Flexible electrochromic biomimetic structure and method of making the same

Abstract

The application relates to the technical field of intelligent camouflage, and provides a flexible electrochromic bionic structure and a preparation method thereof, which comprises the following steps: preparing a reflective resonant cavity composed of a reflective metal layer and an electrochromic layer on a flexible microporous substrate. The reflective resonant cavity forms an initial camouflage color, then the optical constant of the electrochromic layer is changed by applying a voltage to change the camouflage color, visible light camouflage is realized, and the infrared emissivity is adjusted to eliminate / reduce the difference in infrared radiation characteristics between the target and the background, so that infrared camouflage is realized. Therefore, the electrochromic effect is improved.

Description

Technical Field

[0001] This invention relates to the field of intelligent camouflage technology, and in particular to a flexible electrochromic biomimetic structure and its preparation method. Background Technology

[0002] With the development of advanced reconnaissance technologies, the goal of major military powers in exploring and developing advanced camouflage technologies has become how to enable targets to survive "invisibly" on a "transparent battlefield." The ultimate goal of adaptive intelligent camouflage is to utilize advanced technologies to ensure that targets can always blend into their surroundings in terms of color, temperature, brightness, texture, and other characteristics.

[0003] Adaptive intelligent camouflage can be achieved in two ways: one is adaptive environmental characteristic mimicry camouflage, where the camouflaged target can autonomously respond and intelligently control and adjust its own photoelectric characteristics when the photoelectric characteristics of the battlefield background change, achieving a high degree of integration and matching with the photoelectric features of the background (or environment). The other way is adaptive deception camouflage, which displays the combat target as a non-combat target on the enemy's detection system, especially effective against deep learning-based detection methods.

[0004] Intelligent camouflage technology, which mimics environmental characteristics, aims to achieve intelligent camouflage by controlling the degree to which the target blends into the environmental background during different times of day and night, changes in environmental background, and different seasons. Low grass, tall grass, soil, and trees are four typical surface environments, with trees being the most important ground environmental background. Therefore, electrochromic biomimetic leaves can be used for intelligent camouflage of ground targets. Electrochromism is the phenomenon where materials reversibly change their color or optical properties through redox reactions under the influence of an applied electric field.

[0005] Currently, electrochromic technology is mainly used in automotive anti-glare rearview mirrors, smart dimming glass, and automatic light-controlling chemical goggles. However, there is no mature electrochromic solution in the field of smart camouflage, resulting in poor electrochromic performance. Summary of the Invention

[0006] This invention provides a flexible electrochromic biomimetic structure and its fabrication method to solve the problem of electrochromism. A reflective resonant cavity, consisting of a reflective metal layer and an electrochromic layer, is fabricated on a flexible microporous substrate. The reflective resonant cavity forms an initial camouflage color. Then, by applying a voltage to change the optical constant of the electrochromic layer, the camouflage color is altered, achieving visible light camouflage. Furthermore, infrared camouflage is achieved by adjusting the infrared emissivity to eliminate / reduce the difference in infrared radiation characteristics between the target and the background. Based on this, the effect of electrochromism is improved.

[0007] This invention provides a flexible electrochromic biomimetic structure, comprising:

[0008] The working electrode layer is used to switch camouflage reflection colors and adjust infrared emissivity;

[0009] The electrode layer is used to conduct ions and electrons, providing the working electrode layer with the ions required for the color-changing reaction, so as to maintain the charge balance of the electrochromic process;

[0010] The electrolyte layer provides interconnected active ion channels for the working electrode and the counter electrode layer, and isolates electron conduction.

[0011] The working electrode layer includes a reflective metal layer and an electrochromic layer, which together form a reflective resonant cavity to create an initial camouflage color. The difference in infrared radiation characteristics between the target and the background is eliminated / reduced by adjusting the infrared emissivity. The initial camouflage color is changed by altering the optical constant of the electrochromic layer through different voltage values.

[0012] In one embodiment, the reflective metal layer comprises any one of a single-layer metal, a multi-layer metal, or a metal alloy;

[0013] The electrochromic layer is made of inorganic electrochromic materials and / or organic electrochromic materials.

[0014] In one embodiment, the counter electrode layer is a single-layer metal electrode, or a composite electrode composed of a metal and an ion storage layer.

