3D printing metamaterial piezoelectric type interbody fusion cage

Abstract

The invention discloses a 3D printing metamaterial piezoelectric type interbody fusion cage, and relates to the technical field of interbody fusion cages, the 3D printing metamaterial piezoelectric type interbody fusion cage comprises vertebra skeletons and a material piece, the material piece is arranged between the vertebra skeletons, a plurality of holes are formed in the surface of one side of the material piece at equal intervals, the holes are of a three-dimensional porous structure, the holes comprise Gyandroid, SchwarzP and Diamond structures, and the Gyandroid, SchwarzP and Diamond structures are arranged in the material piece. The Gyandroid structure, the SchwarzP structure and the Diamond structure are all extremely small curved surface structures; the device has a unique three-dimensional porous structure, so that stress is uniformly distributed in the material, material fatigue or damage caused by local stress concentration is avoided, the structural stability and reliability of the fusion cage in a long-term complex mechanical environment are ensured, a crystal structure in the piezoelectric material is deformed, and the fusion cage has a good mechanical property. The positive and negative charge centers are relatively displaced, so that a potential difference is generated at the two ends of the material, electric signals are formed, the electric signals can interact with surrounding bone tissue cells, and efficient function exertion in the spine repair and fusion process is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of intervertebral fusion devices, and in particular to a 3D printed metamaterial piezoelectric intervertebral fusion device. Background Art

[0002] Intervertebral fusion is one of the most widely used techniques in spinal surgery. Lumbar intervertebral fusion is mainly used to treat lumbar degenerative instability, lumbar spinal stenosis, lumbar spondylolisthesis, scoliosis and disc-related pain. The lumbar fusion cage uses the expansion force after the fusion cage is placed to stabilize the fusion cage, restore the height of the intervertebral disc, restore the physiological curvature and expand the vertebral area; From the perspective of mechanical properties, it is difficult to accurately design the internal microstructure of traditional materials to achieve ideal stress distribution. In the long-term complex mechanical environment of the human spine, stress concentration is prone to occur when stress is generated by frequent flexion, extension, torsion, and axial loading. This will not only cause material fatigue, wear, and even fracture, shorten the service life of the fusion device, but may also have adverse effects on surrounding bone tissue and nerves, affecting the surgical treatment effect and the patient's recovery process. In terms of the function of promoting bone fusion, traditional intervertebral fusion devices mostly rely on the biological inertness or limited biological activity of the material itself to guide bone tissue growth, and lack a mechanism to actively stimulate bone regeneration. The bone fusion process is relatively slow and the effect is unstable, often requiring a long period of postoperative recovery, increasing the patient's pain and medical costs. Therefore, a 3D printed metamaterial piezoelectric intervertebral fusion device is provided by a technician in this field to solve the problems raised in the above background technology. Summary of the invention

[0003] The purpose of the present invention is to provide a 3D printed metamaterial piezoelectric intervertebral fusion device to solve the problems raised in the above background technology.

[0004] To achieve the above object, the present invention provides the following technical solutions: A 3D printed metamaterial piezoelectric intervertebral fusion device, comprising a spinal frame and a material piece, wherein the material piece is arranged between the spinal frames, and a plurality of pores are evenly spaced on a surface of one side of the material piece; The pores present a three-dimensional porous structure, and the pores include Gyroid, Schwarz P and Diamond structures, and Gyroid, Schwarz P and Diamond structures are all minimal surface structures.

[0005] As a further solution of the present invention: a piezoelectric material is arranged inside the pores, and the material piece and the piezoelectric material are both made of a composite material matrix 3D printing filament containing polyvinylidene fluoride, polylactic acid and barium titanate.

[0006] As a further solution of the present invention: the piezoelectric material comprises the following components by mass fraction: 30%-60% of polyvinylidene fluoride, 20%-50% of polylactic acid, and 10%-30% of barium titanate.

[0007] As a further solution of the present invention: the porosity range of the pores is 30%-70%, and the pore diameter range of the pores is 0.1-1 mm.

