A method for fabricating a flexible and stable color-changing device based on microstructure confinement

Abstract

This invention discloses a flexible, stable color-changing device based on microstructure confinement, its fabrication method, and its applications, belonging to the fields of smart materials and flexible optoelectronics. The device consists of a flexible substrate layer, a functional response layer, and a protective layer. The functional response layer comprises a microporous mesh structure and a stimulus-responsive cholesteric liquid crystal material filling the pores. The microporous mesh structure forms a three-dimensional physical confinement for the liquid crystal, effectively suppressing macroscopic flow and performance degradation of the liquid crystal under flexible deformation. The cholesteric liquid crystal, employing a chiral doping system or an intrinsic cholesteric phase system, can achieve continuous and reversible color changing in response to temperature or electric field. Electrochromism can be achieved after integrating a transparent conductive layer. This invention solves the problem of poor stability of cholesteric liquid crystals on flexible carriers, improving the device's mechanical flexibility and environmental tolerance while retaining its excellent optoelectronic properties. Furthermore, the process is simple and the structure is controllable, showing broad application prospects in adaptive camouflage, human body temperature sensing, and flexible wearable devices.

Description

Technical Field

[0001] This invention belongs to the field of smart materials and flexible optoelectronics technology, and relates to a method for fabricating a flexible and stable color-changing device based on microstructure confinement. Background Technology

[0002] Cholesteric liquid crystals, as smart materials with a unique photonic bandgap structure, can selectively reflect visible light to exhibit vibrant structural colors, and their reflected wavelengths can continuously and reversibly change with external stimuli (such as temperature, electric fields, and magnetic fields). Therefore, they show great application potential in fields such as adaptive camouflage, intelligent sensing, and flexible displays. However, cholesteric liquid crystals have a certain degree of fluidity when in the liquid crystal state, which leads to their extreme instability on non-enclosed flexible substrates. Existing technical approaches mainly focus on two aspects: one is to form microcapsules using polymer-dispersed liquid crystals (PDLCs) or polymer-stabilized liquid crystals (PSLCs) to confine liquid crystal molecules within micron-sized isolated droplets. However, due to the uneven distribution of polymer mesh pore sizes, the color change is uneven, affecting the liquid crystal response performance. The second approach is to use flexible sandwich encapsulation. Under repeated dynamic bending, the modulus mismatch between the encapsulation layer and the liquid crystal layer will generate shear stress. If the mechanical stability of the encapsulation layer is poor, it is easy to cause interface delamination or peeling, making it difficult to guarantee the stability of the device during long-term use.

[0003] In summary, existing technologies have failed to effectively reconcile the contradiction between liquid crystal response performance and overall device flexibility and stability. Therefore, developing a novel composite structure that can maximize the preservation of the excellent optoelectronic properties of cholesteric liquid crystals while endowing them with fabric-like mechanical robustness has become a key bottleneck that urgently needs to be overcome to advance this technology towards practical applications. Summary of the Invention

[0004] Technical issues Cholesteric liquid crystals are fluid and extremely unstable on non-enclosed flexible substrates. Existing polymer dispersion / stabilization and flexible sandwich encapsulation technologies either affect the response and color change uniformity or are prone to interface delamination, making it difficult to balance their optoelectronic performance and device flexibility and stability.

[0005] Technical content This invention aims to overcome the technical challenge of maintaining the morphological stability of cholesteric liquid crystals in flexible dynamic application scenarios while minimizing the loss of core optoelectronic performance. This enables flexible color-changing devices to withstand repeated bending, rubbing, and squeezing like ordinary textile fabrics, and to maintain reliable color-changing function over a long period of time in external environments such as humidity and alternating high and low temperatures.

[0006] To achieve the above objectives, this invention proposes a novel solution based on microstructure confinement. A textile mesh is mounted on a flexible substrate as a physical confinement framework, and liquid crystal is filled within the mesh, followed by polymer encapsulation. Compared to existing polymer mesh or encapsulation structures, this solution offers the following significant advantages: First, the textile mesh, through a precision weaving process, achieves highly uniform pore sizes, ensuring consistent liquid crystal filling and synchronized response in each micro-region, fundamentally solving the problem of uneven color change caused by uneven pore size distribution in polymer meshes. Second, the core mesh confinement design reconstructs the stress transmission path, with the mesh framework bearing the main load, thus protecting the liquid crystal from damage. Furthermore, the thickness of the textile mesh can be precisely controlled by selecting different wire diameters or the number of weaving layers, allowing for free design of the liquid crystal layer thickness to adapt to the response speed and optical density requirements of different application scenarios.

