An ultra-elastic minimally invasive artificial bone scaffold based on additive manufacturing and a preparation method thereof

Abstract

The application discloses a super-elastic minimally invasive artificial bone support based on additive manufacturing and a preparation method thereof. The super-elastic minimally invasive artificial bone support is based on TPMS G-type interpenetrating lattice metamaterial and is composed of basic cells. Each of the basic cells is composed of three double G-type cells in XYZ three directions. The double G-type cell comprises a first G-type cell and a second G-type cell which are interpenetrated and have the same barycenter. The second G-type cell is coincident with the first G-type cell after being rotated by 180 degrees around the Z axis. The basic cell of the minimally invasive artificial bone support has higher biocompatibility and is more suitable for the growth of osteoblasts. In addition, the double G-type cell formed by the interpenetrating structure can also adjust and control the mechanical properties to realize super-elasticity. Better elasticity is more suitable for human implantation.

Description

Technical Field

[0001] This invention relates to the field of artificial bone scaffolds, specifically to a superelastic minimally invasive artificial bone scaffold based on additive manufacturing and its preparation method. Background Technology

[0002] In existing technologies, artificial bone scaffolds are typically implanted in the human body to improve bone remodeling in the repair of large-area bone defects and bone structure filling and support treatments. NiTi alloys are widely used in artificial bone scaffolds due to their unique superelasticity, shape memory properties, good biocompatibility, and corrosion resistance. The unique mechanical properties of NiTi alloys come from their two-phase structure: the monoclinic B19' martensite phase exhibits shape memory, while the cubic B2 austenite phase exhibits superelasticity. The austenite phase can interconvert with martensite under temperature influence. This allows it to be in an austenitic state at body temperature and a martensitic state below -40°C. When compressed at martensitic temperatures, its volume shrinks by 30%, and it can recover its shape through temperature-driven deformation after implantation in the human body.

[0003] like Figure 1 As shown, the basic structure constituting an artificial bone scaffold is typically the Gyroid structure in TPMS, i.e., G-type cells, and its basic equation can be expressed as:

[0004]

[0005] However, the basic structure composed of single G-type cells has a low specific surface area, which affects the elasticity and biocompatibility of the final artificial bone scaffold, causing some inconvenience for subsequent human implantation. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a superelastic minimally invasive artificial bone scaffold based on additive manufacturing and a method for preparing the same, so as to improve at least one of the above-mentioned problems.

[0007] This invention provides a superelastic minimally invasive artificial bone scaffold based on additive manufacturing. The superelastic minimally invasive artificial bone scaffold is based on TPMS G-type interpenetrating lattice metamaterial and is composed of basic cell arrangements. Each basic cell consists of three double G-type cells in each of the X, Y, and Z directions. The double G-type cells include a first G-type cell and a second G-type cell that are interpenetrating and have the same centroid. The second G-type cell coincides with the first G-type cell after being rotated 180 degrees around the Z-axis.

[0008] Preferably, the dimensions of the first G-type cell and the second G-type cell are 3mm×3mm×3mm, and the dimensions of the basic cell are 9mm×9mm×9mm.

[0009] Preferably, the minimally invasive artificial bone scaffold is printed using NiTi shape memory alloy powder.

[0010] Preferably, NiTi shape memory alloy powder with a near-equal atomic ratio is used, wherein the Ni content is 54.5-57wt% and the particle size range is 15-53μm.

[0011] Preferably, the austenite termination temperature of the superelastic minimally invasive artificial bone scaffold is 30.29℃, and the martensitic phase transformation termination temperature is -40.3℃.

[0012] Preferably, the porosity of the basic cell is 70%.

[0013] Preferably, the double G-type cell M is defined as:

[0014]

[0015] in:

[0016]

[0017]

[0018] G represents the surface involved in the synthesis. Let the coordinate vectors be Cartesian space coordinates. Let represent the implicit equation of the double G-type cell surface, where i represents the model order of the surface G involved in the synthesis, n is the total model order, and R is the rotation operator. This represents the coordinates of the rotation center of each model. Represents the rotation matrix;

[0019] definition:

[0020]

[0021] in, This represents the isosurface function extracted from field S. Indicates the interior of the model. Represents the model boundary. This represents the exterior of the model, where c is a model constant.

