Bionic hydrogel based on rolling stress field multi-scale regulation and control and preparation method thereof

Abstract

The invention discloses bionic hydrogel based on calendering stress field multi-scale regulation and control and a preparation method thereof.According to the method, a calendering forming technology under the solvent-free and low-temperature condition is innovatively adopted, a shearing-compression coupling stress field is precisely regulated and controlled, and PVA hydrogel subjected to freeze-thawing pre-forming is processed; the PVA molecular chain is synergistically induced to generate orientation, nanocrystalline domain reconstruction and layered structure assembly on the molecular, nanometer and macroscopic scale, so that the bionic hydrogel with a stable anisotropic structure is constructed. The method does not need a chemical cross-linking agent or an organic solvent, and is green and safe. The obtained hydrogel shows excellent mechanical strength and toughness while maintaining the ultra-high water content of more than 90 wt%. In addition, the damaged or waste hydrogel can be efficiently recycled and regenerated in performance through the process. The invention provides an efficient, sustainable and large-scale preparation platform, and has wide application prospects in the fields of biomedicine, environmental engineering and the like.

Description

Technical Field

[0001] This invention belongs to the field of functional polymer materials technology, specifically relating to a biomimetic hydrogel based on multi-scale control of calendering stress field and its preparation method. Background Technology

[0002] Hydrogels are highly hydrated soft materials with a three-dimensional network structure. Due to their excellent flexibility, hydrophilicity, and biocompatibility, they have shown broad application prospects in cutting-edge fields such as tissue engineering, implantable electronic devices, wearable sensors, and soft robotics. However, the polymer chains inside traditional hydrogels tend to form a non-uniform and loose network structure in an aqueous environment, resulting in problems such as low mechanical strength, easy crack propagation, poor toughness, and poor fatigue resistance (Ni J. et al., Matter, 2021), which seriously restricts their promotion in high-strength or high-load mechanical applications.

[0003] To overcome these shortcomings, researchers have proposed various strategies to enhance the mechanical properties of hydrogels. For example, dual-network hydrogels significantly improve toughness by constructing a synergistic structure of rigid and flexible networks and introducing multiple energy dissipation mechanisms (Gong J. et al., Advanced Materials, 2003). Solvent replacement and salting-out techniques can enhance network density by regulating the conformation of macromolecular chains and promoting crystalline region formation, thereby obtaining ultra-tough and fatigue-resistant hydrogels (Wu Y. et al., Advanced Materials, 2023). In addition, the introduction of nanoreinforcement materials such as carbon nanotubes and aramid nanofibers can effectively transfer loads through hydrogen bonding and interfacial synergistic effects, which can also improve the overall mechanical properties of composite hydrogels (Liu Z. et al., Composites Science and Technology, 2024).

[0004] Compared to isotropic structures, constructing anisotropic hydrogels with macroscopic orientation has been proven to be an effective way to simultaneously improve the strength and functional responsiveness of materials. Currently, techniques such as directional freezing, mechanical stretching, and shear field treatment have been widely used to induce polymer chains to align in specific directions, thereby significantly enhancing the strength and toughness of hydrogels in the orientation direction (Han Z. et al., Advanced Functional Materials, 2024). However, due to the stress relaxation and entropy elastic recoil characteristics of molecular chains, effectively locking and maintaining the orientation structure during preparation remains a technical challenge. To address this issue, researchers have attempted to combine directional freezing with salting out to improve orientation stability and mechanical properties by promoting densification of crystalline regions and enhancing inter-chain interactions (Liang X. et al., Advanced Materials, 2021); other studies have used methods such as restricted drying and mechanical training to construct stable multi-scale fiber structures to simulate the fatigue resistance of muscles (Lin S. et al., PNAS, 2019).

[0005] While the aforementioned methods improve the mechanical properties of hydrogels to some extent, this enhancement often comes at the cost of high water content. However, in many critical applications such as biomedical engineering and extracellular matrix simulation, high water content (typically >90 wt%) is essential for maintaining good biocompatibility and promoting the diffusion and exchange of nutrients and metabolic waste. Therefore, synergistically unifying high water content with excellent mechanical properties has become one of the core challenges that urgently need to be addressed in the field of hydrogels.

[0006] Furthermore, existing research largely focuses on the synthesis and structural design of hydrogels, with insufficient attention paid to their recyclability at the end of their life cycle. As the application of hydrogel-based devices becomes increasingly widespread, the disposal of their waste will bring environmental pressure. Achieving efficient recycling and reuse of hydrogel materials would not only meet the requirements of green and sustainable development but also significantly enhance their application value and economic viability throughout their entire life cycle.

