Liquid metal based frequency reconfigurable metasurface, frequency control method and application thereof

Abstract

The present application relates to a kind of frequency reconfigurable metasurface based on liquid metal, frequency control method and application, belong to electromagnetic metamaterial field.It includes lower layer dielectric substrate, upper layer dielectric cover plate, liquid metal;Upper layer dielectric cover plate is etched with circular through-hole;Lower layer dielectric substrate is etched with similar microchannel of bow tie type, to fill liquid metal;Upper and lower layer dielectric is bonded together;Liquid metal is driven in microchannel by external force and flows;Liquid metal flows into microchannel by circular through-hole, and frequency is adjusted by adjusting liquid metal in microchannel to realize frequency adjustable.The present application adopts liquid metal to control frequency compared with prior art, and the working frequency range is wider, and the resonance depth is larger, can be used as wave-absorbing material and should be realized on airborne antenna The stealth of aircraft.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic metamaterials and relates to a frequency reconfigurable metasurface based on liquid metal. It achieves switching between four frequency states by filling with liquid metal, and the operating frequency can be changed from 2.45 GHz to 6.8 GHz. Background Technology

[0002] Metasurfaces are artificially designed structures whose shape and size variations affect the resonance characteristics of electromagnetic waves. In recent years, reconfigurable metasurfaces have been widely used due to their diverse operating modes, high efficiency, and ability to achieve better electromagnetic stealth. Frequency-reconfigurable metasurfaces can be used in military fields such as radar, satellites, aerospace communications, etc., and also have considerable application prospects in the civilian sector.

[0003] Traditional reconfigurable metasurfaces are controlled by loading electronic components, such as PIN diodes, varactor diodes, or MEMS switches. These electronic components require bias circuits to provide voltage. Therefore, most traditional metamaterial structures are designed and manufactured with fixed shapes and dimensions, and changing their shape and dimensions often requires complex micromechanical design or reprocessing.

[0004] The development of metasurfaces based on liquid metals offers a new approach to the design of traditional reconfigurable metasurfaces. Liquid metals, due to their excellent dynamic reconfigurability, have become a widely used novel material for achieving reconfigurability in recent years. Currently, liquid metal alloys mainly include rubidium, cesium, francium, mercury, and gallium. In engineering, gallium-based alloys, which are non-toxic, stable, and have a lower melting point, are typically chosen as conductor materials. Gallium-based liquid metals have been widely applied in fields such as thermal control and energy, biomedicine, intelligent machines, and aerospace.

[0005] Generally, there are two methods to achieve reconfigurability of liquid metal. First, liquid metal can be used as a switch. Second, liquid metal can be used as part of a radiating element, and its radiation characteristics can be changed by adjusting its length, shape, and position. However, currently, frequency reconfigurability based on liquid metal is achieved as a whole with the antenna; standalone frequency reconfigurable metasurfaces based on liquid metal have not yet been documented. Summary of the Invention

[0006] The technical problem this invention aims to solve is that most existing reconfigurable metasurface structures achieve reconfigurability by combining solid metals and electronic components. However, solid metal metasurfaces have poor material plasticity, making reconfiguration difficult and often requiring electronic components. Furthermore, the mechanical fatigue of these electronic components can affect the reconfigurability of the metasurface, and bias circuits are generally needed to provide the voltage. Therefore, the proposed reconfigurable metasurface based on liquid metal offers a new solution to the inherent defects of traditional metasurfaces.

[0007] The technical solution adopted to solve the above technical problems is as follows:

[0008] A frequency-reconfigurable metasurface based on liquid metal is characterized by comprising a lower dielectric substrate, an upper dielectric cover plate, liquid metal, and a metal ground plate; the upper dielectric cover plate is etched with circular through holes; the lower dielectric substrate is etched with bowtie-shaped microchannels for filling the liquid metal; the upper and lower dielectric layers are bonded together; the metal ground plate is located on the lower surface of the lower dielectric substrate; the liquid metal flows within the microchannels driven by external force; and the circular through holes are located above the microchannels.

[0009] A further technical solution of the present invention: the bowtie-like microchannel includes arrow-shaped channel, diamond-shaped channel, first trapezoidal channel and second trapezoidal channel connected in sequence, and the various channels are connected by rectangular channels.

[0010] A further technical solution of the present invention: each microchannel is provided with a circular through hole above it, and the circular through hole is located at the connection of each microchannel.

[0011] A further technical solution of the present invention: the materials of the lower dielectric substrate and the upper dielectric cover plate are PDMS, with a relative permittivity of 2.67 and a tangent angle loss of 0.0375.

