In order to research these implants, the group utilized selective laser melting (SLM), an emerging 3D printing technology that uses 3D CAD data and high-powered lasers to fuse powdered metal alloys layer-by-layer. The collaborative effort was initiated by SIMTech’s Florencia Edith Wiria and SC3DP’s Wai Yee Yeong, and through their work, they’ve already proved the ability to create biomedical prototypes out of titanium-aluminum-based powders. The issue with aluminum, however, is the potential negative long-term effects that the material could have on human neurology, leading the researchers to turn to an equal mixture of titanium and tantalum alloys.
Although the combination of these alloys is perfect for implants, particularly due to their biocompatibility and mechanical superiority to standalone titanium, there were still a few kinks to work out with the unique tantalum material. Tantalum, a rare, blue-gray metal, has an extremely high melting point of over 3,000 degrees Celsius, making it difficult and costly to turn the tantalum into finely dispersed microspheres engineered for SLM printing. But by mixing the rough, elongated tantalum powder with a titanium microsphere powder, the researchers were able to use the SLM printing process and retain the spherical shape of the titanium alloy, which was vital to the success of the mixture.
“The titanium powder acts as a rolling medium,” Wiria explained. “It pushes the tantalum powder along and makes the processing by SLM possible.”
In order to 3D print these titanium-tantalum prototypes, the researchers needed to reduce the thermal stress of the material, which they succeeded in by applying ‘checkerboard’ laser scanning that melted down the metal materials in alternate up-and-down or side-to-side movements. Not only were the researchers able to show that mixed material was viable and printable, but X-ray and imaging technology actually showed that the addition of the tantalum material and rapid solidification both promoted and stabilized the formation of titanium grains.
“These alloys are specifically designed for orthopedic applications, and even have the potential to show a type of ‘shape-memory’ after being deformed,” Yeong said. “This opens up the possibilities of printing personalized devices to improve patient care.”