A wearable electromagnetic energy harvester based on a fabric metasurface

Abstract

The application discloses a wearable electromagnetic energy collector based on a fabric metasurface, which comprises an upper layer of conductive copper cloth, a lower layer of conductive copper cloth and a dielectric layer between the upper layer of conductive copper cloth and the lower layer of conductive copper cloth; the upper layer of conductive copper cloth comprises two identical rectangular strips and two pairs of identical butterfly-shaped slot trapezoidal patches, the two identical rectangular strips are mirror-symmetric, and the two pairs of butterfly-shaped slot trapezoidal patches are center-symmetric; the lower edges of the two rectangular strips are connected through a load. The lower layer of conductive copper cloth is rectangular, and the side length of the lower layer of conductive copper cloth is equal to the side length of the dielectric layer. The upper layer of conductive copper cloth, the lower layer of conductive copper cloth and the dielectric layer are coaxial. The application has the advantages of compact design, flexible structure, bendable and co-forming, good energy absorption capacity at 2.95 GHz and 6.08 GHz, and can be applied to energy supply of a wireless sensor network, and has a wide application prospect in the Internet of Things, a body area network, health monitoring and the like.

Description

Technical Field

[0001] This invention belongs to the field of microwave collector technology, specifically relating to a wearable electromagnetic energy collector based on a fabric metasurface. Background Technology

[0002] To meet the growing power demands of wearable electronics and eliminate frequent, interrupted charging and discharging and cumbersome wired power transmission, wearable systems integrate energy harvesters such as solar cells, piezoelectric generators, and triboelectric generators, enabling them to operate self-sustainingly. While solar cells and mechanical energy harvesting are widely considered, they have their limitations. Solar cells are dependent on weather conditions and are only available during the day, while mechanical energy harvesting is limited by specific environments with frequent vibrations. As radio frequency electromagnetic signals become increasingly prevalent in everyday living spaces, radio frequency electromagnetic energy serves as an ideal power source for powering functional textile electronics and wearable wireless sensor networks. Electromagnetic energy harvesting is a technology that transfers energy to a load through the air without interconnecting cables, eliminating cumbersome wires and making device charging or power supply more convenient.

[0003] Electromagnetic energy harvesting has been demonstrated in textiles for wearable applications, such as using rectifier antennas to harvest electromagnetic energy and convert it into usable DC power, where the rectifier antennas can be implemented using flexible woven conductive materials. However, antennas used for radio frequency electromagnetic energy harvesting are large in size compared to the operating wavelength, making modular antenna arrays composed of them unsuitable for electromagnetic energy harvesting in wearable systems.

[0004] Metasurfaces possess unique negative permeability and negative permittivity in their electromagnetic properties, making them widely used in electromagnetic absorbers for electromagnetic shielding and stealth. Simultaneously, electromagnetic absorbers are being researched and developed for electromagnetic energy harvesting. The patent application filed by the University of Electronic Science and Technology of China, titled "An Electromagnetic Energy Harvester Based on Metasurfaces" (application number: 202010574397.0), discloses a technology that achieves good energy absorption capability and angular stability at 5.8 GHz; however, its structure requires through-holes penetrating the dielectric layer, increasing the processing complexity on fabric media and making it unsuitable for wearable electromagnetic energy harvesters. In 2022, Wei Yiqing et al. (Wei Y.Q., Duan JP, Jing HH, Lyu Z., Qu Z., Wang JY, Zhang BZA Multiband,Polarization-Controlled Metasurface Absorber for Electromagnetic Energy Harvesting and Wireless Power Transfer, IEEE Trans. Antennas Propag., 70, 5, 2022) achieved electromagnetic energy harvesting at the WIFI frequency using rigid dielectric substrates and printed circuit board technology. However, this method could not achieve flexible bending and was not suitable for wearable energy harvesting.

[0005] In summary, the main problems currently facing space electromagnetic energy harvesting are as follows:

[0006] 1) Existing metasurface energy harvesting requires metal vias to penetrate the dielectric layer, which increases the processing complexity on the fabric medium and cannot meet the needs of wearable electromagnetic energy harvesting.

