Folding piezoelectric vibration energy collector

Abstract

The invention discloses a foldable piezoelectric vibration energy collector, and the collector comprises a cantilever beam which is provided with a fixed end at one end and a free end at the other end; the mass block is located below the cantilever beam, fixedly connected with the free end and used for adjusting the resonant frequency of the cantilever beam; the piezoelectric element is arranged on the cantilever beam; when the cantilever beam vibrates in the vertical direction, the piezoelectric element generates electric energy; the electric energy collecting element is electrically connected with the piezoelectric element and is used for collecting the electric energy; wherein the piezoelectric element comprises a plurality of piezoelectric layers, the plurality of piezoelectric layers are distributed at intervals in the vertical direction and are arranged in parallel, and every two adjacent piezoelectric layers are fixedly connected. Under the condition that a larger mass block or a longer cantilever beam does not need to be arranged, the energy conversion efficiency of the piezoelectric vibration energy collector in an ultralow-frequency vibration environment can be improved, and the miniaturization and wearable requirements of devices or electronic equipment can be met.

Description

Technical Field

[0001] The present invention relates to the technical field of vibration energy harvesting, and particularly to a foldable piezoelectric vibration energy harvester. Background Art

[0002] With the rapid development of Micro-Electro-Mechanical System (MEMS) technology, piezoelectric vibration energy harvesters, as devices that can convert ambient vibration energy into electrical energy, are widely used in the fields of electronic devices such as wireless sensor networks, Internet of Things devices, and smart wearable devices. Especially in ultra-low frequency vibration environments with frequencies below 10 Hz (such as human motion, slow vibration of industrial equipment, or health monitoring of building structures), achieving efficient energy harvesting is of great significance for improving the working efficiency of the device's self-powered system.

[0003] Currently, piezoelectric vibration energy harvesters usually adopt a cantilever beam structure, which has a relatively high natural frequency (usually between dozens of hertz and hundreds of hertz), making it difficult to effectively match the ultra-low frequency ambient vibration with frequencies below 10 Hz, resulting in low energy conversion efficiency.

[0004] Existing piezoelectric vibration energy harvesters reduce the resonance frequency by setting a larger mass block or a longer cantilever beam, etc., so as to match the ultra-low frequency ambient vibration; however, these measures will also lead to a relatively large overall size of the piezoelectric vibration energy harvester, making it difficult to meet the miniaturization and wearable requirements of the device or the above-mentioned electronic devices. Therefore, it is necessary to adjust the structure of the piezoelectric vibration energy harvester.

[0005] The statements here only provide background art related to the present invention and do not necessarily constitute prior art. Summary of the Invention

[0006] The object of the present invention is to provide a foldable piezoelectric vibration energy harvester, which can improve the energy conversion efficiency of the piezoelectric vibration energy harvester in ultra-low frequency vibration environments without setting a larger mass block or a longer cantilever beam, and can also meet the miniaturization and wearable requirements of the device or electronic devices.

[0007] To achieve the above object, the present invention is realized through the following technical solutions:

[0008] A foldable piezoelectric vibration energy harvester, comprising:

[0009] A cantilever beam, one end of which is a fixed end and the other end is a free end;

[0010] A mass block, located below the cantilever beam and fixedly connected to the free end, for adjusting the resonance frequency of the cantilever beam;

[0011] A piezoelectric element is disposed on the cantilever beam; when the cantilever beam vibrates in the vertical direction, the piezoelectric element generates electrical energy;

[0012] An electrical energy collection element is electrically connected to the piezoelectric element and is used to collect the electrical energy;

[0013] Wherein, the piezoelectric element includes a plurality of piezoelectric layers, and the plurality of piezoelectric layers are spaced apart in the vertical direction and arranged in parallel, and two adjacent piezoelectric layers are fixedly connected.

[0014] Optionally, the number of the piezoelectric layers is two; the ends of the two piezoelectric layers close to the free end are fixedly connected or the ends close to the fixed end are fixedly connected.

[0015] Optionally, the number of the piezoelectric layers is greater than or equal to three, and all the piezoelectric layers are divided into a plurality of piezoelectric layer groups in the vertical direction; each piezoelectric layer group includes two adjacent piezoelectric layers, and the same piezoelectric layer is included in two adjacent piezoelectric layer groups;

[0016] In two adjacent piezoelectric layer groups, the two piezoelectric layers of one piezoelectric layer group are fixedly connected at the ends close to the free end, and the two piezoelectric layers of the other piezoelectric layer group are fixedly connected at the ends close to the fixed end.

