Liquid spreading along nanostructured superhydrophilic lanes

A liquid hanging from a liquid-filled tube can spread spontaneously on rough hydrophilic surfaces while it cannot on smooth hydrophilic surfaces, a difference resulting from the competition between the capillary suction pressures provided by the tube and by the surface roughness. In order to pattern liquids on solid surfaces utilizing such wetting characteristics, we investigate the dynamics of a spontaneous liquid spreading from a tube onto a nanostructured superhydrophilic microlane surrounded by a superhydrophobic background. We find distinct regimes of liquid film propagation dynamics to arise depending on the lane width and the liquid column height in the tube. We theoretically analyze the spreading rates of films, which change power laws in the course of spreading, and corroborate the theory with experiments. The spontaneous liquid patterning process reported in this work can provide a viable venue for such applications as electronic circuit printing and biochip fabrication.