Bioinspired Mechanically Robust Metal‐Based Water Repellent Surface Enabled by Scalable Construction of a Flexible Coral‐Reef‐Like Architecture

Abstract

Mechanical robustness is a central concern for moving artificial superhydrophobic surfaces to application practices. It is believed that bulk hydrophilic materials cannot be use to construct micro/nanoarchitectures for superhydrophobicity since abrasion‐induced exposure of hydrophilic surfaces leads to remarkable degradation of water repellency. To address this challenge, the robust mechanical durability of a superhydrophobic surface with metal (hydrophilic) textures, through scalable construction of a flexible coral‐reef‐like hierarchical architecture on various substrates including metals, glasses, and ceramics, is demonstrated. Discontinuous coral‐reef‐like Cu architecture is built by solid‐state spraying commercial electrolytic Cu particles (15–65 µm) at supersonic particle velocities. Subsequent flame oxidation is applied to introduce a porous hard surface oxide layer. Owing to the unique combination of the flexible coral‐reef‐like architecture and self‐similar manner of the fluorinated hard oxide surface layer, the coating surface retains its water repellency with an extremely low roll‐off angle (<2°) after cyclic sand‐paper abrasion, mechanical bending, sand‐grit erosion, knife‐scratching, and heavy loading of simulated acid rain droplets. Strong adhesion to glass, ceramics, and metals up to 34 MPa can be achieved without using adhesive. The results show that the present superhydrophobic coating can have wide outdoor applications for self‐cleaning and corrosion protection of metal parts.

Cold Spray: Over 30 Years of Development Toward a Hot Future

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Fig. 21 The water repellency of cold sprayed Cu-based superhydrophobic coating: (a) the superhydrophobic performance on different substrate materials including (a1) Al alloy, (a2) Mg Alloy, (a3) Al2O3 ceramic and (a4) optical glass; (b) the results of water contact angle and water sliding angle on different substrates; (c) self-cleaning test result by using sticky starch powders; (d) the enhanced floating ability of different plates with superhydrophobic coating (Ref 244 )

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Bioinspired antifouling Fe-based amorphous coating via killing-resisting dual surface modifications

“…The wettability of the coatings prepared was evaluated by water contact angle measurements on a video-based optical system (Kino SL200B), five readings were achieved for each sample. The mechanical robustness of the superhydrophobic surface was assessed by both sandpaper and sand particle abrasion tests 46 , 47 . For the sandpaper abrasion experiments, the coating surface was placed onto 80# mesh sandpaper with a constant load of 100 g and slowly moved at a speed of 5 cm/s for 15 cm along both the horizontal and vertical directions.…”

Superhydrophobic Light Alloy Materials with Corrosion-Resistant Surfaces

“…Therefore, it is worth to note that the roughness of superhydrophobic surface should be optimized in the process of preparing superhydrophobic surface to improve its mechanical robustness. Luo et al reported a superhydrophobic surface which has the robust mechanical durability because of the flexible coral-reeflike hierarchical structure [52] (figure 6). The durability of hierarchical architectures is attributed to the flexible coralreef-like structure constructed by kinetic spray process.…”

“…Figure 6. Superhydrophobic surface with a flexible hierarchical rough structure[52] : The surface topography of the flame-oxidized coating (a) and enlarged(b). (c) Superhydrophobicity on various substrates.…”