CN112190368B - Implant structure with mixed curved surface structural unit and preparation method - Google Patents

Implant structure with mixed curved surface structural unit and preparation method Download PDF

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CN112190368B
CN112190368B CN202010968983.3A CN202010968983A CN112190368B CN 112190368 B CN112190368 B CN 112190368B CN 202010968983 A CN202010968983 A CN 202010968983A CN 112190368 B CN112190368 B CN 112190368B
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curved surface
implant
function
support structure
unit
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CN112190368A (en
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路新
徐伟
于爱华
侯辰锦
刘博文
张策
张嘉振
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University of Science and Technology Beijing USTB
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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02—Prostheses implantable into the body
    • A61F2/28—Bones
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/10—Sintering only
    • B22F3/11—Making porous workpieces or articles
    • B22F3/1103—Making porous workpieces or articles with particular physical characteristics
    • B22F3/1109—Inhomogenous pore distribution
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y10/00—Processes of additive manufacturing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y80/00—Products made by additive manufacturing
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02—Prostheses implantable into the body
    • A61F2/30—Joints
    • A61F2002/30001—Additional features of subject-matter classified in A61F2/28, A61F2/30 and subgroups thereof
    • A61F2002/30108—Shapes
    • A61F2002/30199—Three-dimensional shapes
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02—Prostheses implantable into the body
    • A61F2/30—Joints
    • A61F2/3094—Designing or manufacturing processes
    • A61F2002/30985—Designing or manufacturing processes using three dimensional printing [3DP]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/25—Process efficiency

Abstract

The invention provides an implant structure with mixed curved surface structural units and a preparation method thereof, wherein the implant structure comprises a plurality of first curved surface structural units and a plurality of second curved surface structural units, the plurality of first curved surface structural units form a first bracket structure in an array mode, the plurality of second curved surface structural units form a second bracket structure in an array mode, and the first bracket structure and the second bracket structure are in transition connection through an S-shaped function to form the implant structure; the first curved surface structure unit and the second curved surface structure unit are respectively controlled by implicit function expressions, the structures of the first curved surface structure unit and the second curved surface structure unit are different, and the porosity of the first support structure is larger than that of the second support structure. The implant structure has good mechanical property and biological property, and the two curved surface structure units can be accurately controlled through a mathematical function, so that the accuracy of design and forming is realized.

Description

Implant structure with mixed curved surface structural unit and preparation method
Technical Field
The invention relates to the technical field of biomedical implant materials, in particular to an implant structure with a mixed curved surface structure unit and a preparation method thereof.
Background
In the clinic, one of the important methods for repairing large bone defects is artificial prosthesis replacement surgery. The porous structure is widely applied, however, the existing implant structure is mostly a traditional single rod-shaped structural unit, and the structure and the performance of the natural bone tissue of a human have gradient distribution along with the difference of the space position, so that the scaffold can not be matched in the aspects of mechanical property and biocompatibility. On one hand, the rod-based dot matrix structure is easy to generate local stress concentration due to the existence of obvious nodes, so that the load cannot be efficiently transferred, and the failure is easy to occur under the action of cyclic stress; on the other hand, the specific surface area of the rod-based lattice is low, which is disadvantageous for the attachment and proliferation of cells on the scaffold. On the whole, the current single lattice structure can not meet the requirements of mechanical property and biological appearance property at the same time.
In addition, the conventional powder sintering and casting methods have complicated processes, long production periods and low preparation accuracy when preparing the implant structure, and thus it is difficult to obtain an implant structure having ideal properties.
Therefore, obtaining an implant structure with a hybrid curved surface structure is a problem to be solved in bone replacement.
Disclosure of Invention
The main object of the present invention is to provide an implant structure with mixed curved surface structure unit and a preparation method thereof, the implant structure is formed by combining two bracket structures formed by two curved surface structure unit arrays with different structures, has good mechanical property and biological property, gives full play to the respective advantages of the two curved surface structures, namely, one of the curved surface structural units has high strength and can simulate relatively compact bone to provide sufficient mechanical support, the other curved surface structural unit has high permeability and can simulate relatively loose cancellous bone to promote in-vivo material transportation, and the two curved surface structure units can be accurately controlled through mathematical functions to realize the accuracy of design and forming, the technical problems that the implant structure in the prior art is single in structural unit and has large performance difference with human bone tissue are solved.
