Structure-property relationships in 3D printed bone scaffolds: Role of TPMS architecture and porosity in PLA and nanohydroxyapatite reinforced composites

Abstract

Additive manufacturing of bone scaffolds enables the fabrication of patient-specific inter-connected porous structures that facilitate tissue generation with closely matched mechanical and biological properties of natural bone. This study examines how TPMS architecture, porosity, and material composition impact the compressive strength and stiffness of 3D printed PLA and PLA/nHA scaffolds for bone repair. Filaments are produced via a single-screw extrusion system and 3D printed into ASTM D695 specimens with 50%, 60%, and 70% porosity. Compression tests evaluated the effects of TPMS designs, porosity, and material composition on strength and elastic modulus. IWP scaffolds exhibited the highest mechanical properties, while FRD showed the lowest. The addition of nHA increased the compressive strength by 7.76% and the elastic modulus by 24.79%, with improved crystallinity shown in the XRD analysis. However, SEM images showed the formation of pores in the composite filaments, which may act as stress concentrators and limit the mechanical performance. ANOVA results confirmed TPMS design and porosity as the most significant factors influencing mechanical performance, while material composition had a lesser effect, particularly on compressive strength. TPMS-based PLA/nHA scaffolds show strong potential for bone regeneration, with IWP and gyroid structures exhibiting higher mechanical strength even at high porosity levels.

keywords: Bone scaffolds, composites, fused filament fabrication, mechanical properties, TPMS