Design method of bionic bone scaffold based on TPMS

Abstract

The application discloses a design method of a bionic bone support based on TPMS and belongs to the technical field of bionic bone supports. The application is based on G unit and D unit formulas, adjusts a bias function to generate G gradient unit and D homogeneous unit CAD models; uses a fusion function to fuse the G gradient unit and the D homogeneous unit CAD models to generate a GD radial fusion CAD model, adjusts the bias function of the G gradient unit by using an interpolation method to make the GD radial fusion CAD model reach a target average porosity; reduces the wall thickness of the GD radial fusion CAD model to form a GD radial fusion CAD model with wall thickness; then divides the GD radial fusion CAD model with wall thickness into a finite element simulation grid model and outputs an inp format simulation model file; imports the inp format simulation model file into HyperMesh software, repairs and divides the grid and exports an inp file format model. The porous support designed by the application considers different functional grading of natural bone structures and different cell morphological fusion, better meets the mechanical properties of a natural femur, and light weight design increases the specific surface area to provide more space for bone cell adhesion and growth.

Description

Technical Field

[0001] This invention belongs to the field of bionic bone scaffold technology, specifically relating to a design method for a bionic bone scaffold based on TPMS. Background Technology

[0002] Bone injury is a common clinical condition, and bone tissue engineering is an emerging treatment method that repairs and reconstructs damaged bone tissue by creating porous scaffolds that mimic the structure and physiological function of bone. Its advantages include addressing the limitations of traditional treatments such as the limited availability of autologous bone tissue, the high risks associated with allogeneic transplantation, and the limited effectiveness of drug therapy. Furthermore, bone tissue engineering allows for precise control of the scaffold's mechanical properties and bioactivity to meet the needs of diverse patients.

[0003] Commonly used methods for designing biomimetic bone scaffold structures include designing a homogeneous porous structure from a single cell, or forming different porous structures by combining single rods and nodes. However, these methods also have obvious drawbacks, such as: not conforming to the natural femur structure, stress concentration at the connection points, low specific surface area, and unsuitability for cell proliferation, differentiation, and nutrient transport.

[0004] Three-period minimal surface (TPMS) porous structures, due to their controllable parameter adjustment and periodic smooth surfaces, can effectively solve the above problems. Porous structures designed using the TPMS method can achieve smooth surface connections, have a large specific surface area, and interconnected pores, making them very suitable for the structural design of porous bone scaffolds. Among the many TPMS structures, Gyroid (G) surfaces and Diamond (D) surfaces are two common TPMS surface types. In TPMS porous structures made from G and D surfaces, by adjusting parameters such as the geometry and porosity of the G surface, a porous structure with mechanical properties similar to cancellous bone can be obtained. The D type, as an outer layer unit, is more advantageous than the G type in simulating cortical bone load bearing because, in terms of mechanical properties, the smoother wall of the D type can effectively alleviate stress concentration. The G-type porous structure has relatively small fluctuations and a longer plateau region on the stress-strain curve, exhibiting a more stable performance and being more suitable for energy absorption.

[0005] However, using G units in TPMS as an example, the radial gradient porous structure formed by selecting only one type of G unit still has shortcomings in simulating the characteristics of the real femur structure. It may also result in a low average porosity of the simulated outer cortical bone, which in turn leads to a low overall porosity of the porous structure. If the porosity is too high, it will reduce the strength of the porous structure and eventually cause it to fail. The transfer from cortical bone to cancellous bone should also be a smooth process. Summary of the Invention

[0006] To address the shortcomings of the existing technologies, this invention provides a design method for a biomimetic bone scaffold based on TPMS, which solves problems such as stress concentration, cell proliferation and differentiation, and nutrient transport caused by the porous structure.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A design method for a biomimetic bone scaffold based on TPMS includes the following steps:

[0009] (1) Based on the G-unit formula and the D-unit formula respectively, adjust the bias function to generate the G gradient unit CAD model and the D homogeneous unit CAD model on the Ntopology software respectively.

