Fabricating fluorine-free superhydrophobic grass-like alumina films on glass with anti-reflective properties

Superhydrophobic anti-reflective coatings are essential for anti-fouling in optical lenses and solar cell encapsulation. However, coatings combining anti-reflection, superhydrophobicity, fluorine-free composition, and scalable processing remain scarce. Here, we develop superhydrophobic films via magnetron-sputtered alumina, followed by hot-water treatment and fluorine-free chemical vapor deposition. The film exhibits a water contact angle of 177°, a sliding angle of 3°, and a maximum visible-light transmittance of 95.37%. Its excellent superhydrophobicity enables remarkable self-cleaning ability. In addition, the film retains superhydrophobicity after acid (pH ∼ 1), alkali (pH ∼ 12), ultrasonication (40 kHz), heat treatment (150 °C), and water immersion tests, showing promise for practical applications.