A broadband focusing flexible metalens and its uses

Abstract

The present invention relates to a broadband focusing flexible superlens and its uses, including a housing and a discrete flexible composite layer. The housing is a straight cylindrical structure; the first discrete flexible composite layer is a cylindrical structure and is arranged at the central position of the housing. The second discrete flexible composite layer, the third discrete flexible composite layer, the fourth discrete flexible composite layer, the fifth discrete flexible composite layer, and the sixth discrete flexible composite layer are annular cylindrical structures and are sequentially connected starting from the side wall of the first discrete flexible composite layer; the discrete flexible composite layer includes a base layer made of a flexible silicone elastomer, and micron tungsten particles doped in the base layer. The discrete flexible composite layer is uniformly mixed by the flexible silicone elastomer and the micron tungsten particles according to different mass percentages.

Description

Technical Field

[0001] The present invention relates to the field of flexible superlenses, and specifically refers to a flexible superlens with broadband focusing and its uses. Background Art

[0002] In the field of biomedical ultrasound, sound needs to be transmitted through phase difference layers such as human tissues or bones (such as the skull), aiming to pursue the maximum transmitted sound energy and the minimum reflected sound energy. Impedance matching technology can achieve the purpose that all signals can be transmitted to the load point, and almost no signal is reflected back to the source point, thereby improving energy efficiency. It has been widely used in electrical, mechanical, acoustic, optical, and microwave engineering.

[0003] However, materials such as human tissues or the skull can be regarded as phase difference layers. When sound waves pass through, they will interact with the phase difference layers, resulting in phase changes and thus distortions. For example, the acoustic impedance of the human skull is 3.6 times higher than that of tissues, and there are problems of energy attenuation and impedance mismatch, resulting in an energy attenuation of up to 32%. Due to the mismatch between the phase difference layer and human tissues, the strategy of guiding sound to transmit inside tissues has encountered fundamental challenges.

[0004] Designing a flexible superlens with broadband focusing and its uses to address the problems existing in the above-mentioned prior art is the purpose of the research of the present invention. Summary of the Invention

[0005] Aiming at the problems existing in the above-mentioned prior art, the present invention provides a flexible superlens with broadband focusing and its uses, which can effectively solve the problems existing in the above-mentioned prior art.

[0006] The technical solution of the present invention is as follows:

[0007] A flexible superlens with broadband focusing, comprising a housing and a discrete flexible composite layer, wherein the housing is in a straight cylindrical structure;

[0008] The discrete flexible composite layer includes a first discrete flexible composite layer, a second discrete flexible composite layer, a third discrete flexible composite layer, a fourth discrete flexible composite layer, a fifth discrete flexible composite layer, and a sixth discrete flexible composite layer. The first discrete flexible composite layer is in a cylindrical structure and is arranged at the central position of the housing. The second discrete flexible composite layer, the third discrete flexible composite layer, the fourth discrete flexible composite layer, the fifth discrete flexible composite layer, and the sixth discrete flexible composite layer are in an annular cylindrical structure and are sequentially connected starting from the side wall of the first discrete flexible composite layer;

[0009] The discrete flexible composite layer includes a base layer made of a flexible silicone elastomer and micron tungsten particles doped in the base layer. The discrete flexible composite layer is uniformly mixed by the flexible silicone elastomer and the micron tungsten particles according to different mass percentages.

[0010] Further, the acoustic refractive indices n of the first discrete flexible composite layer, the second discrete flexible composite layer, the third discrete flexible composite layer, the fourth discrete flexible composite layer, the fifth discrete flexible composite layer, and the sixth discrete flexible composite layer satisfy Equation 1:

[0011]

[0012] where y s is the thickness of the flexible hyperlens, y a is the thickness of the phase difference layer, is the refractive index of the phase difference layer, n0 is the refractive index of the background medium, d is the distance from the focus of the flexible hyperlens to the outer surface of the flexible hyperlens, and x is the horizontal axis coordinate.

[0013] Further, the mass percentages of the flexible silicone elastomer and the micron tungsten particles in the first discrete flexible composite layer, the second discrete flexible composite layer, the third discrete flexible composite layer, the fourth discrete flexible composite layer, the fifth discrete flexible composite layer, and the sixth discrete flexible composite layer are obtained according to the equivalent medium theory, and the mass percentages of the flexible silicone elastomer and the micron tungsten particles satisfy Equation 2:

[0014]

[0015] where φ m represents the mass percentage of the flexible silicone elastomer and the micron tungsten particles, is the volume fraction of the composite of the flexible silicone elastomer and the micron tungsten particles, ρ1 represents the mass density of the silicone elastomer, and ρ2 represents the mass density of the micron tungsten particles;

[0016] so that the acoustic refractive index satisfies the Equation 1.

