Broadband microwave wireless energy collection device and method based on flexible metasurface

Abstract

The invention belongs to but not limited to the technical field of microwaves, and particularly relates to a broadband microwave wireless energy collection device and method based on a flexible metasurface, and the device comprises a flexible substrate layer, a metasurface unit array layer, and an energy conversion and output layer. The metasurface unit array layer is composed of a plurality of same metasurface units according to a specific arrangement mode, each metasurface unit comprises a metal patch structure and a dielectric layer, and specifically comprises an upper-layer metal patch structure, an upper-layer dielectric layer, a lower-layer metal patch structure, an air layer, a lower-layer dielectric layer and a bottom-layer feed network; the flexible substrate layer is made of materials with good flexibility, low dielectric constant and low loss characteristics, polyimide with the thickness of 0.1 mm is adopted as the substrate layer, the flexibility of the substrate can be guaranteed through the thickness, and the influence on microwave signal transmission can be effectively reduced; the flexible substrate layer is used for providing flexible support for the whole metasurface structure, so that the metasurface structure can adapt to fitting requirements of various irregular surfaces.

Description

Technical Field

[0001] The present invention belongs to but is not limited to the field of microwave technology, and in particular relates to a broadband microwave wireless energy collection device and method based on a flexible metasurface. Background Art

[0002] With the rapid development of wireless communication technology and the Internet of Things, the demand for miniaturized, low-power devices is growing. Many devices require a continuous energy supply, but traditional battery-powered devices have problems such as limited battery life and the need for frequent replacement or charging. Microwave wireless energy transmission technology, as an effective energy transmission method, has the advantages of long transmission distance and high energy transmission efficiency, providing a new way to solve the above problems.

[0003] In microwave wireless energy transmission systems, energy harvesting devices are key components. Currently common energy harvesting devices, such as traditional rectennas, have many limitations. On the one hand, their operating frequency range is relatively narrow, making it difficult to adapt to the collection of microwave signals of different frequencies in complex and changeable electromagnetic environments, resulting in low energy harvesting efficiency. On the other hand, most traditional energy harvesting devices are rigid structures. In practical applications, especially for some scenarios that require adhesion to irregular surfaces or use in flexible environments, they cannot meet the requirements of flexible laying and conformality with objects, greatly limiting their scope of application.

[0004] In recent years, the emergence of metasurface technology has brought new opportunities to the field of energy harvesting. Metasurface is an artificially designed two-dimensional planar structure. Through the careful design of its unit structure, it can achieve flexible regulation of electromagnetic waves. However, the existing metasurfaces used for energy harvesting still have problems such as complex structure, insufficient flexibility, and unsatisfactory broadband performance, which cannot well meet the needs of broadband, flexible, and efficient energy harvesting in practical applications. Therefore, the development of a broadband flexible energy harvesting metasurface for microwave wireless energy transmission that can overcome the above-mentioned defects has important practical significance and application value.

[0005] In view of the above analysis, the technical problems that urgently need to be solved in the existing technology are: the existing metasurfaces used for energy collection still have problems such as complex structure, insufficient flexibility, and unsatisfactory broadband performance, and cannot well meet the needs of wide-band, flexible, and efficient energy collection in practical applications. Summary of the invention

[0006] In response to the problems existing in the prior art, the present invention provides a wide-band microwave wireless energy harvesting device and method based on a flexible metasurface to solve the problems of narrow operating frequency, rigid structure, and inability to meet the needs of complex application scenarios in existing energy harvesting devices, thereby achieving efficient microwave energy collection within a wide bandwidth and having good flexibility to adapt to various irregular surfaces and flexible working environments.

[0007] The present invention is implemented as follows: a wide-band microwave wireless energy collection device based on a flexible metasurface includes a flexible substrate layer, a metasurface unit array layer, and an energy conversion and output layer. The metasurface unit array layer is composed of a plurality of identical metasurface units arranged in a specific manner, and each metasurface unit includes a metal patch structure and a dielectric layer, specifically including an upper metal patch structure, an upper dielectric layer, a lower metal patch structure, an air layer, a lower dielectric layer, and an underlying feeding network. The flexible substrate layer is made of a material with good flexibility, low dielectric constant, and low loss characteristics, and a 0.1 mm thick polyimide (PI) is used as the substrate layer. This thickness can not only ensure the flexibility of the substrate, but also effectively reduce the impact on microwave signal transmission. The function of the flexible substrate layer is to provide flexible support for the entire metasurface structure, so that it can adapt to the fitting requirements of various irregular surfaces.

