Negative Poisson's ratio effect energy capturing device and method suitable for road structure

Abstract

The invention discloses a negative Poisson's ratio effect energy harvesting device and method suitable for a road structure, and belongs to the technical field of road vibration energy harvesting. The device comprises a substrate with a negative Poisson's ratio structure, piezoelectric ceramic covering and fixed on the substrate, and an excitation rod arranged on the surface of the piezoelectric ceramic. The negative Poisson's ratio structure is formed by periodically arranging a plurality of inwards-concave annular unit cells, and when the negative Poisson's ratio structure is subjected to the action of pressure stress such as traffic load, unique two-way expansion deformation can be generated, so that vertical pressure is efficiently converted into two-way tensile strain in a plane, and the two-way tensile strain is transmitted to piezoelectric ceramics. According to the structure, a traditional d31 working mode is reserved, a d32 mode is more effectively excited, the charge migration path is remarkably widened, and the electro-mechanical conversion efficiency is improved. The device is especially suitable for a low-frequency traffic load environment, solves the problem of low energy collection efficiency caused by resonant frequency mismatch of a traditional cantilever beam structure, and provides an efficient and reliable solution for self-power supply of road infrastructures.

Description

Technical Field

[0001] This invention relates to the field of road vibration energy harvesting technology, specifically to an energy harvesting device and method adapted to the negative Poisson's ratio effect of road structures. Background Technology

[0002] With the widespread application of intelligent transportation technologies, numerous intelligent devices have been deployed in areas such as traffic infrastructure health monitoring, road condition information collection, and vehicle-to-everything (LoV) networks, significantly improving the interactivity and operational efficiency of transportation systems. However, the large-scale deployment of such devices has also led to increased energy consumption, posing challenges to existing power grid supply and the sustainable operation and maintenance of the system. The global highway network is vast and widely distributed. Taking China as an example, by the end of 2025, the total length of highways had reached 5.4368 million kilometers, and the road environment contains abundant energy resources that can be collected.

[0003] To reduce the dependence of transportation infrastructure on traditional power grids and optimize overall system energy consumption, researchers have begun exploring energy harvesting technologies to convert mechanical energy in the road environment into usable electrical energy. Currently, most common road energy harvesting devices employ cantilever beam structures, relying on the piezoelectric effect of the D31 mode for power generation. However, because road traffic loads are low-frequency excitations, cantilever beam structures struggle to reach a resonant state, resulting in low energy conversion efficiency. Furthermore, existing D31 modes also have limitations in energy harvesting capabilities.

[0004] Therefore, it is necessary to develop a new type of energy harvesting device that is suitable for low-frequency circuit environments and can improve energy harvesting efficiency, in order to overcome the problems of poor structural adaptability and limited energy output in existing technologies. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides an energy harvesting device that adapts to the negative Poisson's ratio effect of road structures. The power generation device using the negative Poisson's ratio structure can improve power generation efficiency.

[0006] This invention is achieved through the following technical solution: An energy harvesting device adapted to the negative Poisson's ratio effect of road structures, comprising: A substrate, wherein at least a portion of the substrate has a negative Poisson's ratio structure; Piezoelectric ceramics are covered and fixed onto the substrate of the negative Poisson's ratio structure region; An excitation rod is disposed on the surface of the piezoelectric ceramic; The negative Poisson's ratio structure is configured to generate bidirectional expansion deformation when subjected to compressive stress transmitted by the excitation rod, thereby causing the piezoelectric ceramic to generate an electrical signal.

[0007] Preferably, the negative Poisson's ratio structure is formed by a periodic array of multiple negative Poisson's ratio unit cells on the substrate.

[0008] Preferably, the negative Poisson's ratio unit cell is a centrally symmetric quadrilateral unit cell structure, comprising: Two first deformable edges arranged parallel to each other along a first direction; and Two second deformed edges are symmetrically connected to the two ends of the two first deformed edges; The second deformed edge is an arc-shaped edge that is concave inward toward the center of the unit cell structure.

[0009] Preferably, a tension arm is connected to the center of the second deformed edge, the tension arm extending along the first direction and used to connect with the center of the second deformed edge of the adjacent unit cell.

[0010] Preferably, the curvature of the second deformed edge is configured as an adjustable parameter.