[0010] (2) Use the fusion function to fuse the G gradient unit CAD model and the D homogeneous unit CAD model to generate the GD radial fusion CAD model;

[0011] (3) Establish a CAD model A with the same shape but smaller size than the GD radial fusion CAD model. Use the fusion function to fuse the GD radial fusion CAD model and CAD model A to generate a GD radial fusion CAD model with wall thickness. Then use the interpolation method to adjust the bias function of the G gradient unit CAD model to achieve the target average porosity of the GD radial fusion CAD model with wall thickness.

[0012] (4) Reduce the wall thickness of the GD radial fusion CAD model with wall thickness to form a GD radial fusion CAD model with wall thickness.

[0013] (5) Divide the CAD model with wall thickness of GD radial fusion into a finite element simulation mesh model in Ntopology software, and finally output the simulation model file in inp format.

[0014] (6) Import the simulation model file in .inp format into HyperMesh software to repair and re-mesh it. Use C3D4 mesh type and 0.1mm mesh cell size. Export and save the .inp file format model again.

[0015] (7) Import the .inp format file model generated in step (6) into the display dynamics module of Abaqus software and perform quasi-static compression finite element simulation.

[0016] This invention directly imports the .inp file format model obtained in step (6) into the Abaqus dynamics simulation module for quasi-static compression simulation, obtaining the result data after the quasi-static compression finite element simulation. It then evaluates whether the yield strength and elastic modulus of the established model are within the range of yield strength and elastic modulus of cancellous bone and cortical bone, respectively. If they are within the range, then the established model is the target bionic bone scaffold. The designed target bionic bone scaffold model can be constructed using conventional methods in the art. For example, the .inp file format model obtained in step (6) can be exported as an STL model file using the Export command. The computer can then be connected to a 3D printer, and the STL model file can be transferred to the 3D printer for printing, thus obtaining the target bionic bone scaffold.

[0017] In a preferred embodiment of the present invention, in step (1), the formula for the G unit is Ψ. G (x,y,z)=cos(ωx)sin(ωy)+cos(ωy)sin(ωz)+cos(ωz)sin(ωx)-C1(x,y,z); D unit common

[0018] Ψ D (x,y,z)=sin(ωx)sin(ωy)sin(ωz)+cos(ωx)cos(ωy)sin(ωz)+

[0019] The formula is:

[0020] sin(ωx)cos(ωy)cos(ωz)+sin(ωx)sin(ωy)cos(ωz)-C2(x,y,z)

[0021] Where x, y, and z represent the x, y, and z directions in the Cartesian coordinate system; ω is a constant that determines the surface period, ω = 2Π / l, where l is the unit cell size; C1(x,y,z) and C2(x,y,z) represent the bias functions that determine the surface; Ψ G (x,y,z) and Ψ D (x,y,z) represent the formulas for the G and D units, respectively, and the TPMS function formulas.

[0022] In a preferred embodiment of the present invention, in step (1), the bias function C2 of the D homogeneous unit and the porosity P are used to determine the relationship between the bias function C2 and the porosity P. D The relationship formula is used to adjust the bias function so that the average porosity of the D homogeneous element CAD model is less than 50%; the bias function C2 of the D homogeneous element is related to the average porosity P. D The relationship formula is P D = (0.5002 + 0.4135C2) × 100%; C2 is a fixed value.

[0023] In a preferred embodiment of the present invention, in step (1), the porosity and pore size of the G gradient unit CAD model both increase in a gradient from the outside to the inside in the cross-section, and a minimum porosity P exists at the edge of the G gradient unit CAD model. out The center has the maximum porosity P in .

[0024] In a preferred embodiment of the present invention, in step (1), the bias function C1 of the gradient unit G and the porosity P are used to determine the relationship between the bias function C1 and the porosity P. G The relationship formula makes the average porosity of the G-gradient element CAD model 50-90%; the bias function C1 of the G-gradient element is related to the average porosity P. G The relationship formula is P G = (0.4998 + 0.3246C1) × 100%; where, the bias function C1 is a function related to the coordinates and is a variable; the expression for C1 is: C out =k(x 2 +y 2 )+C in C out Let P be the offset function value of the outer edge of the gradient element CAD model. out =(0.4998+0.3246C) out )×100%; C in Let P be the offset function value of the center of the gradient element CAD model. in =(0.4998+0.3246C) in )×100%; x and y are the coordinates of the point x and y where the xy plane intersects with the edge of the G gradient unit CAD model, respectively. In this invention, an upper, lower and left and right symmetrical CAD model is established with the origin (0,0,0) as the center in the three-dimensional Cartier coordinate system. Here, each z value in the xy plane is zero.

