Shape memory alloy bone scaffold imitating Haversian system as well as 4D printing preparation method and application

Abstract

The invention discloses a shape memory alloy bone scaffold imitating a Haversian system as well as a 4D printing preparation method and application of the shape memory alloy bone scaffold. According to the 4D printing preparation method, the stress state and function requirements of the bone scaffold are fully considered, a bone scaffold porous structure with an imitated Haversian system is designed by adopting a function bionic method, and the bone scaffold is prepared by adopting a 4D printing technology. The inner layer imitated cancellous bone porous structure designed in the preparation method not only meets the requirement that the inner layer has good elasticity and toughness, but also facilitates cell adhesion to guide cell growth and maintains blood supply; the designed artificial cortical bone porous structure with the Haversian system on the outer layer meets the requirement that the outer layer has good compression resistance and bending resistance, and the Haversian system is more beneficial to ingrowth of blood vessels and nerves and maintains skeleton metabolism and repair. The shape memory alloy bone scaffold simulating the Haversian system, disclosed by the invention, has a wide application prospect in the field of bone implants.

Description

Technical Field

[0001] The present invention belongs to the fields of additive manufacturing, metal materials and biomedical engineering, and specifically relates to a shape memory alloy bone scaffold imitating a Haversian system and a 4D printing preparation method and application. Background Art

[0002] As people age, their bone density gradually decreases, their bone structure changes, and their bone strength weakens, leading to an increased risk of fractures. As the population ages, society's demand for the quantity and quality of bone implants is increasing. Hard bones are the most common type of bones in the human body, and are mainly responsible for support, protection, and movement. Hard bones include long bones, short bones, flat bones, and irregular bones. Considering strength and durability, hard bones are often replaced by metal implants. The commonly used materials for orthopedic implants are mostly titanium alloys, magnesium alloys, nickel-titanium alloys, etc. Among them, nickel-titanium alloys have high strength, low modulus, excellent biocompatibility, and unique superelasticity and shape memory effects, and have great potential in the direction of biomedical bone scaffolds.

[0003] From the Haversian anatomy, we know that bones are porous structures with highly complex pores. The cancellous bone fills the inside of the bone, and its porosity is usually above 30%, which has high elasticity. The outer layer is cortical bone with the Haversian system, with a porosity as low as 5%, and its compressive strength is higher than that of cancellous bone. The periosteum, outer ring periosteum, Haversian canal, osteon, interosseous plate, Volkmann canal, inner ring bone plate and endosteum together form a complex Haversian system ( Figure 1 ), Haversian canal is a longitudinal canal, which contains blood vessels and nerves to provide nutrition and oxygen to bone cells and discharge metabolic waste; Volkmann canal crosses the bone and connects with the central canal, which is an important channel for blood vessels and nerves to enter the bone. Cortical bone, cancellous bone and Haversian system together constitute a complete bone structure system. They are interrelated in structure and function, and work together to maintain the normal physiological function of bone tissue.

[0004] In order to facilitate patient recovery and avoid stress shielding, bone implants mostly adopt porous structures. However, in the existing studies, in terms of bone scaffold design, most of them are bone scaffolds with a single porosity, which cannot truly meet the complex functional requirements of implants. In order to further meet the needs of patients, bionic designs inspired by bones have attracted the attention of many scholars. For example, CN117100460A effectively improves the stress shielding effect by opening holes on the surface of the scaffold, improves the connectivity of the pores, and provides favorable conditions for cell growth. CN110876817B discloses a bionic bone component with a multilayer structure and a preparation method thereof, which improves bone repair performance. Science Advances 2020 (12) designed and prepared a bone simulation scaffold with Haversian tubes and Volkmann tubes, in which the cancellous bone is designed into a mesh structure, but the cortical bone is a solid structure with longitudinal openings. The ceramic scaffold has good mechanical properties and biocompatibility. At present, there are few reports on the design and preparation of shape memory alloy porous bone scaffolds that introduce Haversian-like systems. Therefore, this patent takes into account the stress state and functional requirements of the stent, designs and prepares a shape memory alloy stent with a Haversian system, in which the inner layer of cancellous bone and the outer layer of cortical bone are both porous structures.

[0005] The preparation methods of porous bone scaffolds mainly include traditional machining, spark plasma sintering, hot isostatic pressing, direct foaming, high temperature self-propagating and other processes. However, the pore size and shape prepared by these traditional methods are randomly distributed, and quantitative control is limited. It is difficult to prepare high-porosity bone scaffolds. In addition, the instability of the preparation process makes it impossible to provide stable mechanical properties of the bone scaffold, and the material utilization rate is low. Emerging additive manufacturing technologies include 3D printing technologies such as laser directed energy deposition, laser powder bed melting, selective electron beam melting, and arc additive manufacturing, which can achieve highly controllable and interconnected pore shapes of bone scaffolds. In particular, laser powder bed melting 3D printing shape memory alloys, also known as 4D printing, can accurately control the laser beam and energy density, so that the pore size, porosity accuracy and performance stability of the bone scaffold are guaranteed. Summary of the invention

[0006] In order to overcome the deficiencies and shortcomings of the prior art, the primary purpose of the present invention is to provide a 4D printing preparation method for a shape memory alloy bone scaffold that imitates the Haversian system. The preparation method applies the Haversian system of human anatomy to the design of a shape memory alloy porous bone scaffold for functional bionics, and uses a 4D printing process to prepare the bone scaffold, so that the functional properties of the bone scaffold, such as mechanical properties, stability and mass transfer, are closer to those of natural bones, thereby providing an effective way for the design and preparation of bone scaffolds.

