de Wild, Michael

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Michael
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de Wild, Michael

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  • Vorschaubild
    Publikation
    3D-printed LEGO®-inspired titanium scaffolds for patient-specific regenerative medicine
    (Elsevier, 2023) Lee, Seunghun S.; Du, Xiaoyu; Smit, Thijs; Bissacco, Elisa G.; Seiler, Daniel; de Wild, Michael; Ferguson, Stephen J. [in: Biomaterials Advances]
    Despite the recent advances in 3D-printing, it is often difficult to fabricate implants that optimally fit a defect size or shape. There are some approaches to resolve this issue, such as patient-specific implant/scaffold designs based on CT images of the patients, however, this process is labor-intensive and costly. Especially in developing countries, affordable treatment options are required, while still not excluding these patient groups from potential material and manufacturing advances. Here, a selective laser melting (SLM) 3D-printing strategy was used to fabricate a hierarchical, LEGO®-inspired Assemblable Titanium Scaffold (ATS) system, which can be manually assembled in any shape or size with ease. A surgeon can quickly create a scaffold that would fit to the defect right before the implantation during the surgery. Additionally, the direct inclusion of micro- and macroporous structures via 3D-printing, as well as a double acid-etched surface treatment (ST) in the ATS, ensure biocompatibility, sufficient nutrient flow, cell migration and enhanced osteogenesis. Three different structures were designed (non-porous:NP, semi-porous:SP, ultra-porous:UP), 3D-printed with the SLM technique and then surface treated for the ST groups. After analyzing characteristics of the ATS such as printing quality, surface roughness and interconnected porosity, mechanical testing and finite element analysis (FEA) demonstrated that individual and stacked ATS have sufficient mechanical properties to withstand loading in a physiological system. All ATS showed high cell viability, and the SP and UP groups demonstrated enhanced cell proliferation rates compared to the NP group. Furthermore, we also verified that cells were well-attached and spread on the porous structures and successful cell migration between the ATS units was seen in the case of assemblies. The UP and SP groups exhibited higher calcium deposition and RT-qPCR proved higher osteogenic gene expression compared to NP group. Finally, we demonstrate a number of possible medical applications that reveal the potential of the ATS through assembly. © 2023 The Authors
    01A - Beitrag in wissenschaftlicher Zeitschrift
  • Vorschaubild
    Publikation
    Immediate stabilization of pedicle screws
    (De Gruyter, 2023) de Wild, Michael; Zimmermann, Simon; Klein, Karina; Steffen, Thomas; Schlottig, Falko; Hasler, Carol; Rechenberg, Brigitte von [in: Current Directions in Biomedical Engineering]
    This study was designed as proof of principle and safety test of the novel technique, the Immediate Stabilization System (ISS). The technique is designed to immediately stabilize polymer-augmented pedicle screws (PAS) in deficient bone and avoid complications of loosening pedicle screws at the bone-screw interface, especially in osteoporotic patients. A polymer sleeve was designed as augmentation to improve screw anchorage after drilling the screw hole. By applying ultrasonic energy, the polymeric tube was molded into the pores of the host bone forming a strong and uniform bond with the adjacent bone. The original screw was then implanted into the denser bony environment leading to an enhanced immediate stability. The ISS-treated implants were compared to conventionally placed pedicle screws in ex-vivo cadaver bones (2 sheep spines, n = 6 implants per spine, total 12 screws) and in-vivo in a spinal sheep model (Swiss alpine sheep, n = 5, 4 implants per animal, total 20 screws). The primary stability of ISS-treated pedicle screws was increased in ex-vivo bone (+24% insertion torque (IT)) and in-vivo (+32.9% IT) in sheep spine. Removal torque (RT) was lower in the in PAS tested for 8 weeks in-vivo. The ISS technology demonstrated improved anchorage of pedicle screws in ex-vivo cadaver bones as well as in-vivo studies in sheep spine.
