CityU researchers 3D-print NiTi bone scaffolds with 6–7% flexibility, matching natural bone and surpassing current implants
Researchers at City University of Hong Kong have achieved a significant milestone in the field of regenerative medicine. They have successfully 3D-printed nickel-titanium (NiTi) bone scaffolds that combine superelasticity with tunable strength and porosity. Using advanced laser powder bed fusion, the team created implants that recover 6–7% of deformation, matching the flexibility of natural bone and outperforming conventional metal scaffolds. This breakthrough has the potential to revolutionise bone repair and regenerative medicine, offering new hope for patients and medical professionals alike.
The findings are detailed in the International Journal of Extreme Manufacturing.
Global demand for artificial bone implants is rising rapidly
The artificial bone implant market is experiencing rapid growth, 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 Professor 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.”
While NiTi alloys have been used in bone implants, orthodontic wires, bone plates, and vascular stents for decades due to their biocompatibility and excellent deformation recovery capabilities, the complex topological structures of bone scaffolds have posed unique challenges in traditional manufacturing methods.
How 3D printing solves challenges within NiTi bone scaffolds
3D printing technology offers a solution for fabricating NiTi bone scaffolds. However, 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.
The researchers utilised laser powder bed fusion technology to synergistically optimise the microstructure and macrostructure of NiTi scaffolds synergistically, resulting in bone scaffolds with hierarchical microstructures and gyroid-sheet topologies.
This innovative design enhances the reversible martensitic phase transformation, significantly improving the superelasticity of the bone scaffolds. 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.
The researchers found that innovative NiTi bone scaffolds had a maximum recoverable strain of 6%-7%, surpassing conventional counterparts and effectively meeting the deformation demands of natural bones (4%). The superelasticity evolves from enhanced martensitic transformation through multiscale optimism, which involves stabilizing B2 phases and replacing coarse columnar grains with hierarchical microstructures, and employing an efficient sheet topology instead of the commonly adopted strut topology.
“Compared with previously reported scaffolds, our superelastic NiTi scaffolds more closely match the deformation behaviour 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.”