A three-dimensional acoustic-vibration moiré metasurface constructed using the principle of nonlocal anisotropy.

Abstract

This invention belongs to the field of acoustic and vibration metamaterials and wave control technology, specifically relating to a three-dimensional acoustic and vibration moiré metasurface constructed using the principle of nonlocal anisotropy. This metasurface is a three-dimensional structure composed of several three-dimensional units stacked along the x, y, and z directions. All three-dimensional units in each plane of the three-dimensional structure can be twisted around a central axis perpendicular to that plane at a set angle. The three-dimensional structure of this invention not only has the ability to freely twist and control, but also can adjust the interlayer coupling relationship under different twist angles, enabling the system to accurately control the propagation direction and mode of sound waves in a wider three-dimensional space. At the same time, the stacking of three-dimensional units forms a nonlocal state, realizing the transfer of acoustic energy between units, so that the acoustic energy of any unit can be transferred to any other unit.

Description

Technical Field

[0001] This invention belongs to the field of acoustic and vibration metamaterials and wave control technology, specifically relating to a three-dimensional acoustic and vibration moiré metasurface constructed using the principle of nonlocal anisotropy. Background Technology

[0002] Wave vibration manipulation is a key direction in modern engineering and physics research, especially with the advancement of metamaterials and metasurface technologies, which have made precise control over vibration and wave behavior possible. Traditional vibration systems typically rely on periodic structures or resonant units to modulate wave propagation characteristics, but these systems are often limited by structural scale, local resonance effects, and wavelength-dependent control range, making it difficult to achieve multi-dimensional, tunable vibration and wave manipulation.

[0003] Moiré metasurfaces, due to their unique quasi-periodic modulation properties, have demonstrated significant research value in fields such as vibration, wave manipulation, and energy transfer. By applying different relative torsional angles to bilayer periodic structures, moiré metasurfaces can induce novel wave propagation modes, such as magic-angle flat bands, asymmetric localization, and unidirectional channelization. These properties greatly expand the applications of metamaterials in vibration isolation, precise wave manipulation, and energy management. However, current research on bilayer moiré metasurfaces mainly focuses on two-dimensional structures, failing to fully leverage the potential advantages of three-dimensional systems. In the study of three-dimensional vibration and wave metamaterials, nonlocal effects and extreme anisotropy are two key factors. Nonlocal effects refer to the fact that wave propagation is influenced not only by local structures but also by coupling effects from distant structures; this characteristic is particularly pronounced in high-order metamaterials. On the other hand, anisotropy causes the system to exhibit significantly different wave behaviors in different directions, thus forming low-loss unidirectional channelization characteristics in specific directions and achieving localization in other directions. However, research on these two factors in three-dimensional systems has not yet been achieved. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention proposes a scheme for realizing a three-dimensional acoustic-vibration moiré metasurface based on the principle of nonlocal extreme anisotropy.

[0005] The technical solution adopted by this invention to solve the technical problem is as follows:

[0006] A three-dimensional acoustic-vibration moiré metasurface constructed using the principle of nonlocal anisotropy is a three-dimensional structure composed of several three-dimensional units stacked along the x, y, and z directions. All three-dimensional units in each plane of the three-dimensional structure can be twisted around a central axis perpendicular to that plane by a set angle.

[0007] The spacing between the planes of the three-dimensional structure can be changed.

[0008] The three-dimensional unit includes a central resonant cavity, and each of the six end faces of the central resonant cavity is provided with a coupling pipe. The ends of the coupling pipes are provided with coupling cavities. The coupling pipes and coupling cavities on the symmetrical end faces of the central resonant cavity are the same.

[0009] The length of the coupling pipe, the volume of the coupling cavity, and the corresponding end face area of ​​the central resonant cavity on the three symmetrical end faces of the central resonant cavity must each have at least one different parameter.

[0010] The coupling pipe and coupling cavity are hollow structures, and the diameter of the coupling pipe is 1 mm to 4 mm.

