Prewetting dichloromethane induced aqueous solution adhered on Cassie superhydrophobic substrates to fabricate efficient fog-harvesting materials inspired by Namib Desert beetles and mussels

Abstract

Namib Desert beetles harvest water from harsh environments by using their hydrophilic-hydrophobic dorsal surfaces. Generally, Cassie-state superhydrophobic materials are chosen as substrates to prepare bioinspired (super)hydrophilic/(super)hydrophobic patterned surfaces. However, due to the low adhesion and strong repellency, aqueous solution cannot be directly set on Cassie superhydrophobic materials until the dropping volume is larger than 6.5 μL. Therefore, arranging a (super)hydrophilic substance on Cassie superhydrophobic substrates to construct (super)hydrophilic/superhydrophobic patterned surfaces still remains a challenge. In this work, by prewetting with dichloromethane (DCM), the mussel-inspired hydrophilic and bio-adhesive dopamine solution (DA) could be dripped onto a Cassie superhydrophobic Cu surface with an ultralow volume of 0.1 μL, whereby low surface tension DCM would "cloak" the high surface tension DA. Along with DCM volatility, DA was adhered on the Cassie superhydrophobic surface and would then self-polymerize into hydrophilic polydopamine domains, thus hydrophilic/superhydrophobic patterned surfaces with efficient water collection could be successfully developed inspired by Namib Desert beetles and mussels. The bioinspired materials show the potential for real-world industrialization in a large scale, which is of great significance for providing living security for those living in areas with no access to fresh water.