[0011] Preferably, the negative Poisson's ratio unit cell is a hollow circumferential closed structure formed by connecting multiple deformable edges end to end, and all the deformable edges are concave towards the geometric center of the closed structure.

[0012] Preferably, the piezoelectric ceramic is fixed to the substrate by conductive adhesive; Preferably, the conductive adhesive is conductive silver paste; Preferably, the piezoelectric ceramic is PZT-5H.

[0013] Preferably, the excitation rod is made of insulating material.

[0014] A method for fabricating an energy harvesting device that adapts to the negative Poisson's ratio effect of road structures includes: The substrate and the piezoelectric ceramic surfaces to be bonded are electrically bonded to form a piezoelectric unit; By connecting the electrodes to the piezoelectric unit and placing the excitation rod on the surface of the piezoelectric ceramic, an energy harvesting device with a negative Poisson's ratio effect adapted to the road structure is obtained.

[0015] A road energy harvesting system includes a plurality of energy harvesting devices adapted to the negative Poisson's ratio effect of the road structure, the devices being laid in the road structure to convert mechanical energy generated by traffic loads into electrical energy.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects: This application provides an energy harvesting device adapted to the negative Poisson's ratio effect of road structures, which integrates a negative Poisson's ratio structural substrate with special mechanical behavior into a piezoelectric ceramic. By introducing a negative Poisson's ratio substrate capable of bidirectional in-plane expansion under pressure, this device fundamentally changes the stress and deformation modes of traditional piezoelectric energy harvesting elements under low-frequency road loads. When the vehicle load is transmitted to the device through the excitation rod, the negative Poisson's ratio substrate efficiently converts the vertical pressure into bidirectional in-plane tensile strain, which is simultaneously transferred to the piezoelectric ceramic sheet bonded to it. This shift in strain mode allows the piezoelectric ceramic to not only operate in the traditional d31 mode but also more effectively excite its in-plane d32 mode, significantly widening the path for charge separation and migration, thereby improving charge transfer efficiency at the microscopic level. Compared to the low energy harvesting efficiency of traditional cantilever beam structures due to difficulty in resonance under low-frequency excitation, this invention achieves a significant improvement in power output performance in typical low-frequency road environments (such as 10Hz) through structural innovation rather than relying on resonant frequency matching. Experimental data show that by optimizing the parameters of the negative Poisson's ratio unit cell, the device can achieve a higher open-circuit voltage. Therefore, this technical solution provides an effective technical path to solve the long-standing problem of low energy capture efficiency due to low-frequency excitation in the field of road energy harvesting, and has the comprehensive advantages of compact structure, strong adaptability, and high energy conversion efficiency. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the road piezoelectric power generation device of the present invention; Figure 2 This is a schematic diagram of the negative Poisson's ratio unit cell structure of the present invention; Figure 3 These are schematic diagrams of the structures of different substrates of the present invention; Figure 4 This is a schematic diagram of the piezoelectric unit of the present invention; Figure 5 This is a performance test diagram of the energy harvesting device of the present invention.

[0019] In the figure: 1. Substrate; 2. Fixed end; 3. Excitation rod; 4. Negative Poisson's ratio unit cell. Detailed Implementation To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0020] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0021] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0022] In the description of the embodiments of this application, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. In addition, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0023] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0024] In the description of the embodiments of this application, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0025] An energy harvesting device with a negative Poisson's ratio effect adapted to road structures includes a substrate with a negative Poisson's ratio effect and a piezoelectric ceramic covering the substrate, wherein an excitation rod is disposed on the piezoelectric ceramic.

[0026] This negative Poisson's ratio energy harvesting device fixes a piezoelectric ceramic unit onto a substrate exhibiting a negative Poisson's ratio effect. When a vehicle passes over the road surface and generates compressive stress, the substrate exhibits unique mechanical behavior under pressure: unlike conventional materials that contract laterally under pressure, this negative Poisson's ratio substrate undergoes bidirectional expansion deformation within the plane while being subjected to vertical pressure. This bidirectional expansion characteristic effectively enhances the cooperative response of the piezoelectric material's internal lattice, broadens the migration path of charge carriers, and thus significantly optimizes the charge separation and transfer process in the piezoelectric effect. Through this structural coupling, the device can more efficiently convert mechanical energy into electrical energy, improving the overall efficiency of energy recovery.

