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

Abstract

The application discloses an underwater visible light stealth micro-nano hollow sphere and a design method thereof. The underwater visible light stealth micro-nano hollow sphere comprises a spherical shell and a cavity in the spherical shell. 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 to 2 microns. The inner radius, the outer radius and the dielectric constant of the spherical shell satisfy a preset formula. The application has the advantages of simple structure, low manufacturing cost, and can carry micro-nano sensors / detectors, improves the convenience of underwater stealth detection and luring, and can be widely applied to the technical field of underwater detection.

Description

Technical Field

[0001] This invention relates to the field of underwater detection technology, and in particular to an underwater visible light stealth micro / nano hollow sphere and its design method. Background Technology

[0002] Visible light stealth or invisibility technology has a wide range of applications in military stealth, fun stealth toys, and aesthetic stealth design. Generally, visible light stealth is divided into active and passive stealth. Active stealth relies on a light-emitting layer that actively emits light close to the background light to conceal itself. Passive stealth includes electromagnetic wave absorbing layers, metamaterials, complex geometric structures, coatings that match the surrounding environment, camouflage layers, and complex fiber optic / waveguide structures. Besides visible light stealth, underwater stealth often requires acoustic stealth. Acoustic stealth mainly employs three methods: ① using new materials such as fiberglass, synthetic rubber, and reinforced plastics; ② coating the object's surface with a sound-absorbing coating; ③ utilizing new materials with high sound transmission properties to allow most of the sound waves emitted by sonar to penetrate the object.

[0003] While some stealth solutions for large-sized objects have been proposed in related technologies, they cannot be applied to the micro-nano field. However, research on micro-nano sensors and detectors is currently very active, necessitating the design of micro-nano stealth spherical shells to conceal these sensors / detectors. Therefore, research on micro-nano scale optical stealth spherical shells is extremely important.

[0004] A micro-nano optical stealth structure based on butterfly wing biomimetic technology has also been proposed in related technologies. However, this structure is complex to manufacture, only suitable for stealth in the air, and cannot hide objects inside the structure to achieve stealth. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide an underwater visible light stealth micro / nano hollow sphere and its design method. This underwater visible light stealth micro / nano hollow sphere has a simple structure, low manufacturing cost, and can be equipped with micro / nano sensors / detectors, thereby improving the convenience of underwater stealth detection and attraction.

[0006] The first technical solution adopted in this invention is:

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

[0008]

[0009] Where 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 This represents the dielectric constant of the background medium.

[0010] Furthermore, the spherical shell is made of glass material, with an inner radius of 0.53 μm and an outer radius of 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 the following methods: template method, self-assembly method, spray drying method, emulsion polymerization method, electrical discharge-ultrasound composite processing method, sol-gel method, and self-reaction quenching method.

[0014] Furthermore, the spherical shell is prepared by any one of the following methods: template method, self-assembly method, spray drying method, emulsion polymerization method, electrical discharge-ultrasound composite processing method, sol-gel method, and self-reaction quenching method.

[0015] Furthermore, the spherical shell has low acoustic reflectivity and high acoustic absorption / transmittance.

[0016] The second technical solution adopted in this invention is:

[0017] A design method for underwater visible light stealth micro / nano hollow spheres includes the following steps:

[0018] Construct a first spherical surface and a second spherical surface of a hollow sphere. The first spherical surface and the second spherical surface have the same 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 the first potential field inside the first sphere, the second potential field between the second sphere and the first sphere, and the third potential field outside the second sphere;

[0020] By making the first potential field, the second potential field, and the third potential field continuous on the first sphere and the second sphere, the polarizability expression of the hollow sphere is obtained.

[0021] Setting the numerator of the polarizability expression to 0, we obtain the diameter of the first sphere, the diameter of the second sphere, and the first relationship between the dielectric constant of the first optical medium and 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 sphere. Solve for the radius of the first sphere according to the first relationship.

[0023] The geometric parameters of the spherical shell are obtained by taking the radius of the first sphere as the inner radius and the radius of the second sphere as the outer radius, and the first optical medium is used as the material for preparing the spherical shell.

