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E-beam sterilization of microstructures in titanium surfaces for medical implants

Elektronenstrahlsterilisation von Mikrostrukturen auf Titanoberflächen für medizinische Implantate. E-beam sterilization of microholes and microstructures in titanium surfaces for medical implants
: Winkler, Sebastian; Dietze, Marleen; Edelmann, Jan

European Society for Precision Engineering and Nanotechnology -EUSPEN-:
17th International Conference & Exhibition of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2017 : 29th May – 2nd June 2017, Hannover, Germany
Bedford: Euspen, 2017
ISBN: 978-0-9957751-0-7
European Society for Precision Engineering and Nanotechnology (EUSPEN International Conference & Exhibition) <17, 2017, Hannover>
Fraunhofer IWU ()
Fraunhofer FEP ()
microholes; microstructures; titanium; implant; sterilization; electron beam irradiation

Due to its biocompatibility titanium is the metal of choice for most medical implants. The surface in contact with the human body may be equipped with a functional microstructure for various purposes such as bone ingrowth. All implants must be sterilized before operation. Among other processes, the sterilization by low energy electron beam (e-beam-sterilization) offers a lot of advantages. The non-thermal sterilization works with short process times (milliseconds) and without microbicide gases. The radiation sterilization is a regulated process according to DIN EN ISO 11137, which describes a killing effect of microorganism after the validation of a dose of 25 kGy. In principal it is possible to sterilize all material classes, electronic devices and different geometries, so that the low energy e-beam-sterilization is a suitable method for multifunctional implants. The sterilization of surface microstructures with low energy e-beam-sterilization is challenging because of the limited penetration depth. The influence of high aspect ratio microstructures on low energy e-beam-sterilization was investigated experimentally. A microhole array with 230 μm hole diameter served as a model structure and was manufactured in the titanium surface by electrical discharge machining. Other surface microstructures were generated by laser machining and blasting. All samples were contaminated with 107CFU/sample Escherichia coli (E. coli) K12, sterilized by e-beam and incubated in a culture medium in order to prove that the sterilization was successful. The microhole depth was varied to determine the critical depth for low energy e-beam-sterilization.