Design and preparation method of multi-scale functionally graded biomimetic skull patch

Abstract

The application discloses a design and preparation method of a multi-scale function gradient biomimetic skull patch, and belongs to the field of personalized orthopedic implants and additive manufacturing technology. The method is based on the three-layer structure characteristics of a natural skull, constructs a function gradient three-layer model, and establishes a radial-circumferential coupling biomimetic energy consumption network in combination with finite element analysis, constructs a micro-scale buffer penetration unit in a low stress area, and realizes the synergistic optimization of light weight, impact resistance and biological fusion. The inner layer of the designed skull patch adopts a smooth protective structure, the outer layer adopts a tissue fusion structure, and the middle layer adopts a biomimetic bearing structure, and the skull patch can be suitable for additive manufacturing of materials such as PEKK, PEEK and titanium alloy. The method has good mechanical properties, biological properties and engineering application value.

Description

Technical Field

[0001] This invention belongs to the field of personalized orthopedic implant design and additive manufacturing technology, specifically involving a design and preparation method for a multi-scale functional gradient biomimetic skull patch, and more particularly a lightweight biomimetic skull patch design method based on the biomechanical characteristics of the skull, topology optimization and functional gradient structure construction, which can be applied to the design and manufacturing of personalized skull implants made of materials such as polyether ketone ketone (PEKK), polyether ether ketone (PEEK), and titanium alloys. Background Technology

[0002] Skull defects are usually caused by traumatic brain injury, tumor resection, decompression surgery, or congenital malformations. Cranioplasty is an important means of restoring the integrity of the skull, protecting brain tissue, and improving the patient's appearance and neurological function.

[0003] Currently, commonly used skull patches in clinical practice mainly include titanium alloy patches, polymethyl methacrylate patches, and polyetheretherketone (PEEK) patches. Among them, although titanium alloys have high strength, they have problems such as excessively high elastic modulus, high thermal conductivity, and obvious imaging artifacts; PEEK materials have good biocompatibility and mechanical adaptability, but their lightweight design and ability to form complex structures are still limited.

[0004] In recent years, with the development of additive manufacturing technology, personalized skull patches based on 3D reconstruction have gradually become a research hotspot. Existing skull patches mostly employ honeycomb structures, Voronoi structures, or uniform porous structures to achieve weight reduction, but the following problems still exist: Most existing structures use a single uniform porous structure, lacking biomimetic simulation of the three-layer structure of the natural skull; there is a lack of load-bearing path design targeting the impact load characteristics of the skull, resulting in insufficient impact resistance; existing porous structures are usually uniformly distributed, easily causing local stress concentration and decreased mechanical properties; existing structures rarely consider the differentiated interface requirements such as dura mater protection and scalp tissue fusion; some complex structures are difficult to adapt to additive manufacturing processes such as FDM, exhibiting problems such as poor printing stability and significant warping deformation.

[0005] Therefore, there is an urgent need to propose a functional gradient biomimetic skull patch design and fabrication method that combines lightweight, impact resistance, biocompatibility, and additive manufacturing adaptability. Summary of the Invention

[0006] In view of the shortcomings of the existing situation, the purpose of this invention is to provide a design and preparation method for a multi-scale functional gradient biomimetic skull patch, so as to solve the problems of insufficient mechanical properties, single biological interface function, large structural weight and poor adaptability to additive manufacturing of existing skull patches.

[0007] This invention will be implemented with the following scheme: a method for designing and preparing a multi-scale functional gradient biomimetic skull patch, characterized by comprising the following steps: Step 1: Obtain medical imaging data of the patient's skull and establish a three-dimensional model of the skull defect area; Step 2: Based on the hierarchical structural characteristics of the natural skull inner table-cancellous bone-outer table, construct a three-layer functional gradient model; Step 3: Perform finite element static analysis and impact dynamic analysis on the middle layer region to obtain the stress transmission path inside the skull patch; Step 4: Construct a radial-circular coupled biomimetic energy dissipation network based on the stress transmission path; Step 5: Based on the finite element stress distribution results, perform local subtractive optimization on the middle layer structure and construct microscale buffer permeable units in the low stress region; Step 6: Design differentiated interfaces for the inner and outer layers of the skull patch, with the inner layer using a continuous smooth structure and the outer layer using an open structure; Step 7: The optimized skull patch is then formed using additive manufacturing.