[0007] 2) Existing metasurfaces have a single absorption frequency for energy harvesting, resulting in low energy harvesting efficiency in multi-spectral electromagnetic environments. Summary of the Invention

[0008] The purpose of this invention is to address the above-mentioned shortcomings in the prior art by providing a wearable electromagnetic energy harvester based on a fabric metasurface. This addresses the issues that existing metasurface energy harvesting requires metal vias to penetrate the dielectric layer, which increases the processing complexity on the fabric medium and fails to meet the needs of wearable electromagnetic energy harvesting. Furthermore, existing metasurface energy harvesting has a single absorption frequency, resulting in low energy harvesting efficiency in multi-spectral electromagnetic environments.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: a wearable electromagnetic energy harvester based on a fabric metasurface, comprising: an upper conductive layer, a lower conductive layer, and a dielectric layer located between the upper conductive layer and the lower conductive layer, wherein the upper conductive layer, the dielectric layer, and the lower conductive layer are connected in sequence;

[0010] The upper conductive layer includes an electromagnetic energy converging unit and a plurality of trapezoidal patches, wherein the plurality of trapezoidal patches are disposed on both sides of the electromagnetic energy converging unit.

[0011] Furthermore, the electromagnetic energy gathering unit includes a first rectangular strip, a second rectangular strip, and a load. The lower edges of the first and second rectangular strips are connected through the load. The first and second rectangular strips are used to gather electromagnetic energy onto the load for consumption.

[0012] Furthermore, the first rectangular strip and the second rectangular strip are mirror symmetrical.

[0013] Furthermore, the first rectangular strip and the second rectangular strip are spaced 1 mm apart.

[0014] Furthermore, the length of both the first rectangular strip and the second rectangular strip is 25mm, and the width of both is 2mm.

[0015] Furthermore, trapezoidal grooves are formed on several of the trapezoidal patches.

[0016] Furthermore, the trapezoidal patches are centrally symmetrical.

[0017] Furthermore, the trapezoidal patch has an upper base of 2mm, a lower base of 9mm, and a height of 23.5mm. The trapezoidal groove has an upper base of 1mm, a lower base of 4mm, and a distance of 22mm between the upper and lower bases.

[0018] Furthermore, the upper conductive layer, the lower conductive layer, and the dielectric layer are coaxial.

[0019] Furthermore, the main material of the dielectric layer is nylon, with a relative permittivity of 1.834, and the dielectric layer has a thickness of 2 mm, a length of 55 mm, and a width of 25 mm.

[0020] Beneficial effects:

[0021] 1. This invention differs from traditional large-size rectifier antennas in that it is small in size, has a low profile, no vias, and a simple structure, thus simplifying the complexity of the system.

[0022] 2. This invention uses conductive copper cloth to replace traditional metal materials, and the dielectric layer is made of nylon fabric substrate, which is flexible, easy to conform to shape, and has great advantages in wearable scenarios such as health monitoring.

[0023] 3. This invention can achieve efficient energy absorption at dual frequencies, which greatly expands the potential application scenarios compared to traditional single-frequency energy harvesting. For example, it can provide a selectable and more precise energy supply for sensor networks in human health monitoring systems in complex electromagnetic environments.

[0024] In summary, this invention effectively solves the problem that existing metasurface energy harvesting requires metal vias to penetrate the dielectric layer, which increases the processing complexity on fabric media and makes it unsuitable for wearable electromagnetic energy harvesting. At the same time, it also solves the problem that existing metasurface energy harvesting has a single absorption frequency and low energy harvesting efficiency in multi-spectral electromagnetic environments. Attached Figure Description

[0025] Figure 1 This is a structural diagram of a wearable electromagnetic energy harvester based on a fabric metasurface;

[0026] Figure 2 This is a curve showing the energy harvesting capacity of a wearable electromagnetic energy harvester based on a fabric metasurface when electromagnetic waves are incident perpendicularly.

[0027] Figure 3 This is a graph showing the energy harvesting curve of a wearable electromagnetic energy harvester based on a fabric metasurface when the electromagnetic wave is incident at an angle of 5°.

[0028] 1. First rectangular strip, 2. Second rectangular strip, 3. Trapezoidal patch, 4. Load, 5. Dielectric layer, 6. Lower conductive layer. Detailed Implementation

[0029] The invention will now be further explained with reference to the accompanying drawings.