[0007] Based on this, the present invention provides a flexible and stable color-changing device, the structure of which, from top to bottom, includes: an outer protective layer, a liquid crystal-mesh composite functional layer, and a flexible substrate layer.

[0008] Furthermore, the outer protective layer is a transparent resin coating with a thickness of 10-30 μm and an average transmittance of more than 92% for visible light (400-700nm).

[0009] Furthermore, the resin used to form the outer protective layer can be one or more of silicone acrylate resin, polyurethane, fluorocarbon resin or epoxy resin.

[0010] Furthermore, the liquid crystal-mesh composite functional layer consists of a textile mesh and liquid crystal material filling the mesh openings.

[0011] Furthermore, the pore size of the textile mesh is 60-180 μm, the thickness is 60-120 μm, and the porosity is 60%-75%.

[0012] Furthermore, the textile mesh can be made of a plain weave with monofilament; the weaving material includes any one of polyester, nylon 66, and aramid 1313, with a monofilament diameter of 20-50 μm.

[0013] Furthermore, the liquid crystal material is a stimulus-responsive cholesteric liquid crystal system; the stimulus-responsive cholesteric liquid crystal system includes a temperature-responsive cholesteric liquid crystal system or an electric field-responsive cholesteric liquid crystal system.

[0014] Furthermore, the temperature-responsive cholesteric phase liquid crystal system is composed of 2-6 parts cholesterol oleyl carbonate, 1-5 parts cholesterol nonanoate, and 2-6 parts cholesterol chloride.

[0015] Furthermore, the electric field-responsive cholesteric liquid crystal system consists of 7 to 11 parts of E7 and 0.5 to 3 parts of R-811.

[0016] Furthermore, the flexible base layer uses a high-strength flexible fabric as the flexible base, which can be made of polyester, aramid, high-strength nylon, ultra-high molecular weight polyethylene fiber fabric and their blended fabrics, giving the patch overall flexibility and wearability; if the flexible base layer has other performance requirements, the high-strength flexible fabric can be replaced with other high-strength, high-elasticity, high-temperature resistant, conductive and magnetic, or breathable and moisture-permeable fabrics as the base.

[0017] Furthermore, when the liquid crystal material is selected from an electric field-responsive cholesteric liquid crystal system, an upper conductive layer and an upper alignment layer are sequentially provided between the liquid crystal-mesh composite functional layer and the outer protective layer from top to bottom, and a lower alignment layer and a lower conductive layer are sequentially provided between the liquid crystal-mesh composite functional layer and the flexible substrate layer from top to bottom.

[0018] Furthermore, the upper conductive layer and the lower conductive layer are deposited silver nanomaterials; the silver nanomaterials can be silver nanopowder, silver nanowires, or silver nanosheets.

[0019] Furthermore, the upper and lower orientation layers are made of polyimide.

[0020] The aforementioned flexible and stable color-changing devices can be applied to adaptive camouflage, human body temperature sensing, or flexible wearable devices.

[0021] The preparation method of the above-mentioned flexible stable color-changing device includes the following steps: (1) Weigh the liquid crystal raw materials according to their mass components, mix and heat them until the clearing point is above the clearing point, stir evenly, and obtain a color-changing liquid crystal system; (2) Lay the textile mesh onto the flexible substrate and fix it in place; (3) Apply the color-changing liquid crystal system to the fixed textile mesh, so that the liquid crystal penetrates and fills the pores of the textile mesh; (4) Coat the top layer with a layer of resin material and dry to obtain a flexible and stable color-changing device.

[0022] In one embodiment, heating to clear point or above in step (1) means that the liquid crystal completely loses its molecular orientation order under continuous heating and transforms into an optically isotropic and completely transparent state.

[0023] In one embodiment, in step (2), the textile mesh is subjected to oxygen plasma cleaning before laying under the conditions of radio frequency power of 50~150 W, oxygen flow rate of 30~70 sccm, chamber pressure maintained at 30~70 Pa, and processing time of 30~120 s.