[0008] Furthermore, the upper metal patch structure specifically includes: the metal patch structure uses a liquid metal material gallium-indium alloy with an electrical conductivity of 6*10^6S / m. The upper resonance unit uses two circular rings with radii of 11.1mm and 7.7mm as resonance boundaries, and the ring widths are 2.9mm and 2.3mm respectively. At the same time, split and cascade branches are added between the circular rings to enhance the electromagnetic resonance of the internal structure. The split width is 0.2mm, and the cascade structure widths are 0.4mm, 0.7mm, and 0.5mm respectively. This shape can generate multiple resonance modes within a wide frequency band, thereby achieving effective capture of microwave signals of different frequencies.

[0009] Furthermore, the upper dielectric layer specifically includes: polyimide is used as a flexible dielectric material, with a relative dielectric constant of 3.5 and a loss tangent of 0.0027. The thickness of the dielectric layer is 0.1 mm, which not only serves to isolate the metal patch from the flexible substrate layer, but also has an important influence on the electromagnetic performance of the metasurface unit. By reasonably selecting the material and thickness of the dielectric layer, the impedance matching of the metasurface unit can be optimized and the energy collection efficiency can be improved. The lower dielectric layer is the same as the upper dielectric layer.

[0010] Furthermore, the lower metal patch structure specifically includes: the lower patch structure is the same as the upper patch structure, but the lower patch structure is used to generate resonant frequency points at low frequencies, and the lower resonance unit uses two circular rings with radii of 15.8mm and 13.8mm as resonance boundaries, and the ring widths are 1.6mm and 1.8mm respectively, and the split and cascade structures have the same parameters as the upper metal patch structure.

[0011] Furthermore, the air layer specifically includes: adding an air layer between the upper dielectric layer and the lower dielectric layer, adjusting the phase of the electromagnetic wave by adding a 3mm air layer, and promoting the absorption effect of the metasurface on the electromagnetic wave.

[0012] Furthermore, the bottom feeding network specifically includes: using coplanar waveguide electromagnetic coupling to transmit the energy received on the unit to the bottom feeding network to facilitate subsequent energy collection.

[0013] Furthermore, the metasurface unit arrangement specifically includes: multiple metasurface units are arranged in a periodic array on the flexible substrate layer, and the spacing between units is 32mm. This periodic arrangement can form a specific electromagnetic periodic structure, enhance the scattering and capture capabilities of broadband microwave signals, and ensure the stability of the electromagnetic performance of the metasurface during flexible deformation.

[0014] Furthermore, coplanar waveguide coupling feeding is adopted at the bottom of the energy conversion and output layer. Electric field coupling feeding is a contactless energy transmission method that relies on the electric field between adjacent conductors to achieve energy transmission. In the coplanar waveguide, the electric field is mainly concentrated between the signal line and the ground plane. By properly designing the coupling structure, efficient electric field coupling feeding can be achieved.

[0015] Another object of the present invention is to provide a method for collecting broadband microwave wireless energy based on a flexible metasurface using the broadband microwave wireless energy collection device based on a flexible metasurface, comprising:

[0016] S1, when a broadband microwave signal is incident on the energy-harvesting metasurface of the present invention, the metal patch structure in the metasurface unit array layer generates an induced current under the action of the microwave electric field.

[0017] S2, due to the double-layer printing structure, the upper and lower units are designed to correspond to high and low frequencies respectively, so that the metasurface can have strong absorption and scattering capabilities for microwave signals of different frequencies. Subsequently, the phase of the reflected wave is adjusted by adding an air layer to form a continuous absorption frequency band.

[0018] S3, the induced current is coupled to the energy conversion and output layer through the dielectric layer.

