A temperature-responsive microwave absorbing metamaterial, its preparation method and application

Abstract

This invention discloses a temperature-responsive absorbing metamaterial, its preparation method, and its applications. The temperature-responsive absorbing metamaterial comprises an absorbing substrate and a flower-shaped structural unit. The flower-shaped structural unit comprises an absorbing prism and an absorbing-thermal-response sheet. The bottom surface of the absorbing prism is connected to the absorbing substrate, and an absorbing-thermal-response sheet is connected to each side of the absorbing prism. The absorbing-thermal-response sheet comprises an absorbing layer and a liquid crystal elastomer layer. The absorbing substrate, the absorbing prism, and the absorbing layer all comprise polyurethane acrylate containing dynamic disulfide bonds and soft magnetic powder. The temperature-responsive absorbing metamaterial of this invention possesses advantages such as wide-band absorption, strong absorption, stable wide-angle incident wave absorption performance, dynamically reversibly adjustable wave absorption performance, wide range of wave absorption performance adjustment, and self-healing capability. It can be widely used in 5G / 6G communications, consumer electronics, and new energy vehicles.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wave-absorbing materials, in particular to a temperature-responsive wave-absorbing metamaterial, a preparation method and application thereof. BACKGROUND

[0002] With the rapid progress of wireless communication, Internet of Things and consumer electronics technology, the number of electronic devices and base stations has increased significantly, which leads to the increasingly complex electromagnetic wave environment. The increasing electromagnetic radiation not only causes signal interference between electronic devices, affects communication accuracy and safety, but also threatens human health. Therefore, developing new wave-absorbing materials with wide-band strong absorption performance has important social significance and economic value for governing electromagnetic pollution and ensuring information security.

[0003] Wave-absorbing metamaterial is a new type of wave-absorbing material, which can be designed to control electromagnetic properties through structure design, breaking the limitations of traditional wave-absorbing materials that depend on thickness and have single performance. It has attracted widespread attention from researchers. In recent years, researchers have begun to design wave-absorbing metamaterials using nanocarbon materials, shape memory materials, phase change materials, etc., which has promoted the development of wave-absorbing metamaterials in the direction of tunable and dynamic control. However, existing wave-absorbing metamaterials still have problems such as narrow wave-absorbing performance control range and complex control conditions, which cannot fully meet the requirements of practical applications.

[0004] Therefore, it is of great significance to develop a wave-absorbing metamaterial with excellent wave-absorbing performance, wide wave-absorbing performance control range and simple wave-absorbing performance control. SUMMARY

[0005] The present application aims to provide a temperature-responsive wave-absorbing metamaterial, a preparation method and application thereof.

[0006] The technical solution adopted by the present application is as follows:

[0007] A temperature-responsive wave-absorbing metamaterial, which comprises a wave-absorbing substrate and a flower-shaped structure unit, the flower-shaped structure unit comprises a wave-absorbing right prism and a wave-absorbing-thermal response sheet, the bottom surface of the wave-absorbing right prism is connected to the wave-absorbing substrate, and the wave-absorbing-thermal response sheet is connected to any side surface of the wave-absorbing right prism, the wave-absorbing-thermal response sheet comprises a wave-absorbing layer and a liquid crystal elastomer layer, and the wave-absorbing substrate, the wave-absorbing right prism and the wave-absorbing layer all comprise a polyurethane acrylate containing a dynamic disulfide bond and a soft magnetic powder.

[0008] Preferably, the flower-shaped structure unit has multiple units and is uniformly distributed on the surface of the wave-absorbing substrate.

[0009] Preferably, the wave-absorbing right prism has a bottom edge number of 3-12, a bottom surface circumscribed circle radius of 3.0-10.0 mm, and a side edge length of 0.5-2.5 mm.

[0010] Preferably, the microwave-absorbing thermal response sheet is rectangular, with the short side of the rectangle connected to the side of the microwave-absorbing prism, and the length of the long side of the rectangle is 5.0 mm to 25.0 mm.

[0011] Preferably, the length of the shorter side of the rectangle is the same as the side length of the base of the microwave-absorbing prism.

[0012] Preferably, the plane containing the microwave-absorbing thermal response sheet is parallel to the bottom surface of the microwave-absorbing prism.

[0013] Preferably, the absorbing layer is close to the absorbing substrate, and the liquid crystal elastomer layer is far from the absorbing substrate.

[0014] Preferably, the mass ratio of polyurethane acrylate containing dynamic disulfide bonds to soft magnetic powder in the microwave absorbing substrate is 1:0.5 to 4.0.

[0015] Preferably, the thickness of the absorbing substrate is 1.0 mm to 5.0 mm.

[0016] Preferably, the mass ratio of polyurethane acrylate containing dynamic disulfide bonds to soft magnetic powder in the microwave absorbing prism is 1:0.5 to 4.0.

[0017] Preferably, the mass ratio of polyurethane acrylate containing dynamic disulfide bonds to soft magnetic powder in the absorbing layer is 1:0.5 to 4.0.

[0018] Preferably, the thickness of the absorbing layer is 0.5 mm to 2.5 mm.

[0019] Preferably, the raw materials for preparing the polyurethane acrylate containing dynamic disulfide bonds include polyethylene glycol, isocyanate, hydroxyl-terminated disulfide, and hydroxy acrylate.

[0020] Preferably, the molar ratio of polyethylene glycol, isocyanate, hydroxyl-terminated disulfide, and hydroxy acrylate is 1:1.2-2.6:0.2-0.8:0.2-1.0.

[0021] Preferably, the number-average molecular weight of the polyethylene glycol is 500 g / mol to 5000 g / mol.

[0022] Preferably, the isocyanate is at least one of toluene diisocyanate, isophorone diisocyanate, and diphenylmethane diisocyanate.

[0023] Preferably, the hydroxyl-terminated disulfide is at least one of hydroxyethyl disulfide and hydroxypropyl disulfide.

[0024] Preferably, the hydroxyacrylate is at least one of hydroxypropyl acrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate.

[0025] Preferably, the polyurethane acrylate containing dynamic disulfide bonds is prepared by a method comprising the following steps:

[0026] a) Polyethylene glycol, isocyanate, hydroxyl-terminated disulfide and catalyst are dispersed in an organic solvent for prepolymerization, then hydroxy acrylate is added for end-capping, and then dried to obtain polyurethane acrylate.

[0027] b) Dilute polyurethane acrylate with hydroxy acrylate, add a photoinitiator, and then perform photocuring to obtain polyurethane acrylate containing dynamic disulfide bonds.

[0028] Preferably, the catalyst in step a) is at least one of bis(dimethylaminoethyl ether) (BDMAEE), pentamethyldiethylenetriamine (PMDETA), and dibutyltin dilaurate.