[0015] In one embodiment, the material of the electrolyte layer includes any one of liquid electrolyte, gel electrolyte, and solid electrolyte;

[0016] The liquid electrolyte is composed of carbonate-based organic solvents and lithium salts;

[0017] The gel electrolyte is composed of a polymer, an electrolyte salt, and a low-molecular-weight organic solvent;

[0018] The solid electrolyte includes any one of inorganic electrolytes and polymer electrolytes.

[0019] In one embodiment, the electrolyte layer uses a flexible microporous substrate as a carrier;

[0020] The flexible microporous substrate is used to provide a substrate for the working electrode layer and the counter electrode layer, and to provide a flow channel for the electrolyte.

[0021] In one embodiment, the flexible microporous substrate includes any one of a microporous filter membrane, a microporous flexible plastic membrane, and a track-etched membrane.

[0022] In one embodiment, the flexible electrochromic biomimetic structure further includes a first encapsulation protective layer and a second encapsulation protective layer;

[0023] The first and second encapsulation protective layers are used to protect the flexible electrochromic biomimetic structure;

[0024] The second encapsulation protective layer is also used to provide visible light and infrared radiation windows for the flexible electrochromic biomimetic structure.

[0025] In one embodiment, the first encapsulation protective layer and the second encapsulation protective layer are film products.

[0026] This invention also provides a method for preparing a flexible electrochromic biomimetic structure, comprising:

[0027] A gold Au reflective layer, a tungsten oxide WO3 electrochromic layer, a first Au counter electrode, a first gel electrolyte layer, and an encapsulation protective layer were prepared.

[0028] A flexible electrochromic biomimetic structure is prepared based on the Au reflective layer, the WO3 electrochromic layer, the first Au counter electrode, the first gel electrolyte layer, and the encapsulation protective layer.

[0029] In one embodiment, the method further includes:

[0030] Preparation of microporous polyimide films;

[0031] A second working electrode is prepared based on the microporous polyimide film, Au, WO3 and tungsten W;

[0032] Prepare a second Au counter electrode, a second gel electrolyte layer, and an encapsulation protective layer;

[0033] The flexible electrochromic biomimetic structure is prepared based on the second working electrode, the second Au counter electrode, the second gel electrolyte layer, and the encapsulation protective layer.

[0034] The flexible electrochromic biomimetic structure and its fabrication method provided by this invention involve creating a reflective resonant cavity composed of a reflective metal layer and an electrochromic layer on a flexible microporous substrate. The reflective resonant cavity forms an initial camouflage color, and then the optical constant of the electrochromic layer is changed by applying a voltage to alter the camouflage color, achieving visible light camouflage; and infrared camouflage is achieved by adjusting the infrared emissivity to eliminate / reduce the difference in infrared radiation characteristics between the target and the background. Based on this, the effect of electrochromism is improved. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of the flexible electrochromic biomimetic structure provided by the present invention;

[0037] Figure 2 This is one of the working mechanisms of the interference modulation type flexible electrochromic biomimetic leaf provided by the present invention;

[0038] Figure 3 This is a schematic diagram of the leaf-patterned metal mask provided by the present invention;

[0039] Figure 4 This is a schematic diagram of the reflectance spectrum of the biomimetic leaf before and after applying voltage, provided by the present invention;

[0040] Figure 5 This is the second working mechanism of the interference modulation type flexible electrochromic biomimetic leaf provided by the present invention. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0042] The following is combined Figures 1-5 The present invention describes the flexible electrochromic biomimetic structure and its preparation method.

[0043] Specifically, the present invention provides a flexible electrochromic biomimetic structure, with reference to Figure 1 , Figure 1 This is a schematic diagram of the flexible electrochromic biomimetic structure provided by the present invention.

[0044] The flexible electrochromic biomimetic structure provided in this embodiment of the invention includes:

[0045] The working electrode layer is used to switch camouflage reflection colors and adjust infrared emissivity;

[0046] The electrode layer is used to conduct ions and electrons, providing the working electrode layer with the ions required for the color-changing reaction, so as to maintain the charge balance of the electrochromic process;

[0047] The electrolyte layer provides interconnected active ion channels for the working electrode and the counter electrode layer, and isolates electron conduction.

