible light invisible micro-nano hollow spheres of the present invention.

[0084] As a further optional embodiment, any one of a micro-nano detector, a micro-nano sensor, a micro-nano monitor, and an acoustic / chemical bait is placed in the cavity.

[0085] Specifically, when preparing such hollow balls, if objects such as micro-nano detectors, sensors, listeners, acoustic / chemical baits are placed in the hollow area, the volume of the objects only occupies a small part of the hollow area, and the surface of the objects is close to transparent, the underwater invisibility of the entire micro-nano system can be achieved. If the spherical shell material has the characteristics of blocking water molecules and transmitting sound waves, radio waves, chemical molecules, etc., the interaction between the internal object and the outside can be achieved, and the tasks of underwater invisible detection, monitoring, and luring can be achieved. In addition, the hollow ball of this structure can also be applied to the design and preparation of underwater invisible toys. A number of such hollow balls can be assembled, or pasted on a transparent toy frame, or pasted on a transparent toy mold (including hollow and solid molds), and underwater invisible toys of various shapes and sizes can be made.

[0086] As a further optional embodiment, the spherical shell has low sound wave reflectivity and high sound wave absorptivity / transmittance.

[0087] Specifically, if the acoustic stealth properties (high sound wave absorption rate or transmittance, low sound wave reflectivity, etc.) are also considered when selecting the material, the micro-nano hollow sphere can achieve simultaneous optical and acoustic stealth.

[0088] It should be noted that the acoustic wave stealth characteristics of the embodiment of the present invention are achieved by selecting suitable materials or adding coatings, but when selecting materials or adding layers, the original visible light stealth characteristics of the present application must be taken into account, that is, they cannot deviate too much from the constraints of the inner radius, outer radius and dielectric constant of the spherical shell specified in the present application.

[0089] Reference Figure 7 The embodiment of the present invention provides a design method for underwater visible light invisible micro-nano hollow spheres, which is implemented by the underwater visible light invisible micro-nano hollow spheres, and includes the following steps:

[0090] S101, constructing a first spherical surface and a second spherical surface of a hollow sphere, wherein the first spherical surface and the second spherical surface have the same spherical center, and the first spherical surface is located inside the second spherical surface, a uniform air medium is distributed inside the first spherical surface, a uniform first optical medium is distributed between the second spherical surface and the first spherical surface, and a uniform background medium is distributed outside the second spherical surface;

[0091] S102, determining a first potential field inside the first spherical surface, a second potential field between the second spherical surface and the first spherical surface, and a third potential field outside the second spherical surface;

[0092] S103, making the first potential field, the second potential field and the third potential field continuous on the first spherical surface and the second spherical surface, and obtaining a polarizability expression of the hollow sphere;

[0093] S104, setting the numerator of the polarizability expression equal to 0, and obtaining a first relationship between the diameter of the first spherical surface, the diameter of the second spherical surface, and the dielectric constant of the first optical medium and the dielectric constant of the air and the dielectric constant of the background medium;

[0094] S105, determining the dielectric constants of the first optical medium and the background medium, and determining the radius of the second spherical surface, and obtaining the radius of the first spherical surface by solving the first relationship;

[0095] S106, using the radius of the first spherical surface as an inner radius and the radius of the second spherical surface as an outer radius to obtain geometric parameters of the spherical shell, and using the first optical medium as a preparation material of the spherical shell.

[0096] As an optional embodiment, the polarizability expression is as follows:

[0097]

[0098] Wherein, α represents the polarizability, r1 represents the radius of the first spherical surface, r2 represents the radius of the second spherical surface, ε1 represents the dielectric constant of air, ε2 represents the dielectric constant of the first optical medium, ε m Represents the dielectric constant of the background medium.

[0099] As an optional implementation, the first relationship is as follows:

[0100]

[0101] Where r1 represents the radius of the first spherical surface, r2 represents the radius of the second spherical surface, ε1 represents the dielectric constant of air, ε2 represents the dielectric constant of the first optical medium, and ε m Represents the dielectric constant of the background medium.

[0102] Specifically, the design method of the underwater visible light invisible micro-nano hollow sphere of the embodiment of the present invention has been described in detail in the previous stealth principle part. The only difference is that the ellipsoid is replaced by a sphere, the three semi-axes of the inner ellipsoid are replaced by the radius of the first spherical surface, and the three semi-axes of the outer dragged sphere are replaced by the radius of the second spherical surface, that is, a1=b1=c1=r1, a2=b2=c2=r2 are set, and the polarizability expression and the first relationship can be obtained. Then, the dielectric constants of the first optical medium and the background medium are determined, and the radius of the second spherical surface is determined. The radius of the first spherical surface is solved according to the first relationship, and the radius of the first spherical surface is used as the inner radius and the radius of the second spherical surface is used as the outer radius to obtain the geometric parameters of the spherical shell, and the first optical medium is used as the preparation material of the spherical shell.

[0103] Micro-nano hollow spheres have the characteristics of low density and high specific surface area, and they show unique properties in many aspects such as acoustics, optics and electricity, and have broad application prospects. However, there are few studies on micro-nano hollow spheres in the field of stealth.

