An electrically controllable multi-spectrum compatible smart camouflage device

Abstract

The application relates to an electrically controllable multi-spectrum compatible intelligent camouflage device, belonging to the technical field of intelligent camouflage. The multi-spectrum compatible intelligent camouflage device comprises a flexible transparent tunable wave-absorbing layer, an integrated bionic color-changing layer and a flexible metal reflecting layer which are sequentially arranged, the flexible transparent tunable wave-absorbing layer is a main function layer for realizing electric tuning electromagnetic wave absorption of the device, and comprises a transparent flexible medium layer, a transparent resonance working layer located above the transparent flexible medium layer and a transparent multifunctional conductive layer located below the transparent flexible medium layer. The multi-spectrum compatible intelligent camouflage device can change optical characteristics to realize color change according to changes of environment, tasks and the like; has high spectral characteristics similar to typical ground background; can actively adjust radar reflection characteristics; the three characteristics are not interfered with each other; the compatible integration of the three stealth camouflage characteristics is realized; and the target is reduced to be detected and identified, and the stealth camouflage capability of a ground unit is obviously improved.

Description

Technical Field

[0001] This invention belongs to the field of intelligent camouflage technology, specifically relating to an electrically adjustable multi-spectrum compatible intelligent camouflage device. Background Technology

[0002] In recent years, reconnaissance and detection technologies have developed rapidly. The operating bands of high-altitude reconnaissance platforms now cover the entire radar band, from visible / near-infrared light, which places extremely high demands on stealth protection performance. While camouflage nets and coatings, widely used for stealth camouflage, can provide protection for ground units in a single environment, their stealth performance will be significantly reduced when location, time, and other factors change.

[0003] Typically, the optical characteristics of ground units differ significantly from the background depending on the environment. Therefore, to achieve stealth effectiveness in multiple scenarios, the optical characteristics of ground units should be able to automatically adjust to changes in the combat environment. Meanwhile, hyperspectral detection technology covers a reconnaissance spectrum ranging from 0.4 to 2.5 μm. This type of detection technology combines the advantages of spectral analysis and imaging remote sensing, and can detect and identify targets by detecting differences in the inherent spectral characteristics of the target and the background. Therefore, to achieve better stealth effects, in addition to the similarity between the optical characteristics of ground units and the background, the hyperspectral characteristics also need to be similar. Furthermore, current high technologies such as synthetic aperture radar have become increasingly sophisticated and widely used. As an active detection method operating in the microwave band, it has all-weather, all-day operation capabilities and a certain ability to penetrate vegetation and the ground surface. Therefore, to achieve more comprehensive stealth effects, ground units need to be able to actively adjust radar reflection peaks and frequencies to cope with detection by multi-band radar network systems.

[0004] Existing stealth and camouflage devices can individually achieve color changes, simulate the hyperspectral characteristics of typical ground backgrounds (vegetation), and actively adjust radar wave absorption peaks and frequencies. However, they cannot achieve compatibility and intelligent control of these methods. Therefore, there is an urgent need for an electrically controlled stealth and camouflage device that can change its optical characteristics according to changes in environment and mission conditions, possess hyperspectral characteristics similar to typical ground backgrounds (vegetation), and actively adjust radar reflection characteristics. This would reduce the likelihood of target detection and significantly improve the camouflage capabilities of ground units. Summary of the Invention

[0005] The purpose of this invention is to address the problems existing in the background technology by proposing an electrically tunable multi-spectral compatible intelligent camouflage device. This multi-spectral compatible intelligent camouflage device can change color by altering the applied voltage to simulate young and withered leaves, possesses hyperspectral characteristics similar to plants, and can also actively adjust radar reflection characteristics by changing the voltage.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] An electrically tunable multi-spectrum compatible smart camouflage device includes a flexible transparent tunable absorbing layer, an integrated biomimetic color-changing layer, and a flexible metal reflective layer arranged sequentially from top to bottom.

[0008] The flexible transparent tunable absorbing layer is the main functional layer for the device to achieve electrically tunable electromagnetic wave absorption. It includes a transparent flexible dielectric layer, a transparent resonant working layer above the transparent flexible dielectric layer, and a transparent multifunctional conductive layer below the transparent flexible dielectric layer.

