A negative poisson's ratio swelling and toughening hydrogel material, and a preparation method and application thereof

Abstract

The present application belongs to the technical field of polymer materials, and particularly relates to a negative Poisson's ratio swelling and toughening hydrogel material and a preparation method and application thereof. The hydrogel material comprises a fiber skeleton and a hydrogel bonded to the fiber skeleton, and the fiber skeleton has a cosine wave negative Poisson's ratio structure, specifically a periodic structure formed by cosine curves staggered in horizontal and vertical directions. By adjusting the preparation parameters of the cosine wave fiber, the specific surface area of the fiber is large and the swelling effect is obvious, the fiber and the hydrogel form rich covalent grafting, and the cosine wave negative Poisson's ratio structure fiber drives the molecular chains of the hydrogel to be oriented and arranged to form an ordered structure when subjected to tension, so that the strength and toughness of the hydrogel are effectively improved. The prepared negative Poisson's ratio swelling and toughening hydrogel material can be used as a surgical material, such as a replacement or repair of fibrocartilage and / or fibrous connective tissue material.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high polymer materials, and particularly relates to a negative Poisson's ratio swelling and toughening hydrogel material and a preparation method and application thereof. BACKGROUND

[0002] A high polymer hydrogel is a three-dimensional network material formed by cross-linking of hydrophilic polymer chains, can be fully swollen in water without dissolving, has soft and moist texture, and is very similar to human soft tissue, and is considered as an ideal soft tissue replacement material. However, the traditional hydrogel with a mechanical modulus several orders of magnitude lower than that of fiber cartilage, ligament, tendon and other high-strength and high-toughness biological tissues cannot meet the bearing requirement thereof. Although the mechanical properties of high-strength hydrogels such as topological hydrogels, double-network hydrogels and nano-composite hydrogels are obviously improved, it is still difficult to meet the demand of high tensile strength of the material under long-term cyclic load.

[0003] A high-strength hydrogel based on a three-dimensional network support and a preparation method thereof disclosed in an early patent CN108525018A of the inventor's research group, the hydrogel is in-situ polymerized in the three-dimensional network support to form a high-strength hydrogel, the prepared hydrogel has good biocompatibility and extremely high mechanical strength, and can be applied to a replacement product of bearing soft tissue such as cartilage in human tissue. However, under a strong load, the physical combination of the flexible hydrogel and the rigid support easily leads to unsuitable stress, and the interface combination of the two phases is poor and easily torn. If the surface of the support and the hydrogel is chemically modified, in addition to the mechanical locking effect by interpenetration, the interface combination strength can be further improved by chemical bonding, which is an effective strategy to solve the above problems. Based on this, the inventor's research group proposed a negative Poisson's ratio structure annular support coated with sodium alginate / gelatin composite hydrogel as an artificial intervertebral disc in a patent CN117695443A of a negative Poisson's ratio structure artificial intervertebral disc and a preparation method thereof, and the aldehyde group in the amino group of the aldehyde-modified sodium alginate / gelatin composite hydrogel reacts with the aldehyde group on the aldehyde-modified negative Poisson's ratio structure annular support to form an imine bond to realize chemical bonding, and the support and the hydrogel correspond to the annulus fibrosus and the nucleus pulposus of the intervertebral disc respectively. The hydrogel will shrink transversely when subjected to a longitudinal compression load, and the combination strength of the composite hydrogel and the support is significantly improved, which can effectively avoid the problem of phase separation under the action of load. However, this method only improves the mechanical strength under compression load, and it is difficult to meet the high strength and high toughness required by fiber cartilage, ligament, tendon and other high-strength and high-toughness biological tissues under tension.

[0004] Stretching can induce the ordered orientation of molecular chains, which can significantly improve the strength and toughness of polymer materials. However, due to the high water content and cross-linked network structure, the molecular chains of hydrogel are difficult to achieve ordered orientation and improve toughness under normal stretching. In order to overcome this problem, researchers propose to assist hydrogel to achieve ordered orientation of molecular chains by means of electric / magnetic field induction, directional freezing, strong stretching process, self-assembly and other technical means, which can effectively improve the strength and toughness of hydrogel. For example, Feng Jiang et al. realized the ordered orientation of hydrophobic domains and molecular chains by salt precipitation-orientation-locking strategy, and the tensile modulus of hydrogel in the stretching direction was enhanced by about 3000 times, reaching more than 30 MPa. Chaoji Chen et al. proposed a supermolecular self-assembly technology based on salt precipitation effect to induce the ordered orientation of hydrogel supermolecular network in multiple directions, so as to exhibit 7400% super-tensile property in each direction.

