A leaf-like hydrogel composite fabric and a preparation method thereof

Abstract

The application discloses a kind of leaf-like hydrogel composite fabric and preparation method thereof, belong to bionic composite material field.The preparation of leaf-like hydrogel composite fabric of the application includes as follows: respectively preparing uniform sodium alginate solution and acidic solution, after injecting sodium alginate solution into mould, green fabric is laid on its surface and is stationary for a certain time, then acidic solution is added again, stationary is acid-induced phase separation, i.e., hydrogel composite fabric with directional conical porous structure is obtained;After that, it is immersed in hygroscopic salt solution, after standing, leaf-like hydrogel composite fabric is prepared.The bionic composite fabric presents complete plant leaf spectral characteristics in the range of 400~2500 nm, and can efficiently simulate the transpiration of plant leaf.In addition, the material has good hygroscopic-desorption cycle stability, which guarantees the reliability of the bionic material in long-term application in the field of camouflage.

Description

Technical Field

[0001] This invention relates to a leaf-like hydrogel composite fabric and its preparation method, belonging to the field of biomimetic composite materials. Background Technology

[0002] Abundant green plants are distributed in terrestrial environments, effectively concealing and hiding combat targets, making them one of the most common combat backgrounds. Leaves, as the core component of green plants, not only possess unique visible-near-infrared reflectance spectral characteristics but also exhibit continuous transpiration and heat dissipation. Water, as the central link, closely correlates the spectral characteristics of leaves with transpiration; the two synergistically reflect the plant's physiological metabolic state and water use efficiency, providing a core direction for the development of biomimetic camouflage materials. Based on these characteristics of plant leaves, biomimetic materials that simulate their spectral characteristics and transpiration can be developed, effectively countering hyperspectral remote sensing and thermal infrared detection technologies, significantly improving the concealment and protection of targets against a plant background.

[0003] Currently, combining hygroscopic hydrogels with flexible fabrics is one of the effective technical approaches to achieve compatible simulation of plant leaf spectral characteristics and transpiration, and related research has made some progress. For example, Chinese patent CN114214847A discloses a leaf biomimetic material based on viscose fabric, which is prepared by gelation reaction of sodium alginate and calcium chloride on the fabric surface, and can efficiently simulate the spectral characteristics of leaves; Chinese patent CN119529317B uses 2-acrylamide-2-methylpropanesulfonic acid / polyvinyl alcohol to polymerize and gel on polyester fabric, realizing the synergistic simulation of leaf spectral characteristics and transpiration. However, the aforementioned existing technologies still have significant limitations in practical camouflage applications and are difficult to meet the needs of actual combat: In the biomimetic material prepared by CN114214847A, the hygroscopic salt is prone to leakage, which leads to unstable moisture absorption performance of the material, attenuation of the blade feature simulation effect, and poor long-term durability of the material; Although CN119529317B effectively solves the problem of hygroscopic salt leakage, the material's moisture absorption response speed is slow and cannot quickly adapt to the dynamic changes in temperature and humidity in complex combat environments, thus affecting the timeliness and reliability of the camouflage effect.

[0004] Therefore, in order to further improve the actual camouflage performance of biomimetic blade materials and address the shortcomings of existing technologies in terms of response speed and cycle stability, developing new biomimetic blade materials that simultaneously possess rapid temperature and humidity response capabilities and long-term cycle stability is an urgent problem to be solved in the field of camouflage materials. Summary of the Invention

[0005] [Technical Issues] Existing biomimetic materials for blades, which combine hydrogels and fabrics, are prone to problems such as moisture absorption and salt leakage, and low moisture absorption rate in applications. This not only causes unstable water absorption performance of the material, attenuation of the simulation effect of blade spectral characteristics and reduced durability, but also makes it difficult to respond quickly to dynamic changes in temperature and humidity in complex combat environments.