[0007] In summary, current technology lacks a green preparation method for hydrogels that can simultaneously achieve high strength, high toughness, stable anisotropic structure, and good recyclability while maintaining a high water content (>90 wt%). Developing such hydrogel materials with excellent comprehensive properties is urgently needed and of great significance for promoting their practical applications in fields such as life sciences and green manufacturing. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a biomimetic hydrogel based on multi-scale control of calendering stress field and its preparation method. This method, through an innovative solvent-free, low-temperature calendering process, effectively solves the technical bottleneck of traditional hydrogels in balancing mechanical strength, high water content, and environmental friendliness. The process of this invention employs a mechanical coupling strategy of synergistic shear and compressive forces acting on the primary PVA hydrogel formed through freeze-thaw treatment, achieving multi-level directional arrangement of PVA chains at the molecular, nanoscale, and macroscale levels, thereby constructing a hydrogel network with a biomimetic layered structure and significantly anisotropic mechanical properties.

[0009] This invention is achieved through the following technical solution:

[0010] A method for preparing a biomimetic hydrogel based on multi-scale control of calendering stress field includes the following steps:

[0011] Step 1) Add PVA powder to H2O, heat and stir, let stand to eliminate bubbles, and obtain a uniform polymer solution;

[0012] Step 2) The polymer solution obtained in Step 1) is cast into a mold and then subjected to a freeze-thaw cycle to construct a physically cross-linked hydrogel with an isotropic structure;

[0013] Step 3) Place the physically cross-linked hydrogel obtained from the freeze-thaw process in step 2) between the two rollers of a small calender for calendering;

[0014] Step 4) Immerse the hydrogel after calendering in step 3) in H2O to achieve equilibrium swelling and obtain anisotropic hydrogel, which is the biomimetic hydrogel.

[0015] Preferably, in step 1), the mass fraction of PVA in the polymer solution is 15%; the heating and stirring time is 5 h and the temperature is 100℃; the standing time is 1 h.

[0016] Preferably, the mold in step 2) is made of polytetrafluoroethylene; the mold needs to be pretreated before casting as follows: place the mold in an oven and heat it at 80°C for 2 hours; the specific parameters of the freeze-thaw cycle are: freezing time is 8 hours, thawing time at room temperature is 3 hours, and the number of cycles is 3; the thickness of the physically cross-linked hydrogel is 1.1~1.2 mm.

[0017] Preferably, the calendering process in step 3) is performed at a temperature of 37°C, a roll gap of 0.6 / 0.3 mm, and a time of 12 min.

[0018] Preferably, the immersion time in H2O in step 4) is 24 h.

[0019] Preferably, the process also includes step 5), which involves placing the waste or damaged biomimetic hydrogel between two rollers for calendering and recycling, and then immersing it in H2O to achieve balanced swelling, thereby obtaining a recyclable biomimetic hydrogel.

[0020] Preferably, the temperature of the calendering recycling process in step 5) is 60°C, the roll gap is 0.3 mm, and the time is 5 min; the immersion time in H2O is 12 h.

[0021] Preferably, in step 5), the biomimetic hydrogel softens and adheres to the roller surface to form a PVA film, and then the PVA film is folded multiple times for calendering.

[0022] Preferably, step 5) can be repeated, with the number of repetitions being ≥1.

[0023] The biomimetic hydrogel prepared by the above method.

[0024] The beneficial effects of this invention are as follows:

[0025] (1) The "solvent-free and toxic chemical crosslinking agent-free" end-to-end green manufacturing platform established in this invention fundamentally eliminates the environmental and biosafety problems that may be caused by residual organic solvents and toxic crosslinking agents. The preparation process has low energy consumption and conforms to the principles of green chemistry. More importantly, this invention successfully constructs a closed-loop recycling and performance reconstruction strategy for PVA hydrogels, enabling waste materials to be efficiently recycled. Moreover, the key mechanical properties of the recycled hydrogels (such as tensile strength, fracture strain, and toughness) not only do not decrease but are even better than those of the original samples. This characteristic greatly improves the sustainability and resource utilization efficiency of the material throughout its entire life cycle, providing a new paradigm for solving the problem of polymer material waste.

