Preparation method and application of organic hydrogel all-dielectric stretchable microwave absorber based on island bridge structure

Abstract

The invention provides a preparation method and application of an island bridge structure-based organic hydrogel all-dielectric stretchable microwave absorber, and is suitable for the field of microwave absorption and stretchable electronic equipment. The absorber is an all-dielectric island-bridge structure organic hydrogel metamaterial, and a loss dielectric layer is polyacrylamide organic hydrogel and has a periodic island-bridge structure. The invention has the greatest advantages that broadband absorption is realized through standing wave and field concentration effect of the island bridge structure, the stability of the absorber structure is ensured by inducing strain dissipation in a tensile state, the position and strength of an absorption peak are adjusted by using a tensile ratio in different polarization states (TE and TM polarization), and the absorption efficiency is improved. And stable broadband absorption performance under the bandwidth of about 12 GHz is realized. Therefore, the material has great potential in the field of flexible electronic equipment. In addition, the material is simple in preparation process and low in cost, so that large-scale production and application are facilitated.

Description

Technical Field

[0001] The present invention belongs to the field of microwave absorbing materials and their application in stretchable electronic devices. More specifically, it relates to a preparation method and application of an organic hydrogel all-dielectric stretchable microwave absorber based on an island-bridge structure. Background Art

[0002] With the rapid development of flexible electronic devices, wearable devices and stealth technology in the military field, the demand for stretchable microwave absorbing materials is increasing. However, existing microwave absorbers are usually realized by printing a conductive layer on a flexible substrate. However, due to the inconsistency of the mechanical properties of the conductive layer and the dielectric layer, the conductive layer of the traditional absorber is prone to cracking or falling off during repeated stretching, resulting in a decrease in absorption performance. In recent years, improving the tensile properties of microwave absorbers through new materials and structural design has gradually become a research hotspot. For example, organic hydrogel materials have good tensile properties, adhesion and environmental stability, etc., and can be used as a new type of microwave absorbing material. In addition, the design of the island-bridge structure can not only improve the absorption performance and stability of the absorber through field concentration effect and standing wave effect, but also can evenly disperse stress during the stretching process of the absorber, effectively improve the absorption performance and stability of the absorber, and achieve stable broadband absorption of 12GHz under 30% tension. Therefore, there is an urgent need for an innovative microwave absorber combining an island-bridge structure and an organic hydrogel material, which can achieve both efficient broadband absorption and tensile stability. Summary of the invention

[0003] The purpose of the present invention is to provide a preparation method and application of an organic hydrogel all-dielectric stretchable microwave absorber based on an island-bridge structure, so as to solve the stability problem caused by the incompatibility of the conductive layer and the dielectric layer in the prior art. The present invention combines the island-bridge structure with the organic hydrogel material to achieve broadband absorption and high stretching stability while ensuring low cost, so that the microwave absorber can maintain a stable microwave absorption performance of -10dB in the 5-18GHz frequency band.

[0004] To achieve the above purpose, the present invention adopts the following technical means:

[0005] The first aspect of the present invention provides an organohydrogel all-dielectric stretchable microwave absorber based on an island-bridge structure. Figure 1 a, The all-medium island-bridge structure organic hydrogel-based metamaterial is composed of an organic hydrogel-based diamond hollow grid (structure-1) with a diagonal length of b, a wall width of w and a thickness of h, which is moved a / 2 along its diagonal direction (structure-2) and filled with a unit structure formed by the hollow area formed by the intersection of the top angles. The unit structure is distributed in a periodic array plane, and the bottom is a metal plate layer, see Figure 1 b.

[0006] Preferably, the diagonal length b of the organic hydrogel-based diamond hollow grid is preferably 28 to 36 mm, the wall width w is 3.0 to 5.0 mm, and the length a of the unit structure is 36 to 44 mm.

[0007] Preferably, the thickness h of the all-dielectric island-bridge structure organic hydrogel-based metamaterial is 5.2-6.8 mm, and the thickness of the metal plate layer is 0.2-0.5 mm.

[0008] The second aspect of the present invention provides a method for preparing an organic hydrogel all-dielectric stretchable microwave absorber based on an island-bridge structure, comprising the following steps: step one: printing a reverse mold of an island-bridge structure by 3D printing technology; step two: preparing an organic hydrogel in the mold obtained in step one; and step three: demolding.

[0009] Preferably, the reverse mold of the island bridge structure is printed by a fused deposition modeling 3D printer. The 3D printing material includes polylactic acid plastic, ABS plastic and polycarbonate plastic. The 3D printing conditions are: printing temperature of 150-250°C, printing accuracy of 0.05-0.25mm, minimum layer thickness of the nozzle of 0.02-0.08mm, printing speed of 1-8mm / s, and filling rate of 100%.