To achieve the above object, according to a first aspect of the present invention, there is provided an implant structure having a hybrid curve structural unit.
The implant structure with the mixed curved surface structure units comprises a plurality of first curved surface structure units and a plurality of second curved surface structure units, wherein the plurality of first curved surface structure units form a first support structure in an array mode, the plurality of second curved surface structure units form a second support structure in an array mode, and the first support structure and the second support structure are in transition connection through an S-shaped function to form the implant structure;
the first curved surface structure unit and the second curved surface structure unit are respectively controlled by implicit function expressions, the structures of the first curved surface structure unit and the second curved surface structure unit are different, and the porosity of the first support structure is larger than that of the second support structure.
Further, the first curved surface structure unit is a Diamond curved surface structure, and the implicit function expression of the Diamond curved surface structure is as follows:
Figure GDA0002790128990000021
wherein a, b and c are the lengths of the structural units in the directions of x, y and z; t is t1Is a constant that controls the porosity of the structural unit.
Further, the second curved surface structure unit is an I-WP curved surface structure, and the implicit function expression of the I-WP curved surface structure is as follows:
Figure GDA0002790128990000022
Figure GDA0002790128990000023
wherein a, b and c are the lengths of the structural units in the directions of x, y and z; t is t2Is a constant that controls the porosity of the structural unit.
Further, the lengths a, b and c of the Diamond curved surface structure and the I-WP curved surface structure in the x direction, the y direction and the z direction are all 0.5-2 mm; the constant t1Is 0.0833 to 0.75, the constant t20.3846-3.4615.
Based on the difference of the porosity of different parts, for example, the porosity of compact bone is 10% -20%, the porosity of spongy bone is 50% -90%, so the gradient porosity is 10-90%, and considering the target porosity is 10% -90%, the aperture is 200-1000 μm, and the forming precision of the selective laser melting technology, namely the layer thickness is more than or equal to 200 μm, the size of the structural unit is 0.5-2 mm.
The porosity is in the range of 10-90%, so the constant t1The value range is 0.0833-0.75, and the constant t2The value range is 0.3846-3.4615.
Further, the first support structure is a columnar porous structure formed by arraying the plurality of first curved surface structure units along three dimensions of length, width and height, and the second support structure is a hollow columnar porous structure formed by arraying the plurality of second curved surface structure units along three dimensions of length, width and height; the first support structure is arranged in the hollow middle of the second support structure.
Further, the first support structure is a cylindrical porous structure, and the second support structure is a hollow cylindrical porous structure.
Further, the expression of the sigmoid function is as follows:
Figure GDA0002790128990000031
wherein k is a constant for controlling the width of a transition region between the first support structure and the second support structure, and the value of k is 0.5-3; the function G (x, y, z) determines the morphology of the transition region, and the coordinate corresponding to the function G (x, y, z) being 0 is the center of the transition region.
The k value controls the width of a transition region between the first support structure and the second support structure, the larger the k value is, the narrower the transition region is, the function G (x, y, z) determines the morphology of the transition region, and the coordinate corresponding to the function G (x, y, z) ═ 0 is the center of the transition region, that is, the proportion of the first support structure and the second support structure in the transition region is 50% of the positions corresponding to the first support structure and 50% of the second support structure, which is specifically selected according to the actual situation.
Further, the expression of the implant structure is:
Figure GDA0002790128990000032
further, the cylindrical implant structure has the following expression:
Figure GDA0002790128990000033
(ii) a Wherein the content of the first and second substances,
Figure GDA0002790128990000035
which is a function of the radius of the implant structure at different locations; r is0Is the radius of the cylindrical implant structure; z is the height of the implant structure out of position; h is the height of the cylindrical implant structure.
The first two inequalities in the expression respectively determine the volume enclosed by the two isosurface, so that the part between the two isosurface can be obtained after the intersection is taken, namely the shape of the required implant structure is determined; the latter two inequalities determine the boundaries of the implant structure.