[0008] As a further solution of the present invention: the expressions of the Gyroid, SchwarzP, and Diamond structures are as follows: In a three-dimensional Cartesian coordinate system; Gyroid is: sin(x)cos(y)+sin(y)cos(z)+sin(z)cos(x)=0; SchwarzP is: cosh(z)cos(y)+cosh(y)cos(z)+cosh(z)cos(x)-C=0, where c is a constant determined according to specific design; Diamond is: cos(x)sin(y)+cos(y)sin(z)+cos(z)sin(x)=0.

[0009] As a further solution of the present invention: the preparation steps of a 3D printed metamaterial piezoelectric intervertebral fusion device: S1: Dry the composite material raw materials containing polyvinylidene fluoride, polylactic acid, and barium titanate with the component ratios meeting the requirements to prepare 3D printing filaments with uniform diameter, smooth surface, and uniform internal component mixing. The diameter of the filaments is controlled between 1.5-2.5 mm to adapt to the subsequent 3D printing process. During the extrusion process, the temperatures of each zone of the screw are precisely regulated according to the melting points and processing characteristics of each component. For example, the melting section temperature of polyvinylidene fluoride is set at 160-180°C, the melting section temperature of polylactic acid is set at 150-170°C, and the dispersion section temperature of barium titanate is slightly higher than the melting points of the two to ensure that each component is fully melted and mixed and barium titanate is uniformly dispersed in the polymer matrix; S2: Use a 3D printing process parameter that is adapted to or optimized for the spinal skeleton to perform 3D printing of the material piece. During the printing process, the temperature of the printing nozzle is set between 170 - 200 °C according to the characteristics of the filament material, and the temperature of the printing platform is controlled at 40 - 60 °C to ensure good melting spreading and forming effect of the filament. The printing speed is set at 30 - 60 mm / s, the layer height is set at 0.1 - 0.3 mm, and the pores are formed in strict accordance with their respective mathematical expressions for the Gyroid, SchwarzP, and Diamond structures in a three-dimensional Cartesian coordinate system. The design model is converted into printing instructions through slicing software to precisely control the movement path of the nozzle and the material extrusion amount, realizing the precise construction of a complex three-dimensional porous structure; S3: Post-process the material piece after the piezoelectric material. Place it in a vacuum oven and perform annealing treatment at a temperature of 60 - 80 °C for 2 - 4 hours to enable the piezoelectric material to stably form in the pores, and at the same time promote the molecular chain diffusion and entanglement between the matrix of the material piece and the piezoelectric material to ensure its full combination with the matrix of the material piece. Then, the surface of the material piece can be polished, buffed, etc. as needed to improve its surface finish and biocompatibility; S4: Assemble the processed material piece with the spinal skeleton. Adopt a suitable connection method, such as designing mutually matching slot and protrusion structures at the connection part between the spinal skeleton and the material piece, and use a medical adhesive with good biocompatibility for bonding to ensure that the two are firmly connected and closely matched, forming a complete 3D printed metamaterial piezoelectric intervertebral fusion device.

[0010] Compared with the prior art, the beneficial effects of the present invention are: 1. In the physiological environment of the human spine, when a person performs various activities such as walking, bending, and turning, different degrees of mechanical stress will be generated on the implanted metamaterial piezoelectric intervertebral fusion device. Due to the unique three-dimensional porous structure of this material piece, the pores of the Gyroid, SchwarzP, and Diamond minimal surface structures therein can effectively disperse and transfer these stresses. This special pore structure enables the stress to be evenly distributed inside the material, avoiding material fatigue or damage caused by local stress concentration, thereby ensuring the structural stability and reliability of the fusion device in a long-term complex mechanical environment; 2. When the fusion device is under stress, the piezoelectric material made of polyvinylidene fluoride inside the pores will generate electrical signals due to the piezoelectric effect. The mechanical stress causes the crystal structure inside the piezoelectric material to deform, resulting in the relative displacement of the positive and negative charge centers, thereby generating a potential difference at both ends of the material and forming electrical signals. These electrical signals can interact with the surrounding bone tissue cells. On the one hand, the electrical signals can stimulate the activity of osteoblasts, promote the proliferation, differentiation of osteoblasts, and the synthesis and mineralization of the extracellular matrix, accelerating the formation and growth of new bone tissue and contributing to the fusion between vertebral bones. On the other hand, the electrical signals can also inhibit the function of osteoclasts, reduce bone resorption and destruction, and maintain the homeostasis of bone tissue, achieving efficient function during spinal repair and fusion; 3. According to the mathematical expressions of the Gyroid, SchwarzP, and Diamond structures, in a three-dimensional Cartesian coordinate system, for the Gyroid structure, sin(x)cos(y)+sin(y)cos(z)+sin(z)cos(x)=0, etc. During the 3D printing process, these expressions are used to generate models in 3D modeling software. Combining with the characteristics of the PVDF / HA / Mg composite matrix 3D printing wire, the printing parameters are adjusted to accurately manufacture a pore structure that meets the design requirements, ensuring its expected function in the intervertebral fusion device. Description of the Drawings