[0011] A three-dimensional acoustic-vibration moiré metasurface constructed using the principle of nonlocal extreme anisotropy also includes a point sound source placed at the center of the three-dimensional structure.

[0012] The coupling pipe and coupling cavity are made of lightweight solid material.

[0013] The beneficial effects of this invention are as follows:

[0014] 1. The three-dimensional unit structure of this application is composed of stacked units in multiple directions to form a three-dimensional structure. This three-dimensional structure not only has the ability to freely twist and control, but also allows for adjustment of the interlayer coupling relationship at different twist angles, enabling the system to precisely control the propagation direction and mode of sound waves in a wider three-dimensional space. Compared with traditional metamaterial systems, this invention breaks the limitations of a single structure and fixed interlayer distance, realizing continuously adjustable sound field control capabilities, and providing a novel physical mechanism for sound wave channelization, unidirectional propagation, hyperbolic dispersion control, and localized wave modes.

[0015] 2. The three-dimensional structure of this application can be a cube, cuboid, or cone, and the metasurface can be applied to different array patterns. By optimizing the unit arrangement and coupling parameters, this invention can flexibly adapt to different application requirements, demonstrating excellent application potential in fields such as metasurface acoustics, ultrasonic imaging, acoustic stealth, and high-precision beam control.

[0016] 3. The three-dimensional stacking of the units in this application forms a non-local state, realizing the transfer of acoustic energy between units, so that the acoustic energy of any unit can be transferred to any other unit. This non-local characteristic means that the acoustic energy between different units no longer depends on the direct proximity relationship, and the propagation of sound waves is affected by the global system structure. This characteristic makes the propagation of sound waves on the metasurface more flexible and can achieve more precise sound field control.

[0017] 4. This application takes into account the principle of anisotropy and, through ingenious design, makes the acoustic impedance difference in the three directions of the three-dimensional unit large, and the sound wave propagates along the direction perpendicular to the hyperbolic dispersion line, thus realizing hyperbolic propagation.

[0018] 5. The metasurface of this application has good robustness and stability. Damage to individual three-dimensional units will not significantly weaken the overall sound wave control effect.

[0019] 6. The three-dimensional metasurface of this application has a relatively light overall mass and a small area, and can achieve efficient control of sound waves while maintaining the necessary strength. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the three-dimensional acoustic-vibration moiré metasurface of the present invention;

[0021] Figure 2 This is a front view of the three-dimensional acoustic-vibration moiré metasurface of the present invention;

[0022] Figure 3 This is a top view of the three-dimensional acoustic-vibration moiré metasurface of the present invention;

[0023] Figure 4 The diagram shows the acoustic pressure field of the three-dimensional acoustic-vibration moiré metasurface of the present invention under point sound source excitation;

[0024] Among them, (a) is the acoustic pressure field diagram of the zx plane of the three-dimensional acoustic moiré metasurface of the present invention;

[0025] (b) is a diagram of the acoustic pressure field in the xy plane of the three-dimensional acoustic moiré metasurface of the present invention;

[0026] (c) is a diagram of the acoustic pressure field in the yz plane of the three-dimensional acoustic moiré metasurface of the present invention;

[0027] Figure 5 This is a dispersion curve diagram of a single three-dimensional unit cell of the three-dimensional acoustic-vibration moiré metasurface of the present invention;

[0028] Explanation of reference numerals in the attached figures:

[0029] 1. Three-dimensional unit; 2. Central resonant cavity; 3. Coupling pipe; 301. Z-direction coupling pipe; 302. X-direction coupling pipe; 303. Y-direction coupling pipe; 4. Coupling cavity; 401. Z-direction coupling cavity; 402. Y-direction coupling cavity; 403. X-direction coupling cavity. Detailed Implementation

[0030] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0031] See Figure 1-3A three-dimensional acoustic-vibration moiré metasurface constructed using the principle of nonlocal anisotropy is a three-dimensional structure composed of several three-dimensional units 1 stacked along the x, y, and z directions. All three-dimensional units 1 in each plane of the three-dimensional structure can be twisted around a central axis perpendicular to the plane by a set angle. The three-dimensional structure can be flexibly assembled into a cube, cuboid, or pyramidal structure according to requirements. Different forms of three-dimensional structures can be divided into multiple planes that can be twisted to each other according to different directions, and the spacing between the planes of the three-dimensional structure can be changed. Partitions can be added between the planes or all three-dimensional units 1 in one of the planes can be raised to a set height.

