Liquid metal reconfigurable metasurface reflection unit and manufacturing method thereof

Abstract

The invention relates to a liquid metal reconfigurable metasurface reflection unit and a manufacturing method thereof, and belongs to the technical field of artificial electromagnetic materials. The problems that an existing metasurface reflection unit structure is discrete and limited in regulation state, insufficient in continuous adjustment capacity, narrow in adjustment bandwidth and small in reflection phase shift range are solved. Comprising a flexible substrate, a flexible film, a flexible upper cover plate, a driving control structure and a grounding plate, the flexible upper cover plate, the flexible thin film, the flexible substrate, the grounding plate and the driving control structure are stacked in sequence; a micro-channel array structure and a liquid injection port are arranged on the flexible substrate, the micro-channel array structure comprises a plurality of unit micro-channel structures, the plurality of unit micro-channel structures are communicated through through holes, and each unit micro-channel structure is of a bent cross-shaped structure and comprises a liquid storage tank and four semicircular cross arm channels. The metasurface reflection unit is continuous and reconfigurable in structure and has the advantages of being insensitive to polarization and incident angle and large in reflection phase shift range.

Description

Technical Field

[0001] The present invention relates to the technical field of artificial electromagnetic materials, and in particular to a liquid metal reconfigurable supersurface reflection unit and a manufacturing method thereof. Background Art

[0002] Metasurface is an ultra-thin artificial microstructure with special control properties for electromagnetic waves. Its subwavelength structure can flexibly control the reflected electromagnetic wave spectrum and wavefront at the subwavelength scale, producing many special electromagnetic phenomena that cannot be achieved by natural materials, such as controlling the phase, polarization and amplitude of electromagnetic waves. Its thickness is much smaller than the wavelength, the loss is small and it is easy to process. It has broad application prospects in the fields of sensing, detection, imaging, stealth, micro-nano processing, etc.

[0003] Traditional metasurfaces are mostly sandwich structures of "metal resonance layer-dielectric layer-metal ground plane". Their processing and manufacturing have mature processes, but their electromagnetic characteristics cannot be changed after processing, so it is difficult to adapt to the needs of reconfiguration. In order to achieve the adjustable performance of the metasurface, the structural characteristics of the metasurface can be changed to adjust the performance of electromagnetic wave reflection. Some research teams have achieved the adjustable function of the metasurface by using active devices, electrically controlled devices, PIN diodes, MEMS devices, etc. However, the bandwidth of the metasurface regulated by active devices is narrow, and the device has only two states, on and off, which leads to the unit having only limited discrete electromagnetic response regulation states; and the active device needs to be powered on to maintain, which has a high power consumption bottleneck; the electrically controlled device has a working frequency band limit, and the metasurface structure is difficult to apply in the high frequency band, and the nonlinearity is obvious; and the welding of the electrically controlled device will cause the surface of the structure to be uneven, affecting the integrated application of the metasurface structure with other structures. Therefore, it is necessary to study new control methods and unit forms to achieve broadband electromagnetic response continuous control capabilities.

[0004] In recent years, liquid metal (gallium-based alloy) is often used in reconfigurable electromagnetic devices, such as liquid metal antennas, liquid metal metasurfaces, etc. Gallium-based alloys have the advantages of low melting point, high-precision control of flow response, electrical continuity, high ductility, and properties that are not affected by electromagnetic frequency bands. By utilizing the arbitrary fluidity of liquid metal and preparing a microfluidic packaging structure to make the liquid metal flow in the flow channel, it can replace the solid metal part in the metasurface structure and realize the continuous reconfiguration of the electromagnetic response state by controlling its flow in the flow channel. However, the existing application of liquid metal in microfluidic structure is still in its infancy, and there are few reports on the influence of the shape of liquid metal in the microfluidic structure on the performance of the metasurface. Summary of the invention

[0005] In view of the above analysis, the embodiments of the present invention aim to provide a liquid metal reconfigurable metasurface reflection unit and a manufacturing method thereof, so as to solve at least one of the following problems of the existing metasurface reflection unit structure: 1. The control state of the existing metasurface reflection unit structure is discrete and limited; 2. The existing metasurface reflection unit structure has insufficient continuous adjustment capability and a narrow adjustment bandwidth; 3. The existing metasurface reflection unit structure has a small reflection phase shift range.

[0006] The purpose of the present invention is mainly achieved through the following technical solutions:

[0007] On the one hand, the present invention provides a liquid metal reconfigurable metasurface reflection unit, comprising: a flexible substrate, a flexible film, a flexible upper cover plate, a driving control structure and a ground plate;

[0008] The flexible upper cover plate, the flexible film, the flexible substrate, the ground plate and the drive control structure are stacked in sequence;

[0009] A microfluidic array structure and a liquid injection port are arranged on the flexible substrate. The microfluidic array structure includes a plurality of unit microfluidic structures. The plurality of unit microfluidic structures are connected. The unit microfluidic structure is a curved cross-shaped structure including a liquid storage tank and four semicircular cross-arm flow channels.

[0010] Furthermore, the microfluidic channel array structure is used to provide flow channels for liquid metal and driving liquid; the driving control structure is used to control the flow state of liquid metal in multiple unit microfluidic channel structures; and the ground plate is used to reflect electromagnetic waves.