[0007] The second object of the present invention is to provide a shape memory alloy bone scaffold imitating the Haversian system prepared by the above-mentioned 4D printing preparation method. The shape memory alloy bone scaffold imitating the Haversian system prepared by the present invention not only has good biocompatibility, can meet the growth function of osteoblasts, blood vessels, and nerves, but also has good mechanical properties, can avoid stress shielding effect and has a certain load-bearing capacity.

[0008] The third object of the present invention is to provide an application of a shape memory alloy bone scaffold that simulates the Haversian system.

[0009] The primary purpose of the present invention is achieved through the following technical solutions:

[0010] A 4D printing preparation method for a shape memory alloy bone scaffold imitating a Haversian system comprises the following steps:

[0011] Step 1: 3D modeling and design of shape memory alloy bone scaffold imitating Haversian system

[0012] Design the inner layer to simulate the porous structure of cancellous bone and the outer layer to simulate the porous structure of cortical bone with Haversian system ( Figure 2 ), using 3D modeling software to perform Boolean sum operations, so that the inner layer of the cancellous bone-like porous structure and the outer layer of the cortical bone-like porous structure with the Haversian system are radially fused to form a complete Haversian-like shape memory alloy bone scaffold;

[0013] Step 2: 3D model slicing

[0014] The STL files of the inner layer simulated cancellous bone porous structure and the outer layer simulated cortical bone porous structure with Haversian system are respectively imported into the slicing software for slicing processing, and the sliced ​​files are imported into the 4D printing additive manufacturing system;

[0015] Step 3: 4D printing process to prepare shape memory alloy bone scaffolds imitating Haversian system

[0016] First, a NiTi alloy substrate is preheated, and shape memory alloy powder is placed in a powder chamber. Then, the oxygen content in the forming chamber is adjusted, and forming process parameters are given to an inner layer of a cancellous bone-imitation porous structure and an outer layer of a cortical bone-imitation porous structure with a Haversian system, respectively. After forming, a shape memory alloy bone scaffold imitating a Haversian system is obtained; different laser powers and scanning speeds are given to the inner layer of a cancellous bone-imitation porous structure and the outer layer of a cortical bone-imitation porous structure with a Haversian system according to the rod diameter and the curved surface thickness.

[0017] Preferably, the inner layer of cancellous bone-mimicking porous structure in step one is a strut-based porous unit, and the strut-based porous unit is one of an octahedron, a regular cube, a body-centered cube, a face-centered cube, a dodecahedron or a diamond, and its unit size is 0.6 to 1.8 mm, its rod diameter is 140 to 500 μm, its pore diameter is 80 to 1200 μm, and its porosity is 50 to 90%.

[0018] Preferably, the outer layer of the cortical bone-like porous structure with the Haversian system in step one is a porous unit based on a three-periodic minimal surface, and the porous unit based on the three-periodic minimal surface is one of Gyroid, Diamond, Neovius or Lidinoid, with a unit size of 0.6 to 1.8 mm, a surface thickness of 150 to 450 μm, a pore size of 80 to 1200 μm, and a porosity of 10% to 80%.

[0019] Preferably, in step 1, the outer layer of the simulated cortical bone porous structure with the Haversian system is designed to be a simulated Haversian tube arranged in concentric circles in the longitudinal direction and a simulated Volkmann tube arranged in concentric circles in the transverse direction.

[0020] Preferably, the simulated Haversian tubes have a diameter of 80 to 500 μm, and the number thereof is 12 to 36; the simulated Volkmann tubes have a diameter of 80 to 500 μm, and the number thereof is 12 to 36.

[0021] Preferably, the 3D modeling software in step 1 includes 3D Max, Rhino, Fusion 360, SolidWorks, UG, Materialise Magics, and nTopology.

[0022] Preferably, in step three, the preheating temperature of the NiTi alloy substrate is 190-210° C.; the shape memory alloy powder is one of NiTi, NiTiNb, NiTiCr, NiTiFe, and NiTiCu, and the particle size of the shape memory alloy powder is 15-53 μm; and the oxygen content in the forming chamber is controlled within 100 ppm.

[0023] Preferably, in step three, the laser power of the inner layer of cancellous bone-imitation porous structure is 70-200W, and the scanning speed is 400-2000mm / s; the laser power of the outer layer of cortical bone-imitation porous structure with Haversian system is 80-220W, and the scanning speed is 600-2200mm / s.