[0005] Most of the existing methods for assisting the ordered orientation of molecular chains of hydrogel require complicated pre-treatment (such as freeze casting and pre-stretching), which can change the structure and water content of hydrogel, and thus affect the biological properties of hydrogel. Therefore, based on the stretching-induced orientation of molecular chains to improve toughness, developing new methods to assist the ordered orientation of molecular chains of hydrogel during stretching is the key to constructing new high-strength and high-toughness hydrogel patches. SUMMARY

[0006] In order to solve the above technical problems, one of the purposes of the present application is to provide a negative Poisson's ratio swelling and toughening hydrogel material.

[0007] The present application adopts the following technical solutions:

[0008] A negative Poisson's ratio swelling and toughening hydrogel material, the hydrogel material comprises a fiber skeleton and a hydrogel bonded on the fiber skeleton, the fiber skeleton has a cosine wave negative Poisson's ratio structure, specifically a periodic structure formed by cosine curves staggered in horizontal and vertical directions, and the structure is defined as:

[0009] The cosine curve in the horizontal direction is:

[0010] ;

[0011] The cosine curve in the vertical direction is:

[0012] ;

[0013] In the formula, represents the i-th horizontal cosine curve, i∈[1, +∞); represents the j-th vertical cosine curve, j∈[1, +∞); ​​is the number of unit cells along the direction of the cosine amplitude, ; is the number of unit cells along the direction of the cosine amplitude, ; is the number of unit cells along the direction of the cosine amplitude, ; is the number of unit cells along the direction of the cosine amplitude, ; .

[0014] The second object of the present application is to provide a preparation method of a negative Poisson's ratio swelling toughened hydrogel material as described above, comprising the following steps:

[0015] S1. Selecting the values of the demand according to the requirements, , , , , , preparing the staggered arrangement of polymer fiber skeleton by near-field direct writing technology;

[0016] S2. The amino or carboxyl modified polymer fiber skeleton is obtained by modifying the polymer fiber skeleton;

[0017] S3. The carboxyl or amino containing hydrogel prepolymer solution is bonded with the modified polymer fiber skeleton by condensation reaction, and the hydrogel material with cosine wave negative Poisson's ratio structure is obtained.

[0018] Preferably, the material of the polymer fiber skeleton includes any one of polyurethane, polycaprolactone, polylactic acid, and poly(lactic-co-glycolic acid).

[0019] Preferably, the method for amino or carboxyl modification is to graft carboxyl on the surface of the polymer fiber by acrylic acid grafting or maleic anhydride grafting method, or to introduce carboxyl on the surface of the polymer fiber by surface acidolysis or Baeyer-Villiger oxidation method, or to introduce amino or carboxyl on the surface of the polymer fiber by silane coupling agent modification method.

[0020] Preferably, in the step S3, the sodium alginate powder is stirred and dissolved into a 4wt% sodium alginate solution at 37℃, then 0.4wt% calcium sulfate powder and 0.1wt% gluconolactone powder are added and stirred uniformly, to obtain the carboxyl containing hydrogel prepolymer solution; the gelatin powder is stirred and dissolved into a 12wt% gelatin prepolymer solution at 50℃, to obtain the amino containing hydrogel prepolymer solution.

[0021] Preferably, the condensation reaction bonding process is to immerse the modified polymer fiber skeleton into the hydrogel prepolymer solution, react for 6 hours at 37℃, and then stand at room temperature for 24 hours, to obtain the hydrogel material with cosine wave negative Poisson's ratio structure.

[0022] A third object of the present application is to provide the use of a negative Poisson's ratio auxetic toughened hydrogel material as described above in the preparation of a material for replacing or repairing fibrocartilage and / or fibrous connective tissue.

[0023] A third object of the present application is to provide a material for replacing or repairing fibrocartilage and / or fibrous connective tissue, said material comprising a negative Poisson's ratio auxetic toughened hydrogel material as described above.