[0010] The preparation method of the organic hydrogel is as follows: monomer acrylamide, crosslinking agent N,N'-methylenebisacrylamide and initiator ammonium persulfate are fully dissolved in a binary solvent of deionized water and glycerol, and then a catalyst N,N,N',N'-tetramethylethylenediamine is used to promote crosslinking at room temperature.

[0011] Preferably, the mass of the monomer accounts for 25% of the total proportion, and the mass of glycerol accounts for 33.3% to 80% of the proportion of the binary solvent of deionized water and glycerol.

[0012] Preferably, the monomer acrylamide (AM, 99.0%) and the thermal initiator ammonium persulfate (APS, 98%) are purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. (China); the crosslinking agent N,N′-methylenebisacrylamide (MBA, 99.0%) and the catalyst N,N,N′,N′-tetramethylethylenediamine (TEMED, 99.5%) are purchased from Shanghai McLean Biochemical Technology Co., Ltd.; the solvent glycerol (Glycerin, 99.5%) is purchased from Sinopharm Group.

[0013] In addition, the present invention also provides the application of the island-bridge structure-based organic hydrogel all-dielectric stretchable microwave absorber in the field of electromagnetic wave absorption.

[0014] Compared with the existing common microwave absorbing materials, the present invention has the following beneficial effects: the organic hydrogel all-dielectric stretchable microwave absorber based on the island-bridge structure of the present invention is achieved by combining the organic hydrogel with the island-bridge structure, using the standing wave and field concentration effect of the sub-wavelength structure to achieve broadband absorption, achieving a reflection loss of less than -10dB in the frequency range of 5-18GHz, and tuning the absorption peak position and intensity by changing the stretching ratio, and using the strain dissipation effect of the island-bridge structure to maintain the stability of the island structure, achieving effective microwave absorption in a wide frequency range of about 12GHz at a stretching ratio of 30%. In addition, the material preparation process of the scheme of the present invention is very simple and low-cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 :The design idea and periodic array structure schematic diagram of the all-medium island-bridge structure organic hydrogel-based metamaterial of the present invention

[0016] Figure 2 : Frequency-reflection loss curves of the island-bridge structured organohydrogel all-dielectric stretchable microwave absorber prepared in Example 1 under unstretched and 30% stretching ratios.

[0017] Figure 3 : Frequency-reflection loss curves of the island-bridge structure-based organohydrogel all-dielectric stretchable microwave absorber prepared in Example 2 under unstretched and 30% stretching ratios. DETAILED DESCRIPTION

[0018] The present invention is further described below in conjunction with the accompanying drawings and specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art. Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0019] Example 1

[0020] Firstly, an island bridge model was designed by moving an organic hydrogel-based diamond hollow grid with a diagonal length of 32 mm, a wall width of 4 mm and a thickness of 6 mm 20 mm along its diagonal direction and filling the hollow area formed by the intersection of the vertex angles; the printing temperature of the 3D printer was set to 210°C, the printing accuracy to 0.01 mm, the minimum layer thickness of the nozzle to 0.05 mm, the printing speed to 6 mm / s, and the filling rate to 100%. Print polylactic acid plastic into a template of an island bridge structure by a fused deposition modeling 3D printer; add acrylamide, N,N′-methylenebisacrylamide and ammonium persulfate in a mass ratio of 2:0.003:0.03 to a binary solvent of deionized water and glycerol in a mass ratio of 1:1, wherein the mass ratio of acrylamide to the binary solvent is 1:3, and stir until completely dissolved, then add a little N,N,N′,N′-tetramethylethylenediamine to the above solution under stirring to obtain an organic hydrogel precursor solution, and then quickly transfer the precursor solution to the template of the island bridge structure printed by the above 3D printing, and cross-link and solidify, and after demolding, the fully dielectric island bridge structure organic hydrogel-based metamaterial is obtained; in order to better realize the stretching operation, the obtained fully dielectric island bridge structure organic hydrogel-based metamaterial is attached to a rubber film, and finally attached to a 0.2 mm thick metal plate to form an organic hydrogel fully dielectric stretchable microwave absorber based on an island bridge structure;

[0021] The frequency-reflection loss curves of unstretched and 30% stretched ratios were measured by the bow frame method. The results are shown in Figure 3 The stretching test method fixes the stretched all-dielectric island-bridge structure organic hydrogel-based metamaterial on the metal plate by controlling the length of the metal plate layer. In the unstretched state, it is found that the reflection loss at 4.7-18GHz is less than -10dB, see Figure 2 The curve marked by the square in the middle; under the stretched state and TE polarization, the high-frequency peak can be shifted to the left, gradually moving from 13 GHz to 11 GHz, and its peak value increases from -22 dB to -29 dB. The absorption intensity in the mid-frequency band, especially the X-band, is significantly enhanced, and effective absorption is achieved in the range of 5.8-17.8 GHz, see Figure 2 The curve marked with the five-pointed star in the middle; under TM polarization, the high-frequency peak can be shifted to the right, gradually moving from 13 GHz to 15.8 GHz, and its peak value increases from -22 dB to -30 dB, and effective absorption is achieved in a bandwidth range of about 12 GHz, see Figure 2 The curve marked by the triangle in the middle. The invention designs an organic hydrogel-based all-dielectric stretchable microwave absorber based on an island-bridge structure, which can achieve the regulation of the absorption peak position and intensity by stretching, and achieves stable microwave absorption performance with a bandwidth of about 12GHz under different polarizations. This is difficult to achieve with conventional microwave absorbing materials. This fully demonstrates that this invention improves the stability of microwave absorption performance under stretching.