[0104] The design method of underwater invisible micro-nano hollow spheres proposed in the present invention has a simple calculation process and high precision. The method can provide an analytical solution to the refractive index and geometric parameters of the hollow sphere, thereby achieving perfect optical invisibility. The materials used in the present invention are glass materials or conventional optical coating materials, etc., so the processing and manufacturing costs are low; the hollow sphere structure can be applied to the design and manufacture of underwater invisible toys; in addition, micro-nano-level detectors / sensors / bait agents, etc. can also be hidden in the cavity inside the structure, so underwater invisible detection and lure can be achieved. In summary, the underwater visible light invisible micro-nano hollow spheres of the embodiments of the present invention are simple to process, low in manufacturing cost, and have certain application value.

[0105] The above is a description of the underwater visible light invisible micro-nano hollow sphere and its design method according to an embodiment of the present invention. It can be appreciated that the underwater visible light invisible micro-nano hollow sphere of the present invention has a simple structure, low manufacturing cost, and can be equipped with micro-nano sensors / detectors, thereby improving the convenience of underwater invisible detection and luring.

[0106] The above is only a preferred embodiment of the present invention. The present invention is not limited to the above implementation. As long as the technical effect of the present invention is achieved by the same means, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of protection of the present invention. Within the scope of protection of the present invention, its technical scheme and / or implementation method may have various modifications and changes.

Claims

1. An underwater visible light invisible micro-nano hollow sphere, characterized in that: The invention comprises a spherical shell and a cavity inside the spherical shell, wherein the spherical shell is made of glass material or optical coating material, the outer radius of the spherical shell is in the range of 1 nm-2 μm, and the inner radius, outer radius and dielectric constant of the spherical shell satisfy the following formula: Wherein, r1 represents the inner radius of the spherical shell, r2 represents the outer radius of the spherical shell, ε1 represents the dielectric constant of air, ε2 represents the dielectric constant of the spherical shell, ε m Represents the dielectric constant of the background medium.

2. The underwater visible light invisible micro-nano hollow sphere according to claim 1, characterized in that: The spherical shell is made of glass material, the inner radius of the spherical shell is 0.53 μm, and the outer radius of the spherical shell is 1 μm.

3. The underwater visible light invisible micro-nano hollow sphere according to claim 1, characterized in that: The spherical shell is made of magnesium fluoride optical coating material, the inner radius of the spherical shell is 0.72 μm, and the outer radius of the spherical shell is 1 μm.

4. The underwater visible light invisible micro-nano hollow sphere according to claim 1, characterized in that: The spherical shell is made of zinc sulfide optical coating material, the inner radius of the spherical shell is 0.92 μm, and the outer radius of the spherical shell is 1 μm.

5. The underwater visible light invisible micro-nano hollow sphere according to claim 1, characterized in that: The spherical shell is prepared by any one of a template method, a self-assembly method, a spray drying method, an emulsion polymerization method, an electric spark-ultrasonic composite processing method, a sol-gel method and a self-reaction quenching method.

6. The underwater visible light invisible micro-nano hollow sphere according to claim 1, characterized in that: Any one of a micro-nano detector, a micro-nano sensor, a micro-nano monitor and an acoustic / chemical bait is placed in the cavity.

7. The underwater visible light invisible micro-nano hollow sphere according to claim 1, characterized in that: The spherical shell has low sound wave reflectivity and high sound wave absorptivity / transmittance.

8. A method for designing an underwater visible light invisible micro-nano hollow sphere according to any one of claims 1 to 7, characterized in that: include: Constructing a first spherical surface and a second spherical surface of a hollow sphere, wherein the first spherical surface and the second spherical surface have the same spherical center, and the first spherical surface is located inside the second spherical surface, a uniform air medium is distributed inside the first spherical surface, a uniform first optical medium is distributed between the second spherical surface and the first spherical surface, and a uniform background medium is distributed outside the second spherical surface; Determine a first potential field inside the first spherical surface, a second potential field between the second spherical surface and the first spherical surface, and a third potential field outside the second spherical surface; The first potential field, the second potential field and the third potential field are set to be continuous on the first spherical surface and the second spherical surface, and the polarizability expression of the hollow sphere is obtained; Setting the numerator of the polarizability expression equal to 0, obtaining a first relationship between the diameter of the first spherical surface, the diameter of the second spherical surface, and the dielectric constant of the first optical medium, the dielectric constant of air, and the dielectric constant of the background medium; Determine the dielectric constants of the first optical medium and the background medium, and determine the radius of the second spherical surface, and obtain the radius of the first spherical surface by solving the first relationship; The radius of the first spherical surface is used as an inner radius and the radius of the second spherical surface is used as an outer radius to obtain geometric parameters of a spherical shell, and the first optical medium is used as a preparation material of the spherical shell.

9. The design method of underwater visible light invisible micro-nano hollow sphere according to claim 8, characterized in that: The polarizability expression is as follows: Wherein, α represents the polarizability, r1 represents the radius of the first spherical surface, r2 represents the radius of the second spherical surface, ε1 represents the dielectric constant of air, ε2 represents the dielectric constant of the first optical medium, ε m Represents the dielectric constant of the background medium.

10. The design method of underwater visible light invisible micro-nano hollow sphere according to claim 8, characterized in that: The first relationship is as follows: Wherein, r1 represents the radius of the first spherical surface, r2 represents the radius of the second spherical surface, ε1 represents the dielectric constant of air, ε2 represents the dielectric constant of the first optical medium, ε m Represents the dielectric constant of the background medium.

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