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DDC: 530 × Subject: Microscopy ×

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    Effect of additives on MWCNT dispersion and electrical percolation in polyamide 12 composites
    (Melville, NY : AIP, 2017) Socher, Robert; Krause, Beate; Pötschke, Petra
    The aim of this study was to decrease the electrical percolation threshold of multiwalled carbon nanotubes (MWCNTs) in a polyamide 12 matrix by the use of additives. Different kinds of additives were selected which either interact with the π-system of the MWCNTs (imidazolium based ionic liquid (IL) and perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA)) or improve the MWCNT wettability (cyclic butylene terephthalate, CBT). The composites were melt mixed using a DACA microcompounder. The electrical percolation threshold for PA12/MWCNT without additives, measured on compression molded plates, was found between 2.0 and 2.25 wt%. With all used additives, a significant reduction of the electrical percolation threshold could be achieved. Whereas the addition of IL and CBT resulted in MWCNT percolation at around 1.0 wt%, a slightly higher percolation threshold between 1.0 and 1.5 wt% was found for PTCDA as an additive. Interestingly, the electrical resistivity at higher loadings was decreased by nearly two decades when using CBT and one decade after application of PTCDA, whereas IL did not contribute to lower values in this range. In all cases macrodispersion as assessed by light microscopy was not improved and even worse as compared to non-modified composites. In summary, the results illustrate that these kinds of additives are able to improve the performance of PA12 based MWCNT nanocomposites.
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    High-fidelity multimode fibre-based endoscopy for deep brain in vivo imaging
    (London : Nature Publishing Group, 2018) Turtaev, Sergey; Leite, Ivo T.; Altwegg-Boussac, Tristan; Pakan, Janelle M. P.; Rochefort, Nathalie L.; Čižmár, Tomáš
    Progress in neuroscience relies on new techniques for investigating the complex dynamics of neuronal networks. An ongoing challenge is to achieve minimally invasive and high-resolution observations of neuronal activity in vivo inside deep brain areas. Recently introduced methods for holographic control of light propagation in complex media enable the use of a hair-thin multimode optical fibre as an ultranarrow imaging tool. Compared to endoscopes based on graded-index lenses or fibre bundles, this new approach offers a footprint reduction exceeding an order of magnitude, combined with a significant enhancement in resolution. We designed a compact and high-speed system for fluorescent imaging at the tip of a fibre, achieving a resolution of 1.18 ± 0.04 µm across a 50-µm field of view, yielding 7-kilopixel images at a rate of 3.5 frames/s. Furthermore, we demonstrate in vivo observations of cell bodies and processes of inhibitory neurons within deep layers of the visual cortex and hippocampus of anaesthetised mice. This study paves the way for modern microscopy to be applied deep inside tissues of living animal models while exerting a minimal impact on their structural and functional properties.