[0011] Furthermore, the liquid reservoir is located in the center of the unit microfluidic channel structure, the four semicircular cross-arm flow channels are arranged around the liquid reservoir, and are interconnected through the liquid reservoir, and the four semicircular cross-arm flow channels all extend in a direction away from the liquid reservoir.

[0012] Further, the four semicircular cross-arm flow channels include a first semicircular cross-arm flow channel, a second semicircular cross-arm flow channel, a third semicircular cross-arm flow channel and a fourth semicircular cross-arm flow channel;

[0013] The first semicircular arc cross arm flow channel and the third semicircular arc cross arm flow channel are centrally symmetrically distributed, and the second semicircular arc cross arm flow channel and the fourth semicircular arc cross arm flow channel are centrally symmetrically distributed.

[0014] Furthermore, the included angle between adjacent semicircular arc-shaped cross-arm flow channels is 90°.

[0015] Furthermore, the flexible film is bonded to the flexible substrate by heat pressing, the flexible upper cover is bonded to the flexible film by spraying glue, and an air cavity structure having the same structure as the unit microchannel structure is manufactured in the flexible upper cover;

[0016] The driving control structure is connected to the liquid injection port on the flexible substrate via an external conduit;

[0017] The ground plate is glued to the flexible substrate and the driving control structure respectively.

[0018] Furthermore, the flexible substrate, the flexible film and the flexible upper cover plate together form a flexible packaging structure, the thickness h1 of the flexible substrate is 3-6 mm, the thickness of the flexible film is 10-50 μm, and the thickness h2 of the flexible upper cover plate is 1.5-3 mm.

[0019] Furthermore, the height t2 of the air cavity structure is 0.7-1.2 mm.

[0020] Furthermore, the size variation range of the liquid metal in the liquid metal reconfigurable metasurface reflection unit is 30°<J<180°, where J is the arc angle of the liquid metal when flowing in the semicircular cross-arm flow channel.

[0021] On the other hand, the present invention also provides a method for manufacturing a liquid metal reconfigurable metasurface reflection unit, which is used to prepare the liquid metal reconfigurable metasurface reflection unit, comprising:

[0022] S1: determining the shape and initial size of a unit microfluidic channel structure, wherein the unit microfluidic channel structure is a semicircular cross arm structure;

[0023] S2: Designing a microfluidic array structure according to the shape, initial size and initial arrangement period of the unit microfluidic structure, and designing the shape and initial size of the flexible substrate and the flexible upper cover according to the microfluidic array structure;

[0024] S3: Input the shape, initial size and initial arrangement period of the unit microfluidic channel structure, the shape and initial size of the flexible substrate and the flexible upper cover plate, and the initial size of the flexible film into the electromagnetic simulation software to obtain the initial metasurface reflection unit model;

[0025] S4: Input the material parameters of the flexible substrate, liquid metal and driving liquid, use electromagnetic simulation software to perform multiple parameter sweep iterations on the initial metasurface reflection unit model, obtain the final metasurface reflection unit model, and determine the dimensions of the unit microfluidic structure, flexible substrate, flexible film and flexible upper cover in the final metasurface reflection unit model as the final dimensions;

[0026] S5: According to the final metasurface reflection unit model, a unit microfluidic structure, a flexible substrate and a flexible upper cover plate that meet the shape and size requirements are manufactured;

[0027] S6: Fabrication of microfluidic array structures and injection ports on flexible substrates;

[0028] S7: According to the final metasurface reflection unit model, a flexible film is bonded on a flexible substrate by using a hot pressing method; an air cavity structure having the same shape as the unit microchannel structure is opened in the flexible upper cover plate;

[0029] S8: injecting a driving liquid through the injection port, and the driving liquid is injected into the flow channel of each unit microfluidic channel structure through the through holes between the unit microfluidic channel structures; injecting liquid metal through the injection port, and the liquid metal is injected into the flow channel of each unit microfluidic channel structure through the through holes between the unit microfluidic channel structures;

[0030] S9: The flexible upper cover plate is bonded to the flexible film by spraying glue; a ground plate is arranged under the flexible substrate; a driving control structure is arranged under the ground plate, and the driving control structure is connected to the liquid injection port to obtain a metasurface reflection unit.

[0031] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0032] 1. The liquid metal reconfigurable metasurface reflection unit of the present invention adopts a microchannel array composed of liquid metal and a plurality of semicircular cross-arm unit microchannel structures to replace the fixed metal array of the conventional metasurface structure, and realizes continuous reconfiguration of the resonant frequency and reflection phase of the reflection unit by controlling the continuous adjustability of the liquid metal in the semicircular cross-arm channel, thereby solving the problems of limited control state and insufficient continuous adjustment capability faced by conventional metasurface units that use components such as PIN diodes to adjust the electromagnetic response state.

[0033] 2. The liquid metal reconfigurable metasurface reflection unit of the present invention increases the liquid metal size adjustment range and expands the reflection phase adjustment range by bending the flow channel of the cross-shaped structure. It has the functions of polarization insensitivity, incident angle insensitivity, continuously adjustable electromagnetic response, and continuously adjustable reflection phase over a large range. It can be applied to radar camouflage stealth, dynamic reconfigurable communications and other fields.

