Experimental Research on Boundary Slip of Confined Liquids at Micro/Nano Scale and Effect of Shear Rate and Viscosity

In order to research the flow and transportation property of liquids between solid and liquid at micro/nano scale, a commercial Atomic Force Microscope was modified by attaching a 45micro meter diameter glass ball to the end of cantilever to form a ball-disk contact, which was used to investigate boundary slip effect of confined liquids under different velocity. Solid surface specimen was prepared as hydrophilic Si (100) and hydrophobic OTS film surfaces on Si (100) verse different viscosity sucrose solution. The relationship between shear rate and boundary slip are discussed carefully. Results indicated that, slip boundary conditions are found for all different viscosity sucrose solution both on hydrophilic and hydrophobic surface, and slip length of liquid on solid surface with poor wetting property was obviously larger than that with good wetting property. Further more, the degree of slip is found to increase with shear rate and liquids viscosity for the two surfaces, which shows that boundary slip is shear rate and viscosity dependent. The results will be important for the research and control of the flow properties of confined liquids.