[0017] Further, the radii corresponding to the outer walls of the first discrete flexible composite layer, the second discrete flexible composite layer, the third discrete flexible composite layer, the fourth discrete flexible composite layer, the fifth discrete flexible composite layer, and the sixth discrete flexible composite layer are 20.2 - 20.3 mm, 34.0 - 34.1 mm, 42.7 - 42.8 mm, 49.1 - 49.2 mm, 54.1 - 54.2 mm, and 59.95 - 60.05 mm, respectively.

[0018] Furthermore, the outer wall corresponding radii of the first discrete flexible composite layer, the second discrete flexible composite layer, the third discrete flexible composite layer, the fourth discrete flexible composite layer, the fifth discrete flexible composite layer, and the sixth discrete flexible composite layer are 20.241 mm, 34.078 mm, 42.732 mm, 49.129 mm, 54.148 mm, and 60 mm respectively.

[0019] Furthermore, the base layers of the first discrete flexible composite layer and the second discrete flexible composite layer are both formed by mixing A glue and B glue of Ecoflex 00-30 in a ratio of 1:1; and / or,

[0020] The base layers of the third discrete flexible composite layer, the fourth discrete flexible composite layer, the fifth discrete flexible composite layer, and the sixth discrete flexible composite layer are all formed by mixing A glue, B glue, and diluent of Ecoflex 00-30 in a ratio of 1:1:1.

[0021] Furthermore, the background medium is water.

[0022] Furthermore, the discrete flexible composite layer is made by doping micron tungsten particles with a corresponding mass fraction into the flexible silicone elastomer as raw materials and introducing them into a mold printed by 3D.

[0023] Furthermore, a use of a broadband focusing flexible hyperlens is provided, which is used to focus acoustic energy inside human tissues or bones, or to transmit acoustic energy through a phase difference layer.

[0024] Therefore, the present invention provides the following effects and / or advantages:

[0025] This application includes six discrete flexible composite layers distributed radially. The discrete flexible composite layer is formed by uniformly mixing a flexible silicone elastomer and micron tungsten particles according to different mass percentages. The mass percentages of the flexible silicone elastomer and micron tungsten particles are designed by the equivalent medium theory. The two-dimensional flexible material formed by the non-uniform distribution along the radial direction of the hyperlens can achieve ultrasonic focusing. The gradient distribution along the radial direction and the uniform distribution along the axial direction enable it to have the ability of broadband transmission and have focusing characteristics.

[0026] This application is designed by soft material - metamaterial - transformation acoustics, and is simple to manufacture, easy to mass-produce and process.

[0027] When the flexible hyperlens is applied, this application can increase the sound pressure by four times and improve the average spatial resolution to 11.69 times. It can receive higher-intensity signals, so it can be applied to medical ultrasonic equipment to achieve focusing of acoustic energy inside human tissues or bones, or to transmit acoustic energy through a phase difference layer.

[0028] It should be understood that the foregoing summary and the following detailed description of the present invention are exemplary and explanatory, and are intended to provide further explanation of the present invention as claimed. Description of the Drawings

[0029] Figure 1 Schematic structural diagram of an embodiment provided for the present invention.

[0030] Figure 2 Schematic diagram of the dimensions of an embodiment provided for the present invention.

[0031] Figure 3 Schematic diagram of the dimensions of an embodiment provided for the present invention.

[0032] Figure 4 Is the finite element calculation result of the ultrasonic focusing performance of the present invention.

[0033] Figure 5 Experimental schematic diagram of experimental measurement of ultrasonic broadband focusing.

[0034] Figure 6 Are the experimental measurement and simulation calculation results of broadband ultrasonic focusing of the present invention. Detailed Description of the Invention

[0035] For the convenience of those skilled in the art to understand, the structure of the present invention will now be further described in detail with reference to the accompanying drawings: First. For an ultrasonic transducer with a center frequency of 120 kHz, the diameter of the radiation surface of the transducer is 120 mm.

