Bistable AlN piezoelectric thick film vibration energy collector

Abstract

The invention provides a bistable AlN piezoelectric thick film vibration energy collector, and belongs to the technical field of piezoelectric energy collectors. Comprising a substrate, the substrate comprises a fixed end, a first free end, a second free end, an auxiliary beam and at least one pair of main beams, and the fixed end and the first free end are arranged at an interval; the fixed end is fixedly arranged relative to the ground; the auxiliary beam is arranged in a gap between the fixed end and the first free end, one end is fixedly connected with the first free end, and the other end extends towards the fixed end; the second free end is fixedly connected with the auxiliary beam, and the second free end and the fixed end are arranged at an interval; the at least one pair of main beams are arranged in a gap between the fixed end and the first free end, and the two ends of the at least one pair of main beams are fixedly connected with the fixed end and the free end respectively; the first free end and the second free end are both provided with detection mass blocks. The AlN piezoelectric thick film layer is deposited on at least one pair of main beams and auxiliary beams; and the Ag layer is deposited on the AlN piezoelectric thick film layer.

Description

Technical Field

[0001] This invention relates to the field of piezoelectric energy harvester technology, and more particularly to a bistable AlN piezoelectric thick film vibration energy harvester. Background Technology

[0002] With the rapid development of microelectronics technology, the demand for energy supply for miniaturized, low-power electronic devices is increasing. Piezoelectric energy harvesters, as devices capable of converting mechanical energy from the environment into electrical energy, have received widespread attention. For some sensing devices operating in harsh environments or remotely and intermittently, the lifespan of built-in batteries is limited, and manual maintenance and battery replacement are very inconvenient. Harvesting energy from the environment using vibration energy harvesters can extend the lifespan of the equipment and reduce maintenance workload. However, most conventional vibration energy harvesters adopt a single-degree-of-freedom structure, and their operating bandwidth is limited by the inherent frequency band of the single-degree-of-freedom system, resulting in limited energy harvesting efficiency.

[0003] Therefore, it is essential to provide a bistable AlN piezoelectric thick-film vibration energy harvester that can improve energy harvesting efficiency by rationally configuring the mechanical structure and expanding the operating frequency band. Summary of the Invention

[0004] In view of this, the present invention proposes a bistable AlN piezoelectric thick film vibration energy harvester that employs a nonlinear arc beam and widens the operating frequency band.

[0005] This invention provides a bistable AlN piezoelectric thick-film vibration energy harvester, comprising: The substrate includes a fixed end, a first free end, a second free end, an auxiliary beam, and at least one pair of main beams, with a gap between the fixed end and the first free end; The fixed end is fixedly installed relative to the ground; the fixed end has a first end face and a second end face that are positioned opposite each other. An auxiliary beam is set in the gap between the fixed end and the first free end, with one end fixedly connected to the first free end and the other end extending toward the fixed end; The second free end is located on the side of the auxiliary beam away from the first free end and is fixedly connected to the auxiliary beam. The gap between the second free end and the fixed end is set. At least one pair of main beams are disposed in the gap between the fixed end and the first free end, and are respectively located on both sides of the extension direction of the auxiliary beam. The two ends of the at least one pair of main beams are respectively fixedly connected to the fixed end and the free end. The first detection mass block is located on the side of the first free end close to the first end face and extends outward in a direction away from the first free end; The second detection mass block is located on the side of the second free end close to the first end face and extends outward in a direction away from the first free end; AlN piezoelectric thick film layer, deposited on the side of at least one pair of main beams and auxiliary beams near the second end face; An Ag layer is deposited on the side of the AlN piezoelectric thick film away from the first end face.

[0006] Based on the above technical solutions, preferably, the at least one pair of main beams and auxiliary beams each have concave arc-shaped side surfaces; the contours of the AlN piezoelectric thick film layer and the Ag layer are adapted to the contours of the at least one pair of main beams and auxiliary beams.

[0007] Preferably, the auxiliary beam is located at the midpoint of the first free end side surface, and at least one pair of main beams are symmetrically arranged on both sides of the extension direction of the auxiliary beam.

[0008] Preferably, the curvature of the arcuate side surface of the auxiliary beam is greater than the curvature of the arcuate side surface of at least one pair of main beams.

[0009] Preferably, the first free end, the second free end, the auxiliary beam, and at least one pair of main beams have the same thickness; the width of the second free end is greater than the width of the edge of the auxiliary beam.

[0010] Preferably, both the first and second detection mass blocks are made of tungsten.

[0011] More preferably, the first detection mass block and the first free end, and the second detection mass block and the second free end are both fixed by UV adhesive bonding.

[0012] Preferably, the substrate is made of stainless steel.

[0013] Preferably, the thickness of the AlN piezoelectric thick film layer is 10 micrometers.

