INMdok (Leibniz Institute for New Materials)
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Self-Healable and Recyclable Tactile Force Sensors with Post-Tunable Sensitivity
Get PDFAbstract It is challenging to post-tune the sensitivity of a tactile force sensor. Herein, a facile method is reported to tailor the sensing properties of conductive polymer composites by utilizing the liquid-like property of dynamic polymer matrix at low strain rates. The idea is demonstrated using dynamic polymer composites (CB/dPDMS) made via evaporation-induced gelation of the suspending toluene solution of carbon black (CB) and acid-catalyzed dynamic polydimethylsiloxane (dPDMS). The dPDMS matrices allow CB to redistribute to change the sensitivity of materials at the liquid-like state, but exhibit typical solid-like behavior and thus can be used as strain sensors at normal strain rates. It is shown that the gauge factor of the polymer composites can be easily post-tuned from 1.4 to 51.5. In addition, the dynamic polymer matrices also endow the composites with interesting self-healing ability and recyclability. Therefore, it is envisioned that this method can be useful in the design of various novel tactile sensing materials for many applications
Dendrites as climbing dislocations in ceramic electrolytes: Initiation of growth
Get PDFWe idealise dendrite growth in a ceramic electrolyte by climb of a thick edge dislocation. Growth of the dendrite occurs at constant chemical potential of Li+ at the dendrite tip: the free-energy to fracture and wedge open the electrolyte is provided by the flux of Li+ from the electrolyte into the dendrite tip. This free-energy is dependent on the Li+ overpotential at the dendrite tip and is thereby related to the imposed charging current density. The predicted critical current density agrees with measurements for Li/LLZO/Li symmetric cells: the critical current density decreases with increasing initial length of the dendrite and with increasing electrode/electrolyte interfacial ionic resistance. The simulations also reveal that a void on the cathode/electrolyte interface locally enhances the Li+ overpotential and significantly reduces the critical current density for the initiation of dendrite growth
Visualisation of Open Access publications in the reference tools of a library - visOA
Get PDFZiel des geförderten Projekts Sichtbarmachung von Open-Access-Publikationen in den Nachweisinstrumenten einer Bibliothek - visOA - war es, die Sichtbarkeit von Open-Access-Publikationen zu verbessern, indem sie deutlich gekennzeichnet und hervorgehoben werden. Außerdem sollte durch die Programmierung einer virtuellen Zeitschriftenauslage für Open-Access-Journale ein neues Angebot geschaffen werden, das allen Nutzern direkten und ungehinderten Zugang zu Open-Access-Publikationen bietet. Durch die stärkere Sichtbarmachung von Open-Access-Publikationen soll die Wahrnehmung und Bekanntheit des Themas Open Access bei Publizierenden und Rezipienten erhöht werden (und dadurch eventuell auch die Etablierung von Open Access beschleunigt werden.) Die Wirksamkeit der Maßnahmen sollte durch begleitende Forschung überprüft werden
Electronic multiscale hybrid materials: Sinter-free inks, printed transparent grids, and soft devices
Get PDFHybrid electronic materials combine the excellent electronic properties of metals and semiconductors with the mechanical flexibility, ease of processing, and optical transparency of polymers. This talk will discuss hybrids that combine organic and inorganic components at different scales. Metallic and semiconductor nanoparticle cores are coated with conductive polymer shells to create “hybrid inks” that can be inkjet-printed and form conductive leads without any sintering step. Transparent electrodes are printed using ultrathin metal nanowires with core diameters below 2 nm. The chemically synthesized wires spontaneously form percolating structures when patterned with a soft stamp; this rapidly yields optically transparent grid electrodes, even on demanding soft substrates. These new hybrid electronic materials enable the fabrication of soft electronics, including flexible sensors on polymer foils, radio-frequency identification (RFID) antennae on cardboard, and soft human–machine interfaces. Selected devices will be covered at the end of the talk
