Die Verwendung von „klassischen“ Naturfasern als Verstärkungskomponente in Kunststoffbauteilen ist durch ihr besonderes Eigenschaftsspektrum in Kombination mit wirtschaftlichen und ökologischen Vorteilen im gesamten Lebenszyklus begründet. Die Technologien zur Verarbeitung von Naturfasern zu Bauteilen wurden in den vergangenen Jahren kontinuierlich weiterentwickelt, wobei das Hauptaugenmerk auf der Optimierung von Material- und Verfahrensparametern bekannter Technologielösungen lag. Komplexe Anwendungen im Automobilbau erfordern allerdings eine ganzheitliche Betrachtung der gesamten Wertschöpfungskette von der Rohstoffbereitstellung über die Halbzeugfertigung bis hin zur Bauteilentwicklung und -herstellung. In diesem Zusammenhang weisen neuartige Faserverstärkungen aus Ganzpflanzenrohstoffen (GPR) gegenüber den konventionell aufgeschlossenen Naturfasern ein Potenzial für deutlich höhere Material- und Kosteneffizienz auf. Ziel dieser Arbeit ist die Bereitstellung einer werkstoffgerechten Auslegungsstrategie für eine neue durchgängige Prozesskette zur Herstellung von naturfaserverstärkten Bauteilen unter Einsatz von Ganzpflanzenrohstoffen. Am Beispiel der Flachspflanze werden dabei die verketteten Prozessstufen und die zugehörigen Schnittstellen entwickelt, charakterisiert und validiert. Darüber hinaus wird zur Umsetzung von Leichtbauanforderungen der Ansatz verfolgt, funktionale Zusammenhänge zwischen mechanischen Werkstoffkennwerten und lokaler Bauteildichte für eine belastungsgerechte Bauteilauslegung in Leichtbauweise zu erfassen. / The use of „classical“ natural fibres as reinforcing part for plastic components is caused by their particular property range in combination with economical and ecological advantages in the total life cycle. In recent years, technologies for the processing of natural fibres to components were continuously developed, focused on optimising material and process parameters of existing technology solutions. Certainly, complex applications in the automobile industry require an integrated consideration of the total value added chain from material supply to manufacturing of semi-finished products up to component development and production. In this regard novel fibre reinforcements made from whole plant materials possess potential for considerably higher material and cost efficiency compared to conventional natural fibres. The Intention of this work is to provide a material-specific dimensioning strategy for a new integrated process chain to produce natural fibre reinforced components by using raw materials made of the whole plant. Linked process steps and related interfaces were developed, characterised and validated by using the example of a flax plant. Moreover, the approach of realizing lightweight construction requirements is necessary in order to measure functional relations between material parameters and local density for the load-bearing part dimensioning in lightweight structure.

Navigationssysteme sollen nach Möglichkeit an jedem Ort und zu jeder Zeit funktionieren. Satellitennavigationssysteme unterliegen jedoch gewissen äußerlichen Einschränkungen, die die Positionierung erschweren oder erheblich verschlechtern. In einem urbanen Gebiet sind die Einflüsse auf die Positionierung mit Satellitensystemen durch die eingeschränkten räumlichen Verhältnisse besonders groß. Sowohl Mehrwege-Effekte wie auch die Verkleinerung des Sichtbereiches zu den Satelliten treten deutlich mehr auf. Mit der Verwendung von mehreren Satellitensystemen soll versucht werden, die Positionierung im urbanen Gebiet zu verbessern oder überhaupt erst möglich zu machen. Zur Untersuchung werden dafür die Eigenschaften Verfügbarkeit, Genauigkeit und Integrität für GPS, für GLONASS und für beide Systeme als ein Gesamtsystem genauer betrachtet.

The controlled positioning of DNA nanostructures on technologically relevant surfaces represents a major goal along the route toward the full-scale integration of DNA-based materials into nanoelectronic and sensor devices. Previous attempts to arrange DNA nanostructures into defined arrays mostly relied on top-down lithographic patterning techniques combined with chemical surface functionalization. Here we combine two bottom-up techniques for nanostructure fabrication, i.e., self-organized nanopattern formation and DNA origami self-assembly, in order to demonstrate the electrostatic self-alignment of DNA nanotubes on topographically patterned silicon surfaces. Self-organized nanoscale ripple patterns with periodicities ranging from 20 nm to 50 nm are fabricated by low-energy ion irradiation and serve as substrates for DNA origami adsorption. Electrostatic interactions with the charged surface oxide during adsorption direct the DNA origami nanotubes to the ripple valleys and align them parallel to the ripples. By optimizing the pattern dimensions and the Debye length of the adsorption buffer, we obtain an alignment yield of ~70%. Since this novel and versatile approach does not rely on any chemical functionalization of the surface or the DNA nanotubes, it can be applied to virtually any substrate material and any top-down or bottom-up nanopatterning technique. This technique thus may enable the wafer-scale fabrication of ordered arrays of functional DNA-based nanowires.

We developed a multiscale approach to explore the effective thermal conductivity of polycrystalline graphene sheets. By performing equilibrium molecular dynamics (EMD) simulations, the grain size effect on the thermal conductivity of ultra-fine grained polycrystalline graphene sheets is investigated. Our results reveal that the ultra-fine grained graphene structures have thermal conductivity one order of magnitude smaller than that of pristine graphene. Based on the information provided by the EMD simulations, we constructed finite element models of polycrystalline graphene sheets to probe the thermal conductivity of samples with larger grain sizes. Using the developed multiscale approach, we also investigated the effects of grain size distribution and thermal conductivity of grains on the effective thermal conductivity of polycrystalline graphene. The proposed multiscale approach on the basis of molecular dynamics and finite element methods could be used to evaluate the effective thermal conductivity of polycrystalline graphene and other 2D structures.