[0036] Reference Figure 1 -3, a broadband focusing flexible superlens, comprising a housing 1 and a discrete flexible composite layer 2, the housing 1 being a straight cylindrical structure;

[0037] In this embodiment, the housing 1 is a straight cylindrical hollow structure, through which the discrete flexible composite layer 2 can be used to be accommodated, and the discrete flexible composite layer 2 of this embodiment is completely filled and accommodated inside the housing 1.

[0038] The discrete flexible composite layer 2 includes a first discrete flexible composite layer 201, a second discrete flexible composite layer 202, a third discrete flexible composite layer 203, a fourth discrete flexible composite layer 204, a fifth discrete flexible composite layer 205, and a sixth discrete flexible composite layer 206. The first discrete flexible composite layer 201 is a cylindrical structure and is arranged at the central position of the housing 1. The second discrete flexible composite layer 202, the third discrete flexible composite layer 203, the fourth discrete flexible composite layer 204, the fifth discrete flexible composite layer 205, and the sixth discrete flexible composite layer 205 are annular cylindrical structures and are sequentially connected starting from the side wall of the first discrete flexible composite layer 201;

[0039] The first discrete flexible composite layer 201, the second discrete flexible composite layer 202, the third discrete flexible composite layer 203, the fourth discrete flexible composite layer 204, the fifth discrete flexible composite layer 205, and the sixth discrete flexible composite layer 206 of this embodiment are all arranged concentrically, and the centers of the first discrete flexible composite layer 201, the second discrete flexible composite layer 202, the third discrete flexible composite layer 203, the fourth discrete flexible composite layer 204, the fifth discrete flexible composite layer 205, and the sixth discrete flexible composite layer 206 coincide with the center of the housing 1, thereby forming a structure with multiple concentric circles arranged successively outward in cross-section, which can also be described as six discrete flexible composite layers distributed radially.

[0040] The discrete flexible composite layer 2 includes a base layer made of a flexible silicone elastomer and micron tungsten particles doped in the base layer, and the discrete flexible composite layer 2 is uniformly mixed by the flexible silicone elastomer and the micron tungsten particles according to different mass percentages.

[0041] The two-dimensional flexible material formed by the non-uniform distribution along the radial direction of the metalens in this embodiment can achieve ultrasonic focusing, and its gradient distribution along the radial direction and uniform distribution along the axial direction endow it with the ability of broadband transmission.

[0042] In this embodiment, the discrete flexible composite layer 2 is formed by uniformly doping micron tungsten particles in the base layer. Moreover, the doping concentrations of the micron tungsten particles in the first discrete flexible composite layer 201, the second discrete flexible composite layer 202, the third discrete flexible composite layer 203, the fourth discrete flexible composite layer 204, the fifth discrete flexible composite layer 205, and the sixth discrete flexible composite layer 206 are different, which is achieved by the different mass percentages of the flexible silicone elastomer and the micron tungsten particles in this embodiment. Specifically, the base layer can be first made of the flexible silicone elastomer material, and then the corresponding mass fraction of micron tungsten particles is uniformly doped into the base layer. Alternatively, the flexible silicone elastomer material can be doped with the corresponding mass fraction of micron tungsten particles and then uniformly stirred, and then the mixed material is made into the corresponding shape through a mold or the like, which is not limited here. The flexible silicone elastomer can be silicone.

[0043] Furthermore, the acoustic refractive index n(x) of the first discrete flexible composite layer 201, the second discrete flexible composite layer 202, the third discrete flexible composite layer 203, the fourth discrete flexible composite layer 204, the fifth discrete flexible composite layer 205, and the sixth discrete flexible composite layer 206 satisfies Equation 1:

[0044]

[0045] where y s is the thickness of the flexible metalens, and y a is the thickness of the phase difference layer. is the refractive index of the phase difference layer, n0 is the refractive index of the background medium, d is the distance from the focal point of the flexible lens to the outer surface of the flexible lens, and x is the horizontal axis coordinate.

[0046] In this embodiment, y s can also be regarded as the coordinate of the flexible lens, and y a can also be regarded as the coordinate of the phase difference layer. The first term in Equation 1 represents the refractive index of the flexible lens matrix eliminating the phase difference layer, which is the product of the refractive indices of the phase difference layer and the coordinate transformation tensor. In the third term of Equation 1, d is the distance from the focal point of the flexible lens to the outer surface of the flexible lens, and x is the horizontal axis coordinate, which is the independent variable. In this embodiment, the background medium is water with a refractive index of 1.