[0034] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0036] Figure 1 This is a distribution diagram of liquid metal and driving liquid in a liquid metal reconfigurable metasurface reflection unit according to an embodiment of the present invention;

[0037] Figure 2 A top view of a unit microchannel structure of a liquid metal reconfigurable metasurface reflection unit according to an embodiment of the present invention;

[0038] Figure 3 A cross-sectional view of a liquid metal reconfigurable metasurface reflective unit according to an embodiment of the present invention;

[0039] Figure 4 A schematic diagram of the flow of liquid metal in a liquid metal reflection unit according to an embodiment of the present invention;

[0040] Figure 5 A frequency dynamic reconfigurable graph of a liquid metal reflection unit according to an embodiment of the present invention;

[0041] Figure 6 This is a reflection phase range diagram of the liquid metal reflection unit according to an embodiment of the present invention;

[0042] Figure 7 A top view of a unit microchannel structure of a liquid metal reflection unit of a comparative example;

[0043] Figure 8 It is the frequency dynamic reconfigurable diagram of the comparative liquid metal reflection unit;

[0044] Fig. 9 is a reflection phase range diagram of a comparative liquid metal reflection unit;

[0045] Fig.10 A comparison diagram of the reflection phase range of the liquid metal reflection unit of the embodiment of the present invention and the comparative example;

[0046] Fig.11 is the center frequency (f) of the liquid metal reflector unit under X and Y polarization in the embodiment of the present invention 0＝ 8GHz) reflection phase contrast diagram;

[0047] Fig.12 is the center frequency (f) of the liquid metal reconfigurable metasurface reflection unit under different incident angles in the embodiment of the present invention. 0＝ 8GHz) reflection phase contrast diagram.

[0048] Reference numerals:

[0049] 1-liquid metal; 2-microfluidic channel array structure; 21-liquid storage tank; 22-first semicircular cross-arm channel; 23-second semicircular cross-arm channel; 24-third semicircular cross-arm channel; 25-fourth semicircular cross-arm channel; 3-driving liquid; 4-flexible substrate; 5-flexible film; 6-flexible upper cover plate; 7-air cavity structure; 8-driving control structure; 9-ground plate. DETAILED DESCRIPTION

[0050] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0051] The present invention provides a liquid metal reconfigurable metasurface reflection unit, comprising: a flexible substrate 4, a flexible film 5, a flexible upper cover plate 6, a driving control structure 8 and a ground plate 9;

[0052] The flexible upper cover plate 6, the flexible film 5, the flexible substrate 4, the ground plate 9 and the drive control structure 8 are stacked in sequence;

[0053] The flexible substrate 4 is provided with a microfluidic array structure 2 and a liquid injection port, wherein the microfluidic array structure 2 includes a plurality of unit microfluidic structures, wherein the plurality of unit microfluidic structures are connected, and the unit microfluidic structure is a curved cross-shaped structure, including a liquid reservoir 21 and four semicircular cross-arm flow channels, wherein the four semicircular cross-arm flow channels include a first semicircular cross-arm flow channel 22, a second semicircular cross-arm flow channel 23, a third semicircular cross-arm flow channel 24 and a fourth semicircular cross-arm flow channel 25, wherein the liquid reservoir 21 is located at the unit microfluidic structure. The four semicircular cross-arm flow channels are arranged around the liquid reservoir 21 and are interconnected through the liquid reservoir 21. The four semicircular cross-arm flow channels all extend away from the liquid reservoir 21. The first semicircular cross-arm flow channel 22 and the third semicircular cross-arm flow channel 24 are symmetrically distributed around the center, the second semicircular cross-arm flow channel 23 and the fourth semicircular cross-arm flow channel 25 are symmetrically distributed around the center, and the angle between adjacent semicircular cross-arm flow channels is 90°. The injection port is arranged on the side of the flexible substrate and is connected to the unit microfluidic channel structure.

[0054] The flexible film 5 is bonded to the flexible substrate 4 by heat pressing, the flexible upper cover plate 6 is bonded to the flexible film 5 by spraying glue, and the flexible upper cover plate 6 is provided with an air cavity structure 7 which is the same as the unit microchannel structure;

[0055] The driving control structure 8 is connected to the liquid injection port on the flexible substrate 4 through an external conduit, and is used to control the flow state of the liquid metal in the multiple unit microfluidic channel structures, such as position and shape;

[0056] The two sides of the ground plate 9 are respectively glued to the flexible substrate 4 and the drive control structure 8 .