[0024] Furthermore, the expression for the polarizability is as follows:

[0025]

[0026] Where α represents polarizability, r1 represents the radius of the first sphere, r2 represents the radius of the second sphere, ε1 represents the dielectric constant of air, ε2 represents the dielectric constant of the first optical medium, and ε m This represents the dielectric constant of the background medium.

[0027] Furthermore, the first relation is as follows:

[0028]

[0029] Where r1 represents the radius of the first sphere, r2 represents the radius of the second sphere, ε1 represents the dielectric constant of air, ε2 represents the dielectric constant of the first optical medium, and ε m This represents the dielectric constant of the background medium.

[0030] The beneficial effects of this invention are as follows: This invention provides an underwater visible-light stealth micro / nano hollow sphere and its design method. The underwater visible-light stealth micro / nano hollow sphere includes a spherical shell and a cavity located inside the spherical shell. The spherical shell is made of glass or optical coating material, and its outer radius is within the range of 1 nm-2 μm. The inner radius, outer radius, and dielectric constant of the spherical shell satisfy a preset formula. The underwater visible-light stealth micro / nano hollow sphere of this invention has a simple structure, low manufacturing cost, and can be equipped with micro / nano sensors / detectors, improving the convenience of underwater stealth detection and attraction. Attached Figure Description

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

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

[0033] Figure 3 This is a first schematic diagram illustrating the change of the refractive index of a spherical shell material with its inner radius, provided in an embodiment of the present invention.

[0034] Figure 4 This is a second schematic diagram illustrating the variation of the refractive index of a spherical shell material with its inner radius, provided in an embodiment of the present invention.

[0035] Figure 5 This is a third schematic diagram illustrating the variation of the refractive index of a spherical shell material with its inner radius, provided in an embodiment of the present invention.

[0036] Figure 6 This is a fourth schematic diagram illustrating the variation of the refractive index of a spherical shell material with its inner radius, provided in an embodiment of the present invention.

[0037] Figure 7 This is a flowchart illustrating the steps of a method for realizing an underwater visible light stealth micro / nano hollow sphere, as provided in an embodiment of the present invention. Detailed Implementation

[0038] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The step numbers in the following embodiments are only for ease of explanation and do not limit the order of the steps. The execution order of each step in the embodiments can be adapted according to the understanding of those skilled in the art.

[0039] In the description of this invention, "multiple" means two or more. The use of "first" and "second" is for distinguishing technical features only and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or the order in which the indicated technical features are presented. Furthermore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this specification is for the purpose of describing particular embodiments only and not for limiting the invention.

[0040] Reference Figure 1 This invention provides an underwater visible light stealth 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 or optical coating material, and its outer radius is in the range of 1 nm-2 μm. The inner radius, outer radius, and dielectric constant of the spherical shell 2 satisfy the following formula:

[0041]

[0042] Where 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 This represents the dielectric constant of the background medium.

[0043] The micro / nano hollow sphere proposed in this invention is a simple spherical shell structure made of glass or conventional optical coating materials, resulting in low manufacturing costs. This hollow sphere structure can be applied to the design and fabrication of underwater stealth toys. Furthermore, the internal cavity of this structure can conceal micro / nano-level detectors / sensors / decoys, thus enabling underwater stealth detection and attraction. In summary, the underwater visible-light stealth micro / nano hollow sphere of this invention is simple to fabricate, has low manufacturing costs, and possesses certain application value.

[0044] The stealth principle of the underwater visible light stealth micro-nano hollow sphere according to an embodiment of the present invention will be described below.

[0045] The entire theoretical analysis in this section is based on the premise that the radius of the sphere is less than or approximately equal to the wavelength of light. First, a coordinate system is established for studying electromagnetic wave scattering. A typical smooth shape, without sharp edges or corners, is an ellipse, such as... Figure 2 As shown. Figure 2 The three semi-axes of the ellipse in the figure are a, b, and c, and we stipulate that a > b > c. The surface of the elliptic is determined by the following equation (1).

