The use of surface texturization to reduce friction in sliding interfaces has proved successful in some tribological applications. However, it is still difficult to achieve robust surface texturing with controlled designer-functionalities. This is because the current existing gap between enabling texturization technologies and surface design paradigms. Surface engineering, however, is advanced in natural surface constructs especially within legless reptiles. Many intriguing features facilitate the tribology of such animals so that it is feasible to discover the essence of their surface construction. In this work, we report on the tribological behavior of a novel class of surfaces of which the spatial dimensions of the textural patterns originate from micro-scale features present within the ventral scales of pre-selected snake species. Mask lithography was used to produce implement elliptical texturizing patterns on the surface of titanium alloy (Ti6Al4V) pins. To study the tribological behavior of the texturized pins, pin-on-disc tests were carried out with the pins sliding against ultra-high molecular weight polyethylene discs with no lubrication. For comparison, two non-texturized samples were also tested under the same conditions. The results show the feasibility of the texturization technique based on the coefficient of friction of the textured surfaces to be consistently lower than that of the non-texturized samples. NomenclatureRECEIVED

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This work shows the friction response of textured steel surfaces whose deterministic design is inspired in the characteristics of the Vipera Ammodytes snake skin. The skin was studied to identify morphological, chemical, mechanical and tribological attributes that served as inspiration for the design of the deterministic patterns, which were reproduced in AISI 52100 steel samples by Photochemical Machining (PCM). The textured samples were tested in a pin-on-disc tribometer using AISI H13 steel as counter body. The results showed an effective reduction of up to 38% in the friction coefficient of the texturized samples when compared to the conventional ones, as well as an anisotropic friction behavior as a function of the sliding direction. In addition, it was observed that the percentage of texturized area of the samples strongly affected the friction response, especially for values higher than 20%.

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