[0006] [Technical Solution] To address the aforementioned problems, this invention provides a leaf-like hydrogel composite fabric and its preparation method; this composite fabric not only enables simultaneous simulation of leaf spectral characteristics and transpiration, but also possesses rapid response capability to environmental temperature and humidity and excellent moisture absorption cycle stability.

[0007] The biomimetic composite fabric prepared by this invention exhibits complete spectral characteristics of plant leaves in the 400-2500 nm wavelength range, encompassing the "green peak," "red edge," "near-infrared plateau," and "moisture absorption valley." Simultaneously, relying on the synergistic effect of the internal conical porous hydrogel and hygroscopic salts, this material can rapidly and self-drivenly absorb / release water according to ambient temperature and humidity, efficiently simulating the transpiration process of plant leaves. Furthermore, the directional conical pore structure of the hydrogel in the material generates an asymmetric Laplace pressure difference. This structural characteristic effectively inhibits the loss of hygroscopic salts from the hydrogel, significantly improving the stability of the material during multiple moisture absorption-desorption cycles and ensuring the reliability of this biomimetic material for long-term application in the field of camouflage.

[0008] To achieve the above objectives, the following technical solution is provided: The first objective of this invention is to provide a method for preparing leaf-like hydrogel composite fabrics, comprising the following steps: (1) Preparation of green fabrics: The colorant, printing auxiliary agent and water are mixed evenly and stirred until they become a paste to obtain the printing paste; then the printing paste is printed onto the surface of the fabric using screen printing to obtain green fabric. (2) Preparation of cone-shaped porous hydrogel composite fabric: Prepare uniform sodium alginate solution and acidic solution respectively. After injecting sodium alginate solution into the mold, lay the green fabric obtained in step (1) on its surface and let it stand for a certain time. Then add acidic solution and let it stand for acid-induced phase separation to obtain hydrogel composite fabric with directional conical porous structure. (3) Preparation of leaf-like hydrogel composite fabrics: The cone-shaped porous hydrogel composite fabric obtained in step (2) is immersed in a hygroscopic salt solution and left to stand to obtain a leaf-like hydrogel composite fabric.

[0009] In one embodiment, the colorant in step (1) includes one or more of chromium oxide, disperse dye, vat dye, acid dye, reactive dye, dried leaf powder, and sodium copper chlorophyll.

[0010] In one embodiment, the printing auxiliary agent in step (1) includes one or more of dispersants, thickeners, and adhesives.

[0011] In one embodiment, the dispersant includes 85A and AD. 4600, 5080W, NNO, DM 1501, DM 1501N, PVP, BYK One or more of 190.

[0012] In one embodiment, the thickener includes TF-3181SS, TF-313E, TF-313B, TF-312NW, and DM. 5221G, DM 5228, DM 5298. One or more of sodium alginate.

[0013] In one embodiment, the adhesive includes TF-3211, TF-321A, TF-3201YD, TF-3201R, TEP, and BST. One or more of N788, DM 5128A, and DM 5120.

[0014] In one embodiment, the printing paste in step (1) is prepared by mixing and stirring a colorant, a printing auxiliary agent and water to form a paste; wherein the amount of the colorant in the printing paste is 0.1~5.0 wt%; and the amount of the printing auxiliary agent in the printing paste is 5~40.0 wt%.

[0015] In one embodiment, the fabric in step (1) includes one or more of polyester fabric, polyester-cotton blended fabric, cotton fabric, viscose fabric, and nylon fabric.

[0016] In one embodiment, the sodium alginate solution in step (2) is prepared by mixing sodium alginate powder with water to form a slurry; wherein the amount of sodium alginate powder in the sodium alginate solution is 1~5 wt.

[0017] In one embodiment, the stirring conditions are: temperature of 20~40 °C, stirring speed of 1000~5000 rpm, and time of 8~12 h.