[0012] A further technical solution of the present invention: the liquid metal is a gallium-indium alloy EGaIn.

[0013] A further technical solution of the present invention: when extracting liquid metal, sodium hydroxide solution is added into the microchannel to remove surface oxides, thereby making it more fluid.

[0014] A frequency control method based on a frequency-reconfigurable metasurface unit using liquid metal is characterized by achieving different frequencies by adjusting the liquid metal in different microchannels.

[0015] A further technical solution of the present invention: when the arrow-shaped flow channel is filled with liquid metal, the frequency achieved is 6.8 GHz; when the arrow-shaped flow channel and the diamond-shaped flow channel are filled with liquid metal, the frequency achieved is 4.95 GHz; when the arrow-shaped flow channel, the diamond-shaped flow channel, and the first trapezoidal flow channel are filled with liquid metal, the frequency achieved is 3.4 GHz; when the arrow-shaped flow channel, the diamond-shaped flow channel, the first trapezoidal flow channel, and the second trapezoidal flow channel are filled with liquid metal, the frequency achieved is 2.45 GHz.

[0016] An application of a frequency-reconfigurable metasurface based on liquid metal is characterized by replacing the absorbing material with this metasurface unit in an airborne antenna to achieve aircraft stealth.

[0017] The beneficial effects of this invention are as follows:

[0018] This invention provides a frequency-reconfigurable metasurface controlled by liquid metal. Compared to traditional reconfigurable metasurfaces, the metasurface designed in this invention does not require the addition of electronic components; frequency reconfiguration is achieved by whether or not liquid metal is filled within the microchannels. The structure designed in this invention has four states, corresponding to four resonant frequencies, which can be changed from 2.45 GHz to 6.8 GHz, with a resonant range exceeding 4 GHz. Its beneficial effects are as follows:

[0019] 1. In this invention, the fluidity of liquid metal is used to replace traditional electronic devices to achieve reconfigurable characteristics, eliminating the need for additional bias circuitry. Frequency reconfigurability is achieved simply by changing the flow position of the liquid metal within the microchannel. This invention offers high flexibility and avoids mechanical fatigue compared to traditional methods for achieving frequency reconfigurability.

[0020] 2. Existing technologies combine an antenna with a high-impedance surface and a varactor diode to construct a phase-variable reflective unit, whose operating frequency can vary between 5.1 GHz and 6.0 GHz. This invention, however, achieves frequency reconfiguration using liquid metal without the need for a varactor diode, and its operating frequency range is also wider than that of existing technologies.

[0021] 3. In the prior art, the unit achieves the tuning effect by changing the electrical length of the radiation aperture, and its operating frequency is 1.42GHz-1.84GHz. However, the present invention uses liquid metal to control the frequency, and the operating frequency range of the present invention is wider than that of the prior art.

[0022] 4. The microchannels designed in this invention include arrow-shaped channels, rhomboid channels, first trapezoidal channels, second trapezoidal channels, and rectangular channels. Different combinations of shapes are used to achieve reconstruction at different frequencies. The middle shape uses arrow-shaped channels to utilize the flow of liquid metal at the top and bottom. Since the rhomboid channels need to connect two pairs of symmetrical arrow-shaped channels and first trapezoidal channels, this invention utilizes the symmetrical shape of the rhomboid channels, which makes the liquid metal filling on both sides of the symmetry balanced. Finally, the first and second trapezoidal channels are used. Here, the design utilizes the fact that the upper base of the trapezoid is smaller than the lower base, which is conducive to the flow of liquid metal.

[0023] 5. The arrow-shaped flow channel, diamond-shaped flow channel, first trapezoidal flow channel, and second trapezoidal flow channel are connected by a rectangular flow channel. The rectangular flow channel structure is significantly smaller than the two flow channels being connected. By utilizing the surface tension of the liquid metal, it effectively prevents the liquid metal from easily flowing from one flow channel to another, thereby enhancing the stability of the reconfigurable metasurface.

[0024] 6. The resonance depth of the metasurface of this invention can reach below -40dB. As a microwave absorbing material, it should be used to achieve aircraft stealth in airborne antennas. The stealth effect is significantly better than that of traditional reconfigurable metasurfaces that use loaded electronic components. Attached Figure Description

[0025] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0026] Figure 1 is a schematic diagram of the metasurface unit described in this invention, including... Figure 1A and Figure 1B ,in Figure 1A This is a top view of a frequency-reconfigurable metasurface based on liquid metal. Figure 1B This is a side view of the frequency-reconfigurable metasurface.

