Abstract: We prepared super-hydrophobic solutionby adding 2% perfluorinatedoctyltriethoxysilane and additiveto modified-organosilicone dilute solution.We implemented micron order super-hydrophobic coating on inner-walls of three micro-tubes with diameters of 0.447 mm, 0.728 mm and 0.873 mm to form super-hydrophobic micro-tubes. The contact angles of water on their inner surfacesare all larger than 150°.We further constructed aninnermicro-tube fluid characteristicexperimental system and exploredsuper-hydrophobic resistance reduction law. We measured frictional resistance coefficients f of de-ionized water flowing micro-tubes with super-hydrophobic layer and without super-hydrophobic layer for Re changing from 100~3000.Experimental results show flowing resistance in a micro-tube is significantly reduced through super-hydrophobic processing. Moreover, such resistance gradually reduces with the increase of the innerdiameter of a micro-tube. The maximum decreasing amplitude canreach 29.08%.Super-hydrophobic coating can make the transition of flow from laminar to turbulenceinobviously delayed and the transitional Re in micro-tubes increases with the increase of the diameter.

Key words: copper micro-tube, contact angle, fictionalresistance coefficient, Reynoids, transition of flow