[0026] (2) This invention achieves precise control of multi-scale structure through an innovative low-temperature calendering process, and for the first time in the laboratory, combines an ultra-high water content of approximately 90.2% with excellent mechanical properties. The resulting anisotropic hydrogel has a tensile strength of up to 3.20 MPa, a Young's modulus of 3.70 MPa, and a fracture toughness of 2.45 MJ·m. -3 Especially its 187.6 J·m -2 The high fatigue threshold indicates its excellent resistance to crack propagation. This combination of properties successfully solves the core contradiction that traditional high-performance hydrogels often require sacrificing water content, laying the material foundation for the application of hydrogels in harsh environments requiring high water content, such as biomedical applications.

[0027] (3) The core of this invention lies in employing a "mechanical coupling strategy" (coordination of shear force and compressive force) to perform low-temperature calendering on the primary gel formed by freeze-thaw cycles. This method avoids complex equipment and harsh conditions, and efficiently realizes the multi-level directional arrangement of PVA molecular chains from the molecular to the macroscopic scale, thereby constructing a stable anisotropic network with a biomimetic layered structure. This structure not only endows the hydrogel with enhanced mechanical properties of directionality, but also avoids the irreversibility caused by chemical cross-linking because it mainly relies on physical interactions, thus creating conditions for subsequent recyclability.

[0028] (4) The freeze-thaw-calendering process used in this invention is simple, mild, requires no special or expensive equipment, and is easy to scale up and achieve large-scale production. This simple and efficient preparation and recycling method makes this high-performance, renewable PVA hydrogel material have great industrial application prospects and promotion value in many fields such as biomedical materials (such as artificial cartilage and ligaments), flexible electronic devices (such as wearable sensors), and environmental engineering (such as adsorption materials). Attached Figure Description

[0029] Figure 1 This is a schematic diagram illustrating the preparation of the biomimetic hydrogel based on multi-scale control of calendering stress field according to the present invention;

[0030] Figure 2 Scanning electron microscope (SEM) images of the hydrogels: a) Example 1; b) Example 2; c) Comparative Example 1;

[0031] Figure 3 A summary graph showing the water content of the hydrogels prepared in Examples 1, 2 and Comparative Example 1;

[0032] Figure 4 The stress-strain curves of the hydrogels prepared in Examples 1 and 2 (including two directions parallel and perpendicular to the orientation) and Comparative Example 1 are shown.

[0033] Figure 5 The tensile strength / elongation at break (a) and Young's modulus / toughness (b) of the hydrogels prepared in Examples 1 and 2 (including two directions parallel and perpendicular to the orientation) and Comparative Example 1 are summarized in the figure.

[0034] Figure 6 The following are cyclic tensile-recovery stress-strain curves of the hydrogel: a is Comparative Example 1; b is Example 2; c is Example 1.

[0035] Figure 7 The fatigue threshold diagrams for hydrogels are as follows: a) Comparative Example 1; b) Example 2; c) Example 1.

[0036] Figure 8 This is a flowchart illustrating the recycling process of waste or damaged hydrogel in Example 3;

[0037] Figure 9 This is a schematic diagram of PVA closed-loop recycling in Example 3;

[0038] Figure 10 Stress-strain curves of the hydrogels prepared in Examples 3-5;

[0039] Figure 11 The tensile strength, elongation at break, and toughness of the hydrogels prepared in Examples 3-5 are summarized in the figure. Detailed Implementation

[0040] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0041] Unless otherwise specified, the technical means used in the following embodiments are all conventional means well known to those skilled in the art, and the experimental methods without specific conditions are all conventional methods in the art.

[0042] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0043] Example 1

[0044] 1. Preparation of anisotropic hydrogels

[0045] A method for preparing biomimetic hydrogels based on multi-scale control of calendering stress field, such as... Figure 1 As shown, the specific steps are as follows:

[0046] (1) Dissolve 7.5 g of PVA powder in 42.5 g of deionized water (PVA concentration is 15wt.%), heat and stir at 100℃ for 5 h, and then let stand for 1 h to eliminate bubbles to obtain a uniform polymer solution;

[0047] (2) While the polymer solution is hot, pour it into a polytetrafluoroethylene mold that has been preheated (the mold is placed in an oven and heated at 80°C for 2 hours). Then place the mold in a freezer at -20°C for 8 hours and thaw it at room temperature for 3 hours. Repeat the freeze-thaw cycle 3 times to obtain a physically cross-linked freeze-thaw hydrogel with an isotropic structure and a thickness of 1.1~1.2 mm.

