Topological metasurface structure unit, preparation method thereof and reconfigurable topological metasurface

Abstract

The application provides a topological super surface structure unit and a preparation method thereof, and a reconfigurable topological super surface, and belongs to the technical field of topological photonics and artificial super materials. The topological super surface structure unit comprises an upper encapsulation layer and a lower encapsulation layer, a first microchannel layer and a second microchannel layer encapsulated between the upper encapsulation layer and the lower encapsulation layer, and a spacing layer arranged between the first microchannel layer and the second microchannel layer; a microchannel for flowing of liquid metal is arranged on the first microchannel layer and the second microchannel layer respectively, and a through hole flow guide hole is arranged on the spacing plate and used for realizing the liquid metal flow between the first microchannel layer and the second microchannel layer; and the liquid metal forms a metal microstructure by flowing in the microchannel. The application assembles the independent topological super surface structure units into a complete topological super surface which can realize multiple working states, and realizes the reconfiguration of the topological super surface by changing the structure, position and arrangement mode of the topological super surface structure units.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of topological photonics and artificial super-structured materials, and relates to a topological super-surface structure unit and a preparation method thereof, and a reconfigurable topological super-surface. BACKGROUND

[0002] The Maxwell equations describing the motion law of electromagnetic wave field are intrinsically the quantum spin Hall effect of light, and the evanescent wave existing at the interface shows strong spin-momentum correlation. Experiments have confirmed that the symmetry-protected topological state similar to the quantum spin Hall effect can be realized by coupling the super-surface mode with complementary electromagnetic response. The superposition unit arrangement of the super-surface can directly generate degenerate transverse electric (TE) and transverse magnetic (TM) mode double Dirac cones, and enter a wide non-trivial band gap when the layers are separated. Therefore, the ultra-thin structure supports a robust gapless edge state, which is guided by the one-dimensional interface line of the double super-surface, rather than the surface interface.

[0003] The super-surface can be regarded as the two-dimensional counterpart of artificial super-materials, which can not only arbitrarily set electromagnetic parameters, but also introduce complex spin-orbit coupling mechanisms, thus having special physical properties that natural materials do not have. Although the electromagnetic devices based on super-surface have excellent performance, their functions and electromagnetic parameters are fixed after design and processing, and cannot be adjusted at any time, which cannot meet the reconfigurable demand. SUMMARY

[0004] Therefore, the purpose of the present application is to solve the technical problem that the existing electromagnetic devices based on super-surface cannot be adjusted after design and processing, and to provide a topological super-surface structure unit and a preparation method thereof, and a reconfigurable topological super-surface to solve the above problems.

[0005] To achieve the above-mentioned purpose, the present application provides a topological super-surface structure unit, which comprises an upper encapsulation layer and a lower encapsulation layer with the same shape and material, and a first micro-channel layer and a second micro-channel layer encapsulated between the upper encapsulation layer and the lower encapsulation layer, wherein a spacing layer is arranged between the first micro-channel layer and the second micro-channel layer.

[0006] Micro-channels for flowing liquid metal are arranged on the first micro-channel layer and the second micro-channel layer, respectively, and a through-hole flow guide hole is arranged on the spacing plate to realize the flow of liquid metal between the first micro-channel layer and the second micro-channel layer. The liquid metal forms a metal microstructure by flowing in the micro-channel.

[0007] The shape and size of the upper encapsulation layer, the first micro-channel layer, the spacing layer, the second micro-channel layer and the lower encapsulation layer are matched.

[0008] Preferably, the topological metasurface structure unit presents a regular hexagonal prism morphology; the microchannels of the first microchannel layer and the second microchannel layer are both regular hexagonal ring structures, forming a double-ring type unit.

[0009] Alternatively, the microchannels of the first microchannel layer and the second microchannel layer are both hexagonal block structures, forming a double-piece type unit.

[0010] Alternatively, one of the microchannels of the first microchannel layer and the second microchannel layer is a regular hexagonal ring structure, and the other is a hexagonal block structure, forming a piece-ring hybrid type unit.

