A visible light-infrared band ultrafast camouflage device and its preparation method and application

Abstract

A visible-infrared band ultrafast camouflage device and its preparation method and application, the camouflage device includes: a Joule heating layer for providing accurate and stable Joule heat; an insulating isolation layer for insulating the Joule heating layer from the electrocaloric effect layer; an electrocaloric effect layer, including a polymer electrocaloric film and electrocaloric electrodes on both sides, the electrocaloric effect layer is used to apply / remove an electric field to the polymer electrocaloric film through the electrocaloric electrodes while performing Joule heating on the Joule heating layer to generate an electrocaloric effect, so that the temperature signal transmitted to the thermochromic layer presents a square wave signal; the thermochromic layer is used to achieve instantaneous color switching under ultrafast temperature changes. The camouflage device prepared by the present invention utilizes the ultrafast temperature change characteristics of the electrocaloric effect, the stable heating of the Joule heat, and the rapid color change of the thermochromic material in response to temperature to provide an ultrafast and stable camouflage solution for the slow camouflage speed and overshoot problems of wearable visible-infrared band active camouflage devices.

Description

Technical Field

[0001] The present invention relates to the technical field of multi-band camouflage, and in particular to a visible light-infrared band ultrafast camouflage device and a preparation method and application thereof. Background Art

[0002] Camouflage is a common phenomenon in nature. In the process of human development, camouflage has long been discovered and used. Especially in the military field, camouflage plays an irreplaceable and important role. With the rapid development of visible light and infrared band imaging technology, due to its advantages of high resolution, low cost, portability, and easy integration, it has been increasingly used in military and life, playing the role of reconnaissance, identification, and observation. Therefore, the camouflage technology of their respective bands and the fusion camouflage technology have also received widespread attention in the past few decades.

[0003] Camouflage technologies can be mainly classified into static camouflage and dynamic camouflage. Static camouflage in the visible light band is mainly achieved through camouflage colors and matching with surrounding colors. Static camouflage in the infrared band is mainly divided into covering the surface of high-temperature objects with low-emissivity materials, heat-insulating materials, and designing structured surfaces. However, although many studies have achieved infrared camouflage effects under certain conditions, static camouflage is often only applicable in specific environments and is difficult to adapt to more complex environments. Dynamic camouflage in the visible light band mainly uses electrochromic, thermochromic, and mechanochromic methods to achieve active color switching. Dynamic camouflage in the infrared band is mainly achieved through active emissivity adjustment, active reflectivity adjustment, and active thermal management. However, camouflage achieved by adjusting the emissivity or reflectivity is easily affected by high-temperature objects in the environment, while active thermal management is more direct, which is less susceptible to environmental influences by actively controlling the temperature of the object surface or itself, such as microfluidic temperature control, thermoelectric temperature control, Joule heating effect, etc. However, this camouflage method requires temperature regulation of the object itself, so the time of heating and cooling process is mainly determined by the mass, heat capacity, and heating / cooling power of the camouflage device itself, and the camouflage speed is often slow. The temperature equilibrium time can be greatly reduced by programming the voltage, but this method is prone to overshoot, and the cooling time, except for camouflage devices based on thermoelectric effect, can only be cooled by passive heat dissipation. The time to fully recover to the ambient temperature is generally long, which makes the camouflage effect poor. Therefore, how to achieve ultra-fast camouflage to cope with the current high-resolution and high-speed detection methods is very important and urgent. Summary of the invention

[0004] In view of the problem that the temperature difference change rate and camouflage process of existing thermal camouflage devices are slow, the present invention provides a structural design, preparation method and application of an ultrafast camouflage device in the visible light-infrared band by combining the electrocaloric effect, Joule heat and thermochromic effect.

[0005] To achieve the above-mentioned object, the present invention provides an ultrafast camouflage device in the visible light-infrared band, which comprises a thermochromic layer, an electrocaloric effect layer, an insulating isolation layer and a Joule heating layer stacked in sequence along the thickness direction, wherein:

[0006] The Joule heating layer is used to provide accurate and stable Joule heat;

[0007] The insulating isolation layer is used to insulate and isolate the Joule heating layer from the electrocaloric effect layer;

[0008] The electrocaloric effect layer comprises a polymer electrocaloric film and electrocaloric electrodes attached to both sides. The electrocaloric effect layer is used to apply / remove an electric field to the polymer electrocaloric film through the electrocaloric electrodes to generate an electrocaloric effect while the Joule heating layer provides / removes Joule heat, so that the temperature signal transmitted to the thermochromic layer presents a square wave signal;

[0009] The thermochromic layer is used to achieve instantaneous color switching under temperature changes, and its color change temperature point is located within the range of the temperature signal corresponding to the electrocaloric effect layer when the electrocaloric effect is generated.