[0017] Optionally, the material of the piezoelectric element is aluminum nitride.

[0018] Optionally, the thickness of the piezoelectric layer is 1 μm to 1.5 μm.

[0019] Optionally, the electrical energy collection element includes:

[0020] A first metal layer is disposed on the upper surface of the piezoelectric element and serves as an upper electrode;

[0021] A second metal layer is disposed on the upper surface of the cantilever beam and serves as a lower electrode; and the lower electrode and the upper electrode cooperate to collect the electrical energy generated by the piezoelectric element.

[0022] Optionally, the piezoelectric element is polarized in the vertical direction.

[0023] Optionally, the material of the cantilever beam is a conductive material.

[0024] Optionally, an insulating layer is provided between the mass block and the cantilever beam.

[0025] Optionally, the material of the insulating layer is silicon dioxide.

[0026] Compared with the prior art, the present invention has at least one of the following advantages:

[0027] A foldable piezoelectric vibration energy harvester provided by the present invention, the piezoelectric element disposed on the cantilever beam includes a plurality of piezoelectric layers, the plurality of piezoelectric layers are spaced apart and arranged in parallel in the vertical direction, and two adjacent piezoelectric layers are fixedly connected; that is, the piezoelectric element is of a foldable structure. In the present invention, the structure of the piezoelectric element is innovatively designed, which can improve the energy conversion efficiency of the piezoelectric vibration energy harvester in an ultra-low frequency vibration environment. At the same time, there is no need to set a larger mass block or a longer cantilever beam, which can effectively reduce the volume of the device, realize miniaturization, and meet the space requirements of small devices such as wearable devices and wireless body area networks (WBANs).

[0028] The piezoelectric element of the present invention is of a foldable structure, which can cope with motion or vibration environments with different resonant frequency bands, enhances the adaptability of the piezoelectric vibration energy harvester, enables the piezoelectric vibration energy harvester to have broadband or multi-band characteristics, and thus can perform effective energy conversion in different frequency ranges.

[0029] The piezoelectric element of the present invention is of a foldable structure, which also increases the working area of the piezoelectric element to optimize the stress distribution of the piezoelectric material, increases the effective utilization rate of the piezoelectric material, and effectively improves the energy conversion efficiency of the piezoelectric element and the piezoelectric vibration energy harvester.

[0030] The present invention significantly improves the energy harvesting efficiency in a low-frequency vibration environment, meets the requirements of miniaturization, high adaptability and high power density, and has strong application prospects and competitive advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a cross-sectional view of a foldable piezoelectric vibration energy harvester provided by an embodiment of the present invention;

[0032] Figure 2 is a cross-sectional view of a foldable piezoelectric vibration energy harvester provided by another embodiment of the present invention;

[0033] Figure 3 is a front view of a foldable piezoelectric vibration energy harvester provided by an embodiment of the present invention;

[0034] Figure 4 is a rear view of a foldable piezoelectric vibration energy harvester provided by an embodiment of the present invention;

[0035] Figure 5 is a top view of a foldable piezoelectric vibration energy harvester provided by another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0036] The following further elaborates on a foldable piezoelectric vibration energy harvester proposed by the present invention in conjunction with the accompanying drawings and specific embodiments. According to the following description, the advantages and features of the present invention will be clearer. It should be noted that the accompanying drawings are in a very simplified form and all use non-precise scales, only for conveniently and clearly assisting in explaining the purpose of the embodiments of the present invention. In order to make the purpose, features, and advantages of the present invention more obvious and understandable, please refer to the accompanying drawings. It should be known that the structures, scales, sizes, etc. shown in the drawings of this specification are only used to cooperate with the content disclosed in the specification for those familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention. Therefore, they do not have a substantial technical meaning. Any modification of the structure, change in the proportional relationship, or adjustment of the size, without affecting the efficacy that the present invention can produce and the purpose that can be achieved, should still fall within the scope covered by the technical content disclosed by the present invention.

[0037] Combined with the attached Figures 1 to 5 As shown, this embodiment provides a foldable piezoelectric vibration energy harvester, including: a cantilever beam 110, a mass block 120, a piezoelectric element 130, and an electric energy collection element 140. One end of the cantilever beam 110 is a fixed end 1101, and the other end is a free end 1102. The mass block 120 is located below the cantilever beam 110 and is fixedly connected to the free end 1102 for adjusting the resonant frequency of the cantilever beam 110. The piezoelectric element 130 is disposed on the cantilever beam 110; when the cantilever beam 110 vibrates in the vertical direction, the piezoelectric element 130 generates electric energy. The electric energy collection element 140 is electrically connected to the piezoelectric element 130 for collecting the electric energy.