[0027] In some embodiments, a negative Poisson's ratio structure is formed in the substrate, the negative Poisson's ratio structure comprising a plurality of negative Poisson's ratio unit cells arranged in a periodic array on the substrate, the negative Poisson's ratio unit cells expanding bidirectionally when the substrate is subjected to compressive stress.

[0028] The substrate features a unique negative Poisson's ratio structure, composed of a large number of periodically arranged negative Poisson's ratio unit cells. When the substrate is subjected to external compressive stress, these unit cells expand bidirectionally in the direction perpendicular to the applied force through their unique internal hinge or bending deformation mechanism, exhibiting mechanical behavior diametrically opposed to that of conventional materials. This bidirectional expansion characteristic helps improve the substrate's energy absorption capacity, shear stiffness, and impact resistance, thereby effectively improving the overall structural stability and durability.

[0029] Optionally, the negative Poisson's ratio unit cell 4 includes a hollow circumferential closed structure formed by connecting multiple deformable edges end to end, with the deformable edges bent toward the center of the circumferential closed structure.

[0030] Under compressive stress, the deformable edge of the piezoelectric unit expands in the opposite direction of bending, thus causing each deformable edge to deform away from the center, thereby forming multi-directional expansion and improving the energy absorption capacity of the substrate.

[0031] The multiple deformable edges of this negative Poisson's ratio unit cell structure are connected end-to-end to form a complete hollow, circumferentially closed geometry. These deformable edges do not extend straight but instead bend uniformly towards the geometric center of the circumferential structure, forming a unique concave configuration. When the external piezoelectric unit is subjected to compressive stress, it drives each deformable edge to elastically expand in the opposite direction of its original bend. This motion mechanism causes each deformable edge to undergo radial deformation towards the outer edge of the structure, thereby triggering the unit cell to expand collaboratively in multiple directions. This multi-directional synchronous expansion behavior effectively enhances the energy dissipation efficiency of the substrate under stress, significantly improving the overall structure's energy absorption capacity and buffering performance.

[0032] Optional, see below Figure 2 The negative Poisson's ratio unit cell is a centrally symmetric quadrilateral unit cell structure, including a first deformed side and a second deformed side. Two first deformable edges are arranged parallel to each other along a first direction, and two second deformable edges are symmetrically arranged at both ends of the first deformable edges. The second deformable edges are concave arc-shaped edges, and the first deformable edges and the second deformable edges are connected end to end.

[0033] This negative Poisson's ratio unit cell adopts a centrally symmetric quadrilateral structure, mainly composed of two types of structural units: first deformable sides and second deformable sides. In the overall layout, the two first deformable sides are parallel and spaced apart along a first direction, forming the main supporting framework of the structure. The two second deformable sides are symmetrically connected to the two ends of the first deformable sides, with a continuously concave arc-shaped profile, exhibiting a geometrically regular concave feature. The first and second deformable sides are connected end-to-end, together forming a closed quadrilateral unit cell. This structural combination, when subjected to lateral or longitudinal loads, can achieve a negative Poisson's ratio effect through a special deformation mechanism of the sides, that is, bidirectional expansion deformation along the vertical direction under external force.

[0034] Furthermore, a tension arm is provided at the center of the second deformed side. One end of the tension arm is connected to the center of the second deformed side and is arranged along the first direction. The other end of the tension arm is used to connect the center of the side length of the second deformed side of the same negative Poisson's ratio unit cell.

[0035] See Figure 3 The figure illustrates three different configurations of negative Poisson's ratio unit cells, all designed with quadrilaterals as the basic unit and possessing similar topological layouts. The main difference between these unit cells lies in the significant variations in the curvature of the second deformable side, which affects the deformation behavior and mechanical properties of the structure. Specifically, Figure 3 The unit cell presented by A has the greatest curvature, and its second deformed edge shows a distinct arc-shaped indentation. This configuration helps to generate a large lateral contraction effect when under tension. Figure 3The unit cell in B has the smallest curvature, the second deformable edge is almost straight, the overall shape is more rigid, and the deformation capacity is relatively weaker; while Figure 3 The unit cell of C has a curvature between the former two, and the curvature of its second deformed edge is greater than that of the former two. Figure 3 B but smaller than Figure 3 Configuration A represents a transitional form, balancing flexibility and stability. By comparing the three configurations, the degree of influence of curvature on the negative Poisson's ratio effect can be intuitively understood.