[0048] (3) Place the freeze-thawed hydrogel between the two rollers of a small calender (roll gap 0.3 mm, roller temperature 37°C, time 12 min) for calendering.

[0049] (4) Finally, the calendered hydrogel is immersed in deionized water for 24 h to achieve equilibrium swelling and obtain anisotropic hydrogel, which is the biomimetic hydrogel.

[0050] 2. Morphological observation

[0051] The anisotropic hydrogel prepared in this embodiment was observed using a scanning electron microscope.

[0052] Observation results as follows Figure 2 As shown in Figure a, the anisotropic hydrogels obtained by calendering exhibit a gradually ordered layered structure arranged along the shear direction, reflecting the effective orientation of PVA macromolecular chains under the applied mechanical field. The presence of shear and compressive forces during calendering leads to a decrease in hydrogel thickness and an increase in structural regularity. The smaller roll gap results in a smaller pore size of the hydrogel, exhibiting neatly arranged micron-sized fibers. Despite their compact and neatly arranged layered morphology, the anisotropic hydrogels still retain significant porosity. These morphological characteristics, namely the combination of layered arrangement and retained porosity, endow the hydrogels with the ability to maintain high water content while achieving mechanical anisotropy. Figure 3 The reduced aperture and well-organized microstructure promise to improve load transfer efficiency, providing a structural basis for improved mechanical properties.

[0053] 3. Mechanical performance testing

[0054] The anisotropic hydrogel prepared in this embodiment was subjected to uniaxial tensile testing using a general tensile testing machine, and cyclic tensile-recovery and fatigue testing using a fatigue tensile testing machine.

[0055] The test results of uniaxial tensile stress-strain curves are as follows: Figure 4 , 5 As shown, the anisotropic hydrogel prepared in this embodiment has tensile strength, Young's modulus, and toughness parallel to the orientation direction of 3.20±0.77 MPa, 3.70±1.37 MPa, and 2.45±0.68 MJ·m, respectively. -3 The differences in mechanical properties in the two directions are 5.6 times, 21.8 times, and 2.2 times that in the vertical direction, respectively. The huge difference in mechanical properties in the two directions confirms that the calendering process effectively promotes the orderly arrangement of PVA molecular chains and the densification of the three-dimensional network structure through the dual mechanism of synergistic mechanical orientation effect and dehydration.

[0056] The test results of the cyclically increasing tensile-recovery stress-strain curve are as follows: Figure 6 As shown in Figure c, the anisotropic hydrogel prepared in this embodiment exhibits tensile hardening properties. At the 15th cycle (0–100% strain), its initial maximum stress increased by 56%. This unique mechanical memory effect originates from the strain-induced hierarchical orientation of the PVA nanofibers, which creates self-reinforcing pathways during cyclic deformation.

[0057] The results of single-notch fatigue testing are as follows: Figure 7 As shown in Figure c, the fatigue threshold of the anisotropic hydrogel prepared in this embodiment reaches 187.6 J·m.-2 This significant performance improvement is mainly attributed to the multi-level microstructure formed inside the hydrogel: highly oriented and densely packed PVA nanofibers and submicron bundles constitute a hierarchical energy dissipation network, which can effectively disperse stress concentration under cyclic loading and achieve notch passivation.

[0058] Example 2

[0059] 1. Preparation of anisotropic hydrogels

[0060] A method for preparing biomimetic hydrogels based on multi-scale control of calendering stress field is described. The specific preparation steps are the same as in Example 1, except that the roller gap is set to 0.6 mm.

[0061] 2. Morphological observation

[0062] The anisotropic hydrogel prepared in this embodiment was observed using a scanning electron microscope.

[0063] Observation results as follows Figure 2 As shown in Figure b, a larger gap leads to a slight increase in the pore size of the hydrogel and a poorer network density, but the ordered arrangement of nanofibers can still be clearly observed.

[0064] 3. Mechanical performance testing

[0065] The anisotropic hydrogel prepared in this embodiment was subjected to uniaxial tensile testing using a general tensile testing machine, and cyclic tensile-recovery and fatigue testing using a fatigue tensile testing machine.

[0066] The test results of uniaxial tensile stress-strain curves are as follows: Figure 4 , 5 As shown, the anisotropic hydrogel prepared in this embodiment has tensile strength, Young's modulus, and toughness parallel to the orientation direction of 0.82±0.04 MPa, 0.85±0.06 MPa, and 0.55±0.04 MJ·m, respectively. -3 The values ​​are 2.9 times, 7.7 times, and 1.1 times that in the vertical direction, respectively, which are significantly lower than the anisotropic hydrogel prepared in Example 1.

