Ultrathin Photothermal Percolating Metasurface to Combat Fogging

Fogging of surfaces poses a real safety issue for a plethora of applications, such as windows or eyewear. Several approaches have been investigated how this issue can be handled in a passive, energy-neutral way. Previous research has focused on altering the wettability by micro-/nanotexturing surfaces. Another alternative pathway is to exploit the sunlight in order to passively heat the surface. However, solar-based solutions are either broadband absorbing or thick, rendering the surface either intransparent or difficult to integrate into existing systems. Here we show a thin percolating Au-TiO2 metasurface which absorbs nearly 30% of the sunlight over just 11 nm. Based on the percolation effect, the surface remains its transparency in the visible, yet it stronlgy and broadly absorbs in the near-infrared.<br/>Due to its ultrathinness, the metasurface can be readily applied on any—including compliant—substrate and can easily be integrated into existing systems. Its photothermal response allows superior fog prevention and removal. The real-world applicabilty is demonstrated under non-ideal outdoor conditions, showing that the metasurface is ready for industrial implementation.