A metamaterial vibration energy harvester based on a counter-helical acoustic black hole structure

Abstract

This invention discloses a metamaterial vibration energy harvester based on an anti-spiral acoustic black hole structure, comprising an anti-spiral acoustic black hole structure, an extended mass block, and a piezoelectric structure. The anti-spiral acoustic black hole structure includes an ABH beam and an extended beam. The ABH beam is bent into an Archimedean spiral shape, with its thickness gradually decreasing from the starting end to the terminal end. The extended beam extends outward from the terminal end of the ABH beam, and its thickness is the same as the minimum thickness of the ABH beam. The piezoelectric structure is disposed on the extended beam, and the extended mass block is combined with the end of the extended beam. This invention breaks through the conventional approach of using large-size acoustic black holes to deal with low-frequency vibrations. It is not only suitable for space-constrained scenarios, but also achieves a longer effective wave propagation path within the same space, enhancing energy focusing or dissipation effects. While maintaining high-frequency performance, it also has the ability to capture mid- and low-frequency vibrations, achieving efficient energy harvesting.

Description

Technical Field

[0001] This invention relates to the technical field of vibration energy harvesting, specifically to a metamaterial vibration energy harvester based on an anti-helical acoustic black hole structure. Background Technology

[0002] The rapid proliferation of IoT networks and smart sensing systems—particularly in demanding environments such as wearable electronics, aerospace systems, and industrial condition monitoring—has exposed serious limitations of traditional battery technology, including limited lifespan, maintenance complexity, and poor sustainability. Therefore, vibration energy harvesting (VEH), which enables autonomous operation by converting environmental mechanical energy, has become a cutting-edge research area for sustainable power solutions. However, effectively harvesting broadband, low-amplitude vibration energy remains a significant challenge, especially in miniaturized applications where power density and spectral adaptability are crucial.

[0003] Contemporary VEH (Vehicle Energy Harnessing) technology primarily employs three transduction mechanisms: electromagnetic (Faraday induction), electrostatic (capacitive coupling), and piezoelectric (strain-polarization coupling) principles. While electromagnetic systems demonstrate effectiveness in low-frequency, large-displacement excitation, their practical applications are susceptible to excessively high mass density and electromagnetic interference sensitivity. Although electrostatic collectors offer the advantage of compact structure, their operation relies on an external polarization voltage source, and their insufficient power density makes them unsuitable for industrial applications. In contrast, piezoelectric conversion utilizes the direct piezoelectric effect to transform mechanical strain into charge displacement, making it the preferred choice for self-powered microsystems.

[0004] Traditional piezoelectric collectors generally employ cantilever beam structures, flexible designs, or multi-stage composite architectures. However, their practical application performance is limited by the ultra-narrow operating bandwidth caused by the linear resonance mechanism (the effective bandwidth is typically less than 10Hz at a reference frequency of 1000Hz). This limitation significantly weakens the adaptability of energy harvesting systems to broadband vibrational spectra and time-varying dynamics under actual operating conditions. However, recent advances in acoustic black hole (ABH) structures have achieved a paradigmatic breakthrough. Their unique waveguide design not only breaks through the bandwidth limitations of traditional methods but also achieves subwavelength focusing and precise localization of flexural wave energy across a wide frequency range.

[0005] Existing acoustic black hole structures are typically designed to exceed 500 mm in length to minimize reflections caused by truncation. For example, Chinese patent CN118413131A discloses a metamaterial beam vibration energy harvester that combines an acoustic black hole, which includes a vibration structure, a main beam, an additional acoustic black hole beam, and a piezoelectric structure. The length of the main beam exceeds 550 mm, which results in low space efficiency and severely restricts the miniaturization integration requirements of wearable devices.

[0006] While traditional acoustic black hole structures exhibit excellent energy focusing characteristics in high-frequency vibration control, their performance in the mid-to-low frequency range is significantly limited. At lower cutoff frequencies, long-wavelength vibration waves, due to physical size constraints and insufficient waveguide paths, are difficult to effectively compress and focus, leading to a sharp attenuation of energy density in the low-frequency region (e.g., 100-1500Hz). This phenomenon directly manifests as dispersed stress distribution and reduced strain energy density at the piezoelectric conversion terminals, thereby weakening the efficiency of low-frequency vibration energy harvesting.

