Enamel-like bionic composite material with hierarchical structure and preparation method therefor

Abstract

An enamel-like bionic composite material with a hierarchical structure and a preparation method therefor. The method comprises the following steps: assembling nanowires by adopting a wet spinning technique to obtain nanoclusters; dissolving a polymer in water to obtain a clear solution; dispersing the nanoclusters into an organic solution to form a uniform suspension as a slurry; adopting a bidirectional freezing ice-templating technique to assemble the nanoclusters into a macroscale parallel layered arrangement framework; and compacting the framework by means of mechanical compression densification, and acquiring an enamel-like composite material with a hierarchical structure. The enamel-like bionic composite material with the hierarchical structure, prepared by adopting the wet spinning technique to obtain the nanoclusters assembled by one-dimensional nanowires and then by means of the ice-templating technique and the method of mechanical compression densification, exhibits mechanical properties matched with real enamel, thereby meeting the requirements of high strength and high toughness of the composite material in engineering.

Description

A bionic enamel-like composite material with a multi-level structure and a preparation method thereof Technical Field

[0001] The present application relates to the field of bionic composite materials, and in particular to an enamel-like bionic composite material with a multi-level substructure and a preparation method thereof. Background Art

[0002] Tooth enamel is a typical representative of structural composite materials that combines light weight, high strength, and high toughness (hardness and modulus can be as high as 62.1-108.2 GPa and 1.1-4.9 GPa). It wraps around the outer surface of the teeth and is the hardest part of human bone. It is a barrier that protects the dental occlusal system of some mammals from continuous impact and shear loads. It also has excellent resistance to deformation and vibration damage. Even after hundreds of millions of cycles of chewing wear, tooth enamel only disperses most of the chewing stress with extremely limited damage, thereby avoiding tooth fracture and failure.

[0003] However, tooth enamel cannot regenerate after it is damaged. Without prompt treatment, it can lead to progressive tooth loss, toothache, or even tooth loss. Furthermore, tooth defects can only be repaired with artificial materials. Currently available dental restoration materials primarily include metals, ceramics, and resins, but these often suffer from a mismatch between performance and structure. Therefore, there is an urgent need to develop biomimetic materials that match the structure and performance of natural tooth enamel while balancing mechanical, aesthetic, and clinical medical applications.

[0004] Current methods for preparing biomimetic enamel composites primarily include constructing non-biological enamel-like structural materials with columnar arrays through layer-by-layer assembly techniques, preparing enamel-like multilayer organic-inorganic columnar structures through micro-additive manufacturing, and in situ repair of damaged enamel by growing hydroxyapatite arrays. However, there is still a lack of rational design and synthesis methods to construct large-scale, high-performance biomimetic enamel-like composites that can easily mimic the structure of enamel.

[0005] Summary of the Invention

[0006] In response to the shortcomings of existing bionic enamel composite material preparation and assembly methods, the present application provides an enamel-like bionic composite material with a multi-level substructure and a preparation method thereof.

[0007] In a first aspect, the present invention provides a method for preparing an enamel-like biomimetic composite material having a multi-level substructure, and the present invention is achieved by adopting the following technical solutions.

[0008] A method for preparing a biomimetic enamel-like composite material with a multi-level substructure comprises the following steps:

[0009] S1. Adding hydroxyapatite nanowires to a mixed solution of water and ethylene glycol, wherein the concentration of the hydroxyapatite nanowires in the mixed solution is in the range of 0.2-1 mg / mL; after stirring the mixture, ferric chloride, magnesium sulfate, calcium chloride, and ammonium dihydrogen phosphate are sequentially added, and the mixture is stirred and reacted at 30-80°C for 2-8 hours; wherein the concentration of the ferric chloride in the reaction system is in the range of 0.05-0.5 mg / mL; the concentration of the magnesium sulfate in the reaction system is in the range of 0.2-2 mg / mL; the concentration of the calcium chloride in the reaction system is in the range of 0.05-0.5 mg / mL; and the concentration of the ammonium dihydrogen phosphate in the reaction system is in the range of 0.1-2 mg / mL;

[0010] S2. The reaction product obtained in step S1 was centrifuged, washed, and dried to obtain a dry powder sample;

[0011] S3. The dried powder obtained in step S2 is calcined to obtain surface-modified hydroxyapatite nanowires; the surface-modified hydroxyapatite nanowires obtained have a one-dimensional nanowire morphology, a length of about 4 to 11 μm, a diameter of about 20-100 nm, and an aspect ratio of 100-200;

[0012] S4. The surface-modified hydroxyapatite nanowires obtained in step S3 are added to a mixture of water, ethanol, and oleic acid, stirred uniformly, and then a NaOH solution is added and stirred, followed by a hydrothermal reaction at a temperature in the range of 150-200°C for a reaction time of 2-8 hours. The concentration of the surface-modified hydroxyapatite nanowires in the mixture is in the range of 0.01-0.1 g / mL.