[0048] The working electrode layer includes a reflective metal layer and an electrochromic layer, which together form a reflective resonant cavity to create an initial camouflage color. The optical constant of the electrochromic layer is changed by different voltage values ​​to alter the initial camouflage color. The difference in infrared radiation characteristics between the target and the background is eliminated / reduced by adjusting the infrared emissivity.

[0049] It should be noted that electrochromic biomimetic structures used for intelligent camouflage need to meet the basic camouflage requirements of visible light, near-infrared, and thermal infrared. For visible light camouflage, it is necessary to minimize or eliminate large-area color and brightness differences between the camouflaged target and the actual background; for near-infrared camouflage, it is necessary to reduce the difference in reflectance spectrum between the camouflaged target and the actual background; for thermal infrared camouflage, it is necessary to eliminate / reduce and blur the thermal infrared radiation difference between the target and the background in the mid- and far-infrared bands (such as the two atmospheric windows with wavelengths of 3–5 m and 8–14 m).

[0050] The flexible electrochromic biomimetic structure provided by this invention can be a flexible electrochromic biomimetic leaf, a flexible electrochromic biomimetic flower, a flexible electrochromic biomimetic stone, etc. The embodiments of this invention will be explained using a flexible electrochromic biomimetic leaf as an example.

[0051] The flexible electrochromic biomimetic structure is provided with a first encapsulation protective layer, a counter electrode layer, an electrolyte layer, a working electrode layer, and a second encapsulation protective layer from bottom to top.

[0052] The counter electrode layer is used to conduct ions and electrons, store ions, and provide the ions required for the color-changing reaction to the working electrode layer, so as to maintain the charge balance of the electrochromic process.

[0053] The electrolyte layer provides interconnected active ion channels for the working electrode and the counter electrode layer, while isolating electron conduction.

[0054] The working electrode layer is the main function of the flexible electrochromic biomimetic structure. It is used to intelligently switch camouflage reflection colors and reversibly adjust infrared emissivity.

[0055] The working electrode layer includes a reflective metal layer and an electrochromic layer arranged sequentially from bottom to top. The reflective metal layer and the electrochromic layer form a reflective resonant cavity, forming the initial camouflage color. Light is reflected back and forth on the top and bottom surfaces of the electrochromic layer. By enhancing or suppressing the reflection of some light, the initial camouflage color is changed. It can be understood that by applying a voltage to change the optical constants (refractive index n and extinction coefficient k) of the electrochromic layer, the working electrode can be changed to another camouflage color, thus achieving visible light camouflage. Furthermore, the difference in infrared radiation characteristics between the target and the background can be eliminated / reduced by adjusting the infrared emissivity, thereby achieving infrared camouflage.

[0056] For example, simulating fresh leaves (green) and withered leaves (yellow), assuming that the initial camouflage color of the flexible electrochromic bionic leaf is yellow, and that the yellow color can be changed to green by changing the applied voltage to achieve visible light camouflage; infrared camouflage can also be achieved by adjusting the infrared emissivity by changing the applied voltage.

[0057] The flexible electrochromic biomimetic structure provided in this invention forms a reflective resonant cavity through a reflective metal layer and an electrochromic layer, creating an initial camouflage color. Then, by applying a voltage to change the optical constant of the electrochromic layer, the camouflage color is altered, achieving visible light camouflage. Furthermore, by adjusting the infrared emissivity, the difference in infrared radiation characteristics between the target and the background is eliminated / reduced, thereby achieving infrared camouflage. Based on this, the effect of electrochromism is improved.

[0058] Furthermore, the reflective metal layer is a single-layer metal or a multi-layer metal; the electrochromic layer is made of inorganic electrochromic material products and / or organic electrochromic materials.

[0059] It should be noted that the metal reflective layer can be a single layer of metal or multiple layers of metal. For example, the material of the metal reflective layer is a non-reactive metal, including gold (Au), silver (Ag), copper (Cu), platinum (Pt), aluminum (Al), or titanium (Ti), as well as composite metals formed by multiple metals; the thickness of the metal reflective layer is above 20 nm, preferably 20–300 nm.