[0057] Specifically, the flexible substrate 4, the flexible film 5, and the flexible upper cover plate 6 together form a flexible packaging structure, the thickness h1 of the flexible substrate 4 is 3-6 mm, the thickness of the flexible film 5 is 10-50 μm, and the thickness h2 of the flexible upper cover plate 6 is 1.5-3 mm;

[0058] A plurality of unit microfluidic channel structures are arranged in an array on the flexible substrate 4, such as Figure 1 and Figure 4 As shown, the liquid metal 1 is distributed in the liquid storage tank 21 and the four semicircular cross-arm flow channels connected to the liquid storage tank, and the driving liquid is distributed at the ends of the four semicircular cross-arm flow channels; in the microchannel array structure, under the pressure drive of the driving control structure 8, the driving liquid 3 drives the liquid metal 1 to flow continuously in multiple unit microchannel structures, and changes at different flow positions and shapes in the four semicircular cross-arm flow channels of the multiple unit microchannel structures, thereby reconstructing the structural morphology of the liquid metal 1. Each change in the flow position and shape of the liquid metal 1 in the microchannel structure corresponds to a working state of the metasurface, so as to realize dynamic adjustment of the metasurface performance under multiple states. The size change range of the liquid metal when flowing in the semicircular cross-arm flow channel in the liquid metal reconfigurable metasurface reflection unit is 30°<J<180°, where J is the arc angle of the liquid metal when flowing in the semicircular cross-arm flow channel (such as Figure 1 The size and shape changes of liquid metal will change its resonant structure, which will lead to changes in its response frequency, reflection phase and working state, making it possible to dynamically reconfigure the resonant frequency in the C and X bands and continuously and dynamically adjust the reflection phase.

[0059] Specifically, the flexible film 5 is bonded to the flexible substrate by heat compression, so as to seal the liquid metal 1 and the driving liquid 3 to avoid leakage.

[0060] Specifically, an air cavity structure 7 having the same structure as the unit microfluidic channel structure is manufactured in the flexible upper cover plate 6. The height t2 of the air cavity structure 7 is 0.7-1.2 mm, which is slightly higher than the height t1 of the microfluidic channel array structure to accommodate the volume changes of the liquid in the multiple unit microfluidic channel structures.

[0061] Specifically, a plurality of unit microfluidic structures are prepared on a flexible substrate 4 to form a microfluidic array structure 2. The unit resonant structure and its size parameters of the unit microfluidic structure are designed based on the relative dielectric constant, loss tangent, and conductivity material parameters of the flexible substrate, liquid metal, and driving liquid. In order to increase the control range of the reflection phase of the metasurface unit, the unit resonant structure is designed as a semicircular cross-arm structure, which increases the adjustment range of the liquid metal resonance part and broadens the control range of the reflection phase; and according to the unit resonant structure and the flow mode of the liquid metal, a square liquid storage tank is designed at the center connection of the semicircular cross-arm flow channel structure to facilitate the storage of liquid when injecting the driving liquid. The unit microfluidic structure is realized by micro-nano processing technology, including photolithography, nanoimprinting and other process methods. The specific parameters of the microfluidic array structure 2 are: the arrangement period P of the unit microfluidic structure is 13-17 mm, the width w1 of the semicircular cross-arm flow channel is 0.2-0.6 mm, the arc radius r1 of the semicircular cross-arm flow channel is 3-3.5 mm, the liquid reservoir width l1 is 1.5-2.5 mm, and the microfluidic array height t1 is 0.05-0.3 mm.

[0062] Optionally, the flexible substrate 4 , the flexible film 5 , and the flexible upper cover plate 6 are made of materials such as PDMS, PMMA, SEBS, and PET.

[0063] Optionally, the liquid metal is a gallium-indium-tin alloy.

[0064] Optionally, the driving liquid is an alkaline solution, preferably, the alkaline solution is a NaOH solution, and the NaOH driving liquid is injected into the microchannel array structure through the injection port on the flexible substrate 4 before the liquid metal 1. The early injection of the driving liquid can play a wetting role, facilitate the flow of the liquid metal, and also remove the oxide layer on the surface of the liquid metal.

[0065] Optionally, the material of the ground plate 9 is metal, which is used to reflect electromagnetic waves, and materials such as aluminum and copper may be used.

[0066] The present invention also provides a method for manufacturing a liquid metal reconfigurable metasurface reflection unit, which is used to manufacture the liquid metal reconfigurable metasurface reflection unit, comprising the following steps:

[0067] S1: determining the shape and initial size of a unit microfluidic channel structure, wherein the unit microfluidic channel structure is a semicircular cross arm structure;

[0068] S2: Designing a microfluidic array structure according to the shape, initial size and initial arrangement period of the unit microfluidic structure, and designing the shape and initial size of the flexible substrate and the flexible upper cover according to the microfluidic array structure;

[0069] S3: Input the shape, initial size and initial arrangement period of the unit microfluidic channel structure, the shape and initial size of the flexible substrate and the flexible upper cover plate, and the initial size of the flexible film into the electromagnetic simulation software to obtain the initial metasurface reflection unit model;

[0070] S4: Input the material parameters of the flexible substrate, liquid metal and driving liquid, use electromagnetic simulation software to perform multiple parameter sweep iterations on the initial metasurface reflection unit model, obtain the final metasurface reflection unit model, and determine the dimensions of the unit microfluidic structure, flexible substrate, flexible film and flexible upper cover in the final metasurface reflection unit model as the final dimensions;

[0071] S5: According to the final metasurface reflection unit model, a unit microfluidic structure, a flexible substrate and a flexible upper cover plate that meet the shape and size requirements are manufactured;

[0072] S6: Fabrication of microfluidic array structures and injection ports on flexible substrates;

[0073] S7: According to the final metasurface reflection unit model, a flexible film is bonded on a flexible substrate by using a hot pressing method; an air cavity structure having the same shape as the unit microchannel structure is opened in the flexible upper cover plate;

[0074] S8: injecting a driving liquid through the injection port, and the driving liquid is injected into the flow channel of each unit microfluidic channel structure through the through holes between the unit microfluidic channel structures; injecting liquid metal through the injection port, and the liquid metal is injected into the flow channel of each unit microfluidic channel structure through the through holes between the unit microfluidic channel structures;

[0075] S9: The flexible upper cover plate is bonded to the flexible film by spraying glue; a ground plate is arranged under the flexible substrate; a driving control structure is arranged under the ground plate, and the driving control structure is connected to the liquid injection port to obtain a metasurface reflection unit.