[0018] In one embodiment, the acidic solution in step (2) is obtained by mixing an acidic substance with water and stirring until homogeneous; wherein the amount of the acidic substance in the acidic solution is 1~55 wt%; more preferably 10~30%; more preferably 15~25%.

[0019] In one embodiment, the stirring conditions are: temperature of 2~40 °C, stirring speed of 500~1500 rpm, and time of 10~30 min.

[0020] In one embodiment, the acidic substance includes one or more of 2-acrylamide-2-methylpropanesulfonic acid, hydrochloric acid, and sulfuric acid; preferably 2-acrylamide-2-methylpropanesulfonic acid.

[0021] In one embodiment of the present invention, in step (2), the volume ratio of sodium alginate solution to acidic solution in the mold is 1:(1~3); preferably 1:2.

[0022] In one embodiment, the conditions for step (2) to stand for a certain period of time are: temperature of 20~40 °C and time of 20~40 min.

[0023] In one embodiment, the conditions for the acid-induced phase separation in step (2) are: temperature of 20~40 °C and time of 6~12 h.

[0024] In one embodiment, in step (2), the hydrogel has multiple oriented conical porous channels with a pore size of 100~350 μm.

[0025] In one embodiment, the hygroscopic salt solution in step (3) is obtained by mixing hygroscopic salt and water and stirring evenly; wherein the amount of hygroscopic salt in the hygroscopic salt solution is 1~35 wt%; preferably 10%.

[0026] In one embodiment, the hygroscopic salt is one or more of lithium chloride (LiCl), calcium chloride (CaCl2), lithium bromide (LiBr), and magnesium chloride (MgCl2).

[0027] In one embodiment, the immersion conditions in step (3) are: temperature of 20~40 °C and time of 12~24 h.

[0028] The second objective of this invention is to provide a leaf-like hydrogel composite fabric based on the above preparation method.

[0029] A third objective of this invention is to provide the application of the aforementioned leaf-like hydrogel composite fabric in the field of camouflage.

[0030] The fourth objective of this invention is to provide a method for improving the rapid response capability and moisture absorption cycle stability of leaf-like hydrogel composite fabrics, the method comprising the following steps: (1) Preparation of green fabrics: The colorant, printing auxiliary agent and water are mixed evenly and stirred until they become a paste to obtain the printing paste; then the printing paste is printed onto the surface of the fabric using screen printing to obtain green fabric. (2) Preparation of cone-shaped porous hydrogel composite fabric: Prepare uniform sodium alginate solution and acidic solution respectively. After injecting sodium alginate solution into the mold, lay the green fabric obtained in step (1) on its surface and let it stand for a certain time. Then add acidic solution and let it stand for acid-induced phase separation to obtain hydrogel composite fabric with directional conical porous structure. (3) Preparation of leaf-like hydrogel composite fabrics: The cone-shaped porous hydrogel composite fabric obtained in step (2) is immersed in a hygroscopic salt solution and left to stand to obtain a leaf-like hydrogel composite fabric.

[0031] [Beneficial Effects] This invention provides a leaf-like hydrogel composite fabric and its preparation method. The method involves preparing a printing paste by compounding colorants and printing it on the fabric to obtain a green fabric that can simulate the visible light spectrum characteristics of plant leaves. Subsequently, sodium alginate solution is injected into a mold, and the green fabric is laid on its surface and left to stand for a certain period of time. Then, an acidic solution is added, and a hydrogel composite fabric with an oriented conical porous structure is obtained through an acid-induced phase separation process. Finally, the fabric is immersed in a hygroscopic salt solution for a certain period of time to obtain the leaf-like hydrogel composite fabric. The leaf-like hydrogel composite fabric prepared by this invention can simultaneously simulate the spectral characteristics and transpiration of plant leaves, with a spectral correlation coefficient of 0.982 with that of real osmanthus leaves. The hydrogel contained in this biomimetic material has a directional conical pore structure, which can form an asymmetric Laplace pressure difference within the structure, effectively inhibiting the loss of hygroscopic salts and significantly improving the stability of the material in multiple hygroscopic-desorption cycles. Simultaneously, relying on the synergistic effect of the internal conical porous hydrogel and hygroscopic salts, the material can achieve rapid self-driven water absorption / release according to changes in ambient temperature and humidity, efficiently simulating the transpiration of plant leaves, and effectively enhancing the practical application value of this biomimetic material in the field of camouflage.