[0060] The electrochromic layer is made of inorganic electrochromic materials and / or organic electrochromic materials. Among them, inorganic electrochromic materials include tungsten oxide, nickel oxide, molybdenum oxide, vanadium oxide and their doped systems. The preparation methods of inorganic electrochromic materials can adopt thin film preparation processes such as thermal evaporation, magnetron sputtering, chemical vapor deposition, pulsed laser deposition, sol-gel method, hydrothermal method, electrochemical deposition, screen printing, and inkjet printing.

[0061] Organic electrochromic materials include polythiophene, polyaniline, polypyrrole, polycarbazole, violetin, Prussian blue and their derivatives; organic electrochromic materials can be prepared using thin film processes such as thermal evaporation, electrochemical deposition, screen printing, and inkjet printing.

[0062] The thickness of the electrochromic layer is 10–3000 nm, preferably 50–800 nm.

[0063] Furthermore, the counter electrode layer is a single-layer metal electrode, or a composite electrode composed of a metal and an ion storage layer.

[0064] It should be noted that the counter electrode layer is a single-layer metal electrode or a composite electrode composed of a metal and an ion storage layer.

[0065] For example, the material of the counter electrode layer is a non-reactive metal, including gold (Au), silver (Ag), copper (Cu), platinum (Pt), aluminum (Al) or titanium (Ti), and composite metals formed by multiple metals; the thickness of the metal counter electrode is above 20 nm, preferably 20 to 300 nm.

[0066] Furthermore, the electrolyte layer material includes any one of liquid electrolytes, gel electrolytes, and solid electrolytes; liquid electrolytes are composed of carbonate organic solvents and lithium salts; gel electrolytes are composed of polymers, electrolyte salts, and low-molecular-weight organic solvents; solid electrolytes include any one of inorganic electrolytes and polymer electrolytes.

[0067] Furthermore, the electrolyte layer uses a flexible microporous substrate as a carrier;

[0068] Flexible microporous substrates are used to provide a substrate for the working electrode layer and the counter electrode layer, and to provide a flow channel for the electrolyte.

[0069] It should be noted that a flexible microporous substrate is used, which is flexible and thin, unlike conventional thick glass-based electrochromic devices.

[0070] Furthermore, the flexible microporous substrate includes any one of the following: microporous filter membrane, microporous flexible plastic membrane, and track-etched membrane.

[0071] It should be noted that the materials used in microporous filter membranes include: Nylon 66, polyethersulfone (PES), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), mixed cellulose (MCE), and polypropylene (PP). The pore size of the microporous filter membrane ranges from 0.1 to 100 μm.

[0072] Microporous flexible plastic membrane materials include: polyethylene terephthalate (PET) membrane, polyimide (PI) membrane, polycarbonate (PC) membrane, and polyethylene naphthalate (PEN) membrane. The thickness of the microporous flexible plastic membrane is 0.02–0.5 mm.

[0073] The openings in the microporous flexible plastic film can be made using a CNC machine tool or laser drilling.

[0074] The microporous flexible plastic membrane has a pore size of 0.01–1 μm and a porosity of 1–60%, preferably 5–20%.

[0075] Track etching membrane is a type of microporous filter membrane prepared by track etching method. The materials of track etching membrane include: polycarbonate (PC) membrane, polyethylene terephthalate (PET) membrane, polyimide (PI) membrane, and polyethylene naphthalate (PEN) membrane.

[0076] The thickness of the track etching film is 0.02–0.5 mm.

[0077] The track-etched film has a pore size of 0.1–100 μm and a porosity of 1–60%, preferably 5–20%.

[0078] Furthermore, the flexible electrochromic bionic structure also includes a first encapsulation protective layer and a second encapsulation protective layer; the first and second encapsulation protective layers are used to protect the flexible electrochromic bionic structure; the second encapsulation protective layer is also used to provide visible light and infrared radiation windows for the flexible electrochromic bionic structure.

[0079] It should be noted that the first encapsulation protective layer is made of flexible material, and its function is to protect the flexible electrochromic bionic structure from water and oxygen erosion and external force damage.