[0038] Specifically, the fixed end 1101 of the cantilever beam 110 is installed on a carrier 100; and when the cantilever beam 110 is subjected to an external vibration excitation, the free end 1102 of the cantilever beam 110 will vibrate in the vertical direction (such as Figure 1 the A-A direction shown) so that the cantilever beam 110 undergoes bending deformation, thereby driving the piezoelectric element 130 to deform and trigger the piezoelectric effect, and further enabling the piezoelectric element 130 to generate the electric energy, realizing the conversion from mechanical vibration to electric energy. More specifically, the mass block 120 disposed at the free end 1102 can adjust the resonant frequency of the cantilever beam 110, so that the cantilever beam 110 can still undergo bending deformation when the external vibration frequency is relatively low, thereby enabling the piezoelectric element 130 to still generate the electric energy. Optionally, the thickness of the cantilever beam 110 is 8 μm to 15 μm to enable the cantilever beam 110 to have better load-bearing capacity; preferably, the thickness of the cantilever beam 110 is 10 μm, but the present invention is not limited thereto.

[0039] As described in the background art section, in an ultra-low frequency vibration environment with a frequency lower than 10 Hz, using a conventional mass block can no longer meet the requirement of adjusting the resonant frequency of the cantilever beam. Measures such as setting a larger mass block or a longer cantilever beam are needed to reduce the resonant frequency of the cantilever beam to ensure the conversion efficiency from mechanical vibration to electrical energy. However, these measures are contradictory to the requirements of miniaturization and wearability of the device or electronic equipment.

[0040] To address the above problems, in this embodiment, an innovative design is made to the structure of the piezoelectric element 130 to improve the energy conversion efficiency of the piezoelectric vibration energy harvester in an ultra-low frequency vibration environment, and at the same time, there is no need to set a larger mass block or a longer cantilever beam, which can meet the requirements of miniaturization and wearability of the device or electronic equipment.

[0041] Specifically, in this embodiment, as Figure 1 and Figure 2 shown, the piezoelectric element 130 disposed on the cantilever beam 110 includes a plurality of piezoelectric layers 1301. The plurality of piezoelectric layers 1301 are spaced apart and arranged in parallel in the vertical direction (such as the A-A direction shown in Figure 1 ); and two adjacent piezoelectric layers 130 are fixedly connected. That is to say, in this embodiment, the piezoelectric element 130 has a folded structure, and the piezoelectric element 130 and the cantilever beam 110 together form a folded cantilever beam structure.

[0042] Compared with the piezoelectric element having only a single-layer structure in the prior art, the piezoelectric element 130 in this embodiment has a folded structure, which increases the number of piezoelectric layers 1301 in a limited space, making the piezoelectric element 130 have a larger mass and a larger working area, and at the same time making the cantilever beam 110 provided with the piezoelectric element 130 have a lower system stiffness; in this way, both the resonant frequency of the cantilever beam 110 can be reduced and the energy conversion efficiency of the piezoelectric element 130 can be improved, so that the piezoelectric vibration energy harvester can better adapt to ultra-low frequency vibrations (such as human movement, low-frequency vibrations in the environment, etc.) and effectively improve the energy conversion efficiency of the piezoelectric vibration energy harvester in an ultra-low frequency vibration environment.

[0043] Optionally, the material of the piezoelectric element 130 is aluminum nitride (AlN), which can not only ensure that the piezoelectric element 130 has a high piezoelectric coefficient, but also facilitate microfabrication of the piezoelectric element 130 (generally using the sol-gel method to form a film) to form a folded structure with a plurality of piezoelectric layers 1301.

[0044] Optionally, the thickness of the piezoelectric layer 1301 is 1 μm to 1.5 μm, so that the volume of the piezoelectric element 130 provided with a plurality of piezoelectric layers 1301 will not be too large, thereby meeting the requirements of miniaturization and wearability of the device or electronic equipment. Preferably, the thickness of the piezoelectric layer 1301 is 1.2 μm. The gap between two adjacent piezoelectric layers 1301 can be adjusted according to requirements and is not limited herein, as long as the requirements of miniaturization and wearability of the device or electronic equipment can be met.