[0007] In summary, there is an urgent need in this field for a compact broadband energy harvester that can be used to harvest energy in space-constrained applications while achieving enhanced high-efficiency energy harvesting at low and medium frequencies. Summary of the Invention

[0008] This invention addresses the shortcomings of existing technologies by providing a metamaterial vibration energy harvester based on an anti-spiral acoustic black hole structure.

[0009] To achieve the above objectives, the technical solution of the present invention is as follows:

[0010] A metamaterial vibration energy harvester based on an anti-helical acoustic black hole structure includes an anti-helical acoustic black hole structure, an extended mass block, and a piezoelectric structure. The anti-helical acoustic black hole structure includes an ABH beam and an extended beam. The ABH beam is bent into an Archimedean spiral shape, with its thickness gradually decreasing from the starting end to the terminal end. The extended beam extends outward from the terminal end of the ABH beam, and its thickness is the same as the minimum thickness of the ABH beam. The piezoelectric structure is disposed on the extended beam, and the extended mass block is connected to the end of the extended beam.

[0011] Optionally, the Archimedean spiral shape of the ABH beam is described as r = a + bθ, where the initial radius a and the pitch parameter b define the Archimedean spiral geometry, and θ = 0.

[0012] Optionally, the thickness h(x) of the ABH beam along the x-direction follows a power law with an exponent, h(x) = ax. n With (n≥2) changes, the thickness transition becomes sufficiently smooth.

[0013] Optionally, the anti-helical acoustic black hole structure further includes a non-ABH beam, which is connected to the starting end of the ABH beam and has the same thickness as the starting end of the ABH beam.

[0014] Optionally, the thickness variation formula of the anti-helical acoustic black hole structure is as follows:

[0015]

[0016] Where h0 corresponds to the uniform thickness of the non-ABH beam, h t Corresponding to the minimum thickness of the extended beam, l1, l ABH l2 and l2 correspond to the lengths of the non-ABH beam, ABH beam, and extended beam, respectively.

[0017] Optionally, the widths of the non-ABH beams, ABH beams, and extended beams are uniform.

[0018] Optionally, the extended mass block is connected to the end of the extended beam by mechanical connection or integral molding, wherein the center of gravity of the extended mass block coincides with the end of the waveguide path of the anti-helical acoustic black hole structure.

[0019] Optionally, the piezoelectric structure is a piezoelectric ceramic patch attached to the back of the extension beam.

[0020] Optionally, the length of the piezoelectric ceramic patch is less than half the minimum operating wavelength of the terminal.

[0021] Optionally, the piezoelectric structure is provided with an external electrode, which is electrically connected to a load integrated on a terminal block.

[0022] The beneficial effects of this invention are as follows:

[0023] 1. This invention, through the design of a spiral acoustic black hole structure, "compresses" the wave propagation path of traditional linear or planar acoustic black holes into a smaller space, breaking through the conventional approach of using large-size acoustic black holes to deal with low-frequency vibrations. It is not only suitable for space-constrained scenarios, but also achieves a longer effective wave propagation path in the same space, enhancing the energy focusing or dissipation effect.

[0024] 2. This invention significantly reduces the size dependence of the energy harvesting terminal (l2) by employing an anti-spiral layout of the acoustic black hole, while also providing the terminal with modular expansion compatibility. Previous spiral acoustic black hole structures had high space requirements for the installation of internal components, but the reverse configuration greatly improves space efficiency and facilitates integration with complex vibration energy harvesting systems without affecting energy conversion performance.

[0025] 3. By integrating a mass block into the piezoelectric end to form a cantilever piezoelectric structure, targeted frequency band enhancement can be achieved.

[0026] Moreover, it can precisely adjust the system's resonant frequency, optimize the stress distribution on the tablet, and maximize strain energy.

