Flexible dynamic infrared image display device and preparation and control method thereof

Abstract

The application discloses a flexible dynamic infrared image display device, which comprises a flexible support layer, a reflecting layer, a phase change material layer and a metal nanostructure layer arranged in sequence from bottom to top; the metal nanostructure layer is configured by a plurality of arrayed metal nanostructure units; the metal nanostructure unit has in-plane anisotropy and has a polarization conversion function in a working waveband range; in the metal nanostructure layer, the metal nanostructure units have different in-plane rotation angles, and different in-plane rotation angles correspond to different reflected light intensities. The phase change material is combined with the nanostructure, and dynamic infrared image display can be realized by changing an external current. Further, the application discloses a preparation method and a regulation method of the device.

Description

Technical Field

[0001] This invention belongs to the field of optical devices, and specifically relates to an infrared image display technology. Background Technology

[0002] Infrared image display devices are of great significance in many fields, including infrared target simulation, infrared camouflage, and anti-counterfeiting. The infrared image display function depends on the intensity distribution of the light output from the device, a function that can be achieved using metasurfaces. Metasurface devices realize image display functions by arranging nanostructures with different optical responses in space; however, once a static metasurface device is fabricated, its function is fixed. Various applications urgently require infrared image display devices that can be dynamically controlled to meet the needs of different operating environments.

[0003] In recent years, by integrating infrared metasurfaces with dynamically tunable materials, such as two-dimensional materials, transparent conductive oxides, and liquid crystal materials, some dynamically tunable infrared metasurface devices have been demonstrated, including dynamic infrared beam deflectors, dynamic infrared absorbers, and dynamic infrared polarization converters. However, these devices are usually fabricated on rigid substrates, which cannot adapt to working environments with complex morphologies.

[0004] Flexible optical meta-devices have garnered significant attention over the past few decades due to their wide range of applications. Designing dynamic metasurfaces on flexible substrates offers new possibilities for applications such as wearable sensors, dynamic absorbers, flexible photodetectors, and optical stealth. Phase change materials (PCMs) exhibit significant changes in their optical properties during the infrared band, making them suitable for realizing dynamic infrared image display devices. However, commonly used flexible substrates are polymer materials (such as polydimethylsiloxane and polyethylene terephthalate), which remain stable only below 500K, incompatible with the high-temperature fabrication processes of PCMs. Furthermore, temperature-controlled phase change processes limit device response speed and result in high power consumption. To date, no flexible electrically controlled infrared image display devices based on PCMs have been reported in the literature. Summary of the Invention

[0005] To address the aforementioned issues, this invention proposes a flexible dynamic infrared image display device that combines phase change materials with nanostructures. Dynamic infrared image display can be achieved through changes in applied current, i.e., electrically regulated infrared image display.

[0006] The specific technical solution of the present invention includes:

[0007] The first aspect of this invention discloses a flexible dynamic infrared image display device, comprising a flexible support layer, a reflective layer, a phase change material layer, and a metal nanostructure layer arranged sequentially from bottom to top; the metal nanostructure layer is constructed as being composed of a plurality of arrayed metal nanostructure units; the metal nanostructure units have in-plane anisotropy and polarization conversion function within the operating wavelength range; in the metal nanostructure layer, the metal nanostructure units have different in-plane rotation angles, and different in-plane rotation angles correspond to different reflected light intensities.

[0008] As an alternative, the flexible support layer is a flexible mica sheet; the reflective layer is a metal nanofilm; and the phase change material layer is a phase change material film, wherein the optical properties of the phase change material film in the working wavelength band change dynamically during the phase change process.

[0009] As an optional embodiment, the thickness of the flexible mica sheet is 5–100 μm; the thickness of the metal nanofilm is 100–200 nm; and the thickness of the phase change material layer is 200–300 nm.

[0010] As an alternative, the reflective layer is any one of gold nanofilm, silver nanofilm, copper nanofilm, aluminum nanofilm, or nanofilm prepared from the above alloy materials; the phase change material film is a film made of any one of vanadium dioxide, germanium-antimony-tellurium alloy, or antimony trisulfide.

[0011] As an alternative, the metal nanostructure unit is made of conductive metals such as gold, silver, copper, or aluminum, or alloys thereof.

[0012] As an optional embodiment, the metal structural unit is any one of the rod-shaped, L-shaped, V-shaped, and cross-shaped structures with in-plane anisotropy; the arrangement period of the metal nanostructure unit is 800-1000 nm; and the thickness of the metal nanostructure unit is 80-120 nm.