[0032] Furthermore, the biomimetic material prepared by this invention has a simple structure and a convenient preparation process, and has good prospects for industrial application. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of the leaf-like hydrogel composite fabric of the present invention; Figure 2 This is a schematic diagram of the moisture absorption-desorption process of the leaf-like hydrogel composite fabric of the present invention; Figure 3This is a schematic diagram comparing the moisture absorption-desorption cycle curves of the leaf-like hydrogel composite fabrics prepared in Example 1, Comparative Example 3, and Comparative Example 4 of the present invention. Detailed Implementation

[0034] 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.

[0035] This invention relates to the following test methods: (1) Reflectance spectral curve The sample was placed in the solid reflectance sample test chamber of the Lambda 950 UV-Vis-NIR spectrophotometer, and the reflectance spectrum of the sample was measured in the range of 400~2500 nm with a wavelength interval of 10 nm.

[0036] (2) Spectral correlation coefficient ( γ ) The spectral correlation coefficient between the sample and the green plant leaves was calculated according to Equation 1.

[0037] (Equation 1) In the formula, p The sample spectral vector; q The reference standard spectral vector; The average spectrum; For covariance; The standard deviation is denoted as .

[0038] Example 1 A method for preparing leaf-like hydrogel composite fabric includes the following steps: (1) Preparation of green fabrics: The colorant, printing auxiliary agent, and water are mixed evenly and stirred until a paste is formed to obtain a green printing paste. The mass fractions of each component in the printing paste are as follows: Disperse Blue NP-SBG 0.6%, Disperse Dark Blue HGL 0.28%, Disperse Orange 30 0.50%, Dispersant 85A 1.38%, and Thickener DM. 5221G 6%, the remainder is water, and the sum of the mass fractions of the above components is 100%; The green printing paste was printed onto the surface of polyester fabric by flat screen printing. It was pre-baked at 80 °C for 5 min, baked at 180 °C for 2 min, reduced and washed at 80 °C for 10 min, and then dried at 80 °C to obtain the green fabric. (2) Preparation of cone-shaped porous hydrogel composite fabric: Add 4 g of sodium alginate powder to 96 g of water and stir at 25 °C and 3000 rpm for 10 h until the powder is completely dissolved. Let stand for 12 h to obtain a uniform sodium alginate solution with a mass fraction of 4%. Add 15 g of 2-acrylamide-2-methylpropanesulfonic acid powder to 85 g of water and stir at 25 °C and 1000 rpm for 10 min until the powder is completely dissolved to obtain a uniform acidic solution with a mass fraction of 15%. Add 10 mL of sodium alginate solution to a mold and spread it flat. Place the green fabric obtained in step (1) on its surface and let stand for 30 min. Then add 20 mL of acidic solution and let stand at room temperature for 10 h to obtain a hydrogel composite fabric with an oriented conical porous structure. (3) Preparation of leaf-like hydrogel composite fabrics: Add 10 g LiCl to 90 g water and stir at 25 °C and 1000 rpm for 10 min until the powder is completely dissolved to obtain a uniform hygroscopic salt solution with a mass fraction of 10%. Immerse the hydrogel composite fabric obtained in step (2) in the hygroscopic salt solution and let it stand for 12 h to obtain a leaf-like hydrogel composite fabric.

