Amplifying the antimicrobial efficacy of titanium-copper alloys through blended powder laser powder bed fusion

Abstract

Skeletal implant infection (peri-implantitis) remains a major clinical challenge, despite identification of alloy compositions with promising antimicrobial performance. This study explores the opportunity to refine the microstructure of alloys through blended powder laser powder bed fusion (BP-LPBF) manufacturing, focusing on enhancing biological responses. Using antimicrobial Ti-Cu alloys as a case study system, we show that BP-LPBF produces distinct microstructures compared to conventional casting, with performance governed by the spatial distribution and connectivity of Cu-rich phases rather than composition alone. Ti-3Cu (wt%) was found to achieve a refined microstructure with minimal intermetallic formation, strong antibacterial performance (> 99% S. aureus and E. coli after 24 h), and excellent cytocompatibility (78% after 7 days). In contrast, Ti-11.5Cu exhibited superior antibacterial effects (99.9% for S. aureus and 99.99% for E. coli) due to higher Cu ion release, microstructural heterogeneity, and greater Ti2Cu formation; however, it suffered from compromised ductility and cytotoxicity. Importantly, Cu ion release from all alloys was several orders of magnitude lower than reported bactericidal thresholds, indicating that antimicrobial activity is predominantly governed by surface-mediated mechanisms rather than bulk ion release. Spatially localised Cu-rich phases generate micro-galvanic interactions and potentially elevated near-surface Cu activity, enabling effective bacterial inactivation. Under oxidative conditions, increased ion release provides a secondary contribution, supporting a dual-mechanism model. Compared to cast equivalents, BP-LPBF fabricated Ti-Cu alloys exhibited enhanced bio-functionality even at lower Cu levels. Beyond acting as a powerful platform for accelerating alloy development, we also demonstrate LPBF production of multi-material implants with antimicrobial Ti-Cu surface features.