[0045] Please continue to refer to Figure 1 , in one embodiment, the number of the piezoelectric layers 1301 is two; the ends of the two piezoelectric layers 1301 close to the free end 1102 are fixedly connected (as Figure 1 shown) or the ends of the two piezoelectric layers 1301 close to the fixed end 1101 are fixedly connected, so that the piezoelectric element 130 has a folded structure; it can be understood that in this case, the piezoelectric element 130 is generally U-shaped.

[0046] Please continue to refer to Figure 2 , in another embodiment, the number of the piezoelectric layers 1301 is greater than or equal to three, and all the piezoelectric layers 1301 are divided into a plurality of piezoelectric layer groups in the vertical direction; each piezoelectric layer group includes two adjacent piezoelectric layers 1301, and the same piezoelectric layer 1301 is included in two adjacent piezoelectric layer groups. Among two adjacent piezoelectric layer groups, the ends of the two piezoelectric layers 1301 of one piezoelectric layer group close to the free end 1102 are fixedly connected, and the ends of the two piezoelectric layers 1301 of the other piezoelectric layer group close to the fixed end 1101 are fixedly connected, so that the piezoelectric element 130 has a folded structure.

[0047] Specifically, as Figure 2 shown, the number of the piezoelectric layers 1301 is three, and the three piezoelectric layers 1301 can be divided into two piezoelectric layer groups in the vertical direction, which are respectively denoted as the first piezoelectric layer group 131 and the second piezoelectric layer group 132; among them, the first piezoelectric layer group 131 includes the piezoelectric layer 1301 at the bottom and the piezoelectric layer 1301 in the middle, and the second piezoelectric layer group 132 includes the piezoelectric layer 1301 in the middle and the piezoelectric layer 1301 at the top, that is, both the first piezoelectric layer group 131 and the second piezoelectric layer group 132 include the piezoelectric layer 1301 in the middle. More specifically, the ends of the piezoelectric layer 1301 at the bottom and the piezoelectric layer 1301 in the middle in the first piezoelectric layer group 131 close to the free end 1102 are fixedly connected, and the ends of the piezoelectric layer 1301 in the middle and the piezoelectric layer 1301 at the top in the second piezoelectric layer group 132 close to the fixed end 1101 are fixedly connected. In this case, the piezoelectric element 130 is generally S-shaped.

[0048] In other embodiments, in the piezoelectric element 130, the end portions of two adjacent piezoelectric layers 1301 are fixedly connected near the free end 1102; or the end portions of two adjacent piezoelectric layers 1301 are fixedly connected near the fixed end 1101; or the end portions of two adjacent piezoelectric layers 1301 are fixedly connected at the central position; in this case, the piezoelectric element 130 still has a folded structure.

[0049] It can be understood that the number of the piezoelectric layers 1301 does not exceed five to prevent the volume of the piezoelectric element 130 from being too large to meet the requirements of miniaturization and wearability of the device or electronic equipment.

[0050] Please continue to refer to Figure 1 and Figure 2 , the electric energy harvesting element 140 includes: a first metal layer 1401 disposed on the upper surface of the piezoelectric element 130 and serving as an upper electrode; and a second metal layer 1402 disposed on the upper surface of the cantilever beam 110 and serving as a lower electrode; and the lower electrode and the upper electrode cooperate to harvest the electric energy generated by the piezoelectric element 130.

[0051] It can be understood that the material of the cantilever beam 110 is a conductive material, so that the piezoelectric element 130 is electrically connected to the second metal layer 1402 through the cantilever beam 110, thereby enabling the electric energy harvesting element 140 to harvest the electric energy generated by the piezoelectric element 130. Optionally, the material of the cantilever beam 110 is doped silicon, and the doping element can be phosphorus P or boron B, and the doping concentration is not required, as long as the conductivity of the cantilever beam 110 is ensured to be good.

[0052] Specifically, the piezoelectric element 130 is polarized in the vertical direction so that the voltage direction generated by the piezoelectric element 130 is from top to bottom or from bottom to top, thereby ensuring that there is a voltage between the lower electrode and the upper electrode, and further enabling the harvesting of the electric energy.

[0053] Optionally, the materials of the first metal layer 1401 and the second metal layer 1402 are gold (Au), so that the first metal layer 1401 and the second metal layer 1402 have good conductivity to ensure the stability of the harvesting of the electric energy. Optionally, the thicknesses of the first metal layer 1401 and the second metal layer 1402 are 0.8 um to 1.2 um; preferably, the thicknesses of the first metal layer 1401 and the second metal layer 1402 are 1 um, but the present invention is not limited thereto.