In order to achieve the above object, according to a second aspect of the present invention, there is provided a method of manufacturing an implant structure having a hybrid curve structural unit.
The preparation method of the implant structure with the mixed curved surface structural unit comprises the following steps:
s1, constructing a structural expression: determining the structures of the first curved surface structural unit and the second curved surface structural unit and the expressions of the first support structure and the second support structure, and connecting the expressions of the first support structure and the second support structure through an S-shaped function to obtain an expression of the implant structure based on the mixed curved surface structural unit;
s2, constructing a gradient structure: performing visualization processing on the expression of the implant structure and the structural parameters thereof to obtain and derive a 3D model of the implant structure;
s3, carrying out layered slicing processing on the model of the implant structure, and inputting the obtained two-dimensional data information into metal printing equipment; the metal printing equipment comprises the following process parameters: the laser power is 150-200W, the scanning speed is 600-900 mm/s, the scanning distance is 0.1-0.14 mm, and the thickness of the powder spreading layer is 20-30 mu m;
and S4, preparing the implant structure by adopting a selective laser melting technology.
In the invention, the function G (x, y, z) determines the morphology of the transition region, and the specific mode is as follows: in the transition region, the ratio of the two structures at different locations is controlled.
For example: the ratio of the two structures at different positions when the transition region is centered at x-0 (i.e., the zero point of the G (x, y, z) function is x-0) and G (x, y, z) is a linear function is shown in fig. 10;
keeping the transition center constant, when G (x, y, z) is a cubic function, the ratio of the two structures at different positions is shown in FIG. 11;
it can be seen that different G (x, y, z) functions determine the ratio of the two structures in the transition region and thus determine different transition region morphologies.
Therefore, the G (x, y, z) function should meet the following requirements:
g (x, y, z) is continuous within a defined domain, which is the range of size coordinates of the scaffold;
g (x, y, z) has a zero point in the defined domain, i.e. the transition region is in the defined domain;
g (x, y, z) is monotonically increased or decreased within the defined domain, i.e. different scaffold structures are ensured on both sides of the centre of the transition zone.
The average curvature of each point of a three-period extremely-small curved surface (TPMS) on the curved surface is zero, the three-period extremely-small curved surface is periodically arranged in space, and single cells of the three-period extremely-small curved surface can be smoothly connected, so that stress concentration easily generated at the nodes in the traditional lattice structure can be avoided. In addition, TPMS has a high specific surface area, facilitating cell attachment, proliferation and differentiation. In addition, the porosity, unit cell type and unit cell size of the TPMS can be directly controlled and changed through a mathematical formula, so that the structural characteristics of the required implant structure can be accurately regulated and controlled.
Compared with the prior art, the invention has the following advantages:
1. the implant structure designed by the invention comprises two different unit structures, namely a first curved surface structure unit and a second curved surface structure unit, wherein the two structure units are respectively controlled by an implicit function formula, so that the implant structure can be flexibly controlled, different lattice structures can be obtained by changing related parameters, and the implant structure has different structures and performances at different spatial positions.
2. Compared with the traditional rod-based structural unit, the TPMS-based structural unit adopted by the invention is completely controlled by a mathematical function, so that smooth transition can be realized between two mixed lattices, the force transfer efficiency is greatly improved, and the mechanical property of the bracket is improved; the surface curvature characteristic similar to that of bone tissue and the large specific surface area are also favorable for material transportation, cell attachment and proliferation, and the biocompatibility of the scaffold is greatly improved.
3. The implant structure designed by the invention has the structural units with very similar surface curvatures to the bone tissue structure, and the two structural units have respective advantages, namely the I-WP curved surface structural unit has high strength and the Diamond curved surface structural unit has high permeability; therefore, the structural characteristics of 'dense outside and sparse inside' of human bones and the functional characteristics of providing supporting strength by the dense bone on the outer layer and improving the permeability of the spongy bone on the inner layer are simulated, and the two are combined to obtain a bracket structure similar to the structure and the function of human bone tissues; specifically, the I-WP curved surface structure is positioned on the outer layer of the implant structure to provide supporting strength, and the Diamond curved surface structure is positioned on the inner layer of the implant structure to improve the permeability of the stent, so that the prepared implant structure not only meets the requirements of high strength and low elastic modulus of the implant, but also shows good mechanical compatibility; but also is beneficial to the adhesion, proliferation and differentiation of cells, promotes the transportation of nutrient substances and the discharge of metabolic waste out of the body, and shows good biocompatibility.
