Superhydrophobic properties of ultrathin rf-sputtered Teflon films coated etched aluminum surfaces

Superhydrophobicity has been demonstrated on ultrathin rf-sputtered Teflon coated etched aluminum surfaces. The etching of aluminum surfaces has been performed using dilute hydrochloric acid. An optimized etching time of 2.5 min is found to be essential, before Teflon coating, to obtain a highest water contact angle of 164 +/- 3 degrees with a lowest contact angle hysteresis of 2.5 +/- 1.5 degrees, with the water drops simply rolling off these surfaces with even the slightest inclination of the sample. The presence of -CF3 radicals along with -CF2 radicals in the ultrathin rf-sputtered Teflon films, as investigated by X-ray photoelectron spectroscopy (XPS), contributes to the lowering of the surface energy on the aluminum surfaces. The presence of patterned microstructure as revealed by field emission scanning electron microscope (FESEM) together with the low surface energy ultrathin rf-sputtered Teflon films renders the aluminum surfaces highly superhydrophobic. (C) 2007 Elsevier B.V. All rights reserved.