Development of low friction snake-inspired deterministic textured surfaces

Abstract

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

Friction reduction through biologically inspired scale-like laser surface textures

“…When comparing with the literature, it becomes apparent that frictional anisotropy of the laser-generated scale-like surface textures needs to be tested in the future. Such effects were reported for a variety of biological systems [ 55 – 56 ] and polymeric [ 21 – 22 ] as well as metallic [ 24 ] surface morphologies inspired by snake skin. Modelling efforts revealed that anisotropy is a function of the counter body’s surface roughness [ 56 ].…”

“…Researchers have started to look to biology in search for morphological textures that would allow for tribologically optimized surfaces [ 17 ]. Among the animals and biological structures that have been considered are butterfly wings [ 18 ], beetles and earthworms [ 19 ], scorpions [ 20 ] as well as (and most importantly) the skin of snakes and sand fish lizards [ 21 – 24 ]. It has been demonstrated, for example, that sandfish skin exhibits low friction and little wear [ 25 – 26 ].…”

“…The development of manufactured surface textures that are inspired by animals with scale-like surface morphology has resulted in fascinating insights. For texturing a titanium alloy, a lithography-based method was chosen that resulted in regular, elliptical protrusions, lowering friction compared to an untextured control sample [ 24 ]. In an approach resulting in surface textures much closer to the natural example, Baum et al showed that variations in the effective elastic modulus (therefore allowing for damping effects) have a significant influence on the occurrence of stick–slip motion in biological systems and manufactured structures [ 21 ].…”

Multi-Scale Surface Texturing in Tribology—Current Knowledge and Future Perspectives

“…The main conclusion of these works is that reptile skin typically follows an aperiodic and asymmetric pattern, which is in contrast to the deterministic idea of surface texturing such as arranging dimples or other shapes in a regular matrix. It can be figured that by copying more ideas from nature, improved texture designs with superior friction and wear performance can be achieved [43,87]. The research group led by Greiner conducted research towards a similar direction thus copying the surface texture of snakes and lizards to optimize the friction response under dry and lubricated conditions.…”

Coupling effect of morphology and mechanical properties contributes to the tribological behaviors of snake scales

“…The insights gained from the investigations of snake epidermis have inspired various design mimicking natural systems (Abdel-Aal and El Mansori, 2011; Abdel-Aal and El Mansori, 2013; Baum et al, 2014a; Baum et al, 2014b; Cuervo et al, 2016; Greiner and Schäfer, 2015; Mühlberger et al, 2015). For instance, it has been suggested that a surface texture resembling the scale microstructures of the Python regius is able to benefit the lubrication of cylinder liners (Abdel-Aal and El Mansori, 2011).…”