[0010] As a further preferred technical solution of the present invention, the thermochromic layer, the electrocaloric effect layer, the insulating isolation layer and the Joule heating layer are all made of flexible materials.

[0011] As a further preferred technical solution of the present invention, the Joule heating layer includes a thin layer electrode, which is a carbon nanotube network electrode, a silver nanowire network electrode, a PEDOT:PSS electrode, a graphite electrode or a graphene electrode; two copper wires are adhered to both sides of the thin layer electrode by silver glue or two lead electrodes with a width of 0.1-2 mm are formed by vacuum evaporation or magnetron sputtering.

[0012] As a further preferred technical solution of the present invention, the material of the insulating isolation layer is poly-4-methylpentene, water-based polyvinyl alcohol or polystyrene.

[0013] As a further preferred technical solution of the present invention, the electrocardiic material used in the polymer electrocardiic film is P(VDF-TrFE-CTFE), P(VDF-TrFE), P(VDF-HFP) or P(VDF-TrFE-CFE); the electrocardiic electrode is a carbon nanotube electrode, a silver nanowire electrode or a graphene electrode.

[0014] According to another aspect of the present invention, the present invention also provides a method for preparing an ultrafast camouflage device in the visible light-infrared band, which comprises the following steps:

[0015] S1. Dissolving the electrocaloric material in a polar solvent N,N-dimethylformamide to prepare a solution with a concentration of 5-25 wt %; preparing a film with a thickness of 10-40 μm by a drop coating method, a blade coating method or a spin coating method, and forming a polymer electrocaloric film after evaporating the solvent; wherein the solvent evaporation temperature is 60-120° C.; the electrocaloric material is P(VDF-TrFE-CTFE), P(VDF-TrFE), P(VDF-HFP) or P(VDF-TrFE-CFE);

[0016] S2. Electrocaloric electrodes are prepared on the upper and lower surfaces of the polymer electrocaloric film by vacuum evaporation, magnetron sputtering, spraying or printing, and an electrocaloric effect layer is formed by the polymer electrocaloric film and the electrocaloric electrodes on both sides; the electrocaloric electrodes are carbon nanotube electrodes, silver nanowire electrodes or graphene electrodes;

[0017] S3, dissolving poly-4-methylpentene (TPX), aqueous polyvinyl alcohol (PVA) or polystyrene (PS) in n-hexane, cyclohexane, water or toluene, preparing a film with a thickness of 3-20 μm on one surface of the electrocaloric effect layer by drop coating, blade coating or spin coating, and volatilizing the solvent to form an insulating isolation layer;

[0018] S4. Prepare a thin-layer electrode on the surface of the insulating isolation layer by spraying, scraping or printing a dispersion, and then adhere copper wires to both sides of the thin-layer electrode by silver glue and dry them, or form two lead electrodes with a width of 0.1-2 mm on both sides of the thin-layer electrode by vacuum evaporation or magnetron sputtering to obtain a Joule heating layer; the thin-layer electrode is a carbon nanotube network electrode, a silver nanowire network electrode, a PEDOT:PSS electrode, a graphite electrode or a graphene electrode;

[0019] S5. Apply the thermochromic powder dispersion or thermochromic liquid crystal coating on the other side of the electrocaloric effect layer by spraying, spin coating or blade coating to form a thermochromic layer.

[0020] According to another aspect of the present invention, the present invention also provides an application of a visible light-infrared band ultrafast camouflage device, wherein the visible light-infrared band ultrafast camouflage device is disposed on the surface of a device to be camouflaged after the color-changing area is designed according to a preset pattern, or one of the visible light-infrared band ultrafast camouflage devices is used as a color-changing unit, and a plurality of the color-changing units are arranged in an array on the surface of the device to be camouflaged. The device to be camouflaged is a wearable device.

[0021] As a further preferred technical solution of the present invention, the above application also includes a controller, which is used to electrically connect the Joule heating layer and the electrocaloric effect layer in the visible light-infrared band ultrafast camouflage device.