[0025] This invention P G = (0.4998 + 0.3246C1) × 100% and P D =(0.5002+0.4135C2)×100% was obtained by linear fitting of seven bias function C values ​​-0.8, -0.6, -0.4, -0.2, 0, 0.2, and 0.4, which correspond to seven porosity P values ​​respectively. The reliability (R) of both is 99.998%, which meets the requirement of more than 98%.

[0026] This invention is based on the bias function C1 of the G gradient unit and the porosity P G The relationship formula and the bias function C2 of the D homogeneous unit with porosity P DThe bias function is adjusted using the relational formula to make the average porosity of the GD radial fusion CAD model 50-90%. In practical applications, a GD radial fusion CAD model with a target average porosity can be selected according to actual needs. The bias function of the G gradient element CAD model is adjusted by interpolation to make the average porosity of the GD radial fusion CAD model the target average porosity.

[0027] The specific steps (1) are as follows: In the Create module of the Ntopology software, a cylindrical or cubic CAD model is created. Then, in the Math module, the G-element formula and the D-element formula are input, the bias function is adjusted respectively, and the Boolean subtraction command is used to generate the G-gradient element CAD model and the D-homogeneous element CAD model respectively.

[0028] More preferably, since the present invention targets a biomimetic bone scaffold that simulates the structure of the human femur (thigh bone), it is preferable to establish a cylindrical CAD model with a height-to-diameter ratio of 1-2.

[0029] In a preferred embodiment of the present invention, the fusion function is tan(ax), where a is a constant representing the fusion period; and x is the x-direction of the spatial coordinate system.

[0030] More preferably, the fusion function is tan(x / 2).

[0031] The specific steps (2) are as follows: First, create a fusion function tan(ax) in the Math module of the Ntopology software, then call up the Ramp fusion command, and finally use the Boolean intersection command to initially generate the GD radial fusion CAD model.

[0032] As a preferred embodiment of the present invention, in step (4), the wall thickness is reduced by decreasing the Thickness parameter through the Shell command, so that the porosity of the CAD model with wall thickness in the GD radial fusion is 50-90%.

[0033] In a preferred embodiment of the present invention, the wall thickness of the CAD model with GD radial fusion thickness is smaller than that of the GD radial fusion CAD model. The target porosity can be obtained by changing the magnitude of the reduced wall thickness.

[0034] As a preferred embodiment of the present invention, the outer layer of the CAD model with wall thickness of the GD radial fusion is a D homogeneous unit structure, and the inner layer is a G gradient unit structure. The porosity and pore size of the G gradient unit structure are both gradient changes that increase from the edge to the center along the radial direction.

[0035] The bias function C2 of the outer D homogeneous unit structure is set to a constant -0.4847, resulting in a D-unit porous structure CAD model with a porosity of 30%. The G-gradient unit porous structure uses a non-constant bias function C1, which is a coordinate-dependent function. This results in a G-unit model where the porosity gradually increases from the edge towards the center, and the pore size also increases radially from the edge to the center, exhibiting a gradient change. However, it's crucial to ensure that the overall G-gradient unit CAD model's porosity and pore size remain within the ranges of 50%–90% and 100μm–1200μm, respectively. The proportion of G-gradient units in the GD radially fused CAD model with wall thickness can be adjusted by changing the InMax value in the fusion command Ramp. When InMax is 0, the fused model consists entirely of outer D homogeneous unit porous structures. As the InMax value increases, the proportion of G-gradient units gradually increases from the center outwards.

