Improving predictability of additively manufactured Ti-6Al-4 V lattices for orthopaedic devices: A parametric and struts angle study

Abstract

The advancement of metal additive manufacturing has recently enabled the integration of porous lattice regions into orthopaedic devices. Despite the increased utilisation of various metamaterials there remains limited understanding of how to optimise laser process specifically for these geometries. Selective laser melting (SLM) of representative single struts is focused on this study from the perspective of surface properties, mechanical performance, and in-vitro biological response. Specifically, the influence of laser power (100 – 200 W) and speed (2250 – 900 mm/s) and struts angle (20–90°) for a 250μ m strut diameter was explored. Struts built below 45° to the substrate using optimal laser parameters (150 W and 1125 mm/s) were found to exhibit a surface topography that facilitated the highest level of cell adhesion (84.3 cells/mm2) after 24 hrs (p ≤ 0.001). To support this finding, a novel image analysis method was developed to characterise the average roughness across the complete strut profile. An opposite trend was observed for mechanical strength with struts built at above 45° without failure. These findings were brought together in a parameter design map was to guide stakeholders in producing customised biomedical devices, enabling control of key physiochemical properties with the aim of maximising osseointegration.

Keywords

• Selective laser melting
• Three-point bending
• Surface roughness
• Cell response
• Ti-6Al-4V Lattice