[0008] Furthermore, the functional gradient three-layer model includes: an inner protective layer located on the brain tissue side, a biomimetic support layer located in the middle region, and an outer fusion layer located on the scalp tissue side.

[0009] Furthermore, the radial-circular coupled biomimetic energy dissipation network includes: a radial main bearing unit arranged along the impact diffusion direction, and a circumferential energy dissipation connection unit connected to the radial main bearing unit.

[0010] Furthermore, the low-stress region is determined using finite element stress contour plots.

[0011] Furthermore, the mid-layer structural nodes adopt a rounded corner transition design.

[0012] Furthermore, the microscale buffer permeation unit is one or more of a lattice structure, Voronoi structure, TPMS structure, or mesh structure.

[0013] Furthermore, the outer fusion layer is provided with through holes or semi-through holes to promote tissue attachment and nutrient exchange; the inner protective layer adopts a low-roughness continuous surface to reduce irritation to the dura mater.

[0014] Furthermore, the skull patch material used for additive manufacturing of the optimized skull patch includes one or more of PEKK, PEEK, PEK, PPSU, and titanium alloy.

[0015] This application has the following advantages over the prior art: 1. The embodiments of the present invention construct a functional gradient system based on the three-layer structure of the natural skull, thereby achieving synergistic optimization of biological and mechanical properties.

[0016] 2. The embodiments of the present invention construct a radial-circular coupled biomimetic energy dissipation network based on the finite element stress path, which can effectively improve the impact buffering capacity of the skull patch.

[0017] 3. The embodiments of the present invention achieve a balance between lightweighting and structural stability through the coupled design of local material reduction and microscale buffer permeation units.

[0018] 4. The embodiments of the present invention adopt a differentiated interface design, which can simultaneously meet the requirements of dura mater protection and scalp tissue fusion.

[0019] 5. The structure of the embodiments of the present invention is applicable to additive manufacturing processes such as FDM, and has good manufacturing stability and engineering application value. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the overall structure of the multi-scale functional gradient biomimetic skull patch of the present invention; Figure 2 This is a schematic diagram of the functionally graded three-layer structure of the present invention; Figure 3 This is a schematic diagram of the radial-circular coupled biomimetic energy dissipation network of the present invention; Figure 4 This is a schematic diagram of the partially porous structure in the middle layer of the present invention; Figure 5 This is a schematic diagram of the outer layer tissue fusion structure of the present invention; Figure 6 This is a schematic diagram of the smooth inner protective structure of the present invention; Figure 7 This is a schematic diagram of the local subtractive material optimization based on stress field of the present invention; Figure 8 This is a schematic diagram of the additive manufacturing process of the present invention. Detailed Implementation

[0022] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] In the description of this application, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0024] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation", "connection" and "joining" should be interpreted broadly, for example, they can refer to fixed connections, detachable connections, or integral connections; those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0025] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" can explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0026] Example 1 (Refer to) Figures 1 to 8 The present invention proposes a method for designing and fabricating a multi-scale functionally graded biomimetic skull patch, which specifically includes the following steps: Step 1: First, based on the obtained CT images of the patient's skull, import the DICOM format data into Mimics software. Use threshold segmentation to accurately extract and obtain a 3D model of the skull defect area, and export it as an STL file. Then, import the STL model into Geomagic Wrap software to smooth and repair the model surface, thereby establishing a continuous and closed curved surface model.

[0027] Step 2: Import the continuously closed surface model established above into SolidWorks software to create solid structure 100. Based on the hierarchical structure characteristics of the natural skull, namely "inner table - cancellous bone - outer table", solid structure 100 is constructed as a functionally graded three-layer model, including: outer fusion layer 10, middle biomimetic load-bearing layer 20, and inner protective layer 30.