[0013] S5. The reaction product obtained in step S4 is wet-spinned and injected into a coagulation bath containing ethanol and water. The reactant is allowed to stand for a period of time, and then centrifuged, washed, and dried to obtain a dry powder sample, i.e., the nanoclusters; wherein the reactant injection rate is 0.1-1 mL / min;

[0014] S6. dissolving a water-soluble organic polymer in water at 75 to 90° C. and stirring to obtain a polymer solution; wherein the mass ratio of the organic polymer to water is 1:(30-80);

[0015] S7. Take the polymer solution obtained in step S6, add the nanoclusters obtained in step S5 and stir to obtain a nanocluster suspension; the concentration of the nanoclusters in the polymer solution is in the range of 0.03-0.15 g / mL;

[0016] S8. The nanocluster suspension obtained in S7 was poured into a polytetrafluoroethylene mold containing a polydimethylsiloxane sloped bottom with an inclination angle of 5-25°. The device was then placed on a copper plate, which was placed in a Dewar tank filled with liquid nitrogen for magnetic field-assisted ice-templated assembly, ultimately generating a macroscopic bulk composite material.

[0017] S9. The bulk composite material obtained in step S8 is dried to obtain a dried bulk sample;

[0018] S10. The dried block sample obtained in step S9 is subjected to mechanical compression at room temperature, with a pressure range of 5-30 MPa and a compression time of 0.5-3 hours. The compacted enamel-like biomimetic composite material has a multi-level structure similar to that of enamel.

[0019] By adopting the above technical solution, the present invention uses simple and green one-dimensional nanowires and organic polymers as raw materials, adopts wet spinning technology to produce nanoclusters assembled from the one-dimensional nanowires, and then uses ice template technology and mechanical compression densification methods to prepare a biomimetic composite material with a multi-level structure similar to enamel. This preparation method is simple to operate, pollution-free, and can be prepared on a macro scale. The resulting composite material has a hardness of 2.5-4.1GPa, a modulus of 60-90GPa, a flexural strength of 120-160MPa, and a toughness of 5-16MPa m. 1 / 2 .

[0020] Furthermore, in step S1, hydroxyapatite nanowires are added to a mixed solution of water and ethylene glycol, and stirred at 20-30° C. until a uniform white suspension is formed.

[0021] Furthermore, in step S1, the concentration of the hydroxyapatite nanowires in the mixed solution is 0.5 mg / mL.

[0022] Furthermore, in step S1, the volume ratio of water to ethylene glycol is 1:(1-20), preferably 1:19.

[0023] Furthermore, in step S1, the concentration of the ferric chloride in the reaction system is 0.1 mg / mL; the concentration of the magnesium sulfate in the reaction system is 1 mg / mL; the concentration of the calcium chloride in the reaction system is 0.1 mg / mL; and the concentration of the ammonium dihydrogen phosphate in the reaction system is 0.2 mg / mL.

[0024] Furthermore, in step S2, the reaction product obtained in step S1 is centrifuged and washed at a centrifugal speed range of 5000-10000 r / min, and the washing solvent is water; after centrifugal washing, it is vacuum dried at a low temperature of -50°C to -90°C for 24-48 hours.

[0025] Furthermore, in step S3, the temperature range of the calcination conditions is 200-500°C, preferably 300°C; the calcination time is 1-4h, preferably 2h; and the heating rate is 5-20°C / min, preferably 10°C / min.

[0026] Furthermore, in step S4, the concentration of the surface-modified hydroxyapatite nanowires in the mixed solution is 0.05 g / mL.

[0027] Furthermore, in step S4, the volume ratio of water, ethanol and oleic acid is (1-2):1:(1-2). Preferably, the volume ratio of the three is 2:1:2.

[0028] Furthermore, in step S4, the surface-modified hydroxyapatite nanowires obtained in step S3 are added to a mixture of water, ethanol, and oleic acid, and stirred at 20-30° C. until a uniform light yellow suspension is formed.

[0029] Furthermore, in step S4, after adding the NaOH solution, stirring is carried out at 20-40° C. for 10-60 minutes.