Polymeric vesicles or polymersomes are one of the supramolecular entities at the leading edge of synthetic biology. These small compartments have shown to be feasible candidates as nanoreactors, especially for enzymatic reactions. Once cross-linked and equipped with a pH sensitive material, the reaction can be switched off (pH 8) and on (pH 6) in accordance with the increased permeability of the polymersome membranes under acidic conditions. Thus cross-linked and pH sensitive polymersomes provide a basis for pH controlled enzymatic reactions where no integrated transmembrane protein is needed for regulating the uptake and release of educts and products in the polymersome lumen. This pH-tunable working tool was further used to investigate their use in sequential enzymatic reactions (glucose oxidase and myoglobin) where enzymes are loaded in one common polymersome or in two different polymersomes. Crossing membranes and overcoming the space distance between polymersomes were shown successfully, meaning that educts and products can be exchanged between enzyme compartments for successful enzymatic cascade reactions. Moreover the stabilizing effect of polymersomes is also observable by single enzymatic reactions as well as a sequence. This study is directed to establish robust and controllable polymersome nanoreactors for enzymatic reactions, describing a switch between an off (pH 8) and on (pH 6) state of polymersome membrane permeability with no transmembrane protein needed for transmembrane exchange.

We proposed and demonstrated the first account of large-area, semi-transparent, tandem photosensitive nanocrystal skins (PNSs) constructed on flexible substrates operating on the principle of photogenerated potential buildup, which avoid the need for applying an external bias and circumvent the currentmatching limitation between junctions. We successfully fabricated and operated the tandem PNSs composed of single monolayers of colloidal water-soluble CdTe and CdHgTe nanocrystals (NCs) in adjacent junctions on a Kapton polymer tape. Owing to the usage of a single NC layer in each junction, noise generation was significantly reduced while keeping the resulting PNS films considerably transparent. In each junction, photogenerated excitons are dissociated at the interface of the semi-transparent Al electrode and the NC layer, with holes migrating to the contact electrode and electrons trapped in the NCs. As a result, the tandem PNSs lead to an open-circuit photovoltage buildup equal to the sum of those of the two single junctions, exhibiting a total voltage buildup of 128.4 mV at an excitation intensity of 75.8 μW cm⁻² at 350 nm. Furthermore, we showed that these flexible PNSs could be bent over 3.5 mm radius of curvature and cut out in arbitrary shapes without damaging the operation of individual parts and without introducing any significant loss in the total sensitivity. These findings indicate that the NC skins are promising as building blocks to make low-cost, flexible, large-area UV/visible sensing platforms with highly efficient full-spectrum conversion.

In dieser Veröffentlichung wird ein methodischer Syntheseansatz aufgeführt, welcher in einem frühen Entwicklungsstadium zu einer ganzheitlichen Vorbetrachtung möglicher Konzeptvarianten befähigt. Hierfür werden zunächst parametrisierte Gleichungen zur Beschreibung von Flussfeldstrukturen und der Kanalquerschnittskonturen hergeleitet. Mithilfe dieser wird im Rahmen des Synthesealgorithmus die automatisierte Generierung und Berechnung möglicher Konzeptvarianten gewährleistet. Abschließend wird der Synthesealgorithmus im Rahmen einer beispielhaften Parameterstudie verdeutlicht. Hierfür wird ein Anforderungsprofil definiert. Die Ergebnisse der Parameterstudie werden aufgeführt und bewertet. Aus einer exemplarischen Nutzwertanalyse auf Basis ausgewählter Vergleichskriterien resultiert am Ende eine Bestvariante, welche für weitere Entwicklungsschritte herangezogen werden kann.

No description available.

Often synthetic graphene requires transfer onto an arbitrary substrate prior to use because the substrate it was originally synthesized on is inappropriate for either electrical measurement or characterization. While a variety of routes have been developed they are substrate dependant and often involve the use of harsh treatments. Here we present a facile and cheap route that can be applied to graphene over any substrate. This universal transfer route is based on a wet chemical reaction producing gaseous species which can intercalate between the substrate and the graphene and thus gently delaminate the two.

Here we propose, for the first time, a new and green ethanol-thermal reaction method to synthesize highquality and pure thiophene–sulfur doped reduced graphene oxide (rGO), which establishes an excellent platform for studying sulfur (S) doping effects on the physical/chemical properties of this material. We have quantitatively demonstrated that the conductivity enhancement of thiophene–S doped rGO is not only caused by the more effective reduction induced by S doping, but also by the doped S atoms, themselves. Furthermore, we demonstrate that the S doping is more effective in enhancing conductivity of rGO than nitrogen (N) doping due to its stronger electron donor ability. Finally, the dye-sensitized solar cell (DSCC) employing the S-doped rGO/TiO₂ photoanode exhibits much better performance than undoped rGO/TiO₂, N-doped rGO/TiO₂ and TiO₂ photoanodes. It therefore seems promising for thiophene–S doped rGO to be widely used in electronic and optoelectronic devices.