[0029] Preferably, the amount of catalyst used in step a) is 1% to 5% of the mass of polyethylene glycol.

[0030] Preferably, the organic solvent in step a) is at least one of tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, and toluene.

[0031] Preferably, the prepolymerization in step a) is carried out at a temperature of 60°C to 80°C for a reaction time of 2 to 8 hours.

[0032] Preferably, the end-capping in step a) is carried out at a temperature of 60°C to 80°C for a reaction time of 2 to 8 hours.

[0033] Preferably, the drying in step a) is carried out at a temperature of 20℃ to 90℃ for a drying time of 5h to 72h.

[0034] Preferably, the photoinitiator in step b) is at least one of 2,4,6-trimethylbenzoyl diphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoyl phenylphosphine ester, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and 2,4,6-trimethylbenzoyl-4'-methyldiphenylphosphine oxide.

[0035] Preferably, the amount of photoinitiator used in step b) is 0.5% to 5% of the mass of polyurethane acrylate.

[0036] Preferably, the soft magnetic powder is at least one of carbonyl iron powder, iron-nickel alloy powder, iron-cobalt alloy powder, iron-silicon-aluminum powder, iron-based nanocrystalline powder, and iron oxide powder.

[0037] Preferably, the thickness of the liquid crystal elastomer layer is 0.2 mm to 1.0 mm.

[0038] Preferably, the liquid crystal elastomer layer comprises a liquid crystal elastomer formed by copolymerization of 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene and 2,2'-(1,2-ethylenedioxy)bis(ethanethiol).

[0039] Preferably, the molar ratio of 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene to 2,2'-(1,2-ethylenedioxy)bis(ethanethiol) is 1:1.0 to 1.5.

[0040] Preferably, the molecular chains of the liquid crystal elastomer are oriented in a direction parallel to the long side of the microwave-absorbing and thermally-response sheet.

[0041] Preferably, the liquid crystal elastomer is prepared by a method comprising the following steps:

[0042] i) 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene, 2,2'-(1,2-ethylenedioxydioxo)bisethyl mercaptan and dipropylamine were dispersed in a solvent and reacted. After adding a photoinitiator, the mixture was dried to obtain a liquid crystal elastomer prepolymer.

[0043] ii) The liquid crystal elastomer prepolymer is photocured to obtain the liquid crystal elastomer.

[0044] Preferably, the amount of dipropylamine used in step i) is 1% to 5% of the mass of 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene.

[0045] Preferably, the solvent in step i) is at least one of dichloromethane, chloroform, tetrahydrofuran, and ethyl acetate.

[0046] Preferably, the photoinitiator in step i) is at least one of 2,4,6-trimethylbenzoyl diphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoyl phenylphosphine ester, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and 2,4,6-trimethylbenzoyl-4'-methyldiphenylphosphine oxide.

[0047] Preferably, the amount of photoinitiator used in step i) is 0.5% to 4% of the mass of 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene.

[0048] Preferably, the drying in step i) is carried out at a temperature of 20°C to 90°C for a drying time of 5 to 72 hours.

[0049] Preferably, the response temperature range of the temperature-responsive absorbing metamaterial is 20℃ to 90℃.

[0050] A method for preparing a temperature-responsive microwave absorbing metamaterial as described above includes the following steps:

[0051] 1) Digital light processing (DLP) printing technology is used to print the absorbing substrate, absorbing prism and absorbing layer respectively. Then, printing paste is applied to the surface of the absorbing substrate and the side of the absorbing prism before assembly. Finally, thermosetting is performed to achieve the connection between the absorbing prism and the absorbing substrate and absorbing layer.

[0052] 2) A liquid crystal elastomer layer is printed on the surface of the microwave absorbing layer by direct ink writing (DIW) technology through photopolymerization printing to obtain a temperature-responsive microwave absorbing metamaterial.

[0053] Preferably, the process parameters for digital light processing printing in step 1) include: bottom layer exposure time of 60s to 120s, model exposure time of 25s to 80s, slice thickness of 20μm to 50μm, ultraviolet light wavelength of 380nm to 420nm, and light intensity of 5000μW·cm. -2 ~10000μW·cm -2 .

[0054] Preferably, the thermosetting in step 1) is carried out at a temperature of 60℃ to 80℃, and the curing time is 12h to 48h.

[0055] Preferably, the process parameters for direct ink writing in step 2) include: needle inner diameter of 300μm to 2000μm, and dispensing speed of 1mm·s. -1 ~10mm·s -1 The printing air pressure is 300kPa~500kPa, the printing temperature is 60℃~80℃, the ultraviolet light wavelength is 380nm~420nm, and the light intensity is 5000μW·cm. -2 ~10000μW·cm -2 The distance between the needle tip and the printing plate is 100μm to 1000μm. The printing path is a continuous serpentine trajectory, which consists of multiple parallel line segments and turning segments connecting their ends, filling the printing area in a continuous manner.

[0056] An electromagnetic shielding device comprising the aforementioned temperature-responsive absorbing metamaterial.

[0057] Applications of a temperature-responsive absorbing metamaterial as described above in the fields of 5G / 6G communications, consumer electronics, or new energy vehicles.

[0058] The principle of this invention: The microwave absorbing metamaterial of this invention has temperature response characteristics. By adjusting the ambient temperature, the liquid crystal elastomer layer can drive the microwave absorbing-thermal response sheet to bend and deform, thereby realizing the expansion and closure of the flower-shaped structural unit. This can form flower-shaped superstructures with different degrees of expansion. The microwave absorption performance of flower-shaped superstructures with different degrees of expansion is different. Therefore, the absorption mode can be dynamically and reversibly controlled by temperature control.

[0059] The beneficial effects of the present invention are as follows: The temperature-responsive absorbing metamaterial of the present invention has the advantages of wide-band absorption, strong absorption, stable wide-angle incident wave absorption performance, dynamic and reversible controllability of wave absorption performance, wide range of wave absorption performance control, and self-repair capability. It can be widely used in 5G / 6G communication, consumer electronics and new energy vehicles and other fields. Moreover, its preparation process is simple and controllable, making it suitable for large-scale industrial production and application.

[0060] Specifically:

[0061] 1) The temperature-responsive absorbing metamaterial of the present invention comprises flower-shaped structural units. Microwaves can undergo multiple reflections and scattering within the flower-shaped structural units, which can enhance resonant interference absorption. Therefore, the absorbing metamaterial can exhibit significant broadband absorption performance in the microwave band. When the flower-shaped structural units are closed, the absorption frequency band of the absorbing metamaterial can cover 3.3 GHz to 18.0 GHz, and the maximum effective absorption bandwidth can reach 14.7 GHz.

