Ultrathin acoustic superlattice array and method of making same

Abstract

The present application relates to the technical field of acoustic metamaterials and sound field regulation, and particularly relates to an ultrathin acoustic superstructure array and a preparation method thereof, the ultrathin acoustic superstructure array comprising a substrate and double-layer acoustic superstructure units arranged in an array on the substrate, each double-layer acoustic superstructure unit comprising a hard layer and a flexible layer stacked vertically, the height of the flexible layer at different positions being determined according to a preset time delay distribution corresponding to a target sound field regulation function, so that the ultrathin acoustic superstructure array can still maintain the target sound field regulation function when deviating from the design center frequency. The present application uses a time-domain time delay design method to replace the traditional frequency-domain phase design method, and continuously regulates the time delay by changing the height proportion of the flexible layer, effectively widening the working frequency bandwidth of the acoustic superstructure array, so that it can realize stable sound field regulation function in a wide frequency band range.

Description

Technical Field

[0001] This invention belongs to the field of acoustic metamaterials and sound field manipulation technology, and particularly relates to an ultrathin acoustic metastructure array and its preparation method. Background Technology

[0002] Acoustic metamaterials, as artificial composite materials composed of subwavelength-scale unit structures arranged in a specific manner, exhibit a powerful ability to manipulate sound waves, including sound field focusing, deflection, and filtering. Acoustic metastructures based on acoustic metamaterials can achieve flexible manipulation of sound waves at the subwavelength scale, possessing properties not found in natural materials such as equivalent negative elastic modulus and equivalent negative mass density. Therefore, they show broad application prospects in fields such as ultrasonic imaging, non-destructive testing, and underwater acoustic detection.

[0003] Currently, most acoustic metastructures are designed using the principle of frequency-domain phase modulation, which involves constructing the desired sound field distribution by designing the phase response of the unit at a specific frequency. Because this design method relies on the resonance effect of the unit, its phase modulation capability is highly frequency-dependent. When the frequency of the incident sound wave deviates from the designed center frequency, the phase response of the unit changes, disrupting the pre-designed spatial phase distribution. This limits the acoustic metastructure to operating effectively only at a single frequency or within a very narrow frequency bandwidth, making it difficult to achieve stable sound field modulation over a wide frequency range. This limitation significantly restricts the application of acoustic metastructures in scenarios requiring wideband operation (such as broadband ultrasonic imaging and broadband non-destructive testing). Summary of the Invention

[0004] In view of this, the present invention aims to provide an ultrathin acoustic superstructure array and its fabrication method to solve the problem of excessively narrow operating frequency bandwidth caused by the frequency domain phase design method of existing acoustic superstructures.

[0005] To achieve the above objectives, the technical solution created by this invention is implemented as follows: An ultrathin acoustic superstructure array includes a substrate and two layers of acoustic superstructure units arranged in an array on the substrate. Each two-layer acoustic superstructure unit includes a vertically stacked rigid layer and / or a flexible layer. The height of the flexible layer at different locations is determined according to a preset time delay distribution corresponding to the target sound field modulation function, so that the ultrathin acoustic superstructure array can still maintain the target sound field modulation function when deviating from the design center frequency.

[0006] Furthermore, the target sound field control functions include sound field focusing, sound field deflection, and sound field oblique focusing. When the preset time delay distribution corresponds to the sound field focusing function, the ultrathin acoustic superstructure array is a focusing array structure. When the preset time delay distribution corresponds to the sound field deflection function, the ultrathin acoustic superstructure array is a deflection array structure. When the preset time delay distribution corresponds to the sound field oblique focusing function, the ultrathin acoustic superstructure array is an oblique focusing array structure.

[0007] Furthermore, the ultrathin acoustic superstructure array is arranged in a one-dimensional array or a two-dimensional array.

[0008] Furthermore, the rigid layer and the flexible layer are integrally formed using additive manufacturing technology, or the rigid layer and the flexible layer are formed separately and fixed together.

[0009] Furthermore, the rigid layer is made of non-metallic, alloy, or pure metallic materials, while the flexible layer is made of rubber.

[0010] Furthermore, the non-metallic material is any one of resin, ceramic, or glass; the pure metallic material is any one of steel, aluminum, gold, silver, or copper; the alloy material is any one of aluminum alloy, copper alloy, zinc alloy, magnesium alloy, or titanium alloy; and the rubber material is any one of silicone, nitrile rubber, or neoprene rubber.