[0011] Preferably, at least one through-hole injection hole is provided on the upper packaging layer for injecting liquid metal; and one through-hole overflow hole is provided on the lower packaging layer for discharging excess liquid metal.

[0012] Preferably, the materials of the upper packaging layer, the first microchannel layer, the spacing layer, the second microchannel layer, and the lower packaging layer are independently selected from any one of PMMA, PVC, PDMS, and polyimide.

[0013] Preferably, the liquid metal is a liquid gallium-indium-tin alloy.

[0014] The application also provides a preparation method of the topological metasurface structure unit.

[0015] S1: cutting the substrates selected for each layer, and applying adhesive pretreatment on the surfaces in contact with each other between the layers;

[0016] S2: according to the outer shape and size of the structure unit, using a carbon dioxide laser engraving machine to process the outer shape profile of each layer and the microchannels of the first microchannel layer and the second microchannel layer;

[0017] S3: completing the bonding and assembly of each layer;

[0018] S4: placing in a vacuum oven for drying treatment to achieve vacuumization and drying of the microchannels;

[0019] S5: injecting dimethyl silicone oil into the microchannels through the injection hole for inner wall surface pretreatment;

[0020] S6: injecting liquid metal into the microchannels by using external force driving through the injection hole, and the dimethyl silicone oil is gradually discharged through the overflow hole at the same time as the liquid metal is injected, and the excess liquid metal is also discharged through the overflow hole;

[0021] S7: sealing the injection hole and the overflow hole to complete the packaging.

[0022] Preferably, the adhesive pretreatment in step S1 uses pressure-sensitive adhesive.

[0023] Preferably, in the step S6, the liquid metal is injected into the microchannel through the injection hole by external force driving.

[0024] The sodium hydroxide solution and the liquid metal are alternately segmented in the pipeline in an oxygen-free state to remove the oxide on the surface of the liquid metal, and a seal is formed at both ends of the liquid metal to effectively prevent further oxidation.

[0025] The pipeline is fixed at the injection hole, and the liquid metal in the pipeline is continuously injected by external force driving.

[0026] The present application also provides a reconfigurable topological metasurface, which is densely packed with the topological metasurface structure units as described above throughout the working area, wherein the hexagonal ring-shaped microchannels of a part of the topological metasurface structure units are upward, and the hexagonal block-shaped microchannels of another part of the topological metasurface structure units are upward, and the reconfiguration of the topological metasurface is achieved by at least one of moving, flipping and replacing the individual topological metasurface structure units.

[0027] Preferably, the entire working area is densely packed with the piece-ring hybrid topological metasurface structure units, and the reconfiguration is achieved by flipping operation.

[0028] Or the entire working area is densely packed with the double-piece and double-ring topological metasurface units, and the reconfiguration is achieved by moving and / or replacing operation.

[0029] The present application has the advantages of the above technical solutions:

[0030] (1) The topological metasurface structure unit of the present application determines the shape and arrangement of the liquid metal microstructure through the structure of the microchannel. According to the principle of topological metasurface, the complementary hexagonal block-shaped and ring-shaped metal metasurfaces have complementary capacitance and inductance response, so they respectively support low-order TE and TM propagation surface modes.

[0031] (2) The existing topological metasurface has fixed structure and function after design and processing, and cannot adapt to different working needs, i.e. cannot realize reconfiguration. The present application uses the fluidity of liquid metal to inject liquid metal into the topological metasurface structure unit with microchannels, and then uses the independence of each topological metasurface structure unit to assemble a complete topological metasurface that can realize multiple working states. The reconfiguration of the structure and function of the topological metasurface can be realized by changing the structure, position and arrangement of the topological metasurface structure units. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments or prior art description. Obviously, the drawings described below are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0033] Figure 1 Structure diagram of a sheet-ring hybrid topological metasurface structure unit of the present application;

[0034] Figure 2 Structure diagram of a double-sheet topological metasurface structure unit of the present application;

[0035] Figure 3 Structure diagram of a double-ring topological metasurface structure unit of the present application;

[0036] Figure 4 Structure diagram of a regular hexagonal ring microchannel structure in a topological metasurface structure unit of the present application;