[0062] 2) The flower-shaped structural units in the temperature-responsive absorbing metamaterial of the present invention maintain centrosymmetry, so its absorption performance is polarization insensitive, which can ensure that the absorbing metamaterial can still achieve stable absorption when the incident angle of electromagnetic waves changes over a wide range, and has excellent wide-angle absorption performance.

[0063] 3) The temperature-responsive absorbing metamaterial of the present invention is a tunable absorbing metamaterial based on thermally responsive liquid crystal elastomers. It has the advantages of wide and tunable absorption frequency band and high absorption intensity. By controlling the ambient temperature, the configuration of the liquid crystal elastomer, which is oriented by direct ink writing, can be induced. This can drive the unfolding and closing of the flower-like structural units, and the macroscopic structure of the absorbing metamaterial can be controlled (different ambient temperatures correspond to different degrees of closure). This enables large-scale dynamic reversible control of the absorption performance, with the maximum effective absorption bandwidth ranging from 1.4 GHz to 14.7 GHz.

[0064] 4) The temperature-responsive absorbing metamaterial of the present invention uses polyurethane acrylate containing dynamic disulfide bonds as the matrix of the absorbing unit (absorbing substrate, absorbing prism and absorbing layer in the absorbing-thermal response sheet). After heating, the modulus of the absorbing metamaterial can be significantly reduced, which is not only beneficial to the driving of liquid crystal elastomer, but also enables the self-repair of the absorbing unit matrix. Attached Figure Description

[0065] Figure 1 This is a top view of the temperature-responsive absorbing metamaterial of the present invention.

[0066] Figure 2 This is a cross-sectional view of the temperature-responsive absorbing metamaterial of the present invention.

[0067] Figure 3 This is a schematic diagram showing the closed state of the flower-shaped structural unit in this invention at different temperatures.

[0068] Figure 4 The image shows the reflection loss-frequency relationship curves of the temperature-response absorbing metamaterial of Example 1 at different temperatures.

[0069] Figure 5 The curves show the reflection loss-frequency relationship of the temperature-responsive absorbing metamaterial of Example 1 at 90°C for transverse microwaves with different incident angles.

[0070] Figure 6 The reflection loss-frequency relationship curves of the temperature-response absorbing metamaterials of Examples 1-5 and the absorbing materials of Comparative Examples 1-2 at 90°C are shown.

[0071] Figure 7 The figure shows the test results of the temperature response performance of the flower-shaped structural unit in the temperature-responsive absorbing metamaterial of Example 3.

[0072] Explanation of the symbols in the attached diagram: 1. Absorbing substrate; 2. Flower-shaped structural unit; 10. Absorbing prism; 20. Absorbing-thermal response sheet; 100. Absorbing layer; 200. Liquid crystal elastomer layer. Detailed Implementation

[0073] The present invention will be further explained and described below with reference to specific embodiments.

[0074] Example 1:

[0075] A temperature-responsive microwave absorbing metamaterial (structural schematic shown) Figure 1 and Figure 2 As shown, Figure 1 This is a top view. Figure 2 The diagram shows a cross-sectional view; schematic diagrams of the closed state of the flower-like structural unit at different temperatures are shown below. Figure 3As shown, it consists of an absorbing substrate 1 and a flower-shaped structural unit 2; the absorbing substrate 1 is square with a side length of 40.0 mm and a thickness of 2.1 mm; the flower-shaped structural unit 2 consists of an absorbing regular prism 10 and an absorbing-thermal-response sheet 20; the bottom surface of the absorbing regular prism 10 is connected to the absorbing substrate 1; an absorbing-thermal-response sheet 20 is connected to any side surface of the absorbing regular prism 10; the absorbing regular prism 10 is a regular octagonal prism with a base circumcircle radius of 6.5 mm and a side edge length of 2.0 mm; the absorbing-thermal-response sheet 20 consists of an absorbing layer 100 and a liquid crystal elastomer layer 200, the thickness of the absorbing layer 100 being 2.0 mm. The absorbing layer 100 is close to the absorbing substrate 1, and the liquid crystal elastomer layer 200 is 0.4 mm thick and is far from the absorbing substrate 1. The absorbing-thermal response sheet 20 is rectangular, with its short side connected to the side of the absorbing prism 10. The length of the short side of the rectangle is the same as the length of the bottom side of the absorbing prism 10, and the length of the long side of the rectangle is 13.0 mm. The plane of the absorbing-thermal response sheet 20 is parallel to the bottom surface of the absorbing prism 10. The absorbing substrate 1, the absorbing prism 10, and the absorbing layer 100 are all composed of polyurethane acrylate containing dynamic disulfide bonds and iron-based nanocrystalline powder.

[0076] The preparation method of the above-mentioned temperature-responsive absorbing metamaterial is as follows:

[0077] 1) Fabrication and assembly of the absorbing substrate, absorbing prism, and absorbing layer:

[0078] a) Polyethylene glycol with a number average molecular weight of 1000 g / mol was dried and dehydrated at 120 °C for 0.5 h. Then, polyethylene glycol, isophorone diisocyanate, hydroxyethyl disulfide and dibutyltin dilaurate were dispersed in tetrahydrofuran and stirred at 60 °C for 3 h under a nitrogen atmosphere. Hydroxyethyl acrylate was then added and stirred for another 3 h. The molar ratio of polyethylene glycol, isophorone diisocyanate, hydroxyethyl disulfide and hydroxyethyl acrylate was 1:1.6:0.4:0.4. The amount of dibutyltin dilaurate was 1.5% of the mass of polyethylene glycol. The mixture was then vacuum dried at room temperature for 48 h to obtain polyurethane acrylate.

[0079] b) Polyurethane acrylate, hydroxyethyl acrylate, iron-based nanocrystalline powder (median particle size of 4 μm) and ethyl 2,4,6-trimethylbenzoylphenylphosphinate were mixed and stirred evenly. The mass ratio of polyurethane acrylate, hydroxyethyl acrylate, iron-based nanocrystalline powder and ethyl 2,4,6-trimethylbenzoylphenylphosphinate was 1:1:6:0.05 to obtain DLP printing slurry.

[0080] c) A DLP printer was used to print the microwave absorbing substrate, microwave absorbing prism, and microwave absorbing layer using DLP printing paste. The printing parameters were as follows: bottom layer exposure time was 100s, model exposure time was 60s, slice thickness was 25μm, ultraviolet wavelength was 405nm, and light intensity was 7000μW·cm. -2 Then, DLP printing paste is coated on the surface of the absorbing substrate and the side of the absorbing prism before assembly. Finally, it is placed at 80℃ for 12 hours to achieve the connection between the absorbing prism, the absorbing substrate, and the absorbing layer.

