Hierarchical ‘rose-petal’ ZnO/Si surfaces with reversible wettability reaching complete water repellence without chemical modification

Abstract Smart surfaces with externally controlled wettability patterns are ubiquitous building blocks for micro-/nanofluidic and lab-on-chip devices, among others. We develop hierarchical of ZnO nanorods grown on laser-microstructured silicon reversible photo-induced heat-induced wettability. The as-prepared superhydrophilic, very low water contact angles (~ 10°), transition to a wetting state high 150°) when annealed in vacuum. As the annealing temperature increases 400 °C, become completely water-repellent. Even though present angles, at same time, they adhesive droplets, which do not roll off even tilted 90° or 180 o (rose-petal effect), unlike standard hydrophobic typically combine roll-off angles. return superhydrophilic irradiated UV light, indicates external stimuli. Based this transition, we demonstrate local modification by irradiation through mask, results directed liquid motion, useful microfluidic applications. obtained work usually only after chemical surface organic coatings, was necessary developed here, reducing cost processing steps fabrication route. These rose-petal can be used as “mechanical hands” several applications, such no-loss transport small volumes, precision spectroscopy, Furthermore, water-repellent surfaces, rarely reported elsewhere, may find important applications frictionless other devices.