Luisa Euler

This work investigates how unit-cell topology controls flexural-wave dispersion and finite-array attenuation in periodic acoustic-black-hole (ABH) plates. Six configurations are compared under identical material constants, lattice parameter, power-law profile, and residual thickness: a uniform reference plate, two isolated ABH inclusions with circular and y-elongated elliptical shapes, a crossed-strip ABH network, and two cross-connected inclusion–strip networks. The plate is modeled using Kirchhoff–Love theory with spatially varying thickness, and dispersion curves are computed with a finite-difference Bloch (FD–Bloch) formulation along the sampled Γ–X–M–Γ path. The numerical dispersion results are checked against a Gaussian-enriched Ritz method and, for the uniform plate, against the analytical folded dispersion relation. To connect the infinite-periodic predictions with practical attenuation, finite arrays are also analyzed through transmission maps and full-aperture transmission curves. The results show that isolated circular and elliptical ABHs mainly distort dispersion branches, produce partial directional stop behavior, and give only moderate forward-transmission reductions in finite arrays. By contrast, connected low-thickness ligaments strengthen modal coupling and generate wider stop intervals along the sampled path. The crossed-strip and cross-connected circular networks reduce the full-aperture transmission at their selected stop-band frequencies. The cross-connected y-elongated elliptical network gives the strongest response. These results show that ABH topology, and especially the connectivity and anisotropy of the thinned regions, is a decisive design parameter for directional attenuation in lightweight periodic plates.

Electrical stimulation can be used for the treatment of various nerve and muscle injuries as well as acute and chronic pain conditions. An electrical pulse is applied to a muscle or nerve to activate excitable tissue using internal or external electrodes with the aim of building muscle strength, artificially creating or supporting limb movement or reducing pain. Textile electrodes offer several advantages over conventionally used disposable surface electrodes: they are flexible and re-usable and they do not require hydrogels, thereby avoiding skin irritation and allergic reactions and enhancing user comfort. This article presents a literature review that assesses the state of research on textile electrode constructions. Based on the review, production approaches and designs are compared, methods for evaluating stimulation discomfort and pain are proposed and issues related to user compliance are discussed. The article concludes with suggestions for future work focused on investigating the impacts of textile-based electrode parameters on comfort, convenience and ease of use.

Textile electrodes, also called textrodes, for biosignal monitoring as well as electrostimulation are central for the emerging research field of smart textiles. However, so far, only the general suitability of textrodes for those areas was investigated, while the influencing parameters on the contact impedance related to the electrode construction and external factors remain rather unknown. Therefore, in this work, six different knitted electrodes, applied both wet and dry, were compared regarding the influence of specific knitting construction parameters on the three-electrode contact impedance measured on a human forearm. Additionally, the influence of applying pressure was investigated in a two-electrode setup using a water-based agar dummy. Further, simulation of an equivalent circuit was used for quantitative evaluation. Indications were found that the preferred electrode construction to achieve the lowest contact impedance includes a square shaped electrode, knitted with a high yarn density and, in the case of dry electrodes, an uneven surface topography consisting of loops, while in wet condition a smooth surface is favorable. Wet electrodes are showing a greatly reduced contact impedance and are therefore to be preferred over dry ones; however, opportunities are seen for improving the electrode performance of dry electrodes by applying pressure to the system, thereby avoiding disadvantages of wet electrodes with fluid administration, drying-out of the electrolyte, and discomfort arising from a “wet feeling”.