[0047] Furthermore, the mass percentages of the flexible silicone elastomer and the micron tungsten particles in the first discrete flexible composite layer 201, the second discrete flexible composite layer 202, the third discrete flexible composite layer 203, the fourth discrete flexible composite layer 204, the fifth discrete flexible composite layer 205, and the sixth discrete flexible composite layer 206 are designed and obtained according to the effective medium theory, and the mass percentages of the flexible silicone elastomer and the micron tungsten particles satisfy Equation 2:

[0048]

[0049] where φ m represents the mass percentage of the flexible silicone elastomer and the micron tungsten particles, is the volume fraction of the composite of the flexible silicone elastomer and the micron tungsten particles, ρ1 represents the mass density of the silicone elastomer, and ρ2 represents the mass density of the micron tungsten particles;

[0050] so that the acoustic refractive index satisfies Equation 1.

[0051] In this embodiment, according to the effective medium theory embedded in the non-viscous fluid, micron tungsten particles with different mass fractions are dispersed in the silicone elastomer to achieve the refractive index function in Equation 1, and the mass fraction can be described by Equation 2. At a medical ultrasound frequency of 0.5 MHz, the wavelength in tissue is 3 mm, and the minimum size of the micron tungsten particles is 1-5 microns, which is much smaller than 3000 times the minimum incident wavelength. The physical effects of the effective density and the effective sound velocity of the flexible lens can be understood from the perspective of the effective medium theory. Based on the long-wave approximation hypothesis, the effective parameters of the composite of the flexible silicone elastomer and the micron tungsten particles can be expressed as:

[0052]

[0053]

[0054]

[0055] Among them, ρ * , and respectively represent the equivalent density, the transverse wave speed of sound, and the longitudinal wave speed of sound of the flexible silicon elastomer and micron tungsten particle composite material. The equivalent Lame constant and shear modulus satisfy the following equations:

[0056]

[0057]

[0058]

[0059] The densities of the flexible silicon elastomer and micron tungsten particles are respectively and. The Lame constants of the flexible silicon elastomer and micron tungsten particles are respectively GPa and = 20.19 GPa. The shear moduli of the flexible silicon elastomer and micron tungsten particles are respectively = 6.14 kPa and = 15.6 GPa. According to the above formula derivation, as the mass fraction increases, the equivalent density increases from to, the acoustic refractive index increases from 1.4 to 3.2, and the acoustic impedance coverage range is from to. According to, the composite material parameters with different mass fractions required for the preparation of the flexible superlens can be obtained.

[0060] Further, the outer wall corresponding radii of the first discrete flexible composite layer 201, the second discrete flexible composite layer 202, the third discrete flexible composite layer 203, the fourth discrete flexible composite layer 204, the fifth discrete flexible composite layer 205, and the sixth discrete flexible composite layer 206 are respectively 20.2 - 20.3 mm, 34.0 - 34.1 mm, 42.7 - 42.8 mm, 49.1 - 49.2 mm, 54.1 - 54.2 mm, 59.95 - 60.05 mm.

[0061] Specifically, the outer wall corresponding radii of the first discrete flexible composite layer 201, the second discrete flexible composite layer 202, the third discrete flexible composite layer 203, the fourth discrete flexible composite layer 204, the fifth discrete flexible composite layer 205, and the sixth discrete flexible composite layer 206 are respectively 20.241 mm, 34.078 mm, 42.732 mm, 49.129 mm, 54.148 mm, 60 mm.

[0062] In this embodiment, the inner diameter of the maximum diameter of the housing 1 is 116.47 mm, and the outer diameter of the maximum diameter is 145 mm. A support member is provided on the periphery of the housing 1, and the six-layer discrete flexible composite layer 2 is defined inside the housing 1 through the support member. The height of the support member is 15 mm. The preparation method is as follows: First, a composite material of flexible silicone elastomer and micron tungsten particles with different mass fractions of flexible silicone elastomer and micron tungsten particles is filled into the odd layers 1, 3, and 5. After removing the 3D printing outer shell, glue is then poured into the even layers 2, 4, and 6. After the six-layer glue pouring is completed, the 3D printing support is removed.

[0063] Further, the base layers of the first discrete flexible composite layer 201 and the second discrete flexible composite layer 202 are both composed of A glue and B glue of Ecoflex 00-30, without adding a diluent, and are mixed in a ratio of 1:1; and / or,

[0064] The base layers of the third discrete flexible composite layer 203, the fourth discrete flexible composite layer 204, the fifth discrete flexible composite layer 205, and the sixth discrete flexible composite layer 206 are all composed of A glue, B glue, and diluent of Ecoflex 00-30, and are mixed in a ratio of 1:1:1.