[0019] In combination with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solutions to be protected by the present invention are as follows:

[0020] First, the beneficial effects of the present invention include:

[0021] 1. Broadband characteristics

[0022] By double-printing the metasurface units, designing high-frequency and low-frequency units respectively, and introducing phase delay by adding an air layer between the dielectric substrates, multiple resonant modes can be excited within a wide bandwidth, so that the metasurface has strong absorption and scattering capabilities for microwave signals of different frequencies, effectively broadening the frequency range of energy collection, improving energy collection efficiency, and being able to adapt to complex and changeable electromagnetic environments.

[0023] 2.Flexibility

[0024] The entire metasurface is made of a flexible substrate layer and flexible materials. It is designed with polyimide (PI) as the dielectric substrate and gallium-indium alloy as the metal, so that it can adapt to the fitting requirements of various irregular surfaces and can be used in a flexible environment, greatly expanding the application scenarios, such as wearable devices, biomedical implants, flexible electronic devices and other fields.

[0025] 3. Efficient energy harvesting

[0026] Through the optimization of the unit structure design, the real parts of the equivalent dielectric constant and permeability are both negative in the range of 2GHz to 6GHz, which shows that excellent absorption can be achieved due to the atypical electromagnetic characteristics. The real part of the equivalent input impedance is close to 1, and the imaginary part is close to 0. Excellent absorption also comes from good impedance matching with free space. The energy absorption efficiency is improved.

[0027] 4. Simple structure, easy to make

[0028] The metasurface structure of the present invention is relatively simple, and the manufacturing process of the metasurface unit array layer can be processed by inkjet printing technology, which is simple to process, has a low overall manufacturing cost, and is easy to mass produce and apply.

[0029] Second, as auxiliary evidence of the inventiveness of the claims of the present invention, it is also reflected in the following important aspects:

[0030] (1) The expected benefits and commercial value of the technical solution of the present invention after transformation are:

[0031] The invention provides an efficient broadband microwave wireless energy harvesting device that can be widely used in wireless sensor networks, wearable devices, Internet of Things devices, implantable medical devices and other fields to solve the endurance problem of traditional battery-powered devices. Its flexible properties allow it to be integrated into curved or irregular surface devices, such as smart fabrics and electronic skin, opening up emerging markets. Since it is manufactured using inkjet printing technology, it has low costs and is suitable for large-scale production. It has broad commercial prospects and can be applied on a large scale in the future to achieve mass production and market promotion, with high economic benefits.

[0032] (2) The technical solution of the present invention fills the technical gap in the industry at home and abroad:

[0033] At present, most of the research on microwave energy collection at home and abroad is focused on the rectenna with rigid structure. However, the present invention proposes a broadband energy collection device based on flexible metasurface, which makes microwave energy collection technology flexible and broadband compatible for the first time. The double-layer resonant structure and air layer control strategy of the device optimize the absorption of electromagnetic waves and realize broadband energy collection from 2GHz to 6GHz, breaking through the limitations of traditional narrowband energy collection devices and filling the technical gap in this field at home and abroad. By using liquid metal gallium indium alloy as the metal patch material, the flexibility and processability of the device are improved, which is innovative in the field of microwave wireless energy collection.

[0034] (3) The technical solution of the present invention solves the technical problems that people have been eager to solve but have never been able to solve successfully:

[0035] Existing microwave energy harvesting technologies usually have problems with narrow bandwidth and rigid structures that limit usage scenarios, making them difficult to apply to applications such as flexible electronics and wearable devices. The present invention successfully breaks through this bottleneck by combining metasurface design with flexible materials, achieving efficient energy collection over a wide bandwidth. The use of a double-layer structure and air layer regulation allows the metasurface energy harvesting device to maintain efficient energy conversion capabilities within different frequency ranges, solving the long-standing technical problems of low microwave energy collection efficiency and limited operating frequency bands. The use of a flexible substrate in the structural design makes it suitable for bendable and attachable application environments, solving the problem that rigid antennas cannot adapt to complex application scenarios, and providing a new solution for the application of wireless power supply technology.

[0036] (4) The technical solution of the present invention overcomes technical prejudice:.

