Bio-inspired surface modification of PDMS to reduce dry friction

Reducing friction and associated energy dissipation in mechanical systems is critical for a broad range of applications. Under dry condition, soft elastomers are inherently adhesive and display high friction coefficient, which leads to severe wear and damage during contact. The skin structure and the scales geometry of some squamate reptiles, especially snakes and lizards, offers a potential way for friction reduction under extremely dry conditions. The stiff keratin-based epidermis on soft dermic tissue helps snakes reduce friction in forward locomotion. This study aims to mimic such functional skins by modifying both the stiffness and topography of the elastomeric surfaces. Using a photoinitiated infiltration polymerization, glassy polyHEMA is formed within the skin of PDMS, in the presence of water. The as-prepared surface displays a integrated skin layer possessing fold-like structure, with stiffness increasing from glassy to rubbery with the increase of load. Under dry condition, the friction coefficient of the PDMS reduces from 1.6 to 0.14 with the modification.