Sharkskin-inspired armour design: A facile powder-coating strategy for durable superhydrophobic surfaces in underwater applications

Underwater superhydrophobic surfaces (SHS) hold great potential for various applications, but their development has been hindered by complex fabrication and limited durability. This study reported the first demonstration of a sharkskin-inspired SHS that combined micro-riblet armouring with a one-step powder-coating strategy to form a volumetric superhydrophobic (SH) layer. Here, polydimethylsiloxane (PDMS)-functionalized fumed silica nanoparticles were directly embedded into a partially cured polyurethane (PU)/PDMS composite sharkskin microstructure, creating a robust, hierarchical interface. This bio-inspired design produced two unprecedented features: (i) a regenerative volumetric SH layer with water contact angle (WCA) of 161°, where nanoparticles were anchored into the thickness of the coating to a certain depth rather than merely on the surface, and (ii) a riblet-based armoured framework that physically shielded nanoscale features from abrasion and hydrodynamic erosion, sustaining hydrophobicity. As a result, the coating exhibited exceptional durability, retaining SH properties after 24 m of sandpaper abrasion, 30 days of saltwater immersion, outdoor exposure, or a 25-min water jet test. The surface further achieved a 34 % drag reduction, outperforming conventional SH coatings. This environmentally friendly, solvent-free, single-step, and scalable approach overcomes long-standing durability limitations of SH sharkskin surfaces and provides a practical platform for large-scale maritime, industrial, and underwater applications. • A novel facile approach for underwater use durable superhydrophobic surface (SHS). • The SHS featured elastic micro-riblet ‘armour’ design with regenerative SH layer. • The SHS endured 24 m abrasion (3.3 kPa load), over 30 days in saltwater/outdoor. • The SHS exhibited 34 % drag reduction and strong antifouling against bacteria.