[0030] Furthermore, in step S4, the concentration of the NaOH solution is 0.1-0.5 g / mL, and the amount added is 1-5 mL; preferably, the concentration is 0.2 mg / mL, and the amount added is 2.5 mL.

[0031] Furthermore, in step S4, the temperature of the hydrothermal reaction is 180° C., and the reaction time is 4 h.

[0032] Furthermore, in step S5, a syringe with a range of 1-5 mL is used to draw the reaction product obtained in step S4. Preferably, the range of the syringe is 5 mL.

[0033] Furthermore, in step S5, the reactant injection rate is 0.5 mL / min.

[0034] Furthermore, in step S5, the volume ratio of ethanol to water is (1-4):1, preferably 4:1.

[0035] Furthermore, in step S5, the standing time is 1-10 min, preferably 5 min.

[0036] Furthermore, in step S5, the centrifugal speed range is 5000-10000 r / min, and the washing solvent is water;

[0037] Furthermore, in step S5, after centrifugal washing, the mixture is vacuum dried at a low temperature of -50°C to -90°C for 24-48 hours.

[0038] Furthermore, in step S6, the organic polymer includes polyvinyl alcohol, carboxymethyl cellulose, and sodium alginate.

[0039] Furthermore, in step S6, the mass ratio of the organic polymer to water is 1:40.

[0040] Furthermore, in step S7, the solution obtained in step S6 is added to the nanoclusters obtained in step S5, and the mixture is stirred at 20-30° C. until a uniform light yellow suspension is formed.

[0041] Furthermore, in step S7, the concentration of the nanoclusters in the polymer solution is 0.1 g / mL.

[0042] Furthermore, in step S8, the inclination angle of the polydimethylsiloxane (PDMS) slope bottom contained in the ice template freezing device is 25°.

[0043] Furthermore, in step S8, the dimensions of the copper plate are: 20-40 cm in length, 2-4 cm in width, and 0.5-2 cm in thickness.

[0044] Furthermore, in step S9, the bulk composite material obtained in step S8 is vacuum dried at a low temperature of -50°C to -90°C for 24-48 hours. The dried sample has a length of 2-4 cm and a width of 1-2 cm, and has a layered structure composed of parallel nanoclusters, with a layer thickness ranging from 2-5 microns and an interlayer spacing ranging from 10-20 microns.

[0045] Furthermore, in steps S1, S4, and S6, the stirring speed is 200 to 400 rpm, and the stirring time is 0.5 to 2 h; in step S7, the stirring speed is 200 to 400 rpm, and the stirring time is 48 to 72 h.

[0046] In a second aspect, the present invention provides an enamel-like bionic composite material with a multi-level substructure, and the present invention is implemented by adopting the following technical solutions.

[0047] A biomimetic composite material with a multi-level structure similar to tooth enamel, prepared by the above-mentioned preparation method, comprises a micro-nano one-dimensional ceramic nanowire reinforcement phase and an organic polymer toughening phase; the micro-nano ceramic nanowires are hydroxyapatite nanowires with an aspect ratio (6-12 μm / 30-150 nm) of 80-200; and the organic polymer is selected from polyvinyl alcohol, carboxymethyl cellulose, and sodium alginate.

[0048] In a third aspect, the present invention provides a use of an enamel-like biomimetic composite material having a multi-level substructure, which is achieved by adopting the following technical solutions.

[0049] An application of the above-mentioned enamel-like bionic composite material with a multi-level substructure in the preparation of tooth defect repair materials.

[0050] This application has the following beneficial effects.

[0051] (1) The raw materials used in the preparation method of the present invention are simple and easy to obtain, the cost is low, and it can be prepared in large quantities, is environmentally friendly, and is simple to operate;

[0052] (2) The enamel-like biomimetic composite material with a multi-level structure prepared by the present invention presents a microstructure that is almost identical to that of real enamel, and the overall size reaches a macroscopic level, ensuring its practical application;

[0053] (3) The enamel-like biomimetic composite material with a multi-level structure prepared by the present invention exhibits mechanical properties that match those of real enamel: hardness of 2.5-4.1 GPa, modulus of 60-90 GPa, and excellent bending strength (120-160 MPa) and toughness (5-16 MPa m 1 / 2 ), meeting the engineering requirements of composite materials for high strength and toughness. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] FIG1 is a schematic diagram of the wet spinning process of the present invention;

[0055] FIG2 is a schematic diagram of the freezing process of the ice template of the present invention;