[0032] The three-dimensional acoustic-vibration moiré metasurface system of this application uses a "magic-style" torsion structure as its core. The three-dimensional structure can be divided into several planes according to the x, y, z, or oblique plane directions. Each plane can be twisted around a central axis perpendicular to the plane at a certain angle, thereby effectively expanding the system's degree of freedom of adjustment and realizing flexible adjustment of the sound wave propagation path, phase, and amplitude. At the same time, this application considers the concept of nonlocality. By stacking several three-dimensional units 1 along the x, y, and z directions to form a three-dimensional structure, a nonlocal metasurface is formed, realizing the transfer of acoustic energy between units. This allows the acoustic energy of any three-dimensional unit to be transferred to any other three-dimensional unit, and the acoustic energy can be efficiently transferred throughout the entire system, rather than being limited to a certain local area, thus achieving a nonlocal state. This nonlocal characteristic means that the acoustic energy between different units no longer depends on direct proximity, and the propagation of sound waves is affected by the global system structure. This characteristic makes the propagation of sound waves on the metasurface more flexible and can achieve more precise sound field control. Furthermore, the spacing between the planes in this application can be changed, thereby changing the coupling strength, significantly reducing energy loss, and enhancing the unidirectional and localized acoustic-vibration isolation effect of the system.

[0033] The three-dimensional unit 1 includes a central resonant cavity 2. Coupling pipes 3 are respectively provided on the six end faces of the central resonant cavity 2. Coupling cavities 4 are provided at the ends of the coupling pipes 3. The coupling pipes 3 and coupling cavities 4 on the symmetrical end faces of the central resonant cavity 2 are the same. The coupling pipes 3 and coupling cavities 4 are hollow structures. The diameter of the coupling pipes 3 is 1~4mm. The coupling pipes 3 and coupling cavities 4 are made of lightweight solid materials.

[0034] The length of the coupling pipe 3, the volume of the coupling cavity 4, and the corresponding end face area of ​​the central resonant cavity 2 on the three symmetrical end faces of the central resonant cavity 2 must be different in at least one of these parameters. This setting is to ensure that the acoustic impedance of the central resonant cavity 2 is different in the x, y, and z directions, thereby exhibiting anisotropy. The length of the coupling pipe, the volume of the coupling cavity, and the corresponding planar area of ​​the central resonant cavity all have a certain influence on the acoustic impedance parameters. Therefore, at least one of the above three parameters must be different when setting them.

[0035] This application considers the principle of anisotropy and, through a clever design of the three-dimensional unit dimensions, achieves significant differences in acoustic impedance in three directions, thus successfully realizing extreme anisotropy. In isotropic metasurfaces, the wave dispersion curve is circular, at which point the sound wave diffuses in all directions, and wave propagation is unrestricted. However, as... Figure 5 As shown, our metasurface dispersion curve exhibits a hyperbolic shape, indicating that the sound wave propagates along the direction perpendicular to the hyperbola, i.e., hyperbolic propagation is achieved, which is a hallmark of extreme anisotropy.

[0036] The three-dimensional acoustic-vibration moiré metasurface constructed using the principle of nonlocal anisotropy also includes a point sound source. The point sound source is placed at the center of the three-dimensional structure and is used for the acoustic excitation of the metasurface. This allows the acoustic energy to be efficiently coupled and directly transferred to the metasurface unit array, thereby maximizing the acoustic wave injection efficiency and ensuring that the energy is evenly distributed to the surrounding units. This is the most important "sound source coupling region".