[0013] As an alternative, when the metal structural unit is rod-shaped, the corresponding metal nanorod has a length of 500–700 nm and a length of 80–150 nm.

[0014] As an alternative, the in-plane rotation angle of the metal nanostructure unit varies from 0 to 45°, which can achieve continuous modulation of the reflected light intensity from 0 to 0.5.

[0015] The second aspect of this invention discloses a method for preparing the flexible dynamic infrared image display device described in the first aspect of this invention and any alternative embodiment thereof, comprising the following steps:

[0016] A flexible support layer is provided;

[0017] A reflective layer is fabricated on the flexible support layer;

[0018] A phase change material layer is prepared on the reflective layer;

[0019] Metal nanostructure units are fabricated on the phase change material layer.

[0020] As an alternative, when the flexible support layer is a flexible mica sheet, it is prepared by mechanical exfoliation; metal nanomaterials are deposited on the flexible support layer by magnetron sputtering or electron beam evaporation to form a reflective layer; a phase change material is grown on the reflective layer by high-temperature annealing oxidation to form a phase change material layer; and metal nanostructure units are prepared on the phase change material layer by electron beam etching or ultraviolet lithography.

[0021] The third aspect of the present invention discloses another method for controlling the flexible dynamic infrared image display device described in the first aspect of the present invention and any of its optional embodiments, comprising: connecting the flexible dynamic infrared image display device to an external circuit, and dynamically adjusting the infrared image display of the infrared image display device by applying an external current; or, heating the infrared image display device, and dynamically adjusting the infrared image display of the infrared image display device by increasing the device's own temperature.

[0022] The present invention has the following beneficial effects:

[0023] (1) This invention uses mica flakes as a flexible substrate and combines phase change materials with nanostructures to realize a flexible dynamic infrared image display device. Furthermore, the flexible dynamic infrared image display device can be connected to an external circuit, and the display of infrared images can be dynamically adjusted by changing the applied current. It has advantages such as fast response speed, low energy consumption, and easy integration.

[0024] (2) The flexible dynamic infrared image display device provided by the present invention has a wider range of applications, such as wearable devices and adaptive infrared stealth, because the optical response of the metal nanostructure layer is not sensitive to the incident angle.

[0025] (3) In this invention, the metal nanorod, phase change material layer and metal film have a synergistic effect. When the in-plane rotation angle of the metal nanorod is 45°, it has polarization conversion function in the wavelength range of 2.5-3.5μm. Furthermore, by rotating the metal nanorod in-plane, the intensity of reflected light can be continuously controlled, thereby realizing an infrared image display device in the wavelength range of 2.5-3.5μm. Attached Figure Description

[0026] Figure 1(a) Schematic diagram of a flexible dynamic infrared image display device; (b) Schematic diagram of the structure within one cycle, where θ is the rotation angle of the metal nanorod.

[0027] Figure 2 (a) Reflectance spectra of x-polarization and y-polarization components of ten metal nanorod arrays with different in-plane rotation angles at applied currents of 0 mA and 550 mA; (b) Reflectance of x-polarization and y-polarization components at a wavelength of 3 μm extracted when the applied current is 0 mA as a function of nanorod rotation angle; (c) Reflectance of x-polarization and y-polarization components at a wavelength of 3 μm extracted when the applied current is 550 mA as a function of nanorod rotation angle.

[0028] Figure 3 (a) A scanning electron microscope image of the sample in a flexible electrically controlled infrared image (the scale bar in the image represents 2 μm), and an inset image of an optical microscope image (the scale bar in the image represents 50 μm); (b) An FPA image (focal plane array image) of the sample in a flat state at a wavelength of 3 μm throughout the entire cycle, including the applied current gradually increasing from 0 mA to 330 mA and 380 mA until 440 mA when vanadium dioxide undergoes a complete phase transition and the encoded image completely disappears, and the current decreasing from 440 mA to 330 mA and 280 mA until the image is restored; (c) An FPA image of the sample in a bent state at a wavelength of 3 μm when the applied current is 0 mA; (d) An FPA image of the sample in a bent state at a wavelength of 3 μm when the applied current is 440 mA, with a bending radius of 10 mm.

[0029] Figure 4 FPA images of a flexible dynamic infrared image display device at wavelengths of 2.8μm, 2.9μm, 3.1μm and 3.2μm.