[0081] 2) Preparation of the liquid crystal elastomer layer:

[0082] i) Dissolve 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene, 2,2'-(1,2-ethylenedioxy)bis(ethanediol)diethylthiol and dipropylamine in dichloromethane. The molar ratio of 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene to 2,2'-(1,2-ethylenedioxy)bis(ethanediol)diethylthiol is 1:1.2. The amount of dipropylamine used is 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene to 2,2'-(1,2-ethylenedioxy)bis(ethanediol)diethylthiol. 2% of the mass of 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene was added and stirred at room temperature for 12 h. Then, ethyl 2,4,6-trimethylbenzoylphenylphosphinate was added and stirred until homogeneous. The amount of ethyl 2,4,6-trimethylbenzoylphenylphosphinate was 1% of the mass of 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene was added and then dried under vacuum at 80 °C for 24 h to obtain the liquid crystal elastomer prepolymer.

[0083] ii) A liquid crystal elastomer layer was printed on the surface of the microwave absorbing layer using a DIW printer with a liquid crystal elastomer prepolymer (preheated at 70°C for 30 minutes before printing). The printing parameters were as follows: needle inner diameter of 1000 μm and dispensing speed of 1 mm·s. -1 The printing pressure was 400 kPa, the printing temperature was 70℃, the ultraviolet light wavelength was 405 nm, and the light intensity was 10000 μW·cm. -2 The distance between the needle tip and the printing substrate is 200μm. The printing path is a continuous serpentine trajectory, which consists of multiple parallel line segments and turning segments connecting their ends. The printing area is filled in a continuous manner to obtain a temperature-responsive microwave absorbing metamaterial.

[0084] Example 2:

[0085] A temperature-responsive absorbing metamaterial (structure same as in Example 1) is provided, with the following adjustments compared to the temperature-responsive absorbing metamaterial of Example 1: the side length of the absorbing substrate is adjusted to 45.0 mm, and the thickness is adjusted to 1.9 mm; the radius of the circumscribed circle of the bottom surface of the absorbing prism is adjusted to 8.0 mm, and the length of the side edges is adjusted to 2.5 mm; the thickness of the absorbing layer is adjusted to 2.5 mm; the thickness of the liquid crystal elastomer layer is adjusted to 0.3 mm; the length of the long side of the absorbing-thermal-response sheet is adjusted to 16.0 mm; and the iron-based nanocrystalline powder in the absorbing substrate, the absorbing prism, and the absorbing layer is replaced with carbonyl iron powder.

[0086] The preparation method of the above-mentioned temperature-responsive absorbing metamaterial is as follows:

[0087] 1) Fabrication and assembly of the absorbing substrate, absorbing prism, and absorbing layer:

[0088] a) Polyethylene glycol with a number average molecular weight of 800 g / mol was dried and dehydrated at 120 °C for 0.5 h. Then, polyethylene glycol, isophorone diisocyanate, hydroxypropyl disulfide and dibutyltin dilaurate were dispersed in tetrahydrofuran and stirred at 70 °C for 2 h under a nitrogen atmosphere. Hydroxyethyl acrylate was then added and stirred for 3 h. The molar ratio of polyethylene glycol, isophorone diisocyanate, hydroxypropyl disulfide and hydroxyethyl acrylate was 1:1.4:0.3:0.3. The amount of dibutyltin dilaurate was 1.5% of the mass of polyethylene glycol. The mixture was then vacuum dried at room temperature for 48 h to obtain polyurethane acrylate.

[0089] b) Polyurethane acrylate, hydroxyethyl acrylate, carbonyl iron powder (median particle size of 3 μm) and ethyl 2,4,6-trimethylbenzoylphenylphosphinate are mixed and stirred evenly. The mass ratio of polyurethane acrylate, hydroxyethyl acrylate, carbonyl iron powder and ethyl 2,4,6-trimethylbenzoylphenylphosphinate is 1:1.5:7.5:0.05 to obtain DLP printing paste.

[0090] c) A DLP printer was used to print the microwave absorbing substrate, microwave absorbing prism, and microwave absorbing layer using DLP printing paste. The printing parameters were as follows: bottom layer exposure time was 80s, model exposure time was 50s, slice thickness was 25μm, ultraviolet wavelength was 405nm, and light intensity was 7000μW·cm. -2 Then, DLP printing paste is coated on the surface of the absorbing substrate and the side of the absorbing prism before assembly. Finally, it is placed at 80℃ for 12 hours to achieve the connection between the absorbing prism, the absorbing substrate, and the absorbing layer.

[0091] 2) Preparation of the liquid crystal elastomer layer:

[0092] i) Dissolve 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene, 2,2'-(1,2-ethylenedioxy)bis(ethanediol)diethylthiol and dipropylamine in dichloromethane. The molar ratio of 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene to 2,2'-(1,2-ethylenedioxy)bis(ethanediol)diethylthiol is 1:1.2. The amount of dipropylamine used is 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene to 2,2'-(1,2-ethylenedioxy)bis(ethanediol)diethylthiol. 2% of the mass of 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene was added and stirred at room temperature for 12 h. Then, ethyl 2,4,6-trimethylbenzoylphenylphosphinate was added and stirred until homogeneous. The amount of ethyl 2,4,6-trimethylbenzoylphenylphosphinate was 2% of the mass of 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene was added and then dried under vacuum at 80 °C for 24 h to obtain the liquid crystal elastomer prepolymer.

[0093] ii) A liquid crystal elastomer layer was printed on the surface of the microwave absorbing layer using a DIW printer with a liquid crystal elastomer prepolymer (preheated at 70°C for 30 minutes before printing). The printing parameters were as follows: needle inner diameter of 1500 μm and dispensing speed of 1 mm·s. -1 The printing pressure was 400 kPa, the printing temperature was 70℃, the ultraviolet light wavelength was 405 nm, and the light intensity was 10000 μW·cm. -2 The distance between the needle tip and the printing substrate is 300μm. The printing path is a continuous serpentine trajectory, which consists of multiple parallel line segments and turning segments connecting their ends. The printing area is filled in a continuous manner to obtain a temperature-responsive absorbing metamaterial.