[0037] The traditional field of microwave energy harvesting mainly focuses on rectennas with rigid structures, believing that flexible materials will significantly reduce electromagnetic performance, resulting in reduced energy collection efficiency. This invention breaks this traditional perception by optimizing the metasurface structure and material selection, proving that flexible structures can also achieve efficient microwave energy harvesting. The use of liquid metal gallium-indium alloy to improve conductivity, combined with a specific double-layer resonant structure design, overcomes the industry's inherent prejudice that flexible materials have excessive losses in high-frequency electromagnetic applications. The use of inkjet printing technology to manufacture metasurface units not only maintains the high precision of the flexible structure, but also avoids the pollution problem of the traditional etching process, breaking the traditional concept that high-performance microwave devices must rely on rigid materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Schematic diagram of the overall structure of a broadband flexible energy harvesting metasurface provided by an embodiment of the present invention;

[0039] Figure 2 is an enlarged view of the supersurface unit structure provided by an embodiment of the present invention;

[0040] Figure 3 is a schematic diagram of an energy conversion and output layer circuit provided by an embodiment of the present invention;

[0041] Figure 4 is a rendering of a metasurface array provided by an embodiment of the present invention;

[0042] Figure 5 is a diagram of HE measurement results provided by an embodiment of the present invention;

[0043] Figure 6 This is a diagram of the energy collection performance of the metasurface array within the conformal curvature radius R provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0045] 1. Overall structure

[0046] The metasurface unit is printed on two layers of 0.1mm thick polyimide dielectric substrates, with a total of three layers of metal structure, namely the upper resonant unit, the lower resonant unit and the bottom feeding network.

[0047] 2. Flexible substrate layer

[0048] The flexible substrate layer is made of materials with good flexibility, low dielectric constant and low loss characteristics. Polyimide (PI) with a thickness of 0.1 mm is used as the substrate layer. This thickness can not only ensure the flexibility of the substrate, but also effectively reduce the impact on microwave signal transmission. The role of the flexible substrate layer is to provide flexible support for the entire metasurface structure, so that it can adapt to the needs of fitting various irregular surfaces.

[0049] Polyimide (polyimide dielectric substrate); EGain (liquid metal layer); air (air layer)

[0050] 3. Metasurface unit array layer

[0051] The metasurface unit array layer is composed of a plurality of identical metasurface units arranged in a specific manner. Each metasurface unit includes a metal patch structure and a dielectric layer.

[0052] Upper metal patch structure: The metal patch structure uses a liquid metal material gallium-indium alloy with an electrical conductivity of 6*10^6S / m. The upper resonant unit uses two circular rings with radii of 11.1mm and 7.7mm as the resonance boundary, and the ring widths are 2.9mm and 2.3mm respectively. At the same time, split and cascade branches are added between the circular rings to enhance the electromagnetic resonance of the internal structure. The split width is 0.2mm, and the cascade structure widths are 0.4mm, 0.7mm, and 0.5mm respectively. This shape can generate multiple resonant modes within a wide frequency band, thereby achieving effective capture of microwave signals of different frequencies.

[0053] Upper dielectric layer: Polyimide is used as the flexible dielectric material, with a relative dielectric constant of 3.5 and a loss tangent of 0.0027. The thickness of the dielectric layer is 0.1 mm, which not only isolates the metal patch from the flexible substrate layer, but also has an important influence on the electromagnetic performance of the metasurface unit. By reasonably selecting the material and thickness of the dielectric layer, the impedance matching of the metasurface unit can be optimized and the energy collection efficiency can be improved.

[0054] Lower metal patch structure: The lower patch structure is the same as the upper patch structure, but the lower patch structure is used to generate resonant frequency points at low frequencies. The lower resonance unit uses two circular rings with radii of 15.8mm and 13.8mm as resonance boundaries, and the ring widths are 1.6mm and 1.8mm respectively. The split and cascade structures have the same parameters as the upper metal patch structure.

[0055] Air layer: An air layer is added between the upper dielectric layer and the lower dielectric layer. By adding a 3mm air layer, the phase of the electromagnetic wave is adjusted to promote the absorption effect of the metasurface on the electromagnetic wave.

[0056] Lower dielectric layer: same as upper dielectric layer.

[0057] Bottom-layer feeding network: The energy received on the unit is transmitted to the bottom-layer feeding network by coplanar waveguide electromagnetic coupling, which facilitates subsequent energy collection.