[0039] Example 2 A method for preparing leaf-like hydrogel composite fabric includes the following steps: (1) Preparation of green fabrics: The colorant, printing auxiliary agent, and water are mixed evenly and stirred until a paste is formed to obtain a green printing paste. The mass fractions of each component in the printing paste are 3% chromium oxide, 2% dispersant 85A, and DM thickener. The printing paste consists of 6% 5221G, 30% DM 5128A adhesive, and the remainder is water. The total mass fraction of the above components is 100%. The printing paste is printed onto the surface of polyester fabric by flat screen printing and dried at 80 °C to obtain green fabric. (2) Preparation of cone-shaped porous hydrogel composite fabric: Same as step (2) in Example 1; (3) Preparation of leaf-like hydrogel composite fabrics: Same as step (3) in Example 1.

[0040] Example 3 A method for preparing leaf-like hydrogel composite fabric includes the following steps: (1) Preparation of green fabrics: Same as step (1) in Example 1; (2) Preparation of cone-shaped porous hydrogel composite fabric: Add 4 g of sodium alginate powder to 96 g of water and stir at 25 °C and 3000 rpm for 10 h until the powder is completely dissolved. Let stand for 12 h to obtain a uniform sodium alginate solution with a mass fraction of 4%. Add 25 g of 2-acrylamide-2-methylpropanesulfonic acid powder to 75 g of water and stir at 25 °C and 1000 rpm for 10 min until the powder is completely dissolved to obtain a uniform acidic solution with a mass fraction of 25%. Add 10 mL of sodium alginate solution to a mold and spread it flat. Place the green fabric obtained in step (1) on its surface and let stand for 30 min. Then add 20 mL of acidic solution and let stand at room temperature for 10 h to obtain a hydrogel composite fabric with an oriented conical porous structure. (3) Preparation of leaf-like hydrogel composite fabrics: Same as step (3) in Example 1.

[0041] Comparative Example 1 A method for preparing leaf-like hydrogel composite fabric includes the following steps: (1) Preparation of green fabrics: Same as step (1) in Example 1; (2) Preparation of cone-shaped porous hydrogel composite fabric: Add 4 g of sodium alginate powder to 96 g of water and stir at 25 °C and 3000 rpm for 10 h until the powder is completely dissolved. Let stand for 12 h to obtain a uniform sodium alginate solution with a mass fraction of 4%. Add 5 g of 2-acrylamide-2-methylpropanesulfonic acid powder to 95 g of water and stir at 25 °C and 1000 rpm for 10 min until the powder is completely dissolved to obtain a uniform acidic solution with a mass fraction of 5%. Add 10 mL of sodium alginate solution to a mold and spread it flat. Place the green fabric obtained in step (1) on its surface and let stand for 30 min. Then add 20 mL of acidic solution and let stand at room temperature for 10 h to obtain a hydrogel composite fabric with an oriented conical porous structure. (3) Preparation of leaf-like hydrogel composite fabrics: Same as step (3) in Example 1.

[0042] Comparative Example 2 A method for preparing leaf-like hydrogel composite fabric includes the following steps: (1) Preparation of green fabrics: Same as step (1) in Example 1.

[0043] (2) Preparation of hydrogel composite fabrics: Add 4 g of sodium alginate powder to 96 g of water and stir at 25 °C and 3000 rpm for 10 h until the powder is completely dissolved. Let stand for 12 h to obtain a uniform sodium alginate solution with a mass fraction of 4%. Add 15 g of anhydrous acetic acid to 85 g of water and stir at 25 °C and 1000 rpm for 10 min to obtain a uniform acetic acid solution with a mass fraction of 15%. Add 10 mL of sodium alginate solution to a mold and spread it flat. Place the green fabric obtained in step (1) on its surface and let it stand for 30 min. Then add 20 mL of acetic acid solution and let it stand at room temperature for 10 h to obtain the product. Observe its state.

