Anisotropic Spreading Along the Textured Surfaces with Isotropic Wetting
A.M. Emelyanenko, L.B. Boinovich and K.A. Emelyanenko
Fast spreading of a decane droplet over superoleophilic substrates with multimodal surface roughness and different chemical composition of the top textured layer is studied experimentally. New techniques and software based on digital image processing of high spatial resolution optical images of a spreading droplet developed in this study allowed one to distinguish 3 spreading fronts propagating along the substrate with multimodal roughness. It was found that the spreading velocities for bulk droplet base, for the front associated with the propagation of liquid over microchannels/microgrooves, and for the nanotexture impregnation are significantly differed from each other. An important new feature of spreading obtained in this study is related to anisotropic spreading for the latter two fronts at the simultaneous isotropic spreading of bulk drop base. The analysis of obtained experimental data for spreading of the decane droplet over the superoleophilic substrates with different chemical composition indicates that the spreading velocity is affected by the Young (local three-phase) contact angle, established in the course of spreading of liquid along the rough/textured substrate.
Keywords: Wettability, surface roughness, spreading kinetics, decane, superhydrophobic surfaces, superoleophilic surfaces, microtexture, nanotexture