[0022] Compared with the existing technology, the following beneficial effects can be achieved:

[0023] The ultrafast camouflage device in the visible-infrared band provided by the present invention can achieve instantaneous temperature changes through the coordinated work of the electrocaloric effect and the Joule heating effect, and achieve instantaneous color switching through the thermochromic layer. Compared with previous studies, this work mainly shortens the time required for the heating process and the cooling process to room temperature by utilizing the rapid temperature change of the electrocaloric effect, and uses the camouflage device as a color-changing unit, which can be further optimized through array design, pattern design and camouflage color design, to achieve ultrafast switching of device temperature and color, as well as array and pattern control, to cope with more complex environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0025] Figure 1 This is a schematic diagram of the structure of the visible light-infrared band ultrafast camouflage device of Example 1.

[0026] Figure 2 This is a cross-sectional SEM image of the visible light-infrared band ultrafast camouflage device of Example 2.

[0027] Figure 3 The temperature variation with time and the color variation with time (at the time points of 2s, 7s, 20s, 38s, and 40s) of the camouflage device of comparative example 1 when only Joule heat is applied are shown.

[0028] Figure 4 The temperature of the camouflage device of Example 2 changes with time when Joule heat and electrocaloric effect are applied simultaneously, and the color changes with time (time points are 2s, 7s, 20s, 38s, and 40s).

[0029] Figure 5 This is an infrared image of the arrayed ultrafast switching control achieved after the arrayed color-changing units of the camouflage device of Example 3 are designed.

[0030] Figure 6 This is an infrared image of the color-changing unit of the camouflage device of Example 4 that achieves ultrafast temperature switching after patterning.

[0031] Figure 7 This is the ultrafast switching of the color of the color-changing unit of the camouflage device of Example 5 between black and white.

[0032] In the figure: 1. Thermochromic layer; 2. Electrocaloric effect layer; 21. Polymer electrocaloric film; 22. Electrocaloric electrode; 3. Insulation isolation layer; 4. Joule heating layer

[0033] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings in conjunction with the embodiments. DETAILED DESCRIPTION

[0034] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0035] Unless otherwise defined, the technical terms used in the following examples have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. The test reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods, unless otherwise specified, are all conventional methods.

[0036] The electrocaloric effect can achieve instantaneous temperature change, and its theoretical temperature change rate can reach 10 -8 s / K, showing the potential for ultrafast camouflage. Therefore, the electrocaloric effect is introduced into active thermal management to achieve ultrafast camouflage, and by further combining it with thermochromic materials, an ultrafast camouflage device based on square wave temperature in the visible light-infrared band is proposed. In the present invention, square wave temperature refers to the process of heating up and stabilizing and cooling down to the initial temperature in a very short time, so that the temperature signal presents the characteristics of a square wave signal.

[0037] Example 1

[0038] like Figure 1 As shown, this embodiment provides an ultrafast camouflage device in the visible light-infrared band, comprising a thermochromic layer 1, an electrocaloric effect layer 2, an insulating isolation layer 3 and a Joule heating layer 4, all of which are made of flexible materials and stacked in sequence along the thickness direction, wherein:

[0039] The Joule heating layer 4 is used to provide precise and stable Joule heat, that is, converting electrical energy into thermal energy to achieve stable temperature regulation; the Joule heating layer 4 includes a thin layer electrode, which is a carbon nanotube network electrode, a silver nanowire network electrode, a PEDOT:PSS electrode, a graphite electrode or a graphene electrode; two copper wires are adhered to both sides of the thin layer electrode by silver glue or two lead electrodes with a width of 0.1-2 mm are formed by vacuum evaporation or magnetron sputtering, and an external current is input into the thin layer electrode through the lead electrode or the copper wire to realize the conversion of electrical energy into thermal energy.

[0040] The insulating isolation layer 3 has a thickness of about 6 μm and is used to insulate and isolate the Joule heating layer 4 from the electrocaloric effect layer 2 ; the material of the insulating isolation layer 3 is poly-4-methylpentene, water-based polyvinyl alcohol or polystyrene.

