Filters

2012 - 20174

More filters

20194
Reset filters

Settings

End date: 2019 × Start date: 2011 × Publisher: Milton Park : Taylor & Francis × WGL Institute: INM ×

Search Results

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    A study of the adhesive foot of the gecko: Translation of a publication by Franz Weitlaner
    (Milton Park : Taylor & Francis, 2015) Kroner, Elmar; Davis, Chelsea S.
    In recent years, hundreds of scientific studies have been published regarding gecko-inspired adhesives. The primary reason for this increasing interest lies in the unique properties which are combined in the adhesive system of the gecko: this natural system can quickly and repeatedly adhere to different surface chemistry and roughness without the use of adhesion-mediating fluids. Although these properties seem to be inconspicuous at first, there is no man-made system currently available which successfully combines all of these properties and competes with the biological adhesive system. However, there are many applications which may benefit from an artificial adhesion system inspired by geckos, ranging from climbing robots and handling systems to biomedical patches and household objects.
  • Thumbnail Image
    Item
    Adhesion of a rigid punch to a confined elastic layer revisited
    (Milton Park : Taylor & Francis, 2017) Hensel, René; McMeeking, Robert M.; Kossa, Attila
    The adhesion of a punch to a linear elastic, confined layer is investigated. Numerical analysis is performed to determine the equivalent elastic modulus in terms of layer confinement. The size of the layer relative to the punch radius and its Poisson’s ratio are found to affect the layer stiffness. The results reveal that the equivalent modulus of a highly confined layer depends on its Poisson’s ratio, whereas, in contrast, an unconfined layer is only sensitive to the extent of the elastic film. The solutions of the equivalent modulus obtained from the simulations are fitted by an analytical function that, subsequently, is utilized to deduce the energy release rate for detachment of the punch via linear elastic fracture mechanics. The energy release rate strongly varies with layer confinement. Regimes for stable and unstable crack growth can be identified that, in turn, are correlated to interfacial stress distributions to distinguish between different detachment mechanisms.
  • Thumbnail Image
    Item
    Estimating the modulatory effects of nanoparticles on neuronal circuits using computational upscaling
    (Milton Park : Taylor & Francis, 2013) Busse, Michael; Stevens, David; Kraegeloh, Annette; Cavelius, Christian; Vukelic, Mathias; Arzt, Eduard; Strauss, Daniel J.
    Background: Beside the promising application potential of nanotechnologies in engineering, the use of nanomaterials in medicine is growing. New therapies employing innovative nanocarrier systems to increase specificity and efficacy of drug delivery schemes are already in clinical trials. However the influence of the nanoparticles themselves is still unknown in medical applications, especially for complex interactions in neural systems. The aim of this study was to investigate in vitro effects of coated silver nanoparticles (cAgNP) on the excitability of single neuronal cells and to integrate those findings into an in silico model to predict possible effects on neuronal circuits. Methods: We first performed patch clamp measurements to investigate the effects of nanosized silver particles, surrounded by an organic coating, on excitability of single cells. We then determined which parameters were altered by exposure to those nanoparticles using the Hodgkin–Huxley model of the sodium current. As a third step, we integrated those findings into a well-defined neuronal circuit of thalamocortical interactions to predict possible changes in network signaling due to the applied cAgNP, in silico. Results: We observed rapid suppression of sodium currents after exposure to cAgNP in our in vitro recordings. In numerical simulations of sodium currents we identified the parameters likely affected by cAgNP. We then examined the effects of such changes on the activity of networks. In silico network modeling indicated effects of local cAgNP application on firing patterns in all neurons in the circuit. Conclusion: Our sodium current simulation shows that suppression of sodium currents by cAgNP results primarily by a reduction in the amplitude of the current. The network simulation shows that locally cAgNP-induced changes result in changes in network activity in the entire network, indicating that local application of cAgNP may influence the activity throughout the network.
  • Thumbnail Image
    Item
    Discharge during detachment of micro-structured PDMS sheds light on the role of electrostatics in adhesion
    (Milton Park : Taylor & Francis, 2012) Brörmann, Katrin; Burger, Karin; Jagota, Anand; Bennewitz, Roland
    Light emission due to discharge in air is detected during and after the detachment of microstructured PDMS samples from glass surfaces, showing contact charging of the surfaces. The light emission provides information about the detachment process, like the velocity of the peeling front, which is difficult to obtain otherwise. While the work of separation exhibits the dependence on pulling velocity typically found for viscoelastic materials, the emission intensity exhibits almost no velocity dependence. We present a model for the rate-dependent contribution of a mosaic of contact charges to the work of separation. Also, the work of separation increases as expected with increasing aspect ratio of the microstructure, while the emission intensity shows a maximum for intermediate structures. Based on their different dependencies and on an upper-bound estimate of the energy emitted as light, we conclude that for the given system the contribution of electrostatic attraction to the work of separation is minor.