[0024] The present application has the following advantages:

[0025] (1) The material with negative Poisson's ratio effect will expand in the transverse direction when stretched in the axial direction, and will shrink in the transverse direction when compressed in the axial direction. Covalently grafting elastic fibers with negative Poisson's ratio effect to the molecular chains of hydrogel, under the action of stretching, the negative Poisson's ratio fibers will expand, and will be subjected to uniform distribution of tension in both directions. The present application further improves on this basis, by designing and regulating the negative Poisson's ratio structure, a wave-like negative Poisson's ratio structure with obvious auxetic effect (named as cosine wave-like negative Poisson's ratio structure) is obtained, the grafting rate of the cosine wave-like negative Poisson's ratio structure to the hydrogel / fiber is regulated, and the molecular chains of hydrogel and the negative Poisson's ratio fibers are jointly oriented and arranged by stress induction, so as to improve the strength and toughness of the hydrogel matrix.

[0026] (2) The present application provides a model which can realize continuous change and regulation of Poisson's ratio value, by adjusting the modeling parameters A and The value and sign of the Poisson's ratio of the super material structure can be simply regulated, and the material can realize the cosine wave-like negative Poisson's ratio structure. The cosine wave-like negative Poisson's ratio fiber has large specific surface area and rich covalent action, which helps to fix the molecular chains of hydrogel around the fiber, and the fiber is subjected to uniform distribution of tensile stress in the two-dimensional plane due to the auxetic effect, and the molecular chains of hydrogel and the fiber are jointly oriented and arranged by stress induction.

[0027] (3) The present application uses polymer fibers as the skeleton, which can make up for the disadvantage of low mechanical properties of hydrogel, and the hydrogel used can provide high biocompatibility and multifunctionality, such as tissue engineering and drug delivery. The condensation reaction step is mild and simple, and can effectively realize the chemical bonding of the polymer skeleton and the hydrogel. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 It is a schematic diagram of the cosine wave-like negative Poisson's ratio structure regulated according to the model parameters, and the arrow in the figure indicates the change of the structure from negative Poisson's ratio to positive Poisson's ratio.

[0029] Figure 2 It is a schematic diagram of the structure prepared when the model parameters are specific values, Figure 2 wherein a is the negative Poisson's ratio structure, and at this time -1, Figure 2 b is a positive Poisson's ratio structure, at this time =1.

[0030] Figure 3 Fig. 1 is a schematic diagram of the prepared cosine wave negative Poisson's ratio structure under tension, Fig. a is the stress distribution of the cosine wave negative Poisson's ratio fiber structure under tension by finite element simulation analysis, and Fig. b is the stress-induced hydrogel molecular chain arrangement of the cosine wave negative Poisson's ratio fiber.

[0031] Figure 4 Fig. 2 is an X-ray photoelectron spectrogram, Fig. a shows the fitting peak of C1s in the hydrogel (PCL-Gel), Fig. b shows the fitting peak of N1s in the modified scaffold (PCL-GA) and the hydrogel (PCL-Gel). v v v Fig. 3 is the equilibrium state configuration of PCL-Gel polymer under tension and non-tension.

[0032] Figure 5 Fig. 4 is the radial distribution function between Gel and PCL skeleton molecular chains in the equilibrium configuration. v

[0033] Fig. 5 is the space orientation function of Gel and PCL skeleton under tension and non-tension. Figure 6 v Fig. 6 is the space orientation function of the molecular chain in the equilibrium state.

[0034] Figure 7 Fig. 7 is a graph of the space orientation function of Gel and PCL skeleton changing with time under tension and non-tension. v

[0035] Figure 8 DETAILED DESCRIPTION

[0036] The technical solutions of the present application will be described in more detail below in combination with experiments.

[0037] Unless otherwise specified, the terms used herein have meanings commonly understood by those skilled in the art.

[0038] Example 1

[0039] Design and regulation of cosine wave negative Poisson's ratio structure:

[0040] The programmable parameter modeling is carried out through the cosine function, and the continuous Poisson's ratio value change regulation can be realized, and the model is:

[0041] ;

[0042] wherein, represents the first horizontal cosine curve,​​​​​ ; represents the first vertical cosine curve, ; cosine amplitude, ; the number of unit cells along direction, ; the number of unit cells along direction, ; the length of a single cell, ; the adjustment factor, .

