Flow characteristics of silicon oil in nanochannels

The nonlinear flow of liquids through nanoscale channels play an important role in the separation and purification properties of porous membranes, the manufacture of biofilm ionic channels and microfluidic chips, the production of micro electro-mechanical systems. Silicon oil flow experiments were conducted through anodic alumina films with pore sizes of 26, 67, 89, and 124 nm, in which flow mechanism and characteristics of the oil through the nanoscale channels were analyzed. Four nanoflow features are revealed: (1) The experimental flow rate is less than the theoretical flow rate through nanochannels, as solid-liquid interaction increasing flow resistance. (2) At small shear rate, the boundary layer is one, indicating existence of a threshold pressure of oil flow through nanochannels. (3) The boundary layer decreases with the increasing of shear rate, and it rapidly decreases as shear rate increases when the value of shear rate is small. (4) The drag coefficient decreases nonlinearly with increasing shear rate, decreasing more slowly when value of shear rate is big, and trending towards 1 in the case of large shear rate. It is shown that the non-linearity of flow is induced by great solid-liquid interaction in nano and microscale, and increasing the driving force can raise the efficiency at the nanometer scale.

Automated summary

The experimental results reveal that the actual flow rate in nanochannels is lower than the theoretical flow rate due to increased solid-liquid interaction. A threshold pressure for oil flow through nanochannels exists at small shear rates. The boundary layer decreases with increasing shear rate, particularly rapidly at small shear rates, and the drag coefficient decreases nonlinearly with increasing shear rate, eventually tending towards 1 at large shear rates.