Fabrication of superhydrophobic surfaces from femtosecond laser patterned surfaces

A femtosecond oscillator is employed to create periodic grid patterns in a commonly used polymer, poly (methyl methacrylate), PMMA. The wettability measured in terms of static water contact angle shows that the laser patterning causes an enhancement in water contact angle and the magnitude of change depends on the irradiation fluence during writing. A water droplet placed on a laser-patterned surface spreads anisotropically and exhibits different static water contact angle along different directions. Micro-Raman and Scanning Electron Microscope studies carried out on laser patterned and nonpatterned regions clearly confirm that the observed wettability change is due to physical (morphological) changes rather than chemical changes. More interestingly, the replica of the periodic laser patterned structures created on a soft polymer, polydimethylsiloxane (PDMS), via soft lithography technique exhibits superhydrophobic behaviour with a rolling-off nature for the water droplet. This is likely to find variety of applications in diverse fields ranging from passive defogging of windscreen to waterproof clothing to non-stick cookware.