4. The porosity of the implant structure designed by the invention is in gradient change inside and outside, and is smoothly connected at the transition part, so that local stress concentration is avoided.
5. Compared with the traditional manufacturing method, the manufacturing of the implant structure designed by the invention is simpler, the production period is short and the forming precision is high.
Drawings
Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:
FIG. 1 is a schematic structural diagram of an I-WP curved surface structure in an embodiment of the invention;
FIG. 2 is a schematic structural diagram of a Diamond curved surface structure according to an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of a first supporting structure according to an embodiment of the present invention;
FIG. 4 is a top view of a first support structure in an embodiment of the invention;
FIG. 5 is a schematic structural view of a second stent structure in an embodiment of the present invention;
FIG. 6 is a top view of a second mounting structure in an embodiment of the invention;
FIG. 7 is a schematic structural diagram of an implant structure according to an embodiment of the present invention;
FIG. 8 is a top view of an implant structure according to an embodiment of the present invention;
FIG. 9 is a front view of one half of the implant structure in the longitudinal direction in accordance with an embodiment of the present invention;
FIG. 10 is a scale of two structures at different positions when the transition region is centered at x-0 and G (x, y, z) is a linear function according to an embodiment of the present invention;
fig. 11 is a ratio graph of two structures at different positions when the transition region is centered at x-0 and G (x, y, z) is a cubic function according to an embodiment of the present invention.
In the figure:
1. a first support structure; 2. a second support structure; 3. the middle part is hollow; A. a transition region between the first and second stent structures; B. a low porosity region; C. a high porosity region; D. an interface between the first scaffold structure and the transition region; E. an interface between the transition region and the second scaffold structure.
Detailed Description
Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
The invention discloses an implant structure with mixed curved surface structural units, as shown in fig. 1-9, the implant structure with mixed curved surface structural units comprises a plurality of first curved surface structural units and a plurality of second curved surface structural units, the plurality of first curved surface structural units form a first bracket structure 1 in an array mode, the plurality of second curved surface structural units form a second bracket structure 2 in an array mode, and the first bracket structure 1 and the second bracket structure 2 are in transitional connection through an S-shaped function to form the implant structure; the first curved surface structural unit and the second curved surface structural unit are respectively controlled by implicit function expressions, the structures of the first curved surface structural unit and the second curved surface structural unit are different, and the porosity of the first support structure 1 is larger than that of the second support structure 2.
In the above embodiment, the implant structure is mainly formed by combining two stent structures, while the first stent structure is mainly formed by a plurality of first structural unit arrays, the second stent structure is mainly formed by a plurality of second structural unit arrays, and the first stent structure 1 and the second stent structure 2 are transitionally connected by an S-shaped function to form the implant structure; the porosity of the implant structure varies in a gradient. Specifically, the porosity of the scaffold structure in the outer layer of the implant structure is less than the porosity of the scaffold structure in the inner layer; furthermore, the first structural unit and the second structural unit are respectively controlled by implicit function expressions, the structures of the first structural unit and the second structural unit are different, a plurality of identical structural units are arrayed along three dimensions of length, width and height to form a support structure, and the structures of the structural units forming different support structures are different.
Because the porosity of the first support structure 1 is greater than that of the second support structure 2, the first support structure 1 has lower density and higher porosity, so that the elastic modulus of an implant can be effectively reduced, the stress shielding phenomenon is avoided, and the Diamond curved surface structure is favorable for improving the permeability of the support, promoting the body fluid transportation, being favorable for the proliferation and differentiation of cells and accelerating the tissue regeneration; accordingly, the second scaffold 2 has a higher density and a lower porosity than the first scaffold 1, and can provide the high strength required for bone tissue as a load-bearing structure.