[0094] Example 3:

[0095] A temperature-responsive absorbing metamaterial (structure same as in Example 1) is provided, with the following adjustments compared to the temperature-responsive absorbing metamaterial of Example 1: the side length of the absorbing substrate is adjusted to 42.0 mm, and the thickness is adjusted to 1.9 mm; the radius of the circumscribed circle of the bottom surface of the absorbing prism is adjusted to 6.2 mm, and the length of the side edges is adjusted to 1.0 mm; the thickness of the absorbing layer is adjusted to 1.0 mm; the thickness of the liquid crystal elastomer layer is adjusted to 0.2 mm; the length of the long side of the absorbing-thermal-response sheet is adjusted to 15.0 mm; and the iron-based nanocrystalline powder in the absorbing substrate, the absorbing prism, and the absorbing layer is replaced with iron-nickel alloy powder.

[0096] The preparation method of the above-mentioned temperature-responsive absorbing metamaterial is as follows:

[0097] 1) Fabrication and assembly of the absorbing substrate, absorbing prism, and absorbing layer:

[0098] a) Polyethylene glycol with a number average molecular weight of 1000 g / mol was dried and dehydrated at 120 °C for 0.5 h. Then, polyethylene glycol, toluene diisocyanate, hydroxyethyl disulfide and dibutyltin dilaurate were dispersed in tetrahydrofuran and stirred at 60 °C for 3 h under a nitrogen atmosphere. Hydroxyethyl acrylate was then added and stirred for another 3 h. The molar ratio of polyethylene glycol, toluene diisocyanate, hydroxyethyl disulfide and hydroxyethyl acrylate was 1:2:0.6:0.6. The amount of dibutyltin dilaurate was 2% of the mass of polyethylene glycol. The mixture was then vacuum dried at room temperature for 48 h to obtain polyurethane acrylate.

[0099] b) Polyurethane acrylate, hydroxyethyl acrylate, iron-nickel alloy powder (median particle size of 10 μm) and ethyl 2,4,6-trimethylbenzoylphenylphosphinate were mixed and stirred evenly. The mass ratio of polyurethane acrylate, hydroxyethyl acrylate, iron-nickel alloy powder and ethyl 2,4,6-trimethylbenzoylphenylphosphinate was 1:1.2:6:0.06 to obtain DLP printing paste.

[0100] c) A DLP printer was used to print the microwave absorbing substrate, microwave absorbing prism, and microwave absorbing layer using DLP printing paste. The printing parameters were as follows: bottom layer exposure time was 100s, model exposure time was 80s, slice thickness was 50μm, ultraviolet wavelength was 405nm, and light intensity was 9000μW·cm. -2 Then, DLP printing paste is coated on the surface of the absorbing substrate and the side of the absorbing prism before assembly. Finally, it is placed at 80℃ for 12 hours to achieve the connection between the absorbing prism, the absorbing substrate, and the absorbing layer.

[0101] 2) Preparation of the liquid crystal elastomer layer:

[0102] i) Dissolve 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene, 2,2'-(1,2-ethylenedioxy)bis(ethanediol)diethylthiol and dipropylamine in dichloromethane. The molar ratio of 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene to 2,2'-(1,2-ethylenedioxy)bis(ethanediol)diethylthiol is 1:1.1. The amount of dipropylamine used is 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene to 2,2'-(1,2-ethylenedioxy)bis(ethanediol)diethylthiol. 3% of the mass of 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene was added and stirred at room temperature for 8 hours. Then, ethyl 2,4,6-trimethylbenzoylphenylphosphinate was added and stirred until homogeneous. The amount of ethyl 2,4,6-trimethylbenzoylphenylphosphinate was 1.5% of the mass of 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene was added and stirred until homogeneous. The mixture was then dried under vacuum at 80°C for 24 hours to obtain the liquid crystal elastomer prepolymer.

[0103] ii) A liquid crystal elastomer layer was printed on the surface of the microwave absorbing layer using a DIW printer with a liquid crystal elastomer prepolymer (preheated at 80°C for 30 minutes before printing). The printing parameters were as follows: needle inner diameter 800 μm, dispensing speed 1.1 mm·s. -1 The printing pressure was 400 kPa, the printing temperature was 80℃, the ultraviolet light wavelength was 405 nm, and the light intensity was 10000 μW·cm. -2 The distance between the needle and the printing substrate is 100μm. The printing path is a continuous serpentine trajectory, which consists of multiple parallel line segments and turning segments connecting their ends. The printing area is filled in a continuous manner to obtain a temperature-responsive absorbing metamaterial.

[0104] Example 4:

[0105] A temperature-responsive absorbing metamaterial (structure same as in Example 1) is provided, with the following adjustments compared to the temperature-responsive absorbing metamaterial of Example 1: the thickness of the absorbing substrate is adjusted to 2.0 mm; the absorbing prism is adjusted to a regular hexagonal prism; the radius of the circumscribed circle of the base of the absorbing prism is adjusted to 7.0 mm; the thickness of the liquid crystal elastomer layer is adjusted to 0.3 mm; the length of the long side of the absorbing-thermal-response sheet is adjusted to 10.0 mm; and the iron-based nanocrystalline powder in the absorbing substrate, the absorbing prism, and the absorbing layer is replaced with iron-silicon-aluminum powder.

[0106] The preparation method of the above-mentioned temperature-responsive absorbing metamaterial is as follows:

[0107] 1) Fabrication and assembly of the absorbing substrate, absorbing prism, and absorbing layer:

[0108] a) Polyethylene glycol with a number average molecular weight of 2000 g / mol was dried and dehydrated at 120 °C for 0.5 h. Then, polyethylene glycol, diphenylmethane diisocyanate, hydroxyethyl disulfide and dimethylaminoethyl ether were dispersed in tetrahydrofuran. The mixture was then stirred at 60 °C for 3 h under a nitrogen atmosphere. Hydroxypropyl acrylate was then added and the mixture was stirred for another 3 h. The molar ratio of polyethylene glycol, diphenylmethane diisocyanate, hydroxyethyl disulfide and hydroxypropyl acrylate was 1:2:0.6:0.6. The amount of dimethylaminoethyl ether was 1% of the mass of polyethylene glycol. The mixture was then vacuum dried at room temperature for 72 h to obtain polyurethane acrylate.

[0109] b) Polyurethane acrylate, hydroxyethyl acrylate, iron-silicon-aluminum powder (median particle size of 5 μm) and ethyl 2,4,6-trimethylbenzoylphenylphosphine were mixed and stirred evenly. The mass ratio of polyurethane acrylate, hydroxyethyl acrylate, iron-silicon-aluminum powder and ethyl 2,4,6-trimethylbenzoylphenylphosphine was 1:1.2:7:0.06 to obtain DLP printing paste.