[0024] Preferably, the forming process parameters of the inner layer cancellous bone-mimicking porous structure in step 3 are as follows: the spot diameter is 75-85 μm, the scanning interval is 60-100 μm, the layer thickness is 30-40 μm, and the printing strategy is to rotate the laser path by 65-75° every other layer;

[0025] The outer layer has a Haversian system for forming a porous structure of simulated cortical bone. The process parameters are as follows: a spot diameter of 75 to 85 μm, a scanning interval of 60 to 100 μm, a layer thickness of 30 to 40 μm, and a printing strategy of rotating the laser path by 65 to 75° for every other layer.

[0026] The second object of the present invention is achieved by the following technical solutions:

[0027] A shape memory alloy bone scaffold imitating a Haversian system is prepared by the above-mentioned 4D printing preparation method.

[0028] Preferably, the Haversian-simulated shape memory alloy bone scaffold comprises an inner layer of cancellous bone-simulated porous structure and an outer layer of cortical bone-simulated porous structure with a Haversian system.

[0029] The third object of the present invention is achieved by the following technical solutions:

[0030] Application of a shape memory alloy bone scaffold imitating the Haversian system in bone implants.

[0031] Specifically, the specific size parameters of the bone implant depend on the bone part, which is the humerus, ulna, radius, metacarpal, phalanges; femur, tibia, fibula, metatarsal, tarsal, phalanges, sternum, ribs or pelvic bones.

[0032] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0033] In the 4D printing preparation method of the shape memory alloy bone scaffold imitating the Haversian system described in the present invention, the stress state and functional requirements of the bone scaffold are fully considered, and the porous structure of the bone scaffold with the Haversian system is designed by using the functional bionic method, and the bone scaffold is prepared by using the 4D printing process. The inner layer of the porous structure of the simulated cancellous bone designed in the preparation method not only satisfies the inner layer to have good elasticity and toughness, but also facilitates cell adhesion and guides cell growth to maintain blood supply; the outer layer of the designed porous structure of the simulated cortical bone with the Haversian system satisfies the outer layer to have good compression and bending resistance, and the Haversian system is more conducive to the growth of blood vessels and nerves, maintaining bone metabolism and repair. The present invention imports the sliced ​​file into the 4D printing additive manufacturing system; it is convenient to assign the process parameters separately in the subsequent process. The shape memory alloy bone scaffold imitating the Haversian system prepared by the present invention not only has good biocompatibility, can meet the growth function of osteoblasts, blood vessels, and nerves, but also has good mechanical properties, can avoid the stress shielding effect and has a certain bearing capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the bone structure with the Haversian system;

[0035] Figure 2 Schematic diagram of the structure of the shape memory alloy bone scaffold that imitates the Haversian system;

[0036] Figure 3 A three-dimensional image of the shape memory alloy bone scaffold imitating the Haversian system in Example 1;

[0037] Figure 4 The physical picture of the Gyroid three-periodic minimal surface structure and the octahedron structure in Example 1;

[0038] Figure 5 This is a performance diagram of the Gyroid three-periodic minimal surface structure in Example 1;

[0039] Figure 6 This is the performance diagram of the octahedral structure in Example 1;

[0040] Figure 7 A three-dimensional image of the shape memory alloy bone scaffold simulating the Haversian system in Example 3;

[0041] Figure 8 A three-dimensional image of the shape memory alloy bone scaffold simulating the Haversian system in Example 5;

[0042] Fig. 9 A flow chart of the preparation process of shape memory alloy bone scaffolds that mimic the Haversian system;

[0043] Fig.10 It is a three-periodic minimal surface porous structure that cannot be formed in Comparative Example 1;

[0044] Fig.11 This is the performance diagram of the octahedral porous structure in Comparative Example 2. DETAILED DESCRIPTION

[0045] The present invention is further described in detail below in conjunction with specific embodiments and drawings, but the embodiments of the present invention are not limited thereto. The materials used in the examples of the present invention can all be purchased commercially.

[0046] Example 1

[0047] A 4D printing preparation method of a shape memory alloy bone scaffold imitating a Haversian system comprises the following steps:

[0048] Step 1: Design of shape memory alloy bone scaffolds imitating Haversian system

[0049] Inner layer: porous structure imitating cancellous bone, the unit type is an octahedral structure based on struts, the unit size is 0.6mm, the rod diameter is 140μm, the pore size is 450μm, and the porosity is 50%;

[0050] Outer layer: A porous structure imitating cortical bone with a Haversian system. The unit type is a Gyroid three-periodic minimal surface structure. The unit size is 0.6mm, the surface thickness is 225μm, the pore size is 600μm, and the porosity is 25%. In the outer layer, 36 concentrically arranged Haversian tubes with a diameter of 450μm are designed longitudinally, and 36 concentrically arranged Volkmann tubes with a diameter of 450μm are designed transversely.

