A novel technique for investigation of complete and partial anisotropic wetting on structured surface by X-ray microtomography.

An experimental study about the anisotropic wetting behavior of a surface patterned with parallel grooves is presented as an application example of a novel technique for investigation of complete and partial anisotropic wetting on structured surface by X-ray microtomography. Shape of glycerin droplets on such surface is investigated by X-ray micro computed tomography (microCT) acting as a non-intrusive, full volume 3D microscope with micrometric spatial resolution. The reconstructed drop volumes enable to estimate the exact volumes of the drops, their base contours, and 3D static contact angles, based on true cross-sections of the drop-surface couple. Droplet base contours are compared to approximate geometrical contour shapes proposed in the literature. Contact angles along slices parallel and perpendicular to the grooves direction are compared with each other. The effect of the sessile drop volume on the wetting behavior is discussed. The proposed technique, which is applicable for any structured surface, enables the direct measure of Wenzel ratio based on the microCT scan in the wetted region usually inapproachable by any others. Comparisons with simplified models are presented and congruence of results with respect to the minimum resolution needed is evaluated and commented.