Self-comparison measurement for slippage on superhydrophobic surfaces based on the wetting transition

This paper describes a self-comparison measuring method for the slip length of fluid flow over superhydrophobic surfaces consisting of a pillar array based on the wetting transition. The wetting transition of the liquid resting on a superhydrophobic surface in the measuring course may lead to the disappearance of the slippage effect, which can be used to measure the slip length before the wetting transition. Based on this feature, the slip length formula for this measuring method is deduced. Then, to verify this method, a rheological experiment for 70 wt% glycerin solution flow over a superhydrophobic surface with carbon nanotube (CNT) forest was carried out on a commercial rheological system with plate-and-plate configuration. Results show that even on the CNT-coated surface that can induce little slip length, the experimental slip length is still on the same scale as the theoretical one. This measuring method can be used to measure the slip length of liquid flow over the superhydrophobic surface consisting of a pillar array with good flexibility.