[0011] A method for fabricating the above-mentioned ultrathin acoustic superstructure array includes the following steps: S1: Design the time delay distribution required for the ultrathin acoustic superstructure array based on the target sound field control function; S2: Obtain the relationship curve between the time delay of the pre-calibrated double-layer acoustic superstructure unit and the height ratio r of the flexible layer, where r = t1 / t, t1 is the height of the flexible layer, and t is the total height of the double-layer acoustic superstructure unit. Based on the relationship curve and the time delay distribution designed in step S1, determine the required height t1 of the flexible layer and the height t2 of the rigid layer for each double-layer acoustic superstructure unit in the ultra-thin acoustic superstructure array. S3: Prepare a hard layer with a height of t2 and a flexible layer with a height of t1 to form a double-layer acoustic superstructure unit; S4: Arrange multiple double-layer acoustic superstructure units on the substrate according to a preset arrangement to form an ultra-thin acoustic superstructure array.

[0012] Furthermore, in step S3, the rigid layer and the flexible layer are integrally formed using additive manufacturing technology, or the rigid layer and the flexible layer are formed independently and then physically adsorbed or bonded together.

[0013] Furthermore, the specific steps for forming a double-layer acoustic superstructure unit by independently molding the rigid layer and the flexible layer include the following: S31: Mix the liquid silicone and curing agent in the specified proportions and stir thoroughly; S32: De-air the prepared liquid silica gel; S33: Place the prepared hard layer into the encapsulation mold and inject the degassed liquid silicone into the encapsulation mold; S34: A flexible layer formed by the physical adsorption of liquid silicone to a rigid layer at room temperature; S35: Demolding process is performed on the flexible layer and the rigid layer to obtain a double-layer acoustic superstructure unit.

[0014] Furthermore, after the liquid silicone cures to form a flexible layer, it is bonded and fixed to the rigid layer.

[0015] Compared with the prior art, the present invention can achieve the following beneficial effects: This invention employs a time-domain time delay design method to replace the traditional frequency-domain phase design method. It utilizes a rigid-flexible composite double-layer acoustic metastructure unit to continuously control the time delay by varying the height ratio of the flexible layer, effectively broadening the operating frequency bandwidth of the acoustic metastructure array and enabling stable sound field control over a wide frequency range. Therefore, this invention expands the application scenarios of acoustic metastructures, making it particularly suitable for fields requiring wide-bandwidth operation, such as ultrasound imaging, medical imaging, and non-destructive testing. Attached Figure Description

[0016] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 A three-dimensional structural schematic diagram of the ultrathin acoustic superstructure array described in the embodiment of the present invention; Figure 2 A schematic diagram of the one-dimensional arrangement of the double-layer acoustic superstructure unit as described in the embodiment of the present invention; Figure 3 A schematic diagram of the two-dimensional arrangement of the double-layer acoustic superstructure unit as described in the embodiment of the present invention; Figure 4 A schematic diagram of the structure of the double-layer acoustic superstructure unit described in the embodiment of the present invention; Figure 5 This is a schematic diagram of the front view structure of the focusing acoustic superstructure array described in the embodiment of the present invention; Figure 6 A schematic diagram of the focused acoustic field of the focused acoustic superstructure array described in the embodiment of the present invention; Figure 7This is a schematic diagram of the front view structure of the deflection acoustic superstructure array described in an embodiment of the present invention; Figure 8 A schematic diagram of the deflection acoustic field of the deflection acoustic superstructure array described in the embodiment of the present invention; Figure 9 A schematic diagram of the main view structure of the oblique focusing acoustic superstructure array described in the embodiment of the present invention; Figure 10 A schematic diagram of the oblique focusing acoustic field of the oblique focusing acoustic superstructure array described in the embodiment of the present invention; Figure 11 This is a schematic diagram showing the height of the flexible layer at various positions in the acoustic superstructure array with different configurations when using a one-dimensional arrangement, as described in the embodiments of the present invention; wherein, the center of the length L of the acoustic superstructure array is taken as the zero point, the position of the double-layer superstructure unit to the left of the zero point is negative, and the position of the double-layer superstructure unit to the right of the zero point is positive. Figure 12 A schematic diagram showing the relationship between the time delay of the double-layer acoustic superstructure unit and the height ratio r of the flexible layer in an embodiment of the present invention. Figure 13 This is a schematic diagram of the time delay distribution of the focusing acoustic superstructure array described in the embodiment of the present invention; wherein, the relative distance refers to the distance between the double-layer acoustic superstructure units on the left and right sides of the zero point with the center of the length of the focusing acoustic superstructure array as the zero point, and the distance between the double-layer superstructure units on the left side of the zero point and the zero point is negative, and the distance between the double-layer superstructure units on the right side of the zero point and the zero point is positive.