[0051] Step 2: Preparation of shape memory alloy bone scaffolds imitating the Haversian system

[0052] 1) The STL files of the inner layer cancellous bone-simulating porous structure and the outer layer cortical bone-simulating porous structure with Haversian system are respectively imported into the slicing software for slicing processing, and the sliced ​​files are imported into the 4D printing additive manufacturing system.

[0053] 2) Preparation of Haversian-like shape memory alloy bone scaffolds by 4D printing

[0054] Preheat the NiTi alloy substrate to 190°C, place NiTi shape memory alloy powder with a particle size of 15 to 53μm in the powder chamber, and control the oxygen content in the 4D printing chamber to 100ppm. The process parameters of the inner layer of cancellous bone-like porous structure are as follows: laser power of 90W, scanning speed of 400mm / s, spot diameter of 75μm, scanning spacing of 60μm, layer thickness of 30μm, and the printing strategy is to rotate the laser path 65° every other layer. The process parameters of the outer layer of cortical bone-like porous structure with Haversian system are as follows: laser power of 80W, scanning speed of 600mm / s, spot diameter of 75μm, scanning spacing of 60μm, layer thickness of 30μm, and the printing strategy is to rotate the laser path 65° every other layer. Figure 3 This is a three-dimensional diagram of the shape memory alloy bone scaffold that simulates the Haversian system in this embodiment. Figure 4 The actual picture of the Gyroid three-period minimal surface structure and the octahedron structure in this embodiment is as follows: Figure 5 The structure diagram of the Gyroid three-period minimal surface in this embodiment and Figure 6 This is a performance diagram of the octahedral structure in this embodiment.

[0055] Example 2

[0056] A 4D printing preparation method of a shape memory alloy bone scaffold imitating a Haversian system comprises the following steps:

[0057] Step 1: Design of shape memory alloy bone scaffold imitating Haversian system

[0058] Inner layer: porous structure imitating cancellous bone, the unit type is an octahedral structure based on struts, the unit size is 0.6mm, the rod diameter is 140μm, the pore size is 450μm, and the porosity is 50%;

[0059] Outer layer: A porous structure imitating cortical bone with a Haversian system. The unit type is a Gyroid three-periodic minimal surface structure. The unit size is 0.6mm, the surface thickness is 225μm, the pore size is 600μm, and the porosity is 25%. In the outer layer, 36 concentrically arranged Haversian tubes with a diameter of 250μm are designed longitudinally, and 36 concentrically arranged Volkmann tubes with a diameter of 250μm are designed transversely.

[0060] Step 2: Preparation of shape memory alloy bone scaffolds imitating the Haversian system

[0061] 1) The STL files of the inner layer cancellous bone-simulating porous structure and the outer layer cortical bone-simulating porous structure with Haversian system are respectively imported into the slicing software for slicing processing, and the sliced ​​files are imported into the 4D printing additive manufacturing system.

[0062] 2) Preparation of Haversian-like shape memory alloy bone scaffolds by 4D printing

[0063] The NiTi alloy substrate was preheated to 210°C, and the NiTi shape memory alloy powder with a particle size of 15 to 53 μm was placed in the powder cabin, and the oxygen content of the 4D printing cabin was controlled to 100 ppm. The process parameters of the inner layer of cancellous bone-like porous structure were as follows: laser power of 200 W, scanning speed of 2000 mm / s, spot diameter of 75 μm, scanning spacing of 60 μm, layer thickness of 30 μm, and the printing strategy was to rotate the laser path 65° every other layer. The process parameters of the outer layer of cortical bone-like porous structure with Haversian system were as follows: laser power of 220 W, scanning speed of 2200 mm / s, spot diameter of 75 μm, scanning spacing of 60 μm, layer thickness of 30 μm, and the printing strategy was to rotate the laser path 65° every other layer.

[0064] Example 3

[0065] A 4D printing preparation method for a shape memory alloy bone scaffold imitating a Haversian system comprises the following steps:

[0066] Step 1: Design of shape memory alloy bone scaffold imitating Haversian system

[0067] Inner layer: porous structure imitating cancellous bone, the unit type is a diamond structure based on struts, the unit size is 1.8mm, the rod diameter is 400μm, the pore size is 900μm, and the porosity is 80%;

[0068] Outer layer: A porous structure imitating cortical bone with a Haversian system. The unit type is a Lidinoid three-periodic minimal surface structure. The unit size is 1.8 mm, the surface thickness is 200 μm, the pore size is 600 μm, and the porosity is 25%. In the outer layer, 36 concentrically arranged Haversian tubes with a diameter of 450 μm are designed longitudinally, and 36 concentrically arranged Volkmann tubes with a diameter of 450 μm are designed transversely.

[0069] Step 2: Preparation of shape memory alloy bone scaffolds imitating the Haversian system

[0070] 1) The STL files of the inner layer cancellous bone-simulating porous structure and the outer layer cortical bone-simulating porous structure with Haversian system are respectively imported into the slicing software for slicing processing, and the sliced ​​files are imported into the 4D printing additive manufacturing system.

