Regensburg 2019 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 34: New Methods and Developments III: Spectroscopy and Tribology
O 34.3: Vortrag
Dienstag, 2. April 2019, 14:30–14:45, H13
Nano-scale surface steps as the origin of friction anisotropy of snake scales — •Weibin Wu1, Shudong Yu2, Christian Greiner3, Guillaume Gomard1,2, and Hendrik Hölscher1 — 1Institute of Microstructure Technology (IMT), Karlsruhe Institute of Technology (KIT) — 2Light Technology Institute (LTI), Karlsruhe Institute of Technology (KIT) — 3Institute for Applied Materials (IAM), Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
Snakes exhibit special locomotion styles because they are legless and slide in direct contact with the ground. Therefore, their ventral scales feature interesting tribological properties. Previous studies analyzed oriented micron-sized fibril structures on the scales which seem beneficial for controlling friction during sliding but the actual nano-scale interaction mechanism was rarely explained. We characterized the friction behavior of this fibril structure by AFM and measured friction while scanning the step edges of the fibrils up and down. The mirco-fibril structures on the ventral scale of snakes produce comparable large friction peaks during upward scans but considerable lower friction for downward scans. This behavior leads to friction anisotropy in the direction of locomotion. The same result is found for the dorsal scales of sandfish (Scincus scincus) and a polymeric replica of scales of the Chinese cobra (Naja atra). The overall effect increases linearly with step height. Although different snake species exhibit diverse step heights, the distribution of step heights along the body of the examined snakes is very similar indicating dedicated friction anisotropy in different sections along snake bodies.