[0044] Comparative Example 3 The biomimetic material for blades prepared according to patent CN114214847A includes the following steps: (1) Preparation of green fabrics: Same as step (1) in Example 1; (2) Preparation of hydrogel prepolymer solution: Add 1.0 g of sodium alginate powder to 100 mL of water and stir thoroughly until completely dissolved to obtain an aqueous solution of sodium alginate; add 10 g of calcium chloride to 90 g of water and mix well to obtain a calcium chloride solution with a mass fraction of 10%. (3) Preparation of biomimetic materials: Cut the green fabric obtained in step (1) to a suitable size and place it in a mold. Add the sodium alginate aqueous solution obtained in step (2) to make it 3 mm thick. Then spray the calcium chloride solution obtained in step (2) to make it 6 mm thick. Let it stand at room temperature for 30 min, and then dry it at 50 °C for 24 h to obtain the leaf biomimetic material.

[0045] Comparative Example 4 The biomimetic material for blades prepared according to patent CN119529317B includes the following steps: (1) Preparation of green fabrics: Same as step (1) in Example 1; (2) Preparation of hydrogel prepolymer solution: 20 g of 1788 low-viscosity polyvinyl alcohol was added to 80 g of water, stirred at 90°C until completely dissolved, and cooled to room temperature to obtain a 20% polyvinyl alcohol solution. The polyvinyl alcohol solution, 2-acrylamide-2-methylpropanesulfonic acid, N,N-methylenebisacrylamide, ammonium persulfate, and water were mixed and stirred until homogeneous. The mixture was then purged with nitrogen for 20 min to prepare a hydrogel prepolymer solution. The mass fractions of each component in the prepolymer solution were: 60% polyvinyl alcohol solution, 20% 2-acrylamide-2-methylpropanesulfonic acid, 0.7% N,N-methylenebisacrylamide, 0.6% ammonium persulfate, and the remainder was water. The sum of the mass fractions of all components was 100%. (3) Preparation of biomimetic materials: The green fabric obtained in step (1) was cut to a size of 10 cm * 10 cm and laid flat in a mold. 15 mL of the hydrogel prepolymer solution obtained in step (2) was added, and the mixture was polymerized at 60 °C for 12 h to obtain the leaf biomimetic material.

[0046] Comparative Example 5 A method for preparing leaf-like hydrogel composite fabric includes the following steps: (1) Preparation of green fabrics: Same as step (1) in Example 1.

[0047] (2) Preparation of hydrogel composite fabrics: Add 4 g of sodium alginate powder to 96 g of water and stir at 25 °C and 3000 rpm for 10 h until the powder is completely dissolved. Let stand for 12 h to obtain a uniform sodium alginate solution with a mass fraction of 4%. Add 15 g of acrylamide powder to 85 g of water and stir at 25 °C and 1000 rpm for 10 min until the powder is completely dissolved to obtain a uniform acrylamide solution with a mass fraction of 15%. Add 10 mL of sodium alginate solution to a mold and spread it flat. Place the green fabric obtained in step (1) on its surface and let it stand for 30 min. Then add 20 mL of acrylamide solution and let it stand at room temperature for 10 h to obtain the product. Observe its state.

[0048] Comparative Example 6 A method for preparing leaf-like hydrogel composite fabric includes the following steps: (1) Preparation of green fabrics: Same as step (1) in Example 1.

[0049] (2) Preparation of hydrogel composite fabrics: Add 4 g of sodium alginate powder to 96 g of water and stir at 25 °C and 3000 rpm for 10 h until the powder is completely dissolved. Let stand for 12 h to obtain a uniform sodium alginate solution with a mass fraction of 4%. Add 15 g of sodium p-styrene sulfonate powder to 85 g of water and stir at 25 °C and 1000 rpm for 10 min until the powder is completely dissolved to obtain a uniform sodium p-styrene sulfonate solution with a mass fraction of 15%. Add 10 mL of sodium alginate solution to a mold and spread it flat. Place the green fabric obtained in step (1) on its surface and let stand for 30 min. Then add 20 mL of sodium p-styrene sulfonate solution and let stand at room temperature for 10 h to obtain the product. Observe its state.