[0037] Example 1

[0038] In this embodiment, the three-dimensional acoustic-vibration moiré metasurface is stably mounted on a frame. It is a 5×5×5 array structure composed of several three-dimensional units 1 stacked along the x, y, and z directions. The lattice step size of each three-dimensional unit 1 is 40 mm. The three-dimensional unit 1 includes a z-direction coupling channel 301, a z-direction coupling cavity 401, a y-direction coupling cavity 402, an x-direction coupling cavity 403, a central resonant cavity 2, an x-direction coupling channel 302, and a y-direction coupling channel 303. The central resonant cavity 2 is provided with x-direction coupling channels 302, y-direction coupling channels 303, and z-direction coupling channels 301 on its symmetrical end faces along the x, y, and z directions, respectively. The ends of the x-direction coupling channels 302, y-direction coupling channels 303, and z-direction coupling channels 301 are provided with x-direction coupling cavities 403, y-direction coupling cavities 402, and z-direction coupling cavities 401, respectively.

[0039] Considering the principle of anisotropy, in this embodiment, the central resonant cavity 2 has a cuboid structure. The plane with the largest area corresponding to the z-direction coupling cavity 401 of the central resonant cavity 2 is the plane with the largest area, followed by the plane with the x-direction coupling cavity 403, and the plane with the smallest area corresponding to the y-direction coupling cavity 402. Therefore, in the design, the cavity volume of the z-direction coupling cavity 401 is the largest, while the cavity areas of the y-direction coupling cavity 402 and the x-direction coupling cavity 403 are the same. The length of the x-direction coupling pipe 302 is greater than the length of the z-direction coupling pipe 301, which is greater than the length of the y-direction coupling pipe 303. At this time, the cavity volume of the z-direction coupling cavity 401 is greater than that of the y-direction coupling cavity 402 and the x-direction coupling cavity 403, which results in the acoustic impedance in the z-direction being less than that in the x and y directions. At the same time, the central resonant cavity 2 is cuboid in shape, and the difference in the size of its short and long sides causes the acoustic impedance in the x and y directions to also be different. Therefore, the acoustic impedance difference of a single three-dimensional unit is relatively large, thus successfully achieving extreme anisotropy.

[0040] The specific dimensions of the central resonant cavity 2 are 18 mm long × 15 mm wide × 6 mm high; the z-direction coupling cavity 401 is 12 mm long and wide, and 10 mm high; the z-direction coupling pipe 301 is a cylindrical channel with a radius of 2 mm and a height of 7 mm; the x-direction coupling cavity 403 and the y-direction coupling cavity 402 are 9 mm long and wide, and 5 mm high; the x-direction coupling pipe 302 is 7.5 mm long, and the y-direction coupling pipe 303 is 6 mm long, with a pipe radius of 2 mm for both; each 3D unit 1 is printed using R4600 resin additive manufacturing technology, with a wall thickness of 1 mm for each printed part, which reduces the overall weight while ensuring acoustic and vibration performance and structural accuracy. If lower frequency applications are required, the unit size can be enlarged; if higher frequencies are required, the unit size can be reduced while maintaining the precise proportions between the structural components.

[0041] To ensure optimal sound source coupling across the entire structure, this invention places a point sound source (model 13A05-8Ω) at the central resonant cavity connection point of the three-dimensional structure. This allows sound waves to be efficiently coupled and transmitted to each three-dimensional unit of the metasurface structure. In a 5×5×5 array, by combining the point sound source with the three-dimensional metasurface structure and utilizing the coupling characteristics of the pipes and cavities in the three-dimensional direction, the system achieves efficient control and uniform distribution of sound waves. This design not only allows for flexible adjustment of the sound field distribution but also exhibits excellent stability and adaptability, making it suitable for various fields such as acoustic detection, beamforming, and ultrasonic imaging.

