Stand-off fabrication of irregularly shaped, multi-functional hydrophobic and antireflective metal surfaces using femtosecond laser filaments in air

Multi-functional metal surfaces with simultaneous superhydrophobic and antireflective properties have a wide range of industrial, medical, and defense applications. Rapid fabrication of such multifunctional surfaces on irregularly shaped metals and on a large scale has been a challenge. Here we demonstrate an approach for rapid, standoff fabrication of multi-functional surfaces with super-hydrophobic and antireflective properties on irregularly-shaped samples, by texturing them with femtosecond laser filaments in air, followed by chemical fluorination treatment. Two types of metals with a variety of curved surfaces have been processed at a standoff distance of 1 m: the type 304 stainless steel and the type Ti–6Al–4V titanium alloy. Through laser processing and fluorination, multi-functional surfaces with the water contact angle of over 150° and diffused reflectance below 9%, over the wavelength range from 240 to 2500 nm, have been realized on both metals. Our results suggest that this technique could enable cost-effective and large-scale fabrication of irregularly-shaped, multi-functional surfaces that can be useful for various applications.