[0009] The transparent resonant working layer is a patterned conductive grid with diodes welded on it. The patterned conductive grid is composed of an array of unit structures. Each unit structure consists of a central quadrilateral conductive region and four elongated conductive regions parallel to the four sides of the quadrilateral. The length of the long side of each elongated conductive region is equal to the length of the adjacent side of the quadrilateral conductive region. The four elongated regions are connected to the central quadrilateral conductive region by four diodes. The quadrilateral conductive region is uniformly divided into multiple cells, and the conductive region in the center of each cell is removed to form a non-conductive region. The four elongated conductive regions are also divided into multiple cells, and the conductive region in the center of each cell is removed to form a non-conductive region. The side length of the unit structure is not less than 30 mm, the side length of the cell is 0.5–3 μm, and the area of ​​the conductive region of the transparent resonant working layer does not exceed 75% of the area of ​​the transparent flexible dielectric layer.

[0010] The transparent multifunctional conductive layer is composed of cells arranged in an array, with the central conductive region removed to form a non-conductive region. The side length of each cell does not exceed 3 μm. The area of ​​the conductive region of the transparent multifunctional conductive layer does not exceed 50% of the area of ​​the transparent flexible dielectric layer.

[0011] Preferably, the side length of the quadrilateral in the unit structure is not less than 20mm.

[0012] Furthermore, the resistance of the conductive material in the transparent resonant working layer is not less than 10Ω / hole, and the resistance of the conductive material in the transparent multifunctional conductive layer is not less than 5Ω / hole.

[0013] Furthermore, the conductive material of the transparent resonant working layer is ITO, FTO, etc., and the thickness is 0.01 to 25 μm.

[0014] Furthermore, the conductive material of the transparent multifunctional conductive layer is ITO, FTO, etc., and the thickness is 0.01 to 25 μm.

[0015] Furthermore, the transparent flexible dielectric layer is made of PET, PVDF, PDMS, etc.; the thickness of the transparent flexible dielectric layer is 0.5-5mm.

[0016] Furthermore, the integrated biomimetic color-changing layer is the main functional layer for achieving electrochromism and simulating the hyperspectral characteristics of plants in this device, and is prepared using the following steps:

[0017] Step 1: Preparation of transparent regenerated cellulose film:

[0018] 1 wt% to 5 wt% of cotton linters are dissolved in a mixed solvent of dimethyl sulfoxide and 1-ethyl-3-methylimidazolium acetate to obtain a mixture, wherein the mass ratio of dimethyl sulfoxide to 1-ethyl-3-methylimidazolium acetate is (1 to 4): 1; then the mixture is cast into a polytetrafluoroethylene groove and then immersed in anhydrous ethanol to regenerate the dissolved cellulose and form a transparent regenerated cellulose film with a thickness of 0.01 to 1 mm;

[0019] Step 2: Prepare the integrated electrochromic gel:

[0020] The sol is added to deionized water and stirred until the sol is completely dissolved. Then, the electrochromic material and electrolyte are added, and stirring is continued to form an integrated electrochromic gel. The mass percentages of the sol, electrochromic material, electrolyte, and deionized water are as follows: 64wt%–84wt% deionized water, 10wt%–20wt% sol, 4wt%–20wt% electrolyte, and 2wt%–6wt% electrochromic material.

[0021] In step 2, the sol is polyvinyl alcohol, polymethyl methacrylate, etc.; the electrolyte is lithium salt, sodium salt, etc.; and the electrochromic material is an electrochromic material that can change between colorless or yellow and green, including viologen derivatives, triphenylamine derivatives, etc.

[0022] Furthermore, the flexible metal reflective layer is an auxiliary functional layer for the device to achieve electrochromic properties, simulate plant hyperspectral characteristics, and electrically tuned electromagnetic wave absorption. It includes a flexible substrate and a conductive metal layer formed on the flexible substrate. The flexible substrate is made of nylon or similar materials and has a thickness of 0.05–5 mm; the conductive metal layer is one or more of gold and copper and has a thickness of 0.05–0.5 μm.