[0071] 2) Preparation of Haversian-like shape memory alloy bone scaffolds by 4D printing

[0072] Preheat the NiTi alloy substrate to 190°C, place NiTi shape memory alloy powder with a particle size of 15 to 53μm in the powder chamber, and control the oxygen content of the 4D printing chamber to 100ppm. The process parameters of the inner layer of cancellous bone-imitation porous structure are as follows: laser power of 70W, scanning speed of 600mm / s, spot diameter of 75μm, scanning spacing of 60μm, layer thickness of 30μm, and the printing strategy is to rotate the laser path 65° every other layer. The process parameters of the outer layer of cortical bone-imitation porous structure with Haversian system are as follows: laser power of 90W, scanning speed of 400mm / s, spot diameter of 75μm, scanning spacing of 60μm, layer thickness of 30μm, and the printing strategy is to rotate the laser path 65° every other layer. Figure 7 3D diagram of the shape memory alloy bone scaffold simulating the Haversian system in this embodiment.

[0073] Example 4

[0074] A 4D printing preparation method for a shape memory alloy bone scaffold imitating a Haversian system comprises the following steps:

[0075] Step 1: Design of shape memory alloy bone scaffolds imitating Haversian system

[0076] Inner layer: porous structure imitating cancellous bone, the unit type is a diamond structure based on struts, the unit size is 0.9mm, the rod diameter is 200μm, the pore size is 900μm, and the porosity is 80%;

[0077] Outer layer: A porous structure imitating cortical bone with a Haversian system. The unit type is a Lidinoid three-periodic minimal surface structure. The unit size is 1mm, the surface thickness is 100μm, the pore size is 600μm, and the porosity is 25%. In the outer layer, 36 concentrically arranged Haversian tubes with a diameter of 300μm are designed longitudinally, and 36 concentrically arranged Volkmann tubes with a diameter of 300μm are designed transversely.

[0078] Step 2: Preparation of shape memory alloy bone scaffolds imitating the Haversian system

[0079] 1) The STL files of the inner layer cancellous bone-simulating porous structure and the outer layer cortical bone-simulating porous structure with Haversian system are respectively imported into the slicing software for slicing processing, and the sliced ​​files are imported into the 4D printing additive manufacturing system.

[0080] 2) Preparation of Haversian-like shape memory alloy bone scaffolds by 4D printing

[0081] The NiTi alloy substrate was preheated to 190°C, and the NiTi shape memory alloy powder with a particle size of 15 to 53 μm was placed in the powder cabin, and the oxygen content of the 4D printing cabin was controlled to 100 ppm. The process parameters of the inner layer of cancellous bone-like porous structure were as follows: laser power of 200 W, scanning speed of 2200 mm / s, spot diameter of 75 μm, scanning spacing of 60 μm, layer thickness of 30 μm, and the printing strategy was to rotate the laser path 65° every other layer. The process parameters of the outer layer of cortical bone-like porous structure with Haversian system were as follows: laser power of 220 W, scanning speed of 2000 mm / s, spot diameter of 75 μm, scanning spacing of 60 μm, layer thickness of 30 μm, and the printing strategy was to rotate the laser path 65° every other layer.

[0082] Example 5

[0083] A 4D printing preparation method for a shape memory alloy bone scaffold imitating a Haversian system comprises the following steps:

[0084] Step 1: Design of shape memory alloy bone scaffold imitating Haversian system

[0085] Inner layer: porous structure imitating cancellous bone, the unit type is a body-centered cubic structure based on struts, the unit size is 0.9mm, the rod diameter is 200μm, the pore size is 500μm, and the porosity is 85%;

[0086] Outer layer: A porous structure imitating cortical bone with a Haversian system. The unit type is a Diamond three-periodic minimal surface structure. The unit size is 1mm, the surface thickness is 100μm, the pore size is 120μm, and the porosity is 75%. In the outer layer, 36 concentrically arranged Haversian tubes with a diameter of 450μm are designed longitudinally, and 36 concentrically arranged Volkmann tubes with a diameter of 450μm are designed transversely.

[0087] Step 2: Preparation of shape memory alloy bone scaffolds imitating the Haversian system

[0088] 1) The STL files of the inner layer cancellous bone-simulating porous structure and the outer layer cortical bone-simulating porous structure with Haversian system are respectively imported into the slicing software for slicing processing, and the sliced ​​files are imported into the 4D printing additive manufacturing system.

[0089] 2) Preparation of Haversian-like shape memory alloy bone scaffolds by 4D printing

[0090] Preheat the NiTi alloy substrate to 190°C, place NiTi shape memory alloy powder with a particle size of 15 to 53μm in the powder chamber, and control the oxygen content in the 4D printing chamber to 100ppm. The process parameters of the inner layer of cancellous bone-imitation porous structure are as follows: laser power of 130W, scanning speed of 1400mm / s, spot diameter of 75μm, scanning spacing of 60μm, layer thickness of 30μm, and the printing strategy is to rotate the laser path 65° every other layer. The process parameters of the outer layer of cortical bone-imitation porous structure with Haversian system are as follows: laser power of 160W, scanning speed of 1200mm / s, spot diameter of 75μm, scanning spacing of 60μm, layer thickness of 30μm, and the printing strategy is to rotate the laser path 65° every other layer. Figure 8 3D diagram of the shape memory alloy bone scaffold simulating the Haversian system in this embodiment.

