Friction anisotropy is an important property of many surfaces that usually facilitate the generation of motion in a preferred direction. Such surfaces are very common in biological systems and have been the templates for various bio-inspired materials with similar tribological properties. So far friction anisotropy is considered to be the result of an asymmetric arrangement of surface nano- and microstructures. However, here we show by using bio-inspired sawtooth-structured surfaces that the anisotropic friction properties are not only controlled by an asymmetric surface topography, but also by the ratio of the sample–substrate stiffness, the aspect ratio of surface structures, and by the substrate roughness. Systematically modifying these parameters, we were able to demonstrate a broad range of friction anisotropies, and for specific sample–substrate combinations even an inversion of the anisotropy. This result highlights the complex interrelation between the different material and topographical parameters on friction properties and sheds new light on the conventional design paradigm of tribological systems. Finally, this result is also of great importance for understanding functional principles of biological materials and surfaces, as such inversion of friction anisotropy may correlate with gait pattern and walking behaviour in climbing animals, which in turn may be used in robotic applications.
Many solutions for getting grip on varying substrates exist in nature and in technical applications, but they fail on substrate geometries they are not specifically designed for. A novel passive load‐dependent system is developed that creates high friction forces on a large variety of substrates: the granular media friction pad. With an elastic membrane encasing granular media, it reversibly undergoes the jamming transition only by varying the normal load. Here, the friction performance on different substrates is shown and the underlying physical mechanisms in a numerical simulation are investigated.
Presenting your research in the proper light can be exceptionally challenging. Meanwhile, dome illumination systems became a standard for micro-and macrophotography in taxonomy, morphology, systematics and especially important in natural history collections. However, proper illumination systems are either expensive and/or laborious to use. Nowadays, 3D-printing technology revolutionizes lab-life and will soon find its way into most people's everyday life. Consequently, fused deposition modelling printers become more and more available, with online services offering personalized printing options. Here, we present a 3D-printed, scalable, low-cost and modular LED illumination dome system for scientific micro-and macrophotography. We provide stereolithography ('.stl') files and print settings, as well as a complete list of necessary components required for the construction of three differently sized domes. Additionally, we included an optional iris diaphragm and a sliding table, to arrange the object of desire inside the dome. The dome can be easily scaled and modified by adding customized parts, allowing you to always present your research object in the best light.
Typical soil-structure interfaces exhibit a response that is independent of loading direction due to the symmetry of the surfaces' profile. This study presents results from an experimental investigation on the response of sand specimens sheared against three types of surfaces bio-inspired from the skin along the underside of snakes. The results of shear box interface shear tests indicate that all three surfaces exhibit significant anisotropy in response in terms of mobilized shear resistances and corresponding volumetric changes. A discussion on the practical implications and potential benefits of implementation of the snake skin-inspired surfaces in engineering design is provided.
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