[0067] The test results of the cyclically increasing tensile-recovery stress-strain curve are as follows: Figure 6 As shown in Figure b, the anisotropic hydrogel prepared in this embodiment exhibits significant mechanical hysteresis in the first cycle due to its poor orientation, dissipating a large amount of energy and demonstrating the Mullins effect.

[0068] The results of single-notch fatigue testing are as follows: Figure 7 As shown in Figure b, the anisotropic hydrogel prepared in this embodiment has a fatigue threshold of 57.5 J·m. -2The value was significantly lower than that of the anisotropic hydrogel prepared in Example 1.

[0069] Example 3

[0070] 1. Preparation of primary recycled hydrogels

[0071] like Figure 8 , 9 As shown, the discarded or damaged hydrogel (15 wt.%) prepared in Example 1 was placed between two rollers for calendering and recycling (temperature 60°C, roller gap 0.3 mm, time 5 min). The hydrogel softened and adhered to the roller surface to form a PVA film. The PVA film was then folded multiple times and calendered. The PVA film was then immersed in deionized water for 12 h to achieve equilibrium swelling, resulting in a primary recycled hydrogel.

[0072] For subsequent recycling cycles, the same procedure is repeated.

[0073] 2. Mechanical performance testing

[0074] The primary recycled hydrogel prepared in this embodiment was subjected to uniaxial tensile testing using a general-purpose tensile testing machine.

[0075] The test results of uniaxial tensile stress-strain curves are as follows: Figure 10 , 11 As shown, the tensile strength, elongation at break, and toughness of the primary recycled hydrogel prepared in this embodiment are 4.03±0.24 MPa, 161.9±10.8%, and 2.48±0.55 MJ·m, respectively. -3 Its tensile strength and toughness even exceed those of the hydrogel prepared in Example 1.

[0076] Example 4

[0077] 1. Preparation of secondary recycled hydrogels

[0078] The specific preparation steps are the same as in Example 3, except that the discarded or damaged hydrogel obtained in Example 1 is replaced with the recycled hydrogel obtained in Example 3.

[0079] 2. Mechanical performance testing

[0080] The secondary recycled hydrogel prepared in this embodiment was subjected to uniaxial tensile testing using a general-purpose tensile testing machine.

[0081] The test results of uniaxial tensile stress-strain curves are as follows: Figure 10 , 11 As shown, the tensile strength, elongation at break, and toughness of the secondary recycled hydrogel prepared in this embodiment are 2.51±0.18 MPa, 156.8±38.1%, and 1.56±0.22 MJ·m, respectively. -3 .

[0082] Example 5

[0083] 1. Preparation of three-stage recycled hydrogels

[0084] The specific preparation steps are the same as in Example 3, except that the waste or damaged hydrogel obtained in Example 1 is replaced with the secondary recycled hydrogel obtained in Example 4.

[0085] 2. Mechanical performance testing

[0086] The three-stage recycled hydrogel prepared in this embodiment was subjected to uniaxial tensile testing using a general-purpose tensile testing machine.

[0087] The test results of uniaxial tensile stress-strain curves are as follows: Figure 10 , 11 As shown, the tensile strength, elongation at break, and toughness of the three-stage recycled hydrogel prepared in this embodiment are 2.95±0.52 MPa, 123.9±18.2%, and 1.61±0.18 MJ·m, respectively. -3 .

[0088] Comparative Example 1

[0089] 1. Preparation of freeze-thawed hydrogels

[0090] 7.5 g of PVA was dissolved in 42.5 g of deionized water (PVA concentration of 15 wt.%) and stirred at 100 °C for 5 h, then allowed to stand for 1 h to defoam. While still hot, the solution was poured into a preheated polytetrafluoroethylene mold (the mold was placed in an oven and heated at 80 °C for 2 h). The mold was then placed in a freezer at -20 °C for 8 h, and then thawed at room temperature for 3 h. This freeze-thaw cycle was repeated 3 times to obtain a physically cross-linked freeze-thaw hydrogel.

[0091] 2. Morphological observation

[0092] The morphology of the freeze-thawed hydrogel was observed using a scanning electron microscope.

[0093] Observation results as follows Figure 2 As shown in Figure c, the freeze-thawed hydrogel exhibits an interconnected but non-uniform porous structure with numerous micropores in its framework.

