INMdok (Leibniz Institute for New Materials)
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On the geometric stability of an inorganic nanowire and an organic ligand shell
Get PDFThe break-up of a nanowire with an organic ligand shell into discrete droplets is analysed in terms of the Rayleigh-Plateau instability. Explicit account is taken of the effect of the organic ligand shell upon the energetics and kinetics of surface diffusion in the wire. Both an initial perturbation analysis and a full numerical analysis of the evolution in wire morphology are conducted, and the governing non-dimensional groups are identified. The perturbation analysis is remarkably accurate in obtaining the main features of the instability, including the pinch-off time and the resulting diameter of the droplets. It is conjectured that the surface energy of the wire and surrounding organic shell depends upon both the mean and deviatoric invariants of the curvature tensor. Such a behaviour allows for the possibility of a stable nanowire such that the Rayleigh-Plateau instability is not energetically favourable. A stability map illustrates this. Maps are also constructed for the final droplet size and pinch-off time as a function of two non-dimensional groups that characterise the energetics and kinetics of diffusion in the presence of the organic shell. These maps can guide future experimental activity on the stabilisation of nanowires by organic ligand shells
Optoregulation of collagen biosynthesis and remodeling in collagen associated diseases
Get PDFDiese Version des Dokuments ist nicht mehr aktuell. Bitte verwenden Sie folgende aktuelle Version: https://doi.org/10.57954/opus-54
Molekulare Schmierung unpolarer und ionischer Schmiermittel im nanoskaligen Spalt
Get PDFIn dieser Arbeit wurde mittels dynamischer Scherkraftmikroskopie der Einfluss chemischer und physikalischer Oberflächeneigenschaften auf die Struktur und die Schereigenschaften unpolarer und ionischen Flüssigkeiten im nanoskaligen Spalt untersucht. Es konnte gezeigt werden, dass die Schereigenschaften im nanoskaligen Spalt entscheidend von der Ausprägung und der Struktur der molekularen Lagenbildung beeinflusst werden. Diese hängt wiederum von den chemischen und physikalischen Eigenschaften der einschnürenden Oberflächen ab. Die Affinität der Flüssigkeitsmoleküle zu den Oberflächen bestimmt dabei die Orientierung der Moleküle im Spalt sowie die Anzahl der zu beobachteten Lagen. Molekulare Lagenbildung wurde in allen untersuchten Flüssigkeiten und auf allen untersuchten Substraten beobachtet. Dabei handelte es sich sowohl um einfache als auch um technisch relevante Substrate und Flüssigkeiten. Auch konnte gezeigt werden, dass Schersteifigkeit und -Dämpfung im nanoskaligen Spalt nicht von der Normalkraft sondern nur von der Anzahl der molekularen Lagen im Spalt abhängen. Mittels elektrochemischer Methoden war es möglich die molekulare Lagenbildung sowie die Schereigenschaften ionischer Flüssigkeiten zu kontrollieren. Die Wahl geeigneter Materialien, Beschichtungen oder das Anlegen von elektrischen Potenzialen ermöglicht damit die aktive Kontrolle der molekularen Struktur und der Schereigenschaften im nanoskaligen Spalt.In this work, dynamic shear force microscopy was employed to study the influence of physical and chemical surface properties upon the structure and the shear properties of nanometer confined liquids. It could be shown that molecular layering strongly influences the shear properties in nanometer confinement. The structure and magnitude of the molecular layers in turn depend on the physico-chemical properties of the confining surfaces. The affinity of the confined molecules to the surfaces defines the orientation of the molecules in the gap and the number of observable molecular layers. Molecular layering was observed in all investigated liquids and on all substrates. Both simple as well as technical liquids and substrates were used. It could also be shown that shear stiffness and shear damping in confinement depend only on the number of molecular layers between the confining walls and not on the applied normal load. Using electrochemical methods, it was possible to control molecular layering as well as the shear properties of ionic liquids. The choice of appropriate materials, coatings or the application of electrical potentials allow the active control of molecular structure and shear properties in nanometer confinement
Visualisation of HER2 homodimers in single cells from HER2 overexpressing primary formalin fixed paraffin embedded tumour tissue
Get PDFHER2 is considered as one of the most important, predictive biomarkers in oncology. The diagnosis of HER2 positive cancer types such as breast- and gastric cancer is usually based on immunohistochemical HER2 staining of tumour tissue. However, the current immunohistochemical methods do not provide localized information about HER2’s functional state. In order to generate signals leading to cell growth and proliferation, the receptor spontaneously forms homodimers, a process that can differ between individual cancer cells
Influence of Water on Tribolayer Growth When Lubricating Steel with a Fluorinated Phosphonium Dicyanamide Ionic Liquid
Get PDFThis work aims to elucidate the role of environmental humidity on the tribological behavior of steel surfaces lubricated with an ionic liquid comprised of a fluorinated phosphonium cation—tributyl-3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluoro-octyl-phosphonium—and a dicyanamide anion (i.e. N(CN)2−). Ball-on-disk tribotests were carried out at room temperature and at various levels of relative humidity (RH). Water was found to be required to promote the formation of a tribofilm over the contact area. The reaction layer exhibited a patchy morphology, which resembles that observed formed with conventional antiwear additives such as ZnDTP. A surface-chemical analysis of the tribofilm indicated that the tribofilm is composed of fluorides, oxides, and phosphates, pointing to a stress-induced degradation of the ions and corrosion of the sliding counterparts, which is enabled by the presence of water at the sliding interface