[0014] The bistable AlN piezoelectric thick-film vibration energy harvester provided by this invention has the following advantages compared with the prior art: (1) This scheme adopts a substrate with a bistable structure, especially the feature of the auxiliary beam connecting the first free end and the second free end and the gap between it and the fixed end, to realize the core structure of bistable. The structure enables the device to jump between the two potential wells under vibration excitation, significantly broadening the response bandwidth and making it more sensitive to low-frequency and broadband environmental vibration. (2) The auxiliary beam and at least one pair of main beams adopt an arc beam structure, which can optimize the stress distribution; AlN piezoelectric thick film and Ag layer are deposited on the auxiliary beam and at least one pair of main beams respectively, covering the main deformation area of ​​each beam, ensuring that the AlN piezoelectric thick film is consistent with the deformation height of the beam. Combined with a thicker AlN piezoelectric thick film and using the Ag layer as an electrode, it can output a larger strain-induced charge and a higher open circuit voltage, thereby improving the energy conversion efficiency of a single vibration. (3) At least one pair of main beams are symmetrically set on both sides of the auxiliary beam. Combined with two detection mass blocks, the inertia of the collector can be increased. Tungsten has a very high density. The mass of tungsten of the same volume is much greater than that of silicon or stainless steel. This can reduce the overall resonant frequency, better collect the energy of low-frequency environmental vibration, and make the first free end or the second free end produce greater deformation to improve the strain amplitude and power generation of the piezoelectric material AlN piezoelectric thick film layer. (4) Stainless steel substrates have the characteristics of high toughness and fatigue resistance. Compared with traditional silicon substrates, they can not only effectively alleviate the residual stress accumulated during the piezoelectric thick film deposition process, but also improve the structural strength and load-bearing capacity of the device. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the structure of a bistable AlN piezoelectric thick film vibration energy harvester according to the present invention; Figure 2 This is a schematic diagram of the explosion state of a bistable AlN piezoelectric thick film vibration energy harvester according to the present invention; Figure 3 This is a schematic diagram of the displacement response of a bistable AlN piezoelectric thick film vibration energy harvester under different vibration modes according to the present invention; Figure 4 The present invention provides the frequency response simulation results of a bistable AlN piezoelectric thick film vibration energy harvester according to the present invention. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] Conventional vibration energy harvesters mostly employ a single-degree-of-freedom structure, whose operating bandwidth is limited by the inherent frequency band of the single-degree-of-freedom system, resulting in limited energy harvesting efficiency. Therefore, such as... Figure 1 Combination Figure 2 As shown, this invention provides a bistable AlN piezoelectric thick-film vibration energy harvester, comprising: The substrate 100 includes a fixed end 1, a first free end 2, a second free end 3, an auxiliary beam 4, and at least one pair of main beams 5. In this embodiment, the substrate 100 is made of stainless steel. Stainless steel substrates have high toughness and fatigue resistance. Compared with traditional silicon substrates, they can not only effectively alleviate the residual stress accumulated during piezoelectric thick film deposition, but also improve the structural strength and load-bearing capacity of the device. Fixed end 1 is fixedly set relative to the ground; fixed end 1 has a first end face 11 and a second end face 12 that are set opposite to each other; The first free end 2 is spaced apart from the fixed end 1; The auxiliary beam 4 is set in the gap between the fixed end 1 and the first free end 2, with one end fixedly connected to the first free end 2 and the other end extending toward the fixed end 1. The second free end 3 is located on the side of the auxiliary beam 4 away from the first free end 2 and is fixedly connected to the auxiliary beam 4. The second free end 3 is separated from the fixed end 1. Neither the first free end nor the second free end is fixed, and both can sense external vibration signals.

[0019] At least one pair of main beams 5 are disposed within the gap between the fixed end 1 and the first free end 2, and are respectively located on both sides of the extension direction of the auxiliary beam 4. The two ends of the at least one pair of main beams 5 are respectively fixedly connected to the fixed end 1 and the free end; Figure 1 and Figure 2 It is known that at least one pair of main beams 5 and auxiliary beams 4 are arranged in parallel, and at least one pair of main beams 5 and auxiliary beams 4 are used to cantilever the first free end and the second free end, so that the first free end and the second free end form a cantilever beam structure. The first free end 2, the second free end 3, the auxiliary beam 4 and the at least one pair of main beams 5 have the same thickness.

