Stable dopamine-based ink for facile fabrication of robust and efficient fog-collectors

Collecting sustainable fresh water from air is recognized as a promising strategy to alleviate the fresh water crisis, particularly in arid and moist deserts. Herein, we provide a stable dual-component dopamine-based ink (A-B ink) for hydrophilic-patterning of superhydrophobic copper substrate through facile inkjet process by aid of surface-tension-confined liquid strategy, achieving the Namib desert beetle mimetic surfaces. It involves the tailoring of functional dopamine-based solution (A component) by regulation of dopamine chemistry with designed primary amine-containing zwitterionic polymer (ZP-NH2), and the controllable initiation of dopamine polymerization upon contact with NaIO4 solution (B component). The results show that the use of ZP-NH2 is helpful to form a stable zwitterion-contained dopamine solution with controllable aggregate size, which favors the preservation of needle-like morphology. The patterned superhydrophilic zones greatly enhance fog capture ability due to the strong hydration capacity of zwitterions and increased interaction area with fog droplets. Larger wettability difference at pattern boundary (ΔWCA = 150.8°) drives faster coalescence and transport of water droplets, greatly improving the fog-collection rate (WCR) and the ratio of collected water mass to total fog flow mass (η). Further sequential assembly of one superhydrophobic mesh (#10SCM) with two patterned mesh (ink@#60SCM) just by a simple adhesion method allows WCR to reach 3.18 ± 0.19 g cm−2 h−1 and η to 5.41 %. The fog collection efficiency is increased by 156 % compared with the pure superhydrophobic assembled meshes. This work offers a facile and flexible strategy to produce robust and efficient fog collectors in a large scale based on dopamine chemistry. [Display omitted] •A stable A-B ink was tailored by regulating PDA formation with long-chain primary-amine containing zwitterionic polymer.•A-B ink was used to regioselectively patterned superhydrophobic copper, forming superhydrophilic needle-like surfaces to boost fog collection efficiency.•A 3D fog collector with one superhydrophobic and two ink-patterned meshes achieved higher efficiency and long-term stability.