[0036] In a preferred embodiment of the present invention, the unit cell size L1 of the D homogeneous unit structure is L1 = 2mm × 2mm × 2mm; and the unit cell size L2 of the G gradient unit structure is L2 = 2mm × 2mm × 2mm.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention uses a new fusion method in structural design to fuse Gyroid surface and Domaind surface in multiple forms, and designs a novel biomimetic bone scaffold by adjusting the bias function parameters and wall thickness. Its surface is smooth and glossy, the pores are interconnected, and the large specific surface area provides more space for bone cell adhesion and growth. It also conforms to the elastic modulus and yield strength of human cancellous bone and cortical bone. Attached Figure Description

[0038] Figure 1 Schematic diagrams of gradient porous structure generated by G-element and uniform porous cylinder generated by D-element; where (a) is a schematic diagram of CAD model of Gyroid radial gradient porous structure generated by G-element; and (b) is a schematic diagram of CAD model of Domaind homogeneous porous structure generated by D-element.

[0039] Figure 2 The unit cell bias C1 and porosity P are given by G. G The fitting relationship between them and the relationship between D-cell bias C2 and porosity P D The fitting relationship between them; (a) is the relationship between the G-cell bias C1 and the porosity P. G (a) shows the fitting relationship between the two; (b) shows the relationship between the D-cell bias C2 and the porosity P. D The fitting relationship between them.

[0040] Figure 3This is a schematic cross-sectional view of the CAD model of the GD radial fusion band wall thickness.

[0041] Figure 4 The diagram shows the GD radial fusion CAD models of GD1, GD2, and GD3 generated in Example 1, and the GD radial fusion CAD model GD4 with wall thickness.

[0042] Figure 5 Strain distribution maps of the upper surface of the finite element models GD1, GD2, GD3 and GD4 under different strains are generated for the elastic stage, where ε is the strain.

[0043] Figure 6 The diagram shows the yield strength and elastic modulus distribution of the porous structure samples GD1, GD2, GD3, and GD4 after the finite element simulation. Detailed Implementation

[0044] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0045] Example 1

[0046] A design method for a biomimetic bone scaffold based on TPMS includes the following steps:

[0047] (1) First, create a cylindrical CAD model with a diameter and height of 8mm × 12mm in the Create module of the Ntopology software. At this time, the coordinates (x, y, z) inside the cylinder are in the range of (-4≤x≤4, -4≤y≤4, -6≤z≤6). Then, input the G element formula Ψ as shown in Table 1 in the Math module. G (x,y,z) and the D-unit formula Ψ D (x,y,z).

[0048] Table 1

[0049]

[0050] Where x, y, and z represent the x, y, and z directions in a Cartesian coordinate system; ω is a constant, i.e., ω = 2Π / l determines the surface period; in this embodiment, the unit cell size is 2mm × 2mm × 2mm, and l is 2mm; C1(x,y,z) and C2(x,y,z) represent the bias functions that determine the surface, Ψ G (x,y,z) and Ψ D (x,y,z) represent the formulas for the G and D units, respectively, and the TPMS function formulas.

[0051] (2) Figure 2 As shown, using P D= (0.5002+0.4135C2)×100% linear relationship is set as C2(x,y,z) is a constant -0.4847, and a Domaind homogeneous porous structure CAD model with a porosity of 30% is formed using Boolean subtraction instructions.

[0052] (3) Set C1(x,y,z) to a function related to the coordinates. This will make the G gradient element CAD model have a minimum porosity P at the edge. out The center will also have the maximum porosity P. in The initial design scheme of the CAD model of the G gradient unit before fusion is shown in Table 2 below.