[0091] Example 6

[0092] A 4D printing preparation method of a shape memory alloy bone scaffold imitating a Haversian system comprises the following steps:

[0093] Step 1: Design of shape memory alloy bone scaffold imitating Haversian system

[0094] Inner layer: porous structure imitating cancellous bone, the unit type is a body-centered cubic structure based on struts, the unit size is 0.9mm, the rod diameter is 200μm, the pore size is 500μm, and the porosity is 85%;

[0095] Outer layer: A porous structure imitating cortical bone with a Haversian system. The unit type is a Diamond three-periodic minimal surface structure. The unit size is 1mm, the surface thickness is 100μm, the pore size is 120μm, and the porosity is 75%. In the outer layer, 36 concentrically arranged Haversian tubes with a diameter of 80μm are designed longitudinally, and 36 concentrically arranged Volkmann tubes with a diameter of 80μm are designed transversely.

[0096] Step 2: Preparation of shape memory alloy bone scaffolds imitating the Haversian system

[0097] 1) The STL files of the inner layer cancellous bone-simulating porous structure and the outer layer cortical bone-simulating porous structure with Haversian system are respectively imported into the slicing software for slicing processing, and the sliced ​​files are imported into the 4D printing additive manufacturing system.

[0098] 2) Preparation of Haversian-like shape memory alloy bone scaffolds by 4D printing

[0099] The NiTi alloy substrate was preheated to 190°C, and the NiTi shape memory alloy powder with a particle size of 15 to 53 μm was placed in the powder cabin, and the oxygen content of the 4D printing cabin was controlled to 100 ppm. The process parameters of the inner layer of cancellous bone-like porous structure were as follows: laser power of 130 W, scanning speed of 1400 mm / s, spot diameter of 75 μm, scanning spacing of 60 μm, layer thickness of 30 μm, and the printing strategy was to rotate the laser path 65° every other layer. The process parameters of the outer layer of cortical bone-like porous structure with Haversian system were as follows: laser power of 160 W, scanning speed of 1200 mm / s, spot diameter of 75 μm, scanning spacing of 60 μm, layer thickness of 30 μm, and the printing strategy was to rotate the laser path 65° every other layer.

[0100] Example 7

[0101] A 4D printing preparation method of a shape memory alloy bone scaffold imitating a Haversian system comprises the following steps:

[0102] Step 1: Design of shape memory alloy bone scaffold imitating Haversian system

[0103] Inner layer: porous structure imitating cancellous bone, the unit type is a body-centered cubic structure based on struts, the unit size is 0.9mm, the rod diameter is 200μm, the pore size is 500μm, and the porosity is 85%;

[0104] Outer layer: A porous structure imitating cortical bone with a Haversian system. The unit type is a Diamond three-periodic minimal surface structure. The unit size is 1mm, the surface thickness is 100μm, the pore size is 120μm, and the porosity is 75%. In the outer layer, 12 concentrically arranged Haversian tubes with a diameter of 80μm are designed longitudinally, and 12 concentrically arranged Volkmann tubes with a diameter of 80μm are designed transversely.

[0105] Step 2: Preparation of shape memory alloy bone scaffolds imitating the Haversian system

[0106] 1) The STL files of the inner layer cancellous bone-simulating porous structure and the outer layer cortical bone-simulating porous structure with Haversian system are respectively imported into the slicing software for slicing processing, and the sliced ​​files are imported into the 4D printing additive manufacturing system.

[0107] 2) 4D process for preparing Haversian-like shape memory alloy bone scaffolds

[0108] The NiTi alloy substrate was preheated to 190°C, and the NiTi shape memory alloy powder with a particle size of 15 to 53 μm was placed in the powder cabin, and the oxygen content of the 4D printing cabin was controlled to 100 ppm. The process parameters of the inner layer of cancellous bone-like porous structure were as follows: laser power of 130 W, scanning speed of 1400 mm / s, spot diameter of 75 μm, scanning spacing of 60 μm, layer thickness of 30 μm, and the printing strategy was to rotate the laser path 65° every other layer. The process parameters of the outer layer of cortical bone-like porous structure with Haversian system were as follows: laser power of 160 W, scanning speed of 1200 mm / s, spot diameter of 75 μm, scanning spacing of 60 μm, layer thickness of 30 μm, and the printing strategy was to rotate the laser path 65° every other layer.

