High-precision rapid preparation process of metasurface

Abstract

The invention discloses a high-precision rapid preparation process of a metasurface, and belongs to the technical field of microwave communication and flexible medical treatment. The method comprises the following steps: firstly, preparing an electromagnetic loss suspension, then designing a metasurface pattern based on an application purpose and early-stage experimental experience, including drawing a metasurface pattern or a reverse pattern thereof as a pattern of an optical mask, and then manufacturing the optical mask on the surface of a glass plate or a quartz plate by using a laser direct writing or electron beam direct writing technology; the method comprises the following steps: photoetching a pattern on the surface of a microfiltration membrane by utilizing a photoetching technology to obtain a high-precision microfiltration membrane mask as a decompression suction filtration mask, and further photoetching the pattern on the surface of the microfiltration membrane by utilizing the photoetching technology to obtain the high-precision microfiltration membrane mask as the decompression suction filtration mask. And then a sand core filtering device is combined to execute pressure extraction and filtering operation, after the electromagnetic loss suspension liquid is subjected to pressure reduction and suction filtration, a high-precision microfiltration membrane mask plate is obtained, and a deposition pattern on the dried high-precision microfiltration membrane mask plate is transferred to a target base material.

Description

Technical Field

[0001] The present invention belongs to the fields of microwave communications and flexible medical care, and involves technologies such as electromagnetic shielding and compatibility, flexible circuits, and flexible sensing. Specifically, it is a laser-assisted decompression filtration preparation process for patterned conductive metasurfaces with a dimensional accuracy of the order of millimeters, especially a high-precision and rapid preparation process for metasurfaces. Background Art

[0002] As the variety and functionality of electronic products continue to expand, electromagnetic radiation pollution becomes increasingly severe, necessitating the development of highly effective electromagnetic shielding and absorption materials to address this challenge. Long-term exposure to high levels of electromagnetic radiation can lead to a variety of health issues, making the development of high-performance metasurface materials particularly urgent. Furthermore, the rapid development of flexible electronics technology also calls for breakthroughs in the development of high-precision and rapid fabrication processes for conductive surfaces.

[0003] Metasurfaces, as unique superstructures, effectively block the propagation of electromagnetic waves and provide electromagnetic protection by processing materials with electrical and magnetic loss properties into different patterns. Their fabrication techniques encompass a variety of methods, including spin coating, spray coating, and vacuum filtration, but each has its own advantages and disadvantages.

[0004] Currently, screen printing technology is mostly used to prepare patterned metasurfaces. This technology has the advantages of high speed and high precision in large-scale preparation, but its dimensional accuracy control is poor and the cost is high in small-scale preparation, which limits its application in certain fields. On the other hand, the preparation technologies of continuous electromagnetic loss films mainly include spin coating technology, spray coating technology, vacuum filtration technology, etc. These technologies have their own characteristics and are suitable for different application requirements and film materials. Although screen printing technology occupies a certain position in the preparation of patterned metasurfaces, its dimensional accuracy and cost issues still need to be solved, especially in the application and high-precision control in small-scale preparation scenarios. Summary of the Invention

[0005] In response to the problems existing in the existing patterned multi-connected metasurface preparation technology, the present invention provides a high-precision and rapid preparation process for metasurfaces. It is a small-batch rapid preparation process that combines photolithography and vacuum filtration. This process takes a short time from scheme design to product molding and has high precision, making it particularly suitable for sample preparation in the research and development process.

[0006] In order to achieve the above-mentioned purpose of the invention, the technical solution provided by the present invention is as follows:

[0007] A high-precision and rapid preparation process for a metasurface, comprising the following steps:

[0008] S1. Configuring electromagnetic loss suspension, including configuring electric loss materials and magnetic loss materials;

[0009] S2. Design a metasurface pattern based on the application purpose and preliminary experiments. The pattern may include a single-connected pattern, a multi-connected pattern, or a combination of the two. For the designed metasurface pattern, draw the metasurface pattern or the inverse pattern of the metasurface pattern as the pattern of the optical mask according to the type of photoresist in the subsequent steps. For positive resist, the inverse pattern of the metasurface pattern is used, while for negative resist, the metasurface pattern is directly used.

[0010] S3. Based on the metasurface pattern designed in step S2, an optical mask is produced on the surface of a glass plate or a quartz plate using a laser direct writing technique or an electron beam direct writing technique;

[0011] S4. Using photolithography technology to pattern the surface of the microporous filter membrane to obtain a high-precision microporous filter mask as a mask for vacuum filtration;

[0012] S5. Calculate the required thickness of the functional material based on the loss parameters of the designed metasurface, and inversely calculate the required volume of the electromagnetic loss suspension based on the amount of the functional material. Then, prepare the suspension based on the calculated results, add solvent for dilution, and sonicate for 20-40 minutes to fully disperse the suspension.

