Bioinspired mechanically robust metal-based water repellent surface enabled by scalably constructing a flexible coral-reef like Cu based architecture

Mechanical robustness has been a central concern for moving artificial superhydrophobic surfaces with extremely aqueous repellency to application practices. Avoiding use of micro/nano architecture composed bulk hydrophilic material becomes a common sense to prevent exposure of hydrophilic surface and thereby non-wettability degradation. Meanwhile, inexpensive and scalable coating techniques are still in demand. To address these challenges, we demonstrate here the robust mechanical durability of superhydrophobic surface with metal (hydrophilic) textures through scalable construction of a flexible coral-reef like Cu/Cu₂O architecture on various substrates including metals, glasses and ceramics. Discontinuous micro-scale coral-reef like Cu architecture is built by spraying commercial electrolytic Cu particles (15-65 urn) at supersonic velocities. Subsequent flame oxidation is applied to introduce a porous and hard surface oxide layer. The fluorinated surface retains its excellent water repellency with extremely low roll-off angle (1°) after cyclic bending/folding, sand-grit erosion, knife-scratching and even heavy loading of simulated acid rain droplets. Strong adhesion to glass, ceramics and metals up to 34 MPa can be achieved without applying any adhesive. The result show that the flexible Cu based superhydrophobic coating could have wide applications such as outdoor self-cleaning and, especially, corrosion protection of metal parts in aqueous environment.