[0028] Step 3: Import the model into HyperMesh software to generate a finite element mesh, and then import it into Abaqus software to perform static and impact dynamic analysis on the middle layer region. The static load is set to 50~150 N, the impact load is set to 400~600 N, and the boundary condition is set to edge fixed constraint, thereby obtaining the stress transmission path inside the skull patch. Preferably, in this embodiment, the static load is set to 100 N and the impact load is set to 500 N.

[0029] Step 4: Based on the stress transmission path described above, a radial main bearing unit 211 and a circumferential energy dissipation connection unit 212 connected to it are constructed in the middle biomimetic bearing layer 20 along the impact diffusion direction to form a radial-circumferential coupled biomimetic energy dissipation network 21.

[0030] Step 5: Based on the stress cloud distribution results obtained from the finite element analysis, determine the low-stress region of the middle layer. Perform local subtractive material optimization in this low-stress region and fill it with microscale buffer permeable units 23. Furthermore, to reduce stress concentration, a rounded corner transition design is adopted for the nodes of the middle layer structure, with a corner radius set to 0.2~1mm. Preferably, in this embodiment, the corner radius is 0.5mm.

[0031] Step 6: Design a differentiated interface between the outer fusion layer 10 and the inner protective layer 30 of the skull patch.

[0032] Step 7: The optimized skull patch is then additively manufactured. In this embodiment, PEKK material is selected, and FDM (Fused Deposition Modeling) technology is used for printing. Specific printing parameters include: nozzle temperature of 300~400℃, plateau temperature of 100~200℃, layer thickness of 0.1~0.3 mm, and printing speed of 10~50 mm / s. Preferably, in this embodiment, the nozzle temperature is 370℃, the plateau temperature is 160℃, the layer thickness is 0.2 mm, and the printing speed is 20 mm / s.

[0033] Example 2 (Refer to) Figure 1 and Figure 2 In this embodiment, the thickness of each structural layer is distributed in a gradient, specifically: the outer fusion layer 10 has a thickness of 0.2~1.0 mm, the middle biomimetic support layer 20 has a thickness of 1.5~4.0 mm, and the inner protective layer 30 has a thickness of 0.2~1.0 mm. Preferably, in this embodiment, the outer fusion layer 10 has a thickness of 0.5 mm, the middle biomimetic support layer 20 has a thickness of 2.5 mm, and the inner protective layer 30 has a thickness of 0.5 mm.

[0034] Reference Figure 1 and Figure 6The inner protective layer 30 is located on the side facing the dura mater / brain tissue 50. This inner protective layer has a continuous smooth structure, and its inner surface is a low-roughness surface 31. This structure can effectively reduce friction and irritation to the dura mater / brain tissue 50 after implantation, playing a role in preventing adhesion and providing smooth protection, thus ensuring the safety of the implant.

[0035] Reference Figure 2 and Figure 5 The outer fusion layer 10 is located on the side facing the scalp tissue 40. Semi-through opening structures 11 are evenly distributed on the outer fusion layer 10. These opening structures 11 not only achieve the lightweighting of the outer surface, but more importantly, they can promote the attachment of the scalp tissue 40, the ingrowth of blood vessels 41, and the exchange of nutrients between the inside and outside, thereby achieving excellent tissue fusion effect.

[0036] Reference Figure 2 and Figure 3 The middle biomimetic load-bearing layer 20 plays a core role in energy dissipation, load bearing, and impact resistance. It contains a radial-circumferential coupled biomimetic energy dissipation network 21. This network specifically includes radially distributed main load-bearing units 211 and spiral / curved circumferential energy dissipation connecting units 212. The radial main load-bearing units 211 are arranged along the radial force transmission path 214 to transmit the main external loads; the circumferential energy dissipation connecting units 212 connect the radial main load-bearing units along the circumferential energy dissipation path 213 to effectively disperse impact energy during impact.

[0037] Example 3 (Refer to) Figure 4 and Figure 7 To further achieve lightweighting, the middle biomimetic load-bearing layer 20 undergoes localized subtractive material optimization based on the stress field. A stress distribution cloud map is obtained through finite element analysis to accurately identify high-stress and low-stress regions. Material is retained along high-stress paths to form the truss load-bearing skeleton 22; while in the identified low-stress regions, localized subtraction is performed, and microscale buffer permeable units (i.e., locally porous filling regions) 23 are filled. In this embodiment, the microscale buffer permeable unit 23 can be one or more of a lattice structure 231, a Voronoi structure 232, a TPMS structure 233, or a mesh structure 234. This design ensures the mechanical strength of the high-stress areas while reducing the overall weight.