[0020] The first detection mass block 6 is located on the side of the first free end 2 near the first end face 11 and extends outward in a direction away from the first free end 2; The second detection mass block 7 is located on the side of the second free end 3 near the first end face 11 and extends outward in a direction away from the first free end 2. The first detection mass block 6 and the second detection mass block 7 can increase inertia and drive at least one pair of main beams 5 and auxiliary beams 4 to produce greater nonlinear deformation. In this embodiment, both the first detection mass block 6 and the second detection mass block are made of tungsten. Tungsten has a significantly higher density than stainless steel. The large mass of the detection mass block can effectively reduce the resonant frequency of the system's vibration energy harvester, making it more suitable for collecting low-frequency environmental vibration energy. Moreover, it can drive at least one pair of main beams 5 and auxiliary beams 4 to produce greater deformation, thereby increasing the strain amplitude and power generation of the piezoelectric material.

[0021] An AlN piezoelectric thick film layer 8 is deposited on at least one pair of main beams 5 and auxiliary beams 4 near the second end face 12. The AlN piezoelectric thick film layer 8 is used as a piezoelectric material. In one embodiment, the AlN piezoelectric thick film layer 8 has a thickness of 10 micrometers, exhibiting a higher sensing material volume ratio. Compared to conventional films with a thickness of less than 1 micrometer, it can generate more open-circuit voltage, store more charge and energy, thereby significantly improving the energy harvesting efficiency and total output power of a single deformation, and producing an enhanced electrical output response under external excitation. The aluminum nitride used here is a common piezoelectric material.

[0022] Ag layer 9 is deposited on the side of AlN piezoelectric thick film layer 8 away from the first end face 11. Ag layer 9 has good conductivity and is used as an electrode in this embodiment, that is, to output the electrical energy signal generated by the piezoelectric material.

[0023] like Figure 1 As shown, at least one pair of main beams 5 and auxiliary beams 4 both have concave arc-shaped side surfaces; the contours of the AlN piezoelectric thick film layer 8 and the Ag layer 9 conform to the contours of at least one pair of main beams 5 and auxiliary beams 4. In particular, the curvature of the arc-shaped side surface of the auxiliary beam 4 is greater than the curvature of the arc-shaped side surface of at least one pair of main beams 5.

[0024] The auxiliary beam has a greater curvature, which means that its axial stiffness is lower and it is more prone to bending and buckling instability. This drives the entire vibration energy harvester into a bistable structure. At least one pair of main beams 5 has slightly higher stiffness and mainly bears the load and power generation functions. The stiffness difference caused by this curvature can precisely control the critical force / displacement required for bistable instability.

[0025] Furthermore, the arc-shaped at least one pair of main beams 5 and auxiliary beams 4 significantly enhance the stress in the local area at the geometric transition, resulting in a more uniform stress distribution. This uniform stress distribution increases the effective strain level within the AlN piezoelectric thick film layer 8, thereby improving energy conversion efficiency. During vibration, the geometry of the arc-shaped at least one pair of main beams 5 and auxiliary beams 4 can better guide the transmission and distribution of stress, allowing the AlN piezoelectric thick film layer 8 to be subjected to effective stress over a larger area, thus generating more charge output.

[0026] In one embodiment, the auxiliary beam 4 is located at the midpoint of the side surface of the first free end 2, and at least one pair of main beams 5 are symmetrically arranged on both sides of the extension direction of the auxiliary beam 4. This symmetrically distributed structure ensures that the two equilibrium positions of the bistable state have the same or similar potential well depth and stiffness, which can improve the output stability of the vibration energy harvester.

[0027] The first detection mass block 6 and the first free end 2, and the second detection mass block 7 and the second free end 3, are both fixed by UV adhesive bonding. The UV adhesive bonding method provides a certain degree of elasticity, which can buffer the detection mass block from the first or second free end.

[0028] The following is an analysis based on limiting the specific dimensions of the vibration energy harvester and conducting characteristic experiments.

[0029] In this embodiment, as follows Figure 1 As shown, with the x-direction representing length and the y-direction representing width, the fixed end 1 has a length of 4mm and a width of 20mm; the first free end 2 and the first detection mass block 6 have a length of 6mm and a width of 20mm; the second free end and the second detection mass block 7 have a length of 4mm and a width of 6mm; the auxiliary beam 4 has a length of 3.7mm and a width of 6mm; and the pair of main beams 5 have a length of 8.5mm and a width of 6mm, with a center distance of 13.6mm. Under this characteristic dimension combination structure, the device structure can achieve a dual-modal pure bending deformation mode. This design can effectively improve the strain level on the cantilever beam structure while suppressing piezoelectric energy dissipation caused by torsional effects. Simultaneously, this structure possesses wideband energy harvesting capabilities, exhibiting excellent electromechanical coupling characteristics, especially in low-frequency vibration environments below 200Hz, meeting the application requirements for environmental vibration energy capture.

