High Superhydrophobicity Achieved on Poly(ethylene terephthalate) by Innovative Laser-Assisted Magnetron Sputtering

The main development described in this paper consists of combining magnetron sputtering with a Nd:YAG laser to provide additional properties to the deposited thin films. The combination of both of these techniques has been revealed as an innovative methodology by the complementary effects able to respond to all the technical requirements of the desired ultrathin film properties. Plasma sputter-deposited fluoropolymers have been deposited on poly(ethylene terephthalate) (PET) substrates by this innovative Nd:YAG laser-assisted magnetron sputtering technique from a poly(tetrafluoroethylene) (PTFE) target. Laser irradiation of the substrate, occurring directly in the deposition chamber simultaneous to the first step of the deposition process, exhibits the advantage of inducing a micropatterning of the polymer surface by a photoablation process and then affords a high control of the roughness and microstructure. Deposition parameters of the fluoropolymer thin film have been optimized to obtain the maximum F/C atomic ratio to optimally functionalize the structure with fluoro groups; the F/C ratio was evaluated by X-ray photoelectron spectroscopy. Finally, the combination of the optimized sputtering parameters and the Nd:YAG laser treatment of the PET substrates led to superhydrophobic surfaces with a high water contact angle (theta = 160 degrees). The films' morphology and topography were studied by scanning electron microscopy and atomic force microscopy, respectively.