Drag Reduction of Anisotropic Superhydrophobic Surfaces\nPrepared by Laser Etching

Abstract

In\nthis research, the anisotropic superhydrophobic surface is prepared\non a stainless steel surface by laser etching, and the drag reduction\nproperty of the anisotropic surface is studied by a self-designed\nsolid–liquid interface friction test device. Periodic arrangement\nstructures of quadrate scales with oblique grooves are obtained on\na stainless steel surface by a laser. After modification by fluoride,\nthe surface shows superhydrophobicity and anisotropic adhesive property.\nHere, the inclined direction of grooves and the inverse direction\nare defined as RO and OR, respectively. By changing the inclination\nof the grooves, a surface is obtained with a contact angle of 160°\nand a rolling angle difference of 6° along the RO and inverse\nRO direction. It is verified by numerical simulation and experiment\nthat the subjected force of water droplets on the surface is different\nalong the RO and inverse RO direction. Furthermore, the as-prepared\nsurface has different drag reduction effects along the two directions.\nWith the increase of velocity, the drag reduction effect of the superhydrophobic\nsurface decreases against the RO direction, while the drag reduction\neffect along the RO direction is almost unchanged. We believe the\nanisotropic surface will be helpful in novel microfluid devices and\nshipping transportation.