Nanosecond laser textured superhydrophobic metallic surfaces and their chemical sensing applications

tThis 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 processingrates. 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 par-tial deoxidation of oxides on the surface induced during laser texturing. Textures exhibiting steady statecontact angles of up to ∼152◦with contact angle hysteresis of around 3–4◦have been achieved. Inter-estingly, the superhydrobobic surfaces have the self-cleaning ability and have potential for chemicalsensing applications. The principle of these novel chemical sensors is based on the change in contactangle with the concentration of methanol in a solution. To demonstrate the principle of operation ofsuch a sensor, it is found that the contact angle of methanol solution on the superhydrophobic surfacesexponentially decays with increasing concentration. A significant reduction, of 128◦, in contact angle onsuperhydrophobic brass is observed, which is one order of magnitude greater than that for the untreatedsurface (12◦), when percent composition of methanol reaches to 28%.