Carbonous materials, such as graphene and carbon nanotube, have attracted tremendous attention in the fields of nanofluidics due to the slip at the interface between solid and liquid. The dependence of slip length for water on the types of supporting substrates and thickness of carbonous layer, which is critical for applications such as sustainable cooling of electronic devices, remains unknown. In this paper, using colloidal probe atomic force microscope, we measured the slip length of water on graphene l_s supported by hydrophilic and hydrophobic substrates, i.e., SiO₂ and octadecyltrimethoxysilane (OTS). With the thickness of few-layer graphene increases to 3~4 layers, both l_s gradually converge to the value of graphite. Such thickness dependence is termed slip length translucency. Further, l_s is found to decrease by about 70% with the temperature increases from 300 K to 350 K for 2-layer graphene supported by SiO₂. These observations are explained by analysis based on Green-Kubo relation and McLachlan theory. Our results provide the first set of reference values for the slip length of water on supported few-layer graphene. They can not only serve as a direct experimental reference for solid-liquid interaction, but also provide guideline for the design of nanofluidics-based devices, for example the thermo-mechanical nanofluidic devices.
 

石墨烯,界面滑移,半透明性,流体力学