[0109] Comparative Example 1

[0110] A 4D printing preparation method of a shape memory alloy bone scaffold imitating a Haversian system comprises the following steps:

[0111] Step 1: Design of shape memory alloy bone scaffolds imitating Haversian system

[0112] Inner layer: porous structure imitating cancellous bone, the unit type is an octahedral structure based on struts, the unit size is 0.6mm, the rod diameter is 140μm, the pore size is 450μm, and the porosity is 50%;

[0113] Outer layer: A porous structure imitating cortical bone with a Haversian system. The unit type is a Gyroid three-periodic minimal surface structure. The unit size is 0.6mm, the surface thickness is 225μm, the pore size is 600μm, and the porosity is 25%. In the outer layer, 36 concentrically arranged Haversian tubes with a diameter of 450μm are designed longitudinally, and 36 concentrically arranged Volkmann tubes with a diameter of 450μm are designed transversely.

[0114] Step 2: Preparation of shape memory alloy bone scaffolds imitating the Haversian system

[0115] 1) The STL files of the inner layer cancellous bone-simulating porous structure and the outer layer cortical bone-simulating porous structure with Haversian system are respectively imported into the slicing software for slicing processing, and the sliced ​​files are imported into the 4D printing additive manufacturing system.

[0116] 2) 4D process for preparing Haversian-like shape memory alloy bone scaffolds

[0117] The NiTi alloy substrate was preheated to 160°C, and NiTi shape memory alloy powder with a particle size of 15 to 53 μm was placed in the powder cabin. The oxygen content of the 4D printing cabin was controlled to 100 ppm. The process parameters of the inner layer of cancellous bone-like porous structure were as follows: laser power of 90 W, scanning speed of 400 mm / s, spot diameter of 75 μm, scanning spacing of 60 μm, layer thickness of 30 μm, and the printing strategy was to rotate the laser path 65° every other layer. The process parameters of the outer layer of cortical bone-like porous structure with Haversian system were as follows: laser power of 70 W, scanning speed of 1500 mm / s, spot diameter of 75 μm, scanning spacing of 60 μm, layer thickness of 30 μm, and the printing strategy was to rotate the laser path 65° every other layer.

[0118] In Comparative Example 1, the three-period minimal surface sample for imitating the porous structure of cortical bone cannot be formed due to the combined influence of the substrate preheating temperature and the laser power and scanning speed process parameters (low power and high scanning speed). Fig.10 .

[0119] Comparative Example 2

[0120] A 4D printing preparation method for a shape memory alloy bone scaffold imitating a Haversian system comprises the following steps:

[0121] Step 1: Design of shape memory alloy bone scaffolds imitating Haversian system

[0122] Inner layer: porous structure imitating cancellous bone, the unit type is an octahedral structure based on struts, the unit size is 0.6mm, the rod diameter is 140μm, the pore size is 450μm, and the porosity is 50%;

[0123] Outer layer: A porous structure imitating cortical bone with a Haversian system. The unit type is a Gyroid three-periodic minimal surface structure. The unit size is 0.6mm, the surface thickness is 225μm, the pore size is 600μm, and the porosity is 25%. In the outer layer, 36 concentrically arranged Haversian tubes with a diameter of 450μm are designed longitudinally, and 36 concentrically arranged Volkmann tubes with a diameter of 450μm are designed transversely.

[0124] Step 2: Preparation of shape memory alloy bone scaffolds imitating the Haversian system

[0125] 1) The STL files of the inner layer cancellous bone-simulating porous structure and the outer layer cortical bone-simulating porous structure with Haversian system are respectively imported into the slicing software for slicing processing, and the sliced ​​files are imported into the 4D printing additive manufacturing system.

[0126] 2) Preparation of Haversian-like shape memory alloy bone scaffolds by 4D printing

[0127] The NiTi alloy substrate was preheated to 190°C, and the NiTi shape memory alloy powder with a particle size of 15 to 53 μm was placed in the powder cabin, and the oxygen content of the 4D printing cabin was controlled to 100 ppm. The process parameters of the inner layer of cancellous bone-like porous structure were as follows: laser power of 230 W, scanning speed of 2300 mm / s, spot diameter of 75 μm, scanning spacing of 60 μm, layer thickness of 30 μm, and the printing strategy was to rotate the laser path 65° every other layer. The process parameters of the outer layer of cortical bone-like porous structure with Haversian system were as follows: laser power of 80 W, scanning speed of 600 mm / s, spot diameter of 75 μm, scanning spacing of 60 μm, layer thickness of 30 μm, and the printing strategy was to rotate the laser path 65° every other layer.

[0128] In Comparative Example 2, due to the influence of laser power and scanning speed process parameters (high power and high scanning speed), defects were generated inside the octahedral porous structure sample used to simulate the porous structure of cancellous bone. During the compression test, the porous structure failed locally and had poor mechanical properties. Fig.11 .

[0129] By comparing Examples 1 to 7 and Comparative Examples 1 to 2, it can be seen that the shape memory alloy bone scaffold of the Haversian system prepared by the present invention using medium laser power and medium scanning speed has good preparability and good biocompatibility, can meet the growth function of osteoblasts, blood vessels, and nerves, and also has good mechanical properties, can overcome the stress shielding effect, and is beneficial to the patient's recovery.