[0027] 1-Upper layer cover plate, 2-Lower layer dielectric substrate, 3-Microchannel, 4-Circular through hole, 5-Metal floor, 6-Liquid metal, 3-1-Arrow-shaped flow channel, 3-2-Rhombus-shaped flow channel, 3-3-First trapezoidal flow channel, 3-4-Second trapezoidal flow channel, 3-5-Rectangular flow channel, 4-1-A set of circular through holes above the arrow-shaped flow channel 3-1, 4-2-A set of circular through holes above the rhombus-shaped flow channel, 4-3-A set of circular through holes above the first trapezoidal flow channel, 4-4-A set of circular through holes above the second trapezoidal flow channel.

[0028] Figure 2 The diagram shows the reflection coefficients of the metasurface shown in this invention under four conditions. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0030] As shown in Figure 1, Figure 1A This is a top view of a frequency-reconfigurable metasurface unit based on liquid metal. Figure 1B This is a left view of the reconfigurable metasurface unit at this frequency. The following is in conjunction with... Figure 1A , Figure 1B Further explanation of the present invention:

[0031] A frequency-reconfigurable metasurface based on liquid metal includes an upper dielectric cover plate 1, a lower dielectric substrate 2, microchannels 3, circular vias 4, a metal ground plate 5, and liquid metal 6. The circular vias 4 are etched on the upper dielectric cover plate 2. The microchannels 3 are etched on the upper surface of the lower dielectric substrate 1, and the lower surface is the metal ground plate 5. The microchannels 3 are channels through which the liquid metal 6 flows.

[0032] Furthermore, the materials of the lower dielectric substrate 2 and the upper dielectric cover plate 1 are PDMS, with a relative permittivity of 2.67, a tangent angle loss of 0.0375, and length W0 and width L0 of 30mm and 32mm, respectively; the thickness H0 of the upper dielectric cover plate 1 is 0.5mm; the thickness H1 of the lower dielectric substrate 2 is 2.5mm; the thickness H2 of the microchannel 3 is 0.1mm, the length L1 of the microchannel connected by a straight line between two adjacent states is 1mm, the width W1 is 0.4mm, the upper base S0 of the trapezoidal structure is 2mm, and the lower base S1 is 3.5mm; the diameter d of the circular through hole 4 is 1mm; and the height Hg of the metal ground plate 5 is 0.7mm.

[0033] The metal floor 5 is bonded to the lower surface of the lower dielectric substrate 2. The length and width of the metal floor 5 are the same as those of the lower dielectric substrate 2, with a length of 30 mm and a width of 32 mm.

[0034] Furthermore, the microchannel 3 includes: an arrow-shaped channel 3-1, a rhombus-shaped channel 3-2, a first trapezoidal channel 3-3, a second trapezoidal channel 3-4, and a rectangular channel 3-5, with adjacent channels connected by the rectangular channel 3-5. The arrow-shaped channel 3-1 includes two arrows, pointing in opposite directions, with their middle portions connected. Both ends of each arrow are connected to the rhombus-shaped channel 3-2 via the rectangular channel 3-5. The rhombus-shaped channel 3-2 includes two symmetrically distributed channels. One set of two adjacent sides of the rhombus-shaped channel 3-2 is connected to the rhombus-shaped channel 3-2 via the rectangular channel 3-5, and the other set of two adjacent sides is connected to the first trapezoidal channel 3-3 via the rectangular channel 3-5. The first trapezoidal channel 3-3 includes a pair of channels located at the upper end of the arrow-shaped channel 3-1. There are four trapezoidal channels 3-3 in total: two symmetrically distributed channels at the top of the arrow-shaped channel 3-1 and two symmetrically distributed channels at the bottom of the arrow-shaped channel 3-1. The upper bottom edge of the first trapezoidal channel 3-3 is connected to the rhomboid channel 3-2 through the rectangular channel 3-5, and the lower bottom edge is connected to the second trapezoidal channel 3-4 through the rectangular channel 3-5. The second trapezoidal channel 3-4 includes two symmetrically distributed channels at the top of the arrow-shaped channel 3-1 and two symmetrically distributed channels at the bottom of the arrow-shaped channel 3-1, for a total of four. The upper bottom edge of the second trapezoidal channel 3-4 is connected to the first trapezoidal channel 3-3 through the rectangular channel 3-5.