[0036] In some embodiments, the substrate is provided with multiple rows of negative Poisson ratio units, each including multiple negative Poisson ratio unit cells, which are quadrilateral unit cell structures.

[0037] In some embodiments, the substrate has connection areas at both ends for connecting the fixing device 2.

[0038] The connection area is an extension area of ​​the substrate. It should be noted that negative Poisson's ratio unit cells are set in this extension area only in the area covered by the piezoelectric ceramic.

[0039] The fixing device is fixed to the connection area by an adhesive layer.

[0040] In some embodiments, the piezoelectric ceramic is fixed to the substrate 1 by a conductive adhesive, preferably a conductive silver paste.

[0041] The piezoelectric ceramic element is firmly bonded to a designated area of ​​substrate 1 using a layer of specially formulated conductive adhesive through dot coating or printing. This connection method not only achieves physical fixation but, more importantly, establishes a reliable electrical connection path between the piezoelectric ceramic and the substrate. As a preferred option, the conductive adhesive is specifically a conductive silver paste with stable curing performance and excellent conductivity. Its internal micron- or nano-sized silver particles ensure extremely low resistance at the contact interface, thereby efficiently conducting electrical signals, while its bonding strength also meets the mechanical reliability requirements of the device under complex operating conditions.

[0042] In some embodiments, the piezoelectric ceramic is PZT-5H.

[0043] In some embodiments, the excitation rod is an insulated excitation rod disposed on the surface of the piezoelectric ceramic.

[0044] The excitation rod is made of a highly insulating material, forming an insulated excitation rod. This insulated excitation rod is precisely positioned and fixed to a specific working surface of the piezoelectric ceramic element to transmit vibration and ensure electrical isolation.

[0045] Correspondingly, this application also provides a method for preparing the above-mentioned energy harvesting device with negative Poisson's ratio effect adapted to road structure, including the following steps: Step 1: Polish both sides of the piezoelectric ceramic (PZT-5H) and the substrate smooth, apply conductive silver paste to their surfaces, and bond them together; Step 2: Place the bonded piezoelectric ceramic and substrate into a heating box for heating and adhesive removal to form a piezoelectric unit; Step 3: Connect the piezoelectric unit above using wires and copper foil, with red connected to the positive terminal and black connected to the negative terminal; Step 4: Place the piezoelectric unit flat on the fixed end, with a clamping length of 1 / 2 the length of the non-bonded area on one side; Step 5: Place the drive rod tightly against the upper surface of the piezoelectric unit to obtain an energy harvesting device with negative Poisson's ratio effect.

[0046] See Figure 5 The energy-harvesting device with negative Poisson's ratio effect was subjected to piezoelectric testing on the test bench.

[0047] The two ends of the substrate are pressed and fixed to the test stage, and different excitation displacements and frequencies are applied using DMA (Dynamic Loader); both the fixed end and the drive rod are made of PVC (polyvinyl chloride), which serves as insulation.

[0048] See again Figure 3 Piezoelectric tests were conducted on the three types of energy harvesting devices with negative Poisson ratios.

[0049] Figure 3 The open-circuit voltage of the energy harvesting device with structure A was obtained using an oscilloscope. The test results showed that the open-circuit voltage was 3.51V at an excitation frequency of 10Hz and an excitation displacement of 0.5mm.

[0050] Figure 3 The open-circuit voltage of the B-structure energy harvesting device was obtained using an oscilloscope. The test results showed that the open-circuit voltage was 3.97V at an excitation frequency of 10Hz and an excitation displacement of 0.5mm.

[0051] Figure 3 The C-structure energy harvesting device was tested using an oscilloscope to obtain its open-circuit voltage. The results showed that the open-circuit voltage was 2.06V at an excitation frequency of 10Hz and an excitation displacement of 0.5mm.

[0052] Based on the above experiments, a dynamic loader was used to simulate a traffic load, and the open-circuit voltage was measured using an oscilloscope. Furthermore, by varying the negative Poisson's ratio unit cell parameters, the power generation efficiency was further improved. While maintaining the same external shape, the electrical response was increased, thus enhancing energy harvesting.