[0037] Figure 5 Structure diagram of a hexagonal block microchannel structure in a topological metasurface structure unit of the present application;

[0038] Figure 6 Different working state diagrams of a topological metasurface of the present application, in which sheet-ring hybrid topological metasurface structure units are densely laid in the entire working area;

[0039] Figure 7 Different working state diagrams of a topological metasurface of the present application, in which double-sheet and double-ring topological metasurface structure units are complementarily densely laid in the entire working area;

[0040] Figure 8 Preparation method flow diagram of a topological metasurface structure unit of the present application;

[0041] Explanation of reference numerals: 1 - upper packaging layer; 2 - liquid injection hole; 3 - microchannel layer; 31 - first microchannel layer; 32 - second microchannel layer; 4 - spacing layer; 5 - overflow hole; 6 - regular hexagonal ring cavity; 7 - flow guide hole; 8 - regular hexagonal block cavity; 9 - lower packaging layer. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0043] like Figures 1-5 As shown, the present invention provides a topological metasurface structure unit, including an upper encapsulation layer 1 and a lower encapsulation layer 9 with the same shape and material, and a first microchannel layer 31 and a second microchannel layer 32 encapsulated between the upper encapsulation layer 1 and the lower encapsulation layer 9, wherein a spacer layer 4 is provided between the first microchannel layer 31 and the second microchannel layer 32.

[0044] Microchannels for liquid metal flow are provided on the first microchannel layer 31 and the second microchannel layer 32 respectively. A through-hole 7 is provided on the spacer plate 4 to realize the flow of liquid metal between the first microchannel layer 31 and the second microchannel layer 32. The liquid metal forms a metal microstructure by flowing in the microchannel.

[0045] The dimensions of the upper encapsulation layer 1, the first microchannel layer 31, the spacer layer 4, the second microchannel layer 32, and the lower encapsulation layer 9 are matched.

[0046] The topological metasurface structure unit exhibits a regular hexagonal prism shape; the microchannels of the first microchannel layer 31 and the second microchannel layer 32 are both regular hexagonal ring (regular hexagonal ring cavity 6) structures, as shown below. Figure 4 As shown, a double-ring unit is formed as follows: Figure 3 As shown; or, the microchannels of the first microchannel layer 31 and the second microchannel layer 32 are both hexagonal block (regular hexagonal block cavity 8) structures, as shown. Figure 5 As shown, a dual-plate unit is formed as follows: Figure 2 As shown; or, in the microchannels of the first microchannel layer 31 and the second microchannel layer 32, one is a regular hexagonal ring structure and the other is a hexagonal block structure, forming a sheet-ring hybrid unit as shown. Figure 1 As shown. The structure of the microchannels determines the shape and arrangement of the liquid metal microstructures. According to the principle of topological metasurfaces, complementary hexagonal block and toroidal metal metasurfaces have complementary capacitive and inductive responses, thus supporting low-order TE and TM propagation surface modes, respectively.

[0047] Preferably, at least one through-hole injection hole 2 is arranged on the upper encapsulation layer 1 for injecting liquid metal, and one through-hole overflow hole 5 is arranged on the lower encapsulation layer 9 for discharging excess liquid metal. For example, when the topological metasurface structure unit is a double-ring unit, two through-hole injection holes 2 are arranged on the upper encapsulation layer 1, one through-hole overflow hole 5 is arranged on the lower encapsulation layer 9, and one through-hole flow guide hole 7 is arranged on the spacing layer 4, and there are a total of four through-holes. When the topological metasurface structure unit is a double-piece unit, one through-hole injection hole 2 is arranged on the upper encapsulation layer 1, one through-hole overflow hole 5 is arranged on the lower encapsulation layer 9, and one through-hole flow guide hole 7 is arranged on the spacing layer 4, and there are a total of three through-holes. When the topological metasurface structure unit is a mixed piece-ring unit, two through-hole injection holes 2 are arranged on the upper encapsulation layer 1, one through-hole overflow hole 5 is arranged on the lower encapsulation layer 9, and one through-hole flow guide hole 7 is arranged on the spacing layer 4, and there are a total of four through-holes.