[0056] FIG3 is a scanning electron microscope photograph of the layered structure of the enamel-like biomimetic composite material with a multi-level substructure obtained in Example 1 of the present invention;

[0057] FIG4 is an optical photograph of a sample obtained in Example 1 of the present invention;

[0058] FIG5 is a diagram showing the mechanical data of the enamel-like biomimetic composite material with a multi-level structure obtained in Example 1 of the present invention;

[0059] FIG6 is a scanning electron microscope photograph of a cross-section of the enamel-like biomimetic composite material with a multi-level structure obtained in Example 1 of the present invention after compression;

[0060] FIG7 is a scanning electron microscope photograph of the layered structure of the enamel-like biomimetic composite material obtained in Example 2 of the present invention;

[0061] FIG8 is a diagram showing the mechanical data of the enamel-like biomimetic composite material obtained in Example 2 of the present invention;

[0062] FIG9 is a scanning electron microscope photograph of a cross-section of the enamel-like biomimetic composite material obtained in Example 2 of the present invention after compression;

[0063] FIG10 is a scanning electron microscope photograph of the layered structure of the enamel-like biomimetic composite material obtained in Example 3 of the present invention;

[0064] FIG11 is a diagram showing the mechanical data of the enamel-like biomimetic composite material obtained in Example 3 of the present invention;

[0065] FIG12 is a scanning electron microscope photograph of the cross section of the enamel-like biomimetic composite material obtained in Example 3 of the present invention after compression. DETAILED DESCRIPTION

[0066] The present patent application is further described below with reference to the embodiments.

[0067] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; the materials, reagents, etc. used in the following preparation examples and examples are all commercially available unless otherwise specified.

[0068] Example 1

[0069] A method for preparing a tooth enamel-like biomimetic composite material based on the directional assembly of hydroxyapatite nanoclusters and polyvinyl alcohol comprises the following steps:

[0070] In the first step, hydroxyapatite nanowires are added to a mixed solution of water and ethylene glycol, stirred at 25°C to form a uniform white suspension, and ferric chloride, magnesium sulfate, calcium chloride, and ammonium dihydrogen phosphate are added in sequence, and stirred at 40°C for 4 hours; wherein the concentration of the hydroxyapatite nanowires in the mixed solution is 0.53 mg / mL; the volume ratio of water to ethylene glycol is 1:19; the concentration of the ferric chloride in the reaction system is 0.1 mg / mL; the concentration range of the magnesium sulfate in the reaction system is 1.2 mg / mL; the concentration range of the calcium chloride in the reaction system is 0.1 mg / mL; and the concentration range of the ammonium dihydrogen phosphate in the reaction system is 0.26 mg / mL;

[0071] In the second step, the reaction product obtained in the first step is centrifuged and washed, and then frozen and placed in a freeze dryer for vacuum drying at a low temperature of -90°C for 48 hours to remove moisture in the sample, thereby obtaining a dry powder sample; wherein the centrifugal speed range is 10,000 r / min and the washing solvent is water;

[0072] The third step is to take the dried powder obtained in the second step and place it in a muffle furnace for calcination to obtain surface-modified hydroxyapatite nanowires; wherein the calcination temperature range is 300°C, the calcination time is 2 hours, and the heating rate is 10°C / min;

[0073] In the fourth step, the nanowires obtained in the third step are added to a mixture of water, ethanol, and oleic acid, stirred at 25°C to form a uniform light yellow suspension, and then a NaOH solution is added, stirred at 25°C for 30 minutes, and then transferred to a hydrothermal kettle for a hydrothermal reaction; wherein the concentration range of the nanowires in the mixture is 0.05 g / mL, the volume ratio of water, ethanol, and oleic acid is 1:1:1; the concentration of the NaOH solution is 0.2 g / mL; the temperature range of the hydrothermal reaction is 180°C, and the reaction time is 4 hours;

[0074] In the fifth step, the reaction product obtained in the fourth step is drawn into a syringe with a range of 5 mL, and then wet spinning is performed (as shown in FIG1 ), and the reactant is injected into a coagulation bath containing ethanol and water, and allowed to stand for a period of time, and then centrifuged and washed, frozen and placed in a freeze dryer and vacuum dried at a low temperature of -90°C for 48 hours to remove moisture in the sample, and finally a dry powder sample, i.e., a nanocluster, is obtained; wherein the reactant injection speed is 0.5 mL / min, the volume ratio of ethanol to water is 4:1, and the standing time is 5 minutes; the centrifugal speed range is 10,000 r / min, and the washing solvent is water;

[0075] In the sixth step, 1 g of polyvinyl alcohol was dissolved in 35 mL of deionized water in an oil bath at 80° C., and stirred at a stirring rate of 300 rpm for 2 h to obtain 30 g of a uniformly mixed colorless transparent solution.