[0038] Reference Figure 8 After completing the multi-scale structural design, the 3D model is sliced ​​using slicing software and then imported into additive manufacturing equipment for integrated printing. PEKK polymer material is used for additive manufacturing to ultimately produce the finished skull patch. This finished product is non-toxic and non-allergenic to human tissue and can safely integrate with the human body for a long time.

[0039] In summary, the test results show that the skull patch prepared in this embodiment has a significantly reduced mass of 21.04% compared to a solid structure, while still maintaining good impact resistance and structural stability.

[0040] This invention proposes a multi-scale functional gradient biomimetic skull patch design and fabrication method, which effectively solves the problems of insufficient mechanical properties, single biological interface function, excessive structural weight and poor additive manufacturing adaptability of existing skull implants. It successfully provides a comprehensive solution that combines lightweight, high impact resistance, excellent biocompatibility and good additive manufacturing adaptability.

[0041] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for designing and fabricating a multi-scale functional gradient biomimetic skull patch, characterized in that: Includes the following steps: Step 1: Obtain medical imaging data of the patient's skull and establish a three-dimensional model of the skull defect area; Step 2: Based on the hierarchical structural characteristics of the natural skull inner table-cancellous bone-outer table, construct a three-layer functional gradient model; Step 3: Perform finite element static analysis and impact dynamic analysis on the middle layer region to obtain the stress transmission path inside the skull patch; Step 4: Construct a radial-circular coupled bionic energy dissipation network based on the stress transmission path. The radial-circular coupled bionic energy dissipation network includes: a radial main load-bearing unit arranged along the impact diffusion direction and a circular energy dissipation connection unit connected to the radial main load-bearing unit. Step 5: Based on the finite element stress distribution results, perform local subtractive optimization on the middle layer structure, and construct microscale buffer permeable units in the low stress region. The microscale buffer permeable units are one or more of the following: lattice structure, Voronoi structure, TPMS structure, or mesh structure. Step 6: Design differentiated interfaces for the inner and outer layers of the skull patch, with the inner layer using a continuous smooth structure and the outer layer using an open structure; Step 7: The optimized skull patch is then formed using additive manufacturing.

2. The method for designing and fabricating a multi-scale functional gradient biomimetic skull patch according to claim 1, characterized in that, The functional gradient three-layer model includes: an inner protective layer located on the brain tissue side, a biomimetic support layer located in the middle region, and an outer fusion layer located on the scalp tissue side.

3. The method for designing and fabricating a multi-scale functional gradient biomimetic skull patch according to claim 1, characterized in that, The low-stress region was determined using finite element stress contour plots.

4. The method for designing and fabricating a multi-scale functional gradient biomimetic skull patch according to claim 1, characterized in that, The mid-layer structural nodes adopt a rounded corner transition design.

5. The method for designing and fabricating a multi-scale functional gradient biomimetic skull patch according to claim 2, characterized in that, The outer fusion layer is provided with through holes or semi-through holes to promote tissue attachment and nutrient exchange; the inner protective layer adopts a low-roughness continuous surface to reduce irritation to the dura mater.

6. The method for designing and fabricating a multi-scale functional gradient biomimetic skull patch according to claim 1, characterized in that, The skull patch material used for additive manufacturing of the optimized skull patch includes one or more of PEKK, PEEK, PEK, PPSU, and titanium alloy.

7. The method for designing and fabricating a multi-scale functionally graded biomimetic skull patch according to any one of claims 1-4, characterized in that, The skull patch prepared by this method includes: an inner protective layer located on the side of the brain tissue, a biomimetic support layer located in the middle region, and an outer fusion layer located on the side of the scalp tissue; the outer fusion layer is provided with an open structure, the inner protective layer is a continuous smooth structure, and the biomimetic support layer has a radial-circular coupled biomimetic energy dissipation network constructed inside.

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