Oil-Grafted Track-Assisted Directional Transport of Water Droplets and Submerged Air Bubbles on Solid Surfaces.

Wettability-tailored tracks are emerging as an efficient approach to collecting and transporting underwater air bubbles as well as water from the mist. However, tailoring the surface wettability by modifying the surface structural features via physiochemical methods to create superhydrophilic-superhydrophobic contrast tracks suffers from long-term durability issues, while the emerging liquid-infused slippery surface has inherent design engineering limitations and issues from infused oil depletion. Herein, we demonstrate that by selective silicone oil grafting onto the glass substrate, it is possible to create a wettability contrast of ∼ 43°. Further, we illustrate the application of such tracks for underwater air bubble capturing and transportation in an aqueous medium with surface tension ranging from 72 to 43.5 mN/m. In addition, the potential of these nonadhesive and adhesive tracks for water collection from the mist is shown and the critical effect of the track dimension and intertrack spacing on the water harvesting rate is investigated in detail. The study illustrates that the nonadhesive nature of the oil-grafted region enables the easy transport of underwater air bubbles as well as water from the flow medium and thus offers an easy and facile approach to creating substrates for underwater air bubble collection and water harvesting.