[0041] The electrocaloric effect layer 2 has a thickness of about 28 μm and includes a polymer electrocaloric film 21 and electrocaloric electrodes 22 attached to both sides. The electrocaloric effect layer 2 is used to apply / remove an electric field to the polymer electrocaloric film 21 through the electrocaloric electrodes 22 to generate an electrocaloric effect while the Joule heating layer 4 provides / removes Joule heat, so that the temperature signal transmitted to the thermochromic layer 1 presents a square wave signal; the electrocaloric material used in the polymer electrocaloric film 21 is P(VDF-TrFE-CTFE), P(VDF-TrFE), P(VDF-HFP) or P(VDF-TrFE-CFE); the electrocaloric electrode 22 is a carbon nanotube electrode, a silver nanowire electrode or a graphene electrode.

[0042] The thermochromic layer 1 has a thickness of 3-20 μm and is used to achieve instantaneous color switching under ultrafast temperature changes, and its color change temperature point is located within the range of the temperature signal corresponding to the electrocaloric effect layer 2 when the electrocaloric effect is generated. The temperature of the thermochromic layer 1 is jointly regulated by the electrocaloric effect layer 2 and the Joule heating layer 4, that is, the heat transferred to the thermochromic layer is jointly acted upon by the electrocaloric effect layer and the Joule heating layer. Under the stable heating of Joule heat, the ultrafast temperature change characteristics of the electrocaloric effect are used to achieve square wave temperature, so that the thermochromic material responds quickly to the temperature and changes color, thereby achieving ultrafast color change camouflage of the camouflage device.

[0043] Specifically, the thermochromic layer is formed by coating a thermochromic powder dispersion or a thermochromic liquid crystal. Among them, the thermochromic powder can be purchased from Shenzhen Huancai Bianse Technology Co., Ltd. The thermochromic powder is also called a reversible thermochromic pigment. It is a powder particle (microcapsule) that repeatedly changes color as the temperature rises or falls. The particles are spherical and have an average diameter of 2 to 7 microns. The thermochromic powder can be prepared from an electron transfer type organic compound system. At a specific temperature (also known as thermochromic temperature or color change temperature point), the molecular structure of the organic matter changes due to electron transfer, thereby achieving color change, thereby achieving a color change from "colored-colorless", "colorless-colored" or "one color to another color" state. Of course, in actual use, it is not limited to the thermochromic powder sold by Shenzhen Huancai Bianse Technology Co., Ltd., and it can also use other thermochromic powders in the prior art with the above-mentioned functional characteristics. Preferably, the color-changing temperature point is selected as any temperature in the range of 10-60°C. Of course, materials with other color-changing temperature points can also be selected according to the actual use environment requirements, and thermochromic materials with three-stage color change can also be selected.

[0044] In actual applications, the visible light-infrared band ultrafast camouflage device is also equipped with a controller. The lead electrode or copper wire of the Joule heating layer and the electrocaloric electrode of the electrocaloric effect layer are respectively connected to the controller. The Joule heat of the Joule heating layer and the electrocaloric effect of the electrocaloric effect layer are both controlled by the controller.

[0045] In the present invention, while the Joule heating layer provides / removes Joule heat, an electric field is applied / removed to the polymer electrocaloric film to generate an electrocaloric effect, so that the temperature signal transmitted to the thermochromic layer presents a square wave signal, and the color change temperature point of the thermochromic layer is located within the interval of the temperature signal presenting the square wave signal. The temperature signal presenting a square wave signal is equivalent to a switch signal that triggers the thermochromic layer to change color (from "colored-colorless", "colorless-colored" or "one color to another color"). In the experimental process of the following embodiments, for the convenience of description, the state of triggering the thermochromic layer to change color when a square wave signal is generated is defined as "on"; the state of triggering the thermochromic layer to change color when the square wave signal is removed is defined as "off".

[0046] Example 2

[0047] This embodiment provides a method for preparing an ultrafast camouflage device in the visible light-infrared band, and the specific steps are as follows:

[0048] Step 1. Preparation of silver nanowires, carbon nanotubes, and thermochromic powder dispersions

[0049] 1) Preparation of silver nanowire dispersion: silver nanowires, methanol and isopropanol were mixed in a volume ratio of 1:2:4 and mixed for 30 minutes using a mixer.

[0050] 2) Preparation of carbon nanotube dispersion: 5 mg of carboxylated carbon nanotubes were dispersed in a mixture of 18 ml of isopropanol and 2 ml of deionized water, and probe ultrasonication was used for 40 min to prepare a carbon nanotube solution.