[0024] In one embodiment, the flexible substrate layer in step (2) can be cleaned, dried, and then the textile mesh can be fixed.

[0025] In one embodiment, fixing in step (2) includes applying pressure or using an adhesive for fixing.

[0026] In one embodiment, step (3) involves operations such as dripping, pouring, and scraping, as long as the liquid crystal fills the pores of the textile mesh.

[0027] In one embodiment, when the liquid crystal material is an electric field-responsive cholesteric liquid crystal system, before the textile mesh is laid and fixed, a silver nanomaterial dispersion is deposited on the flexible substrate to prepare a lower conductive layer, and then a polyimide solution is coated to prepare a lower alignment layer; after the liquid crystal fills the pores of the textile mesh, a polyimide solution is coated to prepare an upper alignment layer, and then a silver nanowire dispersion is deposited to prepare an upper conductive layer.

[0028] Beneficial effects Compared with existing technologies, the forest understory light and shadow adaptive camouflage patch provided by this invention has the following significant advantages: (1) Inherent mechanical stability: The textile mesh, as a continuous phase skeleton, bears most of the tensile and shear stress on the patch, protecting the internal liquid crystal from damage. The patch can withstand more than 1,000 harsh bends with extremely low performance degradation, realizing the transformation from a brittle coating to a tough composite film.

[0029] (2) Exceptional environmental reliability: The mesh and the cured outer protective layer together form a dense cage-like protective structure, effectively blocking the intrusion of water vapor, salt, and ultraviolet rays. The patch can pass multiple environmental adaptability tests in standards such as GJB 150A, meeting the requirements for long-term use.

[0030] (3) Excellent optical performance retention: The micro-pore confinement ensures the high uniformity of the liquid crystal layer thickness, making the color change of large-area patches uniform, and the color difference ΔE can be controlled within 1.5, ensuring the integrity and consistency of the camouflage visual effect.

[0031] (4) Good process compatibility and scalability: The structure allows for manufacturing using mature textile coating and lamination processes, paving the way for large-scale, low-cost production. At the same time, this basic platform is easy to expand in function, for example, by compounding multiple temperature-sensitive materials in the mesh to achieve a wider color change range, or by integrating other functional coatings on the outer layer. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the flexible, stable thermochromic device structure in Example 1; Figure 2 This is a schematic diagram of the flexible stable electrochromic device structure in Example 2; Figure 3 Optical microscope and SEM images of the textile mesh used in Examples 1 and 2; Figure 4 The image shows the flexible, stable thermochromic camouflage patch prepared in Example 1 undergoing cycling at high and low temperatures. Figure 5 The heating response time diagram of the flexible stable thermochromic device prepared in Example 1; Figure 6 An example image showing the camouflage effect of the flexible, stable thermochromic device prepared in Example 1; Figure 7 The flexible bending diagram of the flexible and stable thermochromic device prepared in Example 1; Figure 8 DSC image of the flexible stable thermochromic device prepared in Example 1; Figure 9 POM diagram of the liquid crystal system prepared in Example 1 that responds to human fever temperature (37.3 °C); Detailed Implementation The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The specific embodiments described below further illustrate the present invention.

[0033] The testing method involved in this invention: 1. Polarizing Microscopy (POM) Analysis: When testing thermochromic devices, the sample was placed on a polarizing microscope equipped with a constant-temperature heating stage. The temperature was increased and decreased at a rate of 2 °C / min. The color of the sample at each temperature was recorded using a polarizing microscope and a digital camera. When testing electrochromic devices, the device was placed under crossed polarizers and connected to a 1 kHz sinusoidal AC power supply. Starting from 0 V, the voltage was gradually increased to 10 V in 0.5 V steps. After stabilization at each voltage point, polarizing microscope images and corresponding colors were acquired.

[0034] 2. Color uniformity test: Use a colorimeter to uniformly select at least 10 points on the sample surface for measurement, and calculate the color difference ΔE*ab between each point and the average value. ΔE < 2.0 is generally considered to indicate good uniformity.

