Institut für Medizintechnik und Medizininformatik
Dauerhafte URI für die Sammlunghttps://irf.fhnw.ch/handle/11654/23
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Ergebnisse nach Hochschule und Institut
Publikation Reinigungseffektivität und Kavitationsrauschpegel bei Ultraschall-unterstützter wässriger Reinigung von Medizinprodukten(2012) Jung, Christiane; Budesa, Boris; Fässler, Fabian; Uehlinger, Robert; Müller, Thomas; Schaffner, Patrik; Bläsi, Simon; de Wild, Michael04B - Beitrag KonferenzschriftPublikation Exploitation of transition temperatures of NiTi- SMA by adjusting SLM parameters(De Gruyter, 2021) Schuler, Felix; Dany, Sebastian; John, Christoph; de Wild, MichaelAbstract: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 part01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Molecular assembly and self‐assembly: molecular nanoscience for future technologies(2003) de Wild, Michael; Berner, Simon; Suzuki, Hitoshi; Ramoino, Luca; Baratoff, Alexis; Jung, Thomas A.In this review the emerging science of single molecules is discussed in the perspective of nanoscale molecular functions and devices. New methods for the controlled assembly of well-defined molecular nanostructures are pre- sented: self assembly and single molecular positioning. The observation and selective modification of conformation, electronics, and molecular mechanics of individual molecules and molecular assemblies by scanning probes is dem- onstrated. To complement this scientific review, some of the possible conse- quences and visions for future developments are discussed, as far as they derive from the presented systems. The prospects of nanoscale science to stim- ulate technological evolution are exemplified.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Comparison of methods for testing ultrasound in the cleaning bath(2014) Zwahlen, Alexander; de Wild, Michael; Jung, Christiane04B - Beitrag KonferenzschriftPublikation Microstructure of selective laser melted nickel–titanium(Elsevier, 2014) Bormann, Therese; Müller, Bert; Schinhammer, Michael; Kessler, Anja; Thalmann, Peter; de Wild, MichaelIn selective laser melting, the layer-wise local melting of metallic powder by means of a scanning focused laser beam leads to anisotropic microstructures, which reflect the pathway of the laser beam. We studied the impact of laser power, scanning speed, and laser path onto the microstructure of NiTi cylinders. Here, we varied the laser power from 56 to 100 W and the scanning speed from about 100 to 300 mm/s. In increasing the laser power, the grain width and length increased from (33 ± 7) to (90 ± 15) μm and from (60 ± 20) to (600 ± 200) μm, respectively. Also, the grain size distribution changed from uni- to bimodal. Ostwald-ripening of the crystallites explains the distinct bimodal size distributions. Decreasing the scanning speed did not alter the microstructure but led to increased phase transformation temperatures of up to 40 K. This was experimentally determined using differential scanning calorimetry and explained as a result of preferential nickel evaporation during the fabrication process. During selective laser melting of the NiTi shape memory alloy, the control of scanning speed allows restricted changes of the transformation temperatures, whereas controlling the laser power and scanning path enables us to tailor the microstructure, i.e. the crystallite shapes and arrangement, the extent of the preferred crystallographic orientation and the grain size distribution.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Modulation of human osteoblasts by metal surface chemistry(Wiley, 2013) Hofstetter, Wilhelm; Sehr, Harald; de Wild, Michael; Portenier, Jeannette; Gobrecht, Jens; Hunziker, Ernst B.The use of metal implants in dental and orthopedic surgery is continuously expanding and highly successful. While today longevity and load-bearing capacity of the implants fulfill the expectations of the patients, acceleration of osseo integration would be of particular benefit to shorten the period of convalescence. To further clarify the options to a ccelerate the kinetics of osseo integration, within this study,the osteogenic properties of structurally identical surfaces with different metal coatings were investigated. To assess the development and function of primary human osteoblastson metal surfaces, cell viability, differentiation, and gene expression were determined. Titanium surfaces were used as positive, and surfaces coated with gold were used as negative controls. Little differences in the cellular parameters tested for were found when the cells were grown ontitanium discs sputter coated with titanium, zirconium, niobium, tantalum, gold, and chromium. Cell number, activity of cell layer-associated alkaline phosphatase (ALP), and levels of transcripts encoding COL1A1 and BGLAP did not vary significantly in dependence of the surface chemistry.Treatment of the cell cultures with 1,25(OH)2D3/Dex,however, significantly increased ALP activity and BGLAP messenger RNA levels. The data demonstrate that the metallayer coated onto the titanium discs exerted little modulatory effects on cell behavior. It is suggested that the micro-environment regulated by the periimplant tissues is more effective in regulating the tissue response than is the mate-rial of the implant itself.