[0130] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A 4D printing preparation method for a shape memory alloy bone scaffold imitating the Haversian system, characterized in that: The following steps are included: Step 1: 3D modeling and design of shape memory alloy bone scaffold imitating Haversian system Design an inner layer of cancellous bone-like porous structure and an outer layer of cortical bone-like porous structure with Haversian system, and use 3D modeling software to perform Boolean sum operation to make the cross-sections of the inner layer of cancellous bone-like porous structure and the outer layer of cortical bone-like porous structure with Haversian system radially fused to form a complete Haversian-like shape memory alloy bone scaffold; Step 2: 3D model slicing The STL files of the inner layer simulated cancellous bone porous structure and the outer layer simulated cortical bone porous structure with Haversian system are respectively imported into the slicing software for slicing processing, and the sliced ​​files are imported into the 4D printing additive manufacturing system; Step 3: 4D printing process to prepare shape memory alloy bone scaffolds imitating Haversian system First, a NiTi alloy substrate is preheated, and shape memory alloy powder is placed in a powder chamber. Then, the oxygen content in the forming chamber is adjusted, and forming process parameters are given to an inner layer of a cancellous bone-imitation porous structure and an outer layer of a cortical bone-imitation porous structure with a Haversian system, respectively. After forming, a shape memory alloy bone scaffold imitating a Haversian system is obtained; different laser powers and scanning speeds are given to the inner layer of a cancellous bone-imitation porous structure and the outer layer of a cortical bone-imitation porous structure with a Haversian system according to the rod diameter and the curved surface thickness.

2. The 4D printing preparation method of the shape memory alloy bone scaffold simulating the Haversian system according to claim 1, characterized in that: The inner layer of cancellous bone-mimicking porous structure in step one is a porous unit based on struts, and the porous unit based on struts is one of octahedron, cube, body-centered cube, face-centered cube, dodecahedron or diamond, and its unit size is 0.6-1.8 mm, its rod diameter is 140-500 μm, its pore diameter is 80-1200 μm, and its porosity is 50-90%.

3. The 4D printing preparation method of the shape memory alloy bone scaffold simulating the Haversian system according to claim 1, characterized in that: The outer layer of the simulated cortical bone porous structure with the Haversian system in step 1 is a porous unit based on a three-periodic minimal surface. The porous unit based on the three-periodic minimal surface is one of Gyroid, Diamond, Neovius or Lidinoid, with a unit size of 0.6 to 1.8 mm, a surface thickness of 150 to 450 μm, a pore size of 80 to 1200 μm, and a porosity of 10% to 80%.

4. The 4D printing preparation method of the shape memory alloy bone scaffold simulating the Haversian system according to claim 1, characterized in that: In step 1, the outer layer of the simulated cortical bone porous structure with the Haversian system is designed to be a simulated Haversian tube arranged in concentric circles in the longitudinal direction, and is designed to be a simulated Volkmann tube arranged in concentric circles in the transverse direction.

5. The 4D printing preparation method of the shape memory alloy bone scaffold simulating the Haversian system according to claim 4, characterized in that: The diameter of the simulated Haversian tube is 80-500 μm, and the number is 12-36; the diameter of the simulated Volkmann tube is 80-500 μm, and the number is 12-36.

6. The 4D printing preparation method of the Haversian system-mimicking shape memory alloy bone scaffold according to claim 1, characterized in that: In step three, the preheating temperature of the NiTi alloy substrate is 190-210° C.; the shape memory alloy powder is one of NiTi, NiTiNb, NiTiCr, NiTiFe, and NiTiCu, and the particle size of the shape memory alloy powder is 15-53 μm; and the oxygen content in the forming chamber is controlled within 100 ppm.

7. The 4D printing preparation method of the Haversian system-simulating shape memory alloy bone scaffold according to claim 1, characterized in that: The laser power of the inner layer of the porous structure imitating cancellous bone in step 3 is 70-200W, and the scanning speed is 400-2000mm / s; the laser power of the outer layer of the porous structure imitating cortical bone with the Haversian system is 80-220W, and the scanning speed is 600-2200mm / s.

8. The 4D printing preparation method of the Haversian system-mimicking shape memory alloy bone scaffold according to claim 1, characterized in that: The forming process parameters of the inner layer cancellous bone-mimicking porous structure in step 3 are as follows: the spot diameter is 75-85 μm, the scanning interval is 60-100 μm, the layer thickness is 30-40 μm, and the printing strategy is to rotate the laser path by 65-75° every other layer; The outer layer has a Haversian system for forming a porous structure of simulated cortical bone. The process parameters are as follows: a spot diameter of 75 to 85 μm, a scanning interval of 60 to 100 μm, a layer thickness of 30 to 40 μm, and a printing strategy of rotating the laser path by 65 to 75° for every other layer.

9. A shape memory alloy bone scaffold imitating the Haversian system, characterized in that: Prepared according to the 4D printing preparation method according to any one of claims 1 to 8.

10. Use of the shape memory alloy bone scaffold simulating the Haversian system according to claim 9 in bone implants.

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