[0046]

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

[0048]

[0049] In this formula, ξ = constant represents a confocal ellipsoid, ξ = 0 represents the ellipsoid under study, η = constant represents a hyperboloid of one leaf, and ζ = constant represents a hyperboloid of two leaves. Below, we study the electromagnetic wave scattering problem of an ellipsoid with a covering layer. Extending the electromagnetic wave scattering problem of an ellipsoid to a multilayer ellipsoid does not require adding any new concepts. We assume that the inner ellipsoid has three semi-axes a1, b1, c1, and its medium has a relative permittivity of ε1. The entire ellipsoid covered by a coating has three semi-axes a2, b2, c2, and the covering layer medium has a relative permittivity of ε2. We call this covering layer the outer ellipsoid. The permittivity of the background material is ε. mThe background is typically air or water. Similar to the previous discussion, we introduce an ellipsoidal coordinate system (ξ, η, ζ):

[0050]

[0051] For η and ζ, there are similar expressions. ξ = 0 represents the surface of the inner ellipsoid, and 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] In the formula:

[0054]

[0055] Assume the potential fields in the inner and outer ellipsoids are Φ1 and Φ2, respectively, as shown in the system of equations (5a):

[0056]

[0057] In the formula:

[0058]

[0059] The potential field Φ3 in the background medium is Φ0 and Φ p The sum. Where Φ p It is the perturbation potential field of the ellipsoidal particle, as shown in the following equation:

[0060] Φ p =C4F2(ξ)G(η,ζ) (6)

[0061] Based on equations (4a), (5a) and (6), combined with Φ and By applying continuous boundary conditions at each interface of the ellipsoid, four unknown constants C1, C2, C3, and C4 can be obtained, thus yielding a solution for the scattered field. This solution satisfies the polarizability shown in the following equation.

[0062]

[0063] In the formula, v and f represent the volumes of the entire ellipsoid including the overlying layer, and the inner 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 These represent the shape factors of the inner and outer ellipsoids, respectively, as shown in the following formula:

[0067]

[0068] When ε1 = ε2, equation (7a) simplifies to the polarizability expression for ellipsoidal particles without an overlay. A similar analysis can be performed when the external electrostatic field vector is along the x or y axis.

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

[0070]

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

[0072]

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

[0074]

[0075] Equation (10) is the theoretical basis for designing micro / nano stealth hollow spheres, in which...

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

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

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

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

[0080] The refractive index of the invisible hollow sphere is studied according to equation (10) as a function of its inner radius. As analyzed above, this invention studies micro- and nano-spheres, whose scale is smaller than or close to the wavelength of visible light. The wavelength of visible light is approximately 400-700 nm, so the theory applies to micro- and nano-spheres whose radii are in the range of 1 nm-2 μm. Here, we fix r2 = 1 μm and explore the variation of the refractive index of the spherical shell material with the inner radius r1, such as... Figures 3 to 6 As shown, Figure 3 r1 is located in the range [0.1, 0.3] μm. Figure 4 r1 is located in the range [0.3, 0.6] μm. Figure 5 r1 is located in the range [0.6, 0.85] μm. Figure 6 The radius r1 is within the range of [0.85, 0.99] μm. When the outer radius is other values, it follows... Figures 3 to 6 The specific size of r1 can be changed proportionally based on the calculation results.

[0081] Figure 4 , 5 Figures 6 and 7 respectively mark a refractive index point of interest: magnesium fluoride (1.38), glass (1.52), and zinc sulfide (2.38). Their corresponding inner radii are 0.53 μm, 0.72 μm, and 0.92 μm, respectively. By selecting these three materials and using their corresponding inner radius and other parameters, underwater micro / nano stealth spherical shells can be fabricated.

[0082] As an optional implementation, the spherical shell is prepared by any one of the following methods: template method, self-assembly method, spray drying method, emulsion polymerization method, electrical discharge-ultrasound composite processing method, sol-gel method, and self-reaction quenching method.

[0083] Specifically, commonly used methods for preparing micro / nano hollow spheres include: template method, self-assembly method, spray drying method, emulsion polymerization method, electrical discharge-ultrasound 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 stealth micro / nano hollow spheres of this invention.

[0084] As a further optional implementation, the cavity may contain any one of a micro / nano detector, a micro / nano sensor, a micro / nano listener, and an acoustic / chemical decoy.

