Nanoscale design of snake skin for reptation locomotions via friction anisotropy

Multi-mode scanning probe microscopy is employed to investigate the nanostr ucture of dermal samples from three types of snakes. Sophisticated friction modifying nanostructures are described. These include an ordered microfibr illar array that can function to achieve mission adaptable friction charact eristics. Significant reduction of adhesive forces in the contact areas cau sed by the 'double-ridge' nanoscale microfibrillar geometry provides ideal conditions for sliding in forward direction with minimum adhesive forces an d friction. Low surface adhesion in these local contact points may reduce l ocal wear and skin contamination by environmental debris. The highly asymme tric, 'pawl-like' profile of the microfibrillar ends with radius of curvatu re 20-40 nm induces friction anisotropy in forward-backward motions and ser ves as an effective stopper for backward motion preserving low friction for forward motion. The system of continuous micropores penetrating through th e snake skin may serve as a delivery system for lubrication/anti-adhesive l ipid mixture that provides for boundary lubrication of snake skins. (C) 199 9 Elsevier Science Ltd. All rights reserved.