Biodegradable iron based thin films for medical applications

• Applicant: Dr. Christiane Zamponi
• Subject Area: Biomaterials
• Term: from 2013 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 237012428

Biodegradable materials are subject of intense scientific research in recent years, in particular for their application as temporary medical implants. The two most important metallic materials in this respect are magnesium and iron. Whereas the bio-corrosion of magnesium in the human body processes under the formation of hydrogen with high rate leading to premature device failure, bio-corrosion of iron proceeds too slowly. However, by alloying additional elements, corrosion as well as mechanical properties can be tuned. Within this project, structured foils of highly pure iron and iron based alloys will be fabricated and characterized for their intended use as micro implants. These foils will be deposited and structured using magnetron sputtering and microsystem technology processes, respectively. Besides the influence of the precipitates of the mechanical and the corrosion behavior, an important focus in this project in the influence of the surface finishing. In the ongoing project a process to realize structured Fe-foils was developed. Due to the lithographic process the edges /aspect have a different roughness compared to the top and bottom. It is known that the roughness limits the mechanical fatigue behavior. Three different surface treatments will be carried out: micro shot peening, chemical and electrochemical polishing. The challenge is to adapt this for bulk material well known technology to sputtered films. After that, the fatigue behavior will be investigated in air and also in artificial simulated body fluids, like e.g. hanks solution depending on the surface finishing. All developed iron based material foils will be characterized by tensile tests, corrosion experiments, contact angle measurements and structural investigations (XRD, SEM, EDS, TEM). Using sacrificial layers, thicker metallic foils will be released from their substrate. Another focus of this project is the investigation cell toxicity of the developed iron based alloys. The cytotoxicity depending on the compound and the surface finishing will be investigated. Due to developed structuring process it is possible to generate freestanding iron based foils with an open pattern (net structure). The size and shape of the opening has an influence of the cell viability and the cell adhesion. Net like structures are preferred for temporary implantation because the stability and the degradation can be influence by the design. The cell growth on structure iron based free standing films will be investigated.The envisaged goal is to obtain structured, iron-based foils with high thicknesses in the range of 50 µm that are well suited for their use as microimplants. The Kieler Nanolabor offers the infrastructure and the equipment required for this proposal.

• DFG Programme: Research Grants