[0027] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the overall structure of the vibration energy harvester disclosed in Embodiment 1 of the present invention;

[0029] Figure 2 This is a schematic diagram of the anti-helical acoustic black hole structure of the vibration energy harvester disclosed in Embodiment 1 of the present invention;

[0030] Figure 3 This is a schematic diagram of the parameters of the vibration energy harvester disclosed in Embodiment 1 of the present invention from another angle;

[0031] Figure 4 This is a schematic diagram of the installation of the piezoelectric structure of the vibration energy harvester disclosed in Embodiment 1 of the present invention;

[0032] Figure 5 This is a schematic diagram of the conventional linear ABH beam energy harvester in Comparative Example 1.

[0033] Figure 6 This is a schematic diagram comparing the piezoelectric power harvesting performance in the low-to-mid frequency band of Embodiment 1 and Comparative Example 1 of the present invention.

[0034] The diagram is labeled as follows: 1. Extended mass block, 2. Piezoelectric structure, 3. Anti-helical acoustic black hole structure, 301. Non-ABH beam, 302. ABH beam, 303. Extended beam. Detailed Implementation

[0035] The present invention will be explained and described in more detail below with reference to specific embodiments. These descriptions are for illustrative purposes only and are not intended to limit the scope of the invention. It should be noted that the following embodiments are for illustrative purposes only and are not intended to limit the technical solutions described herein. All technical solutions and improvements that do not depart from the scope of this invention should be included within the scope of the claims of this invention.

[0036] refer to Figures 1 to 3The metamaterial vibration energy harvester based on the anti-helical acoustic black hole structure in this embodiment includes an extended mass block 1, a piezoelectric structure 2, and an anti-helical acoustic black hole structure 3. The anti-helical acoustic black hole structure 3 consists of a non-ABH beam 301, an ABH beam 302, and an extended beam 303. The ABH beam 302 is bent into an Archimedean spiral shape, with its thickness gradually decreasing from the starting end to the end. The extended beam 303 extends outward from the end and has the minimum thickness of the ABH beam 302. The non-ABH beam 301 is connected to the starting end and has the maximum thickness of the ABH beam 302. The piezoelectric structure 2 covers the extended beam 303 of the anti-helical acoustic black hole structure 3. Its electrodes are connected to a load integrated on a terminal block via copper foil and wires. The extended mass block 1 is mechanically connected or integrally molded to the end of the extended beam 303, so that the center of gravity of the extended mass block 1 coincides with the end of the waveguide path of the anti-helical acoustic black hole structure 3, thereby ensuring that the inertial force acts directly on the strain concentration region of the piezoelectric structure 2.

[0037] ABH beam 302 has a thickness distributed according to a power law, h(x) = ax n A thin plate with n≥2 is bent into an Archimedean spiral shape, specifically described as r=a+bθ, where the initial radius a=30mm and the pitch parameter b=10 / πmm define the geometry of the Archimedean spiral, θ=0 defines the maximum thickness at the spiral's starting point, and the spiral's radius of curvature gradually increases from the inside out. When a wave enters the region of ABH beam 302, the wavelength reaches its maximum value, while the bending radius reaches its minimum value, causing the anti-spiral ABH beam 302 to exhibit a higher wavelength-to-curvature ratio in the initial region, resulting in more pronounced wavefront distortion. The anti-spiral structure achieves an equivalent extension of the wave propagation path (total effective length l) through the Archimedean spiral equation r(θ)=a+bθ. ABH =400mm), while the lateral projection size is reduced by 77.3% (straight beam is 440mm), which allows long-wavelength low-frequency waves (100-1500Hz) to undergo multiple reflections and focusing in the helical path, significantly improving energy density. The anti-helical structure not only maintains the equivalent performance of the classic helical design, but also frees up space for the piezoelectric ends.

[0038] The extended beam 303 is a straight structure with uniform thickness. It extends outward tangentially to the end of the ABH beam 302, achieving a smooth transition. Extending the end structure l2 further increases the energy harvesting efficiency in the mid-to-low frequency range. Due to manufacturing limitations and truncation effects of the actual ABH beam 302, energy concentration always occurs near the truncated end, rather than the idealized end. Extending l2 can redistribute stress onto the piezoelectric patch, thereby significantly improving the energy conversion efficiency in this range.