[0023] Furthermore, the fabrication process of the transparent resonant working layer is as follows: First, a conductive layer is deposited on a transparent flexible dielectric layer using physical deposition; then, a patterned conductive network is etched; finally, a diode is soldered.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] The present invention provides an electrically adjustable multi-spectral compatible intelligent camouflage device that can change its optical characteristics to achieve color change according to changes in environment, mission and other conditions; it has hyperspectral characteristics similar to typical ground background (vegetation); at the same time, it can actively adjust radar reflection characteristics, and the above three characteristics do not interfere with each other, realizing the compatibility and integration of the above three stealth camouflage characteristics, thereby reducing the target being detected and identified, and significantly improving the stealth camouflage capability of ground units. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of an electrically tunable multi-spectrum compatible smart camouflage device provided by the present invention;

[0027] Figure 2 This is a schematic diagram of the unit cell structure in the transparent resonant operating layer;

[0028] Figure 3 A schematic diagram illustrating the color change principle of an electrically tunable, multi-spectrum compatible intelligent camouflage device provided by this invention;

[0029] Figure 4 A comparison of the reflectance spectrum of an electrically tunable multi-spectral compatible smart camouflage device provided by the present invention with that of a leaf (yellow ginkgo);

[0030] Figure 5 This invention provides a verification model of the electromagnetic wave absorption principle of an electrically tunable multi-spectrum compatible smart camouflage device and a simulated electromagnetic wave absorption curve. Detailed Implementation

[0031] The implementation principle and solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0032] like Figure 1 As shown in the diagram, this invention provides a schematic of a multi-spectral compatible intelligent camouflage device that can be electrically controlled. The device includes, from top to bottom, a flexible transparent tunable absorbing layer, an integrated biomimetic color-changing layer, and a flexible metal reflective layer. Electrodes 1 and 2 are connected to a transparent resonant working layer within the flexible transparent tunable absorbing layer, electrode 3 is connected to a transparent multifunctional conductive layer within the flexible transparent tunable absorbing layer, and electrode 4 is connected to a conductive metal layer within the flexible metal reflective layer. Applying a voltage between electrodes 1 and 2 enables electrically tunable electromagnetic wave absorption, while applying a voltage between electrodes 3 and 4 enables electrochromism. The integrated biomimetic color-changing layer, combined with the flexible metal reflective layer, achieves hyperspectral characteristics similar to those of plants.

[0033] like Figure 2The diagram shows a schematic of the unit structure in the transparent resonant working layer. The unit structure consists of a central quadrilateral conductive region and four elongated conductive regions parallel to the four sides of the quadrilateral. The length of the elongated conductive regions is equal to the length of the adjacent sides of the quadrilateral conductive regions. Four diodes connect the four elongated regions to the central quadrilateral conductive region. The quadrilateral conductive region is uniformly divided into multiple cells, and the conductive region at the center of each cell is removed to form a non-conductive region. Similarly, the four elongated conductive regions are divided into multiple cells, and the conductive region at the center of each cell is removed to form a non-conductive region. The side length of the unit structure is not less than 30 mm, the side length of the cell is 0.5–3 μm, and the area of ​​the conductive region in the transparent resonant working layer does not exceed 75% of the area of ​​the transparent flexible dielectric layer. To achieve both electrochromic and electrically tunable electromagnetic wave absorption while simultaneously realizing hyperspectral characteristics similar to those of plants, this invention designs periodic structural patterns for the transparent resonant working layer and the transparent multifunctional conductive layer in the flexible transparent tunable absorbing layer based on the principle of frequency-selective surfaces. To ensure the transparent, flexible, tunable absorbing layer can absorb radar waves while maximizing the transmission of near-infrared light in the 850–2500 nm range, a periodic composite structural pattern at the wavelength level close to the resonant frequency of radar and near-infrared waves is employed. Similarly, the transparent multifunctional conductive layer, while transmitting near-infrared light in the 850–2500 nm range, maximizes radar wave reflection, also employing a periodic structural pattern at the wavelength level of the near-infrared wave resonant frequency. Furthermore, the conductive material of the transparent resonant layer has a resistance of at least 10 Ω / hole, and the conductive material of the transparent multifunctional conductive layer has a resistance of at least 5 Ω / hole. The selection of these resistance values ​​balances the needs of both radar absorption and electrochromic properties.