[0042] In this embodiment, the materials, dimensions, and torsion angles of each unit, its coupling pipes, and coupling cavities can all be adjusted proportionally within a certain range. Regarding size design and frequency adaptability, this embodiment selects a lattice step size of 40 mm, and the unit size can be scaled up or down proportionally as needed to adapt to different operating frequency requirements. In terms of manufacturing and assembly processes, this invention employs 3D printing technology to ensure structural accuracy and acoustic characteristics. Simultaneously, alignment and positioning structures are designed on the unit edges and connecting surfaces to simplify the assembly process and improve system stability.

[0043] The metasurface in this embodiment was validated by fixing a sound source at the center of the metasurface and arranging multiple sensors around it to measure the sound field. This verified the invention's ability to precisely control sound waves in multiple dimensions, as well as its robustness against external noise and reflected wave interference in complex environments. Furthermore, the metasurface maintains excellent acoustic and vibration control performance across multiple frequency bands, ensuring its wide applicability in practical applications.

[0044] like Figure 4 As shown, an acoustic-vibration-pressure field analysis was performed on the metasurface of this application. The middle three layers of the metasurface were twisted by 23° along the z-axis during the analysis. The results show that by adjusting the twist angle, unidirectional hyperbolic wave propagation occurred in the zx plane of the metasurface, highly concentrated low-loss channelized propagation occurred in the xy plane, and wave localization occurred in the yz plane. The metasurface exhibited three types of manipulated waves in three different spatial planes, indicating that the metasurface precisely intervened in wave propagation in high dimensions, achieving efficient control and uniform distribution. Comparing the system size and the length of the spatial wave propagation path also reveals that the metasurface is very small in size and highly efficient relative to the spatial range of influence, which is beneficial for its wide range of applications.

[0045] By adjusting the planar torsion of a 5×5×5 moiré metasurface, this invention can flexibly realize various acoustic and vibration modes, including channeled propagation, unidirectional hyperbolic wave propagation, and localized wave modes, providing richer and more diverse acoustic and vibration manipulation capabilities. This innovative control method effectively solves the adjustment limitations caused by the fixed interlayer distance in traditional metamaterial systems, enabling the system to have higher tunability and acoustic and vibration energy management capabilities.

[0046] like Figure 5 As shown, isofrequency curve analysis of a single 3D unit was performed using COMSOL Multiphysics software. The analysis results indicate that differences in resonant cavity volume, central cavity shape, and pipe connection length in the x, y, and z directions collectively lead to differences in resonant modes in these three directions, resulting in differences in acoustic impedance and anisotropy. This anisotropy leads to... Figure 5 The hyperbolic dispersion curves presented show that the dispersion lines change from the center to the edges. These hyperbolas indicate that the group velocity of the sound wave no longer diffuses outwards, but is instead influenced by anisotropy and propagates along the direction perpendicular to the hyperbola. The frequency range shown also reveals that wave propagation in the metasurface exhibits deep subwavelength characteristics.

[0047] In this embodiment, by designing and precisely controlling the dimensions, length, and structural parameters of the coupling pipes and coupling cavities in the x, y, and z directions, the system exhibits differentiated acoustic impedances in different directions, thus displaying hyperbolic dispersion characteristics (i.e., extreme anisotropy) in each plane dimension. Utilizing this characteristic, the propagation path and mode of sound waves can be flexibly controlled by adjusting the torsion angles of each layer or the distribution between units.

[0048] In this embodiment, a 5×5×5 layer Mohr system stacking strategy is adopted. This scheme successfully realizes a variety of wave behaviors, including channelized propagation, unidirectional hyperbolic propagation, and localized wave modes, demonstrating excellent control capabilities and broad application potential.