[0080] The second encapsulation protective layer, serving as a window for the flexible electrochromic bionic structure, is made of a flexible material that is transparent across multiple visible and infrared bands. Its function is to protect the flexible electrochromic bionic structure from water and oxygen erosion and external force damage, and to provide a visible light and infrared radiation window for the flexible electrochromic bionic structure.

[0081] Furthermore, the first and second encapsulation protective layers are film products.

[0082] It should be noted that the materials of the first and second encapsulation protective layers include polyethylene (PE) film, polyethylene terephthalate (PET) film, and polyimide (PI) film.

[0083] The thickness of the first and second encapsulation protective layers is 0.01 to 1 mm, preferably 0.03 to 0.1 mm.

[0084] Furthermore, patterns on flexible electrochromic biomimetic structures, such as leaf patterns, can be prepared using methods such as metal masking, photolithography, screen printing, and inkjet printing.

[0085] Furthermore, the patterns of the flexible electrochromic biomimetic structure can also be square, rhomboid, polygonal, circular, and other patterns.

[0086] Based on the above embodiments, this invention also proposes a method for preparing a flexible electrochromic biomimetic structure.

[0087] For example, embodiments of the present invention provide an interference-modulated flexible electrochromic biomimetic leaf based on Au (gold) and WO3 (tungsten oxide). The flexible electrochromic biomimetic leaf is arranged from bottom to top as follows: a first PE encapsulation protective layer, an Au counter electrode layer, a gel electrolyte layer with a nylon 66 microporous filter membrane as a carrier, an Au reflective electrode layer, a WO3 electrochromic layer, and a second PE encapsulation protective layer.

[0088] like Figure 2 As shown, the working mechanism of the interference modulation type flexible electrochromic bionic leaf based on Au and WO3 is as follows: a 100nm thick Au film and a 290nm thick WO3 electrochromic layer form a reflective resonant cavity. The initial color of the resonant cavity is yellow (withered leaf). The WO3 electrochromic layer is a cathode electrochromic material. When an electric current is applied, WO3 gains electrons, and its optical constant changes, which in turn causes the color of the resonant cavity to turn green (fresh leaf).

[0089] The method for fabricating an interference-modulated flexible electrochromic biomimetic leaf based on Au and WO3 according to an embodiment of the present invention includes fabricating an Au reflective layer, a WO3 electrochromic layer, a first Au counter electrode, a first gel electrolyte layer, and an encapsulation protective layer, and then fabricating a flexible electrochromic biomimetic structure based on the Au reflective layer, the WO3 electrochromic layer, the first Au counter electrode, the first gel electrolyte layer, and the encapsulation protective layer. The steps are as follows:

[0090] Step 1: Preparation of Au / WO3 working electrode.

[0091] The surface of the nylon 66 microporous filter membrane is sputtered with Au film and WO3 film in sequence using a leaf-patterned metal mask to form an interference modulation type resonant cavity that can reversibly switch between yellow and green.

[0092] 1.1 Preparation of Au reflective layer.

[0093] The surface of the nylon 66 microporous filter membrane is covered with a metal mask plate with a leaf pattern. Figure 3 After that, place it on the substrate holder in the vacuum chamber, and evacuate the back vacuum to 3×10⁻⁶. -4 The pressure was below Pa, the argon flow rate was 50 sccm, the deposition pressure was 1.5 Pa, the sputtering power was 50 W, the target material was Au, and an Au film layer was deposited on the nylon 66 microporous filter membrane substrate by DC sputtering. The thickness of the Au film layer was controlled to be 100 nm.

[0094] 1.2 Preparation of WO3 electrochromic layer.

[0095] The nylon 66 microporous filter membrane substrate with Au membrane deposited was placed in a vacuum chamber, and the back vacuum was evacuated to 3×10⁻⁶. -4 Below Pa, argon flow rate 80 sccm, oxygen flow rate 10 sccm, deposition pressure 3.0 Pa, sputtering power 50 W, target material is WO3 target, WO3 film layer is further deposited on Au layer by radio frequency sputtering, and the thickness of WO3 film layer is controlled to 290 nm.

[0096] Step 2: Preparation of Au counter electrode.