[0011] Figure 1 It is a schematic structural diagram of a 3D printed metamaterial piezoelectric intervertebral fusion device.

[0012] Figure 2 It is a schematic diagram of the cooperation between the material part and the spinal skeleton in a 3D printed metamaterial piezoelectric intervertebral fusion device.

[0013] Figure 3 It is a schematic structural diagram of the pores in the fusion mechanism of a 3D printed metamaterial piezoelectric intervertebral fusion device.

[0014] Figure 4 It is a schematic structural diagram of the piezoelectric material in a 3D printed metamaterial piezoelectric intervertebral fusion device.

[0015] Figure 5 It is a schematic diagram of the piezoelectric signal of the piezoelectric material in a 3D printed metamaterial piezoelectric intervertebral fusion device.

[0016] In the figure: 1, spinal skeleton; 2, material part; 3, pores; 4, piezoelectric material. Detailed Implementation Modes

[0017] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0018] Embodiment 1

[0019] Referring to Figures 1-5 , this embodiment provides a 3D printed metamaterial piezoelectric intervertebral fusion device, including a spinal skeleton 1 and a material member 2. The material member 2 is arranged between the spinal skeletons 1, and a plurality of pores 3 are evenly spaced on one surface of the material member 2; The pore 3 has a three-dimensional porous structure. The pore 3 includes Gyroid, Schwarz P, and Diamond structures, and the Gyroid, Schwarz P, and Diamond structures are all minimal surface structures; In this embodiment, specifically, a piezoelectric material 4 is arranged inside the pore 3. Both the material member 2 and the piezoelectric material 4 are prepared from a composite matrix 3D printing wire containing polyvinylidene fluoride, polylactic acid, and barium titanate; The piezoelectric material 4 contains the following components by mass fraction: Polyvinylidene fluoride 30%-60%, polylactic acid 20%-50%, barium titanate 10%-30%; The porosity range of the pore 3 is 30%-70%, and the pore diameter range of the pore 3 is 0.1-1 mm; In the physiological environment of the human spine, when a person performs various activities such as walking, bending, and turning, different degrees of mechanical stress will be generated on the implanted metamaterial piezoelectric intervertebral fusion device. Due to the unique three-dimensional porous structure of the material member 2, the Gyroid, Schwarz P, and Diamond minimal surface structure pores therein can effectively disperse and transfer these stresses. This special pore structure enables the stress to be evenly distributed inside the material, avoiding material fatigue or damage caused by local stress concentration, thereby ensuring the structural stability and reliability of the fusion device in a long-term complex mechanical environment; Meanwhile, when the fusion device is under stress, the piezoelectric material 4 made of polyvinylidene fluoride filled inside the pores 3 will generate electrical signals due to the piezoelectric effect. Mechanical stress causes the crystal structure inside the piezoelectric material to deform, resulting in the relative displacement of the positive and negative charge centers, thereby generating a potential difference at both ends of the material and forming electrical signals. These electrical signals can interact with the surrounding bone tissue cells. On the one hand, the electrical signals can stimulate the activity of osteoblasts, promote the proliferation, differentiation of osteoblasts, and the synthesis and mineralization of the extracellular matrix, accelerating the formation and growth of new bone tissue and contributing to the fusion between vertebral bones. On the other hand, the electrical signals can also inhibit the function of osteoclasts, reduce bone resorption and destruction, and maintain the homeostasis of bone tissue, achieving efficient functional performance during spinal repair and fusion.