[0076] Step 7: 9 mL of the solution obtained in step 6 was added with 0.81 g of nanoclusters, and the mixture was stirred in a 30°C water bath at a stirring rate of 300 rpm for 48 h to form a uniform light yellow suspension.

[0077] In the eighth step, the light yellow suspension obtained in the seventh step was poured into a polytetrafluoroethylene mold containing a polydimethylsiloxane (PDMS) sloped bottom with an inclination angle of 20°. The device was then placed on a copper plate with dimensions of 30 cm long, 2 cm wide, and 0.5 cm thick. The copper plate was placed in the middle of a Dewar tank filled with liquid nitrogen. A magnetic field-assisted ice template assembly was performed (as shown in FIG2 ), and finally a macroscopic bulk composite material was generated. In the present invention, the freezing temperature provided by the liquid nitrogen was -120°C.

[0078] In the ninth step, the frozen sample obtained in the eighth step was placed in a freeze dryer and dried at a low-temperature vacuum drying temperature of -90°C for 48 hours to remove the water in the sample and obtain a dried sample. After removing the water, a layered hydroxyapatite nanocluster and polyvinyl alcohol complex was obtained, with dimensions of 4 cm in length and 2 cm in width. Figure 3 is a scanning electron micrograph of the product, which shows that the layer thickness of the product is approximately 2 microns and the interlayer spacing (solid arrow line) is 20 microns. The freeze dryer used was an Alpha 1-2plus model from Christ Company in Germany.

[0079] In the tenth step, the freeze-dried hydroxyapatite nanoclusters and polyvinyl alcohol composite framework obtained in the ninth step were placed in a tablet press and compressed at 20 MPa for 2 h at room temperature to obtain a light yellow dense block material (as shown in FIG4 ).

[0080] In this embodiment, quasi-static nanoindentation was used to test the enamel-like composite material prepared in Example 1 (denoted as HEA, see Figure 5), and the indentation depth ranged from 25 to 400 nm. The test results showed that the hardness of the composite material prepared in Example 1 was 3.8 GPa and the modulus was 86.2 GPa, which were consistent with the mechanical properties of real enamel. At the same time, quasi-static three-point bending (standard: ASTM D790-03) was used to test Example 1, with a loading speed of 1 mm / min. Its flexural strength was 160 MPa and its toughness was 10 MPa m 1 / 2 Scanning electron microscopy of the cross-section of the tested specimen revealed a multi-level structure similar to that of tooth enamel (as shown in Figure 6).

[0081] Example 2

[0082] A method for preparing a tooth enamel-like biomimetic composite material based on the directional assembly of hydroxyapatite nanoclusters and carboxymethyl cellulose comprises the following steps:

[0083] In the first step, hydroxyapatite nanowires are added to a mixed solution of water and ethylene glycol, stirred at 25°C to form a uniform white suspension, and ferric chloride, magnesium sulfate, calcium chloride, and ammonium dihydrogen phosphate are added in sequence, and stirred at 40°C for 4 hours; wherein the concentration of the hydroxyapatite nanowires in the mixed solution is 0.53 mg / mL; the volume ratio of water to ethylene glycol is 1:19; the concentration of the ferric chloride in the reaction system is 0.1 mg / mL; the concentration range of the magnesium sulfate in the reaction system is 1.2 mg / mL; the concentration range of the calcium chloride in the reaction system is 0.1 mg / mL; and the concentration range of the ammonium dihydrogen phosphate in the reaction system is 0.26 mg / mL;

[0084] In the second step, the reaction product obtained in the first step is centrifuged and washed, and then frozen and placed in a freeze dryer for vacuum drying at a low temperature of -90°C for 48 hours to remove moisture in the sample, thereby obtaining a dry powder sample; wherein the centrifugal speed range is 10,000 r / min and the washing solvent is water;

[0085] The third step is to take the dried powder obtained in the second step and place it in a muffle furnace for calcination to obtain surface-modified hydroxyapatite nanowires; wherein the calcination temperature range is 300°C, the calcination time is 2 hours, and the heating rate is 10°C / min;