[0110] c) A DLP printer was used to print the microwave absorbing substrate, microwave absorbing prism, and microwave absorbing layer using DLP printing paste. The printing parameters were as follows: bottom layer exposure time was 100s, model exposure time was 80s, slice thickness was 25μm, ultraviolet wavelength was 405nm, and light intensity was 9000μW·cm. -2 Then, DLP printing paste is coated on the surface of the absorbing substrate and the side of the absorbing prism before assembly. Finally, it is placed at 80℃ for 12 hours to achieve the connection between the absorbing prism, the absorbing substrate, and the absorbing layer.

[0111] 2) Preparation of the liquid crystal elastomer layer:

[0112] i) Dissolve 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene, 2,2'-(1,2-ethylenedioxy)bis(ethanediol)diethylthiol and dipropylamine in dichloromethane. The molar ratio of 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene to 2,2'-(1,2-ethylenedioxy)bis(ethanediol)diethylthiol is 1:1.1. The amount of dipropylamine used is 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene to 2,2'-(1,2-ethylenedioxy)bis(ethanediol)diethylthiol. 3% of the mass of 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene was added and stirred at room temperature for 8 hours. Then, ethyl 2,4,6-trimethylbenzoylphenylphosphinate was added and stirred until homogeneous. The amount of ethyl 2,4,6-trimethylbenzoylphenylphosphinate was 2% of the mass of 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene was added and then dried under vacuum at 80°C for 24 hours to obtain the liquid crystal elastomer prepolymer.

[0113] ii) A liquid crystal elastomer layer was printed on the surface of the microwave absorbing layer using a DIW printer with a liquid crystal elastomer prepolymer (preheated at 60°C for 30 minutes before printing). The printing parameters were as follows: needle inner diameter 1200 μm, dispensing speed 1 mm·s. -1 The printing pressure was 400 kPa, the printing temperature was 60℃, the ultraviolet light wavelength was 405 nm, and the light intensity was 10000 μW·cm. -2 The distance between the needle and the printing substrate is 100μm. The printing path is a continuous serpentine trajectory, which consists of multiple parallel line segments and turning segments connecting their ends. The printing area is filled in a continuous manner to obtain a temperature-responsive absorbing metamaterial.

[0114] Example 5:

[0115] A temperature-responsive absorbing metamaterial (structure same as in Example 1) is provided, with the following adjustments compared to the temperature-responsive absorbing metamaterial of Example 1: the side length of the absorbing substrate is adjusted to 30.0 mm and the thickness is adjusted to 2.3 mm; the radius of the circumscribed circle of the bottom surface of the absorbing prism is adjusted to 4.0 mm and the length of the side edges is adjusted to 1.5 mm; the thickness of the absorbing layer is adjusted to 1.5 mm; the thickness of the liquid crystal elastomer layer is adjusted to 0.5 mm; the length of the long side of the absorbing-thermal-response sheet is adjusted to 8.0 mm; and the iron-based nanocrystalline powder in the absorbing substrate, the absorbing prism, and the absorbing layer is replaced with iron oxide powder.

[0116] The preparation method of the above-mentioned temperature-responsive absorbing metamaterial is as follows:

[0117] 1) Fabrication and assembly of the absorbing substrate, absorbing prism, and absorbing layer:

[0118] a) Polyethylene glycol with a number average molecular weight of 800 g / mol was dried and dehydrated at 120 °C for 0.5 h. Then, polyethylene glycol, isophorone diisocyanate, hydroxyethyl disulfide and dibutyltin dilaurate were dispersed in tetrahydrofuran and stirred at 60 °C for 3 h under a nitrogen atmosphere. Hydroxyethyl acrylate was then added and stirred for another 3 h. The molar ratio of polyethylene glycol, isophorone diisocyanate, hydroxyethyl disulfide and hydroxyethyl acrylate was 1:1.8:0.4:0.6. The amount of dibutyltin dilaurate was 1.8% of the mass of polyethylene glycol. The mixture was then vacuum dried at room temperature for 36 h to obtain polyurethane acrylate.

[0119] b) Polyurethane acrylate, hydroxyethyl acrylate, iron oxide powder (median particle size of 5 μm) and ethyl 2,4,6-trimethylbenzoylphenylphosphine were mixed and stirred evenly. The mass ratio of polyurethane acrylate, hydroxyethyl acrylate, iron oxide powder and ethyl 2,4,6-trimethylbenzoylphenylphosphine was 1:1:6:0.05 to obtain DLP printing paste.

[0120] c) A DLP printer was used to print the microwave absorbing substrate, microwave absorbing prism, and microwave absorbing layer using DLP printing paste. The printing parameters were as follows: bottom layer exposure time was 100s, model exposure time was 80s, slice thickness was 20μm, ultraviolet wavelength was 405nm, and light intensity was 9000μW·cm. -2 Then, DLP printing paste is coated on the surface of the absorbing substrate and the side of the absorbing prism before assembly. Finally, it is placed at 80℃ for 12 hours to achieve the connection between the absorbing prism, the absorbing substrate, and the absorbing layer.

[0121] 2) Preparation of the liquid crystal elastomer layer:

[0122] i) Dissolve 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene, 2,2'-(1,2-ethylenedioxy)bis(ethanediol)diethylthiol and dipropylamine in dichloromethane. The molar ratio of 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene to 2,2'-(1,2-ethylenedioxy)bis(ethanediol)diethylthiol is 1:1.2. The amount of dipropylamine used is 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene to 2,2'-(1,2-ethylenedioxy)bis(ethanediol)diethylthiol. 2% of the mass of 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene was added and stirred at room temperature for 12 h. Then, ethyl 2,4,6-trimethylbenzoylphenylphosphinate was added and stirred until homogeneous. The amount of ethyl 2,4,6-trimethylbenzoylphenylphosphinate was 1.5% of the mass of 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene was added and stirred until homogeneous. The mixture was then dried under vacuum at 80 °C for 24 h to obtain the liquid crystal elastomer prepolymer.

[0123] ii) A liquid crystal elastomer layer was printed on the surface of the microwave absorbing layer using a DIW printer with a liquid crystal elastomer prepolymer (preheated at 70°C for 30 minutes before printing). The printing parameters were as follows: needle inner diameter of 1000 μm and dispensing speed of 1 mm·s. -1 The printing pressure was 400 kPa, the printing temperature was 70℃, the ultraviolet light wavelength was 405 nm, and the light intensity was 10000 μW·cm. -2 The distance between the needle and the printing substrate is 250μm. The printing path is a continuous serpentine trajectory, which consists of multiple parallel line segments and turning segments connecting their ends. It fills the printing area in a continuous manner to obtain a temperature-responsive microwave absorbing metamaterial.

[0124] Comparative Example 1:

[0125] A microwave absorbing material, which has a flat plate structure and a thickness of 4.1 mm.

