Bioinspired Ribbed Nanoneedles with Robust Superhydrophobicity

Abstract

The robustness of superhydrophobicity is a fundamental issue for the applications of water‐repellent materials. Inspired by the hierarchical structures of water‐strider legs, this work describes a new water‐repellent material decorated with ribbed, conical nanoneedles, successfully achieved on the surface of copper and consisting of copper hydroxide nanoneedle arrays sculptured with nanogrooves. The behavior of water drops on an as‐prepared surface under various external disturbances is investigated. It is shown in particular that squeezing and relaxing drops between two such surfaces leads to a fully reversible exploration of the solid surface by the liquid, which is distinct from other superhydrophobic surfaces. This unique character is attributed to the penetrating Cassie state that occurs at the ribbed, conical nanoneedles. The proprietary lateral nanogrooves can, not only vigorously support the enwrapped liquid‐air interface when a force is applied to the drop, but also provide reliable contact lines for the easy de‐pinning of the deformed interface when the force is released from the drop. The results confirm the exceptional ability of strider legs to repel water, and should help to further the design of robust water‐repellent materials and miniaturized aquatic devices.

Recent Progress in Bionic Condensate Microdrop Self‐Propelling Surfaces

“…Accordingly, the nonaligned structures may also be used to create more efficient condensation heat-transfer surfaces as long as the surface adhesion of each nanoneedle is sufficiently low to ensure the efficient self-removal of suspended condensate microdrops via mutual coalescence. Inspired by the conical setae of the legs of the water strider, Yao et al [101] developed a type of clustered copper hydroxide ribbed-nanoneedle structure with robust superhydrophobicity. During the squeezing and relaxation process of the tested water droplets, the surface adhesion of functional films and nanoneedle sidewalls is negligibly low, which may be ascribed to the synergetic effect of the sharp tip and hierarchical surface nanogrooves of the nanoneedles.…”

The icephobic performance of alkyl-grafted aluminum surfaces

“…The chemical baths used for coating contained 1.0 % of octadecyltrimethoxysilane (ODTMS, from Fisher Scientific) [35], 1.0 % of heptadecafluorodecyltrimethoxysilane (FAS, from Shin Etsu Chemical Co.) [36], or 5.0 mM stearic acid (SA, from Wako) [37].…”

“…The solvents were ethanol/water (9:1 v/v) [35], methanol/water (9:1 v/v) [36], and pure ethanol [37], respectively. All the coating protocols applied in this study are widely used by others and their description can be found in greater detail elsewhere [35][36][37].…”

Recent biomedical applications of bio-sourced materials

“…1D) [18,19]. The legs of water striders are covered with numerous needleshaped setae arranged in a similar orientations at the micron scale, with a tilt angle of approximately 20 • from the surface [20].…”

“…The legs of water striders are covered with numerous needleshaped setae arranged in a similar orientations at the micron scale, with a tilt angle of approximately 20 • from the surface [20]. Inspired by the water strider legs, some multiscale structured materials with a superhydrophobic surface have been developed [18,21]. Zhang et al prepared superhydrophobic coatings on a gold thread to compare their forces and motions on gold wires supported on water surfaces (Fig.…”