E. Quandt, University of Kiel, Kiel, Germany; H. Rumpf, V. Wipperfuerth, C. Zamponi, Research Center Caesar, Bonn, Germany
NiTi-films were deposited on silicon substrates by magnetron sputtering technique. Typical deposition rates of 10 µm/h allowed the fabrication of freestanding films of a thickness adjustable between 5 and 50 µm. A remarkable high mechanical stability was achieved in these films revealing an ultimate tensile strength of 1180 MPa at a maximum strain of 11.5%. At 37°C superelastic properties were demonstrated showing a closed-loop hysteresis in tensile testing and a plateau of more than 5% strain. Photolithography and wet etching technology were applied in order to fabricate planar thin film devices. Achievable structure sizes range in the order of the NiTi film thickness, i.e. typically between 5 and 15 µm. Tensile testing experiments revealed a remarkable strain tolerance particularly in net-shaped structures which summed up to a superelastic strain of up to 5%.
Moreover, it has been shown that the deposition process can be transferred to the fabrication of NiTi tubes, which have high potential for application as vascular implants, e.g. stents. First experiments on the micro-structuring of such tubes were performed demonstrating the possibility to transfer the planar fabrication route to three-dimensional objects.
Financial support of the Deutsche Forschungsgemeinschaft through SFB 459 is gratefully acknowledged.
NiTi-films were deposited on silicon substrates by magnetron sputtering technique. Typical deposition rates of 10 µm/h allowed the fabrication of freestanding films of a thickness adjustable between 5 and 50 µm. A remarkable high mechanical stability was achieved in these films revealing an ultimate tensile strength of 1180 MPa at a maximum strain of 11.5%. At 37°C superelastic properties were demonstrated showing a closed-loop hysteresis in tensile testing and a plateau of more than 5% strain. Photolithography and wet etching technology were applied in order to fabricate planar thin film devices. Achievable structure sizes range in the order of the NiTi film thickness, i.e. typically between 5 and 15 µm. Tensile testing experiments revealed a remarkable strain tolerance particularly in net-shaped structures which summed up to a superelastic strain of up to 5%.
Moreover, it has been shown that the deposition process can be transferred to the fabrication of NiTi tubes, which have high potential for application as vascular implants, e.g. stents. First experiments on the micro-structuring of such tubes were performed demonstrating the possibility to transfer the planar fabrication route to three-dimensional objects.
Financial support of the Deutsche Forschungsgemeinschaft through SFB 459 is gratefully acknowledged.