[0035] Furthermore, the circular through holes 4 include: a set of circular through holes 4-1 above the arrow-shaped flow channel 3-1, a set of circular through holes 4-2 above the rhomboid flow channel, a set of circular through holes 4-3 above the first trapezoidal flow channel, and a set of circular through holes 4-4 above the second trapezoidal flow channel, with each set of circular through holes being centrally symmetrical.

[0036] Specifically, the circular through holes 4 are located at the inlet or outlet of each flow channel. A group of circular through holes 4-1 above the arrow-shaped flow channel 3-1 includes 6 through holes, of which 2 are located in the middle of the arrow and 4 are located at the outlet of the arrow. A group of circular through holes 4-2 above the rhomboid flow channel includes 2 through holes, located at the outlet connected to the first trapezoidal flow channel 3-3. A group of circular through holes 4-3 above the first trapezoidal flow channel includes 1 through hole, located at the outlet connected to the second trapezoidal flow channel 3-4. A group of circular through holes 4-4 above the second trapezoidal flow channel includes 1 through hole, located at the outlet.

[0037] The upper dielectric cover plate 1 and the lower dielectric substrate 2 are bonded together to prevent leakage of liquid metal 6. By driving the liquid metal 6 to flow to the position of arrow-shaped flow channel 3-1, diamond-shaped flow channel 3-2, first trapezoidal flow channel 3-3 or second trapezoidal flow channel 3-4 by external force, the resonant frequency of the metasurface can be changed.

[0038] Furthermore, the reconfigurable metasurface of this invention achieves four different resonant frequencies by adjusting the liquid metal 6, specifically:

[0039] The first state is that liquid metal 6 flows into the arrow-shaped flow channel 3-1, achieving a frequency of 6.8 GHz; the second state is that liquid metal 6 flows into the arrow-shaped flow channel 3-1 and the diamond-shaped flow channel 3-2, achieving a frequency of 4.95 GHz; the third state is that liquid metal 6 flows into the arrow-shaped flow channel 3-1, the diamond-shaped flow channel 3-2, and the first trapezoidal flow channel 3-3, achieving a frequency of 3.4 GHz; the fourth state is that liquid metal 6 flows into the arrow-shaped flow channel 3-1, the diamond-shaped flow channel 3-2, the first trapezoidal flow channel 3-3, and the second trapezoidal flow channel 3-4, achieving a frequency of 2.45 GHz.

[0040] Furthermore, the liquid metal flows within the microchannels driven by external force. When the liquid metal 6 is extracted, sodium hydroxide solution is added to the microchannels 3 to remove surface oxides, making it more fluid.

[0041] At room temperature, metallic mercury is the only heavy liquid metal with high electrical conductivity. However, mercury can evaporate at room temperature, and mercury vapor is highly toxic and can cause significant harm to the human body. Alternatively, a special alloy of mercury and iron, prepared in a specific ratio, can also be liquid at room temperature and possesses similar physical properties to mercury. The difference is that the iron alloy is non-toxic and harmless. Therefore, the liquid metal 6 flowing within the microchannel 3 is an iron alloy (EGaIn).

[0042] like Figure 2 The figure shows the reflection coefficient of the metasurface as a function of frequency. Each state corresponds to a resonant frequency, and the resonance depth of each resonant frequency is below -20dB. In the second state, the resonance depth reaches below -40dB. The reconfigurable metasurface of this invention can be used as an absorbing material to achieve aircraft stealth in airborne antennas, and its stealth effect is significantly better than that of traditional reconfigurable metasurfaces.

[0043] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the scope of the technology disclosed in the present invention, and such modifications or substitutions should all be covered within the scope of protection of the present invention.