[0050] Results Analysis 1. The morphology and pore size of the biomimetic materials prepared in the examples and comparative examples were described and measured. The results are shown in Table 1: Table 1. Morphology and pore size of different biomimetic materials

[0051] 2. Calculate the spectral correlation coefficient of the biomimetic materials prepared in the examples and comparative examples. The biomimetic materials prepared in the examples and comparative examples were placed at 25 °C and 60% relative humidity (RH) for 24 h to reach moisture equilibrium, and then spectral tests were performed. The spectral correlation coefficient between the materials and osmanthus leaves was calculated according to Equation 1. The results are shown in Table 2. Table 2. Spectral correlation coefficients between different biomimetic materials and osmanthus leaves

[0052] 3. The moisture absorption rate of the biomimetic materials prepared in the examples and comparative examples was measured. The biomimetic materials prepared in the examples and comparative examples were dried at 60 °C, and then placed at 25 °C and humidity levels of 30%, 60%, and 90% RH for 3 h for moisture absorption tests. The moisture absorption rate was calculated, and the results are shown in Table 3. Table 3. Moisture absorption rates of different biomimetic materials under different humidity levels.

[0053] 4. The photothermal desorption rate of the biomimetic materials prepared in the examples and comparative examples was measured. The biomimetic materials prepared in the examples and comparative examples were placed at 25 °C and 90% RH for 24 h to absorb moisture, and then placed at 1 kW m at 25 °C and 30% RH. -2 After irradiation under a xenon lamp for 6 hours, the desorption rate of each material was calculated, and the results are shown in Table 4. Table 4. Photothermal desorption rates of different biomimetic materials

[0054] 5. The hygroscopic-desorption cycle stability of the biomimetic materials prepared in the examples and comparative examples was determined. The biomimetic materials prepared in Examples 1, 3, and 4 were placed at 25 °C and 90% RH for 24 h to reach moisture equilibrium. Then, the materials were dried at 120 °C for 12 h, constituting one moisture absorption-desorption cycle. A total of 10 moisture absorption-desorption cycles were then performed. The moisture absorption of each material was calculated, and the results are as follows: Figure 3 As shown.

[0055] Analysis of the above results shows that, compared with Example 1 and Example 2, although the leaf-like hydrogel composite fabrics prepared with different colorants have slight differences in color, both show high spectral similarity to osmanthus leaves.

[0056] Comparative examples 1, 3, and 2 show that the concentration and type of acidic solution have a significant impact on the gelation process and pore structure of sodium alginate solution. By controlling the concentration of the acidic solution, hydrogel composite fabrics with different morphologies can be prepared, thus enabling customized production according to actual application requirements. Furthermore, only specific acidic solutions can cause sodium alginate solution to form a hydrogel.

[0057] Comparing Example 1 and Comparative Example 3, it can be seen that the hydrogel composite fabric with directional conical channel structure has excellent performance in preventing salt solution leakage. After 10 moisture absorption-desorption cycle tests, its moisture absorption did not change significantly, ensuring the reliability of the material in long-term use.

[0058] Comparing Example 1 and Comparative Example 4, it can be seen that although both have good hygroscopic-desorption cycle stability, the biomimetic material prepared in Example 1 shows a faster hygroscopic and desorption rate based on the synergistic effect of the internal conical porous hydrogel and hygroscopic salt. It achieves a rapid response to changes in environmental temperature and humidity, efficiently simulates the transpiration of plant leaves, and effectively enhances the practical application value of the biomimetic material in the field of camouflage.

[0059] Comparative Examples 1, 5, and 6 show that acrylamide and sodium p-styrene sulfonate cannot induce sodium alginate solution to form a hydrogel, while 2-acrylamide-2-methylpropanesulfonic acid can induce sodium alginate solution to form a hydrogel through the hydrogen ions generated by the ionization of its aqueous solution. Finally, a leaf-like hydrogel composite fabric with a conical porous structure was successfully prepared.