[0017] Explanation of reference numerals in the attached figures: 1. Substrate; 2. Double-layer acoustic superstructure unit; 21. Rigid layer; 22. Flexible layer. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0019] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0020] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0021] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "assembly," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0022] The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0023] like Figure 1 As shown, this invention provides an ultrathin acoustic metastructure array, including a substrate 1 and two-layer acoustic metastructure units 2, with multiple two-layer acoustic metastructure units 2 arranged in an array on the substrate 1. The length of the ultrathin acoustic metastructure array is denoted as L, the width as W, and the height as t. In this embodiment, L = 8 mm, W = 9.3 mm, and t = 1 mm. It should be noted that the values ​​of L, W, and t can be any positive numbers; the above values ​​are merely illustrative and do not constitute a limitation of this invention.

[0024] The arrangement of the double-layer acoustic superstructure unit 2 can be one-dimensional or two-dimensional. For example... Figure 2As shown, when arranged in one dimension, it consists of N double-layer acoustic superstructure units 2 arranged along a straight line. N is a positive integer, the spacing between two adjacent double-layer acoustic superstructure units 2 is p, and the width of each double-layer superstructure unit 2 is s. In this embodiment, N=12, p=0.18mm, and s=0.5mm. It should be noted that the value of N can be any positive integer, and the values ​​of p and s can be any values. The above values ​​are only illustrative and do not constitute a limitation on the present invention. Figure 3 As shown, when arranged in two dimensions, it consists of M rows and N columns of double-layered superstructure units 2, with a spacing of m between each row of double-layered acoustic superstructure units 2. In this embodiment, M=N=12, W=9.3mm, m=0.3mm, and p=0.18mm. It should be noted that the values ​​of M and N can be any positive integers, the value of W can be any positive number, and the value of m can be any value. The above values ​​are merely illustrative and do not constitute a limitation on the present invention.

[0025] like Figure 4 As shown, the double-layer acoustic superstructure unit 2 consists of vertically stacked rigid layers 21 and / or flexible layers 22. The rigid layer 21 is made of a rigid material, which can be a non-metallic material, an alloy material, or a pure metallic material. Non-metallic materials include, but are not limited to, resin, ceramics, and glass; pure metallic materials include, but are not limited to, steel, aluminum, gold, silver, and copper; and alloy materials include, but are not limited to, aluminum alloys, copper alloys, zinc alloys, magnesium alloys, and titanium alloys. In this embodiment, resin material is preferably used as the rigid layer 21, and it is processed using 3D printing technology, which has the advantages of high processing accuracy, low cost, and ease of forming complex structures. The flexible layer 22 is made of a rubber material, which includes, but is not limited to, any one of silicone, nitrile rubber, and neoprene rubber. The rubber material can also be a composite material with elastic deformation capabilities. In this embodiment, silicone material is preferably used as the flexible layer 22, utilizing its excellent elastic deformation capabilities and low sound propagation speed to achieve precise control of sound wave propagation time. The positions of the rigid layer and the flexible layer are reciprocal, and the double-layer acoustic superstructure unit 2 can also be composed of two different rigid layers 21 or two different flexible layers 22.

[0026] By designing the height of the flexible layer 22 at different locations, the time delay of each double-layer acoustic superstructure unit 2 can be adjusted to obtain the time delay distribution of the entire ultrathin acoustic superstructure array, thereby achieving different target sound field control functions. The target sound field control functions include sound field focusing, sound field deflection, and sound field oblique focusing.

[0027] When the time delay distribution of an ultrathin acoustic metastructure array corresponds to the sound field focusing function, the ultrathin acoustic metastructure array is a focusing array structure, such as... Figure 5As shown, the focusing acoustic metastructure array acts like an optical convex lens, causing planar ultrasonic waves to converge during propagation, forming a focused sound field, such as... Figure 6 As shown. When applied to defect detection, a focused sound field can improve the detection sensitivity of minute defects.

