An environmentally-friendly method to fabricate extreme wettability patterns on metal substrates with good time stability

Wettability patterns have significant application potential in liquid transportation and water collection. Plasma hydrophilization is high-efficient and less-destructive, and has been widely used for preparing wettability patterns. However, the plasma-treated surfaces tend to recover to its original wettability, causing invalidation of the patterns. As a green treatment method, boiled water treatment could construct nanostructures, which is favorable for hydrophilicity-retaining; while the hydrophilization effect of plasma treatment would promote the reaction. Therefore, it should be possible to combine plasma and boiled water treatments to prepare long-lasting wettability patterns. In this paper, superhydrophobic aluminum surfaces were modified by plasma jet followed by boiled water treatment. The time stability, microstructures and chemical compositions of the treated surfaces were investigated by testing contact angles, scanning electron microscope, X-ray diffractometer, and X-ray photoelectron spectroscopy. The surfaces treated by plasma jet and boiled water could retain super-hydrophilicity for a long time under various storage conditions, including normal ambient, high temperature or high humidity. On the basis of this technique, long-lasting patterns could be prepared on different metal substrates. The green method proposed is expected to have promising application potential in fabricating wettability patterns and lab-on-chip devices, especially for those used in severe conditions.