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DDC: 540 × Publisher: Weinheim : Wiley ×

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    Effect of Viscosity on Microswimmers: A Comparative Study
    (Weinheim : Wiley, 2021) Nsamela, Audrey; Sharan, Priyanka; Garcia‐Zintzun, Aidee; Heckel, Sandra; Chattopadhyay, Purnesh; Wang, Linlin; Wittmann, Martin; Gemming, Thomas; Saenz, James; Simmchen, Juliane
    Although many biological fluids like blood and mucus exhibit high viscosities, there are still many open questions concerning the swimming behavior of microswimmers in highly viscous media, limiting research to idealized laboratory conditions instead of application-oriented scenarios. Here, we analyze the effect of viscosity on the swimming speed and motion pattern of four kinds of microswimmers of different sizes which move by contrasting propulsion mechanisms: two biological swimmers (bovine sperm cells and Bacillus subtilis bacteria) which move by different bending patterns of their flagella and two artificial swimmers with catalytic propulsion mechanisms (alginate microtubes and Janus Pt@SiO2 spherical microparticles). Experiments consider two different media (glycerol and methylcellulose) with increasing viscosity, but also the impact of surface tension, catalyst activity and diffusion coefficients are discussed and evaluated.
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    Microscopic Softening Mechanisms of an Ionic Liquid Additive in an Electrically Conductive Carbon-Silicone Composite
    (Weinheim : Wiley, 2022) Zhang, Long; Schmidt, Dominik S.; González‐García, Lola; Kraus, Tobias
    The microstructural changes caused by the addition of the ionic liquid (IL) 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide to polydimethylsiloxane (PDMS) elastomer composites filled with carbon black (CB) are analyzed to explain the electrical, mechanical, rheological, and optical properties of IL-containing precursors and composites. Swelling experiments and optical analysis indicate a limited solubility of the IL in the PDMS matrix that reduces the cross-linking density of PDMS both globally and locally, which reduces the Young's moduli of the composites. A rheological analysis of the precursor mixture shows that the IL reduces the strength of carbon–carbon and carbon–PDMS interactions, thus lowering the filler–matrix coupling and increasing the elongation at break. Electromechanical testing reveals a combination of reversible and irreversible piezoresistive responses that is consistent with the presence of IL at microscopic carbon–carbon interfaces, where it enables re-established electrical connections after stress release but reduces the absolute conductivity.