[0013] S6. Perform the following operations in the sand core filter device:

[0014] First, pour an appropriate amount of deionized water into the filter cup for pressure extraction and filtration to drain the pores between the high-precision microporous filter membrane mask and the sand core filter base, ensuring a smooth decompression filtration path; after the deionized water in the filter cup is filtered, pour the diluted electromagnetic loss suspension into the filter cup to start formal decompression filtration; after the electromagnetic loss suspension is decompressed and filtered, take out the high-precision microporous filter membrane mask, complete the complete deposition of the electromagnetic loss functional material on the high-precision microporous filter membrane mask, and obtain a mask deposited in the shape of the designed pattern; finally, place the high-precision microporous filter membrane mask in a 50-70℃ oven for 7-9 hours to fully dry;

[0015] S7. Transfer the deposited pattern on the dried high-precision microporous filter membrane mask to the target substrate, then spin-coat a sealing layer on the substrate to encapsulate the electromagnetic loss layer, and complete the preparation of the metasurface through a laser lithography-assisted reduced pressure filtration preparation process.

[0016] Furthermore, in the electromagnetic loss suspension prepared in step S1: the electric loss material includes single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, MXene, metal nanowires, etc.; the magnetic loss material includes ferrite, transition metal oxides; and the solvent includes water, alcohols, oils, esters, acetone, and dichloromethane.

[0017] The inverse pattern of the metasurface pattern in step S2 is obtained by exchanging the blank area and the colored area.

[0018] The photolithography steps in step S4 include substrate processing, resist coating, pre-baking, exposure, post-baking, development, fixing, and hardening processes, and the photoresist is fixed on the surface of the microporous filter membrane according to the designed pattern.

[0019] The sand core filter device used in step S6 includes a filter bottle and a sand core filter base. The high-precision microporous filter membrane mask is placed on the sand core filter base, the filter cup is placed on the sand core filter base and fixed, and the sand core filter base is connected to the liquid collecting bottle. The liquid collecting bottle is connected to a vacuum pump to realize the pressure extraction operation in the bottle.

[0020] In the process of vacuum filtration, the microporous filter membranes used include cellulose acetate membrane, cellulose nitrate membrane, mixed cellulose ester membrane, polyamide membrane, polytetrafluoroethylene membrane, polypropylene filter membrane, polyethersulfone filter membrane, and polyvinylidene fluoride filter membrane.

[0021] The transfer substrate described in step S7 includes format films, thin plates and objects with smooth and flat surfaces, including polyimide films, polyethylene terephthalate films, resin-based fiber-reinforced plastic plates, and carbon fiber plates.

[0022] Furthermore, the high-precision and rapid preparation process of the metasurface provided by the present invention can be applied in the fields of aerospace, radar communications, and medical electronics.

[0023] Beneficial effects: The process of the present invention adopts a small-batch rapid preparation process combining photolithography and vacuum filtration, which has significant improvements in dimensional accuracy, preparation time and material cost compared with the preparation process of the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a process flow chart of the process of the present invention;

[0025] Figure 2 It is a schematic diagram of photolithography SU8 on the surface of microporous filter membrane;

[0026] Figure 3 It is a schematic diagram of the vacuum filtration process;

[0027] Figure 4 It is a high-precision microporous filter membrane mask after vacuum filtration;

[0028] Figure 5 This is a schematic diagram of the pattern boundary after reduced pressure filtration;

[0029] Figure 6 This is a comparison chart of the pattern size accuracy obtained by the present invention and other filtration processes;

[0030] Figure 7 This is a microscopic image of the conductive surface after filtration;

[0031] Figure 8 The conductive column graph is prepared by the process of the present invention. DETAILED DESCRIPTION

[0032] To illustrate the technical solution disclosed in the present invention in detail, a further introduction is given below in conjunction with the accompanying drawings.

[0033] Combine Figure 1 As described above, first prepare an aqueous multi-walled carbon nanotube suspension with a concentration of 0.5 mg / ml. Then design the pattern of the electromagnetic metasurface, and prepare a photomask based on the designed metasurface pattern. Select a nylon microporous filter membrane, and then spin-coat SU8-2050 on the microporous filter membrane through a photolithography process and form a pattern to obtain a high-precision microporous filter membrane mask, such as Figure 2 As shown. Select a large-diameter filter bottle, place the high-precision microporous filter mask on the sand core filter base, place the filter cup on the sand core filter base and fix it with a clamp, connect the sand core filter base to the liquid collection bottle, connect the liquid collection bottle to the vacuum pump, and build the device. Dilute the aqueous multi-walled carbon nanotube suspension to 0.5 mg / L and ultrasonicate for 30 minutes to fully disperse the suspension. Turn on the vacuum pump, first pour an appropriate amount of deionized water into the filter cup for filtration to drain the pores between the high-precision microporous filter mask and the sand core filter base, and ensure that the vacuum filtration path is smooth. After the deionized water in the filter cup is filtered, pour the diluted electromagnetic loss suspension into the filter cup to start formal vacuum filtration, as shown in the schematic diagram. Figure 3 After the electromagnetic loss suspension is decompressed and filtered, the high-precision microporous filter mask is taken out. At this time, the electromagnetic loss functional material has been completely deposited on the high-precision microporous filter mask in the shape of the designed pattern. Figure 4 As shown in the figure, the high-precision microporous filter membrane mask was placed in a 60°C oven for 4 hours to fully dry. A sealing layer was then spin-coated on the dried membrane to encapsulate the electromagnetic loss layer. This completes the fabrication of the metasurface using the laser lithography-assisted vacuum filtration process.