[0035] 3. Adhesion Test: The adhesion of the camouflage patch was tested according to GB / T 9286-2021 "Cross-cut Test for Paints and Varnishes". The patch sample was placed flat on a hard surface. Using a cross-cutting tool, six parallel cuts (1 or 2 mm apart) were made on the coating surface with uniform force and speed, ensuring the depth completely cuts through all coating to the base fabric surface. The cuts were repeated perpendicular to the first set, forming a 6×6 grid pattern. Debris was gently brushed away along the diagonal of the grid with a soft brush. Transparent tape was firmly adhered to the grid area, pressing it flat with the fingers to ensure complete contact. After holding for 60 seconds, one end of the tape was held, and the tape was quickly peeled off at a 60° angle within 0.5-1.0 seconds. Under illumination, the extent of coating peeling in the grid area was observed with a magnifying glass, and rated from 0-5 according to the standard.

[0036] 4. Anti-interference performance: During daily wear, the camouflage patch will continuously undergo a bending-restoration-bending process. A bending performance test was conducted on the camouflage patch. The patch was bent from both sides towards the middle, and its color performance was tested after 200 bends at different angles using a POM (Positive Oxidation Membrane) device.

[0037] 5. Damp heat resistance aging: Refer to Procedure I (constant damp heat) in GJB 150.9A-2009 "Laboratory Environmental Test Methods for Military Equipment Part 9: Damp Heat Test". Place the sample in a constant temperature and humidity chamber (70±2℃, 95%±3% RH) for continuous exposure for 500 hours. After the cycle, allow it to recover for 24 hours under standard conditions (23℃, 50% RH), and then comprehensively test its optical and mechanical properties, calculating the performance retention rate.

[0038] 6. High and Low Temperature Cycling: Referring to GJB 150.4A-2009 "Laboratory Environmental Testing Methods for Military Equipment Part 4: Low Temperature Test" and the high temperature test method, a cyclic procedure was established: maintain at -40℃ for 2 hours, increase the temperature to 70℃ at a rate of 10℃ / min, maintain at 70℃ for 2 hours, and decrease the temperature to -40℃ at a rate of 10℃ / min. This constitutes one cycle. A total of 50 cycles were performed. Performance changes before and after each cycle were tested.

[0039] 7. SAM Angle Test: A portable field spectrometer is used, requiring a wavelength range of at least 400-1000 nm and a resolution ≤3 nm. Using a handheld or fixed spectrometer probe, baseline calibration is performed by aligning the spectrometer with a standard white board before each measurement and when ambient light intensity changes. In the target environment (e.g., forest), select 3-5 representative background types, such as: healthy green leaves, withered yellow leaves, moist soil, dry soil, and shaded areas of tree trunks and bark. For each background type, spectral measurements are taken at 10-15 points in its typical area, and the average value is used as the reference spectral vector for that background type.

[0040] Example 1 1. Raw materials: Nylon Oxford cloth, deionized water, cholesterol chloride, cholesterol oleyl carbonate (COC), cholesterol nonanoate (CN), polyester plain weave mesh (pore size 80-160 μm, thickness 100 μm), silicone acrylate resin, ethanol.

[0041] 2. Preparation steps: (1) Cleaning the background layer: First, soak the nylon base fabric in 40 ℃ warm water for 5 minutes to fully wet it. Use an ultrasonic cleaner with the power set to 200W, frequency 40 kHz, and temperature 45 ℃ for 10 minutes. After dehydration, hang it to air dry at room temperature for 30 minutes, and then place it in an 80℃ oven to dry for 60 minutes.

[0042] (2) Preparation of thermochromic cholesteric liquid crystal system: Weigh 4 parts of COC, 3 parts of CN and 4 parts of cholesterol chloride, mix them in a beaker with a rotor, place it on a magnetic heating stirring table, heat it to above the clearing point, stir evenly, and obtain thermochromic cholesteric liquid crystal system.

[0043] (3) Pretreatment of textile mesh: The cut polyester monofilament mesh is placed into the reaction chamber of the oxygen plasma cleaner. The treatment parameters are set as follows: radio frequency power is 100 W, oxygen flow rate is 50 sccm, chamber pressure is maintained at 50 Pa, and treatment time is 90 s.