[0086] In the fourth step, the nanowires obtained in the third step are added to a mixture of water, ethanol, and oleic acid, stirred at 25°C to form a uniform light yellow suspension, and then a NaOH solution is added, stirred at 25°C for 30 minutes, and then transferred to a hydrothermal kettle for a hydrothermal reaction; wherein the concentration range of the nanowires in the mixture is 0.05 g / mL, the volume ratio of water, ethanol, and oleic acid is 1:1:1; the concentration of the NaOH solution is 0.2 g / mL; the temperature range of the hydrothermal reaction is 180°C, and the reaction time is 4 hours;

[0087] In the fifth step, the reaction product obtained in the fourth step is drawn into a syringe with a range of 5 mL, and then wet spinning is performed (as shown in FIG1 ), and the reactant is injected into a coagulation bath containing ethanol and water, and allowed to stand for a period of time, and then centrifuged and washed, frozen and placed in a freeze dryer and vacuum dried at a low temperature of -90°C for 48 hours to remove moisture in the sample, and finally a dry powder sample, i.e., a nanocluster, is obtained; wherein the reactant injection speed is 0.5 mL / min, the volume ratio of ethanol to water is 4:1, and the standing time is 5 minutes; the centrifugal speed range is 10,000 r / min, and the washing solvent is water;

[0088] In the sixth step, 1 g of carboxymethyl cellulose was dissolved in 35 mL of deionized water in an oil bath at 80° C., and stirred at a stirring rate of 300 rpm for 2 h to obtain 30 g of a uniformly mixed colorless transparent solution.

[0089] In the seventh step, 9 mL of the solution obtained in the sixth step was added with 0.81 g of nanoclusters, and the mixture was stirred in a water bath at 30°C at a stirring rate of 300 rpm for 48 h to form a uniform light yellow suspension.

[0090] In the eighth step, the light yellow suspension obtained in the seventh step was poured into a polytetrafluoroethylene mold containing a polydimethylsiloxane (PDMS) sloped bottom with an inclination angle of 20°. The device was then placed on a copper plate with dimensions of 30 cm long, 2 cm wide, and 0.5 cm thick. The copper plate was placed in the middle of a Dewar tank filled with liquid nitrogen. A magnetic field-assisted ice template assembly was performed (as shown in FIG2 ), and finally a macroscopic bulk composite material was generated. In the present invention, the freezing temperature provided by the liquid nitrogen was -120°C.

[0091] In step nine, the frozen sample obtained in step eight was placed in a freeze dryer and dried under low-temperature vacuum at -90°C for 48 hours to remove water from the sample and obtain a dried sample. This removal of water yielded a layered hydroxyapatite nanocluster-polyvinyl alcohol composite measuring 4 cm in length and 2 cm in width. Figure 7 shows a scanning electron micrograph of this product, showing a layer thickness of approximately 2 microns and an interlayer spacing (solid arrows) of 20 microns. The freeze dryer used was an Alpha 1-2plus model from Christ, Germany.

[0092] In the tenth step, the freeze-dried hydroxyapatite nanoclusters and polyvinyl alcohol composite framework obtained in the ninth step are placed in a tablet press and compressed at 20 MPa for 2 h at room temperature to obtain a yellow dense block material.

[0093] In this embodiment, quasi-static nanoindentation and quasi-static three-point bending were used to test the enamel-like composite material prepared in Example 2. As shown in FIG8 , the hardness was 2.6 GPa, the modulus was 64.1 GPa, the flexural strength was 120 MPa, and the toughness was 5.6 MPa m 1 / 2 Scanning electron microscopy of the cross-section of the tested specimen revealed a multi-level structure similar to that of tooth enamel (as shown in Figure 9).

[0094] Example 3

[0095] A method for preparing a tooth enamel-like biomimetic composite material based on the directional assembly of hydroxyapatite nanoclusters and sodium alginate comprises the following steps:

[0096] In the first step, hydroxyapatite nanowires are added to a mixed solution of water and ethylene glycol, stirred at 25°C to form a uniform white suspension, and ferric chloride, magnesium sulfate, calcium chloride, and ammonium dihydrogen phosphate are added in sequence, and stirred at 40°C for 4 hours; wherein the concentration of the hydroxyapatite nanowires in the mixed solution is 0.53 mg / mL; the volume ratio of water to ethylene glycol is 1:19; the concentration of the ferric chloride in the reaction system is 0.1 mg / mL; the concentration range of the magnesium sulfate in the reaction system is 1.2 mg / mL; the concentration range of the calcium chloride in the reaction system is 0.1 mg / mL; and the concentration range of the ammonium dihydrogen phosphate in the reaction system is 0.26 mg / mL;