[0028] When the time delay distribution of an ultrathin acoustic metastructure array corresponds to the sound field deflection function, the ultrathin acoustic metastructure array is a deflection array structure, such as... Figure 7 As shown, the deflection acoustic superstructure array acts like an optical prism, causing a complete deflection of the propagation direction of planar ultrasonic waves, forming a deflection sound field, such as... Figure 8 As shown. When applied to defect detection, deflected sound fields are suitable for detecting tilted defects (such as sloping grooves and cracks) or non-perpendicular incident scenarios, without the need for physically rotating the probe.

[0029] When the time delay distribution of an ultrathin acoustic metastructure array corresponds to the oblique focusing function of the sound field, the ultrathin acoustic metastructure array is an oblique focusing array structure, such as... Figure 9 As shown. The oblique-focusing acoustic superstructure array is a combination of a focusing acoustic superstructure array and a deflection acoustic superstructure array. Planar ultrasonic waves not only deflect in direction but also converge along their deflected path, forming an oblique-focusing sound field, such as... Figure 10 As shown. When applied to defect detection, oblique-focused sound fields are suitable for detecting deep defects in complex structures, such as when incident at a non-perpendicular angle and focused on the defect location in a confined space. The specific configuration of the acoustic superstructure array is determined based on the sound field control requirements.

[0030] like Figure 11 As shown, in a one-dimensional arrangement, the height t1 of the flexible layer 22 at different positions corresponding to the acoustic superstructure array realizing the sound field focusing function, sound field deflection function and sound field oblique focusing function is shown.

[0031] Existing acoustic metastructures employ frequency-domain phase design methods, the core idea of ​​which is to generate the desired phase delay in each unit at a specific frequency. Since the phase delay of each unit depends on resonance effects, it exhibits strong frequency dispersion characteristics. When the incident sound wave frequency deviates from the design frequency, the phase deviation of each unit is different, disrupting the pre-designed spatial phase distribution and causing the sound field control function to fail. Therefore, this type of acoustic metastructure can only operate within a single frequency or an extremely narrow bandwidth.

[0032] This invention differs from others by employing a time-domain time delay design method. Its physical essence lies in not directly controlling the phase of the sound wave at a specific frequency, but rather controlling the time delay required for the sound wave to pass through different double-layer acoustic superstructure units 2. The time delay for a sound wave to pass through a double-layer acoustic superstructure unit 2 is defined as the time it takes for the sound wave to pass from the rigid layer 21 through the flexible layer 22, where the positions of the rigid layer 21 and the flexible layer 22 are reciprocal, meaning the sound wave can also pass from the flexible layer 22 through the rigid layer 21. For a double-layer acoustic superstructure unit 2 composed of a rigid layer 21 and a flexible layer 22, the propagation speed of the sound wave in the flexible layer 22 is lower than that in the rigid layer 21. Therefore, by adjusting the height ratio r = t1 / t of the flexible layer 22 (where t is the total height of the double-layer acoustic superstructure unit 2 and t1 is the height of the flexible layer 22), the time delay for the sound wave to pass through the double-layer acoustic superstructure unit 2 can be continuously changed.

[0033] The time delay is approximately constant over a wide frequency range, depending only on the geometry and material velocity of the double-layer acoustic superstructure unit 2, unlike the phase which is linearly related to frequency. Although the phase value changes with frequency, the time delay itself remains constant. Therefore, once the spatial time delay distribution of an acoustic superstructure array designed based on time delay is determined, it can maintain the same wavefront timing relationship at all frequencies, thereby achieving broadband sound field manipulation.

[0034] Specifically, the present invention achieves wideband operation through the following steps: i. Pre-calibrate the relationship between the time delay of the double-layer acoustic superstructure unit 2 and the height ratio r of the flexible layer 22.

[0035] For the selected rigid and flexible materials, the relationship curve between the height ratio r of the flexible layer 22 and the time delay is established through simulation or experiment, such as... Figure 12 As shown in the figure, this relationship curve remains constant over a wide frequency range and does not change with the frequency of the incident sound wave.

[0036] ii. Design the time delay distribution of the ultrathin acoustic superstructure array based on the target sound field control function.

[0037] Based on the required sound field control functions (such as focusing, deflection, and oblique focusing), the time delay required for each double-layer acoustic superstructure unit 2 on the array is designed, resulting in the time delay distribution of the acoustic superstructure array. Taking a focusing acoustic superstructure array as an example, its time delay distribution is as follows: Figure 13 As shown, this time delay distribution is independent of frequency.

