Designing Titanium Alloys with Enhanced Biological Functionalities Using Additive Manufacturing

Sushant Ciliveri

doi:10.7273/000006302

With over 7 million yearly orthopedic surgeries in the US alone, the attention towards metallic implant materials for orthopedic applications has gained much importance in the past 2 decades. The advent of metal additive manufacturing (AM) aiding the processing of patient-specific implants has proved to be a boon for the implant manufacturing sector. Challenges persist with delayed implant-host bone tissue integration and bacterial infections at the implant site. Addressing these issues requires revision surgery. However, elderly patients with immunocompromised bone health cannot undergo the physical toll of revision surgeries on their overall health, reducing their life expectancy. The long-term stability of an implant in vivo depends on its early-stage osseointegration. Titanium is the ultimate choice of metallic biomaterial, and is bio-inert in nature. There is an unmet need in the orthopedic metallic implant sector with enhanced biological performance in vivo, leading to accelerated bone-tissue growth on the implant surface. Current strategies include structural modification (surface porosities) and material chemistry intervention to aid accelerated bone-tissue integration. Along with the biological performance, the processing feasibility via AM and mechanical integrity of the alloy designs are essential parameters. This dissertation focuses on three significant aspects of titanium-based orthopedic implants: structure, material chemistry, and manufacturability via AM. The dissertation begins from the surface of an implant and is driven into bulk material modification. The dissertation further discusses a Ti-alloy design to replace the commercially used Ti6Al4V alloy for orthopedic applications, starting with exploring the structural integrity of porous surface coatings and modifying its material chemistry. Surface chemistry modifications include the addition of osteogenic MgO and angiogenic SiO2, and antibacterial Cu to Ti, showing superior in vivo biological performance to commercially pure titanium (CpTi). The first step in designing the bulk implant material was to reduce the Al and V contents in Ti6Al4V to design an alloy, Ti3Al2V, specifically for the orthopedic industry. Bioactive Ta and antibacterial Cu were added to this alloy, proving superior in vivo performance without significant degradation in mechanical strength compared to Ti6Al4V. Additive manufacturing of this designed Ti-Ta-Cu alloy was explored via print-parameter optimization with higher energy densities since Ta and Cu need higher energy input for laser-based AM.

Designing Titanium Alloys with Enhanced Biological Functionalities Using Additive Manufacturing

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