[0085] Specifically, when fabricating these hollow spheres, if micro / nano detectors, sensors, listening devices, acoustic / chemical decoys, etc., are placed within the hollow area, and the objects occupy only a small portion of the hollow area with nearly transparent surfaces, underwater stealth of the entire micro / nano system can be achieved. If the shell material has the properties of blocking water molecules while allowing sound waves, radio waves, and chemical molecules to pass through, interaction between the internal objects and the external environment can be achieved, enabling underwater stealth detection, listening, and decoy tasks. In addition, this type of hollow sphere can also be applied to the design and fabrication of underwater stealth toys. By assembling several of these hollow spheres, attaching them to a transparent toy frame, or attaching them to a transparent toy mold (including hollow and solid molds), underwater stealth toys of various shapes and sizes can be created.

[0086] As an optional further implementation, the spherical shell has low acoustic reflectivity and high acoustic absorption / transmittance.

[0087] Specifically, if acoustic stealth characteristics (high acoustic absorption or transmittance, low acoustic reflectivity, etc.) are also considered when selecting materials, then the micro-nano hollow sphere can achieve both optical and acoustic stealth.

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

[0089] Reference Figure 7 This invention provides a design method for underwater visible light stealth micro / nano hollow spheres, which is used to achieve underwater visible light stealth micro / nano hollow spheres as described above, and includes the following steps:

[0090] S101. Construct a first spherical surface and a second spherical surface of a hollow sphere. The centers of the first spherical surface and the second spherical surface are the same, 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. Determine the first potential field inside the first sphere, the second potential field between the second sphere and the first sphere, and the third potential field outside the second sphere.

[0092] S103. Make the first potential field, the second potential field and the third potential field continuous on the first sphere and the second sphere to obtain the polarizability expression of the hollow sphere.

[0093] S104. Set the numerator of the polarizability expression to 0 to obtain the diameter of the first sphere, the diameter of the second sphere, and the first relationship between the dielectric constant of the first optical medium and the dielectric constant of air and the dielectric constant of the background medium.

[0094] S105. Determine the dielectric constants of the first optical medium and the background medium, and determine the radius of the second sphere. Solve for the radius of the first sphere according to the first relational formula.

[0095] S106. The geometric parameters of the spherical shell are obtained by taking the radius of the first sphere as the inner radius and the radius of the second sphere as the outer radius, and the first optical medium is used as the material for preparing the spherical shell.

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

[0097]

[0098] Where α represents polarizability, r1 represents the radius of the first sphere, r2 represents the radius of the second sphere, ε1 represents the dielectric constant of air, ε2 represents the dielectric constant of the first optical medium, and ε m This represents the dielectric constant of the background medium.

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

[0100]

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

[0102] Specifically, the design method of the underwater visible light stealth micro / nano hollow sphere of this invention has been described in detail in the previous stealth principle section. The only difference is that the ellipsoid is replaced with a sphere, the radius of the first sphere is used to replace the three semi-axes of the inner ellipsoid, and the radius of the second sphere is used to replace the three semi-axes of the outer spherical sphere. That is, let a1 = b1 = c1 = r1, a2 = b2 = c2 = r2, then the polarizability expression and the first relation can be obtained. Then the dielectric constants of the first optical medium and the background medium are determined, and the radius of the second sphere is determined. The radius of the first sphere is obtained by solving according to the first relation. The radius of the first sphere is used as the inner radius and the radius of the second sphere is used as the outer radius to obtain the geometric parameters of the spherical shell, and the first optical medium is used as the material for preparing the spherical shell.

[0103] Micro- and nano-hollow spheres possess characteristics such as low density and high specific surface area, exhibiting unique properties in many fields including acoustics, optics, and electronics, and have broad application prospects. However, research on the application of micro- and nano-hollow spheres in the field of stealth is limited.

[0104] The design method for underwater stealth micro / nano hollow spheres proposed in this invention features a simple calculation process and high accuracy. This method can provide analytical solutions for the refractive index and geometric parameters of the hollow sphere, achieving perfect optical cloaking. The materials used in this invention are glass or conventional optical coating materials, resulting in low manufacturing costs. This hollow sphere structure can be applied to the design and fabrication of underwater stealth toys. Furthermore, the internal cavity of this structure can conceal micro / nano-level detectors / sensors / decoys, thus enabling underwater stealth detection and attraction. In summary, the underwater visible light stealth micro / nano hollow spheres of this invention are simple to fabricate, have low manufacturing costs, and possess certain application value.

