Development of antimicrobial metal alloys

Rabbitt, Daisy Lily Adonia ORCID: 0000-0002-2727-0700 (2025). Development of antimicrobial metal alloys. University of Birmingham. Ph.D.

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Abstract

With rising rates of orthopaedic implant infections and antimicrobial resistance, novel methods to combat these clinical challenges are greatly needed. This thesis focusses on producing an inherently antimicrobial material to offer a localised solution for infection prevention.

Ti-Cu alloys are investigated as potential candidates for biomedical alloys due to their evidenced antimicrobial efficacy. This thesis contributes knowledge to understanding what microstructural features drive the antimicrobial efficacy of Ti-Cu alloys and demonstrates that additive manufacturing may be used to amplify these effects.

Initially, arc melted specimen of Ti-11.5 (wt.%) Cu and Ti-33 (wt.%) Cu were manufactured and heat treated to examine the influence of microstructural refinement to fine tune antimicrobial efficacy. Larger (approximately 5 µm), rounded TixCu precipitates had increased antimicrobial efficacy, compared to nanoscale and elongated precipitates, though no specimen showed efficacy towards E. coli.

Further investigations using powder metallurgy and additive manufacturing demonstrated that processing routes markedly affect microstructure and copper ion release, enhancing antimicrobial potency. Notably, AM-fabricated alloys with only 3 wt.% Cu exhibited significant antimicrobial efficacy against both S. aureus and E. coli. Improvements in their responses to native bone cells were also prominent, with cell viability of 78 % and 51 % after 7 days for Ti-3Cu and Ti-11.5Cu respectively. However, concerns around the long-term biocompatibility of Ti-11.5Cu due to the ion release mechanism must be considered.

Finally, to address concerns around the mechanical mismatches that may lead to aseptic loosening, the potential for developing a Ti-Mo-Cu alloy was explored. Using low laser energy densities and post-processing heat treatments, successful Mo diffusion was achieved. This led to fabrication of promising alloy systems with 100 % antimicrobial efficacy. These findings underscore the importance of compositional tuning and role of heat treatments in optimising both the mechanical integrity and biological functionality of titanium alloys for advanced biomedical applications.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):