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End date: 2020 × Start date: 2019 × End date: 2014 × Start date: 2013 × DDC: 530 × Has files: Yes × Type: Text × WGL Institute: INM ×

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Now showing 1 - 5 of 5
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    In situ measurements with CPC micro-actuators using SEM
    (Bellingham : SPIE, 2014) Kaasik, Friedrich; Must, Indrek; Lust, Enn; Jürgens, Meelis; Presser, Volker; Punning, Andres; Temmer, Rauno; Kiefer, Rudolf; Aabloo, Alvo
    Comparative measurements of carbon-polymer composite micro-actuators based on room temperature ionic liquid electrolyte were carried out in situ (1) in vacuum using a state-of-the-art scanning electron microscope, (2) in an oxygen-free atmosphere under ambient pressure, and (3) under ambient environment. The fabricated micro-actuators sustained their actuation performance in all three environments, revealing important implications regarding their humidity-dependence. SEM observations demonstrate high stroke actuation of a device with submillimeter length, which is the typical size range of actuators desirable for medical or lab-on-chip applications.
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    Adhesion behavior of polymer networks with tailored mechanical properties using spherical and flat contacts
    (Cambridge : Cambridge University Press, 2013) Lakhera, Nishant; Graucob, Annalena; Schneider, Andreas S.; Kroner, Elmar; Micciché, Maurizio; Arzt, Eduard; Frick, Carl P.
    Four acrylate-based networks were developed such that they possessed similar glass transition temperature (~-37 °C) but varied in material stiffness at room temperature by an order of magnitude (2-12 MPa). Thermo-mechanical and adhesion testing were performed to investigate the effect of elastic modulus on adhesion profiles of the developed samples. Adhesion experiments with a spherical probe revealed no dependency of the pull-off force on material modulus as predicted by the Johnson, Kendall, and Roberts theory. Results obtained using a flat probe showed that the pull-off force increases linearly with an increase in the material modulus, which matches very well with Kendall's theory.
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    Force microscopy of layering and friction in an ionic liquid
    (Bristol : IOP Publishing, 2014) Hoth, Judith; Hausen, Florian; Müser, Martin H.; Bennewitz, Roland
    The mechanical properties of the ionic liquid 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl) trifluorophosphate ([Py1,4][FAP]) in confinement between a SiOx and a Au(1 1 1) surface are investigated by means of atomic force microscopy (AFM) under electrochemical control. Up to 12 layers of ion pairs can be detected through force measurements while approaching the tip of the AFM to the surface. The particular shape of the force versus distance curve is explained by a model for the interaction between tip, gold surface and ionic liquid, which assumes an exponentially decaying oscillatory force originating from bulk liquid density correlations. Jumps in the tip–sample distance upon approach correspond to jumps of the compliant force sensor between branches of the oscillatory force curve. Frictional force between the laterally moving tip and the surface is detected only after partial penetration of the last double layer between tip and surface.
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    Self-assembly of gold nanoparticles at the oil-vapor interface: from mono- to multilayers
    (Washington D.C. : American Chemical Society, 2014) Born, Philip; Schön, Volker; Blum, Susanne; Gerstner, Dominik; Huber, Patrick; Kraus, Tobias
    Alkylthiol-coated gold nanoparticles spontaneously segregate from dispersion in toluene to the toluene-vapor interface. We show that surface tension drops during segregation with a rate that depends on particle concentration. Mono- and multilayers of particles form depending on particle concentration, time, and temperature. X-ray reflectometry indicates fast monolayer formation and slow multilayer formation. A model that combines diffusion-limited segregation driven by surface energy and heterogeneous agglomeration driven by dispersive van der Waals particle interactions is proposed to describe film formation.
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    Epidermal growth factor receptor subunit locations determined in hydrated cells with environmental scanning electron microscopy
    (London : Nature Publishing Group, 2013) Peckys, Diana B; Baudoin, Jean-Pierre; Eder, Magdalena; Werner, Ulf; de Jonge, Niels
    Imaging single epidermal growth factor receptors (EGFR) in intact cells is presently limited by the available microscopy methods. Environmental scanning electron microscopy (ESEM) of whole cells in hydrated state in combination with specific labeling with gold nanoparticles was used to localize activated EGFRs in the plasma membranes of COS7 and A549 cells. The use of a scanning transmission electron microscopy (STEM) detector yielded a spatial resolution of 3 nm, sufficient to identify the locations of individual EGFR dimer subunits. The sizes and distribution of dimers and higher order clusters of EGFRs were determined. The distance between labels bound to dimers amounted to 19 nm, consistent with a molecular model. A fraction of the EGFRs was found in higher order clusters with sizes ranging from 32–56 nm. ESEM can be used for quantitative whole cell screening studies of membrane receptors, and for the study of nanoparticle-cell interactions in general.