[0053] like Figure 2 As shown in Table 2, the specific calculation process of the initial design G gradient unit bias function is as follows: According to Table 2, each selected set of P... out and P in Using P G The linear relationship of (0.4998 + 0.3246C1) × 100% corresponds to a set of internal and external bias function values ​​C. in and C out Then follow C out =k(x 2 +y 2 )+C in The expression for the bias function of each G-unit is obtained using the form (k represents the rate of change from the central porosity to the edge porosity; the larger the k value, the faster the porosity changes with the coordinates, and each set of k values ​​is calculated using a special point method). In this embodiment: P in =80% Substitute into P in =(0.4998+0.3246C) in )×100% yields C in =0.9246; P out =20% Substitute into P out =(0.4998+0.3246C) out )×100% yields C out = -0.9236, then take the coordinates (4, 0, 0) of the special point where the xy plane intersects with the outermost edge of the cylinder with a diameter × height of 8mm × 12mm. Therefore, -0.9236 = k(4 2 +0 2 )+0.9246, yielding k=-0.1155. Similarly, the first two sets of k values ​​are 0 and -0.0963 respectively. In summary, the initial design G-element bias function is 0, -0.0963(x 2 +y 2 +0.771 and -0.1155(x) 2 +y 2After obtaining the three initial design G-unit bias functions (C1(x,y,z)) by adding 0.9246, the Boolean subtraction command is used to generate the CAD model of the Gyroid radial gradient porous structure.

[0054] Table 2

[0055]

[0056] (4) After generating the Gyroid radial gradient porous structure CAD model and the Domaind homogeneous porous structure CAD model in steps (1)(2)(3), the tan(ax) formula is introduced as the fusion formula (where a is a constant, representing the fusion period; x is the x-direction of the spatial coordinate system). In this embodiment, in order to better simulate the natural femur structure, the value of a is a = 1 / 2. Then, the Ramp fusion command is called up and the relevant parameters of the 8mm×12mm Domaind homogeneous porous structure CAD model and the Gyroid radial gradient porous structure CAD model generated in steps (2) and (3) are input. Then, the Shell shelling command is called up and Ramp is substituted into it (and the Thickness in Shell is 1.5mm and remains unchanged) to obtain the 8mm×12mm GD radial fusion CAD model. In this embodiment, the initial wall thickness of the GD radial fusion CAD model is selected when the cell size is 2mm×2mm×2mm, which is 1.5mm. When the wall thickness is ≥1.5mm, the porosity of the GD fusion CAD model remains unchanged. When the wall thickness value is greater than 0mm and less than 1.5mm, the smaller the value, the greater the porosity. The initial wall thickness can be designed according to the needs of different cell sizes.

[0057] Then, in the Ntopology software's Create module, a cylindrical CAD model with a diameter and height of 7mm × 10mm was created. The Boolean Intersect command was used to intersect and merge the 8mm × 12mm GD radial fusion CAD model generated by the Shell command with the 7mm × 10mm cylindrical CAD model using the tan(ax) fusion formula, forming a 7mm × 10mm cylindrical GD radial fusion CAD model with wall thickness. However, the overall average porosity of the resulting 7mm × 10mm cylindrical GD radial fusion CAD model with wall thickness was not the target average porosity of 50%.

[0058] Finally, in the Shell extraction command, the initial wall thickness parameter of 1.5mm for Thickness remains unchanged. Interpolation is used to fine-tune the parameters of the initial design G-gradient element bias functions in Table 2. Specifically, in the three initial design G-element bias functions, 0 remains unchanged, and -0.0963(x) is used. 2 +y 2Change the parameter adjustment from +0.751 to -0.1001(x) 2 +y 2 +0.771, -0.1155(x) 2 +y 2 The parameter adjustment was changed from +0.9246 to -0.1303(x) 2 +y 2 +0.907. (The interpolation method involves adjusting the G gradient unit bias function while checking whether the porosity of the GD radial fused CAD model with wall thickness is 50%. If it is not reached, the parameters are adjusted further.) When the average porosity of the GD radial fused CAD model with wall thickness is 50%, the actual G gradient unit scheme before fusion after fine-tuning is shown in Table 3 below.

[0059] Table 3

[0060]

[0061] (5) As shown in Table 4, the overall average porosity of the GD radial fusion CAD models with wall thicknesses formed after parameter adjustment for GD1, GD2, and GD3 is 50%. The schematic diagram of the model is shown below. Figure 4 As shown, GD1 serves as the control group, where both the G gradient unit structure and the D homogeneous unit structure have an average homogeneous porosity of 50%. Figure 3 As shown, the outer layer of the GD radial fusion CAD model is a D homogeneous unit structure, and the inner layer is a G gradient unit structure. The homogeneous porosity of the D homogeneous unit structure is 30%, and the G gradient unit structure has a gradient porosity. The porosity and pore size of the G gradient unit CAD model both increase in a gradient manner from the edge to the center along the radial direction.