[0076] Specifically, in step S4, the material parameters of the flexible substrate, liquid metal and driving liquid include the relative dielectric constant, loss tangent and conductivity of the material; when the metasurface reflection unit model simultaneously satisfies: the resonant frequency of the metasurface unit model has a reconfigurable range of 4-12 GHz in the C and X bands; the reflection phase change range of the metasurface unit model with the change of the liquid metal size is ≥180°, the iteration can be stopped to obtain the final metasurface reflection unit model.

[0077] The liquid metal reconfigurable metasurface reflection unit of the present invention adopts a microchannel array composed of liquid metal and a plurality of semicircular cross-arm unit microchannel structures to replace the fixed metal array of the conventional metasurface structure, and realizes continuous reconfiguration of the resonant frequency and reflection phase of the reflection unit by controlling the continuous adjustability of the liquid metal in the semicircular cross-arm channel, thereby solving the problems of limited control state and insufficient continuous adjustment capability faced by conventional metasurface units that use components such as PIN diodes to adjust the electromagnetic response state.

[0078] Example 1

[0079] The liquid metal reconfigurable metasurface reflective unit of this embodiment is as follows: Figure 1 , Figure 2 and Figure 3 As shown, it includes: a flexible substrate 4, a flexible film 5, a flexible upper cover plate 6, a drive control structure 8 and a ground plate 9;

[0080] The flexible upper cover plate 6, the flexible film 5, the flexible substrate 4, the ground plate 9 and the drive control structure 8 are stacked in sequence;

[0081] The flexible substrate 4 is provided with a microfluidic array structure 2 and a liquid injection port, wherein the microfluidic array structure includes a plurality of unit microfluidic structures, wherein the plurality of unit microfluidic structures are connected by through holes, wherein the unit microfluidic structure is a curved cross-shaped structure, including a liquid reservoir 21 and four semicircular cross-arm flow channels, wherein the four semicircular cross arms include a first semicircular cross-arm flow channel 22, a second semicircular cross-arm flow channel 23, a third semicircular cross-arm flow channel 24 and a fourth semicircular cross-arm flow channel 25 ... microfluidic array structure includes a plurality of unit microfluidic structures, wherein the microfluidic array structure includes a plurality of unit microfluidic structures, wherein the microfluidic array structure includes a plurality of unit microfluidic structures, wherein the microfluidic array structure includes a plurality of unit microfluidic structures, wherein the microfluidic array structure includes a plurality of unit microfluidic structures, wherein the microfluidic array structure includes a plurality of unit microfluidic structures, wherein the microfluidic array structure includes a plurality of unit microfluidic structures, wherein the microfluidic array structure includes a plurality of unit microfluidic structures, wherein the microfluidic array structure includes a plurality of unit microfluidic structures, wherein the microfluidic array structure includes a plurality of unit microfluidic structures, wherein the microfluidic array structure includes a plurality The liquid reservoir 21 is located in the center of the microfluidic channel structure, the four semicircular cross-arm flow channels are arranged around the liquid reservoir 21, and are interconnected through the liquid reservoir 21. The four semicircular cross-arm flow channels all extend in a direction away from the liquid reservoir 21. The first semicircular cross-arm flow channel 22 and the third semicircular cross-arm flow channel 24 are symmetrically distributed at the center, the second semicircular cross-arm flow channel 23 and the fourth semicircular cross-arm flow channel 25 are symmetrically distributed at the center, and the angle between adjacent semicircular cross-arm flow channels is 90°;

[0082] The flexible film 5 is bonded to the flexible substrate 4 by heat pressing, the flexible upper cover plate 6 is bonded to the flexible film 5 by spraying glue, and the flexible upper cover plate 6 is provided with an air cavity structure 7 which is the same as the unit microchannel structure;

[0083] The driving control structure 8 is connected to the liquid injection port on the flexible substrate 4;

[0084] The ground plate 9 is glued to the flexible substrate 4 and the driving control structure 8 respectively.