[0126] The preparation method of the above-mentioned microwave absorbing material is as follows:

[0127] a) Polyethylene glycol with a number average molecular weight of 1000 g / mol was dried and dehydrated at 120 °C for 0.5 h. Then, polyethylene glycol, isophorone diisocyanate, hydroxyethyl disulfide and dibutyltin dilaurate were dispersed in tetrahydrofuran and stirred at 60 °C for 3 h under a nitrogen atmosphere. Hydroxyethyl acrylate was then added and stirred for another 3 h. The molar ratio of polyethylene glycol, isophorone diisocyanate, hydroxyethyl disulfide and hydroxyethyl acrylate was 1:1.6:0.4:0.4. The amount of dibutyltin dilaurate was 1.5% of the mass of polyethylene glycol. The mixture was then vacuum dried at room temperature for 48 h to obtain polyurethane acrylate.

[0128] b) Polyurethane acrylate, hydroxyethyl acrylate, iron-based nanocrystalline powder (median particle size of 4 μm) and ethyl 2,4,6-trimethylbenzoylphenylphosphinate were mixed and stirred evenly. The mass ratio of polyurethane acrylate, hydroxyethyl acrylate, iron-based nanocrystalline powder and ethyl 2,4,6-trimethylbenzoylphenylphosphinate was 1:1:6:0.05 to obtain DLP printing slurry.

[0129] c) A flatbed structure was printed using a DLP printer with DLP printing paste. The printing parameters were as follows: bottom layer exposure time was 100s, model exposure time was 60s, slice thickness was 25μm, ultraviolet wavelength was 405nm, and light intensity was 7000μW·cm. -2 Thus, a microwave absorbing material is obtained.

[0130] Comparative Example 2:

[0131] An absorbing material, which is modified from the temperature-responsive absorbing metamaterial of Example 1 as follows: the absorbing-thermal-response sheet is modified to an absorbing sheet (i.e., the liquid crystal elastomer layer is removed).

[0132] The preparation method of the above-mentioned microwave absorbing material is as follows:

[0133] a) Polyethylene glycol with a number average molecular weight of 1000 g / mol was dried and dehydrated at 120 °C for 0.5 h. Then, polyethylene glycol, isophorone diisocyanate, hydroxyethyl disulfide and dibutyltin dilaurate were dispersed in tetrahydrofuran and stirred at 60 °C for 3 h under a nitrogen atmosphere. Hydroxyethyl acrylate was then added and stirred for another 3 h. The molar ratio of polyethylene glycol, isophorone diisocyanate, hydroxyethyl disulfide and hydroxyethyl acrylate was 1:1.6:0.4:0.4. The amount of dibutyltin dilaurate was 1.5% of the mass of polyethylene glycol. The mixture was then vacuum dried at room temperature for 48 h to obtain polyurethane acrylate.

[0134] b) Polyurethane acrylate, hydroxyethyl acrylate, iron-based nanocrystal powder (median particle size of 4 μm) and ethyl 2,4,6-trimethylbenzoylphenylphosphinate were mixed and stirred evenly. The mass ratio of polyurethane acrylate, hydroxyethyl acrylate, iron-based nanocrystal powder and ethyl 2,4,6-trimethylbenzoylphenylphosphinate was 1:1:6:0.05 to obtain DLP printing paste.

[0135] c) A DLP printer was used to print the microwave absorbing substrate, microwave absorbing prism, and microwave absorbing layer using DLP printing paste. The printing parameters were as follows: bottom layer exposure time was 100s, model exposure time was 60s, slice thickness was 25μm, ultraviolet wavelength was 405nm, and light intensity was 7000μW·cm. -2Then, DLP printing paste is coated on the surface of the absorbing substrate and the side of the absorbing prism, and then assembled. Finally, it is placed at 80℃ for 12 hours to achieve the connection between the absorbing prism, the absorbing substrate and the absorbing layer, thus obtaining the absorbing material.

[0136] Performance testing:

[0137] 1) The reflection loss-frequency relationship curves of the temperature-response absorbing metamaterial of Example 1 at different temperatures are shown below. Figure 4 As shown.

[0138] Depend on Figure 4 It can be seen that as the temperature increases from 25℃ to 90℃, the reflection loss curve of the temperature-responsive absorbing metamaterial expands from low-frequency absorption to high-frequency absorption, and the effective absorption bandwidth (reflection loss <-10dB) expands from 3.0GHz to 14.7GHz, which can realize temperature-responsive controllable broadband absorption.

[0139] 2) The reflection loss-frequency relationship curves of the temperature-responsive absorbing metamaterial of Example 1 for transverse microwaves at different incident angles at 90℃ are shown below. Figure 5 As shown.

[0140] Depend on Figure 5 It can be seen that as the incident angle of microwaves increases, the effective absorption bandwidth of the temperature-responsive absorbing metamaterial gradually decreases, but it still has excellent absorption performance in the incident angle range of 0° to 45°.

[0141] 3) The reflection loss-frequency relationship curves of the temperature-response absorbing metamaterials of Examples 1-5 and the absorbing materials of Comparative Examples 1-2 at 90℃ are shown below. Figure 6 As shown.

[0142] Depend on Figure 6 It can be seen that when the temperature is 90℃, the temperature-responsive absorbing metamaterials of Examples 1 to 5 have significantly improved absorbing performance and significantly increased effective absorption bandwidth compared with the absorbing materials of Comparative Examples 1 to 2.

[0143] 4) The temperature response performance test results of the flower-shaped structural unit in the temperature-responsive absorbing metamaterial of Example 3 are as follows: Figure 7 As shown.

[0144] Depend on Figure 7 It can be seen that the flower-like structural units in temperature-responsive absorbing metamaterials can indeed change their morphology (the degree of closure of the flower-like structural units) with temperature changes.

[0145] 5) The effective absorption bandwidth test results of the temperature-responsive absorbing metamaterials of Examples 1-5 and the absorbing materials of Comparative Examples 1-2 at different temperatures are shown in the table below:

[0146] Table 1. Test results of effective absorption bandwidth of temperature-responsive absorbing metamaterials and absorbing materials at different temperatures.

[0147]

[0148] Note: The absorption performance was calculated using the CST Studio Suite simulation platform based on finite integration technology. The electromagnetic response characteristics of the temperature-responsive absorbing metamaterial were numerically simulated, and structural design and parameter optimization were carried out. In the simulation settings, the unit cell method was adopted, and the simulation calculation was performed on only one basic structural unit of the temperature-responsive absorbing metamaterial. This method can significantly reduce computational complexity and improve computational efficiency. By applying periodic boundary conditions (PBC), an infinitely large temperature-responsive absorbing metamaterial absorbing array was simulated. For numerical solution, the frequency domain finite element method was selected, the boundary type was set to unit periodic boundary, and the excitation method was Floquet port.