[0034] Tested by optical microscope (such as Figure 5 and Figure 6 As shown in Figure 2), laser printing can control the size accuracy of the metasurface pattern to about 20μm, which has a high dimensional accuracy. Figure 7 As shown, after filtration, the functional material is evenly distributed on the substrate. The surface resistance is measured to be related to the surface density of the functional material on the substrate surface. The relationship is as follows: Figure 8 shown.

Claims

1. A high-precision and rapid preparation process for a supersurface, characterized in that the steps include: S1. Configuring electromagnetic loss suspension, including configuring electric loss materials and magnetic loss materials; S2. Design a metasurface pattern based on the application purpose and preliminary experiments. The pattern may include a single-connected pattern, a multi-connected pattern, or a combination of the two. For the designed metasurface pattern, draw the metasurface pattern or the inverse pattern of the metasurface pattern as the pattern of the optical mask according to the type of photoresist in the subsequent steps. For positive resist, the inverse pattern of the metasurface pattern is used, while for negative resist, the metasurface pattern is directly used. S3. Based on the metasurface pattern designed in step S2, an optical mask is produced on the surface of a glass plate or a quartz plate using a laser direct writing technique or an electron beam direct writing technique; S4, using photolithography technology to photoetch patterns on the surface of the microporous filter membrane to obtain a microporous filter membrane mask as a mask for vacuum filtration; S5. Calculate the required thickness of the functional material based on the loss parameters of the designed metasurface, and inversely calculate the required volume of the electromagnetic loss suspension based on the amount of the functional material. Then, prepare the suspension based on the calculated results, add solvent for dilution, and sonicate for 20-40 minutes to fully disperse the suspension. S6. Perform the following operations in the sand core filter device: First, pour an appropriate amount of deionized water into the filter cup for pressure extraction and filtration to drain the pores between the microporous filter membrane mask and the sand core filter base, ensuring a smooth decompression filtration path; after the deionized water in the filter cup is filtered, pour the diluted electromagnetic loss suspension into the filter cup to start formal decompression filtration; after the electromagnetic loss suspension is decompressed and filtered, take out the high-precision microporous filter membrane mask, complete the complete deposition of the electromagnetic loss functional material on the high-precision microporous filter membrane mask, and obtain a mask deposited in the shape of the designed pattern; finally, place the high-precision microporous filter membrane mask in a 50-70℃ oven for 7-9 hours to fully dry; S7. Transfer the deposited pattern on the dried microporous filter membrane mask to the target substrate, then spin-coat a sealing layer on the transfer substrate to encapsulate the electromagnetic loss layer, and complete the preparation of the metasurface through a laser lithography-assisted reduced pressure filtration preparation process.

2. The high-precision and rapid preparation process for a supersurface according to claim 1, characterized in that: The sand core filter device used in step S6 includes a filter bottle and a sand core filter base. The microporous filter membrane mask is placed on the sand core filter base, the filter cup is placed on the sand core filter base and fixed, and the sand core filter base is connected to the liquid collecting bottle. The liquid collecting bottle is connected to a vacuum pump to realize the pressure extraction operation in the bottle.

3. The high-precision and rapid preparation process for a supersurface according to claim 1, characterized in that: In the electromagnetic loss suspension prepared in step S1, the electric loss material includes single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, MXene, and metal nanowires; the magnetic loss material includes ferrite and transition metal oxides; and the solvent includes water, alcohols, oils, esters, acetone, and dichloromethane.

4. The high-precision and rapid preparation process for a supersurface according to claim 1, characterized in that: The inverse pattern of the metasurface pattern in step S2 is obtained by exchanging the blank area and the colored area.

5. The high-precision and rapid preparation process for a supersurface according to claim 1, characterized in that: The photolithography steps in step S4 include substrate processing, resist coating, pre-baking, exposure, post-baking, development, fixing, and hardening, thereby fixing the photoresist on the surface of the microporous filter membrane according to the designed pattern.

6. The high-precision and rapid preparation process for a supersurface according to claim 1, characterized in that: In the process of vacuum filtration, the microporous filter membranes used include cellulose acetate membrane, cellulose nitrate membrane, mixed cellulose ester membrane, polyamide membrane, polytetrafluoroethylene membrane, polypropylene filter membrane, polyethersulfone filter membrane, and polyvinylidene fluoride filter membrane.

7. The high-precision and rapid preparation process for a supersurface according to claim 1, characterized in that: The transfer substrate described in step S7 includes format films, thin plates and objects with smooth and flat surfaces, including polyimide films, polyethylene terephthalate films, resin-based fiber-reinforced plastic plates, and carbon fiber plates.

8. The high-precision and rapid preparation process for a supersurface according to any one of claims 1 to 7, characterized in that: The metasurface has applications in aerospace, radar communications, and medical electronics.

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