In order to study fluid flow characteristics of the micro-nano gap,the boundary slip in micro-nano gap was studied using atomic force microscope,mainly from the standpoint of liquid viscosity.The solid sample was SiO2,the liquid sample was pentarythriol oleate with different viscosity,their molecular formula are C77H140O8,their viscosity were 32mm2/s and 150mm2/s,respectively.Using the relative velocity method processed the test results,as the results shown,two different types of pentaerythritol oleate on the face of SiO2 both have boundary slip,the boundary slip increases with increasing of liquid viscosity.The reason is shown as follow,with the viscosity increasing,the shear force which will increase between nearing the solid surface liquid molecules and contacting with solid surface liquid molecules,so that solid-liquid force is easy to overcome,easy to generate boundary slip.
