Hierarchically nanotextured surfaces maintaining superhydrophobicity under severely adverse conditions

Abstract

Superhydrophobic surfaces are highly desirable for a broad range of technologies and products affecting everyday life. Despite significant progress in recent years in understanding the principles of hydrophobicity, mostly inspired by surface designs found in nature, many man-made surfaces employ readily processable materials, ideal to demonstrate principles, but with little chance of survivability outside a very limited range of well-controlled environments. Here we focus on the rational development of robust, hierarchically nanostructured, environmentally friendly, metal-based (aluminum) superhydrophobic surfaces, which maintain their performance under severely adverse conditions. Based on their functionality, we superpose selected hydrophobic layers (i.e. self-assembled monolayers, thin films, or nanofibrous coatings) on hierarchically textured aluminum surfaces, collectively imparting high level robustness of superhydrophobicity under adverse conditions. These surfaces simultaneously exhibit chemical stability, mechanical durability and droplet impalement resistance. They impressively maintained their superhydrophobicity after exposure to severely adverse chemical environments like strong alkaline (pH ∼ 9-10), acidic (pH ∼ 2-3), and ionic solutions (3.5 weight% of sodium chloride), and could simultaneously resist water droplet impalement up to an impact velocity of 3.2 m s(-1) as well as withstand standard mechanical durability tests.

Nanosecond laser micro- and nanotexturing for the design of a superhydrophobic coating robust against long-term contact with water, cavitation, and abrasion

“…However, for industrial applications, the resistance to specific mechanical loads must be significant for longterm performance. That is why a lot of effort has been devoted to laboratory studies and the development of industrial techniques to construct superhydrophobic surfaces that are robust against mechanical loads and electrochemical impacts [11][12][13][14][15][16]. Despite considerable progress in this area, long-lived superhydrophobic coatings that are durable in harsh operating conditions are still highly desirable.…”

Superhydrophobicity vs. Ice Adhesion: The Quandary of Robust Icephobic Surface Design

“…A recent study shows that both the surface texture and the contact angle play an important role in the droplet impact event. Moreover, experimental studies on multitier surface textures with nanoscale morphology reveal indeed the potential of such surfaces to resist rebound to sticky transition also at high impact speeds . Recently, Checco et al presented a novel block copolymer based surface with well‐defined nanotexture (feature size of ≈10 nm) resisting impalement up to 10 m s −1 with millimeter‐sized water droplets.…”

Mechanically durable superoleophobic aluminum surfaces with microstep and nanoreticula hierarchical structure for self-cleaning and anti-smudge properties

“…Various techniques, including chemical etching and anodization techniques, have been used to produce superhydrophobic aluminum surfaces. Chemical etching method with various chemical etchants including boiling water [31,15], NaOH [12,22], HCl [30], ZnNO 3 Á6H 2 O [39,24], HNO 3 combined with Cu(NO 3 ) 2 [11,23], AlCl 3 combined with triethanolamine [21], La(NO 3 ) 3 [20], and FeCl 3 [25], and anodization method, with various electrolytes including oxalic acid [19,27], mixed solutions of NaCl and fluorosilane [33], have been used to prepare superhydrophobic aluminum surfaces. In the above-mentioned papers, nanoplatelet, microstep, nanoreticula, microflower, and nanowire structures have been created to achieve superhydrophobicity.…”