Super-wetting interfaces as a multiphase composite prototype for ultra-low friction

Green ultra-low friction or negligible sliding friction with extremely low energy consumption has been the key to energy-saving, environmental friendliness and long-life machine operation in industrial applications. Inspired by the rapid movement of striders on the surface of water, a solid-liquid-gas-solid multiphase composite ultra-low friction system was constructed based on the deliberate assembly of special wetting interfaces. By the finite modification of the superhydrophilic/superhydrophobic interfaces and using environmentally friendly water as the main lubrication component, an ultra-low friction phenomenon was achieved under a contact stress of 255 Pa, and the corresponding friction coefficient was as low as 0.002. The dynamic contact angle test and Couette flow field characterization confirmed that the low contact angle hysteresis force at the solid-liquid interface constituted the main sources of friction force and determined the ultra-low friction characteristics of the interface thereof. Besides, multi-body dissipative particle dynamics simulation was applied to confirm the critical frictional laws. Moreover, the multiphase composite friction system constructed with a green ionic liquid polar component also exhibited ultra-low friction performance, showing excellent universality. More importantly, this new friction system completely avoided the occurrence of wear by preventing the direct contact of friction pairs. This work therefore is believed to provide a novel prototype for constructing an ultra-low friction system based on green lubricating components.