[0039] The non-ABH beam 301 is a straight structure with a uniform thickness. It extends outwards tangentially to the starting end of the ABH beam 302, achieving a smooth transition. Its function is to provide a uniformly thick foundation support for the anti-helical acoustic black hole structure. As the starting segment of the structure, the non-ABH beam 301 is usually directly connected to the fixed end (such as the support frame or vibration source) to ensure the stable installation of the entire ABH beam and the extension beam. Its uniform thickness provides the necessary rigidity and strength, preventing the overall structure from becoming fragile due to the tapering design of the ABH beam. Vibration waves are transmitted from the uniform segment of the non-ABH beam 301 to the tapering region of the ABH beam 302. This transition segment optimizes the wave transmission path through smooth geometric connections (such as the power-law distribution starting point), reducing reflection or energy loss and ensuring that vibration energy enters the ABH region efficiently.

[0040] Combination Figure 4 The piezoelectric structure 2 is a PZT-5H piezoelectric ceramic attached to the extended beam 303 of the anti-helical acoustic black hole structure 3. The electrodes are connected to a 10kΩ load resistor via copper foil. The piezoelectric structure 2 converts mechanical strain into charge output through the direct piezoelectric effect. To minimize charge cancellation caused by simultaneous peak and valley deformation, the length of the piezoelectric patch must be kept less than half the minimum operating wavelength. If the piezoelectric patch length exceeds half the wavelength, the wave will simultaneously undergo tensile and compressive deformation at different positions on the patch (i.e., wave crests and troughs coexist), causing positive and negative charges to cancel each other out, significantly reducing the output voltage and energy conversion efficiency. Keeping the piezoelectric patch length less than half the minimum operating wavelength ensures that the vibration wave phase is consistent within the area covered by the patch, maximizing the efficiency of strain energy conversion into charge.

[0041] Extended mass block 1 is fixedly installed at the end region of extended beam 303. The addition of the mass block reduces system resonance and matches it with low-frequency vibrations in the environment. The inertial force of extended mass block 1 concentrates strain energy into piezoelectric structure 2, achieving an 83.7% peak power enhancement and a 53-fold valley power amplification through geometric impedance matching.

[0042] Example 1

[0043] The structure of the metamaterial vibration energy harvester based on the anti-helical acoustic black hole structure in Example 1 is as described above. Its anti-helical acoustic black hole structure 3 is made of metallic iron, and the geometric parameters, material parameters, and piezoelectric ceramic sheet parameters are shown in Tables 1, 2, and 3, respectively.

[0044] Table 1 Geometric parameters of the vibration energy harvester

[0045]

[0046] Where h0 represents the thickness of non-ABH beam 301, h t h represents the thickness of the extended beam 303. mThe thickness of the extended mass block is represented by l, and the length of the non-ABH beam 301 is represented by l. ABH l1 represents the effective length of beam 302 (ABH), l2 represents the length of extended beam 303, l3 represents the length of extended mass block, and B represents the width of vibration energy harvester.

[0047] Table 2 Material parameters of the vibration energy harvester

[0048]

[0049] Table 3 Parameters of Piezoelectric Ceramic Sheets

[0050]

[0051] Among them l p h represents the length of the piezoelectric ceramic sheet. p B represents the thickness of the piezoelectric ceramic sheet, and B represents the width of the piezoelectric ceramic sheet.

[0052] Comparative Example 1

[0053] This comparative example provides a conventional linear ABH beam energy harvester, such as Figure 5 As shown, its energy harvesting efficiency is consistent with the established benchmark of similar configurations. The difference from Example 1 is that it is a linear ABH beam without helical curling and extended mass blocks. The other geometric parameters, material parameters and piezoelectric ceramic sheet parameters are the same.

[0054] The piezoelectric power harvesting performance of the metamaterial vibration energy harvester based on the anti-helical acoustic black hole and cantilever beam in Example 1 is compared with that of the conventional linear ABH beam energy harvester in Comparative Example 1.