[0105] The above describes the underwater visible light stealth micro-nano hollow sphere and its design method according to embodiments of the present invention. It can be understood that the underwater visible light stealth micro-nano hollow sphere of the present invention has a simple structure, low manufacturing cost, and can be equipped with micro-nano sensors / detectors, which improves the convenience of underwater stealth detection and attraction.

[0106] The above description is merely a preferred embodiment of the present invention. The present invention is not limited to the above-described embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention, as long as they achieve the technical effects of the present invention by the same means, should be included within the scope of protection of the present invention. Within the scope of protection of the present invention, the technical solutions and / or implementation methods can have various modifications and variations.

Claims

1. An underwater visible light stealth micro / nano hollow sphere, characterized in that, The device includes a spherical shell and a cavity inside the spherical shell. The spherical shell is made of glass or an optically coated material. The cavity houses any one of the following: a micro / nano detector, a micro / nano sensor, a micro / nano listener, and an acoustic / chemical decoy. The outer radius of the spherical shell is in the range of 1 nm to 2 μm. The inner radius, outer radius, and dielectric constant of the spherical shell satisfy the following equation: in, This represents the inner radius of the spherical shell. This represents the outer radius of the spherical shell. The dielectric constant of air. This represents the dielectric constant of the spherical shell. Indicates the dielectric constant of the background medium; The geometric parameters of the spherical shell are determined through the following steps: Construct a first spherical surface and a second spherical surface of a hollow sphere. The first spherical surface and the second spherical surface have the same 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 the first potential field inside the first sphere, the second potential field between the second sphere and the first sphere, and the third potential field outside the second sphere; By making the first potential field, the second potential field, and the third potential field continuous on the first sphere and the second sphere, the polarizability expression of the hollow sphere is obtained. Setting the numerator of the polarizability expression to 0, we obtain the diameter of the first sphere, the diameter of the second sphere, and the first relationship between the dielectric constant of the first optical medium and 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 sphere. Solve for the radius of the first sphere according to the first relationship. The geometric parameters of the spherical shell are obtained by taking the radius of the first sphere as the inner radius and the radius of the second sphere as the outer radius, and the first optical medium is used as the material for preparing the spherical shell.

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

3. The underwater visible light stealth 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 stealth 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 stealth micro / nano hollow sphere according to claim 1, characterized in that: The spherical shell is prepared by any one of the following methods: template method, self-assembly method, spray drying method, emulsion polymerization method, electrical discharge-ultrasound composite processing method, sol-gel method, and self-reaction quenching method.

6. The underwater visible light stealth micro / nano hollow sphere according to claim 1, characterized in that: The spherical shell has low acoustic reflectivity and high acoustic absorption / transmittance.

7. A design method for an underwater visible light stealth micro / nano hollow sphere as described in any one of claims 1 to 6, characterized in that, include: Construct a first spherical surface and a second spherical surface of a hollow sphere. The first spherical surface and the second spherical surface have the same 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 the first potential field inside the first sphere, the second potential field between the second sphere and the first sphere, and the third potential field outside the second sphere; By making the first potential field, the second potential field, and the third potential field continuous on the first sphere and the second sphere, the polarizability expression of the hollow sphere is obtained. Setting the numerator of the polarizability expression to 0, we obtain the diameter of the first sphere, the diameter of the second sphere, and the first relationship between the dielectric constant of the first optical medium and 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 sphere. Solve for the radius of the first sphere according to the first relationship. The geometric parameters of the spherical shell are obtained by taking the radius of the first sphere as the inner radius and the radius of the second sphere as the outer radius, and the first optical medium is used as the material for preparing the spherical shell.

8. The design method of an underwater visible light stealth micro / nano hollow sphere according to claim 7, characterized in that, The polarizability expression is as follows: in, Indicates polarizability, This represents the radius of the first sphere. This represents the radius of the second sphere. The dielectric constant of air. This represents the dielectric constant of the first optical medium. This represents the dielectric constant of the background medium.

9. The design method of an underwater visible light stealth micro / nano hollow sphere according to claim 7, characterized in that, The first relation is as follows: in, This represents the radius of the first sphere. This represents the radius of the second sphere. The dielectric constant of air. This represents the dielectric constant of the first optical medium. This represents the dielectric constant of the background medium.

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