[0038] iii. Inversely determine the height t1 of the flexible layer 22 of each double-layer acoustic superstructure unit 2.

[0039] Substituting the time delay of each double-layer acoustic superstructure unit 2 into the relationship curve between the height proportion r of the flexible layer 22 and the time delay, the height proportion r of the flexible layer 22 in each double-layer acoustic superstructure unit 2 is determined in reverse. Then, the height t1 of the flexible layer 22 in each double-layer acoustic superstructure unit 2 is calculated using the formula r = t1 / t. Since the total height t of the double-layer acoustic superstructure unit 2 is a known quantity, the height t2 of the rigid layer 21 is also determined after calculating the height t1 of the flexible layer 22.

[0040] Through the above design, when the frequency of the incident sound wave changes, although the phase delay of each double-layer acoustic superstructure unit 2 changes linearly, the relative time delay relationship between different double-layer acoustic superstructure units 2 remains unchanged. Therefore, the wavefront shape (i.e., the equiphase surface shape) of the sound wave remains the same at all frequencies, thereby enabling stable sound field control function over a wide frequency range.

[0041] The foregoing details the structure and working principle of the ultrathin acoustic superstructure array provided by this invention. This invention also provides a method for fabricating an ultrathin acoustic superstructure array, comprising the following steps: S1: Design the time delay distribution required for the ultrathin acoustic superstructure array based on the target sound field control function.

[0042] The design method for time delay distribution is existing technology, so it will not be described in detail in this invention.

[0043] S2: Obtain the relationship curve between the time delay of the pre-calibrated double-layer acoustic superstructure unit 2 and the height ratio r of the flexible layer 22, where r = t1 / t, t1 is the height of the flexible layer 22, and t is the total height of the double-layer acoustic superstructure unit 2. Based on the relationship curve and the time delay distribution designed in step S1, determine the required height t1 of the flexible layer 22 and the height t2 of the rigid layer 21 for each double-layer acoustic superstructure unit 2 in the ultra-thin acoustic superstructure array.

[0044] S3: Prepare a hard layer 21 with a height of t2 and a flexible layer 22 with a height of t1 to form a double-layer acoustic superstructure unit 2.

[0045] The rigid layer 21 and the flexible layer 22 are integrally formed using additive manufacturing technology, or the rigid layer 21 and the flexible layer 22 are formed independently and then physically adsorbed or bonded together.

[0046] The following explanation uses resin material as the rigid layer 21 and silicone material as the flexible layer 22 as examples of independent preparation.

[0047] The fabrication of the double-layer acoustic superstructure unit 2 specifically includes the following steps: S31: Mix the liquid silicone and curing agent in the specified proportions and stir thoroughly.

[0048] The purpose of thorough stirring is to ensure that the liquid silicone and curing agent are mixed evenly.

[0049] S32: De-air the prepared liquid silica gel.

[0050] The degassing process is to prevent air bubbles from forming inside the cured silicone, thereby preventing these bubbles from affecting the propagation of the sound field.

[0051] S33: Place the prepared hard layer 21 into the encapsulation mold, and inject the degassed liquid silicone into the encapsulation mold.

[0052] Resin material can be printed into a hard layer 21 using 3D printing technology, and the encapsulation mold can also be formed using 3D printing technology.

[0053] The encapsulation mold has cavities inside, one cavity for placing the hard layer 21 and the other cavity for injecting the de-bubbling liquid silicone.

[0054] S34: A flexible layer 22 is formed by curing liquid silicone at room temperature and physically adsorbing it onto the rigid layer 21.

[0055] After curing, the liquid silicone becomes an elastic solid silicone, which serves as the flexible layer 22. It also has physical interactions such as van der Waals forces and hydrogen bonds with the resin surface, which serves as the rigid layer 21, to achieve a tight bond between the two.

[0056] To further improve the bonding strength between the rigid layer 21 and the flexible layer 22, the flexible layer 22 is bonded to the rigid layer 21 after the liquid silicone has cured to form the flexible layer 22.

[0057] S35: Demolding process is performed on flexible layer 22 and rigid layer 21 to obtain double-layer acoustic superstructure unit 2.

[0058] S4: Arrange multiple double-layer acoustic superstructure units 2 on the substrate 1 according to a preset arrangement to form an ultra-thin acoustic superstructure array.

