We investigate the slippage effect in a super-hydrophobic micro-channel. The micro-scale grooves are fabricated on the vertical wall to make the super-hydrophobic surfaces, which enable us visualize the flow fields near walls and directly measure the slip length. Velocity profiles are measured using micro-particle image velocimetry (PIV). The velocity profile near the wall shows larger slip length and, if the groove structure is high and wide, the liquid meniscus forms curves into the valley so that the wavy flow is created after the grooves. Also depending on the ratio of pitch to width of the groove structure, the water meniscus status can be either sustained between the valleys or collapsed to be wet. This Cassie to Wenzel transition is observed in the micro-channel. And we investigate the effects of grooves shape and the flow rate on the wetting transition.

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