[0054] Please continue to refer toFigure 1 and Figure 2 , an insulating layer 150 is provided between the mass block 120 and the cantilever beam 110 to electrically insulate the mass block 120 and the cantilever beam 110; and the cantilever beam 110 and the insulating layer 150 form a SOI (Silicon-On-Insulator) structure. Optionally, the material of the insulating layer 150 is silicon dioxide (SiO2); optionally, the thickness of the insulating layer 150 is 1.5 μm. Optionally, the material of the mass block 120 is silicon (Si), and the thickness of the mass block 150 is 400 μm, but the present invention is not limited thereto.

[0055] In addition, in some embodiments, as Figure 5 shown, on the same mass block 120, a plurality of the piezoelectric elements 130, the cantilever beams 110 corresponding to carry the piezoelectric elements 130, and the power collection elements 140 corresponding to be electrically connected to the piezoelectric elements 130 can be arranged side by side and form a series structure, further increasing the energy conversion efficiency of the piezoelectric vibration energy harvester.

[0056] Specifically, the plurality of cantilever beams 110, the plurality of piezoelectric elements 130, and the plurality of power collection elements 140 share the same mass block 120. Therefore, when the MEMS device vibrates, the voltage signals generated by the plurality of piezoelectric elements 130 have the same amplitude, frequency, and phase, and can be connected in series in a circuit, increasing the open-circuit voltage by multiple times (the multiple of increase is the same as the number of piezoelectric elements), thereby significantly improving the rectified power.

[0057] In addition, in some embodiments, the folded piezoelectric vibration energy harvester is fixed within a frame 210 (as Figure 3 shown) to facilitate installation in a device or an electronic device, but the present invention is not limited thereto.

[0058] Based on the same inventive concept, this embodiment also provides a method for manufacturing a foldable piezoelectric vibration energy harvester, including: Step S1, depositing a SiO2 insulating layer 201 (for example, with a thickness of 1.5 um) on a silicon substrate 200 (for example, a single crystal silicon with a thickness of 400 um). Step S2, depositing a doped silicon layer (for example, with a thickness of 10 um) on the SiO2 insulating layer. Step S3, patterning the silicon substrate, the SiO2 insulating layer, and the doped silicon layer to form a first patterned component and a second patterned component; and the first patterned component is a frame 210 and is composed of the silicon substrate and the SiO2 insulating layer, and the second patterned component is located inside the first patterned component and is composed of the silicon substrate, the SiO2 insulating layer, and the doped silicon layer. Step S4, deeply etching the second patterned component from the back of the silicon substrate according to a preset pattern, etching through the silicon substrate and the SiO2 insulating layer until the doped silicon layer is exposed (as Figure 4 shown); at this time, the unetched silicon substrate of the second patterned component forms the mass block 120, and the doped silicon layer forms the cantilever beam 110; Step S5, depositing or magnetron sputtering a plurality of AlN piezoelectric layers (for example, a total of 3, each piezoelectric layer with a thickness of 1.2 um, and the interlayer gap can be appropriately adjusted) in the vertical direction on the cantilever beam 110, and then patterning the AlN piezoelectric layers; since the AlN piezoelectric layer is a folded structure, repeat this step S5 until a plurality of AlN piezoelectric layers are grown; at this time, the grown plurality of AlN piezoelectric layers form the piezoelectric element 130. Step S6, continue to grow a Pad metal layer (selecting Au metal, 1 um), and then pattern the metal layer to form a first metal layer 1401 on the piezoelectric element 130 and a second metal layer 1402 on the cantilever beam 110, and the first metal layer 1401 and the second metal layer 1402 together form the electric energy collection element 140.

[0059] In summary, for the foldable piezoelectric vibration energy harvester provided in this embodiment, the piezoelectric element disposed on the cantilever beam includes a plurality of piezoelectric layers, the plurality of piezoelectric layers are spaced apart and arranged in parallel in the vertical direction, and two adjacent piezoelectric layers are fixedly connected; that is, the piezoelectric element is a folded structure. In this embodiment, the structure of the piezoelectric element is innovatively designed, which can improve the energy conversion efficiency of the piezoelectric vibration energy harvester in an ultra-low frequency vibration environment. At the same time, there is no need to set a larger mass block or a longer cantilever beam, which can effectively reduce the volume of the device, realize miniaturization, and meet the space requirements of small devices such as wearable devices and wireless body area networks (WBANs), that is, meet the requirements of miniaturization and wearability of the device or electronic equipment.