[0043] the absolute value of the Poisson's ratio can be adjusted by the sign of the Poisson's ratio can be adjusted by Figure 1 , by adjusting the modeling parameters A and , the value and the sign of the Poisson's ratio of the metamaterial structure can be simply adjusted.

[0044] For example, as shown in a of Figure 2 , when the amplitude of the cosine curve is adjusted to be -1, the prepared structure is a negative Poisson's ratio structure, and =-1; as shown in b of , when the orientation of the cosine curve is adjusted to be 1, the prepared structure is a positive Poisson's ratio structure, and Figure 2 =1, and the positive Poisson's ratio structure becomes denser as the value of A decreases; when the orientation of the cosine curve is adjusted to be -1, the prepared structure is a negative Poisson's ratio structure, and =-1, and the positive Poisson's ratio structure becomes denser as the value of A decreases. To meet the needs of the cosine wave negative Poisson's ratio structure, in the present application,

[0045] the value is -1. Embodiment 2

[0046] Preparation of a negative Poisson's ratio auxetic toughened hydrogel material

[0047] comprising the following steps:

[0048] S1. Selecting

[0049] , , , , , The high polymer fiber skeleton is prepared by near-field direct writing technology, and the material of the high polymer fiber skeleton includes any one of polyurethane, polycaprolactone, polylactic acid, and poly-lactic-glycolic acid copolymer.

[0050] S2. The high polymer fiber skeleton is modified with amino or carboxyl group, and the modification method is a prior art which can be selected according to requirements, for example, the carboxyl group can be grafted on the surface of the high polymer fiber by acrylic acid grafting or maleic anhydride grafting method, or the carboxyl group can be introduced on the surface of the high polymer fiber by surface acidolysis or Baeyer-Villiger oxidation method, or the amino or carboxyl group can be introduced on the surface of the high polymer fiber by silane coupling agent modification method, and finally the modified high polymer fiber skeleton is obtained.

[0051] S3. The modified high polymer fiber skeleton is immersed in a hydrogel prepolymer solution containing carboxyl or amino group, and reacted at 37°C for 6 hours, and then placed at room temperature for 24 hours, to obtain a hydrogel material with a cosine wave negative Poisson's ratio structure.

[0052] The preparation method of the hydrogel prepolymer solution is as follows:

[0053] The preparation of the multi-amino hydrogel prepolymer solution is exemplified by a typical gelatin hydrogel. Gelatin powder is dissolved into a uniform gelatin prepolymer solution (12wt%) at 50°C under stirring;

[0054] The preparation of the multi-carboxyl hydrogel prepolymer solution is exemplified by a typical sodium alginate hydrogel. Sodium alginate powder is dissolved into a uniform sodium alginate solution (4wt%) at 37°C under stirring, and then 0.4wt% calcium sulfate powder and 0.1wt% gluconolactone powder are added to form a hydrogel prepolymer solution.

[0055] Example 3

[0056] A preparation method of a hydrogel material with a cosine wave negative Poisson's ratio structure includes the following steps:

[0057] S1. The high polymer fiber skeleton is prepared by near-field direct writing technology, and the material of the high polymer fiber skeleton includes any one of polyurethane, polycaprolactone, polylactic acid, and poly-lactic-glycolic acid copolymer. 、 、 、 、 The polycaprolactone fiber skeleton is prepared by near-field direct writing technology;

[0058] S2. The polycaprolactone fiber skeleton is modified with amino group, and the modification method is that the fiber is sequentially soaked in 10% (w / w) 1,6-hexanediamine / isopropyl alcohol solution and 2% (w / w) glutaraldehyde solution for 12h, ultrasonic cleaned, and vacuum dried for 48h to obtain a modified PCL-GA fiber skeleton.

[0059] S3. The modified polymer fiber scaffold was immersed in the gelatin (Gel) hydrogel prepolymer solution with amino groups, and reacted at 37°C for 6 hours, followed by standing at room temperature for 24 hours to obtain the hydrogel material with cosine wave negative Poisson's ratio structure. v PCL-Gel).

[0060] Performance test

[0061] The material prepared in Example 3 was tested

[0062] The covalent grafting of the fiber and the hydrogel molecular chain was determined by X-ray photoelectron spectroscopy.

