Underwater Recoverable Superhydrophobic Surface with Hierarchical Structure

Abstract

Underwater superhydrophobic surfaces (SHSs) are promising for drag reduction but are limited by the metastability of underwater air plastrons. Inspired by the replenishment mechanism of the water spider’s air plastron, a recoverable SHS with a sparse micro-nano hierarchical structure was fabricated by obtaining a microcone array structure through laser etching and mold replication, followed by the chained nanoparticle deposition and fluorination treatment. The surface exhibited exceptional durability, sustaining 100 abrasion cycles (2 kPa) and 5.5 h water jetting (25 kPa). This is attributed to the microcone array, which protects the superhydrophobic nanoparticles under mechanical action. The hierarchical structure exhibited underwater aerophilicity, which enabled 34 cycles from fully wetting to superhydrophobicity. Rotational rheometric analysis revealed a drag reduction rate of 13.6%. Fluid dynamics simulations showed that the microstructure reduced wall shear stress, achieving a drag reduction rate of 14.2% at a flow velocity of 1 m/s and a wall-slip velocity of 0.15 m/s. This study provides design directions and theoretical foundations for the application of SHS in sustainable drag reduction.

Keywords

underwater / recoverable superhydrophobic surface / hierarchical structure / air plastron

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Funding

National Natural Science Foundation of China(51973033)

National Natural Science Foundation of China(11774049)