[0022] By adjusting parameters such as the angle of intersection, centroid, and number of combinations, it is possible to achieve the desired result when order i=2. , and take In this case, M is a double G-type cell unit.

[0023] This invention also provides a method for preparing a superelastic minimally invasive artificial bone scaffold based on additive manufacturing, comprising:

[0024] Provides NiTi shape memory alloy powder for additive manufacturing;

[0025] Additive printing is performed based on preset process and structural parameters to obtain a superelastic minimally invasive artificial bone scaffold composed of basic cell arrangements.

[0026] Preferably, the additive manufacturing process parameters are: laser power 140W, scanning speed 1200mm / s, laser scanning spacing 80μm, and powder thickness 30μm.

[0027] Compared with the prior art, the embodiments of the present invention have at least the following advantages:

[0028] 1. Compared with the existing single G-type cell structure, the dual G-type cell structure of this embodiment has higher biocompatibility and is more suitable for osteoblast growth;

[0029] 2. Under the same porosity conditions, compared with the existing single G-type cell structure, the double G-type cell structure of this embodiment has a higher specific surface area gain, and the higher specific surface area increases the load contact points at the mechanical level, further enhancing the load-bearing capacity.

[0030] 3. In this embodiment, the double G-cell structure formed by interpenetrating structure can achieve superelasticity by regulating mechanical properties. Compared with the existing single G-cell structure, it has better elasticity and is more suitable for human implantation, resulting in better implantation effect. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure of an existing single G-type cell.

[0032] Figure 2 This is a schematic diagram illustrating the formation of a basic cell in an embodiment of the present invention;

[0033] Figure 3 This is a schematic diagram illustrating the biocompatibility of the artificial bone scaffold; where, Figure 3 (a) is a schematic diagram of the biocompatibility of existing artificial bone scaffolds based on single G-type cells; Figure 3 (b) is a schematic diagram of the biocompatibility of the superelastic minimally invasive artificial bone scaffold according to an embodiment of the present invention;

[0034] Figure 4 This is a graph showing the yield strength of the artificial bone scaffold as a function of strain; where, Figure 4 (a) is a graph showing the change in yield strength of existing artificial bone scaffolds based on single G-cells as a function of strain; Figure 4 (b) is a graph showing the change in yield strength of the hyperelastic minimally invasive artificial bone scaffold as a function of strain in this embodiment;

[0035] Figure 5This is a static compression curve of the superelastic minimally invasive artificial bone scaffold of the present invention after different cycles;

[0036] Figure 6 This is a comparative schematic diagram showing the deformation recovery of artificial bone scaffolds; among which, Figure 6 (a) is a comparative schematic diagram of the deformation recovery of existing artificial bone scaffolds based on single G-type cells; Figure 6 (b) is a comparative schematic diagram of the deformation recovery of the superelastic minimally invasive artificial bone scaffold based on the double G-type cell structure in this embodiment. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Please see Figure 2 The first embodiment of the present invention provides a superelastic minimally invasive artificial bone scaffold based on additive manufacturing. The superelastic minimally invasive artificial bone scaffold is based on TPMS G-type interpenetrating lattice metamaterial and is composed of basic cells 10 arranged in a manner. Each of the basic cells 10 consists of three double G-type cells 20 in each of the X, Y, and Z directions. The double G-type cells 20 include a first G-type cell 21 and a second G-type cell 22 that are interpenetrating and have the same centroid. The second G-type cell 22 is rotated 180 degrees around the Z-axis and then coincides with the first G-type cell 21.

[0039] In this embodiment, the basic cell 10 can be understood as the basic unit constituting the artificial bone scaffold, which forms an overall structure by arranging multiple double G-type cells 20 in the XYZ directions. Specifically, the arrangement of the basic cells 10 can be precisely controlled by additive manufacturing technology, such as by using a layer-by-layer stacking method to construct a three-dimensional mesh layout, mainly to increase the cell density per unit volume, thereby expanding the surface exposed area.

[0040] In this embodiment, the ultra-elastic minimally invasive artificial bone scaffold is specifically printed using NiTi shape memory alloy powder. The NiTi shape memory alloy powder used has a near-equiatomic ratio, a Ni content of 54.5-57 wt%, and a particle size range of 15-53 μm.