[0059] The double-layer acoustic superstructure unit 2 can be fixed to the substrate 1 by means of adhesive bonding or other methods.

[0060] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0061] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. An ultrathin acoustic superstructure array, characterized in that, The system includes a substrate and two-layer acoustic superstructure units arranged in an array on the substrate. Each two-layer acoustic superstructure unit includes a vertically stacked rigid layer and a flexible layer. The total height of the two-layer acoustic superstructure unit is t. The heights t1 of the flexible layer and t2 of the rigid layer at different locations are determined according to a preset time delay distribution corresponding to the target sound field control function. The time delay distribution is determined by a pre-calibrated curve showing the relationship between the time delay of the two-layer acoustic superstructure unit and the height ratio r of the flexible layer, where r = t1 / t. This ensures that the ultra-thin acoustic superstructure array can maintain the target sound field control function even when it deviates from the design center frequency.

2. The ultrathin acoustic superstructure array according to claim 1, characterized in that, The target sound field control function includes sound field focusing function, sound field deflection function, and sound field oblique focusing function. When the preset time delay distribution corresponds to the sound field focusing function, the ultra-thin acoustic superstructure array is a focusing array structure. When the preset time delay distribution corresponds to the sound field deflection function, the ultra-thin acoustic superstructure array is a deflection array structure. When the preset time delay distribution corresponds to the sound field oblique focusing function, the ultra-thin acoustic superstructure array is an oblique focusing array structure.

3. The ultrathin acoustic superstructure array according to claim 1 or 2, characterized in that, The ultrathin acoustic superstructure array is arranged in a one-dimensional array or a two-dimensional array.

4. The ultrathin acoustic superstructure array according to claim 3, characterized in that, The rigid layer and the flexible layer are integrally formed using additive manufacturing technology, or the rigid layer and the flexible layer are formed separately and fixed together.

5. The ultrathin acoustic superstructure array according to claim 4, characterized in that, The rigid layer is made of non-metallic, alloy, or pure metallic materials, while the flexible layer is made of rubber.

6. The ultrathin acoustic superstructure array according to claim 5, characterized in that, Non-metallic materials are any one of resin, ceramic, and glass; pure metallic materials are any one of steel, aluminum, gold, silver, and copper; alloy materials are any one of aluminum alloy, copper alloy, zinc alloy, magnesium alloy, and titanium alloy; and rubber materials are any one of silicone, nitrile rubber, and chloroprene rubber.

7. A method for fabricating an ultrathin acoustic superstructure array according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1: Design the time delay distribution required for the ultrathin acoustic superstructure array based on the target sound field control function; S2: Obtain the relationship curve between the time delay of the pre-calibrated double-layer acoustic superstructure unit and the height ratio r of the flexible layer, where r = t1 / t, t1 is the height of the flexible layer, and t is the total height of the double-layer acoustic superstructure unit. Based on the relationship curve and the time delay distribution designed in step S1, determine the required height t1 of the flexible layer and the height t2 of the rigid layer for each double-layer acoustic superstructure unit in the ultra-thin acoustic superstructure array. S3: Prepare a hard layer with a height of t2 and a flexible layer with a height of t1 to form a double-layer acoustic superstructure unit; S4: Arrange multiple double-layer acoustic superstructure units on the substrate according to a preset arrangement to form an ultra-thin acoustic superstructure array.

8. The method for fabricating an ultrathin acoustic superstructure array according to claim 7, characterized in that, In step S3, the rigid layer and the flexible layer are integrally formed using additive manufacturing technology, or the rigid layer and the flexible layer are formed independently and then physically adsorbed or bonded together.

9. The method for fabricating an ultrathin acoustic superstructure array according to claim 8, characterized in that, The specific steps involved in forming a double-layer acoustic superstructure unit by independently molding the rigid and flexible layers are as follows: S31: Mix the liquid silicone and curing agent in the specified proportions and stir thoroughly; S32: De-air the prepared liquid silica gel; S33: Place the prepared hard layer into the encapsulation mold and inject the degassed liquid silicone into the encapsulation mold; S34: A flexible layer formed by the physical adsorption of liquid silicone to a rigid layer at room temperature; S35: Demolding process is performed on the flexible layer and the rigid layer to obtain a double-layer acoustic superstructure unit.

10. The method for fabricating an ultrathin acoustic superstructure array according to claim 9, characterized in that, After the liquid silicone cures to form a flexible layer, it is bonded and fixed to the rigid layer.

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