[0058] Unit arrangement: Multiple metasurface units are arranged in a periodic array on the flexible substrate layer, with a spacing of 32 mm between units. This periodic arrangement can form a specific electromagnetic periodic structure, enhance the scattering and capture capabilities of broadband microwave signals, and ensure the stability of the electromagnetic performance of the metasurface during flexible deformation.

[0059] Working principle:

[0060] When a broadband microwave signal is incident on the energy-harvesting metasurface of the present invention, the metal patch structure in the metasurface unit array layer generates an induced current under the action of the microwave electric field. Due to the double-layer printing structure, the upper unit and the lower unit are designed to correspond to high frequency and low frequency respectively, so that the metasurface can have strong absorption and scattering capabilities for microwave signals of different frequencies, and then adjust the phase of the reflected wave by adding an air layer, thereby forming a continuous absorption band. These induced currents are coupled to the energy conversion and output layer through the dielectric layer.

[0061] Figure 1 The overall structure of the metasurface is shown, including the flexible substrate layer 1, the metasurface unit array layer 2, and the energy conversion and output layer 3. The positional relationship and overall layout between the layers can be clearly seen.

[0062] Figure 2 The structure of the metasurface unit is shown in detail, including a metal patch structure 21 and a dielectric layer 22. The specific shape of the metal patch [such as a fractal structure] and the dimensions of each part are clearly marked, such as the length L1, width W1, thickness T1 of the metal patch, and the thickness D1 of the dielectric layer.

[0063] like Figure 3 As shown, the bottom uses coplanar waveguide coupling feeding. Electric field coupling feeding is a contactless energy transmission method that mainly relies on the electric field between adjacent conductors to achieve energy transmission. In the coplanar waveguide, the electric field is mainly concentrated between the signal line and the ground plane. By properly designing the coupling structure, efficient electric field coupling feeding can be achieved.

[0064] Example 1

[0065] 1. Material selection

[0066] The dielectric substrate is made of polyimide (PI) with a thickness of 0.1 mm. PI has good flexibility and a moderate dielectric constant (relative dielectric constant is about 3.5), and has a low loss tangent (loss tangent is about 0.0027), which can meet the requirements of the metasurface for flexible support and low signal loss.

[0067] The metal patch structure of the metasurface unit uses liquid metal gallium-indium alloy with a thickness of 0.035mm. Gallium-indium alloy has high electrical conductivity (conductivity reaches 6*10^6S / m) and flexibility that other metals do not have, which can effectively sense microwave signals to generate current.

[0068] 2. Production process

[0069] First, the designed metasurface unit is exported from the simulation software as a gerber file and imported into the T-SRD model liquid metal printer.

[0070] The printer absorbs the medium substrate PI and prints the liquid metal in the form of ink onto the medium substrate by inkjet printing.

[0071] The printed unit was placed in a reflow oven and heated at a constant temperature of 160°C for 10 minutes to solidify the liquid metal on the dielectric substrate.

[0072] Re-import the gerber file of the bottom unit, put the cooled PI back into the printer to print the bottom media substrate, and then heat and cure it to complete the processing.

[0073] Performance Testing:

[0074] The prepared broadband flexible energy-harvesting metasurface is placed in a microwave darkroom, and a microwave signal generator is used to transmit a broadband microwave signal with a frequency range of 1GHz to 8GHz. The signal is amplified by a power amplifier, and then sent to the horn antenna through a coaxial line to transmit to free space. The DC power output by the metasurface is measured by a power meter, and the energy collection efficiency is calculated. The test results show that in the entire frequency range of 2GHz-6GHz, the energy collection efficiency of the metasurface can reach more than 50%, and its half-power bandwidth reaches 100%. In the frequency range of 2GHz to 6GHz, the energy collection efficiency can reach up to 79.6%. At the same time, the metasurface is subjected to a bending test, and it is bent into shapes with different curvature radii. During the bending process, the energy collection performance of the metasurface remains basically stable, verifying its good flexibility and electromagnetic performance stability.

[0075] 1. Specific application fields or related products of the present invention.