[0051] 3) Preparation of thermochromic powder dispersion: 0.03 g of thermochromic powder (color change temperature 31° C.), 0.1 ml of PDMS A component, 0.01 ml of PDMS B component and 3 ml of isopropanol solution were mixed together and mixed using a mixer for 30 min.

[0052] Step 2. Preparation of P(VDF-TrFE-CFE) thin film layer

[0053] 1.5g of P(VDF-TrFE-CFE) powder was mixed with 17.25g of DMF to form a solution, and the solution was fully stirred at 60°C for 12h to dissolve into a colorless, transparent, uniform solution. Filtered with a polytetrafluoroethylene (PTFE) filter with a pore size of 0.22μm, and degassed in a water bath for 2h. The film was prepared on a glass substrate by a solution method, and heated on a hot stage at 110°C for 2h to evaporate the solvent. After drying, it was demolded from the glass plate, and then the carboxylated carbon tube dispersion was evenly sprayed on the film, with an overlapping area of ​​4mm×4mm square. Finally, annealed at 120°C for 12h. The final film thickness of the P(VDF-TrFE-CFE) film layer was about 28μm, which was used as the electrocaloric effect layer.

[0054] Step 3. Preparation of TPX thin film

[0055] 0.5g poly-4-methylpentene (TPX) was mixed with 25ml cyclohexane to form a solution, and then stirred for 12h at 60℃ until it became a colorless, transparent, uniform solution. A TPX film was prepared on the prepared P(VDF-TrFE-CFE) film by the solution method, and the solvent was evaporated at room temperature for 30min. The film thickness was about 6μm, and the TPX film was obtained as an insulating isolation layer.

[0056] Step 4. Preparation of silver nanowire heater

[0057] First, the silver nanowire dispersion was sprayed on the surface of the TPX film to form a 4×6mm rectangular thin-layer electrode, with the middle area overlapping the effective electrocaloric effect area of ​​the P(VDF-TrFE-CFE) film layer. The copper wire was fixed to the extra 1mm area on both sides of the thin-layer electrode using silver glue, and cured at room temperature for 30 minutes and at 40°C for 1 hour to achieve the construction of the Joule heating layer.

[0058] Step 5. Preparation of thermochromic layer

[0059] The thermochromic powder dispersion was sprayed on the other side of the P(VDF-TrFE-CFE) film and heated at 60°C for 1h to prepare the thermochromic layer, and finally complete the construction of an ultrafast camouflage device in the visible light-infrared band based on square wave temperature.

[0060] The structure of the camouflage device of Example 2 is as follows Figure 1 As shown, the cross-sectional SEM image of the camouflage device is as follows Figure 2 shown.

[0061] Comparative Example 1

[0062] As the control experimental group of Example 2, the difference is that the electrocaloric effect layer is not provided, and the rest remains the same as Example 2. The obtained camouflage device consists of a thermochromic layer, an insulating isolation layer and a Joule heating layer stacked in sequence along the thickness direction.

[0063] When Joule heat is applied to the camouflage device of Example 1, the temperature and color (blue when the thermochromic layer is closed and white when it is opened) change with time as shown in the following curves: Figure 3 As shown in the figure, when the device is heated by Joule heating power of 1.10mW, 1.57mW, 2.16mW, and 2.48mW respectively, it can be seen that the heating and cooling time required to heat to the specified temperature using only Joule heating is greater than 10 seconds (the effective heating area of ​​Joule heating is 4mm×4mm). It can be seen from the color change process that its color changes slowly as the temperature rises / falls during the heating (7s) and cooling (38s) processes.

[0064] When the camouflage device of Example 2 is subjected to Joule heat and electrocaloric effect, the temperature and color (blue when the thermochromic layer is closed and white when it is opened) change with time as shown in the following curves: Figure 4 As shown, relative to Figure 3 Only the time for Joule heat heating to reach the same temperature difference is used. It can be seen that here, when 1.10mW, 1.57mW, 2.16mW, and 2.48mW of power are applied / removed respectively to the Joule heating layer, 52MV / m, 61MV / m, 77MV / m, and 96MV / m are applied / removed to the electrocaloric film layer at the same time, the time required for the heating and cooling process is shorter (the active area of ​​the electrocaloric film and the Joule heating area are both 4mm×4mm, the thickness of the electrocaloric film is 28μm, and the TPX layer is 6μm), which is almost completed in an instant, close to a "square wave" temperature signal. At the same time, the color is also switched instantly. This is mainly due to the electrocaloric effect of the P (VDF-TrFE-CFE) film layer, which can make the temperature respond instantly to the change of the electric field to achieve the specified temperature difference, while the Joule heat mainly provides the ability to stabilize the temperature difference to achieve a continuous camouflage effect.