[0085] Specifically, the flexible substrate 4, the flexible film 5, and the flexible upper cover plate 6 together form a flexible packaging structure, the thickness h1 of the flexible substrate 4 is 4 mm, the thickness of the flexible film 5 is 40 μm, and the thickness h2 of the flexible upper cover plate 6 is 2 mm;

[0086] The height t2 of the air cavity structure 7 is 1 mm;

[0087] The specific parameters of the microfluidic array structure 2 are: the unit microfluidic structure arrangement period P is 15 mm, the width w1 of the semicircular cross-arm flow channel is 0.5 mm, the arc radius r1 of the semicircular cross-arm flow channel is 3.2 mm, the liquid reservoir width l1 is 2 mm, and the microfluidic array height t1 is 0.2 mm;

[0088] The materials of the flexible substrate 4, the flexible film 5 and the flexible upper cover plate 6 are SEBS rubber;

[0089] The liquid metal is a gallium-indium-tin alloy;

[0090] Driving liquid: NaOH solution;

[0091] The material of the ground plate 9 is aluminum;

[0092] like Figure 4 The figure shows the liquid metal flow diagram of the metasurface reflection unit of the present embodiment. It can be seen from the figure that the liquid metal 1 is distributed in the liquid storage tank 21 and the four semicircular cross-arm flow channels connected to the liquid storage tank, and the NaOH driving liquid is distributed at the ends of the four semicircular cross-arm flow channels; under the pressure drive of the driving control structure 8, the NaOH driving liquid drives the liquid metal 1 to flow continuously in the microchannel structure, and changes at different flow positions and shapes in the four semicircular cross-arm flow channels of the microchannel structure, thereby reconstructing the structural morphology of the liquid metal 1. Each change in the flow position and shape of the liquid metal 1 in the microchannel structure corresponds to a working state of the metasurface, so as to realize dynamic adjustment of the metasurface performance under multiple states. The size change of the liquid metal 1 in the semicircular cross-arm flow channel can be characterized by an angle J, and its adjustment range is 30°<J<180°.

[0093] Figure 5 This is a frequency dynamic reconfiguration diagram of the metasurface reflection unit of this embodiment. It can be seen that as the liquid metal flows in the microchannel, the resonant frequency of the metasurface reflection unit can be reconfigured within the range of 4.5 to 12 GHz.

[0094] Figure 6 This is a reflection phase range diagram of the metasurface reflection unit of this embodiment. It can be seen that within the C and X bands, the reflection phase control range of the metasurface reflection unit satisfies 180°.

[0095] Fig.11This is a reflection phase range diagram of the metasurface reflection unit of this embodiment at the center frequency (f0=8GHz) under X and Y polarizations. It can be seen that the unit has polarization insensitivity.

[0096] Fig.12 3 is a reflection phase range diagram of the metasurface reflection unit of this embodiment at the center frequency (f0=8GHz) under different incident angles. It can be seen that the unit has the characteristic of being insensitive to the incident angle.

[0097] Example 2

[0098] This embodiment provides a method for manufacturing the liquid metal reconfigurable metasurface reflection unit of Embodiment 1, comprising the following steps:

[0099] S1: According to the requirements of polarization insensitivity and incident angle insensitivity of the metasurface reflection unit, combined with the fluidic characteristics of liquid metal, the shape and initial size of the unit microfluidic channel structure are designed. The unit microfluidic channel structure is a semicircular cross arm structure;

[0100] Among them, the initial dimensions of the unit microchannel structure are: semicircular cross arm channel width w1 = 0.1 mm, semicircular cross arm radius r1 = 2.5 mm, and liquid reservoir width l1 = 1.4 mm;

[0101] S2: Designing a microfluidic array structure according to the shape, initial size and initial arrangement period of the unit microfluidic structure, and designing the shape and initial size of the flexible substrate and the flexible upper cover according to the microfluidic array structure;

[0102] Among them, the initial arrangement period P = 12mm, the microchannel array structure height t1 = 0.4mm, the flexible substrate and the flexible upper cover plate are rectangular parallelepiped structures, the thickness h1 of the flexible substrate is 2mm, the thickness h2 of the flexible upper cover plate 6 is 1.4mm, the air cavity 7 in the flexible upper cover plate 6 has the same shape as the unit microchannel structure, and the air cavity height t2 = 0.6mm;

[0103] S3: Input the shape, initial size and initial arrangement period of the unit microfluidic structure, the shape and initial size of the flexible substrate and the flexible upper cover, and the initial size of the flexible film into the CST electromagnetic simulation software to obtain the initial metasurface reflection unit model;

[0104] Among them, the initial thickness of the flexible film is 8 μm;

[0105] S4: Input the material parameters of the flexible substrate, liquid metal and driving liquid, and use CST electromagnetic simulation software to perform multiple parameter sweep iterations on the initial metasurface reflection unit until the iteration stop condition is met to obtain the final metasurface reflection unit model. The dimensions of the unit microfluidic structure, flexible substrate and flexible upper cover plate in the final metasurface reflection unit model are the final dimensions;

[0106] After multiple iterations, the resonant frequency of the final metasurface unit model is reconfigurable within the C and X bands to 4.5-12 GHz; the reflection phase of the final metasurface unit model changes by 180° as the size of the liquid metal changes;

[0107] At this time, in the final supersurface unit model, the specific parameters of the microfluidic array structure are: the unit microfluidic structure arrangement period P is 15mm, the width w1 of the semicircular cross-arm flow channel is 0.5mm, the arc radius r1 of the semicircular cross-arm flow channel is 3.2mm, the liquid reservoir width l1 is 2mm, and the microfluidic array height t1 is 0.2mm;

[0108] The thickness h1 of the flexible substrate 4 is 4 mm, the thickness of the flexible film 5 is 40 μm, and the thickness h2 of the flexible upper cover plate 6 is 2 mm;

[0109] The height t2 of the air cavity structure 7 is 1 mm.