Elastohydrodynamic Dewetting of Thin Liquid Films: Elucidating Underwater Adhesion of Topographically Patterned Surfaces
Get PDFIn underwater adhesion of a topographically patterned surface with a very soft material such as human skin, the elastic deformation can be large enough to achieve solid-on-solid contact not only on top of the hills but also in the valleys of the substrate topography. In this context, we have studied the dynamics of dewetting of a thin liquid film confined between a rigid, periodic micropillar array and a soft, elastic sphere. In our experiments, we observed two very distinct dewetting morphologies. For large ratios of array period to micropillar height and width, the dewetted areas tend to have a diamond-like shape and expand with a rate similar to a flat, unpatterned substrate. When the array period is reduced, the morphology of the dry spot becomes irregular and its expansion rate is significantly reduced. We developed a fully coupled numerical model of the dewetting process that reproduces the key features observed in experiments. Moreover, we performed contact mechanics simulations to characterize the deformation of the elastomer and the shape of the dewetted area in a unit cell of the micropillar array
Correlative Fluorescence- and Electron Microscopy of Whole Breast Cancer Cells Reveals Different Distribution of ErbB2 Dependent on Underlying Actin
Get PDFEpidermal growth factor receptor 2 (ErbB2) is found overexpressed in several cancers, such as gastric, and breast cancer, and is, therefore, an important therapeutic target. ErbB2 plays a central role in cancer cell invasiveness, and is associated with cytoskeletal reorganization. In order to study the spatial correlation of single ErbB2 proteins and actin filaments, we applied correlative fluorescence microscopy (FM), and scanning transmission electron microscopy (STEM) to image specifically labeled SKBR3 breast cancer cells. The breast cancer cells were grown on microchips, transformed to express an actin-green fluorescent protein (GFP) fusion protein, and labeled with quantum dot (QD) nanoparticles attached to specific anti-ErbB2 Affibodies. FM was performed to identify cellular regions with spatially correlated actin and ErbB2 expression. For STEM of the intact plasma membrane of whole cells, the cells were fixed and covered with graphene. Spatial distribution patterns of ErbB2 in the actin rich ruffled membrane regions were examined, and compared to adjacent actin-low regions of the same cell, revealing an association of putative signaling active ErbB2 homodimers with actin-rich regions. ErbB2 homodimers were found absent from actin-low membrane regions, as well as after treatment of cells with Cytochalasin D, which breaks up larger actin filaments. In both latter data sets, a significant inter-label distance of 36 nm was identified, possibly indicating an indirect attachment to helical actin filaments via the formation of heterodimers of ErbB2 with epidermal growth factor receptor (EGFR). The possible attachment to actin filaments was further explored by identifying linear QD-chains in actin-rich regions, which also showed an inter-label distance of 36 nm
Structural and Chemical Hierarchy in Hydroxyapatite Coatings
Get PDFHydroxyapatite coatings need similarly shaped splats as building blocks and then a homogeneous microstructure to unravel the structural and chemical hierarchy for more refined improvements to implant surfaces. Coatings were thermally sprayed with differently sized powders (20–40, 40–63 and 63–80 µm) to produce flattened homogeneous splats. The surface was characterized for splat shape by profilometry and Atomic force microscopy (AFM), crystal size by AFM, crystal orientation by X-ray diffraction (XRD) and structural variations by XRD. Chemical composition was assessed by phase analysis, but variations in chemistry were detected by XRD and Raman spectroscopy. The resulting surface electrical potential was measured by Kelvin probe AFM. Five levels of structural hierarchy were suggested: the coating, the splat, oriented crystals, alternate layers of oxyapatite and hydroxyapatite (HAp) and the suggested anion orientation. Chemical hierarchy was present over a lower range of order for smaller splats. Coatings made from smaller splats exhibited a greater electrical potential, inferred to arise from oxyapatite, and supplemented by ordered OH− ions in a rehydroxylated surface layer. A model has been proposed to show the influence of structural hierarchy on the electrical surface potential. Structural hierarchy is proposed as a means to further refine the properties of implant surfaces