The second support structure 2 with lower porosity and higher density is connected with the first support structure 1 with higher porosity and lower density in a smooth transition way by utilizing an S-shaped transition function to form a structure body with dense outside and sparse inside, which has the characteristics of the human skeleton, namely the compact bone with high strength and low porosity on the surface layer and the highly inosculated spongy bone with low strength and high porosity on the inner layer, so that the elastic modulus is reduced while the strength requirement of the implant as a bearing part is ensured, and the implant has good mechanical compatibility with natural bone; meanwhile, the implant has good biocompatibility and prolongs the service life of the implant.
As another embodiment of the present invention, the first supporting structure 1 is a columnar porous structure formed by using a plurality of first structural units arrayed along three dimensions of length, width and height, as shown in fig. 3 and 4; the second support structure 2 is a hollow cylindrical porous structure formed by arraying a plurality of second structural units along three dimensions of length, width and height, and as shown in fig. 5 and 6, the first support structure 1 is arranged in the hollow part 3 of the second support structure 2.
Further, the first scaffold 1 is a cylindrical porous structure.
Further, the second stent structure 2 is a hollow cylindrical porous structure, and the first stent structure is connected at the hollow center 3 of the second stent structure 2 by an S-shaped function.
As another embodiment of the present invention, the first curved surface structure unit is a Diamond curved surface structure, and the implicit function expression of the Diamond curved surface structure is as follows:
Figure GDA0002790128990000081
wherein a, b and c are structural units in the formula x,Length dimensions in the y and z directions; t is t1Is a constant for controlling the porosity of the structural unit, and the value of the constant is 0.0833-0.75; i.e. by adjusting the dimensions a, b, c and t of the building blocks1The Diamond curved surface structural units with different sizes and porosities can be obtained.
As another embodiment of the invention, the second curved surface structure unit is an I-WP curved surface structure, and the implicit function expression of the I-WP curved surface structure is as follows:
Figure GDA0002790128990000082
Figure GDA0002790128990000083
wherein a, b and c are length dimensions of the structural unit in x, y and z directions; t is t2Is a constant for controlling the porosity of the structural unit, and has a value of 0.3846-3.4615; i.e. by adjusting the dimensions a, b, c and t of the building blocks2Values, I-WP structural units of different sizes and porosities are available.
As another embodiment of the invention, the lengths a, b and c of the Diamond curved surface structure in the x, y and z directions are all in the range of 0.5-2 mm.
As another embodiment of the invention, the lengths a, b and c of the I-WP curved surface structure in the x direction, the y direction and the z direction are all in the range of 0.5-2 mm.
As another embodiment of the present invention, the first stent structure 1 and the second stent structure 2 are connected by a smooth transition of an S-type function, and the expression of the S-type function is:
Figure GDA0002790128990000084
wherein k is a constant controlling the width of the transition region between the first scaffold 1 and the second scaffold 2; the function G (x, y, z) determines the morphology of the transition region, and the coordinate corresponding to the function G (x, y, z) being 0 is the center of the transition region. The k value and the function G (x, y, z) are selected according to actual conditions, namely, a proper S-shaped function expression is selected according to actual needs.
As another embodiment of the present invention, the expression for the implant structure is:
Figure GDA0002790128990000091
as another embodiment of the present invention, the cylindrical implant structure is expressed by:
Figure GDA0002790128990000092
wherein the content of the first and second substances,
Figure GDA0002790128990000093
which is a function of the radius of the implant structure at different locations; r is0Radius of the cylindrical implant structure; z is the height of the implant at different locations; h is the height of the cylindrical implant structure. The values of the parameters can be selected according to actual conditions.
As shown in FIG. 9, the implant structure based on the I-WP curved surface structure unit and the Diamond curved surface structure unit has the outer low porosity region A formed by the second scaffold structure 2 with high relative density to provide sufficient strength, and the inner high porosity region B formed by the first scaffold structure 1 with low relative density to significantly reduce the elastic modulus of the implant and promote the transportation of body fluid and the proliferation and differentiation of cells, and the first scaffold structure 1 and the second scaffold structure 2 are smoothly connected into an integral scaffold structure through the transition region C controlled by the S-shaped function to avoid stress concentration.
