Simon Scherrer


Last Name

Scherrer

First Name

Simon

ORCID

0000-0001-5479-8765

Organisational unit

09455 - Isa, Lucio / Isa, Lucio

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2024 - 20253
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Publications 1 - 3 of 3
  • Electromechanical properties of uniaxial polar ionic plastic crystal [(C₂H₅)₄N][FeBrCl₃]
    Item type: Journal Article
    Walker, Julian; Sodahl, Elin Dypvik; Scherrer, Simon; et al. (2024)
    Journal of Physics: Energy
    Ferroelectric plastic crystals are an emerging class of materials that combine room temperature ferroelectricity and piezoelectricity with a high temperature plastic mesophase prior to melting. These materials offer possibilities for accessing different property parameter spaces from the state-of-the-art metal oxide and polymer ferroelectrics. Tetraethylammonium bromotrichloroferrite, [(C₂H₅)₄N][FeBrCl₃], has a unipolar wurtzite-like structure and thus may have potential for small but stable piezoelectric coefficients like the iso-symmetrical AlN. In this study, density functional theory was used to compute elastic compliance, piezoelectric coefficients, and dielectric constant values. Single crystals grown from aqueous solutions were evaluated via single crystal synchrotron x-ray diffraction, impedance spectroscopy and high and weak-field electromechanical characterization. Diffraction studies revealed that the anion tetrahedra orientated preferentially so that the Br⁻ ion had a 30% alignment with the polarization vector. Electromechanical measurements found piezoelectric coefficients in the 5–9 pC N⁻¹ and pm V⁻¹ range. The piezoelectric coefficient (d33) was most stable with 3.4% variation between 0.4 and 90 Hz and 0.5 and 3 V. Additional piezoelectric stability measurements were made as a function of DC bias field and temperature. Impedance measurements indicate contributions from either intrinsic effects unique to ionic plastic crystals, such as molecular rotation, or the extrinsic effect of electrode interfaces, both of which can play a role in the electromechanical response of the materials. The results show that [(C₂H₅)₄N][FeBrCl₃] has potential as a small signal piezoelectric that has a softer elastic moduli than AlN but a stiffer moduli than polyvinylidene fluoride, and thus occupies a unique parameter space.
  • Toward Global Latency Transparency
    Item type: Conference Paper
    Krähenbühl, Cyrill; Tabaeiaghdaei, Seyedali; Scherrer, Simon; et al. (2024)
    2024 IFIP Networking Conference (IFIP Networking)
    A recent advance in networking is the deployment of path-aware multipath network architectures, where network endpoints are given multiple network paths to send their data on. In this work, we tackle the challenge of selecting paths for latency-sensitive applications. Even today's path-aware networks, which are much smaller than the current Internet, already offer dozens and in several cases over a hundred paths to a given destination, making it impractical to measure all path latencies to find the lowest latency path. Furthermore, for short flows, performing latency measurements may not provide benefits as the flow may finish before completing the measurements. To overcome these issues, we argue that endpoints should be provided with a latency estimate before sending any packets, enabling latency-aware path choice for the first packet sent. As we cannot predict the end-to-end latency due to dynamically changing queuing delays, we measure and disseminate the propagation latency, enabling novel use cases and solving concrete problems in current network protocols. We present the Global Latency Information Dissemination System (GLIDS), which is a step toward global latency transparency through the dissemination of propagation latency information.
  • Characterizing sliding and rolling contacts between single particles
    Item type: Journal Article
    Scherrer, Simon; Ramakrishna, Shivaprakash Narve; Niggel, Vincent; et al. (2025)
    Proceedings of the National Academy of Sciences of the United States of America
    Contacts between particles in dense, sheared suspensions are believed to underpin much of their rheology. Roughness and adhesion are known to constrain the relative motion of particles, and thus globally affect the shear response, but an experimental description of how they microscopically influence the transmission of forces and relative displacements within contacts is lacking. Here, we show that an innovative colloidal-probe atomic force microscopy technique allows the simultaneous measurement of normal and tangential forces exchanged between tailored surfaces and microparticles while tracking their relative sliding and rolling, unlocking the direct measurement of coefficients of rolling friction, as well as of sliding friction. We demonstrate that, in the presence of sufficient traction, particles spontaneously roll, reducing dissipation and promoting longer-lasting contacts. Conversely, when rolling is prevented, friction is greatly enhanced for rough and adhesive surfaces, while smooth particles coated by polymer brushes maintain well-lubricated contacts. We find that surface roughness induces rolling due to load-dependent asperity interlocking, leading to large off-axis particle rotations. In contrast, smooth, adhesive surfaces promote rolling along the principal axis of motion. Our results offer direct values of friction coefficients for numerical studies and an interpretation of the onset of discontinuous shear thickening based on them, opening up ways to tailor rheology via contact engineering.
Publications 1 - 3 of 3