[0048] The material of the outer encapsulation layer is selected to ensure the sealing property, thickness and mechanical strength. The micro-channel layer is sealed by the outer encapsulation layer, so that the liquid metal is in a closed and air-isolated working environment after injection, thereby avoiding oxidation of the liquid metal and affecting the working effect. Preferably, the materials of the upper encapsulation layer 1 and the lower encapsulation layer 9 are PVC or PDMS film materials.

[0049] The spacing layer 4 provides a spacing between the first micro-channel layer 31 and the second micro-channel layer 32, so that one independent topological metasurface structure unit can have different liquid metal microstructures. Preferably, the materials of the upper encapsulation layer 1, the first micro-channel layer 31, the spacing layer 4, the second micro-channel layer 32 and the lower encapsulation layer 9 are independently selected from any one of PMMA, PVC, PDMS and polyimide.

[0050] The metal microstructure in the application is not limited to the use of liquid metal, and other suitable metal materials can also be applicable. Preferably, the liquid metal is a liquid gallium-indium-tin alloy, which has low melting point, good fluidity and is easy to inject into the micro-channel to form a microstructure; the gallium-indium-tin alloy has high electrical conductivity, which is slightly lower than copper but much higher than other conductive liquids; the gallium-indium-tin alloy is not easy to volatilize and has no biological toxicity, thereby ensuring the safety of the operator.

[0051] As shown in Figure 8 The application further provides a preparation method of the topological metasurface structure unit, which comprises the following steps:

[0052] S1: cutting the selected substrates of each layer, and applying glue to the surfaces in contact with each other between the layers for pretreatment;

[0053] S2: according to the size of the structure unit, using a carbon dioxide laser engraving machine to process the outer shape of each layer and the micro-channels of the first micro-channel layer and the second micro-channel layer;

[0054] S3: complete the bonding and assembly of each layer;

[0055] S4: placed in a vacuum oven for drying treatment to achieve the vacuum and drying of the micro-channel;

[0056] S5: by the injection hole into the micro-channel injection of dimethyl silicone oil for inner wall surface pretreatment;

[0057] S6: by the injection hole using external force driven liquid metal injection into the micro-channel, dimethyl silicone oil at the same time by the overflow hole gradually be discharged, the excess liquid metal also through the overflow hole discharge;

[0058] S7: the injection hole and overflow hole sealing treatment complete packaging.

[0059] In the step S1 of the adhesive pretreatment, the pressure sensitive adhesive is used, which can effectively avoid the contamination of the substrate by high temperature melting splashes in the processing process, ensure the surface quality of the processed surface, and the pressure sensitive adhesive can absorb the excess heat of the laser beam to ensure the flatness of the processed microstructure incision and improve the overall processing quality.

[0060] The step S2 uses a carbon dioxide laser engraving machine for processing, which can reduce the pollution and waste liquid generated by conventional microstructure forming methods, can fully meet the single piece processing and batch production demand, is more flexible and environmentally friendly; the processing power and processing rate of the laser can be adjusted to achieve the best match to prevent the substrate from warping, curling and other adverse effects during processing, to maximize the processing precision.

[0061] The step S3 uses a multi-layer structure of layer-by-layer pressure bonding assembly method, which can effectively simplify the design layout, avoid the use of traditional mechanical connectors and fasteners, reduce the design complexity of the structure unit, and improve the assembly efficiency.

[0062] In the step S5, dimethyl silicone oil is injected into the microfluidic channel for surface pretreatment, and when the injected dimethyl silicone oil is pushed out, a uniform oil film envelope layer can be formed on the inner wall of the microchannel, further isolating oxygen and effectively reducing the flow resistance when the liquid metal is injected.

[0063] In the step S6, the liquid metal is injected into the micro-channel through the injection hole using external force, and the liquid metal can be injected from one or more injection holes under the action of external force, and overflowed from the overflow hole at the other end, to completely fill the micro-channel and form a liquid metal microstructure. Specifically:

[0064] The sodium hydroxide solution in the pipeline is formed in an anaerobic state and alternately segmented liquid with the liquid metal to remove the oxide on the surface of the liquid metal, and a seal is formed at both ends of the liquid metal to effectively prevent further oxidation;

[0065] The pipeline is fixed at the liquid injection hole, and the liquid metal in the pipeline is continuously injected by external force driving.