[0065] In this embodiment, Ecoflex silicone is platinum-catalyzed silicone, which has the characteristics of being versatile and easy to use. The weight or volume mixing ratio of Ecoflex silicone is 1A:1B, and it cures at room temperature with a negligible shrinkage rate. The low viscosity ensures easy mixing and degassing. The cured silicone is very soft, very strong, and very "elastic", can be stretched many times the original size without tearing, and will elastically recover to its original shape without deformation. The A glue, B glue, and diluent of Ecoflex 00-30 are directly purchased from the prior art and can be directly bought on the market. The core structure of this embodiment is prepared by the A glue, B glue, and diluent of Ecoflex 00-30, which is designed by soft material - metamaterial - transformation acoustics, and has the advantages of simple production, easy mass production and processing, etc.

[0066] Further, the discrete flexible composite layer is made of the flexible silicone elastomer doped with micron tungsten particles with corresponding mass fractions as raw materials, and is introduced into a mold made by 3D printing.

[0067] This embodiment further provides a use of a broadband focusing flexible superlens for focusing acoustic energy inside human tissues or bones, or transmitting acoustic energy through a phase difference layer.

[0068] Experimental data

[0069] According to Figure 4, comparison of the simulated results of the sound intensity field with and without the flexible hyperlens at a frequency of 120 kHz. It can be found that the flexible hyperlens with broadband focusing provided in this embodiment has a focusing characteristic, and the focal point is 50 mm away from the outer surface of the flexible hyperlens along the z-axis direction. In the experiment, the incident wavelength at a working frequency of 120 kHz is 12 mm, and the moving step of the motor is 1 mm, which can ensure that there are 12 measurement points within one wavelength range.

[0070] According to Figure 5 , it is an experimental schematic diagram of the experimental measurement of ultrasonic broadband focusing. The signal generator is used to generate five pulse signals. Then the signal is amplified by a broadband power amplifier and drives a broadband transducer (50 kHz - 0.5 MHz) to transmit broadband acoustic signals. The hydrophone is driven by a DC regulated power supply, receives signals in an underwater environment, and then is stored in a computer after A / D conversion through an oscilloscope. A three-dimensional moving motor is used to drive the hydrophone to move and scan the sound field.

[0071] According to Figure 6 , by introducing the flexible hyperlens with broadband focusing provided in this embodiment, the simulated transmitted sound pressure level can be increased from -17.5 dB to nearly 0 dB. During the experiment, the sound pressure was measured five times around the focal region, and the simulated transmitted sound pressure level has a consistent trend compared with the experimental results. In the range of 50 kHz - 0.5 MHz, without the flexible hyperlens, the experimental average sound pressure level is -16.05 dB, and with the flexible hyperlens, it is increased to -4.01 dB. This indicates that when the flexible hyperlens is applied, the sound pressure increases by a factor of four (12.04 decibels). The simulation results show that without the flexible hyperlens, the full width at half maximum is distributed between 94.546 - 105.97 mm, while with the flexible hyperlens, it is distributed between 1.59 - 7.98 mm, which is consistent with the experimental results. In the experimental frequency range of 50 kHz - 0.5 MHz, without the flexible hyperlens, the experimental average full width at half maximum is 97.83 mm, and with the flexible hyperlens, it is 8.37 mm. The experimental results show that after introducing the flexible hyperlens with broadband focusing provided in this embodiment, the average spatial resolution is increased to 11.69 times (more than 10 times). It should be noted that in the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps not listed in the claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The present invention can be implemented by means of hardware including several different elements and by means of a suitably programmed computer. In a unit claim listing several means, several of these means can be embodied by the same item of hardware. The use of the words first, second, and third, etc. does not denote any order. These words can be interpreted as names.

[0072] Although the preferred embodiments of the present invention have been described, additional changes and modifications can be made to these embodiments by those skilled in the art once they learn the basic creative concept. Therefore, the appended claims are intended to be construed to include the preferred embodiments as well as all changes and modifications that fall within the scope of the present invention.