[0063] As shown in FIG. 6, the XPS spectrum of the C element of the hybrid hydrogel is shown in FIG. 6a, wherein the characteristic peaks of N2C=O, C-O-C and C-C are 288.6 eV, 287.6 eV and 284.8 eV respectively, and the appearance of N2C=O and C-O-C groups indicates the successful introduction of gelatin. Figure 4 As shown in FIG. 6, the XPS spectrum of the C element of the hybrid hydrogel is shown in FIG. 6a, wherein the characteristic peaks of N2C=O, C-O-C and C-C are 288.6 eV, 287.6 eV and 284.8 eV respectively, and the appearance of N2C=O and C-O-C groups indicates the successful introduction of gelatin. Figure 4 As shown in FIG. 6, the XPS spectrum of the C element of the hybrid hydrogel is shown in FIG. 6a, wherein the characteristic peaks of N2C=O, C-O-C and C-C are 288.6 eV, 287.6 eV and 284.8 eV respectively, and the appearance of N2C=O and C-O-C groups indicates the successful introduction of gelatin. Figure 4 As shown in FIG. 6, the XPS spectrum of the C element of the hybrid hydrogel is shown in FIG. 6a, wherein the characteristic peaks of N2C=O, C-O-C and C-C are 288.6 eV, 287.6 eV and 284.8 eV respectively, and the appearance of N2C=O and C-O-C groups indicates the successful introduction of gelatin. -v As shown in FIG. 6, the XPS spectrum of the C element of the hybrid hydrogel is shown in FIG. 6a, wherein the characteristic peaks of N2C=O, C-O-C and C-C are 288.6 eV, 287.6 eV and 284.8 eV respectively, and the appearance of N2C=O and C-O-C groups indicates the successful introduction of gelatin. -v As shown in FIG. 6, the XPS spectrum of the C element of the hybrid hydrogel is shown in FIG. 6a, wherein the characteristic peaks of N2C=O, C-O-C and C-C are 288.6 eV, 287.6 eV and 284.8 eV respectively, and the appearance of N2C=O and C-O-C groups indicates the successful introduction of gelatin. -v As shown in FIG. 6, the XPS spectrum of the C element of the hybrid hydrogel is shown in FIG. 6a, wherein the characteristic peaks of N2C=O, C-O-C and C-C are 288.6 eV, 287.6 eV and 284.8 eV respectively, and the appearance of N2C=O and C-O-C groups indicates the successful introduction of gelatin. - v As shown in FIG. 6, the XPS spectrum of the C element of the hybrid hydrogel is shown in FIG. 6a, wherein the characteristic peaks of N2C=O, C-O-C and C-C are 288.6 eV, 287.6 eV and 284.8 eV respectively, and the appearance of N2C=O and C-O-C groups indicates the successful introduction of gelatin.

[0064] The orientation of the NPR fiber-induced hydrogel molecular chain arrangement was evaluated by molecular dynamics simulation. Figure 5 The equilibrium configurations of the hydrogel (- v PCL-Gel) in the stretched and unstretched states are shown in FIG. 7, which shows that when the- v PCL-Gel is in the unstretched equilibrium state, the- v PCL scaffold molecular chains can maintain good linearity but will appear slight twisting, while the grafted Gel hydrogel molecular chains are tightly wrapped around the- v PCL scaffold molecular chains, maintaining a relatively small free energy of the polymer molecular system; when the polymer is in the equilibrium state in the stretched state, due to the negative Poisson's ratio effect of the- v PCL scaffold, the scaffold expands under the action of stretching, and the Gel hydrogel molecular chains are uniformly distributed in the direction of tending to be perpendicular to the scaffold.

[0065] - v PCL scaffold is in the unstretched and stretched states, the Gel and- vThe radial distribution function (RDF) between the molecular chains of the PCL backbone is as follows: Figure 6 As shown, the height of the first main peak of RDF in the stretched state is significantly higher than that in the unstretched state, indicating that the probability of the main peak appearing at around r=1Å after stretching is much greater than before stretching. After stretching, the gel... v The distribution near the PCL stent becomes more concentrated.