[0066] Wherein, the external force driving is mechanical force driving or voltage driving, the flow rate and flow of the liquid metal can be accurately controlled, the preparation efficiency of the topological metasurface structure unit is improved, and the utilization rate of the liquid metal is ensured. The mechanical force driving is to apply air pressure or liquid pressure to the liquid metal by using a high-precision injection pump to inject the liquid metal into the microfluidic channel. The voltage driving is to form a pair of driving electrodes on the liquid metal microchannel to form an electric field, change the surface tension of the liquid metal, and drive the liquid metal to form directional motion in the microchannel until it is filled.

[0067] The application also provides a reconfigurable topological metasurface, which is densely packed with the topological metasurface structure units as described above in the entire working area, wherein the hexagonal ring-shaped microchannels of a part of the topological metasurface structure units are upward, and the hexagonal block-shaped microchannels of another part of the topological metasurface structure units are upward, and the reconfiguration of the topological metasurface is realized by at least one of the independent moving, flipping and replacing of each topological metasurface structure unit.

[0068] In some embodiments, the entire working area of the reconfigurable topological metasurface is densely packed with the ring-mixed topological metasurface structure units, as shown in Figure 6 As shown, the working area is selected as a rectangular area, wherein the part of the hexagonal ring-shaped microchannels upward is on the left, the part of the hexagonal block-shaped microchannels upward is on the right, and the one-dimensional waveguide extends from the midpoint of the top of the working area to the lower left corner of the working area at a certain angle after a certain distance downward, and the one-dimensional waveguide extends from Figure 6 The working state transition from the left side to the right side can be realized by changing the part of the triangular area at the lower part of the working area, and the specific operation is to flip the part of the ring-mixed topological metasurface structure units in the triangular area, which can realize the transition of the part of the structure units from the hexagonal block-shaped microchannels upward to the hexagonal ring-shaped microchannels upward, so as to achieve Figure 6 the working state shown in the right side, Figure 6 In the working state shown in the right side, the one-dimensional waveguide extends from the midpoint of the top of the working area to the lower right corner of the working area at a certain angle after a certain distance downward, so as to change the transmission direction of the wave by flipping part of the topological metasurface structure units, thereby achieving the purpose of reconfiguration.

[0069] In some embodiments, the reconfigurable topological metasurface is densely packed with the double-piece and double-ring topological metasurface structure units in the entire working area, as shown in Figure 7As shown, the work area is selected as a rectangular region, Figure 7 In the left working state, the one-dimensional waveguide extends horizontally to the left boundary of the working area after starting from the midpoint of the top of the working area and extending downward for a certain distance. Figure 7 As shown on the right, the one-dimensional waveguide extends horizontally to the right boundary of the working area after starting from the midpoint of the top of the working area and extending downward for a certain distance, and the topological metasurface working state is Figure 7 The conversion between the left and right sides can be realized by replacing part of the topological metasurface structure unit in the working area to achieve the purpose of reconfiguration.

[0070] The advantages of the technical scheme of the present application are:

[0071] (1) The topological metasurface structure unit of the present application determines the shape and arrangement of the liquid metal microstructure by the structure of the microchannel. According to the principle of topological metasurface, complementary hexagonal block and ring-shaped metal metasurface have complementary capacitance and inductance response, so they support low-order TE and TM propagation surface modes respectively.

[0072] (2) The existing topological metasurface has fixed structure and function after design and processing, and cannot adapt to different working needs, i.e. cannot realize reconfiguration. The present application uses the fluidity of liquid metal to inject liquid metal into the topological metasurface structure unit with microchannels, and then uses the independence of each topological metasurface structure unit to assemble a complete topological metasurface that can realize multiple working states. The reconfiguration of the structure and function of the topological metasurface can be realized by changing the structure, position and arrangement of the topological metasurface structure unit.