[0041] In this embodiment, near-equal atomic ratio refers to a ratio in which the atomic numbers of nickel and titanium are nearly equal, which can be achieved by precisely controlling the raw material ratio. Specifically, the Ni content of 54.5-57 wt% is a weight percentage range set based on the difference in atomic weight between nickel and titanium, ensuring that the alloy exhibits stable phase transformation behavior. Furthermore, the particle size range of 15-53 μm is chosen to meet the requirements of additive manufacturing processes for powder flowability and spreading characteristics, aiming to avoid agglomeration problems caused by excessively fine powder and interlayer bonding defects caused by excessively coarse powder.

[0042] Specifically, in the fabrication of the aforementioned ultra-elastic minimally invasive artificial bone scaffold, NiTi shape memory alloy powder with a near-equal atomic ratio was used as the base material. By strictly controlling the Ni content within the range of 54.5-57 wt%, the martensitic phase transformation behavior could be effectively regulated, stabilizing the austenite termination temperature at a level close to human body temperature. Simultaneously, the limited particle size range ensured both uniform powder spreading during the printing process and dense forming of the scaffold structure with consistent pore distribution. This material selection and parameter limitation not only solved the phase transformation temperature drift problem caused by compositional deviations but also significantly improved the forming quality of the scaffold during additive manufacturing, thereby achieving the goal of stably exhibiting ultra-elastic recovery performance under human body temperature conditions.

[0043] Specifically, the austenite termination temperature of the superelastic minimally invasive artificial bone scaffold is 30.29℃, and the martensitic phase transformation termination temperature is -40.3℃.

[0044] In this embodiment, specifically, the porosity of the basic cell 10 is 70%.

[0045] Specifically, porosity refers to the proportion of pore volume to total volume in the basic cell 10, which can be achieved by adjusting the distribution density and size of the pores within the basic cell 10. In additive manufacturing, this parameter can be achieved by precisely controlling the printing path and material deposition method, for example, by employing a specific laser scanning strategy or adjusting the powder layer thickness. Setting the porosity to 70% aims to balance the mechanical properties and biocompatibility of the scaffold, ensuring that it provides sufficient support while also promoting cell attachment and nutrient exchange.

[0046] The following combination Figure 2 The structural composition of the basic cell 10 of the hyperelastic minimally invasive artificial bone scaffold in this embodiment is described in detail:

[0047] First, the first G-type cell 21 is provided.

[0048] Specifically, the dimensions of the first G-type cell 21 are 3mm × 3mm × 3mm.

[0049] Then, the provided first G-type cell 21 is copied and rotated 180 degrees around the Z-axis to form the second G-type cell 22.

[0050] Next, by moving the first G-type cell 21 and the second G-type cell 22, their centers of gravity (which are also the center since they are uniformly symmetrical) are made to coincide to obtain the double G-type cell 20. Since the centers of gravity of the two have actual structures, they will form an interpenetrating structure at the center of gravity, thus making the superelastic minimally invasive artificial bone scaffold based on TPMS G-type interpenetrating lattice metamaterial.

[0051] In this embodiment, the design of the double G-cell 20 employs two interpenetrating G-cell structures with overlapping centroids. This design enables the formation of a dense network through the interweaving of the two G-cells. For example, the first G-cell 21 and the second G-cell 22 can be defined geometrically through mathematical modeling, and their interpenetrating layout can be achieved through computer-aided design, thus significantly increasing the specific surface area.

[0052] The double G-type cell 20 can be represented by the following model:

[0053] The double G-type cell M is defined as:

[0054]

[0055] in:

[0056]

[0057]

[0058] G represents the surface involved in the synthesis. Let the coordinate vectors be Cartesian space coordinates. Let represent the implicit equation of the double G-type cell surface, where i represents the model order of the surface G involved in the synthesis, n is the total model order, and R is the rotation operator. This represents the coordinates of the rotation center of each model. Represents the rotation matrix;

[0059] definition:

[0060]

[0061] in, This represents the isosurface function extracted from field S. Indicates the interior of the model. Represents the model boundary. This represents the exterior of the model, where c is a model constant.

[0062] By adjusting parameters such as the angle of intersection, centroid, and number of combinations, it is possible to achieve the desired result when order i=2. , and take In this case, M is a double G-type cell unit.

[0063] Finally, three double G-type cells are formed in each of the XYZ directions, forming the basic cell 10.

[0064] Specifically, the basic cell has a size of 9mm×9mm×9mm, and the porosity of the overall structure is set at 70%, which is consistent with the porosity range of human tibial cancellous bone.