[0062] (6) Selecting GD3 to reduce wall thickness for lightweight design to generate GD4: In the Shell command, the wall thickness is reduced by decreasing the Thickness parameter of the radially fused CAD model GD3 with wall thickness to form a 7mm×10mm radially fused CAD model GD4 with wall thickness, ultimately achieving the goal of lightweight design. A schematic diagram of the model is shown below. Figure 4 As shown in Table 4, the specific model parameters are as follows.

[0063] Table 4

[0064]

[0065]

[0066] (7) The final 7mm×10mm GD radial fusion CAD models GD4, GD1, GD2 and GD3 are initially divided into finite element simulation mesh models using the Mesh From Implicit Body command in Ntopology software. Finally, the simulation model file in inp format is output using the output command (Export FE Mesh).

[0067] (8) Import the simulation model file in .inp format into HyperMesh software to repair and re-mesh it. Use tetrahedral meshing, and set the mesh type to C3D4 with a mesh element size of 0.1mm. Then export and save the .inp format file model again.

[0068] (9) The four generated .inp format models were imported back into the Display Dynamics module of Abaqus software for quasi-static compression finite element simulation. The elastic modulus of 110 GPa and Poisson's ratio of 0.3 were set as the properties of Ti-6Al-4V material, and the mesh elements were set to yield failure when the maximum deformation ratio reached 1.5. At the same time, the boundary conditions for the compression of the porous structure were defined. A 60% displacement load was applied to the top surface, and the bottom surface constrained the translational and rotational degrees of freedom of the porous structure in the X, Y, and Z coordinate directions. The top surface constrained the translational and rotational degrees of freedom in the X, Y, and Z directions, allowing only translation in the Z direction. The top and bottom surfaces were rigid surfaces, and the friction coefficient between the rigid surfaces and the porous structure was 0.1. The total simulation time was set to 0.006 s.

[0069] like Figure 5 The deformation behavior and stress concentration distribution of four porous structures were simulated using the finite element method. Strain contour plots show that under load, the deformation of the support initially develops at the surface edges and then gradually propagates to the center of the support. Increasing the volume fraction of the inner layer leads to an increase in the equivalent stress of the porous structure because the increased porosity exacerbates the volume fraction difference between the internal supports and the surrounding connecting parts, thus worsening stress concentration. The stress in all supports is mainly concentrated at the center of the inclined supports and the fusion interface, which may make the structure more susceptible to failure. Therefore, reinforcing the stress concentration areas can improve the reliability of the structure.

[0070] Figure 6The results of the quasi-static compression finite element simulations of four different models are presented: 1. The yield strengths of GD1, GD2, and GD3 are slightly greater than the yield strength range of cortical bone (33-193 MPa) between 194.4 MPa and 253.4 MPa, while the yield strength of GD4, at 186.7 MPa, falls within the cortical bone range. 2. The elastic moduli of all four models are between 4.2 GPa and 6.6 GPa, all within the cortical bone elastic modulus range. However, only GD4, with an elastic modulus of 4.2 GPa, falls within the cancellous bone range. When a model meets the mechanical performance requirements of cortical bone, stress shielding is avoided. Therefore, in summary, only GD4 meets the mechanical performance requirements of the femur and avoids stress shielding.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A design method for a biomimetic bone scaffold based on TPMS, characterized in that, Includes the following steps: (1) Based on the G-element formula and the D-element formula respectively, adjust the bias function and generate the G gradient element CAD model and the D homogeneous element CAD model respectively on the Ntopology software. (2) Use the fusion function to fuse the G gradient unit CAD model and the D homogeneous unit CAD model to generate the GD radial fusion CAD model; (3) Establish a CAD model A with the same shape but smaller size than the GD radial fusion CAD model. Use the fusion function to fuse the GD radial fusion CAD model and CAD model A to generate a GD radial fusion CAD model with wall thickness. Then use the interpolation method to adjust the bias function of the G gradient unit CAD model to achieve the target average porosity of the GD radial fusion CAD model with wall thickness. The interpolation method involves adjusting the G gradient unit bias function while checking whether the porosity of the GD radial fusion CAD model with wall thickness is the target average porosity. If it is not reached, the parameters are adjusted further. (4) Reduce the wall thickness of the GD radial fusion CAD model with wall thickness to form a GD radial fusion CAD model with wall thickness. (5) Divide the CAD model with wall thickness of GD radial fusion into a finite element simulation mesh model in Ntopology software, and finally output the simulation model file in inp format; (6) Import the simulation model file in .inp format into HyperMesh software to repair and re-mesh it. Use C3D4 mesh type and 0.1mm mesh cell size. Export and save the .inp file format model again. In step (1), the formula for unit G is: ; The formula for unit D is: ; in x, y, z Represents the x, y, and z directions in a Cartesian coordinate system; The constant determines the period of the surface. =2Π / l , l The constant represents the edge length of the unit cell; and This represents the bias function that determines the surface. and The formulas for G-cell and D-cell are respectively represented by the TPMS function formulas.

