Fabrication of multifunctional titanium surfaces by producing hierarchical surface patterns using laser based ablation methods

Textured implant surfaces with micrometer and sub-micrometer features can improve contact properties like cell adhesion and bacteria repellency. A critical point of these surfaces is their mechanical stability during implantation. Therefore, strategies capable to provide both biocompatibility for an improved implant healing and resistance to wear for protecting the functional surface are required. In this work, laser-based fabrication methods have been used to produce hierarchical patterns on titanium surfaces. Using Direct Laser Writing with a nanosecond pulsed laser, crater-like structures with a separation distance of 50 µm are produced on unpolished titanium surfaces. Directly on this texture, a hole-like pattern with 5 µm spatial period is generated using Direct Laser Interference Patterning with picosecond pulses. While the smaller features should reduce the bacterial adhesion, the larger geometry was designed to protect the smaller features from wear. On the multifunctional surface, the adherence of E. Coli bacteria is reduced by 30% compared to the untreated reference. In addition, wear test performed on the multiple-scale patterns demonstrated the possibility to protect the smaller features by the larger craters. Also, the influence of the laser treatment on the growth of a titanium oxide layer was evaluated using Energy Dispersive X-Ray Spectroscopy analysis. © 2019, The Author(s)

Critical steps towards e-Governance: a case study analysis

The purpose of this paper is to make a further contribution to the theory and to the understanding of e-Governance. In doing so, the paper proceeds by an in-depth analysis of three cases, which, we think, are particularly illustrative of the three main dimensions – i.e., e-Service-Delivery, e-Regulation and e-Policy-Making – of evolving e-Governance practice and theory. By analysing the cases from a comprehensive theoretical framework, we will show how information and communication technology (ICT) impacts the transformation of the State

Friedliche Revolution in Sachsen: Das Ende der DDR und die Wiedergründung des Freistaates

Es geht um die Friedliche Revolution in Sachsen, das Ende der DDR und die Wiedergründung des Freistaates Sachsen

Targeting new ways for large-scale, high-speed surface functionalization using direct laser interference patterning in a roll-to-roll process

Direct Laser Interference Patterning (DLIP) is used to texture current collector foils in a roll-to-roll process using a high-power picosecond pulsed laser system operating at either fundamental wavelength of 1064 nm or 2nd harmonic of 532 nm. The raw beam having a diameter of 3 mm @ 1/e$^2$ is shaped into an elongated top-hat intensity profile using a diffractive so-called FBS®-L element and cylindrical telescopes. The shaped beam is split into its diffraction orders, where the two first orders are parallelized and guided into a galvanometer scanner. The deflected beams inside the scan head are recombined with an F-theta objective on the working position generating the interference pattern. The DLIP spot has a line-like interference pattern with about 15 μm spatial period. Laser fluences of up to 8 J cm$^{−2}$ were achieved using a maximum pulse energy of 0.6 mJ. Furthermore, an in-house built roll-to-roll machine was developed. Using this setup, aluminum and copper foil of 20 μm and 9 μm thickness, respectively, could be processed. Subsequently to current collector structuring coating of composite electrode material took place. In case of lithium nickel manganese cobalt oxide (NMC 622) cathode deposited onto textured aluminum current collector, an increased specific discharge capacity could be achieved at a C-rate of 1 °C. For the silicon/graphite anode material deposited onto textured copper current collector, an improved rate capability at all C-rates between C/10 and 5 °C was achieved. The rate capability was increased up to 100% compared to reference material. At C-rates between C/2 and 2 °C, the specific discharge capacity was increased to 200 mAh g$^{−1}$, while the reference electrodes with untextured current collector foils provided a specific discharge capacity of 100 mAh g$^{−1}$, showing the potential of the DLIP technology for cost-effective production of battery cells with increased cycle lifetime

Aspect ratio of nano/microstructures determines Staphylococcus aureus adhesion on PET and titanium surfaces

Aims: Joint infections cause premature implant failure. The avoidance of bacterial colonization of implant materials by modification of the material surface is therefore the focus of current research. In this in vitro study the complex interaction of periodic structures on PET and titanium surfaces on the adhesion of Staphylococcus aureus is analysed. Methods and Results: Using direct laser interference patterning as well as roll-to-roll hot embossing methods, structured periodic textures of different spatial distance were produced on surfaces and S. aureus were cultured for 24 h on these. The amount of adhering bacteria was quantified using fluorescence microscopy and the local adhesion behaviour was investigated using scanning electron microscopy. For PET structures, minimal bacterial adhesion was identified for an aspect ratio of about 0·02. On titanium structures, S. aureus adhesion was significantly decreased for profile heights of < 200 nm. Our results show a significantly decreased bacterial adhesion for structures with an aspect ratio range of 0·02 to 0·05. Conclusions: We show that structuring on surfaces can decrease the amount of S. aureus on titanium and PET as common implant materials. Significance and Impact of the Study: The study highlights the immense potential of applying specific structures to implant materials to prevent implant colonization with pathogen bacteria.Fil: Meinshausen, A. K.. Otto-von-Guericke-Universität Magdeburg; AlemaniaFil: Herbster, M.. Otto-von-Guericke-Universität Magdeburg; AlemaniaFil: Zwahr, C.. Technische Universität Dresden; AlemaniaFil: Soldera, Marcos Maximiliano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas. Universidad Nacional del Comahue. Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas; ArgentinaFil: Müller, A.. Otto-von-Guericke-Universität Magdeburg; AlemaniaFil: Halle, T.. Otto-von-Guericke-Universität Magdeburg; AlemaniaFil: Lasagni, A. F.. Technische Universität Dresden; AlemaniaFil: Bertrand, J.. Otto-von-Guericke-Universität Magdeburg; Alemani