[0034] like Figure 3 The diagram shown illustrates the color-changing principle of an electrically tunable multi-spectrum compatible intelligent camouflage device provided by this invention. The specific principle of simulating withered leaves (yellow) and tender leaves (green) by changing the voltage between electrodes 3 and 4 is as follows: Yellow (withered leaves) is achieved by mixing a yellow or colorless electrochromic active material with a yellow flexible metal reflective layer; green (tender leaves) is achieved by the electrochromic molecules in the integrated biomimetic color-changing layer turning green on the flexible metal reflective layer under voltage, thus covering the underlying color. Simultaneously, a transparent flexible tunable absorbing layer, a transparent flexible dielectric layer, and a transparent regenerated cellulose film with high visible light transmittance are required to ensure the color remains unaffected.

[0035] like Figure 4The image shows a comparison between the electrically tunable multi-spectral compatible intelligent camouflage device provided by this invention and the reflectance spectrum of a simulated plant leaf (yellow ginkgo). The reflectance spectrum of the simulated plant leaf in the 350–850 nm range is simulated by changing the applied voltage to alter the color, mimicking the green and yellow spectra. The near-infrared reflectance plateau in the 850–1150 nm range is primarily achieved by providing a horizontal near-infrared reflectance through the transparent regenerated cellulose film in the integrated biomimetic color-changing layer, and by utilizing the high reflectance of the underlying flexible metal reflective layer to enhance the overall reflectance of the device. The water absorption peaks at 1400 nm and 1800 nm are achieved through the water retention in the regenerated cellulose film within the integrated biomimetic color-changing layer and the water absorption effect of hygroscopic components such as lithium salts in the electrolyte. Simultaneously, high near-infrared transmittance is required from the patterned transparent resonant working layer and the transparent multifunctional conductive layer in the transparent flexible tunable absorbing layer, as well as the high near-infrared transmittance of the transparent flexible dielectric layer, to ensure that the transparent flexible tunable absorbing layer does not interfere with the simulation of the plant reflectance spectrum.

[0036] like Figure 5 The diagram shows a verification model of the electrically tunable electromagnetic wave absorption principle of a multi-spectrum compatible intelligent camouflage device provided by this invention, along with the simulated electromagnetic wave absorption curve. Electromagnetic waves propagate to a flexible, transparent, tunable absorbing layer. The coupling between the transparent resonant working layer and the transparent multifunctional conductive layer generates resonant loss, achieving radar wave absorption. A metal reflective layer ensures complete reflection of the electromagnetic waves with no transmission. Simultaneously, by changing the reverse bias voltage of the varactor diode on the transparent resonant layer, the impedance matching of the transparent resonant working layer can be altered, allowing continuous tuning of the absorption band.

[0037] Example

[0038] An electrically tunable, multi-spectral compatible smart camouflage device, the specific fabrication process of which is as follows:

[0039] Step 1. Fabrication of a flexible, transparent, tunable absorbing layer:

[0040] 1.1 Fabrication of the transparent resonant working layer

[0041] A 5μm thick ITO film was deposited on the surface of a 2.5mm thick PET (transparent flexible dielectric layer) using magnetron sputtering. The designed transparent resonant working layer patterned conductive grid was etched on the ITO film using laser etching to remove excess ITO. Then, a micro diode, model SMV2019-079LF, was welded onto the etched conductive layer surface. The transparent resonant working layer is a patterned conductive grid with diodes welded on it. The patterned conductive grid consists of an array of unit structures with a side length of 30mm. Each unit structure consists of a central square ITO conductive region with a side length of 20mm and four elongated conductive regions parallel to the four sides of the square ITO. The elongated conductive regions are rectangular ITO patterns with a long side length of 20mm and a short side length of 4mm. The four elongated regions are connected to the central square conductive region by four diodes with a length of 1mm and a width of 0.25mm. The square ITO conductive region is uniformly divided into multiple square cells with a side length of 2μm. The square conductive region with a side length of 1.73μm at the center of each cell is removed to form a non-conductive region. Similarly, the four elongated conductive regions are divided into multiple square cells with a side length of 2μm. The square conductive region with a side length of 1.73μm at the center of each cell is removed to form a non-conductive region.