[0097] The bottom surface of the nylon 66 microporous filter membrane is used to fabricate the Au counter electrode. After covering the bottom surface of the nylon 66 microporous filter membrane with a metal mask plate with a leaf pattern, it is placed on the substrate holder in the vacuum chamber, and the back-bottom vacuum is evacuated to 3×10⁻⁶. -4 The pressure was below Pa, the argon flow rate was 50 sccm, the deposition pressure was 1.5 Pa, the sputtering power was 50 W, the target material was Au, and an Au film layer was deposited on the nylon 66 microporous filter membrane substrate by DC sputtering. The thickness of the Au film layer was controlled to be 100 nm.

[0098] Step 3: Preparation of the gel electrolyte layer (using nylon 66 microporous filter membrane as a carrier).

[0099] The gel electrolyte uses propylene carbonate (PC) as the solvent, lithium perchlorate (LiClO4) as the solute, and polymethyl methacrylate (PMMA) as the polymer matrix. The lithium perchlorate concentration is 0.1 mol / L using a molar concentration meter. The prepared electrolyte solution is applied to the nylon 66 microporous filter membrane prepared in step 2, on which the working electrode and counter electrode are deposited, using a blade coating method. This allows the electrolyte to connect the working electrode and counter electrode through the pores of the filter membrane.

[0100] Step 4: Preparation of the encapsulation protective layer.

[0101] A 40μm thick polyethylene (PE) film is attached to the lower and upper surfaces of the microporous filter membrane obtained in step 3, and the membrane is then sealed using a heat sealing machine to obtain an encapsulated electrochromic bionic leaf.

[0102] refer to Figure 4 , Figure 4 The reflectance spectra of the bionic leaf before and after applying voltage were obtained. Different voltages were applied to the encapsulated electrochromic bionic leaf, and its color and infrared emissivity changed with the voltage. The initial color of the bionic leaf was yellow (withered leaf). When a -3V voltage was applied, the color changed from yellow (withered leaf) to green (fresh leaf), with an infrared emissivity of 0.54. When a +2V voltage was applied, the color changed from green (fresh leaf) to yellow (withered leaf), with an infrared emissivity of 0.72. The infrared emissivity of the bionic leaf could be adjusted within a range of 0.18.

[0103] In this embodiment of the invention, a reflective resonant cavity is formed by an Au film and a WO3 electrochromic layer. The initial color of the resonant cavity is yellow (withered leaves). The WO3 electrochromic layer is a cathode electrochromic material. When an electric current is applied, the WO3 gains electrons, and its optical constant changes, resulting in the resonant cavity turning green (fresh leaves). Based on this, the electrochromic effect is improved.

[0104] This invention also provides an interference-modulated flexible electrochromic biomimetic leaf based on Au / W / WO3 and its fabrication method. Figure 5 As shown, the electrochromic bionic leaf includes, from bottom to top, a first PE encapsulation protective layer, an Au counter electrode layer, an electrolyte layer with a microporous polyimide (PI) film as a carrier, an Au reflective electrode layer, a W (tungsten) reflective electrode layer, a WO3 electrochromic layer, and a second PE encapsulation protective layer.

[0105] The working mechanism of the Au / W / WO3-based interference modulation flexible electrochromic biomimetic leaf is as follows: Au and W films with thicknesses of 120nm and 100nm respectively, together with a WO3 electrochromic layer with a thickness of 245nm, form a reflective resonant cavity. The initial color of the resonant cavity is yellow (withered leaf). The WO3 electrochromic layer is a cathode electrochromic material. When an electric current is applied, the WO3 electrochromic layer gains electrons, and its optical constant changes, causing the color of the resonant cavity to turn green (fresh leaf).

[0106] The method for preparing an interference-modulated flexible electrochromic biomimetic leaf based on Au / W / WO3 according to an embodiment of the present invention includes preparing a polyimide film; preparing a second working electrode based on the polyimide film, Au, W, and WO3; preparing a second Au counter electrode, a second gel electrolyte layer, and an encapsulation protective layer; and then preparing a flexible electrochromic biomimetic structure based on the second working electrode, the second Au counter electrode, the second gel electrolyte layer, and the encapsulation protective layer. The steps are as follows:

[0107] Step 1: Preparation of mechanically perforated polyimide (PI) films.