2. The design method of the biomimetic bone scaffold based on TPMS as described in claim 1, characterized in that, In step (1), the bias function C2 of the homogeneous unit D and the porosity P are used as the basis for the calculation. D The relationship formula is used to adjust the bias function so that the average porosity of the D homogeneous element CAD model is less than 50%. The bias function C2 of the D homogeneous element is related to the average porosity P. D The relationship formula is P D =(0.5002 +0.4135 C2)× 100%.

3. The design method of the biomimetic bone scaffold based on TPMS as described in claim 1, characterized in that, In step (1), the porosity and pore size of the G gradient unit CAD model both increase in a gradient from the outside to the inside on the cross-section, and a minimum porosity P exists at the edge of the G gradient unit CAD model. out The center has the maximum porosity P in .

4. The design method of the biomimetic bone scaffold based on TPMS as described in claim 3, characterized in that, In step (1), the bias function C1 of the gradient unit G and the porosity P are used as the basis for the calculation. G The relationship formula makes the average porosity of the G-gradient element CAD model 50-90%; the bias function C1 of the G-gradient element is related to the average porosity P. G The relationship formula is P G = (0.4998 + 0.3246 C1) × 100%; where the expression for the bias function C1 is: = ( )+ ,in G is the offset function value of the outer edge of the gradient unit CAD model, P out = (0.4998 +0.3246 C out ) × 100%; Let P be the offset function value of the center of the gradient element CAD model. in = (0.4998 +0.3246 C in ) × 100%.

5. The design method of the biomimetic bone scaffold based on TPMS as described in claim 1, characterized in that, The fusion function is tan(ax), where a is a constant representing the fusion period; and x is the x-direction of the spatial coordinate system.

6. The design method of the biomimetic bone scaffold based on TPMS as described in claim 1, characterized in that, In step (4), the wall thickness is reduced by decreasing the Thickness parameter through the Shell command, so that the porosity of the CAD model with wall thickness in the GD radial fusion is 50%-90%.

7. The design method of the biomimetic bone scaffold based on TPMS as described in claim 6, characterized in that, The wall thickness of the CAD model with the GD radial fusion band is smaller than that of the GD radial fusion CAD model.

8. The design method of the biomimetic bone scaffold based on TPMS as described in claim 1, characterized in that, The outer layer of the CAD model with GD radial fusion and wall thickness is a D homogeneous unit structure, and the inner layer is a G gradient unit structure. The porosity and pore size of the G gradient unit structure are both gradient changes that increase from the edge to the center along the radial direction.

9. The design method of the biomimetic bone scaffold based on TPMS as described in claim 8, characterized in that, The cell size L1 of the D homogeneous unit structure is L1 = 2mm × 2mm × 2mm; The cell size L2 of the G gradient unit structure is L2 = 2mm × 2mm × 2mm.

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