The invention also discloses a preparation method of the implant structure, which specifically comprises the following steps:
s1, constructing a structural expression; according to the required structure and performance characteristics of the implant, the sizes and the porosities of the I-WP curved surface structure and the Diamond curved surface structure which need to be selected are determined, so that the expressions of the first stent structure and the second stent structure can be determined, a proper S-shaped function is selected, and the expressions of the first stent structure and the second stent structure are connected through the S-shaped transition function to obtain the expression of the implant structure.
S2, constructing a gradient structure: inputting the expression of the implant structure and the size and shape parameters thereof into MATHEMATICA software for visualization processing to obtain and export a 3D model of the implant structure; the expression of the implant structure, the size and the shape parameters of the implant structure are subjected to Boolean operation to obtain the expression of the cylindrical implant structure, and the expression specifically comprises the following steps:
Figure GDA0002790128990000101
s3, carrying out layered slicing processing on the model of the implant structure through rapid prototyping auxiliary software Materialise Magics, and inputting the obtained two-dimensional data information into metal printing equipment; the metal printing equipment has the following process parameters: the laser power is 150-200W, the scanning speed is 600-900 mm/s, the scanning distance is 0.1-0.14 mm, and the thickness of the powder spreading layer is 20-30 mu m.
And S4, preparing the implant structure by adopting a selective laser melting technology. In the step, Ti powder with the granularity range of 30-45 mu m is used as a raw material, and an implant structure is prepared through SLM equipment.
And S5, taking out the product of the implant structure prepared in the step, and performing sand blasting and ultrasonic treatment to obtain a finished product of the implant structure. Meanwhile, the compressive yield strength and the elastic modulus are obtained through a compression experiment and are compared with human bone tissues.
It should be noted that, after step S2 and before step S3, the present invention further performs mechanical property and permeability analysis on the constructed model of the implant structure, specifically:
and (3) mechanical analysis, namely performing simulation on the designed implant structure model through finite element analysis software ANSYS WORKBENCH to obtain the maximum equivalent stress of the implant structure model, and judging whether the implant structure model fails under the set working condition. The specific simulation conditions are set as follows: the Material parameters were set according to the Performance parameters of the 3D printed article, i.e., Density 4.64g/cm3Poisson's ratio of 0.33, the elastic modulus is 110Gpa, the lower surface of the cylinder is added with a fixed constraint condition, a fixing force of 50MPa is applied perpendicular to the upper surface, and because the force borne by the skeleton is generally 5 times of the gravity of the human body, the weight of an adult man is assumed to be 75Kg, and the stress is 50MPa according to P ═ F/S.
The simulation of the permeability of the implant structure is carried out by a Fluent module in ANSYS WORKBENCH software, and the simulation conditions are as follows: to simulate body fluids, ensuring that the fluid is in laminar flow, the inlet is a velocity inlet with a value of 0.001m/s, the fluid is incompressible fluid water with a density of 1000kg/m3The viscosity was 0.001 pas, the outlet was a pressure outlet, the value was set to 0Pa, and the wall conditions were set to non-slip walls; by formula of permeability
Figure GDA0002790128990000102
And calculating the pressure distribution cloud chart to obtain the permeability.
The technical scheme of the invention is further explained by combining specific examples.
