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 Development of models for additively manufactured actuators using compliant Wren mechanism(Elsevier, 11/2021) Lennart, Rubbert; Schuler, Felix; Gayral, Thibault; de Wild, Michael; Renaud, PierreCompliant Wren mechanisms (CWM) constitute specific compliant structures of particular interest. Derived from Wren mechanisms, they can exhibit a large variety of motions, from quasi translation to quasi rotation. In this paper, the development of models for the analysis and synthesis of CWM is considered. A kinematic model is introduced first to assess all possible motions when used as an actuator. Then the static model and stress expressions are derived to help their design. These derivations are achieved for two types of geometries, corresponding to the geometries of interest. CWM are filigree structures, whose manufacturing is difficult to consider without additive manufacturing. A specific work on their production using selective laser melting (SLM) is then achieved to ensure the reliability of their production. As a proof of concept, a pneumatically actuated component is then developed and tested. It is composed of two CWM of different geometries. It offers the possibility to obtain translation and rotation using a single pressure input. The developed models are investigated using finite element models and experiments using additively manufactured structures.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Smart 4D-printed implants and instruments(De Gruyter, 09/2020) de Wild, Michael; Schuler, FelixSelective 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 ZeitschriftPublikation Pre-process calculation to optimize laser parameter in selective laser melting(2018) Matter, Nathalie; Schuler, Felix; Schumacher, Ralf; de Wild, Michael04B - Beitrag KonferenzschriftPublikation 3D-printed auxetic structures for bio-medical application(2018) Schuler, Felix; Renaud, Pascal; de Wild, Michael04B - Beitrag KonferenzschriftPublikation Osteoconductive Lattice Microarchitecture for Optimized Bone Regeneration(Mary Ann Liebert, 06/2018) de Wild, Michael; Ghayor, Chafik; Zimmermann, Simon; Rüegg, Jasmine; Nicholls, Flora; Schuler, Felix; Chen, Tse-Hsiang; Weber, Franz E.Selective laser melting (SLM) is one methodology to realize additive manufacturing and is mainly used to join metal powder in a layer-by-layer manner to produce a solid three-dimensional (3D) object. For bone tissue engineering purposes, scaffolds can readily be designed as 3D data model and realized with titanium known for its excellent osseointegration behavior. The microarchitecture, that is, design with submillimeter features, of additively manufactured scaffolds is in many cases a lattice structure. This study aimed to apply SLM that allows a high degree of microarchitectural freedom to generate lattice structures and to determine the optimal distance between rods and the optimal diameter of rods for osteoconduction (bone ingrowth into scaffolds) and bone regeneration. For the biological readout, diverse SLM-fabricated titanium implants were placed in the calvarium of rabbits and new bone formation and defect bridging were determined after 4 weeks of healing. The results from the middle section of the defects show that with a lattice microarchitecture, the optimal distance between titanium rods is around 0.8 mm and the optimal rod dimension is between 0.3 and 0.4 mm to optimize defect bridging and bone regeneration.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation A new approach to 3D-print of fine and complex structures(08/2018) Schuler, Felix06 - PräsentationPublikation Lattice Microarchitecture for Bone Tissue Engineering from Calcium Phosphate Compared to Titanium(Mary Ann Liebert, 10/2018) Chen, Tse-Hsiang; Ghayor, Chafik; Siegenthaler, Barbara; Schuler, Felix; Rüegg, Jasmine; de Wild, Michael; Weber, Franz E.Additive manufacturing of bone tissue engineering scaffolds will become a key element for personalized bone tissue engineering in the near future. Several additive manufacturing processes are based on extrusion where the deposition of the filament will result in a three-dimensional lattice structure. Recently, we studied diverse lattice structures for bone tissue engineering realized by laser sintering of titanium. In this work, we used lithography-based ceramic manufacturing of lattice structures to produce scaffolds from tricalcium phosphates (TCP) and compared them in vivo to congruent titanium scaffolds manufactured with the identical computer-aided design data to look for material-based differences in bony healing. The results show that, during a 4-week period in a noncritical-size defect in a rabbit calvarium, both scaffolds with the identical microarchitecture performed equally well in terms of bony regeneration and bony bridging of the defect. A significant increase in both parameters could only be achieved when the TCP-based scaffolds were doped with bone morphogenetic protein-2. In a critical-size defect in the calvarial bone of rabbits, however, the titanium scaffold performed significantly better than the TCP-based scaffold, most likely due to its higher mechanical stability. We conclude that titanium and TCP-based scaffolds of the same microarchitecture perform equally well in terms of bone regeneration, provided the microarchitecture meets the mechanical demand at the site of implantation.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Biopsy needle drive actuators made from NiTi(2017) Schuler, Felix; Renaud, Pascal; de Wild, Michael06 - Präsentation