Researchers at City University of Hong Kong (CityU HK) have developed novel artificial bone scaffolds with a high deformation recovery capability of 6% –7%, compared to 2% – 4% for natural bone and less than 1% for conventional metallic scaffolds. Additionally, these scaffolds allow for flexible adjustments of properties like strength, modulus, and permeability to meet specific implantation site requirements.
Reported in the International Journal of Extreme Manufacturing , this work provides valuable insights into developing high-performance artificial bone scaffolds and other multifunctional metamaterials for diverse engineering applications.
The global demand for bone implants is sharply increasing, with projections estimating a market value of $64.27 billion by 2030.
"Artificial bone scaffolds are a critical part of implants, but existing scaffolds still fall short of being ideal," stated Prof. Jian LU, the corresponding author of this paper and Chair Professor in the Department of Mechanical Engineering at CityU HK. "Scaffolds serve as partial implants to address localized bone loss and must closely mimic the properties of natural bone at the implantation site. For instance, they should possess adequate deformation recovery and offer adjustable modulus, strength, and permeability to match the site's characteristics. Unfortunately, conventional metal scaffolds have yet to meet these expectations."
NiTi alloys are biocompatible metals with excellent deformation recovery capabilities (also known as superelasticity). Since the late 20th century, researchers have explored their use in implants, including orthodontic wires, bone plates, and vascular stents. However, the complex topological structures of bone scaffolds pose challenges for traditional manufacturing methods.
The advent of 3D printing technology offers a solution for fabricating NiTi scaffolds. Nonetheless, preliminary studies reveal difficulties in controlling the performance of 3D-printed NiTi scaffolds, with unclear strategies for achieving optimal superelasticity and a broad range of tunable properties.
Using laser powder bed fusion technology (a 3D printing technique), Prof. Jian LU's team synergistically optimized the microstructure and macrostructure of NiTi scaffolds, resulting in scaffolds with hierarchical microstructures and gyroid-sheet topologies.
This design enhances reversible martensitic phase transformation, significantly improving the scaffolds' superelasticity. Furthermore, by adjusting the volume fraction and unit cell size, a wide range of mechanical and mass transfer properties was achieved, enhancing the scaffolds' applicability.
"Compared with previously reported scaffolds, our superelastic NiTi scaffolds more closely match the deformation behavior of natural bone and offer adaptable properties to meet the diverse needs of different implantation sites," said Shiyu ZHONG, first author of the paper and a PhD student under Prof. Jian LU. "Future research will focus on the biocompatibility and durability (including fatigue, corrosion, etc.) of these scaffolds to enhance their clinical applications."
International Journal of Extreme Manufacturing (IJEM, IF: 21.3) is dedicated to publishing the best advanced manufacturing research with extreme dimensions to address both the fundamental scientific challenges and significant engineering needs.
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