[0065] Example 3

[0066] This embodiment provides an application of an ultrafast camouflage device in the visible-infrared band. Based on the method of the above embodiment 2, multiple ultrafast camouflage devices in the visible-infrared band are prepared. Each camouflage device is used as an independent color-changing unit to form a 3×3 array. When working, each unit applies 2.16mW of power to the Joule heating layer and 77MV / m of electric field to the electrocaloric film layer. The effective area is 6mm×6mm. PLC, relay, single-chip microcomputer, etc. are used as controllers to independently control each unit (specifically, the control of the Joule heating layer and the electrocaloric effect layer). Figure 5As shown, it can be seen that the camouflage device is designed in a simple array (3×3), and each unit is independently intelligently controlled to achieve instantaneous temperature switching. The 3×3 array ultrafast camouflage device was tested using an infrared thermal imager. By programming the on / off mode of different points, the pattern is turned on and off every 5 seconds, and the three letters "N", "K" and "U" are displayed respectively when turned on, and return to the ambient temperature instantly when turned off. The temperature difference between the working temperature of each unit (~33°C) and the ambient temperature (~30°C) is about 3K. It has the ability to carry out large-scale arraying to increase the coverage area and regional camouflage, and can adapt to more complex environments.

[0067] Example 4

[0068] This embodiment provides an application of an ultrafast camouflage device in the visible light-infrared band. The ultrafast camouflage device in the visible light-infrared band is prepared based on the method of the above embodiment 2. The effective area of ​​the camouflage device is as follows: Figure 6 The pattern displayed in the on state, the effective area here refers to the overlapping area of ​​the effective color change area of ​​the thermochromic layer, the electrocaloric effect area of ​​the electrocaloric effect layer and the Joule heating effective area of ​​the Joule heating layer. It can be seen that the effective area of ​​the camouflage device is prepared into a more complex pattern (such as an airplane shape) by the mask method. Under the condition of an ambient temperature of ~30°C, the temperature of its effective area instantly reaches ~33°C (on state) when the device is turned on, and the temperature returns to the ambient temperature (off state) when the device is turned off. Therefore, the camouflage device can be designed with more complex patterns according to actual requirements, thereby realizing instantaneous camouflage of complex patterns, thereby coping with more complex usage situations.

[0069] Example 5

[0070] This embodiment provides an application of an ultrafast camouflage device in the visible light-infrared band. The ultrafast camouflage device in the visible light-infrared band is prepared based on the method of the above-mentioned embodiment 2. The thermochromic layer is prepared using a thermochromic material with a color change temperature point of 31°C that changes from black to white. The effective area is 6mm×6mm. During operation, the power applied to the Joule heating layer is 2.16mW, and the electric field applied to the electrocaloric film layer is 77MV / m. The color change process is captured using an optical camera. The color of the camouflage device can achieve ultrafast switching between black and white. Figure 7 As shown. It can be seen that at room temperature of ~29°C, the surface color of the ultrafast camouflage device is black (off state). When the device is turned on, the surface color of the ultrafast camouflage device instantly changes to white (on state), demonstrating its ability to switch colors ultrafast in the visible light band, thereby being able to cope with detection methods with higher frame rates.

[0071] Although specific embodiments of the present invention are described above, those skilled in the art should understand that these are merely examples and that various changes or modifications may be made to the embodiments without departing from the principles and essence of the present invention. The scope of protection of the present invention is limited only by the appended claims.

Claims

1. A visible light-infrared band ultrafast camouflage device, characterized in that: It includes a thermochromic layer, an electrocaloric effect layer, an insulating isolation layer and a Joule heating layer which are sequentially stacked along the thickness direction, wherein: The Joule heating layer is used to provide stable Joule heat; The insulating isolation layer is used to insulate and isolate the Joule heating layer from the electrocaloric effect layer; The electrocaloric effect layer comprises a polymer electrocaloric film and electrocaloric electrodes attached to both sides. The electrocaloric effect layer is used to apply / remove an electric field to the polymer electrocaloric film through the electrocaloric electrodes to generate an electrocaloric effect while the Joule heating layer provides / removes Joule heat, so that the temperature signal transmitted to the thermochromic layer presents a square wave signal; The thermochromic layer is used to achieve instantaneous color switching under temperature changes, and its color change temperature point is located within the range of the temperature signal corresponding to the electrocaloric effect layer when the electrocaloric effect is generated.