[0044] (4) Forming the liquid crystal mesh composite layer: After oxygen plasma cleaning, the polyester mesh is flattened and adhered to the background layer (within 30 minutes after cleaning). A low-viscosity roller is used to gently press and ensure initial adhesion. The liquid crystal system from step (2) is heated to above the clearing point to achieve an isotropic state. It is then quickly poured onto one end of the mesh and rapidly coated using a glass rod preheated to 80°C. Capillary action and scraping pressure are used to completely impregnate the mesh with the liquid crystal melt. The layer is then moved to a room temperature cooling platform, where the liquid crystal rearranges within the mesh pores to form a cholesteric phase, resulting in a complete liquid crystal-mesh composite functional layer.

[0045] (5) Constructing / encapsulating the isolation layer: A low-viscosity silicone acrylate resin ethanol solution is uniformly coated onto the surface of the liquid crystal mesh composite layer. The patch is placed in an oven and heated to dry, forming a smooth, dense, transparent encapsulation hard film with a thickness of 10-30 μm.

[0046] Comparative Example 1 (CE1): Meshless Reference Group The preparation process is exactly the same as E1, the only difference being the omission of step 2 (mesh laying). The heated liquid crystal is directly coated onto the background layer, and after cooling, a conventional liquid crystal coating is formed. This comparative example is used to verify the necessity of the core structure.

[0047] Comparative Example 2 (CE2): Large Aperture Mesh Group The only difference was that the mesh in step 2 of E1 was replaced with a polyester mesh with an average pore size of 280 μm (other parameters remained similar). This was used to verify the critical effect of the lower limit of the mesh pore size.

[0048] Comparative Example 3 (CE3): Small aperture / low porosity mesh group The mesh in step 2 of E1 was replaced with a polyester mesh with an average pore size of 45 μm and an open area of ​​approximately 40%. This was used to verify the upper limit of the mesh pore size and issues related to wetting and filling.

[0049] Comparative Example 4 (CE4): Groups with different liquid crystal ratios The liquid crystal ratio in step 3 of E1 was simply changed to 2 parts COC, 8 parts CN, and 1 part cholesterol chloride. This was used to verify the synergistic effect between a specific liquid crystal formulation and the network structure.

[0050] Comparative Example 5 (CE5): Group without outer protective layer The preparation process is the same as E1, but step 4 (coating the protective layer) is omitted. This is crucial for verifying the environmental tolerance of the outer protective layer.

[0051] Table 1

[0052] The optical properties of the test samples are shown in Table 1. As shown in CE4, even with the same structure, a degraded liquid crystal formulation can lead to a shift in the color change range. This indicates that the optimal performance of this invention is the result of the synergistic effect of a specific liquid crystal formulation (4:3:4) and a specific mesh structure, rather than a simple superposition. Meanwhile, the textile mesh has a significant impact on the optical properties of the samples. As shown in CE1, the mesh is the cornerstone of color development stability, and there are optimal parameters for the mesh. Both CE2 and CE3 show that when the aperture is too large, the mesh confinement effect is weak; when the aperture is too small, mesh filling is difficult, resulting in the liquid crystal not achieving optimal color development within the mesh. This indicates that the optimal mesh parameters in this invention are 80-160 μm.

[0053] Table 2

[0054] The mechanical stability properties of the tested samples are shown in Table 2. CE5, lacking a protective layer, had its adhesion test performed primarily on the liquid crystal layer itself, resulting in unstable results. A comparison between E1 and CE1 shows that the textile mesh plays a decisive role in the mechanical stability of the samples. Simultaneously, the protective layer also has a positive effect on the mechanical stability of the samples.

[0055] Table 3

[0056] The environmental stability performance of the test samples is shown in Table 3. As can be seen from CE5, the outer protective layer is crucial for environmental durability. The rapid failure of CE5 in damp heat and cycling tests highlights the indispensability of the outer protective layer in resisting corrosion from real-world complex environments. It, together with the mesh, constitutes a double layer of protection: microscopic confinement and macroscopic encapsulation.

[0057] Table 4

[0058] The camouflage performance of the test samples is shown in Table 4. As can be seen from the optimal embodiment E1 of this invention, in both main camouflage states, the spectral blending degree with the corresponding natural background reached a good or higher level (SAM≤8.2°), confirming its effective dynamic adaptive capability. In contrast, the SAM angles of comparative examples CE1 and CE4 increased significantly (>12°), resulting in a degraded camouflage effectiveness. This is directly attributed to the lack of a grid structure and the inappropriate liquid crystal formulation. Therefore, from the perspective of optical camouflage effectiveness, this strongly verifies the necessity and synergy of the core technical features of this invention.

