Coupling Effect of Morphology and Mechanical Properties Contributes to the Tribological Behaviors of Snake Scales
It is known that the tribological behaviors of snake skins are contributed by the synergistic action of multiple factors, such as surface morphology and mechanical properties, which has inspired fabrication of scale-like surface textures in recent years. However, the coupling effect and mechanism remain to be elucidated. In this work, the morphology and mechanical properties of the scales from different body sections (leading body half, middle trunk and tailing body half) and positions (dorsal, lateral and ventral) of Boa constrictor and Eryx tataricus were characterized and compared to investigate the corresponding effects on the tribological behaviors and to probe the possible coupling mechanism. The morphological characterizations of scanning electron microscopy and atomic force microscopy revealed significant differences between the two species that the scales from Boa constrictor are rougher in general. The mechanical properties measured by nanoindentation corroboratively demonstrated substantial differences in elastic modulus and hardness. Interestingly, the ventral scales with lower surface roughness, together with relatively larger elastic modulus and hardness, manifest higher friction coefficients. A “double-crossed” hypothesis was proposed to explain the observed coupling effect of morphology and mechanical properties on friction, which may afford valuable insights for the design of bionic surface with desirable tribological performance.
Keywordsbionics coupling effect friction coefficient morphology mechanical properties snake scales
Unable to display preview. Download preview PDF.
This work was supported by National Natural Science Foundation of China (51375204 and U1601203), Jilin Provincial Science & Technology Department (20140101056JC), and Province Joint Fund (SXGJSF2017-2-4 and SXGJQY2017-1) and JLUSTIRT Program of Jilin University.
- Comanns P, Winands K, Pothen M, Bott R A, Wagner H, Baumgartner W. The Texas horned lizard as model for robust capillary structures for passive directional transport of cooling lubricants. SPIE Smart Structures and Materials+ Nondestructive Evaluation and Health Monitoring, 2016, 979711, https://doi.org/10.1117/12.2218873. Google Scholar
- Rechenberg I. Tribological characteristics of sandfish. Nature as Engineer and Teacher: Learning for Technology from Biological Systems, 2003, 8–11.Google Scholar
- Stidworthy J. Snakes of the World, Grosset & Dunlap Inc., USA, 1974.Google Scholar
- Mehrtens J M. Living Snakes of the World in Color, Sterling Pub Co Inc, USA, 1987.Google Scholar
- Ren L Q, Li J Q, Tong J, Chen B C. Bionic nonsmoothness and its applications. Proceedings of the 6th Asia-Pacific Conference of ISTVS, Shanghai, China, 2000, 351–358.Google Scholar
- Sun J-R, Hong C, Qian C, Li J-Q, Chen B C, Ren L Q. Bionic study on the dung beetle Copris ochus Motschulsky for reduction of soil adhesion. Acta Biophysica Sinica, 2001, 17, 785–793.Google Scholar
- Ren L Q, Liang Y H. Generation mechanism of biological coupling. Journal of Jilin University (Engineering and Technology Edition), 2011, 41, 1348–1357. (in Chinese)Google Scholar