[0108] A small CNC engraving machine was used to drill holes in a 0.125 mm thick polyimide (PI) film. The pore size and porosity of the polyimide (PI) film affect parameters such as emissivity and response time of the electrochromic device. Too few pores will obstruct the ion transport channels of the electrolyte, while too many pores will reduce the effective area of ​​the electrochromic layer. In this embodiment of the invention, the pore size is set to 0.5 mm and the porosity to 13%.

[0109] Step 2: Preparation of Au / W / WO3 working electrode.

[0110] An interference modulation resonant cavity with reversible switching between yellow and green is formed by sequentially sputtering Au, W, and WO3 films with thicknesses of 120 nm, 100 nm, and 245 nm onto the surface of a mechanically perforated polyimide (PI) film using a leaf-patterned metal mask.

[0111] Step 3: Preparation of Au counter electrode.

[0112] The bottom surface of a mechanically perforated polyimide (PI) film is used to prepare an Au counter electrode. After covering the bottom surface of the film with a metal mask featuring a leaf pattern, it is placed on a substrate holder in a vacuum chamber, and the back-bottom vacuum is evacuated to 3 × 10⁻⁶. -4 Below Pa, argon flow rate 50 sccm, deposition pressure 1.5 Pa, sputtering power 50 W, target material Au target, Au film layer is deposited on mechanically perforated polyimide (PI) thin film substrate by DC sputtering process, the thickness of Au film layer is controlled to 200 nm.

[0113] Step 4: Preparation of the gel electrolyte layer (mechanically perforated polyimide film as carrier).

[0114] The gel electrolyte uses propylene carbonate (PC) as the solvent, lithium perchlorate (LiClO4) as the solute, and polymethyl methacrylate (PMMA) as the polymer matrix. The lithium perchlorate concentration is 0.1 mol / L using a molar concentration meter. The prepared electrolyte solution is applied using a blade coating method to the mechanically perforated polyimide (PI) film prepared in step 3, which has a working electrode and a counter electrode deposited thereon. This allows the electrolyte to connect the working electrode and the counter electrode through the pores of the polyimide (PI) film.

[0115] Step 5: Preparation of the encapsulation protective layer.

[0116] The perforated polyimide (PI) film obtained in step 4 is covered with a 40 μm thick polyethylene (PE) film on its lower and upper surfaces, and then sealed using a thermoforming machine to obtain an encapsulated electrochromic biomimetic leaf.

[0117] By applying different voltages to the encapsulated electrochromic bionic leaf, its color and infrared emissivity change accordingly. The initial color of the bionic leaf is yellow (withered leaf). When a -3V voltage is applied, the color changes from yellow (withered leaf) to green (fresh leaf), with an infrared emissivity of 0.37. When a +2V voltage is applied, the color changes from green (fresh leaf) to yellow (withered leaf), with an infrared emissivity of 0.69. The infrared emissivity of the bionic leaf can be adjusted within a range of 0.32.

[0118] In this embodiment of the invention, a reflective resonant cavity is composed of an Au film, a W film, and a WO3 electrochromic layer. The initial color of the resonant cavity is yellow (withered leaves). The WO3 electrochromic layer is a cathode electrochromic material. When an electric current is applied, the WO3 electrochromic layer gains electrons, and its optical constant changes, causing the color of the resonant cavity to change to green (fresh leaves). Based on this, the electrochromic effect is improved.

[0119] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0120] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0121] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A flexible electrochromic biomimetic structure, characterized in that, include: The working electrode layer is used to switch camouflage reflection colors and adjust infrared emissivity; The electrode layer is used to conduct ions and electrons, providing the working electrode layer with the ions required for the color-changing reaction, so as to maintain the charge balance of the electrochromic process; The electrolyte layer provides interconnected active ion channels for the working electrode and the counter electrode layer, and isolates electron conduction. The working electrode layer includes a reflective metal layer and an electrochromic layer, which together form a reflective resonant cavity to create an initial camouflage color. The difference in infrared radiation characteristics between the target and the background is eliminated / reduced by adjusting the infrared emissivity. The initial camouflage color is changed by altering the optical constant of the electrochromic layer using different voltage values. The reflective metal layer is a gold (Au) reflective layer, and the electrochromic layer is a tungsten oxide (WO3) electrochromic layer. The thickness of the Au reflective layer is 100 nm, and the thickness of the WO3 electrochromic layer is 290 nm. The reflective metal layer can be a single-layer metal or a multi-layer metal; In the case of a flexible electrochromic biomimetic structure that is a flexible electrochromic biomimetic leaf, the initial camouflage color of the flexible electrochromic biomimetic leaf is yellow. By changing the applied voltage, the yellow color can be changed to green to achieve visible light camouflage; or, by changing the applied voltage to adjust the infrared emissivity, the yellow color can be changed to green to achieve infrared camouflage.