[0073] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

[0074] In the present invention, unless otherwise clearly defined and limited, the terms "mounted", "connected", "connected to", "fixed", etc. shall be construed in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0075] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms should not be understood as necessarily referring to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

Claims

1. A flexible hyperlens for broadband focusing, characterized in that: It includes a housing and a discrete flexible composite layer, and the housing is a straight cylindrical structure; The discrete flexible composite layer includes a first discrete flexible composite layer, a second discrete flexible composite layer, a third discrete flexible composite layer, a fourth discrete flexible composite layer, a fifth discrete flexible composite layer, and a sixth discrete flexible composite layer. The first discrete flexible composite layer is a cylindrical structure and is arranged at the central position of the housing. The second discrete flexible composite layer, the third discrete flexible composite layer, the fourth discrete flexible composite layer, the fifth discrete flexible composite layer, and the sixth discrete flexible composite layer are annular cylindrical structures and are sequentially connected starting from the side wall of the first discrete flexible composite layer; The discrete flexible composite layer includes a base layer made of a flexible silicone elastomer, and micron tungsten particles doped in the base layer. The discrete flexible composite layer is uniformly mixed by the flexible silicone elastomer and the micron tungsten particles according to different mass percentages; The acoustic refractive indices n of the first discrete flexible composite layer, the second discrete flexible composite layer, the third discrete flexible composite layer, the fourth discrete flexible composite layer, the fifth discrete flexible composite layer, and the sixth discrete flexible composite layer satisfy Formula 1: Among them, y s is the thickness of the flexible metalens, y a is the thickness of the phase difference layer, is the refractive index of the phase difference layer, n0 is the refractive index of the background medium, d is the distance from the focus of the flexible metalens to the outer surface of the flexible metalens, and x is the horizontal axis coordinate; The mass percentages of the flexible silicone elastomer and the micron tungsten particles in the first discrete flexible composite layer, the second discrete flexible composite layer, the third discrete flexible composite layer, the fourth discrete flexible composite layer, the fifth discrete flexible composite layer, and the sixth discrete flexible composite layer are obtained by design according to the equivalent medium theory.

2. The flexible hyperlens for broadband focusing according to claim 1, wherein: The mass percentages of the flexible silicone elastomer and the micron tungsten particles satisfy Formula 2: Among them, φ m represents the mass percentage of the flexible silicon elastomer and the micron tungsten particles, is the volume fraction of the composite of the flexible silicon elastomer and the micron tungsten particles, ρ1 represents the mass density of the silicon elastomer, and ρ2 represents the mass density of the micron tungsten particles; So that the acoustic refractive index satisfies the Formula 1.

3. The flexible hyperlens for broadband focusing according to claim 2, wherein: The outer wall corresponding radii of the first discrete flexible composite layer, the second discrete flexible composite layer, the third discrete flexible composite layer, the fourth discrete flexible composite layer, the fifth discrete flexible composite layer, and the sixth discrete flexible composite layer are 20.2 - 20.3 mm, 34.0 - 34.1 mm, 42.7 - 42.8 mm, 49.1 - 49.2 mm, 54.1 - 54.2 mm, 59.95 - 60.05 mm respectively.

4. The flexible hyperlens for broadband focusing according to claim 3, wherein: The outer wall corresponding radii of the first discrete flexible composite layer, the second discrete flexible composite layer, the third discrete flexible composite layer, the fourth discrete flexible composite layer, the fifth discrete flexible composite layer, and the sixth discrete flexible composite layer are 20.241 mm, 34.078 mm, 42.732 mm, 49.129 mm, 54.148 mm, 60 mm respectively.

5. The flexible hyperlens for broadband focusing according to claim 3, characterized in that: The base layers of the first discrete flexible composite layer and the second discrete flexible composite layer are both composed of Ecoflex 00 - 30 A glue and B glue mixed in a ratio of 1:1; and / or, The base layers of the third discrete flexible composite layer, the fourth discrete flexible composite layer, the fifth discrete flexible composite layer, and the sixth discrete flexible composite layer are all composed of Ecoflex 00 - 30 A glue, B glue, and a diluent mixed in a ratio of 1:1:

1.

6. The flexible hyperlens for broadband focusing according to claim 1, characterized in that: The background medium is water.

7. A flexible hyperlens for broadband focusing according to any one of claims 1 to 6, characterized in that: The discrete flexible composite layer is prepared by using the flexible silicone elastomer doped with micron tungsten particles with a corresponding mass fraction as a raw material and introducing it into a mold printed by 3D printing.

8. Use of a broadband focusing flexible metalens, characterized in that: The broadband focusing flexible hyperlens adopts the broadband focusing flexible hyperlens as described in claim 7, and is used for focusing acoustic energy inside human tissues or bones, or transmitting acoustic energy through a phase difference layer.

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