[0059] Table 5

[0060] By adjusting the proportion of the cholesteric liquid crystal, it can be precisely matched to the human body temperature range, as shown in Table 5. Using this device as a human body temperature sensor, it displays a bright green light when the human body has a fever, which has significant application value in the field of flexible wearables.

[0061] Example 2 (E2) A nylon mesh with a pore size of 80-160 μm and a thickness of 100 μm was used, and the remaining steps were the same as in Example 1.

[0062] Example 3 (E3) An aramid mesh with a pore size of 80-160 μm and a thickness of 100 μm was used, and the remaining steps were the same as in Example 1.

[0063] Table 6

[0064] As shown in Table 6, when only the material of the textile mesh is changed, the performance of the device is not affected, which proves the versatility of textile mesh materials.

[0065] Example 4 (E4) 1. Raw materials: Nylon Oxford cloth, deionized water, E7, R-811, polyimide solution, polyester plain weave mesh (pore size 80-160 μm, thickness 100 μm), silicone acrylate resin, ethanol.

[0066] 2. Preparation steps: (1) Cleaning the background layer: First, soak the nylon base fabric in 40°C warm water for 5 minutes to fully wet it. Use an ultrasonic cleaner with the power set to 200W, frequency 40 kHz, and temperature 45 ℃ for 10 minutes. After dehydration, hang it to air dry at room temperature for 30 minutes, and then place it in an 80°C oven to dry for 60 minutes.

[0067] (2) Preparation of conductive substrate: Silver nanowires (diameter 30-50 nm, length 20-30 μm) were deposited on nylon base fabric by spraying to form a conductive layer. The operation was to spray the silver nanowire dispersion (concentration 2 mg / mL) onto the nylon base fabric and then anneal it (120℃, 15 minutes). The thickness of the conductive layer was 150-250 nm.

[0068] (3) Preparation of the lower alignment layer: Polyimide solution was coated on the conductive layer by spin coating at 3000 rpm for 40 s. The sample was pre-cured at 80 °C for 10 minutes and imidized at 200 °C for 60 minutes. Finally, the surface was rubbed with a cloth for alignment. The thickness of the alignment layer was 50-100 nm.

[0069] (4) Preparation of electrochromic cholesteric liquid crystal system: Weigh 9 parts of E7 and 1 part of R-811, mix them in a beaker with a rotor, place it on a magnetic heating stirring table, heat it to above the clearing point, stir it evenly, and obtain the electrochromic cholesteric liquid crystal system.

[0070] (5) Pretreatment of textile mesh: The cut polyester monofilament mesh is placed into the reaction chamber of the oxygen plasma cleaner. The treatment parameters are set as follows: radio frequency power is 100 W, oxygen flow rate is 50 sccm, chamber pressure is maintained at 50 Pa, and treatment time is 90 seconds.

[0071] (6) Forming the liquid crystal mesh composite layer: After oxygen plasma cleaning, the polyester mesh is flattened and adhered to the background layer (within 30 minutes after cleaning). A low-viscosity roller is used to gently press and ensure initial adhesion. The liquid crystal system from step (4) is heated to above the clearing point to achieve an isotropic state. It is then quickly poured onto one end of the mesh and rapidly coated using a glass rod preheated to 80 °C. Capillary action and scraping pressure are used to completely impregnate the mesh with the liquid crystal melt. The layer is then moved to a room temperature cooling platform, where the liquid crystal rearranges within the mesh pores to form a cholesteric phase, resulting in a complete liquid crystal-mesh composite functional layer.

[0072] (7) Preparation of the upper orientation layer: Polyimide solution was coated on the liquid crystal-mesh composite layer by spin coating at 1000 rpm for 40 s. The sample was pre-cured at 80 °C for 10 minutes, imidized at 180 °C for 60 minutes, and finally rubbed with a cloth to align the surface. The thickness of the orientation layer was 50-100 nm.

[0073] (8) Preparation of the upper conductive layer: Silver nanowires (diameter 30-50 nm, length 20-30 μm) are deposited on the orientation layer by spraying to form a conductive layer. The operation is to spray the silver nanowire dispersion (concentration 2 mg / mL) onto the nylon base fabric and then anneal it (120℃, 15 minutes). The thickness of the conductive layer is 150-250 nm.