[0049] Based on the principle of nonlocal anisotropy, this application proposes a design scheme for realizing a three-dimensional acoustic-vibration moiré metasurface. This invention's three-dimensional acoustic-vibration moiré metasurface, while ensuring multi-dimensional acoustic vibration propagation control capabilities, achieves ultra-low-loss unidirectional channelization and localized acoustic vibration control, greatly improving the efficiency of energy transfer and vibration regulation. Based on the principle of nonlocal anisotropy, this system, through the rational design of the torsion angle, allows all dimensions to be transformed into "magic angles" with flat band characteristics, thereby breaking the dependence of traditional systems on a single torsion angle and expanding the degrees of freedom in acoustic vibration regulation.

[0050] This application employs a nonlocal design concept, connecting multiple three-dimensional units—specifically, the cross-connections between pipes and cavities—to allow energy to be freely transferred throughout the system, further enhancing the efficiency and flexibility of sound wave propagation control. Through this innovative design, the invention achieves excellent beam control capabilities without significantly increasing overall mass and volume. Furthermore, due to the hyperbolic acoustic dispersion characteristics, the system exhibits extreme anisotropy in multiple dimensions, realizing efficient and controllable sound wave propagation modulation across a wide frequency range.

[0051] Simultaneously considering the anisotropy principle, the shape of the central resonant cavity, the volume of the coupling cavity, and the length of the coupling pipe, the system exhibits unique directional selectivity in different directions, resulting in significant differences in acoustic impedance in the three directions, thus successfully achieving extreme anisotropy.

[0052] This invention offers advantages such as flexible structural design, strong controllability, and high scalability. Furthermore, by optimizing the interlayer coupling mechanism and adjusting the parameters of the coupling tube, the energy transmission and acoustic vibration control processes of the system are made more stable, reducing energy loss and enhancing the unidirectional and localized acoustic vibration isolation effect. The innovative nature of this technology makes it promising for applications in high-precision vibration control, energy transfer, subwavelength wave manipulation, and high-sensitivity sensing, providing a new solution for the further development of wave and vibration control technologies.

[0053] The above examples are only used to illustrate the feasibility and practical operation of the present invention and are not intended to limit the invention. Within the scope of knowledge possessed by those skilled in the art, corresponding adjustments and optimizations can be made without departing from the core concept of the present invention. Through the above design and adjustable methods, the present invention successfully realizes a three-dimensional metasurface structure that combines extreme anisotropic dispersion, flexible torsional control, and multi-frequency acoustic vibration adaptation, which can be widely used in multiple fields such as acoustic imaging, acoustic cloaking, and ultrasonic sensing, providing an innovative solution for the research and application of acoustic and vibration metasurfaces.

Claims

1. A three-dimensional acoustic-vibration moiré metasurface constructed using the principle of nonlocal anisotropy, characterized in that, The structure is a three-dimensional structure composed of several three-dimensional units stacked along the x, y, and z directions. All three-dimensional units on each plane of the three-dimensional structure can be twisted around a central axis perpendicular to that plane by a set angle. The spacing between the planes of the three-dimensional structure can be changed. Each three-dimensional unit includes a central resonant cavity, and each of the six end faces of the central resonant cavity is provided with a coupling pipe. The ends of the coupling pipes are provided with coupling cavities. The coupling pipes and coupling cavities on the symmetrical end faces of the central resonant cavity are the same. The structure also includes a point sound source, which is placed at the center of the three-dimensional structure.

2. The three-dimensional acoustic-vibration moiré metasurface constructed using the principle of nonlocal anisotropy according to claim 1, characterized in that, The length of the coupling pipe, the volume of the coupling cavity, and the corresponding end face area of ​​the central resonant cavity on the three symmetrical end faces of the central resonant cavity must each have at least one different parameter.

3. A three-dimensional acoustic-vibration moiré metasurface constructed using the principle of nonlocal anisotropy according to claim 1, characterized in that, The coupling pipe and coupling cavity are hollow structures, and the diameter of the coupling pipe is 1mm to 4mm.

4. A three-dimensional acoustic-vibration moiré metasurface constructed using the principle of nonlocal anisotropy according to claim 1, characterized in that, The coupling pipe and coupling cavity are made of lightweight solid material.

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