[0030] like Figure 3 As shown, in the first vibration mode, i.e. 1 st In the modal analysis, both the first detection mass block 6 and the second detection mass block 7 exhibit significant displacement responses. However, the mechanical stress distribution on the two main beams 5 is more pronounced than that on the auxiliary beam 4 at the center. This means that in the first vibration mode, the two main beams 5 bear greater mechanical stress, becoming the main component of structural deformation and energy transfer. This stress distribution characteristic means that during operation in the first vibration mode, the vibration energy harvester mainly relies on the parallel connection of the two main beams 5 for charge collection. The larger stress on the two main beams 5 causes corresponding strain within the AlN piezoelectric thick film layer 8 at that location, thereby converting mechanical energy into electrical energy through the piezoelectric effect, achieving charge collection.

[0031] When entering the second vibration mode, namely 2 ndIn the second vibration mode, the displacement response of the first detection mass 6 decreases, while the second detection mass 7 exhibits obvious vibration characteristics, with stress mainly concentrated on the auxiliary beam 4 at the center. Unlike the first vibration mode, in the second vibration mode, the auxiliary beam 4 at the center becomes the main area of ​​stress concentration. Therefore, in the second vibration mode, charge collection is mainly achieved through the auxiliary beam 4. Under stress, the auxiliary beam 4 causes effective strain in the AlN piezoelectric thick film layer 8 at that location, thereby converting mechanical energy into electrical energy.

[0032] Both vibration modes are pure bending modes. The two modes represent the attitude and displacement changes of the vibration energy harvester at different frequencies, and the displacement degree of different test mass blocks is also different.

[0033] Figure 4 The simulation results of the frequency response of the vibration energy harvester are shown, in which two distinct peaks are observed at 59 Hz and 174 Hz. Figure 4 (a) and Figure 4 The peak frequencies in (b) correspond to the first and second resonant frequencies of the vibration energy harvester, respectively. This verifies the characteristics of the vibration energy harvester under two vibration modes. It meets the environmental monitoring requirements for low resonant frequencies below 200 Hz.

[0034] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A bi-stable AlN piezoelectric thick film vibration energy harvester characterized by, include: The substrate includes a fixed end, a first free end, a second free end, an auxiliary beam, and at least one pair of main beams, with a gap between the fixed end and the first free end; The fixed end is fixedly installed relative to the ground; the fixed end has a first end face and a second end face that are positioned opposite each other. An auxiliary beam is set in the gap between the fixed end and the first free end, with one end fixedly connected to the first free end and the other end extending toward the fixed end; The second free end is located on the side of the auxiliary beam away from the first free end and is fixedly connected to the auxiliary beam. The gap between the second free end and the fixed end is set. At least one pair of main beams are disposed in the gap between the fixed end and the first free end, and are respectively located on both sides of the extension direction of the auxiliary beam. The two ends of the at least one pair of main beams are respectively fixedly connected to the fixed end and the free end. The first detection mass block is located on the side of the first free end close to the first end face and extends outward in a direction away from the first free end; The second detection mass block is located on the side of the second free end close to the first end face and extends outward in a direction away from the first free end; AlN piezoelectric thick film layer, deposited on the side of at least one pair of main beams and auxiliary beams near the second end face; An Ag layer is deposited on the side of the AlN piezoelectric thick film away from the first end face.

2. A bistable AlN piezoelectric thick film vibration energy harvester according to claim 1, characterized in that, The at least one pair of main beams and auxiliary beams each have concave arc-shaped side surfaces; the contours of the AlN piezoelectric thick film layer and the Ag layer are adapted to the contours of the at least one pair of main beams and auxiliary beams.

3. A bistable AlN piezoelectric thick film vibration energy harvester according to claim 2, wherein, The auxiliary beam is located at the midpoint of the first free end side surface, and at least one pair of main beams are symmetrically arranged on both sides of the extension direction of the auxiliary beam.

4. A bistable AlN piezoelectric thick film vibration energy harvester according to claim 2, wherein, The curvature of the curved side surface of the auxiliary beam is greater than the curvature of the curved side surface of at least one pair of main beams.

5. A bistable AlN piezoelectric thick-film vibration energy harvester according to claim 2, characterized in that, The first free end, the second free end, the auxiliary beam, and at least one pair of main beams have the same thickness; the width of the second free end is greater than the width of the edge of the auxiliary beam.

6. A bistable AlN piezoelectric thick-film vibration energy harvester according to claim 2, characterized in that, Both the first and second detection mass blocks are made of tungsten.

7. A bistable AlN piezoelectric thick-film vibration energy harvester according to claim 6, characterized in that, The first detection mass block and the first free end, and the second detection mass block and the second free end are both fixed by UV adhesive bonding.

8. A bistable AlN piezoelectric thick-film vibration energy harvester according to claim 2, characterized in that, The substrate is made of stainless steel.

9. A bistable AlN piezoelectric thick-film vibration energy harvester according to claim 2, characterized in that, The thickness of the AlN piezoelectric thick film is 10 micrometers.

Images