Switchable Underwater Adhesion by Deformable Cupped Microstructures
Get PDFAbstract Switchable underwater adhesion can be useful for numerous applications, but is extremely challenging due to the presence of water at the contact interface. Here, deformable cupped microstructures (diameter typically 100 µm, rim thickness 5 µm) are reported that can switch between high (≈1 MPa) and low (<0.2 MPa) adhesion strength by adjusting the retraction velocity from 100 to 0.1 µm s–1. The velocity at which the switch occurs is determined by specific design parameters of the cupped microstructure, such as the cup width and angle. The results are compared with theoretical estimates of water penetration into the contact zone and expansion of the cup during retraction. This work paves the way for controlling wet adhesion on demand and may inspire further applications in smart adhesives
Annual report 2019 / Leibniz Institute for New Materials
Get PDFVorwort:
Wir sind ein bisschen stolz: Erneut können wir auf ein sehr erfolgreiches Jahr am INM zurückblicken. Wieder haben unsere Publikationen einen neuen Höchststand erreicht, unsere Ergebnisse wurden in den führenden Journals unserer Fachgebiete veröffentlicht und die Einwerbung externer Mittel liegt über unseren Zielen. Dass unsere Spanne von Grundlagenforschungs bis hin zu Anwendungen reicht, konnten wir nachdrücklich belegen: Die 2019 ausgegründete INNOCISe GmbH wird unsere erfolgreiche Forschung im Bereich bioinspirierter Haftsysteme in innovative Lösungen für Anwendungen in den Bereichen Robotik, Handling und Automation umsetzen.
Wie geht es weiter? Zwei Zukunftsthemen haben wir für unser Institut identifiziert: biomedizinsche Materialien für die digitale Umgebung. Viele Anforderungen der Welt von morgen werden nur mit neuen Materiallösungen umzusetzen sein. Soeben beginnen die Renovierungsarbeiten für unseren Erweiterungsbau, den wir für unsere Zukunftsthemen herrichten. Außerdem gehen wir neue strategische Kooperationen mit Medizin und Informatik ein - denn Innovationen können nur gemeinsam gelingen.
Tauchen Sie mit uns ein in die spannend Welt moderner Materialforschung. Wir freuen uns, wenn Sie das INM auch in die Zkunft begleiten
Myxobacteria-Derived Outer Membrane Vesicles: Potential Applicability Against Intracellular Infections
Get PDFIn 2019, it was estimated that 2.5 million people die from lower tract respiratory infections annually. One of the main causes of these infections is Staphylococcus aureus, a bacterium that can invade and survive within mammalian cells. S. aureus intracellular infections are difficult to treat because several classes of antibiotics are unable to permeate through the cell wall and reach the pathogen. This condition increases the need for new therapeutic avenues, able to deliver antibiotics efficiently. In this work, we obtained outer membrane vesicles (OMVs) derived from the myxobacteria Cystobacter velatus strain Cbv34 and Cystobacter ferrugineus strain Cbfe23, that are naturally antimicrobial, to target intracellular infections, and investigated how they can affect the viability of epithelial and macrophage cell lines. We evaluated by cytometric bead array whether they induce the expression of proinflammatory cytokines in blood immune cells. Using confocal laser scanning microscopy and flow cytometry, we also investigated their interaction and uptake into mammalian cells. Finally, we studied the effect of OMVs on planktonic and intracellular S. aureus. We found that while Cbv34 OMVs were not cytotoxic to cells at any concentration tested, Cbfe23 OMVs affected the viability of macrophages, leading to a 50% decrease at a concentration of 125,000 OMVs/cell. We observed only little to moderate stimulation of release of TNF-alpha, IL-8, IL-6 and IL-1beta by both OMVs. Cbfe23 OMVs have better interaction with the cells than Cbv34 OMVs, being taken up faster by them, but both seem to remain mostly on the cell surface after 24 h of incubation. This, however, did not impair their bacteriostatic activity against intracellular S. aureus. In this study, we provide an important basis for implementing OMVs in the treatment of intracellular infections