[0097] In the second step, the reaction product obtained in the first step is centrifuged and washed, and then frozen and placed in a freeze dryer for vacuum drying at a low temperature of -90°C for 48 hours to remove moisture in the sample, thereby obtaining a dry powder sample; wherein the centrifugal speed range is 10,000 r / min and the washing solvent is water;

[0098] The third step is to take the dried powder obtained in the second step and place it in a muffle furnace for calcination to obtain surface-modified hydroxyapatite nanowires; wherein the calcination temperature range is 300°C, the calcination time is 2 hours, and the heating rate is 10°C / min;

[0099] In the fourth step, the nanowires obtained in the third step are added to a mixture of water, ethanol, and oleic acid, stirred at 25°C to form a uniform light yellow suspension, and then a NaOH solution is added, stirred at 25°C for 30 minutes, and then transferred to a hydrothermal kettle for a hydrothermal reaction; wherein the concentration range of the nanowires in the mixture is 0.05 g / mL, the volume ratio of water, ethanol, and oleic acid is 1:1:1; the concentration of the NaOH solution is 0.2 g / mL; the temperature range of the hydrothermal reaction is 180°C, and the reaction time is 4 hours;

[0100] In the fifth step, the reaction product obtained in the fourth step is drawn into a syringe with a range of 5 mL, and then wet spinning is performed (as shown in FIG1 ). The reactant is injected into a coagulation bath containing ethanol and water, and allowed to stand for a period of time. The reactant is then centrifuged and washed, frozen, and placed in a freeze dryer and vacuum-dried at a low temperature of -90°C for 48 hours to remove moisture from the sample, ultimately obtaining a dry powder sample, i.e., the nanoclusters. The reactant injection rate is 0.5 mL / min, the volume ratio of ethanol to water is 4:1, and the standing time is 5 minutes. The centrifugal speed range is 10,000 r / min, and the washing solvent is water.

[0101] In the sixth step, 1 g of sodium alginate was dissolved in 35 mL of deionized water in an oil bath at 80° C., and stirred at a stirring rate of 300 rpm for 2 h to obtain 30 g of a uniformly mixed colorless transparent solution.

[0102] In the seventh step, 9 mL of the solution obtained in the sixth step was added with 0.81 g of nanoclusters, and the mixture was stirred in a water bath at 30°C at a stirring rate of 300 rpm for 48 h to form a uniform light yellow suspension.

[0103] In the eighth step, the light yellow suspension obtained in the seventh step was poured into a polytetrafluoroethylene mold containing a polydimethylsiloxane (PDMS) sloped bottom with an inclination angle of 20°. The device was then placed on a copper plate with dimensions of 30 cm long, 2 cm wide, and 0.5 cm thick. The copper plate was placed in the middle of a Dewar tank filled with liquid nitrogen. A magnetic field-assisted ice template assembly was performed (as shown in FIG2 ), and finally a macroscopic bulk composite material was generated. In the present invention, the freezing temperature provided by the liquid nitrogen was -120°C.

[0104] In step nine, the frozen sample obtained in step eight was placed in a freeze dryer and dried under low-temperature vacuum at -90°C for 48 hours to remove water from the sample and obtain a dried sample. This removal of water yielded a layered hydroxyapatite nanocluster-polyvinyl alcohol composite measuring 4 cm in length and 2 cm in width. Figure 10 shows a scanning electron micrograph of this product, showing a layer thickness of approximately 2 microns and an interlayer spacing (solid arrows) of 20 microns. The freeze dryer used was an Alpha 1-2plus model from Christ, Germany.

[0105] In the tenth step, the freeze-dried hydroxyapatite nanoclusters and polyvinyl alcohol composite framework obtained in the ninth step are placed in a tablet press and compressed at 20 MPa for 2 h at room temperature to obtain a yellow dense block material.

[0106] In this embodiment, quasi-static nanoindentation and quasi-static three-point bending were used to test the enamel-like composite material prepared in Example 3. As shown in FIG11 , the hardness was 3.1 GPa, the modulus was 72.8 GPa, the flexural strength was 130 MPa, and the toughness was 7.3 MPa m 1 / 2 Scanning electron microscopy of the cross-section of the tested specimen revealed that it had a multi-level structure similar to that of tooth enamel (as shown in Figure 12).