Example 1:
an implant structure based on I-WP curved surface structure unit and Diamond curved surface structure unit, the implant structure is a columnar porous structure with the size of
Figure GDA00027901289900001110
The porosity is 50% -80% -50% along the radial direction, the porous material comprises a first support structure 1 of an inner layer and a second support structure 2 of an outer layer, and the first support structure 1 and the second support structure 2 are connected through an S-shaped transition function; wherein the expression of the S-shaped transition function is:
Figure GDA0002790128990000111
the porosity of the first support structure 1 is 80%, and an inner-layer high-porosity low-density area is formed; the first support structure 1 is formed by a plurality of Diamond surface structure unit arrays, and the corresponding implicit function expression is as follows:
Figure GDA0002790128990000112
the dimension of the structural unit of the Diamond curved surface is 2mm and is expressed by a implicit function
Figure GDA0002790128990000113
Figure GDA0002790128990000114
Control is carried out;
the porosity of the second scaffold 2 is 50%, forming an outer low porosity high density region; the second bracket structure 2 is formed by a plurality of I-WP curved surface structure unit arrays, and the corresponding implicit function expression is as follows:
Figure GDA0002790128990000115
the size of the I-WP curved surface structural unit is 2mm, and the structural unit is expressed by a implicit function:
Figure GDA0002790128990000116
Figure GDA0002790128990000117
Figure GDA0002790128990000118
control is carried out;
finally, obtaining a columnar porous structure with the diameter of 10mm and the height of 10mm through Boolean operation, wherein the corresponding expression is as follows:
Figure GDA0002790128990000119
the implant structural model obtained in example 1 was subjected to simulation of mechanical properties and permeability.
The method of making the implant structure of example 1 includes the steps of:
s1, constructing a structural expression; determining the sizes and the porosities of structural units of an I-WP curved surface structure and a Diamond curved surface structure which need to be selected according to the structural and performance characteristics needed by the implant, namely determining the expressions of the first stent structure 1 and the second stent structure 2, selecting a proper S-shaped function, and connecting the expressions of the first stent structure 1 and the second stent structure 2 through the S-shaped transition function to obtain the expression of the implant structure;
s2, constructing a gradient structure: inputting an expression of the implant structure and the size and shape parameters of the structure into MATHEMATICA software for visualization processing to obtain and export a 3D model of the implant structure;
s3, importing the 3D model drawn by MATHEMATICA software into rapid prototyping auxiliary software Materalises Magics for layering and slicing processing to obtain two-dimensional data information;
s4, generating a scanning path of the two-dimensional data information, inputting the obtained two-dimensional data into SLM equipment, and setting process parameters: the laser power is 180W, the scanning speed is 900mm/s, the scanning distance is 0.14mm, and the thickness of the powder layer is 30 mu m;
and S5, preparing the structure by using SLM equipment, taking out, and performing sand blasting and ultrasonic treatment. Meanwhile, the yield strength and the elastic modulus are obtained through a compression experiment and are compared with human bone tissues.
Embodiments 2 to 4 disclose an implant structure, and the implant structure is prepared by the same preparation method as in embodiment 1, but the difference is mainly in the size and porosity of the implant structure and each constituent scaffold structure, and the specific process parameters of the SLM equipment, and the relevant structure parameters of the implant structure and each process parameter in the preparation method in embodiments 1 to 4 are summarized as detailed in tables 1 to 4.
TABLE 1
Figure GDA0002790128990000121
Figure GDA0002790128990000131
TABLE 2
Figure GDA0002790128990000132
TABLE 3
Figure GDA0002790128990000133
Figure GDA0002790128990000141
TABLE 4
Figure GDA0002790128990000142
Figure GDA0002790128990000151
The properties of the implant structures prepared in examples 1-4 are summarized below and are detailed in Table 5.
TABLE 5
Figure GDA0002790128990000152
As can be seen from Table 5, under the stress action of 50MPa, the maximum equivalent stress of the implant structures prepared in the embodiments 1 to 4 of the invention is 160.75 to 503.3MPa, and the maximum equivalent stress is smaller than the yield strength of the material, namely 830MPa, so that the implant structures cannot fail under the stress condition; the compressive yield strength is 126.32-211.6 MPa, the strength of the compact bone is within the range of 10-220 MPa, and the strength of the compact bone is far higher than that of the cancellous bone (0.8-11.6 MPa); the elastic modulus is within the range of 5.68-7.15 GPa, is relatively close to the elastic modulus value (0.01-30 GPa) of human bone tissues, and has good mechanical compatibility.
Calculated from the permeability simulation, the permeability was 5.92 x 10-9～10.26*10-9m2Permeability to human bone tissue 0.467 x 10-9～14.8*10-9m2The approach shows that the implant structure prepared by the invention has good permeability, is beneficial to the adhesion, proliferation and differentiation of cells, and promotes the transportation of nutrient substances and the discharge of metabolic waste out of the body.