[0076] Wearable devices and smart textiles: Since the present invention adopts a flexible metasurface structure, it can be directly integrated into wearable devices such as smart clothing, smart wristbands, smart glasses, and smart gloves to provide wireless energy supply and reduce dependence on traditional batteries. It can be used for sports health monitoring equipment (such as heart rate monitoring, step recording, blood oxygen detection equipment) and smart medical equipment (such as smart knee protectors and ECG monitoring patches). It is suitable for smart tactical clothing in the military field, so that soldiers' equipment can be wirelessly powered to extend combat time.

[0077] Wireless sensor network (WSN) and Internet of Things (IoT) devices: Applicable to remote wireless sensors, such as environmental monitoring, industrial monitoring, smart agriculture and other application scenarios, to achieve long-term energy supply for sensor nodes. In the field of smart home, such as wireless door locks, temperature and humidity sensors, air quality monitors, etc., to provide continuous and stable microwave energy collection.

[0078] 2. Relevant evidence of the technical effects obtained by the embodiments of the present invention.

[0079] Firstly, the energy absorption effect of the designed energy-harvesting metasurface was measured, such as Figure 4 As shown, the speaker transmission power is adjusted to 1W and the distance L is adjusted from 20cm to 80cm to observe the effect of the metasurface array.

[0080] Subsequently, L is fixed to test the performance of the metasurface array. Pload and Pinc can be obtained by measuring the electric field distribution on the spatial aperture of the metasurface array using a power meter. The calculation formula of Pinc is:

[0081] L is fixed at 50cm, the transmission power is 1W, the surface power density of the central resonant unit is 0.51mW / cm2, and the measurement results of HE are as follows Figure 5 As shown. At 2.8GHz, the maximum receiving efficiency is 78%, which is slightly lower than the simulation results. Table I gives the comparison of the flexible metasurface array with other works. It can be seen that this work maintains a high receiving efficiency when composed of flexible materials. The differences between the simulation results and the experimental results are analyzed. First, the metasurface array consists of 3×3 units, but the simulated array is an infinite array with periodic boundaries, which will affect the performance of the central unit. Secondly, although the dielectric constant of PMI is close to that of air, there is still a certain gap. Third, the dielectric constant of the dielectric substrate polyimide used will also change at different frequencies and cannot be accurately measured.

[0082] Select the highest efficiency point and fix the transmission frequency point, and set the incident angle θ to -30° to 30° by rotating the turntable. Measure the receiving efficiency at different incident angles, such as Figure 5 As shown. It can be observed that within the horizontal angle range of ±15, the receiving efficiency can be maintained above 60%. As the incident angle shifts, the receiving efficiency decreases. The decrease in receiving efficiency can be explained by the decrease in effective electrical resonance, which is caused by the decrease in the normal component of the wave vector. When the incident angle increases, the normal component of the wave vector decreases accordingly, leading to this phenomenon.

[0083] Finally, the energy harvesting performance of the metasurface array within the conformal curvature radius R was measured. Figure 6 As shown in the figure, when R is 180mm, 140mm and 100mm, the maximum receiving efficiency can be maintained above 75%. When R is 60mm, some frequency offset will occur, but the maximum receiving efficiency is still greater than 70%. The results show that the designed metasurface array can maintain excellent receiving efficiency performance under different conformal curvature radii. Similarly, the different metasurface curvature radii will also cause the normal component of the wave vector to change, so the receiving efficiency is different from the vertical incidence condition.

[0084] In the description of the present invention, unless otherwise specified, "plurality" means two or more than two; the orientations or positional relationships indicated by the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail", etc. are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0085] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modification, equivalent substitution and improvement made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A broadband microwave wireless energy harvesting device based on a flexible metasurface, characterized in that: It includes a flexible substrate layer, a metasurface unit array layer and an energy conversion and output layer; the metasurface unit array layer is composed of multiple identical metasurface units in a specific arrangement, and each metasurface unit includes a metal patch structure and a dielectric layer, specifically including an upper metal patch structure, an upper dielectric layer, a lower metal patch structure, an air layer, a lower dielectric layer and an underlying feeding network; the flexible substrate layer is made of a material with good flexibility, low dielectric constant and low loss characteristics, and a 0.1mm thick polyimide is used as the substrate layer, which can not only ensure the flexibility of the substrate, but also effectively reduce the impact on microwave signal transmission; the function of the flexible substrate layer is to provide flexible support for the entire metasurface structure, so that it can adapt to the fitting requirements of various irregular surfaces.

