Metallurgical expert Heraeus Amloy is working with the University of Graz to 3D-print new medical devices made from amorphous metals.As part of the Clinical Additive Manufacturing for Medical Applications (CAMED) program, the research will allow partners to develop and test new alloy powders for end-use implants and prostheses.Because of the extraordinary mechanical properties of amorphous alloys, the new 3D printing equipment is expected to perform significantly better than existing equipment made of steel or titanium.
“As part of the CAMED project, we are currently testing the Amloy-ZR02 alloy,” said Jurgen Wachter, Head of Hereus Amloy.Its main ingredient is high-purity zirconium, which has been proven to be biocompatible.”
A set of 3D-printed radius-plate implants made of amorphous metals.Image from Heraeus.
Limitations of conventional medical implants
To date, most metal-based medical implants have been made of stainless steel, cobalt-chromium or titanium.While most of these alloys work, even when they are custom-printed, they struggle to adapt to the changing forces inside a patient’s body.
A titanium costal arch, for example, is forced to undergo about eight million breathing movements per year.Thermo-temperature titanium does not provide enough elasticity, so an implant may be difficult to place in a patient’s chest if it is not optimally anchored to the surrounding bone.Although minimum force is applied with each breathing cycle, the sheer number of cycles will eventually lead to fatigue fractures, especially over a longer period of time.
Anotomics, an Australian medical device company, has previously made 3D-printed titanium rib implants.Photographed by Anotomics.
Why use amorphous metals?
An amorphous metal or metallic glass is formed by shaking a molten metal pool, which means the atoms in the material don’t have enough time to form a lattice structure.Instead, the atoms solidify in an irregular and disordered (amorphous) structure similar to glass.This results in an excellent set of physical properties, including corrosion resistance, excellent strength characteristics and high elasticity.It is this combination of strength and elasticity that makes this material class well suited for permanent load applications such as medical implants.
Ultimately, the Heraeus project aims to improve the machinability of these amorphous metals so that they can be 3D-printed on most industrial laser powder bed melting systems.With 3D-printed implants, healthcare professionals will be able to create the next generation of patient-specific devices tailored to each wearer’s physique.This is expected to be particularly convenient when dealing with injuries caused by accidents and tumour removal, as the implantation of implants after such events can be a complex process.
Valeska Melde, Head of Marketing and Sales at Heraeus Amloy, concludes: “Amorphous metals have many advantages over steel and titanium: the material has both strength and elasticity.It fits perfectly to bone, promotes recovery, and is well tolerated because it can be implanted without causing cell deformation.”
While the company has been in the limelight for some time, Heraeus is known for producing the world’s largest 3D-printed amorphous metal parts.Printed in 2019, the gear is made from the company’s proprietary AMZ4 metal powder and has a diameter of 110mm.
More recently, Heraeus has partnered with machine tool maker Trumpf to promote the use of 3D-printed amorphous parts for engineering applications.By making materials more cost efficient when 3D printed, the partners aim to establish additive manufacturing for amorphous metal parts as a standard production method on the shop floor.