[0107] Although the embodiments of the present invention have been shown and described above, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a biomimetic enamel-like composite material having a multi-level substructure, characterized by: The following steps are involved: S1. Adding hydroxyapatite nanowires to a mixed solution of water and ethylene glycol, wherein the concentration of the hydroxyapatite nanowires in the mixed solution is in the range of 0.2-1 mg / mL; after stirring the mixture, ferric chloride, magnesium sulfate, calcium chloride, and ammonium dihydrogen phosphate are added in sequence, and the mixture is stirred and reacted at 30-80°C for 2-8 hours; wherein the concentration of the ferric chloride in the reaction system is in the range of 0.05-0.5 mg / mL; the concentration of the magnesium sulfate in the reaction system is in the range of 0.2-2 mg / mL; the concentration of the calcium chloride in the reaction system is in the range of 0.05-0.5 mg / mL; and the concentration of the ammonium dihydrogen phosphate in the reaction system is in the range of 0.1-2 mg / mL; S2. The reaction product obtained in step S1 was centrifuged, washed, and dried to obtain a dry powder sample; S3. calcining the dried powder obtained in step S2 to obtain surface-modified hydroxyapatite nanowires; S4. The surface-modified hydroxyapatite nanowires obtained in step S3 are added to a mixture of water, ethanol, and oleic acid, stirred uniformly, and then a NaOH solution is added and stirred, followed by a hydrothermal reaction at a temperature in the range of 150-200°C for a reaction time of 2-8 hours. The concentration of the surface-modified hydroxyapatite nanowires in the mixture is in the range of 0.01-0.1 g / mL. S5. The reaction product obtained in step S4 is wet-spinned and injected into a coagulation bath containing ethanol and water. The reactant is allowed to stand for a period of time, and then centrifuged, washed, and dried to obtain a dry powder sample, i.e., the nanoclusters; wherein the reactant injection rate is 0.1-1 mL / min; S6. dissolving a water-soluble organic polymer in water at 75 to 90° C. and stirring to obtain a polymer solution; wherein the mass ratio of the organic polymer to water is 1:(30-80); S7. Take the polymer solution obtained in step S6, add the nanoclusters obtained in step S5 and stir to obtain a nanocluster suspension; the concentration of the nanoclusters in the polymer solution is in the range of 0.03-0.15 g / mL; S8. The nanocluster suspension obtained in S7 was poured into a polytetrafluoroethylene mold containing a polydimethylsiloxane sloped bottom with an inclination angle of 5-25°. The device was then placed on a copper plate, which was placed in a Dewar tank filled with liquid nitrogen for magnetic field-assisted ice-templated assembly, ultimately generating a macroscopic bulk composite material. S9. The bulk composite material obtained in step S8 is dried to obtain a dried bulk sample; S10. The dried block sample obtained in step S9 is subjected to mechanical compression at room temperature, with a pressure range of 5-30 MPa and a compression time of 0.5-3 h.

2. The method for preparing a biomimetic enamel-like composite material with a multi-level structure according to claim 1, characterized in that: In step S1, the volume ratio of water to ethylene glycol is 1:(1-20).

3. The method for preparing a biomimetic enamel-like composite material with a multi-level structure according to claim 1, characterized in that: In step S3, the temperature range of the calcination conditions is 200-500° C., the calcination time is 1-4 hours, and the heating rate is 5-20° C. / min.

4. The method for preparing a biomimetic enamel-like composite material with a multi-level structure according to claim 1, characterized in that: In step S4, the volume ratio of water, ethanol and oleic acid is (1-2):1:(1-2).

5. The method for preparing a biomimetic enamel-like composite material with a multi-level structure according to claim 1, characterized in that: In step S4, the concentration of the NaOH solution is 0.1-0.5 g / mL.

6. The method for preparing a biomimetic enamel-like composite material with a multi-level structure according to claim 1, characterized in that: In step S5, a syringe with a measuring range of 1-5 mL is used to draw the reaction product obtained in step S4.

7. The method for preparing a biomimetic enamel-like composite material with a multi-level structure according to claim 1, characterized in that: In step S5, the volume ratio of ethanol to water is (1-4):1; and the standing time is 1-10 min.

8. The method for preparing a biomimetic enamel-like composite material with a multi-level structure according to claim 1, characterized in that: In step S6, the organic polymer includes polyvinyl alcohol, carboxymethyl cellulose, and sodium alginate.

9. An enamel-like biomimetic composite material with a multi-level structure prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the enamel-like biomimetic composite material with a multi-level substructure according to claim 9 in preparing a tooth defect repair material.

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