[0060] 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 method for preparing leaf-like hydrogel composite fabrics, characterized in that, The method includes the following steps: (1) Preparation of green fabrics: The colorant, printing auxiliary agent and water are mixed evenly and stirred until they become a paste to obtain the printing paste; then the printing paste is printed onto the surface of the fabric using screen printing to obtain green fabric. (2) Preparation of cone-shaped porous hydrogel composite fabric: Prepare uniform sodium alginate solution and acidic solution respectively. After injecting sodium alginate solution into the mold, lay the green fabric obtained in step (1) on its surface and let it stand for a certain time. Then add acidic solution and let it stand for acid-induced phase separation to obtain hydrogel composite fabric with directional conical porous structure. The acidic solution is obtained by mixing an acidic substance with water and stirring until homogeneous; The acidic substances include one or more of 2-acrylamide-2-methylpropanesulfonic acid, hydrochloric acid, and sulfuric acid; (3) Preparation of leaf-like hydrogel composite fabrics: The cone-shaped porous hydrogel composite fabric obtained in step (2) is immersed in a hygroscopic salt solution and left to stand to obtain a leaf-like hydrogel composite fabric.

2. The method according to claim 1, characterized in that, The colorant mentioned in step (1) includes one or more of chromium oxide, disperse dye, vat dye, acid dye, reactive dye, dried leaf powder, and sodium copper chlorophyll.

3. The method according to claim 1, characterized in that, The sodium alginate solution described in step (2) is prepared by mixing sodium alginate powder with water to form a slurry; wherein the amount of sodium alginate powder in the sodium alginate solution is 1~5wt.

4. The method according to claim 1, characterized in that, The acidic solution described in step (2) is obtained by mixing an acidic substance with water and stirring until homogeneous; wherein the amount of the acidic substance in the acidic solution is 10~30 wt.

5. The method according to claim 1, characterized in that, In step (2), the volume ratio of sodium alginate solution to acidic solution in the mold is 1:(1~3).

6. The method according to claim 1, characterized in that, The conditions for the acid-induced phase separation in step (2) are: temperature 20~40 °C and time 6~12 h.

7. The method according to claim 1, characterized in that, The hygroscopic salt solution in step (3) is obtained by mixing hygroscopic salt and water and stirring evenly; wherein the amount of hygroscopic salt in the hygroscopic salt solution is 1~35 wt.

8. The leaf-like hydrogel composite fabric prepared by the method according to any one of claims 1 to 7.

9. The application of the leaf-like hydrogel composite fabric according to claim 8 in the field of camouflage.

10. A method for improving the rapid response capability and moisture absorption cycle stability of leaf-like hydrogel composite fabrics, characterized in that, The method includes the following steps: (1) Preparation of green fabrics: The colorant, printing auxiliary agent and water are mixed evenly and stirred until they become a paste to obtain the printing paste; then the printing paste is printed onto the surface of the fabric using screen printing to obtain green fabric. (2) Preparation of cone-shaped porous hydrogel composite fabric: Prepare uniform sodium alginate solution and acidic solution respectively. After injecting sodium alginate solution into the mold, lay the green fabric obtained in step (1) on its surface and let it stand for a certain time. Then add acidic solution and let it stand for acid-induced phase separation to obtain hydrogel composite fabric with directional conical porous structure. The acidic solution is obtained by mixing an acidic substance with water and stirring until homogeneous; The acidic substances include one or more of 2-acrylamide-2-methylpropanesulfonic acid, hydrochloric acid, and sulfuric acid; (3) Preparation of leaf-like hydrogel composite fabrics: The cone-shaped porous hydrogel composite fabric obtained in step (2) is immersed in a hygroscopic salt solution and left to stand to obtain a leaf-like hydrogel composite fabric.

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