de Wild, Michael

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Michael
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de Wild, Michael

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2020 - 20212
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Autor:in: Schuler, Felix × Thema: NiTi ×

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  • Vorschaubild
    Publikation
    Exploitation of transition temperatures of NiTi- SMA by adjusting SLM parameters
    (De Gruyter, 2021) Schuler, Felix; Dany, Sebastian; John, Christoph; de Wild, Michael [in: Current Directions in Biomedical Engineering]
    Abstract:It is well known that the transition temperatures, e.g. the austenite peak temperature Ap, of NiTi Shape Memory Alloys (SMAs) can be adjusted by changing the alloy composition. This topic recently became more interesting due to the possibilities to produce SMA-parts by additive manufacturing, specifically by Selective Laser Melting (SLM). The potential of new designs and smart structures by so-called 4D-printingwith locally adjusted transition temperatures Appotentially opensup new applicationsand novel temperature-responsive medical devices. This work focuses on the SLM manufacturing parameters exposure time ET(scanning speed) and laser power Pand their impact on the transition temperatureApbeyond the commonly used generic process parameter energy density ED. By systematical variation of process-and scan-parameters, the impact of the P, ET, sample orientation and layer heightLHas well as interdependencies between them have been studied. Awide range of transition temperatures Apbetween -20°C and 70°C has been reached from one starting material by varying ET. These findings potentially allow the manufacturing of smart devices with multi-stage deformation processes in a single 4D-printed part
    01A - Beitrag in wissenschaftlicher Zeitschrift
  • Vorschaubild nicht verfügbar
    Publikation
    Smart 4D-printed implants and instruments
    (De Gruyter, 09/2020) de Wild, Michael; Schuler, Felix [in: Current Directions in Biomedical Engineering]
    Selective laser melting (SLM) was used to manufacture smart programmed structures with customized properties made of biocompatible NiTi shape-memory alloy. A series of helixes was produced with systematically varied SLM process parameters Laser Exposure Time and Laser Power in order to specifically change the thermo-mechanical material properties of the 3D-structures. This innovation opens up the possibility to adjust the NiTi phase transformation temperature during the manufacturing process. This controllable property determines which of the two crystallographic phases martensite or austenite is present at a certain operating temperature and allows the mechanical properties to be adjusted: martensitic devices are soft and pseudo-plastic due to the shape-memory effect, whereas austenitic structures are pseudo-elastic. In a further step, the SLM process parameters were locally varied within 4D-printed twin-helixes. As a result, the phases, respectively the mechanical properties of a single component were adjusted at different locations. The ratio of elastic to plastic deformation and the spring constant of the helix can be locally controlled. This allows, for example, the spatio-temporal programming of 3D-printed surgical instruments or implants that are stimuli-responsive.
    01A - Beitrag in wissenschaftlicher Zeitschrift