[0030] Figure captions: 1-Flexible support layer, 2-Reflective layer, 3-Phase change material layer, 4-Metal nanorod. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. These embodiments are implemented based on the technical solutions of the present invention, and provide detailed implementation methods and specific design schemes. However, the scope of protection of the present invention is not limited to the following embodiments.

[0032] like Figure 1As shown in the figure, this invention provides a flexible dynamic infrared image display device based on vanadium dioxide. This device mainly includes a flexible support layer 1, a reflective layer 2, a phase change material layer 3, and a metal nanostructure layer 4 arranged sequentially from bottom to top. Specifically: the flexible support layer 1 is a synthetic fluorine-gold mica sheet prepared by mechanical exfoliation, also known as a "flexible mica sheet," characterized by high temperature resistance and atomic-level flatness, with a thickness typically of 5–100 μm. The reflective layer 2 is a gold nanofilm, prepared by magnetron sputtering on the flexible mica sheet, with a thickness typically of 100–120 nm, exhibiting a reflectivity close to 1 in the working wavelength band. The phase change material layer 3 is vanadium dioxide, grown on the gold nanofilm by high-temperature annealing oxidation, with a thickness distribution of approximately 200–300 nm; its optical properties in the working wavelength band change significantly during the phase transition process. The metal nanostructure layer 4 is an array composed of anisotropic metal nanorods with different in-plane rotation angles, i.e., a metal nanostructure array. The metal nanorods are made of gold, with a length of 500–600 nm, a width of 80–120 nm, a thickness of 80–120 nm, and a period of 800–1000 nm. The rotation angle θ of the metal nanorods varies from 0 to 45°, covering a reflected light intensity output range of 0–0.5. It should be noted that the numerical ranges A–B in this invention all include two endpoint values.

[0033] When the angle θ between the major axis and the y-axis of the metal nanorod is 45° and vanadium dioxide is in the insulating phase, the metal nanorod can convert x-polarized light with a wavelength range of 2.5–3.5 μm, which is incident perpendicularly, into y-polarized light for reflection. When x-polarized light is incident, the intensity of the y-polarized component of the reflected light can be modulated by rotating the metal nanorod in the xy plane. By gradually increasing the rotation angle of the metal nanorod from 0° to 45°, continuous modulation of the reflected light intensity from 0 to 0.5 can be achieved. When vanadium dioxide is in the metallic phase, the reflected light intensity of the y-polarized component of the metal nanorod is 0 at all rotation angles.

[0034] When the device is connected to an external power source, the phase transition process of vanadium dioxide can be controlled by the applied current. The applied current intensity should typically be sufficient to generate Joule heat that induces a phase transition in the vanadium dioxide material (the phase transition temperature of vanadium dioxide is approximately 68°C). In other embodiments, temperature control can also be used; the device can be placed on a heating plate to raise the overall temperature of the device, thereby inducing a phase transition in the vanadium dioxide material.

[0035] Because the optical response of metallic nanostructures is insensitive to the incident angle, the device can maintain its functional stability when bent with a radius of curvature not less than a preset value. When the incident angle of light is within the preset angle range (e.g., 0–50°), the optical response of the nanostructure remains stable, and correspondingly, the polarization conversion function also remains unchanged. The interaction between the incident light wave and the bent device can be equivalent to the superposition of incident light waves illuminating the flat device at various incident angles. Therefore, when the radius of curvature of the device substrate is greater than or equal to a preset value (e.g., 9 mm), the device maintains normal operation. Based on this principle, a grayscale image can be encoded into the rotation angle distribution of the metallic nanorods, realizing flexible electrically controlled infrared image display based on vanadium dioxide.

[0036] Understandably, the nanorods within a metal nanostructure array possess different rotation angles. When incident with x-polarization, analyzed with y-polarization, and with an applied current of 0, the metal nanorods provide different reflected light intensities at different in-plane rotation angles, which can be used to encode infrared images. In practical applications, the rotation angles of each nanorod in the metal nanostructure array can be designed based on the desired infrared image, thus mapping the grayscale distribution of the infrared image onto the rotation angle distribution of the nanorods in the metal nanorod array.

[0037] In other embodiments, the geometry of the anisotropic metal nanostructure in the metal nanostructure layer 4 can also be selected as an L-shaped, V-shaped, or cross-shaped structure with in-plane anisotropy, as long as it can excite different optical resonance modes in the structure when x-polarized light and y-polarized light are incident, and at the same time, within the working wavelength range, the amplitude ratio of the emitted light wave is around 1 and the phase difference is around 0.5π, so that it has the function of polarization conversion, then by rotating the metal nanostructure in the xy plane, infrared images can be encoded.