[0055] Figure 6 The comparison of piezoelectric power harvesting performance between Example 1 and Comparative Example 1 shows that the metamaterial vibration energy harvester based on an anti-helical acoustic black hole and a cantilever beam reduces the projection axial length by 77% while maintaining broadband efficiency. The average power of the SABH-ETMS is 2.7 × 10⁻⁶ Hz in the 100-1500 Hz range. -3 W, compared to traditional designs (1.9×10 - 4 W) increased by 14.2 times. It is worth noting that the peak power output (7.1 × 10⁻⁶) -2 W) appears at 304Hz, compared to the traditional linear ABH (3.1×10 at 800Hz). -3 Compared to the traditional linear ABH beam energy harvester, the low-frequency response is enhanced, and the peak power is increased by 22.9 times. Compared to the traditional linear ABH beam energy harvester, the energy harvester proposed in this embodiment expands the operating bandwidth and enhances the energy harvesting capability for mid- and low-frequency vibrations.

[0056] The metamaterial vibration energy harvester based on an anti-helical acoustic black hole structure proposed in this invention exhibits significantly superior performance in capturing mid-to-low frequency vibrations compared to traditional linear ABH beams. While maintaining high-frequency performance (power output at >1500Hz is comparable), it increases the average power output in the mid-to-low frequency band by 14.2 times, with a 1000% increase in power density and a 22.9-fold increase in peak power in the 200-600Hz band, and also demonstrates superior spatial efficiency (lateral dimensions reduced by 77%).

[0057] The above are merely specific embodiments of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial modifications made to the present invention using this concept shall be considered as infringing upon the protection scope of the present invention.

Claims

1. A metamaterial vibration energy harvester based on an anti-spiral acoustic black hole structure, characterized in that: This includes anti-spiral acoustic black hole structures, extended mass blocks, and piezoelectric structures; The anti-helical acoustic black hole structure includes an ABH beam, a non-ABH beam, and an extended beam. The ABH beam is composed of thin plates with a power-law thickness, bent into an Archimedean spiral shape, with the thickness gradually decreasing from the starting end to the end, and the radius of curvature gradually increasing from the inside to the outside. The non-ABH beam is connected to the starting end of the ABH beam and has the same thickness as the starting end of the ABH beam. The extended beam extends outward in a manner tangential to the end of the ABH beam and achieves a smooth transition. The extended beam is a straight structure with a uniform thickness, and its thickness is the same as the minimum thickness of the ABH beam. The piezoelectric structure is a piezoelectric ceramic patch attached to the back of the extension beam; the length of the piezoelectric ceramic patch is less than half of the minimum operating wavelength of the terminal. The extended mass block is connected to the end of the extended beam, and the center of gravity of the extended mass block coincides with the end of the waveguide path of the anti-helical acoustic black hole structure.

2. The metamaterial vibration energy harvester based on an anti-spiral acoustic black hole structure according to claim 1, characterized in that: The Archimedean spiral shape of the ABH beam is described as follows: , where the initial radius and pitch parameters The geometry of the Archimedean spiral was defined. The maximum thickness is defined at the starting end of the spiral.

3. The metamaterial vibration energy harvester based on an anti-helical acoustic black hole structure according to claim 1, characterized in that: The thickness of the ABH beam along The direction follows a power law with an exponent. change.

4. The metamaterial vibration energy harvester based on an anti-spiral acoustic black hole structure according to claim 1, characterized in that: The formula for the thickness variation of the anti-spiral acoustic black hole structure is: ， in Corresponding to the uniform thickness of the non-ABH beam, Corresponding to the minimum thickness of the extended beam, , and These correspond to the lengths of the non-ABH beam, ABH beam, and extended beam, respectively.

5. The metamaterial vibration energy harvester based on an anti-spiral acoustic black hole structure according to claim 4, characterized in that: The widths of the non-ABH beams, ABH beams, and extended beams are all uniform.

6. The metamaterial vibration energy harvester based on an anti-spiral acoustic black hole structure according to claim 1, characterized in that: The extended mass block is connected to the end of the extended beam via mechanical connection or integral molding.

7. The metamaterial vibration energy harvester based on an anti-spiral acoustic black hole structure according to claim 1, characterized in that: The piezoelectric structure is provided with an external electrode, which is electrically connected to a load integrated on a terminal block.

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