Laser sintering of gravure printed indium tin oxide films on polyethylene terephthalate for flexible electronics
Get PDFTin doped indium oxide (ITO) thin films provide excellent transparency and conductivity for electrodes in displays and photovoltaic systems. Current advances in producing printable ITO inks are reducing the volume of wasted indium during thin film patterning. However, their applicability to flexible electronics is hindered by the need for high temperature processing that results in damage to conventional polymer substrates. Here, we detail the conditions under which laser heating can be used as a replacement for oven and furnace treatments. Measurements of the optical properties of both the printed ITO film and the polymer substrate (polyethylene terephthalate, PET) identify that in the 1.5–2.0 μm wavelength band there is absorption in the ITO film but good transparency in PET. Hence, laser light that is not absorbed in the film does not go on to add a deleterious energy loading to the substrate. Localization of the energy deposition in the film is further enhanced by using ultrashort laser pulses (~1 ps) thus limiting heat flow during the interaction. Under these conditions, laser processing of the printed ITO films results in an improvement of the conductivity without damage to the PET
Nanostrukturierte Schichten für Photovoltaik und Elektronik aus kontrollierter Partikelabscheidung : NanoSpekt Abschlussbericht : 2013-2019
Get PDFDas Ziel des Projektes "NanoSpekt" war es, neue elektronische Materialien auf Basis von Partikelanordnungen zu entwickeln und sie als Schichten mit wohldefinierter Mikrostruktur für transparente und flexible Elektronik abzuscheiden. Das Projekt deckte unterschiedliche Stufen der Materialherstellung ab, von der Synthese von Nanopartikeln (NP) bis zur Charakterisierung der ferten Schichten. [...
Bioinspired Liposomes for Oral Delivery of Colistin to Combat Intracellular Infections by Salmonella enterica
Get PDFAbstract Bacterial invasion into eukaryotic cells and the establishment of intracellular infection has proven to be an effective means of resisting antibiotic action, as anti-infective agents commonly exhibit a poor permeability across the host cell membrane. Encapsulation of anti-infectives into nanoscaled delivery systems, such as liposomes, is shown to result in an enhancement of intracellular delivery. The aim of the current work is, therefore, to formulate colistin, a poorly permeable anti-infective, into liposomes suitable for oral delivery, and to functionalize these carriers with a bacteria-derived invasive moiety to enhance their intracellular delivery. Different combinations of phospholipids and cholesterol are explored to optimize liposomal drug encapsulation and stability in biorelevant media. These liposomes are then surface-functionalized with extracellular adherence protein (Eap), derived from Staphylococcus aureus. Treatment of HEp-2 and Caco-2 cells infected with Salmonella enterica using colistin-containing, Eap-functionalized liposomes resulted in a significant reduction of intracellular bacteria, in comparison to treatment with nonfunctionalized liposomes as well as colistin alone. This indicates that such bio-invasive carriers are able to facilitate intracellular delivery of colistin, as necessary for intracellular anti-infective activity. The developed Eap-functionalized liposomes, therefore, present a promising strategy for improving the therapy of intracellular infections
Strength of bacterial adhesion on nanostructured surfaces quantified by substrate morphometry
Get PDFMicrobial adhesion and the subsequent formation of resilient biofilms at surfaces are decisively influenced by substrate properties, such as the topography. To date, studies that quantitatively link surface topography and bacterial adhesion are scarce, as both are not straightforward to quantify. To fill this gap, surface morphometry combined with single-cell force spectroscopy was performed on surfaces with irregular topographies on the nano-scale. As surfaces, hydrophobized silicon wafers were used that were etched to exhibit surface structures in the same size range as the bacterial cell wall molecules. The surface structures were characterized by a detailed morphometric analysis based on Minkowski functionals revealing both qualitatively similar features and quantitatively different extensions. We find that as the size of the nanostructures increases, the adhesion forces decrease in a way that can be quantified by the area of the surface that is available for the tethering of cell wall molecules. In addition, we observe a bactericidal effect, which is more pronounced on substrates with taller structures but does not influence adhesion. Our results can be used for a targeted development of 3D-structured materials for/against bio-adhesion. Moreover, the morphometric analysis can serve as a future gold standard for characterizing a broad spectrum of material structures
Switchable double-sided micropatterned adhesives for selective fixation and detachment
Get PDFMicropatterned dry adhesives are promising candidates for the development of innovative adhesive platforms. Their reversible adhesion to various materials and surfaces has been reported over more than a decade. Switching between a strong and a weak adhesive state can be introduced by elastic buckling instabilities of the microstructure. In this work, we report on novel adhesive pads that exhibit micropatterned pillars on both sides. In double-sided PDMS micropatterns, the dimensions of the pillar structures were tuned by modulating the critical force for buckling during compressive loading. In this way, selective detachment of glass substrates was induced from one side of the pad. Our results indicate a significant switching efficiency of up to 83% between the strong and weak adhesive state. The new structures have high potential for emerging applications where temporary, double-sided fixations in combination with a predetermined detachment location are required