From Solution to Microstructures in Minutes: Microdroplet-Derived Stand-Alone TiO₂ Surfaces for Simultaneous Water Harvesting and Treatment

Abstract

We present a straightforward and eco-friendly method to transform a titanium tetraisopropoxide (TTIP) solution into superhydrophobic TiO2 microstructures by ambient microdroplet deposition. At lower temperatures the micropillars of amorphous TiO2 act as nucleation sites for condensing humidity to form droplets. However, the microstructures facilitate efficient water runoff despite TiO2’s hydrophilic character by a combination of surface hydrophobicity and gravity. Additionally, the photocatalytic TiO2 surface resists biofilm formation and degrades the contaminants, offering long-term collection of safe water and its purification, which has been demonstrated with examples. We demonstrate that the microdroplet-based methodology developed for the conversion of solution into microdroplets can also be applied to other metal oxides, including CuO and ZnO, highlighting the universality of the process.