[0065] In this embodiment, after obtaining the basic cell 10, the final superelastic minimally invasive artificial bone scaffold can be obtained by repeatedly arranging the basic cell 10.

[0066] The performance of the ultra-elastic minimally invasive artificial bone scaffold of this embodiment will be verified through some experiments or simulations.

[0067] 1. Biocompatibility

[0068] Biocompatibility refers to the degree of interaction between a living organism or artificial material and a living organism. In the medical field, biocompatibility is an important indicator for evaluating the interaction between materials and human tissues. Appropriate biocompatibility plays a crucial role in the application of medical devices, biomedical materials, and tissue engineering. Poor biocompatibility of materials may lead to health risks for patients and reduced treatment outcomes. At the same time, excellent biocompatibility is also essential for the development of artificial organs, tissue engineering, and regenerative medicine. Through appropriate material selection and design, artificial organs and tissue-engineered products can achieve better compatibility, thereby improving their success rate and efficacy.

[0069] like Figure 3 (a) and Figure 3 As shown in (b), through comparison using cell fluorescence staining experiments, it was found that this embodiment ( Figure 3 (b) Compared to single G-type cells ( Figure 3 (a) The green fluorescence is dense and continuous, the cells spread more fully, and the cytoskeleton fiber network is more developed, which significantly promotes cell spreading and cytoskeleton formation. Therefore, this embodiment has better biocompatibility than single G-type cells.

[0070] 2. Elastic modulus and yield strength

[0071] Experimental results are as follows Figure 4 (a) and Figure 4 As shown in (b). Figure 4 (a) and Figure 4(b) The yield strength versus strain curves of the artificial bone scaffold formed by a single G-type cell structure and the artificial bone scaffold formed by the double G-type cell structure in this embodiment are shown in Table 1.

[0072] Table 1

[0073]

[0074] As can be seen from the yield strength corresponding to the fourth column of Table 1, in the elastic stage, the yield strength of this embodiment is 124.05, which is within the range of 10-200 for human bones. However, the yield strength of the artificial bone scaffold based on single G-cell is 299.35, which exceeds the range of human bones. This means that this embodiment is more suitable for artificial bone applications, while the artificial skeleton based on single G-cell may cause fractures of the human bones around the implant after implantation.

[0075] 3. Energy absorption effect

[0076] Human cancellous bone itself has a certain energy absorption and buffering capacity, and this embodiment better simulates the mechanical behavior of natural bone, avoids the "stress shielding effect", buffers external force impact, and reduces the risk of fracture.

[0077] Specifically, such as Figure 5 As shown, Figure 5 This is a static compression curve of the superelastic minimally invasive artificial bone scaffold of this invention after different cycles. In this embodiment, the recoverable strain after 10 compressions reaches 75.05% (the unrecoverable strain after the 10th compression is the intersection of the last line 10th Cycle and the X-axis, approximately 0.02495, therefore the recovery rate is (0.1-0.0245) / 0.1=75.05%), which demonstrates that this embodiment has excellent energy absorption performance.

[0078] 4. Structural recovery rate

[0079] Structural recovery rate is an important indicator for evaluating artificial bone scaffolds. This embodiment uses a cryogenic compression and body temperature recovery process to measure the deformation recovery rate of the artificial bone scaffold. The compression process involves cooling to a martensitic state using liquid nitrogen, compressing to 30%, and then restoring to body temperature. Dimensions before and after compression deformation are measured as follows: Figure 6 (a) and Figure 6 As shown in (b), the artificial bone scaffold based on the dual G-type cell structure in this embodiment has a pre-compression deformation dimension of 95 (e.g., Figure 6 (b) Left side), after compression deformation, it is 94.1 (e.g.) Figure 6 (b) Right side), the structural recovery rate can reach 99.1%, while the pre-compression deformation size of the artificial bone scaffold based on the single G-type cell structure is 86.2 (e.g. Figure 6 (a) Left side), after compression deformation, it is 82 (as shown in the image). Figure 6 (a) Right side), the structural recovery rate is 95.1%, which is less than that of this embodiment.

[0080] Experiments have shown that, compared with the prior art, the embodiments of the present invention have at least the following advantages:

[0081] 1. Compared with the existing single G-type cell structure, this embodiment has higher biocompatibility and is more suitable for osteoblast growth.

