Bio inspired self-cleaning ultrahydrophobic aluminium surface by laser processing

Micro channels and pillars were fabricated by a nanosecond laser source on thin aluminum foil of 100 mm thickness. The wettability of the laser processed m-patterns were evaluated by the static water contact angle and found to be at the Cassie-Baxter state. The roll-off and static contact angle are 5 degrees and 180 degrees respectively for the m-pillar structures. The m-pillar structure which has a well-formed m-cell structure demonstrated water droplet rebounding and a self-cleaning effect with edible sugar on the laser patterned surface. The elemental analysis suggests that the pulse width, frequency and power density could greatly influence the nature of the new aluminum oxide surfaces formed after laser processing, particularly in relation to the activation of those surfaces against hydroxylation and further chemisorption of organic molecules from air that transforms the surface free energy leading to a transition from a hydrophilic to ultrahydrophobic surface in a short interval of time.