[0042] 1.2 Preparation of transparent multifunctional conductive layer

[0043] A 0.5 μm thick ITO film was deposited on the lower surface of a 2.5 mm thick PET (transparent flexible dielectric layer) using magnetron sputtering. The designed transparent multifunctional conductive layer pattern was then etched onto the ITO film using laser etching to remove excess ITO. The transparent multifunctional conductive layer consists of arrayed cells with a central conductive region removed to form non-conductive regions. Each cell is square with a side length of 2 μm, and the non-conductive regions are squares with a side length of 1.4 μm.

[0044] Step 2. Preparation of the integrated biomimetic color-changing layer:

[0045] 2.1 Preparation of transparent regenerated cellulose film

[0046] 0.15g of cotton linters were swollen in 6.5g of dimethyl sulfoxide for 3 hours. After the cotton linters were completely swollen, 3.5g of 1-ethyl-3-methylimidazolium acetate was added and stirred thoroughly for 5 hours to obtain a mixture. The mixture was then cast into a polytetrafluoroethylene groove with a depth of 50μm and immersed in anhydrous ethanol for 12 hours to regenerate the dissolved cellulose and form a transparent regenerated cellulose film with a thickness of 0.35mm.

[0047] 2.2 Preparation of integrated electrochromic gel

[0048] 10g PVA was added to a mixed solvent of 80mL deionized water and 10mL dimethyl sulfoxide, and stirred for 3h in an oil bath at 85℃. After all PVA was dissolved, it was taken out and allowed to stand for 6h to defoam, thus obtaining PVA gel.

[0049] Under stirring conditions, 0.28 g of 1-benzyl-1'-(p-cyanophenyl)-4,4'-bipyridine dibromide, 0.12 g of 1,1'-ferrocene dimethyl alcohol and 0.53 g of lithium perchlorate were added to 10 g of the above gel. After stirring evenly for 6 h, the gel was taken out and allowed to stand for 12 h to defoam, thus obtaining an integrated electrochromic gel.

[0050] Step 3. Fabrication of the flexible metal reflective layer:

[0051] Vacuum electron beam deposition was employed, using a 200 μm thick flexible nylon film as the substrate and a high-purity gold target as the target material. A gold film with a thickness of 300–350 nm was deposited on the nylon film. The vacuum level of the vacuum chamber during the deposition process was less than 3 × 10⁻⁶. -3 The deposited gold film adhered firmly to the substrate without detachment, and the conductivity of the gold film obtained by four-probe testing was approximately 2.2 × 10⁻⁶. 7 Sm -1 .

[0052] Step 4. Device packaging:

[0053] The device is obtained by sequentially stacking the polyethylene film, the flexible transparent tunable absorbing layer prepared in step 1, the integrated biomimetic color-changing layer prepared in step 2, the flexible metal reflective layer prepared in step 3, and the polyethylene film, and then encapsulating them with the aid of a hot press.