[0073] The above is only a preferred embodiment of the present application and is not intended to limit the present application. Any modification, equivalent replacement and improvement within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A topological metasurface structural unit, characterized in that, It includes an upper encapsulation layer and a lower encapsulation layer that are identical in shape and material, and a first microchannel layer and a second microchannel layer encapsulated between the upper encapsulation layer and the lower encapsulation layer, wherein a spacer layer is provided between the first microchannel layer and the second microchannel layer; Microchannels for liquid metal flow are provided on the first microchannel layer and the second microchannel layer respectively. A through-hole is provided on the spacer layer to enable liquid metal flow between the first microchannel layer and the second microchannel layer. The liquid metal forms a metal microstructure by flowing in the microchannel. The upper encapsulation layer, the first microchannel layer, the spacer layer, the second microchannel layer, and the lower encapsulation layer are matched in size; The topological metasurface structure unit presents a regular hexagonal prism shape; the microchannels of the first microchannel layer and the second microchannel layer are both regular hexagonal ring structures, forming a double-ring unit; Alternatively, the microchannels in both the first and second microchannel layers are hexagonal block structures, forming a double-layer unit; Alternatively, in the microchannels of the first microchannel layer and the second microchannel layer, one is a regular hexagonal ring structure and the other is a hexagonal block structure, forming a sheet-ring hybrid unit; The materials of the upper encapsulation layer, the first microchannel layer, the spacer layer, the second microchannel layer, and the lower encapsulation layer are all independently selected from PMMA, PVC, PDMS, and polyimide.

2. The topological metasurface structure unit according to claim 1, characterized in that, The upper encapsulation layer has at least one through-hole for injecting liquid metal; the lower encapsulation layer has one through-hole for draining excess liquid metal.

3. The topological metasurface structure unit according to claim 1, characterized in that, The liquid metal is a liquid gallium indium tin alloy.

4. The method for preparing the topological metasurface structural unit as described in claim 3, characterized in that, Includes the following steps: S1: Cut the substrates selected for each layer and pre-treat the surfaces that come into contact with each other between the layers with adhesive. S2: Based on the external dimensions of the structural unit, a carbon dioxide laser engraving machine is used to process the external contours of each layer and the microchannels of the first microchannel layer and the second microchannel layer. S3: Complete the bonding and assembly of each layer; S4: Place in a vacuum oven for drying to achieve vacuuming and drying of the microchannels; S5: Inject dimethyl silicone oil into the microchannel through the injection hole to pre-treat the inner wall surface; S6: Liquid metal is injected into the microchannel through the injection hole using external force. Dimethyl silicone oil is gradually discharged through the overflow hole while the liquid metal is being injected. Excess liquid metal is also discharged through the overflow hole. S7: Seal the injection hole and overflow hole to complete the encapsulation.

5. The preparation method according to claim 4, characterized in that, The adhesive pretreatment in step S1 uses pressure-sensitive adhesive.

6. The preparation method according to claim 4, characterized in that, In step S6, injecting liquid metal into the microchannel using external force through the injection hole specifically involves: In an anaerobic environment, sodium hydroxide solution and liquid metal are alternately separated in the pipeline to remove oxides from the surface of the liquid metal, and a seal is formed at both ends of the liquid metal to effectively prevent further oxidation. The pipeline is fixed at the injection hole, and the liquid metal in the pipeline is continuously injected using external force.

7. A reconfigurable topological metasurface, characterized in that, The entire working area is densely covered with the topological metasurface structural units as described in claim 2, wherein a portion of the topological metasurface structural units have hexagonal annular microchannels facing upwards, while another portion of the topological metasurface structural units have hexagonal block microchannels facing upwards. The reconstruction of the topological metasurface is achieved by at least one of the following operations: independent movement, flipping, and replacement of each topological metasurface structural unit.

8. The reconfigurable topological metasurface according to claim 7, characterized in that, Its entire working area is densely covered with sheet-ring hybrid topological metasurface structural units, and reconstruction is achieved through a flipping operation; Alternatively, the entire working area can be densely covered by complementary biplane and biring metasurface structural units, and reconstruction can be achieved through movement and / or replacement operations.

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