[0110] S5: According to the final metasurface reflection unit model, a unit microfluidic structure, a flexible substrate and a flexible upper cover plate that meet the shape and size requirements are manufactured;

[0111] S6: According to the final metasurface reflection unit model, a microfluidic array structure and a liquid injection port are manufactured on a flexible substrate, wherein the microfluidic array structure includes a plurality of unit microfluidic structures, and each unit microfluidic structure is connected by a through hole;

[0112] S7: Based on the final metasurface reflective unit model, a flexible film is bonded on a flexible substrate using a hot pressing method;

[0113] S8: According to the final metasurface reflection unit model, an air cavity structure with the same shape as the unit microfluidic channel structure is manufactured in the flexible upper cover plate, and the height of the air cavity structure is greater than the height of the microfluidic channel array structure;

[0114] S9: injecting a driving liquid through the injection port, and injecting the driving liquid into the flow channel of each unit microfluidic channel structure through the through holes between the unit microfluidic channel structures;

[0115] S10: injecting liquid metal through the injection port, and the liquid metal is injected into the flow channel of each unit microfluidic channel structure through the through holes between the unit microfluidic channel structures;

[0116] S11: bonding the flexible upper cover plate to the flexible film by spraying glue;

[0117] S12: Disposing a ground plate under the flexible substrate;

[0118] S13: A driving control structure is arranged under the ground plate, and the driving control structure is connected to the liquid injection port to obtain a metasurface reflection unit entity.

[0119] Comparative Example

[0120] The metasurface reflection unit of this comparative example includes: a flexible substrate, a flexible film, a flexible upper cover plate, a driving control structure and a ground plate;

[0121] The flexible upper cover plate, the flexible film, the flexible substrate, the ground plate and the drive control structure are stacked in sequence;

[0122] The flexible substrate is provided with a microfluidic array structure and a liquid injection port, wherein the microfluidic array structure includes a plurality of unit microfluidic structures, wherein the plurality of unit microfluidic structures are connected by through holes, wherein the unit microfluidic structure is a vertical cross-shaped structure, including a liquid reservoir and four mutually perpendicular rectangular cross-arm flow channels, wherein the liquid reservoir is located in the center of the microfluidic structure, and the four mutually perpendicular rectangular cross-arm flow channels are arranged around the liquid reservoir; the unit microfluidic structure is as follows Figure 7 As shown;

[0123] The flexible film is bonded to the flexible substrate by heat pressing, the flexible upper cover is bonded to the flexible film by spraying glue, and an air cavity structure having the same structure as the microchannel structure is manufactured in the flexible upper cover;

[0124] The driving control structure is connected to the liquid injection port on the flexible substrate;

[0125] The ground plate is glued to the flexible substrate and the driving control structure respectively.

[0126] Specifically, the flexible substrate, the flexible film, and the flexible upper cover plate together form a flexible packaging structure, the thickness h1 of the flexible substrate is 4 mm, the thickness of the flexible film is 40 μm, and the thickness h2 of the flexible upper cover plate is 2 mm;

[0127] The height t2 of the air cavity structure is 1 mm;

[0128] The specific parameters of the microfluidic array structure are: unit microfluidic structure arrangement period P = 15mm, rectangular cross arm channel width w1 = 0.2mm, channel length l2 = 5.9mm, liquid reservoir width l1 = 2mm, microfluidic array height t1 is 0.2mm; liquid metal flow control angle 0mm<l0<6mm.

[0129] The materials of the flexible substrate 4, the flexible film 5 and the flexible upper cover plate 6 are SEBS rubber;

[0130] The liquid metal is a gallium-indium-tin alloy;

[0131] Driving liquid: NaOH solution;

[0132] The material of the ground plate 9 is aluminum.

[0133] Figure 8 This is the frequency dynamic reconfiguration diagram of the metasurface reflection unit in this comparative example. It can be seen that as the liquid metal flows in the microchannel, the resonant frequency of the unit can be reconfigured within the range of 6 to 12 GHz. Fig. 9 This is the reflection phase range diagram of the comparison metasurface reflection unit. It can be seen that in the 6-12 GHz band, the reflection phase control range of the unit satisfies 180°.

[0134] By comparison, it can be seen that the resonant frequency of the metasurface reflection unit in Example 1 or Example 2 of the present invention can be reconfigured within the range of 4.5 to 12 GHz as the liquid metal flows in the microchannel; the resonant frequency of the metasurface reflection unit in the comparative example can be reconfigured within the range of 6 to 12 GHz as the liquid metal flows in the microchannel; the reconfigurable range of the metasurface reflection unit in Example 1 or Example 2 of the present invention is slightly wider than that of the comparative example. Fig.10 It can be seen that the reflection phase control range of the metasurface reflection unit in Example 1 or Example 2 of the present invention is wider than that of the comparative example.