Claims

1. An electrically controllable multi-spectrum compatible smart camouflage device, characterized in that, The flexible transparent tunable absorbing layer, the integrated bionic color-changing layer and the flexible metal reflecting layer are sequentially arranged from top to bottom. The flexible transparent tunable absorbing layer comprises a transparent flexible dielectric layer, a transparent resonant working layer located above the transparent flexible dielectric layer, and a transparent multifunctional conductive layer located below the transparent flexible dielectric layer. The first electrode and the second electrode are connected to the transparent resonant working layer in the flexible transparent tunable absorbing layer, the third electrode is connected to the transparent multifunctional conductive layer in the flexible transparent tunable absorbing layer, and the fourth electrode is connected to the conductive metal layer in the flexible metal reflecting layer; the voltage applied between the first electrode and the second electrode realizes electrically tunable electromagnetic wave absorption, and the voltage applied between the third electrode and the fourth electrode realizes electrochromism. The transparent resonant working layer is a patterned conductive grid with diodes welded, which is composed of an array of unit structures, each unit structure is composed of a quadrilateral conductive area in the middle and four long strip-shaped conductive areas parallel to the four sides of the quadrilateral, the long side length of the long strip-shaped conductive area is equal to the length of the adjacent side of the quadrilateral conductive area, and the four long strip-shaped conductive areas are connected to the quadrilateral conductive area in the middle through four diodes; the quadrilateral conductive area is evenly divided into a plurality of unit cells, and the conductive area at the center of each unit cell is removed to form a non-conductive area; each of the four long strip-shaped conductive areas is divided into a plurality of unit cells, and the conductive area at the center of each unit cell is removed to form a non-conductive area; wherein the side length of the unit structure is not less than 30 mm, the side length of the unit cell of the transparent resonant working layer is 0.5-3 μm, and the area of the conductive area of the transparent resonant working layer is not more than 75% of the area of the transparent flexible dielectric layer; The transparent multifunctional conductive layer is composed of an array of unit cells with a central conductive area removed to form a non-conductive area, and the side length of the unit cell of the transparent multifunctional conductive layer is not more than 3 μm; the area of the conductive area of the transparent multifunctional conductive layer is not more than 50% of the area of the transparent flexible dielectric layer; The integrated bionic color-changing layer is prepared by the following steps: Step 1, preparation of a transparent regenerated cellulose film: Dissolve 1 wt% to 5 wt% of cotton short fibers in a mixed solvent of dimethyl sulfoxide and 1-ethyl-3-methylimidazole acetate, to obtain a mixed solution, wherein the mass ratio of dimethyl sulfoxide to 1-ethyl-3-methylimidazole acetate is (1-4):1; then cast the mixed solution into a polytetrafluoroethylene groove, and then immerse it in anhydrous ethanol to regenerate the dissolved cellulose, thereby forming a transparent regenerated cellulose film with a thickness of 0.01-1 mm; Step 2, preparation of an integrated electrochromic gel: The sol is added into deionized water, stirred until the sol is completely dissolved, then the electrochromic material and electrolyte are added, and continue to stir to form an integrated electrochromic gel; wherein the mass percentage of the sol, the electrochromic material, the electrolyte and the deionized water is: 64 wt% to 84 wt% of deionized water, 10 wt% to 20 wt% of sol, 4 wt% to 20 wt% of electrolyte, and 2 wt% to 6 wt% of electrochromic material.

2. The electrically controllable multi-spectrum compatible smart camouflage device of claim 1, wherein, The length of the side of the quadrangle in the unit structure is not less than 20 mm.

3. The electrically controllable multi-spectrum compatible smart camouflage device of claim 1, wherein, The resistance of the conductive material of the transparent resonance working layer is not less than 10 Ω / square, and the resistance of the conductive material of the transparent multifunctional conductive layer is not less than 5 Ω / square.

4. The electrically controllable multi-spectrum compatible smart camouflage device of claim 1, wherein, The conductive material of the transparent resonance working layer is graphene, ITO or FTO, and the thickness is 0.01 to 25 μm.

5. The electrically controllable multi-spectrum compatible smart camouflage device of claim 1, wherein, The conductive material of the transparent multifunctional conductive layer is graphene, ITO or FTO, and the thickness is 0.01 to 25 μm.

6. The electrically controllable multi-spectrum compatible smart camouflage device of claim 1, wherein, The transparent flexible medium layer is PET, PVC, PE, PC, PP, PVDF or PDMS; and the thickness of the transparent flexible medium layer is 0.5 to 5 mm.

7. The electrically controllable multi-spectrum compatible smart camouflage device of claim 1, wherein, The sol in step 2 is polyvinyl alcohol or polymethyl methacrylate; the electrolyte is lithium salt or sodium salt; and the electrochromic material is an electrochromic material that can change between colorless or yellow and green.

8. The electrically controllable multi-spectrum compatible smart camouflage device of claim 1, wherein, The flexible metal reflection layer comprises a flexible substrate and a conductive metal layer formed on the flexible substrate; the flexible substrate is nylon, and the thickness is 0.05 to 5 mm; and the conductive metal layer is one or more of gold and copper, and the thickness is 0.05 to 0.5 μm.

Images