Mechanical Properties and In Vitro Degradation of Sputtered Biodegradable Fe-Au Foils

Iron-based materials proved being a viable candidate material for biodegradable implants. Magnetron sputtering combined with UV-lithography offers the possibility to fabricate structured, freestanding foils of iron-based alloys and even composites with non-solvable elements. In order to accelerate the degradation speed and enhance the mechanical properties, the technique was used to fabricate Fe-Au multilayer foils. The foils were annealed after the deposition to form a homogeneous microstructure with fine Au precipitates. The characterization of the mechanical properties was done by uniaxial tensile tests. The degradation behavior was analyzed by electrochemical tests and immersion tests under in vitro conditions. Due to the noble Au precipitates it was possible to achieve high tensile strengths between 550 and 800 MPa depending on the Au content and heat treatment. Furthermore, the Fe-Au foils showed a significantly accelerated corrosion compared to pure iron samples. The high mechanical strength is close to the properties of SS316L steel. In combination with the accelerated degradation rate, sputtered Fe-Au foils showed promising properties for use as iron-based, biodegradable implants.