[0094] (3) Mechanical performance testing

[0095] Uniaxial tensile tests were performed on the freeze-thawed hydrogel using a general tensile testing machine, and cyclic tensile-recovery and fatigue tests were performed on the freeze-thawed hydrogel using a fatigue tensile testing machine.

[0096] The test results of uniaxial tensile stress-strain curves are as follows: Figure 4 , 5As shown, the tensile strength, Young's modulus, and toughness of the freeze-thawed hydrogel parallel to the orientation direction are 0.58±0.02 MPa, 0.18±0.01 MPa, and 1.20±0.12 MJ·m, respectively. -3 The value was significantly lower than that of the anisotropic hydrogel prepared in Example 1.

[0097] The test results of the cyclically increasing tensile-recovery stress-strain curve are as follows: Figure 6 As shown in Figure a, the freeze-thawed hydrogel exhibits significant mechanical hysteresis in the first cycle, dissipating the greatest energy and demonstrating the Mullins effect.

[0098] The results of single-notch fatigue testing are as follows: Figure 7 As shown in Figure a, the fatigue threshold of the freeze-thaw hydrogel is only 5.1 J·m. -2 The anisotropic hydrogels prepared in Examples 1 and 2 are significantly lower than those prepared in Examples 1 and 2.

[0099] The above experimental results show that the hydrogel prepared by freeze-thaw has a loosely physically cross-linked network structure and exhibits low mechanical strength on a macroscopic scale.

[0100] The embodiments described above are only some, not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. The scope of protection of the present invention is determined by the scope claimed in the claims. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing a biomimetic hydrogel based on multi-scale regulation of a rolling stress field, characterized by, Includes the following steps: Step 1) Add PVA powder to H2O, heat and stir, let stand to eliminate bubbles, and obtain a uniform polymer solution; Step 2) The polymer solution obtained in Step 1) is cast into a mold and then subjected to a freeze-thaw cycle to construct a physically cross-linked hydrogel with an isotropic structure; Step 3) Place the physically cross-linked hydrogel obtained from the freeze-thaw process in step 2) between the two rollers of a small calender for calendering; Step 4) Immerse the hydrogel after calendering in step 3) in H2O to achieve equilibrium swelling and obtain anisotropic hydrogel, which is the biomimetic hydrogel.

2. The method according to claim 1, wherein the method is characterized by, Step 1) The polymer solution contains 15% PVA by mass; the heating and stirring time is 5 h and the temperature is 100℃; the settling time is 1 h.

3. The method according to claim 1, wherein the method is characterized by, Step 2) The mold is made of polytetrafluoroethylene; the mold needs to be pretreated before casting as follows: place the mold in an oven and heat it at 80°C for 2 hours; the specific parameters of the freeze-thaw cycle are: freezing time is 8 hours, thawing time at room temperature is 3 hours, and the number of cycles is 3; the thickness of the physically cross-linked hydrogel is 1.1~1.2 mm.

4. The method according to claim 1, wherein the method is characterized by, Step 3) The calendering process is performed at a temperature of 37°C, a roll gap of 0.6 / 0.3 mm, and a time of 12 min.

5. The method according to claim 1, wherein the method is characterized by, Step 4) The immersion time in H2O is 24 h.

6. The method for preparing a biomimetic hydrogel based on multi-scale control of calendering stress field according to claim 1, characterized in that, It also includes step 5), which is: placing the waste or damaged biomimetic hydrogel between two rollers for calendering and recycling, and then immersing it in H2O to achieve balanced swelling, so as to obtain recyclable biomimetic hydrogel.

7. The method for preparing a biomimetic hydrogel based on multi-scale control of calendering stress field according to claim 6, characterized in that, Step 5) The calendering recycling process is carried out at a temperature of 60°C, a roll gap of 0.3 mm, and a time of 5 min; the immersion time in H2O is 12 h.

8. The method for preparing a biomimetic hydrogel based on multi-scale control of calendering stress field according to claim 6, characterized in that, In step 5), the biomimetic hydrogel softens and adheres to the roller surface to form a PVA film, and then the PVA film is folded multiple times for calendering.

9. The method for preparing a biomimetic hydrogel based on multi-scale control of calendering stress field according to claim 6, characterized in that, The operation in step 5) can be repeated, with a repetition count of ≥1.

10. The biomimetic hydrogel prepared by the preparation method according to any one of claims 1-9.

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