2. The flexible electrochromic biomimetic structure according to claim 1, characterized in that, The counter electrode layer is a single-layer metal electrode, or a composite electrode composed of a metal and an ion storage layer.

3. The flexible electrochromic biomimetic structure according to claim 1, characterized in that, The electrolyte layer is made of any one of liquid electrolytes, gel electrolytes, and solid electrolytes. The liquid electrolyte is composed of carbonate-based organic solvents and lithium salts; The gel electrolyte is composed of a polymer, an electrolyte salt, and a low-molecular-weight organic solvent; The solid electrolyte includes any one of inorganic electrolytes and polymer electrolytes.

4. The flexible electrochromic biomimetic structure according to claim 1, characterized in that, The electrolyte layer uses a flexible microporous substrate as a carrier; The flexible microporous substrate is used to provide a substrate for the working electrode layer and the counter electrode layer, and to provide a flow channel for the electrolyte.

5. The flexible electrochromic biomimetic structure according to claim 4, characterized in that, The flexible microporous substrate includes either a microporous filter membrane or a track-etched membrane.

6. The flexible electrochromic biomimetic structure according to claim 1, characterized in that, The flexible electrochromic biomimetic structure also includes a first encapsulation protective layer and a second encapsulation protective layer; The first and second encapsulation protective layers are used to protect the flexible electrochromic biomimetic structure; The second encapsulation protective layer is also used to provide visible light and infrared radiation windows for the flexible electrochromic biomimetic structure.

7. The flexible electrochromic biomimetic structure according to claim 6, characterized in that, The first and second encapsulation protective layers are film products.

8. A method for preparing a flexible electrochromic biomimetic structure, characterized in that, include: A gold Au reflective layer, a tungsten oxide WO3 electrochromic layer, a first Au counter electrode, a first gel electrolyte layer, and an encapsulation protective layer were prepared. A flexible electrochromic biomimetic structure is prepared based on the Au reflective layer, the WO3 electrochromic layer, the first Au counter electrode, the first gel electrolyte layer, and the encapsulation protective layer. The working mechanism of the interference modulation type flexible electrochromic bionic leaf based on Au and WO3 is as follows: a 100 nm thick Au film and a 290 nm thick WO3 electrochromic layer form a reflective resonant cavity. The initial color of the resonant cavity is yellow. The WO3 electrochromic layer is a cathode electrochromic material. When an electric current is applied, WO3 gains electrons, which causes the color of the resonant cavity to turn green. The preparation of the Au reflective layer includes: depositing the Au reflective layer on a nylon 66 microporous filter membrane by DC sputtering, wherein the target material is an Au target, the argon flow rate is 50 sccm, the deposition gas pressure is 1.5 Pa, the sputtering power is 50 W, and the Au layer thickness is controlled to be 100 nm. The preparation of the WO3 electrochromic layer includes: depositing the WO3 electrochromic layer on the Au reflective layer by radio frequency sputtering, wherein the target material is a WO3 target, the argon flow rate is 80 sccm, the oxygen flow rate is 10 sccm, the deposition pressure is 3.0 Pa, the sputtering power is 50 W, and the thickness of the WO3 layer is controlled to be 290 nm.

9. The method for preparing the flexible electrochromic biomimetic structure according to claim 8, characterized in that, The method further includes: Preparation of polyimide films; A second working electrode is prepared based on the polyimide film, Au, WO3, and tungsten W; Prepare a second Au counter electrode, a second gel electrolyte layer, and an encapsulation protective layer; The flexible electrochromic biomimetic structure is prepared based on the second working electrode, the second Au counter electrode, the second gel electrolyte layer, and the encapsulation protective layer.

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