[0060] It should be noted that in this article, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of additional identical elements in the process, method, article or device comprising said element.

[0061] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "height", "thickness", "upper", "lower", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the present invention. In the description of the present invention, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0062] In the description of the present invention, unless otherwise clearly defined and limited, the terms "mounted", "connected", "coupled", "fixed" shall be construed broadly. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection, an electrical connection; it may be directly connected, or indirectly connected through an intermediate medium, and 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.

[0063] In the present invention, unless otherwise clearly defined and limited, the first feature being "above" or "below" the second feature may include direct contact between the first and second features, or may include the first and second features not being in direct contact but in contact through additional features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes the first feature being directly above and obliquely above the second feature, or merely indicating that the first feature has a higher horizontal height than the second feature. The first feature being "below", "beneath" and "underneath" the second feature includes the first feature being directly below and obliquely below the second feature, or merely indicating that the first feature has a lower horizontal height than the second feature.

[0064] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be recognized that the above description should not be construed as a limitation of the present invention. After those skilled in the art have read the above content, various modifications and alternatives to the present invention will be obvious. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims

1. A foldable piezoelectric vibration energy harvester, characterized in that: include: A cantilever beam (110), one end of which is a fixed end (1101) and the other end of which is a free end (1102); A mass block (120), located below the cantilever beam (110), fixedly connected to the free end (1102), and used to adjust the resonant frequency of the cantilever beam (110); A piezoelectric element (130) is disposed on the cantilever beam (110); when the cantilever beam (110) vibrates in a vertical direction, the piezoelectric element (130) generates electric energy; an electric energy collecting element (140), electrically connected to the piezoelectric element (130) and used for collecting the electric energy; The piezoelectric element (130) comprises a plurality of piezoelectric layers (1301), the plurality of piezoelectric layers (1301) are spaced apart and arranged in parallel along a vertical direction, and two adjacent piezoelectric layers (1301) are fixedly connected.

2. The foldable piezoelectric vibration energy harvester according to claim 1, characterized in that: The number of the piezoelectric layers (1301) is two; the two piezoelectric layers (1301) are fixedly connected at their ends close to the free end (1102) or at their ends close to the fixed end (1101).

3. The foldable piezoelectric vibration energy harvester according to claim 1, characterized in that: The number of the piezoelectric layers (1301) is greater than or equal to three, and all the piezoelectric layers (1301) are divided into a plurality of piezoelectric layer groups along the vertical direction; each of the piezoelectric layer groups includes two adjacent piezoelectric layers (1301), and the two adjacent piezoelectric layer groups include the same piezoelectric layer (1301); In two adjacent piezoelectric layer groups, the two piezoelectric layers (1301) of one piezoelectric layer group are fixedly connected at their ends close to the free end (1102), and the two piezoelectric layers (1301) of the other piezoelectric layer group are fixedly connected at their ends close to the fixed end (1101).

4. The foldable piezoelectric vibration energy harvester according to claim 1, characterized in that: The material of the piezoelectric element (130) is aluminum nitride.

5. The foldable piezoelectric vibration energy harvester according to claim 1, characterized in that: The thickness of the piezoelectric layer (1301) is 1 μm to 1.5 μm.

6. The foldable piezoelectric vibration energy harvester according to claim 1, characterized in that: The electric energy collection element (140) comprises: A first metal layer (1401), disposed on the upper surface of the piezoelectric element (130) and serving as an upper electrode; The second metal layer (1402) is arranged on the upper surface of the cantilever beam (110) and serves as a lower electrode; and the lower electrode and the upper electrode cooperate to collect the electric energy generated by the piezoelectric element (130).

7. The foldable piezoelectric vibration energy harvester according to claim 5, characterized in that: The piezoelectric element (130) is polarized in a vertical direction.

8. The foldable piezoelectric vibration energy harvester according to claim 5, characterized in that: The cantilever beam (110) is made of a conductive material.

9. The foldable piezoelectric vibration energy harvester according to claim 1, characterized in that: An insulating layer (150) is provided between the mass block (120) and the cantilever beam (110).

10. The foldable piezoelectric vibration energy harvester according to claim 9, characterized in that: The material of the insulating layer (150) is silicon dioxide.

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