[0038] In other embodiments, the metal nanorods in the metal nanostructure layer 4 can be made of materials other than gold, such as silver, copper, aluminum, or the aforementioned alloy materials. As long as they have polarization conversion capabilities within the working wavelength band, they can be used to encode grayscale images.

[0039] In other embodiments, the reflective layer 2 can be any of the following, except for gold nanofilms: silver nanofilms, copper nanofilms, aluminum nanofilms, or nanofilms made of the above alloy materials. The thickness of the nanofilm is 100-200 nm.

[0040] In other embodiments, the phase change material layer 3 can also be made of germanium-antimony-tellurium alloy or antimony trisulfide material, which also have dynamically changing optical properties. The thickness of the phase change material layer can be 200–300 nm.

[0041] Furthermore, this invention also provides a method for fabricating a flexible dynamic infrared image display device, mainly comprising the following steps:

[0042] A flexible mica sheet is provided, which can be prepared by mechanical exfoliation.

[0043] A reflective layer was prepared by depositing a thin film of metal nanomaterials on a flexible mica sheet using magnetron sputtering or electron beam evaporation techniques.

[0044] A phase change material layer was prepared by growing a phase change material film on the gold nanofilm using a high-temperature annealing oxidation method.

[0045] Metal nanorod arrays were fabricated on a phase change material layer using electron beam etching or ultraviolet photolithography.

[0046] Figure 2 The paper presents the measurement results of the reflectance spectra of the x-polarization and y-polarization components of metal nanorod arrays with different in-plane rotation angles provided in embodiments of the present invention, when the applied current is 0 mA and 550 mA. Figure 2 (a) The reflection spectra of metal nanorods with ten different in-plane rotation angles selected at 5° intervals in the 2-4 μm range before and after the vanadium dioxide phase transition are given. When the rotation angle decreases from 45° to 0°, the y-polarization component of the reflection gradually decreases and the x-polarization component gradually increases when the applied current is 0 mA. Figure 2 (b) The reflectance at a wavelength of 3 μm is extracted as a function of the nanorod rotation angle, where the circular and triangular dots represent the measured y-polarization and x-polarization components, respectively. Based on these ten different in-plane rotation angles, a grayscale image can be encoded using the metal nanorods. At an applied current of 550 mA, Figure 2 (a) The reflectance of gold nanorods at different rotation angles is given. Figure 2 (c) shows the reflectance at an extracted wavelength of 3 μm as a function of the nanorod rotation angle, with the y- and x-polarized components of the reflected light remaining almost constant. This result demonstrates that dynamic infrared image display can be achieved using this vanadium dioxide-based electrically modulated nanostructure.

[0047] Figure 3 The invention provides a flexible dynamic infrared image display device, wherein the rotation angle distribution of the metal nanorods in the device is obtained by mapping a grayscale image of Maxwell's portrait. Figure 3 (a) Provides a partial scanning electron micrograph of the infrared image display sample provided in the embodiments of the present invention, where the scale bar is 2 μm. The inset is an optical micrograph with a scale bar of 50 μm. When x-polarized light is incident and y-polarized light is analyzed... Figure 3(b) The left side shows the FPA image of the device in a flat state at a wavelength of 3 μm without applied current, clearly presenting a Maxwell portrait. Figure 3 (b) top row ( Figure 3 The two images at the top of the middle position (b) show the FPA images of the measured device as the applied current gradually increases. The two images connected by arrows in the middle show the measurement results at applied currents of 330mA and 380mA, respectively. As the current increases, the y-polarization component reflected by the gold nanorods at all rotation angles decreases, leading to a decrease in the contrast of the measured FPA images. When the applied current exceeds 440mA, the y-polarization component reflected by the gold nanorods at all rotation angles decreases to 0, and the image disappears completely. Figure 3 (b) bottom row ( Figure 3 The two lower images (b) in the middle position show the FPA images as the measured applied current gradually decreases from 440mA to 0mA. The two images connected by arrows in the middle show the FPA images measured when the applied current is 330mA and 280mA, respectively, with the image contrast gradually increasing. This demonstrates that this electrically adjustable infrared image display is continuous and reversible. The infrared image display device also maintains its function even when bent. Figure 3 (c) and (d) are the FPA images of the device in a bent state (radius of curvature of 10 mm) with an applied current of 0 and 440 mA, respectively, corresponding to a wavelength of 3 μm. It can be seen that the device's electrically controlled infrared image display function remains unchanged in the bent state.