[0053] This application also provides a road energy harvesting system comprising multiple road piezoelectric power generation devices, which are laid in the road structure to convert mechanical energy generated by traffic loads into electrical energy.

[0054] This application discloses an energy-harvesting device with a negative Poisson's ratio effect adapted to road structures. For ordinary substrates with a positive Poisson's ratio effect, σ11 and σ22 are always opposite when subjected to external force, which reduces the output power of the piezoelectric unit. Therefore, a piezoelectric unit with a negative Poisson's ratio effect is introduced. The negative Poisson's ratio effect generated by the substrate causes the piezoelectric material to exhibit the same deformation in the x-axis and y-axis directions, thus producing the same signs σ11 and σ22. This method not only preserves the d31 operating mode but also supplements the mode caused by D32. The negative Poisson's ratio characteristic of the substrate enhances the charge transfer transport channel in the piezoelectric material, thereby improving the efficiency of charge separation and transfer.

[0055] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. An energy harvesting device that adapts to the negative Poisson's ratio effect of road structures, characterized in that, include: The substrate (1) has at least a portion of a region having a negative Poisson's ratio structure; Piezoelectric ceramics are covered and fixed on the substrate (1) of the negative Poisson's ratio structure region; An excitation rod (3) is disposed on the surface of the piezoelectric ceramic; The negative Poisson's ratio structure is configured to generate bidirectional expansion deformation when subjected to compressive stress transmitted by the excitation rod (3), thereby causing the piezoelectric ceramic to generate an electrical signal.

2. The energy harvesting device for the negative Poisson's ratio effect adapted to road structures according to claim 1, characterized in that, The negative Poisson ratio structure is formed by a periodic array of multiple negative Poisson ratio unit cells (4) on the substrate (1).

3. An energy harvesting device adapting to the negative Poisson's ratio effect of road structures according to claim 2, characterized in that, The negative Poisson's ratio unit cell (4) is a centrally symmetric quadrilateral unit cell structure, comprising: Two first deformable edges arranged parallel to each other along a first direction; and Two second deformed edges are symmetrically connected to the two ends of the two first deformed edges; The second deformed edge is an arc-shaped edge that is concave inward toward the center of the unit cell structure.

4. The energy harvesting device for the negative Poisson's ratio effect adapted to road structures according to claim 3, characterized in that, A tension arm is connected to the center of the second deformable edge, the tension arm extends along the first direction and is used to connect with the center of the second deformable edge of the adjacent unit cell.

5. The energy harvesting device for the negative Poisson's ratio effect adapted to road structures according to claim 3, characterized in that, The curvature of the second deformed edge is configured as an adjustable parameter.

6. The energy harvesting device for the negative Poisson's ratio effect adapted to road structures according to claim 2, characterized in that, The negative Poisson's ratio unit cell is a hollow, circumferentially closed structure formed by connecting multiple deformable edges end to end, and all deformable edges are concave towards the geometric center of the closed structure.

7. The energy harvesting device for the negative Poisson's ratio effect adapted to road structures according to claim 1, characterized in that, The piezoelectric ceramic is fixed to the substrate (1) by conductive adhesive; Preferably, the conductive adhesive is conductive silver paste; Preferably, the piezoelectric ceramic is PZT-5H.

8. The energy harvesting device for the negative Poisson's ratio effect adapted to road structures according to claim 1, characterized in that, The excitation rod (3) is made of insulating material.

9. A method for preparing an energy harvesting device with a negative Poisson's ratio effect adapted to road structures, characterized in that, The method, applied to the energy harvesting device as described in any one of claims 1-8, comprises: The substrate (1) and the piezoelectric ceramic surfaces to be bonded are electrically bonded to form a piezoelectric unit; The piezoelectric unit is wired with electrodes, and the excitation rod (3) is placed on the surface of the piezoelectric ceramic to obtain an energy harvesting device with a negative Poisson's ratio effect that adapts to the road structure.

10. A road energy harvesting system, characterized in that, The invention comprises a plurality of energy harvesting devices adapted to the negative Poisson's ratio effect of a road structure as described in any one of claims 1-8, the devices being laid in the road structure for converting mechanical energy generated by traffic loads into electrical energy.

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