[0135] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A liquid metal reconfigurable metasurface reflection unit, characterized in that: The liquid metal reconfigurable metasurface reflection unit comprises: a flexible substrate, a flexible film, a flexible upper cover plate, a driving control structure and a ground plate; The flexible upper cover plate, the flexible film, the flexible substrate, the ground plate and the drive control structure are stacked in sequence; A microfluidic array structure and a liquid injection port are arranged on the flexible substrate. The microfluidic array structure includes a plurality of unit microfluidic structures. The plurality of unit microfluidic structures are connected. The unit microfluidic structure is a curved cross-shaped structure including a liquid storage tank and four semicircular cross-arm flow channels.

2. According to the liquid metal reconfigurable metasurface reflection unit according to claim 1, the microfluidic array structure is used to provide liquid metal and driving liquid flow channels; the driving control structure is used to control the flow state of liquid metal in multiple unit microfluidic structures; and the ground plate is used to reflect electromagnetic waves.

3. The liquid metal reconfigurable metasurface reflection unit according to claim 1, characterized in that: The liquid reservoir is located in the center of the unit microfluidic channel structure, the four semicircular cross-arm flow channels are arranged around the liquid reservoir, and are interconnected through the liquid reservoir, and the four semicircular cross-arm flow channels all extend in a direction away from the liquid reservoir.

4. The liquid metal reconfigurable metasurface reflection unit according to claim 1, characterized in that: The four semicircular cross-arm flow channels include a first semicircular cross-arm flow channel, a second semicircular cross-arm flow channel, a third semicircular cross-arm flow channel and a fourth semicircular cross-arm flow channel; The first semicircular arc cross arm flow channel and the third semicircular arc cross arm flow channel are centrally symmetrically distributed, and the second semicircular arc cross arm flow channel and the fourth semicircular arc cross arm flow channel are centrally symmetrically distributed.

5. The liquid metal reconfigurable metasurface reflection unit according to claim 4, characterized in that: The included angle between adjacent semicircular arc cross arm flow channels is 90°.

6. The liquid metal reconfigurable metasurface reflection unit according to claim 4, characterized in that: The flexible film is bonded to the flexible substrate by heat pressing, the flexible upper cover is bonded to the flexible film by spraying glue, and an air cavity structure having the same structure as the unit microchannel structure is manufactured in the flexible upper cover; The driving control structure is connected to the liquid injection port on the flexible substrate via an external conduit; The ground plate is glued to the flexible substrate and the driving control structure respectively.

7. The liquid metal reconfigurable metasurface reflection unit according to claim 5, characterized in that: The flexible substrate, the flexible film and the flexible upper cover plate together form a flexible packaging structure. The thickness h1 of the flexible substrate is 3-6 mm, the thickness of the flexible film is 10-50 μm, and the thickness h2 of the flexible upper cover plate is 1.5-3 mm.

8. The liquid metal reconfigurable metasurface reflection unit according to claim 7, characterized in that: The height t2 of the air cavity structure is 0.7-1.2 mm.

9. The liquid metal reconfigurable metasurface reflection unit according to claim 1, characterized in that: The size variation range of the liquid metal in the liquid metal reconfigurable metasurface reflection unit is 30°<J<180°, where J is the arc angle of the liquid metal when it flows in the semicircular cross-arm flow channel.

10. A method for manufacturing a liquid metal reconfigurable metasurface reflection unit, used to prepare the liquid metal reconfigurable metasurface reflection unit according to any one of claims 1 to 9, characterized in that: include: S1: determining the shape and initial size of a unit microfluidic channel structure, wherein the unit microfluidic channel structure is a semicircular cross arm structure; S2: Designing a microfluidic array structure according to the shape, initial size and initial arrangement period of the unit microfluidic structure, and designing the shape and initial size of the flexible substrate and the flexible upper cover according to the microfluidic array structure; S3: Input the shape, initial size and initial arrangement period of the unit microfluidic channel structure, the shape and initial size of the flexible substrate and the flexible upper cover plate, and the initial size of the flexible film into the electromagnetic simulation software to obtain the initial metasurface reflection unit model; S4: Input the material parameters of the flexible substrate, liquid metal and driving liquid, use electromagnetic simulation software to perform multiple parameter sweep iterations on the initial metasurface reflection unit model, obtain the final metasurface reflection unit model, and determine the dimensions of the unit microfluidic structure, flexible substrate, flexible film and flexible upper cover in the final metasurface reflection unit model as the final dimensions; S5: According to the final metasurface reflection unit model, a unit microfluidic structure, a flexible substrate and a flexible upper cover plate that meet the shape and size requirements are manufactured; S6: Fabrication of microfluidic array structures and injection ports on flexible substrates; S7: According to the final metasurface reflection unit model, a flexible film is bonded on a flexible substrate by using a hot pressing method; an air cavity structure having the same shape as the unit microchannel structure is opened in the flexible upper cover plate; S8: injecting a driving liquid through the injection port, and injecting the driving liquid into the flow channel of each unit microfluidic channel structure through the through holes between the unit microfluidic channel structures; Injecting liquid metal through the injection port, and injecting the liquid metal into the flow channel of each unit microfluidic channel structure through the through holes between the unit microfluidic channel structures; S9: The flexible upper cover plate is bonded to the flexible film by spraying glue; a ground plate is arranged under the flexible substrate; a driving control structure is arranged under the ground plate, and the driving control structure is connected to the liquid injection port to obtain a metasurface reflection unit.

Images