2. The visible light-infrared band ultrafast camouflage device according to claim 1, characterized in that: The thermochromic layer, the electrocaloric effect layer, the insulating isolation layer and the Joule heating layer are all made of flexible materials.

3. The visible light-infrared band ultrafast camouflage device according to claim 1, characterized in that: The Joule heating layer includes a thin layer electrode, which is a carbon nanotube network electrode, a silver nanowire network electrode, a PEDOT:PSS electrode, a graphite electrode or a graphene electrode; two copper wires are adhered to both sides of the thin layer electrode by silver glue, or two lead electrodes with a width of 0.1-2 mm are formed by vacuum evaporation or magnetron sputtering.

4. The visible light-infrared band ultrafast camouflage device according to claim 1, characterized in that: The material of the insulating isolation layer is poly-4-methylpentene, water-based polyvinyl alcohol or polystyrene.

5. The visible light-infrared band ultrafast camouflage device according to claim 1, characterized in that: The electrocardiic material used in the polymer electrocardiic film is P (VDF-TrFE-CTFE), P (VDF-TrFE), P (VDF-HFP) or P (VDF-TrFE-CFE); the electrocardiic electrode is a carbon nanotube electrode, a silver nanowire electrode or a graphene electrode.

6. The method for preparing a visible light-infrared band ultrafast camouflage device according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Dissolving the electrocaloric material in a polar solvent N,N-dimethylformamide to prepare a solution with a concentration of 5-25 wt %; preparing a film with a thickness of 10-40 μm by a drop coating method, a blade coating method or a spin coating method, and forming a polymer electrocaloric film after evaporating the solvent; wherein the solvent evaporation temperature is 60-120° C.; the electrocaloric material is P(VDF-TrFE-CTFE), P(VDF-TrFE), P(VDF-HFP) or P(VDF-TrFE-CFE); S2. Electrocaloric electrodes are prepared on the upper and lower surfaces of the polymer electrocaloric film by vacuum evaporation, magnetron sputtering, spraying or printing, and an electrocaloric effect layer is formed by the polymer electrocaloric film and the electrocaloric electrodes on both sides; the electrocaloric electrodes are carbon nanotube electrodes, silver nanowire electrodes or graphene electrodes; S3, dissolving poly-4-methylpentene, aqueous polyvinyl alcohol or polystyrene in n-hexane, cyclohexane, water or toluene, preparing a film with a thickness of 3-20 μm on one surface of the electrocaloric effect layer by drop coating, blade coating or spin coating, and volatilizing the solvent to form an insulating isolation layer; S4. Prepare a thin-layer electrode on the surface of the insulating isolation layer by spraying, scraping or printing a dispersion, and then adhere copper wires to both sides of the thin-layer electrode by silver glue and dry them, or form two lead electrodes with a width of 0.1-2 mm on both sides of the thin-layer electrode by vacuum evaporation or magnetron sputtering to obtain a Joule heating layer; the thin-layer electrode is a carbon nanotube network electrode, a silver nanowire network electrode, a PEDOT:PSS electrode, a graphite electrode or a graphene electrode; S5. Apply the thermochromic powder dispersion or thermochromic liquid crystal coating on the other side of the electrocaloric effect layer by spraying, spin coating or blade coating to form a thermochromic layer.

7. Use of the visible light-infrared band ultrafast camouflage device according to any one of claims 1 to 5, or the visible light-infrared band ultrafast camouflage device prepared by the method according to claim 6, characterized in that: The color-changing area of ​​the visible light-infrared band ultrafast camouflage device is designed according to a preset pattern and arranged on the surface of the device to be camouflaged, or one visible light-infrared band ultrafast camouflage device is used as a color-changing unit, and multiple color-changing units are arranged in an array on the surface of the device to be camouflaged.

8. The use according to claim 7, characterized in that: It also includes a controller, which is used to electrically connect the Joule heating layer and the electrocaloric effect layer in the visible light-infrared band ultrafast camouflage device.

9. The use according to claim 7, characterized in that: The device to be disguised is a wearable device.

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