Nanosecond laser textured superhydrophobic metallic surfaces and their chemical sensing applications

This work demonstrates superhydrophobic behavior on nanosecond laser patterned copper and brasssurfaces. Compared with ultrafast laser systems previously used for such texturing, infrared nanosecondfiber lasers offer a lower cost and more robust system combined with potentially much higher processing rates. The wettability of the textured surfaces develops from hydrophilicity to superhydrophobicity overtime when exposed to ambient conditions. The change in the wetting property is attributed to the partial deoxidation of oxides on the surface induced during laser texturing. Textures exhibiting steady state contact angles of up to similar to 152 degrees. with contact angle hysteresis of around 3-4 degrees. have been achieved. Interestingly, the superhydrobobic surfaces have the self-cleaning ability and have potential for chemical sensing applications. The principle of these novel chemical sensors is based on the change in contact angle with the concentration of methanol in a solution. To demonstrate the principle of operation of such a sensor, it is found that the contact angle of methanol solution on the superhydrophobic surfaces exponentially decays with increasing concentration. A significant reduction, of 128 degrees, in contact angle on superhydrophobic brass is observed, which is one order of magnitude greater than that for the untreated surface (12 degrees), when percent composition of methanol reaches to 28%. (C) 2015 The Authors. Published by Elsevier B.V.