[0082] 2. Under the same porosity conditions, compared with the existing single G-type cell structure, the double G-type cell structure of this embodiment has a higher specific surface area gain, which increases the load contact points at the mechanical level and further enhances the load-bearing capacity.

[0083] 3. In this embodiment, the double G-type cell 20 formed by the interpenetrating structure can achieve superelasticity by adjusting the mechanical properties. Compared with the existing single G-type cell structure, the better elasticity is more suitable for human implantation. Experiments show that this embodiment can achieve 30% compression before surgery and automatic expansion after implantation during surgery, with a shape recovery rate of 99.1%, providing possibilities for minimally invasive orthopedic surgery.

[0084] 4. This embodiment has a better energy absorption effect, and the strain recovery after 10 compressions can reach 75.05%.

[0085] The second embodiment of the present invention also provides a method for preparing a superelastic minimally invasive artificial bone scaffold based on additive manufacturing according to any of the above embodiments, comprising:

[0086] Provides NiTi shape memory alloy powder for additive manufacturing;

[0087] Additive printing is performed based on preset process and structural parameters to obtain a superelastic minimally invasive artificial bone scaffold composed of basic cell arrangements.

[0088] Preferably, the additive manufacturing process parameters are: laser power 140W, scanning speed 1200mm / s, laser scanning spacing 80μm, and powder thickness 30μm.

[0089] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A superelastic minimally invasive artificial bone scaffold based on additive manufacturing, characterized in that, The superelastic minimally invasive artificial bone scaffold is composed of basic cell cells arranged in three directions: X, Y, and Z. Each basic cell cell consists of three double G-type cells. The double G-type cells include interpenetrating first G-type cells and second G-type cells with overlapping centers of gravity. The second G-type cell cell overlaps with the first G-type cell cell after rotating 180 degrees around the Z-axis.

2. The superelastic minimally invasive artificial bone scaffold based on additive manufacturing according to claim 1, characterized in that, The dimensions of the first G-type cell and the second G-type cell are 3mm×3mm×3mm, and the dimensions of the basic cell are 9mm×9mm×9mm.

3. The superelastic minimally invasive artificial bone scaffold based on additive manufacturing according to claim 1, characterized in that, The ultra-elastic minimally invasive artificial bone scaffold is printed using NiTi shape memory alloy powder.

4. The superelastic minimally invasive artificial bone scaffold based on additive manufacturing according to claim 3, characterized in that, The NiTi shape memory alloy powder used has a near-equal atomic ratio, with a Ni content of 54.5-57 wt% and a particle size range of 15-53 μm.

5. The superelastic minimally invasive artificial bone scaffold based on additive manufacturing according to claim 1, characterized in that, The austenite termination temperature of the superelastic minimally invasive artificial bone scaffold is 30.29℃, and the martensitic phase transformation termination temperature is -40.3℃.

6. The superelastic minimally invasive artificial bone scaffold based on additive manufacturing according to claim 1, characterized in that, The porosity of the basic cell is 70%.

7. The superelastic minimally invasive artificial bone scaffold based on additive manufacturing according to claim 1, characterized in that, The double G-type cell M is defined as: in: G represents the surface involved in the synthesis. Let the coordinate vectors be Cartesian space coordinates. Let represent the implicit equation of the double G-type cell surface, where i represents the model order of the surface G involved in the synthesis, n is the total model order, and R is the rotation operator. This represents the coordinates of the rotation center of each model. Represents the rotation matrix; definition: in, This represents the isosurface function extracted from field S. Indicates the interior of the model. Represents the model boundary. This represents the exterior of the model, where c is a model constant. By adjusting parameters such as the angle of intersection, centroid, and number of combinations, it is possible to achieve the desired result when order i=2. and take In this case, M is a double G-type cell unit.

8. A method for preparing a superelastic minimally invasive artificial bone scaffold based on additive manufacturing as described in any one of claims 1 to 7, characterized in that, include: Provides NiTi shape memory alloy powder for additive manufacturing; Additive printing is performed based on preset process and structural parameters to obtain a superelastic minimally invasive artificial bone scaffold composed of basic cell arrangements.

9. The preparation method according to claim 8, characterized in that, The additive manufacturing process parameters are: laser power 140W, scanning speed 1200mm / s, laser scanning spacing 80μm, and powder thickness 30μm.

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