Experimental Investigation of Wetting Anisotropy on Microgrooved Brass Surfaces

Through a systematic study of microgrooved brass surfaces, the effect of parallel, periodic microgroove geometry on the wettability is examined experimentally and compared to that of flat surfaces, where the drop size is comparable to the groove dimensions.A total of 18 brass samples are fabricated by micromachining without any chemical modification of the surface The substrates have groove depths in the range of 26 to 122 μm, groove widths of 27 to 187 μm, and are about 45 mm x 45 mm in size, with a thickness about 3 mm.A high degree of wetting anisotropy is observed on most of the microgrooved surfaces. A significantly higher value of static contact angle (SCA) in the orthogonal direction (across the grooves) of the grooves is observed on the microgrooved surfaces compared to the contact angle on the flat baseline surfaces which are hydrophilic in nature.The contact angle also shows a significant dependence on droplet volume. The observed wetting behavior is attributed to the manner in which droplets rest on these surfaces, contact line pinning by the groove edges and texture and local variation of roughness of the micromachined brass surfaces.