[0066] Gel in stretched and unstretched states and - v The spatial orientation function between PCL skeletons varies with time, as shown in the figure below. Figure 7 As shown, in the equilibrium configuration, P2(r) mainly fluctuates around the 0 value line in the unstretched state, indicating that the Gel molecular chains are in a disordered state at this time; while in the stretched state, the P2(r) value is smaller than that in the unstretched state, becomes negative after 525 ps and gradually approaches -0.5, indicating that the spatial distribution of the stretched Gel hydrogel tends to be in the direction perpendicular to the scaffold. Figure 8 The graph shows the spatial orientation function of the molecular chains in equilibrium. From the P2(r) data at each moment, it can be seen that before stretching, the peaks of the gel hydrogel are mainly concentrated around 10 Å, but after stretching, the peaks are generally distributed above 30 Å. Furthermore, after stretching, P2(r) exhibits a negative vertical distribution, indicating that the stretched gel hydrogel is spatially displaced away from the equilibrium state. v PCL supports tend to be arranged in a vertical orientation.

[0067] The above experiments show that the negative Poisson's ratio scaffold can induce the orientation of water molecules in the hydrogel, indicating that the negative Poisson's ratio effect is beneficial to further enhancing the mechanical properties of hybrid hydrogels.

[0068] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A negative Poisson's ratio, swelling, toughened hydrogel material, characterized in that, The hydrogel material comprises a high molecular fiber skeleton and a hydrogel bonded on the high molecular fiber skeleton, the high molecular fiber skeleton has a cosine wave negative Poisson's ratio structure, specifically a periodic structure formed by cosine curves staggered in horizontal and vertical directions, the structure is defined as: Cosine curve in horizontal direction: ； Cosine curve in vertical direction: ； wherein represents the i-th horizontal cosine curve, i ∈ [1, +∞); represents the j-th vertical cosine curve, j ∈ [1, +∞); is the cosine amplitude, ; is the number of unit cells along the direction; is the number of unit cells along the direction; is the length of a single unit cell; is the adjustment factor, ; The preparation method of the hydrogel material comprises the following steps: S1. Selecting the value of , , , , , the high polymer fiber skeleton in staggered arrangement is prepared by near-field direct writing technology. S2. Amino or carboxyl modification is performed on the high molecular fiber skeleton to obtain a modified high molecular fiber skeleton; S3. A carboxyl or amino containing hydrogel prepolymer solution is bonded with the modified high molecular fiber skeleton through condensation reaction to obtain a hydrogel material with a cosine wave negative Poisson's ratio structure.

2. A negative Poisson's ratio, swell-induced toughened hydrogel material as claimed in claim 1, wherein, The material of the high molecular fiber skeleton comprises any one of polyurethane, polycaprolactone, polylactic acid, and poly(lactic-co-glycolic acid).

3. A negative Poisson's ratio, swell-induced toughened hydrogel material as claimed in claim 1, wherein, The method for amino or carboxyl modification is to graft carboxyl on the surface of the high molecular fiber through acrylic acid grafting or maleic anhydride grafting, or to introduce carboxyl on the surface of the high molecular fiber through surface acidolysis or Baeyer-Villiger oxidation, or to introduce amino or carboxyl on the surface of the high molecular fiber through silane coupling agent modification.

4. A negative Poisson's ratio, swell-induced toughened hydrogel material as claimed in claim 1, wherein, In step S3, sodium alginate powder is stirred and dissolved into a 4 wt% sodium alginate solution at 37°C, then 0.4 wt% calcium sulfate powder and 0.1 wt% gluconolactone powder are added and stirred uniformly to obtain a carboxyl containing hydrogel prepolymer solution; gelatin powder is stirred and dissolved into a 12 wt% gelatin prepolymer solution at 50°C to obtain an amino containing hydrogel prepolymer solution.

5. A negative Poisson's ratio, swell-induced toughened hydrogel material as claimed in claim 1, wherein, In the condensation reaction bonding process, the modified high molecular fiber skeleton is immersed in the hydrogel prepolymer solution, and the reaction is carried out at 37°C for 6 hours, followed by room temperature standing for 24 hours to obtain a hydrogel material with a cosine wave negative Poisson's ratio structure.

6. Use of the negative Poisson's ratio swelling toughened hydrogel material according to claim 1 in the preparation of a material for replacing or repairing fibrous cartilage and / or fibrous connective tissue.

7. A material for replacing or repairing fibrocartilage and / or fibrous connective tissue, characterized in that, A material comprising the negative Poisson's ratio swelling toughened hydrogel material according to claim 1.

Images