[0020] Example 2

[0021] Referring to Figures 1-5 , this example is based on the previous example. The difference from the previous example is that the expressions of the Gyroid, Schwarz P, and Diamond structures are as follows: In a three-dimensional Cartesian coordinate system; Gyroid: sin(x)cos(y)+sin(y)cos(z)+sin(z)cos(x)=0; SchwarzP: cosh(z)cos(y)+cosh(y)cos(z)+cosh(z)cos(x)-C=0, where c is a constant determined according to specific design; Diamond: cos(x)sin(y)+cos(y)sin(z)+cos(z)sin(x)=0; Preparation steps of a 3D-printed metamaterial piezoelectric intervertebral fusion device: S1: Dry the composite material raw materials containing polyvinylidene fluoride, polylactic acid, and barium titanate with the component ratios meeting the requirements to prepare 3D printing filaments with uniform diameter, smooth surface, and uniform internal component mixing. The diameter of the filaments is controlled between 1.5 - 2.5 mm to adapt to the subsequent 3D printing process. During the extrusion process, the temperatures of each zone of the screw are precisely regulated according to the melting points and processing characteristics of each component. For example, the melting section temperature of polyvinylidene fluoride is set at 160 - 180 °C, the melting section temperature of polylactic acid is set at 150 - 170 °C, and the dispersion section temperature of barium titanate is slightly higher than the melting points of the two to ensure that each component is fully melted and mixed and barium titanate is uniformly dispersed in the polymer matrix; S2: Use the printing process parameters adapted to or optimized for the spinal skeleton 1 to perform 3D printing of the material part 2. During the printing process, the printing nozzle temperature is set between 170 - 200 °C according to the characteristics of the filament material, and the printing platform temperature is controlled at 40 - 60 °C to ensure good melting spreading and forming effect of the filament. The printing speed is set at 30 - 60 mm / s, and the layer height is set at 0.1 - 0.3 mm. The pores 3 need to be formed strictly according to their respective mathematical expressions of Gyroid, SchwarzP, and Diamond structures in the three-dimensional Cartesian coordinate system. The design model is converted into printing instructions through slicing software to precisely control the movement path of the nozzle and the material extrusion amount, realizing the precise construction of a complex three-dimensional porous structure; S3: Post-process the material part 2 filled with the piezoelectric material 4. Place it in a vacuum oven and perform annealing treatment at a temperature of 60 - 80 °C for 2 - 4 hours to enable the piezoelectric material 4 to be stably formed in the pores 3. At the same time, promote the molecular chain diffusion and entanglement between the matrix of the material part 2 and the piezoelectric material 4 to ensure its full combination with the matrix of the material part 2. Then, the surface of the material part can be polished, buffed, etc. as needed to improve its surface smoothness and biocompatibility; S4: Assemble the processed material part 2 with the spinal skeleton 1. Adopt a suitable connection method, such as designing mutually matching slot and protrusion structures at the connection part between the spinal skeleton 1 and the material part 2, and use a medical adhesive with good biocompatibility for bonding to ensure that the two are firmly connected and closely matched, forming a complete 3D printed metamaterial piezoelectric intervertebral fusion device; According to the mathematical expressions of Gyroid, SchwarzP, and Diamond structures, in the three-dimensional Cartesian coordinate system, such as sin(x)cos(y)+sin(y)cos(z)+sin(z)cos(x)=0 for the Gyroid structure, etc. During the 3D printing process, use these expressions to generate models in 3D modeling software, and combine with the characteristics of the PVDF / HA / Mg composite matrix 3D printing filament to adjust the printing parameters to accurately manufacture the pore structure that meets the design requirements, ensuring that it plays the expected function in the intervertebral fusion device.

[0022] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claimed rights.

[0023] In addition, it should be understood that although this specification is described in terms of embodiments, not every embodiment contains only an independent technical solution. This narrative manner of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A 3D printed metamaterial piezoelectric intervertebral fusion cage, characterized in that: It comprises a spinal frame (1) and a material piece (2), wherein the material piece (2) is arranged between the spinal frames (1), and a plurality of pores (3) are evenly spaced on a surface of one side of the material piece (2); The pores (3) present a three-dimensional porous structure, and the pores (3) include Gyroid, SchwarzP and Diamond structures, and the Gyroid, SchwarzP and Diamond structures are all minimal surface structures.

