High-strength low-stiffness porous NiTi scaffold manufactured via laser powder bed fusion.

Abstract

Laser powder bed fusion (LPBF) manufactured porous NiTi can achieve controlled porosity and architecture that not only tune mechanical properties to the physiological range but also promote osteointegration for orthopaedics implant applications. Nevertheless, most LPBF-manufactured porous NiTi structures fail to provide compressive strength required for load-bearing implants. To address this challenge, the present study explores the design and fabrication of porous NiTi structures specifically tailored for load-bearing applications. Four porous NiTi architectures were designed and fabricated via LPBF: cubic, gyroid, and two topology-optimised designs tailored to improve strength without sacrificing porosity. Their static and superelastic responses were systematically characterised through experiments and complemented by finite element analysis to reveal the deformation mechanisms and design-property relationships. The results highlight the pivotal role of unit cell geometry in governing mechanical behaviour. The gyroid design offered uniform stress distribution but lower strength due to its compliant, rotation-dominated deformation. In contrast, the cubic and topology-optimised structures achieved higher yield strength and compressive strength, with the topology-optimised designs outperforming conventional architectures reported in the literature at similar porosity levels. More importantly, the optimised porous NiTi structures sustained superior load-bearing capacity while keeping low stiffness and retaining bone-like superelastic recovery under high stresses. These findings provide new insights into how porous architecture governs the mechanical and functional performance of NiTi scaffolds. This study establishes practical design guidelines for the development of high-strength, low-stiffness porous NiTi structures, advancing their application as promising load-bearing implants in orthopaedics.