Claims

1. A frequency-reconfigurable metasurface based on liquid metal, characterized in that... It includes an upper dielectric cover plate (1), a lower dielectric substrate (2), microchannels (3), circular through holes (4), a metal ground plate (5), and liquid metal (6); the upper dielectric cover plate (2) is etched with circular through holes (4); the upper surface of the lower dielectric substrate (1) is etched with microchannels (3), and the lower surface is a metal ground plate (5); the microchannels (3) are channels for the flow of liquid metal (6); The metal floor (5) is bonded to the lower surface of the lower dielectric substrate (2); The microchannel (3) includes: an arrow-shaped channel (3-1), a rhombus-shaped channel (3-2), a first trapezoidal channel (3-3), a second trapezoidal channel (3-4), and a rectangular channel (3-5). Adjacent channels are connected by a rectangular channel (3-5). The arrow-shaped channel (3-1) includes two arrows pointing in opposite directions, with their middle portions connected. Both ends of each arrow are connected to the rhombus-shaped channel (3-2) via a rectangular channel (3-5). The rhombus-shaped channel (3-2) includes two symmetrically distributed channels. One set of two adjacent sides of the rhombus-shaped channel (3-2) is connected to the rhombus-shaped channel (3-2) via a rectangular channel (3-5), and the other set of two adjacent sides is connected to the rhombus-shaped channel (3-2) via a rectangular channel (3-5). A trapezoidal flow channel (3-3) is connected; the first trapezoidal flow channel (3-3) includes two symmetrically distributed at the upper end of the arrow-shaped flow channel (3-1) and two symmetrically distributed at the lower end of the arrow-shaped flow channel (3-1), for a total of 4. The upper base of the first trapezoidal flow channel (3-3) is connected to the rhomboid flow channel (3-2) through the rectangular flow channel (3-5), and the lower base is connected to the second trapezoidal flow channel (3-4) through the rectangular flow channel (3-5); the second trapezoidal flow channel (3-4) includes two symmetrically distributed at the upper end of the arrow-shaped flow channel (3-1) and two symmetrically distributed at the lower end of the arrow-shaped flow channel (3-1), for a total of 4. The upper base of the second trapezoidal flow channel (3-4) is connected to the first trapezoidal flow channel (3-3) through the rectangular flow channel (3-5); The circular through-hole 4 includes: a set of circular through-holes (4-1) above the arrow-shaped flow channel (3-1), a set of circular through-holes (4-2) above the rhomboid flow channel, a set of circular through-holes (4-3) above the first trapezoidal flow channel, and a set of circular through-holes (4-4) above the second trapezoidal flow channel, with each set of circular through-holes being centrally symmetrical. The circular through holes 4 are located at the inlet or outlet of each flow channel. A group of circular through holes (4-1) above the arrow-shaped flow channel (3-1) includes 6 through holes, of which 2 are located in the middle of the arrow and 4 are located at the outlet of the arrow. A group of circular through holes (4-2) above the rhomboid flow channel includes 2 through holes, located at the outlet connected to the first trapezoidal flow channel (3-3). A group of circular through holes (4-3) above the first trapezoidal flow channel includes 1 through hole, located at the outlet connected to the second trapezoidal flow channel (3-4). A group of circular through holes (4-4) above the second trapezoidal flow channel includes 1 through hole, located at the outlet. The upper dielectric cover plate (1) and the lower dielectric substrate (2) are bonded together to prevent the liquid metal (6) from leaking. The resonant frequency of the metasurface can be changed by driving the liquid metal (6) to flow to the position of the arrow-shaped flow channel (3-1), the rhomboid flow channel (3-2), the first trapezoidal flow channel (3-3), or the second trapezoidal flow channel (3-4) by external force. Four different resonant frequencies are achieved by adjusting the liquid metal (6), specifically: The first state is that liquid metal (6) flows into the arrow-shaped flow channel (3-1), achieving a frequency of 6.8 GHz; the second state is that liquid metal (6) flows into the arrow-shaped flow channel (3-1) and the diamond-shaped flow channel (3-2), achieving a frequency of 4.95 GHz; the third state is that liquid metal (6) flows into the arrow-shaped flow channel (3-1), the diamond-shaped flow channel (3-2), and the first trapezoidal flow channel (3-3), achieving a frequency of 3.4 GHz; the fourth state is that liquid metal (6) flows into the arrow-shaped flow channel (3-1), the diamond-shaped flow channel (3-2), the first trapezoidal flow channel (3-3), and the second trapezoidal flow channel (3-4), achieving a frequency of 2.45 GHz.

2. The frequency-reconfigurable metasurface based on liquid metal according to claim 1, characterized in that... The materials of the lower dielectric substrate and the upper dielectric cover plate are PDMS, with a relative permittivity of 2.67 and a tangent angle loss of 0.0375.

3. The frequency-reconfigurable metasurface based on liquid metal according to claim 1, characterized in that: The liquid metal is a gallium-indium alloy EGaIn.

4. The frequency-reconfigurable metasurface based on liquid metal according to claim 1, characterized in that: When extracting liquid metal, sodium hydroxide solution is added to the microchannel to remove surface oxides and make it more fluid.

5. An application of the frequency-reconfigurable metasurface based on liquid metal as described in any one of claims 1-4, characterized in that: This metasurface element can be used to replace absorbing materials in airborne antennas to achieve aircraft stealth.

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