2. The broadband microwave wireless energy harvesting device based on flexible metasurface according to claim 1, characterized in that: The upper metal patch structure specifically includes: the metal patch structure adopts liquid metal material gallium-indium alloy with an electrical conductivity of 6*10^6S / m; the upper resonance unit uses two circular rings with radii of 11.1mm and 7.7mm respectively as resonance boundaries, and the ring widths are 2.9mm and 2.3mm respectively. At the same time, split and cascade branches are added between the circular rings to enhance the electromagnetic resonance of the internal structure. The split width is 0.2mm, and the cascade structure widths are 0.4mm, 0.7mm, and 0.5mm respectively.

3. The broadband microwave wireless energy harvesting device based on flexible metasurface according to claim 1, characterized in that: The upper dielectric layer specifically includes: polyimide is used as the flexible dielectric material, its relative dielectric constant is 3.5, and the loss tangent is 0.0027; the thickness of the dielectric layer is 0.1mm, which not only serves to isolate the metal patch from the flexible substrate layer, but also has an important influence on the electromagnetic properties of the metasurface unit. By reasonably selecting the material and thickness of the dielectric layer, the impedance matching of the metasurface unit is optimized and the energy collection efficiency is improved. The lower dielectric layer is the same as the upper dielectric layer.

4. The broadband microwave wireless energy harvesting device based on flexible metasurface according to claim 1, characterized in that: The lower metal patch structure specifically includes: the lower patch structure is the same as the upper patch structure, but the lower patch structure is used to generate resonant frequency points at low frequencies, and the lower resonance unit uses two circular rings with radii of 15.8mm and 13.8mm as resonance boundaries, and the ring widths are 1.6mm and 1.8mm respectively, and the split and cascade structures have the same parameters as the upper metal patch structure.

5. The broadband microwave wireless energy harvesting device based on flexible metasurface according to claim 1, characterized in that: The air layer specifically includes: adding an air layer between the upper dielectric layer and the lower dielectric layer, adjusting the phase of the electromagnetic wave by adding a 3mm air layer, and promoting the absorption effect of the metasurface on the electromagnetic wave.

6. The broadband microwave wireless energy harvesting device based on flexible metasurface according to claim 1, characterized in that: The bottom feeding network specifically includes: using coplanar waveguide electromagnetic coupling to transmit the energy received on the unit to the bottom feeding network to facilitate subsequent energy collection.

7. The broadband microwave wireless energy harvesting device based on flexible metasurface according to claim 1, characterized in that: The arrangement of the metasurface units specifically includes: a plurality of metasurface units are arranged in a periodic array on a flexible substrate layer, and the spacing between the units is 32 mm.

8. The broadband microwave wireless energy harvesting device based on flexible metasurface according to claim 1, characterized in that: Coplanar waveguide coupling feeding is used at the bottom of the energy conversion and output layer. Electric field coupling feeding is a contactless energy transmission method that relies on the electric field between adjacent conductors to achieve energy transmission. In the coplanar waveguide, the electric field is mainly concentrated between the signal line and the ground plane. By properly designing the coupling structure, efficient electric field coupling feeding can be achieved.

9. A method for collecting broadband microwave wireless energy based on a flexible metasurface, using the broadband microwave wireless energy collection device based on a flexible metasurface as claimed in any one of claims 1 to 8, comprising: S1, when a broadband microwave signal is incident on the energy-harvesting metasurface of the present invention, the metal patch structure in the metasurface unit array layer generates an induced current under the action of the microwave electric field; S2, due to the double-layer printing structure, the upper and lower units are designed to correspond to high and low frequencies respectively, so that the metasurface can have strong absorption and scattering capabilities for microwave signals of different frequencies. Then, the phase of the reflected wave is adjusted by adding an air layer to form a continuous absorption band; S3, the induced current is coupled to the energy conversion and output layer through the dielectric layer.

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