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Molecular assembly and self-assembly. Molecular nanoscience for future technologies(Schweizerische Chemische Gesellschaft, 2002) de Wild, Michael; Berner, Simon; Suzuki, Hitoshi; Ramoino, Luca; Baratoff, Alexis; Jung, Thomas A.In this review the emerging science of single molecules is discussed from the perspective of nanoscale molecular functions and devices. New methods for the controlled assembly of well-defined mo lecular nanostructures are presented: self assembly and single molecular positioning. The observation and selective modification of conformation, electronics, and molecular mechanics of individual molecules and molecular assemblies by scanning probes are demonstrated. To complement this scientific review, some of the possible consequences and visions for future developments are discussed, as far as they derive from the presented systems. Here, the prospects of nanoscale science to stimulate technological evolution are ex emplified.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Novel microcalorimetric assay for antibacterial activity of implant coatings. The cases of silver‐doped hydroxyapatite and calcium hydroxide(Wiley, 08/2015) Braissant, Olivier; Chavanne, Philippe; de Wild, Michael; Pieles, Uwe; Stevanovic, Sabrina; Schumacher, Ralf; Straumann, Lukas; Wirz, Dieter; Gruner, Philipp; Bachmann, Alexander; Bonkat, GernotBiomaterials with antimicrobial properties are now commonly used in different clinical specialties including orthopedics, endodontic, and traumatology. As a result, assessing the antimicrobial effect of coatings applied on implants is of critical importance. In this study, we demonstrate that isothermal microcalorimetry (IMC) can be used for monitoring bacterial growth and biofilm formation at the surface of such coatings and for determining their antimicrobial effects. The antibacterial effects of silver doped hydroxyapatite (HA) and calcium hydroxide coatings on Staphylococcus epidermidis were determined with a minimal workload. Using the Gompertz growth model we determined biofilm growth rates close to those values reported in the literature. Furthermore, we were able to estimate the reduction in the bacterial inocula originally applied at the surface of the coatings. Therefore, in addition to monitoring the antimicrobial effect of silver doped HA and calcium hydroxide coatings, we also demonstrate that IMC might be a valuable tool for assessing such antimicrobial properties of implant coatings at a minimal workload.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Investigating dry electro-chemical polishing of titanium structures(De Gruyter, 2021) Simeunovic, Sven; Jung, Christiane; Mory, Dominik; Seiler, Daniel; de Wild, MichaelWith the introduction of novel automated polishing methods, more attention has recently been paid to post-processing methods of metallic implants. One such method is the polishing process known as DryLyte®. The most significant difference to previous electropolishing methods is the use of solid organic polymer particles activated with sulfonic acid acting as the electrolyte. The solid particle electrolyte raises new question in terms of polishing results for small features as well as overall polishing quality of metallic surfaces. The aim of this study was to determine the quality of the polishing process for titanium rods with different initial surface roughness and with tapped holes in three different orientations (0°, 45°, 90°) by subjecting them to the DryLyte® polishing process for 30 min. In addition, the influence of the process parameters voltage and the anodic time T2 during the treatment on the resulting surface quality and the polishing efficiency was determined. In conclusion, the dry electro-chemical finishing process has shown great smoothing capabilities for titanium even with small, tapped holes. The Ra values were lowered significantly throughout all titanium samples after 30 min polishing time.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Tailoring selective laser melting process parameters for NiTi implants(Springer, 12/2012) Bormann, Therese; Schumacher, Ralf; Müller, Bert; Mertmann, Matthias; de Wild, MichaelComplex-shaped NiTi constructions become more and more essential for biomedical applications especially for dental or cranio-maxillofacial implants. The additive manufacturing method of selective laser melting allows realizing complex-shaped elements with predefined porosity and three-dimensional micro-architecture directly out of the design data. We demonstrate that the intentional modification of the applied energy during the SLM-process allows tailoring the transformation temperatures of NiTi entities within the entire construction. Differential scanning calorimetry, x-ray diffraction, and metallographic analysis were employed for the thermal and structural characterizations. In particular, the phase transformation temperatures, the related crystallographic phases, and the formed microstructures of SLM constructions were determined for a series of SLM-processing parameters. The SLM-NiTi exhibits pseudoelastic behavior. In this manner, the properties of NiTi implants can be tailored to build smart implants with pre-defined microarchitecture and advanced performance.01A - Beitrag in wissenschaftlicher Zeitschrift