[0030] like Figure 1 As shown, the present invention provides a wearable electromagnetic energy harvester based on a fabric metasurface, comprising: an upper conductive layer, a lower conductive layer 6, and a dielectric layer 5 located between the upper and lower conductive layers. The upper conductive layer, the dielectric layer 5, and the lower conductive layer 6 are connected sequentially from top to bottom.

[0031] The upper conductive layer includes an electromagnetic energy converging unit and several trapezoidal patches 3. The electromagnetic energy converging unit includes a first rectangular strip 1, a second rectangular strip 2, and a load 4. The lower edges of the first rectangular strip 1 and the second rectangular strip 2 are connected by the load 4. The first rectangular strip 1 and the second rectangular strip 2 are disposed on the dielectric layer 5, and are mirror-symmetrical. Several trapezoidal patches 3 are disposed on both sides of the electromagnetic energy converging unit and located on the dielectric layer 5. Each trapezoidal patch 3 has a trapezoidal groove, and the trapezoidal patches 3 are centrally symmetrical.

[0032] In this embodiment, the upper conductive layer is adhered to the upper surface of the dielectric layer 5, and the lower conductive layer 6 is adhered to the lower surface of the dielectric layer 5. The upper conductive layer, the lower conductive layer 6, and the dielectric layer 5 are coaxial. The upper conductive layer includes an electromagnetic energy gathering unit and several trapezoidal patches 3. The upper conductive layer is an upper conductive copper cloth layer, and the lower conductive layer 6 is a lower conductive copper cloth layer; both the upper and lower conductive copper cloth layers are flexible conductive layers. The dielectric layer 5 is primarily made of nylon with a relative permittivity of 1.834; its thickness is 2 mm, its length a is 55 mm, and its width b is 25 mm. The lower conductive layer 6 is rectangular, with a side length equal to that of the dielectric layer 5. Through the above configuration, this invention achieves flexible bending, is easy to conform to design, is convenient to wear, and is suitable for wearable scenarios such as health monitoring.

[0033] The electromagnetic energy gathering unit includes a first rectangular strip 1, a second rectangular strip 2, and a load 4. The lower edges of the first rectangular strip 1 and the second rectangular strip 2 are connected by the load 4. The spacing g between the first rectangular strip 1 and the second rectangular strip 2 is 1 mm. The length of both the first rectangular strip 1 and the second rectangular strip 2 is 25 mm, and the width w is 2 mm. The first rectangular strip 1 and the second rectangular strip 2 gather electromagnetic energy and dissipate it in the load 4.

[0034] There are two pairs of trapezoidal patches 3, with two patches in each pair. Each trapezoidal patch 3 has a trapezoidal slot. The two pairs of trapezoidal patches 3 with slots are centrally symmetrical and have an overall butterfly shape. The upper base w1 of the trapezoidal patch 3 is 2mm, the lower base w2 is 9mm, the height s is 23.5mm, and the thickness is 0.1mm. The upper edge of the trapezoidal slot is 1mm, the lower edge is 4mm, and the distance s1 between the upper and lower edges is 22mm. The trapezoidal patches 3 and the trapezoidal slots on them add electromagnetic resonance at higher frequencies, thus achieving a dual-frequency electromagnetic resonance effect.

[0035] This invention simulates the collector of this invention within the energy harvesting device frequency band of 2-7 GHz by modeling in the electromagnetic software CST STUDIO SUITE.

[0036] like Figure 2 As shown, a comparative analysis of the energy harvesting under load is performed on two curves of the present invention when electromagnetic waves are incident perpendicularly. Figure 2 The horizontal axis represents frequency, and the vertical axis represents the energy collected by the load. Figure 2The curves in the figure represent the simulated energy harvesting curves of the load when electromagnetic waves are incident perpendicularly, as per the present invention. From the simulated energy harvesting curves of the load when electromagnetic waves are incident perpendicularly, it can be seen that the load absorbs 0.41W of energy (total energy 0.5W) at 2.95GHz, achieving an absorption efficiency of 82%, and the load absorbs 0.41W of energy (total energy 0.5W) at 6.08GHz, also achieving an absorption efficiency of 82%. This demonstrates that the present invention has a very good collection effect on perpendicularly incident electromagnetic waves.