[0022] Example 2

[0023] A new island bridge structure is designed by moving an organic hydrogel-based diamond hollow grid with a diagonal length of 34 mm, a wall width of 4 mm and a thickness of 6.5 mm by 22 mm along its diagonal direction and filling the hollow area formed by the intersection of the top angles. The rest of the manufacturing method is basically the same as that of Example 1.

[0024] The frequency-reflection loss curves of unstretched and 30% stretched ratios were measured by the bow frame method. The results are shown in Figure 3 The stretching test method is the same as that of Example 1. In the unstretched state, it is found that the reflection loss is less than -10dB in the frequency range of 4.5-17.4GHz. Figure 3 The curve marked by the square in the middle; under the stretched state and TE polarization, the absorption intensity of the central peak can be enhanced, and its peak value increases from -23.5dB to -25.8dB, and effective absorption is achieved in the range of 4.7-17.4GHz, see Figure 3 The curve marked with the five-pointed star in the middle; under TM polarization, the peak value of the high-frequency peak can be tuned, gradually moving from -19.4dB to -22.2dB, and effective absorption can be achieved in a bandwidth range of about 13GHz, see Figure 3 The curve marked by the middle triangle. This is difficult to achieve with conventional microwave absorbing materials. This fully demonstrates that by adjusting the proportion of the island structure, the organic hydrogel-based all-dielectric stretchable microwave absorber based on the island-bridge structure involved in this invention can achieve the regulation of the absorption peak position and intensity by stretching, and significantly improve the stability of microwave absorption performance at 5-17GHz.

[0025] By comparing the structure and absorption performance data of the all-dielectric island-bridge structure organic hydrogel-based metamaterial in the above embodiment, it can be found that as the proportion of the island structure in the island-bridge structure changes, the microwave absorption performance of the all-dielectric island-bridge structure organic hydrogel-based metamaterial under the stretching state changes, which can be explained by changing the proportion of the island structure in the island-bridge structure. The absorption stability of the organic hydrogel-based all-dielectric stretchable microwave absorber based on the island-bridge structure can be adjusted. This design has important potential in the development and application of microwave absorption materials in the future, and is not only applicable to the fields of communications and flexible electronics, but can also be extended to high-tech industries such as radar and stealth technology.

Claims

1. An organohydrogel all-dielectric stretchable microwave absorber based on an island-bridge structure, characterized in that: The invention discloses an all-dielectric island-bridge structure organic hydrogel-based metamaterial, wherein the island-bridge structure is a periodic array formed by moving the organic hydrogel-based diamond hollow grids along their diagonal directions and filling the hollow areas formed by the intersection of the top corners.

2. The all-dielectric island-bridge structure organic hydrogel-based metamaterial according to claim 1, characterized in that: The diagonal length of the organic hydrogel-based diamond hollow grid is preferably 28 to 36 mm, the wall width is preferably 3.0 to 5.0 mm, the moving distance is preferably 18 to 22 mm, and the thickness is preferably 5.2 to 6.8 mm.

3. A method for preparing an organohydrogel all-dielectric stretchable microwave absorber based on an island-bridge structure, characterized in that: The following steps are included: Step 1: Printing a mold of the island-bridge structure through 3D printing technology; Step 2: Preparing an organic hydrogel in the mold obtained in step 1; Step 3: Demolding.

4. The method for preparing an organohydrogel all-dielectric stretchable microwave absorber based on an island-bridge structure according to claim 3, characterized in that: The preparation method of the organic hydrogel is as follows: acrylamide, N,N'-methylenebisacrylamide and ammonium persulfate are fully dissolved in a binary solvent of deionized water and glycerol, and then N,N,N',N'-tetramethylethylenediamine is used to promote cross-linking at room temperature.

5. The method for preparing an organohydrogel according to claim 4, characterized in that: The acrylamide accounts for 25% of the total proportion, and the mass of glycerol accounts for 33.3% to 80% of the binary solvent proportion of deionized water and glycerol.

6. A method for preparing an organohydrogel all-dielectric stretchable microwave absorber based on an island-bridge structure prepared by the preparation method according to any one of claims 3 to 5.

7. Application of the method for preparing an organohydrogel all-dielectric stretchable microwave absorber based on an island-bridge structure according to any one of claims 1 to 6 in the field of electromagnetic wave absorption.

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