Flow and slip transition in nanochannels

We experimentally investigate the Poiseuille flows in nanochannels. It is found that the flow rate undergoes a transition between two linear regimes as the shear rate is varied. The transition indicates that the nonslip boundary condition is valid at low shear rate. When the shear rate is larger than a critical value, slip takes place and the slip length increases linearly with increasing shear rate before approaching a constant value. The results reported in this work can help advance the understanding of flow slip in nanochannels.

Figure 1

Schematic (top panel) and fabricated chip (bottom panel) of the nanofluidic system.

Figure 2

Nanochannel characterization. Top panel: AFM studies of nanochannels. Channel height is 105.6 nm with surface roughness less than 1.1 nm. Bottom panel: An image of a fluorescent flow in nanochannels.

Figure 3

Experimental setup of the fluidic system. DI water is driven by a syringe pump with a desired flow rate. Arrows indicate the flow directions. Pressures at the reservoirs are measured by pressure transducers.

Figure 4

Time variation of $P_1$ in Fig. 3 for (a) flow rate $Q=0.03$ μl/h and (b) flow rate $Q=0.11$ μl/h in each channel.

Figure 5

Flow rate as a function of pressure drop. Error bars represent the standard deviation of three experiments. Dashed lines are a guide to the eye.

Figure 6

Slip length as a function of shear rate. Solid lines are a guide to the eye.