The implant structure prepared in the embodiments 1-3 of the invention has a porosity of 65%, which is greater than 50%, and within a porosity range of 50% -90% of cancellous bone, so that the implant structure can be used for repairing cancellous bone.
In addition, as can be seen from the comparison of the experimental results of example 1, example 2 and example 3, the yield strength of the prepared scaffold can be increased but the permeability thereof can be decreased by appropriately decreasing the size of the unit structure under the same porosity.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.

Claims (4)

1. A method of making an implant structure having mixed-curve structural elements, comprising the steps of:
s1, constructing a structural expression: determining structures of the first curved surface structural unit and the second curved surface structural unit and expressions of the first support structure (1) and the second support structure (2), and connecting the expressions of the first support structure (1) and the second support structure (2) through an S-shaped function to obtain an expression of the implant structure based on the mixed curved surface structural unit; wherein the content of the first and second substances,
the first support structure (1) is a columnar porous structure formed by a plurality of first curved surface structure units arrayed along three dimensions of length, width and height, and the second support structure (2) is a hollow columnar porous structure formed by a plurality of second curved surface structure units arrayed along three dimensions of length, width and height; the first support structure (1) is arranged in the hollow middle part of the second support structure (2), and the first support structure (1) and the second support structure (2) are in transition connection through an S-shaped function to form the implant structure; the porosity of the first scaffold structure (1) is greater than the porosity of the second scaffold structure (2);
the first curved surface structure unit and the second curved surface structure unit are respectively controlled by implicit function expressions, and the structures of the first curved surface structure unit and the second curved surface structure unit are different;
the first curved surface structure unit is a Diamond curved surface structure, and the implicit function expression of the Diamond curved surface structure is as follows:
Figure FDA0003504939890000011
Figure FDA0003504939890000012
wherein a, b and c are the lengths of the structural units in the directions of x, y and z, and the a, b and c are all 0.5-2 mm; t is t1Constant to control porosity of structural units, t10.0833 to 0.75;
the second curved surface structure unit is an I-WP curved surface structure, and the implicit function expression of the I-WP curved surface structure is as follows:
Figure FDA0003504939890000013
Figure FDA0003504939890000014
wherein a, b and c are the lengths of the structural units in the directions of x, y and z, and a, b and c are all 0.5-2 mm; t is t2Constant to control porosity of structural units, t20.3846-3.4615;
the expression of the sigmoid function is:
Figure FDA0003504939890000021
k is a constant for controlling the width of a transition region between the first support structure and the second support structure, and the value of k is 0.5-3; determining the morphology of the transition region by using a function G (x, y, z), wherein the coordinate corresponding to the function G (x, y, z) which is 0 is the center of the transition region;
s2, constructing a gradient structure: performing visualization processing on the expression of the implant structure and the structural parameters thereof to obtain and derive a 3D model of the implant structure;
s3, carrying out layered slicing processing on the model of the implant structure, and inputting the obtained two-dimensional data information into metal printing equipment; the metal printing equipment comprises the following process parameters: the laser power is 150-200W, the scanning speed is 600-900 mm/s, the scanning distance is 0.1-0.14 mm, and the thickness of the powder spreading layer is 20-30 mu m;
and S4, preparing the implant structure by adopting a selective laser melting technology.
2. The method for preparing an implant structure with mixed-curved surface structural units according to claim 1, wherein the first scaffold structure (1) is a cylindrical porous structure and the second scaffold structure (2) is a hollow cylindrical porous structure.
3. The method of claim 1, wherein the expression for the implant structure is:
Figure FDA0003504939890000022
4. the method of claim 3, wherein the cylindrical implant structure is expressed by the formula:
Figure FDA0003504939890000023
；
wherein the content of the first and second substances,
Figure FDA0003504939890000024
which is a function of the radius of the implant structure at different locations; r is0A radius of the implant structure that is cylindrical; z is the height of the implant structure at the non-location; h is the height of the cylindrical implant structure.
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