[0074] (9) Upper substrate layer composite and protective layer coating: The nylon fabric layer is lightly pressed onto the upper conductive layer, and the low viscosity silicone acrylate resin ethanol solution is uniformly scraped onto the surface of the liquid crystal mesh composite layer. After the patch is placed in the oven and heated and dried, a smooth, dense, transparent encapsulation hard film with a thickness of 10-30 μm is formed.

[0075] Table 7

[0076] As shown in Table 7, within the range of 0-8 V, the device color changes continuously from reddish-brown to blue, with high color saturation and uniform texture, proving that the grid confinement structure effectively ensures the uniform response of the liquid crystal.

[0077] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A flexible stabilized color changing device, characterized in that, The structure of the flexible stable color-changing device, from top to bottom, includes: an outer protective layer, a liquid crystal-mesh composite functional layer, and a flexible substrate layer; The outer protective layer is a transparent resin coating with a thickness of 10-30 μm; The liquid crystal-mesh composite functional layer consists of a textile mesh and liquid crystal material filled inside the mesh pores; the pore size of the textile mesh is 60-180 μm, the thickness is 60-120 μm, and the porosity is 60%-75%; the liquid crystal material includes temperature-responsive cholesteric liquid crystal system or electric field-responsive cholesteric liquid crystal system. The flexible substrate layer uses a high-strength flexible fabric as the flexible substrate.

2. A flexible stabilised colour changing device as claimed in claim 1, characterised in that, The resin is selected from one or more of the following: silicone acrylate resin, polyurethane, fluorocarbon resin, or epoxy resin.

3. The flexible stabilized color-changing device of claim 1, wherein The textile mesh is made of plain weave monofilament; the weaving material includes any one of polyester, nylon 66, and aramid 1313, and the monofilament diameter is 20-50 μm.

4. The flexible stabilized color-changing device of claim 1, wherein The temperature-responsive cholesteric phase liquid crystal system consists of 2-6 parts cholesterol oleyl carbonate, 1-5 parts cholesterol nonanoate, and 2-6 parts cholesterol chloride.

5. The flexible stabilized color-shifting device of claim 1, wherein The electric field-responsive cholesteric liquid crystal system consists of 7 to 11 parts of E7 and 0.5 to 3 parts of R-811.

6. The flexible stabilized color-changing device of claim 1, wherein The flexible base layer is made of polyester, aramid, high-strength nylon, ultra-high molecular weight polyethylene fiber fabrics and their blends.

7. The flexible stabilized color-changing device of claim 1, wherein When the liquid crystal material is selected from the electric field responsive cholesteric liquid crystal system, an upper conductive layer and an upper alignment layer are arranged from top to bottom between the liquid crystal-mesh composite functional layer and the outer protective layer, and a lower alignment layer and a lower conductive layer are arranged from top to bottom between the liquid crystal-mesh composite functional layer and the flexible substrate layer. The upper and lower conductive layers are deposited silver nanomaterials; the silver nanomaterials are silver nanopowder, silver nanowires, or silver nanosheets. The upper and lower orientation layers are made of polyimide.

8. The application of the flexible stable color-changing device according to any one of claims 1 to 7 in adaptive camouflage, human body temperature sensing or flexible wearable devices.

9. A method for the production of a flexible stabilized color changing device according to any one of claims 1 to 7, characterized in that Includes the following steps: (1) Weigh the liquid crystal raw materials according to their mass components, mix and heat them until the clearing point is above the clearing point, stir evenly, and obtain a color-changing liquid crystal system; (2) Lay the textile mesh onto the flexible substrate and fix it in place; (3) Apply the color-changing liquid crystal system to the fixed textile mesh, so that the liquid crystal penetrates and fills the pores of the textile mesh; (4) Coat the top layer with a layer of resin material and dry to obtain a flexible and stable color-changing device.

10. The preparation method according to claim 9, characterized in that, In step (2), before the textile mesh is laid, it is cleaned with oxygen plasma under the following conditions: radio frequency power of 50~150 W, oxygen flow rate of 30~70 sccm, chamber pressure of 30~70 Pa, and processing time of 30~120 s.

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