Plasmonic heating of protected silver nanowires for anti-frosting superhydrophobic coating.

Atmospheric frosting and icing pose significant problems for critical and common-use infrastructures. Passive anti-frosting and anti-icing strategies that require no energy input have been actively sought, with no viable and permanent solutions known yet. Bioinspired superhydrophobic (SH) materials have been considered promising path to explore; however, the outcome has been less than compelling because of their low resistance to atmospheric humidity. In most cases, condensing water on an SH surface eventually leads to mechanical locking of ice instead of ice removal. Hybrid strategies involving some form of limited energy input are being increasingly considered, each with its own challenges. Here, we propose the application of plasmonic heating of silver nanowires (AgNWs) for remote frost removal, utilizing an SH hybrid passive-active system. This novel system comprises a durable nanocomposite covered with a hydrophobized mesh of AgNWs, protected against environmental degradation by a tin oxide (SnO) shell. We demonstrate the frost removal ability at -10 °C and 30% RH, achieved by a combination of plasmonic heating of AgNWs with a non-sticking behavior of submicrometric droplets of molten frost on the SH surface. Heating was realized by illuminating the mesh with low-power blue laser light. Adjustment of the nanowire (NW) and shell dimensions allows the generation of surface plasmon resonance in illuminated NWs at a wavelength overlapping the emission maximum of the light used. In environmental stability tests, the nanostructures exhibited high atmospheric, mechanical, and thermal stability. The narrow-wavelength absorption of the structure in the blue light range and the reflective properties in the infrared range were designed to prevent protected surfaces from overheating in direct sunlight.