2. The 3D printed metamaterial piezoelectric intervertebral fusion cage according to claim 1, characterized in that: A piezoelectric material (4) is arranged inside the pore (3); the material piece (2) and the piezoelectric material (4) are both prepared from a composite material matrix 3D printing filament comprising polyvinylidene fluoride, polylactic acid and barium titanate.

3. The 3D printed metamaterial piezoelectric intervertebral fusion cage according to claim 2, characterized in that: The piezoelectric material (4) comprises the following components in terms of mass fraction: Polyvinylidene fluoride 30%-60%, polylactic acid 20%-50%, barium titanate 10%-30%.

4. The 3D printed metamaterial piezoelectric intervertebral fusion cage according to claim 3, characterized in that: The porosity of the pores (3) ranges from 30% to 70%, and the pore diameter of the pores (3) ranges from 0.1 to 1 mm.

5. The 3D printed metamaterial piezoelectric intervertebral fusion cage according to claim 1, characterized in that: The expressions of the Gyroid, SchwarzP and Diamond structures are as follows: In three-dimensional Cartesian coordinate system; Gyroid is: sin(x)cos(y)+sin(y)cos(z)+sin(z)cos(x)=0; SchwarzP is: cosh(z)cos(y)+cosh(y)cos(z)+cosh(z)cos(x)-C=0, where c is a constant determined according to the specific design; Diamond is: cos(x)sin(y)+cos(y)sin(z)+cos(z)sin(x)=0.

6. A preparation process for a 3D printed metamaterial piezoelectric intervertebral fusion device as claimed in any one of claims 1 to 5, characterized in that: S1: Drying a composite material raw material containing polyvinylidene fluoride, polylactic acid and barium titanate with the required proportions of each component to prepare a 3D printing filament with uniform diameter, smooth surface and uniform internal component mixing. The diameter of the filament is controlled between 1.5-2.5 mm to adapt to the subsequent 3D printing process. During the extrusion process, the temperature setting of each zone of the screw is precisely controlled according to the melting point and processing characteristics of each component. For example, the temperature of the melting section of polyvinylidene fluoride is set at 160-180°C, the temperature of the melting section of polylactic acid is set at 150-170°C, and the temperature of the dispersing section of barium titanate is slightly higher than the melting points of the two, to ensure that each component is fully melted and mixed and the barium titanate is evenly dispersed in the polymer matrix; S2: Use printing process parameters that are compatible with or optimized for the spine (1) to perform 3D printing of the material part (2). During the printing process, the temperature of the print head is set between 170-200°C according to the material properties of the filament, and the temperature of the printing platform is controlled at 40-60°C to ensure good melting, spreading and molding effects of the filament. The printing speed is set at 30-60mm / s, and the layer height is set at 0.1-0.3mm. The pores (3) must be molded in a three-dimensional Cartesian coordinate system in strict accordance with their respective mathematical expressions according to their Gyroid, SchwarzP and Diamond structures. The design model is converted into printing instructions through slicing software, and the nozzle movement path and material extrusion amount are accurately controlled to achieve accurate construction of complex three-dimensional porous structures; S3: Post-processing the material piece (2) after the piezoelectric material (4) is placed in a vacuum oven and annealed at 60-80°C for 2-4 hours to stably shape the piezoelectric material (4) in the pores (3) and promote the diffusion and entanglement of the molecular chains between the matrix of the material piece (2) and the piezoelectric material (4) to ensure that it is fully combined with the matrix of the material piece (2). Afterwards, the surface of the material piece can be ground, polished, etc. as needed to improve its surface finish and biocompatibility; S4: Assemble the processed material piece (2) and the spinal frame (1) using a suitable connection method, such as designing mutually matching slots and protrusion structures at the connection parts between the spinal frame (1) and the material piece (2), and use a medical adhesive with good biocompatibility for bonding, to ensure that the two are firmly connected and tightly matched, so as to form a complete 3D printed metamaterial piezoelectric intervertebral fusion device.

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