3D Carbon Bone Scaffolds via Laser Sintering and Pyrolysis
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Solution Overview
Problem
Titanium implants for bone repair suffer from stiffness mismatch with bone, leading to stress-shielding and potential implant loosening, and metal ions can cause adverse biological reactions, necessitating the development of materials with improved biocompatibility and mechanical properties.
Innovation Solution
A two-step process using additive manufacturing to produce carbon structures by sintering a fusible organic polymer and subsequent pyrolysis to create a high-carbon content material, such as pyrolytic carbon, which mimics bone stiffness and reduces metal ion release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If titanium implants are used for bone repair, then load-bearing capability is improved, but stiffness mismatch causes stress-shielding and implant loosening
Solution Approach 1:
The patent applies porous materials by creating a porous carbon structure through pyrolysis of a foam precursor. The porous structure reduces the effective stiffness of the implant to match bone stiffness while maintaining load-bearing capability through the porous framework, thereby eliminating stress-shielding and preventing implant loosening.
Solution Approach 2:
The patent applies parameter changes by controlling the density and pore size of the carbon structure through pyrolysis conditions. By adjusting the bulk density (e.g., 0.2-2.0 g/cm³) and pore characteristics, the implant's mechanical properties are tuned to achieve stiffness matching with bone while retaining sufficient strength for load-bearing applications.
2Strength
If metal implants are used, then structural integrity is improved, but metal ion release causes adverse biological reactions
Solution Approach 1:
The patent applies this principle by using carbon, a non-metallic material that does not release harmful metal ions. While carbon structures may have different longevity characteristics compared to metals, they eliminate the biological harm caused by metal ion release, providing a biocompatible alternative for implant applications.
Solution Approach 2:
The patent applies composite materials by creating a porous carbon structure that combines the benefits of metallic strength (through the carbon framework) with the biocompatibility of non-metallic materials. The porous carbon composite provides structural integrity while avoiding the harmful effects of metal ion release.
3Strength
If dense metallic implants are used, then mechanical strength is improved, but biocompatibility and stress distribution are worsened
Solution Approach 1:
The patent applies porous materials to create a carbon structure with controlled porosity that reduces stiffness to match bone while maintaining mechanical strength through the porous framework. This allows for better stress distribution and eliminates stress-shielding while preserving load-bearing capability.
Solution Approach 2:
The patent applies parameter changes by controlling the density, pore size, and pore distribution of the carbon structure. By optimizing these parameters, the implant achieves a balance between mechanical strength and stiffness matching, enabling both structural integrity and biocompatibility.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method produces carbon structures with mechanical properties closer to bone, minimizing stress-shielding and adverse biological reactions, offering a sustainable and cost-effective alternative for biomedical implants with tailored properties.
Implementation Method 1
Selective laser sintering is a known method of AM which typically includes the following general steps. Powdered material such as plastic, metal, ceramic or glass is spread onto a platform and a laser is used to selectively heat an area of powdered material corresponding to a two-dimensional cross section of the final three dimensional structure. The heat from the laser causes the powdered material to fuse together.
Implementation Method 2
Pyrolytic carbon or pyrocarbon is a synthetic substance that is generally produced by heating organic material in the absence of oxygen. It has excellent biocompatibility and hardness and is anti-thrombotic.
Data Source
AI summary
The present invention relates to a method for making a three dimensional carbon structure and also to a sintered article comprising pyrolysed carbon particles. The method comprises sintering a powdered organic material, preferably using selective laser sintering, to form a sintered three dimensional structure having a desired shape. The sintered structure is then pyrolysed to form the final carbon structure. The method is particularly useful in the production of biomedical implants such as bone scaffolds and joint replacements. In some embodiments, the powdered organic material is lignin which provides a renewable and highly cost effective starting material for the method of the present invention.