Stress-minimizing nano-cones and UV-polyurethane synergy: highly transparent, flexible superhydrophobic coatings with excellent durability

Transparent superhydrophobic coatings hold significant promise for diverse applications but face challenges in balancing optical performance with mechanical robustness. Here, we develop a multifunctional coating by integrating precision-engineered subwavelength nano-cone arrays, UV-curable polyurethane (Norland optical adhesive, NOA) matrices, and a low-friction perfluoropolyether (PFPE) monolayer. Fabricated via nanosphere lithography and nanoimprinting, the coating demonstrates excellent superhydrophobicity (static contact angle: 165°, sliding angle: 2°), and achieves 92% visible-light transmittance, 3% reflection reduction, and a haze as low as 0.4%. Crucially, superhydrophobicity of the coating can be maintained under harsh conditions, including 18,000 abrasion cycles (20 kPa), 24-h high-speed water jets (2 bar), and 45 tape-peeling tests. Finite element analysis reveals that nano-cone geometry minimizes stress concentration, while NOA’s balanced mechanical properties enhance durability. The high flexibility of the coating ensures compatibility with curved surfaces for diverse substrates. This scalable approach overcomes the durability-transparency trade-off, enabling promising applications in self-cleaning optics, solar panels, and flexible electronics.