[0037] like Figure 3 As shown, a comparative analysis of the energy harvesting under load is performed on two curves of the present invention when the electromagnetic wave is incident at a tilt of 5°. Figure 3 The horizontal axis represents frequency, and the vertical axis represents the energy collected by the load. Figure 3 The curve in the figure represents the simulated energy harvesting curve of the load when the electromagnetic wave is incident at a 5° angle. From the simulated energy harvesting curve of the load when the electromagnetic wave is incident at a 5° angle, it can be seen that at 2.989 GHz, the load absorbs 0.41 W of energy (total energy 0.5 W), achieving an absorption efficiency of 82%. At 6.11 GHz, the load absorbs 0.28 W of energy (total energy 0.5 W), with an absorption efficiency exceeding 50%. Although the two absorption frequencies are slightly offset compared to when the electromagnetic wave is incident perpendicularly, the absorption efficiency exceeding 50% indicates that the present invention has a good harvesting effect when the incident electromagnetic wave angle is 5°.

[0038] In summary, the present invention has a small size and low profile, which effectively solves the problem that conventional rectifier antennas are too large to meet the miniaturization requirements of large-scale wireless energy harvesting devices. The design is free of vias, has a simple structure, and simplifies the complexity of the system.

[0039] This invention features a compact design, using conductive copper cloth instead of traditional metal materials. The dielectric layer is made of nylon fabric substrate, which is flexible, easy to conform to shape, and has great advantages in wearable scenarios such as health monitoring.

[0040] This invention exhibits excellent energy absorption capabilities at both 2.95 GHz and 6.08 GHz, achieving highly efficient energy absorption at dual frequencies. Compared to traditional single-frequency energy harvesting, this significantly expands potential application scenarios. For example, it can provide selective and more precise energy supply for sensor networks in human health monitoring systems under complex electromagnetic environments. Furthermore, it can be used for energy supply in wireless sensor networks, showing broad application prospects in the Internet of Things, body area networks, and health monitoring.

[0041] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A wearable electromagnetic energy harvester based on a fabric metasurface, characterized in that, include: An upper conductive layer, a lower conductive layer (6), and a dielectric layer (5) located between the upper conductive layer and the lower conductive layer are connected in sequence; The upper conductive layer includes an electromagnetic energy gathering unit and a plurality of trapezoidal patches (3), with the plurality of trapezoidal patches (3) disposed on both sides of the electromagnetic energy gathering unit; The electromagnetic energy gathering unit includes a first rectangular strip (1), a second rectangular strip (2), and a load (4). The lower edges of the first rectangular strip (1) and the second rectangular strip (2) are connected by the load (4). The first rectangular strip (1) and the second rectangular strip (2) are used to gather electromagnetic energy onto the load (4) for consumption.

2. The wearable electromagnetic energy harvester based on fabric metasurface according to claim 1, characterized in that, The first rectangular strip (1) and the second rectangular strip (2) are mirror symmetrical.

3. The wearable electromagnetic energy harvester based on fabric metasurface according to claim 1, characterized in that, The first rectangular strip (1) and the second rectangular strip (2) are spaced 1 mm apart.

4. The wearable electromagnetic energy harvester based on fabric metasurface according to claim 1, characterized in that, The length of the first rectangular strip (1) and the width of the second rectangular strip (2) are both 25 mm and 2 mm respectively.

5. The wearable electromagnetic energy harvester based on fabric metasurface according to claim 1, characterized in that, Trapezoidal grooves are provided on several of the trapezoidal patches (3).

6. The wearable electromagnetic energy harvester based on fabric metasurface according to claim 5, characterized in that, The trapezoidal patches (3) are centrally symmetrical.

7. The wearable electromagnetic energy harvester based on fabric metasurface according to claim 5, characterized in that, The trapezoidal patch (3) has an upper base of 2mm, a lower base of 9mm, and a height of 23.5mm. The upper edge of the trapezoidal groove is 1mm, the lower edge is 4mm, and the distance between the upper and lower edges is 22mm.

8. The wearable electromagnetic energy harvester based on fabric metasurface according to claim 1, characterized in that, The upper conductive layer, the lower conductive layer (6), and the dielectric layer (5) are coaxial.

9. The wearable electromagnetic energy harvester based on fabric metasurface according to claim 1, characterized in that, The main material of the dielectric layer (5) is nylon, with a relative permittivity of 1.834, and the dielectric layer (5) has a thickness of 2 mm, a length of 55 mm, and a width of 25 mm.

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