[0048] Figure 4 The paper presents pseudo-color FPA images of a flexible dynamic infrared image display device at wavelengths of 2.8 μm, 2.9 μm, 3.1 μm, and 3.2 μm when the applied current is 0 and 440 mA. The top and bottom rows correspond to the measurements taken when the sample is in a flat and bent state, respectively. Since the metal nanostructure possesses polarization conversion capabilities in the 2.5–3.5 μm wavelength range, the infrared image display function based on this also has a certain bandwidth. It can be seen that at these four wavelengths, regardless of whether the sample is in a flat or bent state, the device can achieve electrically regulated infrared image display.

[0049] In summary, this invention discloses a flexible, electrically regulated infrared image display device that combines phase change materials with nanostructures, enabling dynamic infrared image display through variations in applied current. This invention can be widely used in electrically regulated wearable devices, adaptive infrared stealth, and infrared camouflage.

[0050] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A flexible dynamic infrared image display device, characterized in that, It includes a flexible support layer, a reflective layer, a phase change material layer and a metal nanostructure layer arranged from bottom to top; The metal nanostructure layer is constructed as being composed of several arrayed metal nanostructure units. The metal nanostructure unit has in-plane anisotropy and polarization conversion function within the working wavelength range; in the metal nanostructure layer, the metal nanostructure unit has different in-plane rotation angles, and different in-plane rotation angles correspond to different reflected light intensities.

2. The flexible dynamic infrared image display device as described in claim 1, characterized in that, The flexible support layer is a flexible mica sheet; the reflective layer is a metal nanofilm; the phase change material layer is a phase change material film, and the optical properties of the phase change material film in the working wavelength band change dynamically during the phase change process.

3. The flexible dynamic infrared image display device as described in claim 2, characterized in that, The thickness of the flexible mica sheet is 5–100 μm; the thickness of the metal nanofilm is 100–200 nm; and the thickness of the phase change material layer is 200–300 nm.

4. The flexible dynamic infrared image display device as described in claim 1, characterized in that, The reflective layer is any one of gold nanofilm, silver nanofilm, copper nanofilm, aluminum nanofilm, or nanofilm prepared from the above alloy materials; the phase change material film is any one of vanadium dioxide, germanium-antimony-tellurium alloy, or antimony trisulfide; the metal nanostructure unit is made of conductive metals gold, silver, copper, aluminum, or the above alloy materials.

5. The flexible dynamic infrared image display device as described in claim 1, characterized in that, The metal structural unit is any one of the rod-shaped, L-shaped, V-shaped, and cross-shaped structures with in-plane anisotropy; the arrangement period of the metal nanostructure unit is 800-1000 nm; and the thickness of the metal nanostructure unit is 80-120 nm.

6. The flexible dynamic infrared image display device as described in claim 5, characterized in that, When the metal structural unit is rod-shaped, the corresponding metal nanorod has a length of 500–700 nm and a length of 80–150 nm.

7. The flexible dynamic infrared image display device according to any one of claims 1 to 6, characterized in that, The in-plane rotation angle of the metal nanostructure unit varies from 0 to 45°, enabling continuous modulation of the reflected light intensity from 0 to 0.

5.

8. A method, characterized in that, The method for fabricating the flexible dynamic infrared image display device as described in any one of claims 1 to 7 includes the following steps: A flexible support layer is provided; A reflective layer is fabricated on the flexible support layer; A phase change material layer is prepared on the reflective layer; Metal nanostructure units are fabricated on the phase change material layer.

9. The method as described in claim 8, characterized in that, When the flexible support layer is a flexible mica sheet, it is prepared by mechanical exfoliation; metal nanomaterials are deposited on the flexible support layer by magnetron sputtering or electron beam evaporation to form a reflective layer; phase change material is grown on the reflective layer by high-temperature annealing oxidation to form a phase change material layer; metal nanostructure units are prepared on the phase change material layer by electron beam etching or ultraviolet lithography.

10. A method, characterized in that, The method for controlling the flexible dynamic infrared image display device as described in any one of claims 1 to 7 includes: connecting the flexible dynamic infrared image display device to an external circuit and dynamically adjusting the infrared image display of the infrared image display device by applying an external current; or, heating the infrared image display device and dynamically adjusting the infrared image display of the infrared image display device by increasing the device's own temperature.

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