[0149] Depend on Figure 4 , Figure 6 As shown in Table 1:

[0150] a) At room temperature, the flower-like structural units of the temperature-responsive absorbing metamaterials in Examples 1-5 are in an expanded state, similar to a flat plate structure, thus exhibiting poor absorption performance, concentrated in low-frequency absorption. As the temperature rises, the flower-like structural units close, revealing a distinct flower-like superstructure feature, which enhances the multiple reflections and scattering of microwaves within the structure. The absorption performance of the temperature-responsive absorbing metamaterials in Examples 1-5 is significantly improved, with an effective absorption bandwidth (reflection loss <-10dB) reaching 13.4GHz to 14.7GHz at 90℃, representing an increase of over 300% compared to the room temperature state. Therefore, by controlling changes in ambient temperature, the absorption performance of the temperature-responsive absorbing metamaterials of this invention can be controlled in real time, thereby addressing complex and variable electromagnetic absorption application environments.

[0151] b) The absorbing material of Comparative Example 1 has a planar structure, and its performance is limited to single-peak absorption caused by quarter-wavelength interference, with an absorption bandwidth of only 1.9 GHz. The absorbing material of Comparative Example 2 has the same structure as the temperature-responsive absorbing metamaterial of Example 1, but it does not have a temperature-responsive unit (liquid crystal elastomer layer). After heating, it cannot form a closed flower-like superstructure. Therefore, the absorbing performance of the material remains unchanged with temperature changes, and its effective absorption bandwidth is maintained at 3.0 GHz. It can be seen that, compared with the absorbing materials of Comparative Examples 1 to 2, the temperature-responsive absorbing metamaterials of Examples 1 to 5 contain flower-like superstructures that can be formed by heating, which significantly improve the absorbing performance of the material.

[0152] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A temperature responsive metamaterial, characterized in that, The composition comprises a wave-absorbing base and a flower-shaped structure unit; the composition of the flower-shaped structure unit comprises a wave-absorbing right prism and a wave-absorbing-thermal response sheet; the bottom surface of the wave-absorbing right prism is connected with the wave-absorbing base; any side surface of the wave-absorbing right prism is connected with the wave-absorbing-thermal response sheet; the composition of the wave-absorbing-thermal response sheet comprises a wave-absorbing layer and a liquid crystal elastomer layer; the compositions of the wave-absorbing base, the wave-absorbing right prism and the wave-absorbing layer all comprise polyurethane acrylate containing dynamic disulfide bond and soft magnetic powder.

2. The temperature-responsive metamaterial absorber of claim 1, wherein: The number of the bottom edges of the wave-absorbing right prism is 3-12, the circumscribed circle radius of the bottom surface is 3.0 mm-10.0 mm, and the length of the side edge is 0.5 mm-2.5 mm.

3. The temperature-responsive metamaterial absorber of claim 1, wherein: The wave-absorbing-thermal response sheet is in the shape of a rectangle, the short side of the rectangle is connected with the side surface of the wave-absorbing right prism, and the length of the long side of the rectangle is 5.0 mm-25.0 mm.

4. The temperature-responsive metamaterial absorber of claim 1, wherein: The thickness of the wave-absorbing layer is 0.5 mm-2.5 mm, and the thickness of the liquid crystal elastomer layer is 0.2 mm-1.0 mm.

5. The temperature-responsive metamaterial of any one of claims 1-4, wherein: The mass ratio of polyurethane acrylate containing dynamic disulfide bond to soft magnetic powder in the wave-absorbing base is 1:0.5-4.0, the mass ratio of polyurethane acrylate containing dynamic disulfide bond to soft magnetic powder in the wave-absorbing right prism is 1:0.5-4.0, the mass ratio of polyurethane acrylate containing dynamic disulfide bond to soft magnetic powder in the wave-absorbing layer is 1:0.5-4.0, and the soft magnetic powder is at least one of carbonyl iron powder, iron-nickel alloy powder, iron-cobalt alloy powder, iron-silicon-aluminum powder, iron-based nanocrystalline powder and ferroferric oxide powder.

6. The temperature-responsive metamaterial of any one of claims 1-4, wherein: The raw materials for preparing the polyurethane acrylate containing dynamic disulfide bond comprise polyethylene glycol, isocyanate, hydroxyl-terminated disulfide and hydroxy acrylate; the molar ratio of the polyethylene glycol, isocyanate, hydroxyl-terminated disulfide and hydroxy acrylate is 1:1.2-2.6:0.2-0.8:0.2-1.0; the number average molecular weight of the polyethylene glycol is 500 g / mol-5000 g / mol; the isocyanate is at least one of toluene diisocyanate, isophorone diisocyanate and diphenylmethane diisocyanate; the hydroxyl-terminated disulfide is at least one of hydroxyethyl disulfide and hydroxypropyl disulfide; and the hydroxy acrylate is at least one of hydroxypropyl acrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate and hydroxypropyl methacrylate.

7. The temperature-responsive metamaterial of any one of claims 1-4, wherein: The liquid crystal elastomer layer comprises a liquid crystal elastomer formed by copolymerization of 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene and 2,2'-(1,2-ethylenedioxy)bisethanethiol; the molar ratio of the 1,4-bis[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene and 2,2'-(1,2-ethylenedioxy)bisethanethiol is 1:1.0-1.5; the molecular chains of the liquid crystal elastomer are arranged in alignment, and the arrangement direction is parallel to the long side of the wave-absorbing-thermal response sheet.

8. A method for preparing the temperature-responsive metamaterial of any one of claims 1-7, wherein, The method comprises the following steps: 1) The wave-absorbing base, the wave-absorbing right prism and the wave-absorbing layer are printed by using digital light processing printing technology, then the printed paste is coated on the surface of the wave-absorbing base and the side of the wave-absorbing right prism, and the wave-absorbing right prism is assembled with the wave-absorbing base and the wave-absorbing layer, and then heat curing is performed to realize the connection of the wave-absorbing right prism with the wave-absorbing base and the wave-absorbing layer; 2) The liquid crystal elastomer layer is printed on the surface of the wave-absorbing layer by using direct ink writing technology through photocuring printing, and a temperature-responsive wave-absorbing metamaterial is obtained.

9. An electromagnetic shielding device, characterized by The temperature-responsive wave-absorbing metamaterial according to any one of claims 1-7.

10. Application of the temperature-responsive wave-absorbing metamaterial according to any one of claims 1-7 in the field of 5G / 6G communication, the field of consumer electronics or the field of new energy vehicles.

Images