    01A - Beitrag in wissenschaftlicher Zeitschrift
  • Vorschaubild
    Publikation
    Three-dimensional printed hydroxyapatite bone substitutes designed by a novel periodic minimal surface algorithm are highly osteoconductive
    (Liebert, 2023) Maevskaia, Ekaterina; Khera, Nupur; Ghayor, Chafik; Bhattacharya, Indranil; Guerrero, Julien; Nicholls, Flora; Waldvogel, Christian; Bärtschi, Ralph; Fritschi, Lea; Salamon, Dániel; Özcan, Mutlu; Malgaroli, Patrick; Seiler, Daniel; de Wild, Michael; Weber, Franz E. [in: 3D Printing and Additive Manufacturing]
    01A - Beitrag in wissenschaftlicher Zeitschrift
  • Vorschaubild
    Publikation
    Topology-optimized patient-specific osteosynthesis plates
    (De Gruyter, 02.09.2022) Maintz, Michaela; Seiler, Daniel; Thieringer, Florian M.; de Wild, Michael [in: Current Directions in Biomedical Engineering]
    Patient-specific osteosynthesis plates can be used to reduce complications related to bone fracture treatment, such as infection, malocclusion and fatigue fractures of plates and screws. However, the implant design process is tedious. We propose a semi-automatic workflow to computationally design patient-specific titanium osteosynthesis plates for mandibular angle fractures. In this process, the plate stiffness is maximized while the mass is reduced. Two plate designs with different numbers of screw holes (implant #1 with four holes, implant #2 with eight holes) were generated with identical topology optimization settings and compared in a finite element model simulating various biomechanical masticatory loads. Differences in von Mises stresses in the implants and screws were observed. The load case of clenching the jaw on the opposite side of the fracture showed the highest stress distribution in implant #1 and higher peak stresses in implant #2. Stress concentrations were observed in sharp corners of the implant and could be reduced using local stress-based topology optimization. We conclude that the design process is an effective method to generate patientspecific implants.
    01A - Beitrag in wissenschaftlicher Zeitschrift
  • 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
    Publikation
    Investigating dry electro-chemical polishing of titanium structures
    (De Gruyter, 2021) Simeunovic, Sven; Jung, Christiane; Mory, Dominik; Seiler, Daniel; de Wild, Michael [in: Current Directions in Biomedical Engineering]
    With 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 Zeitschrift
  • Vorschaubild
    Publikation
    Rapid prototyped porous nickel–titanium scaffolds as bone substitutes
    (SAGE, 17.01.2014) Hoffmann, Waldemar; Bormann, Therese; Rossi, Antonella; Müller, Bert; Schumacher, Ralf; Martin, Ivan; de Wild, Michael; Wendt, David [in: Journal of Tissue Engineering]
    While calcium phosphate–based ceramics are currently the most widely used materials in bone repair, they generally lack tensile strength for initial load bearing. Bulk titanium is the gold standard of metallic implant materials, but does not match the mechanical properties of the surrounding bone, potentially leading to problems of fixation and bone resorption. As an alternative, nickel–titanium alloys possess a unique combination of mechanical properties including a relatively low elastic modulus, pseudoelasticity, and high damping capacity, matching the properties of bone better than any other metallic material. With the ultimate goal of fabricating porous implants for spinal, orthopedic and dental applications, nickel–titanium substrates were fabricated by means of selective laser melting. The response of human mesenchymal stromal cells to the nickel–titanium substrates was compared to mesenchymal stromal cells cultured on clinically used titanium. Selective laser melted titanium as well as surface-treated nickel–titanium and titanium served as controls. Mesenchymal stromal cells had similar proliferation rates when cultured on selective laser melted nickel–titanium, clinically used titanium, or controls. Osteogenic differentiation was similar for mesenchymal stromal cells cultured on the selected materials, as indicated by similar gene expression levels of bone sialoprotein and osteocalcin. Mesenchymal stromal cells seeded and cultured on porous three-dimensional selective laser melted nickel–titanium scaffolds homogeneously colonized the scaffold, and following osteogenic induction, filled the scaffold’s pore volume with extracellular matrix. The combination of bone-related mechanical properties of selective laser melted nickel–titanium with its cytocompatibility and support of osteogenic differentiation of mesenchymal stromal cells highlights its potential as a superior bone substitute as compared to clinically used titanium.
    01A - Beitrag in wissenschaftlicher Zeitschrift
  • Vorschaubild
    Publikation
    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: Chimia]
    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 Zeitschrift