Thin Transparent Photothermal Coatings for Rapid Defogging in Automotive Applications

Abstract

Counteracting surface fogging to maintain surface transparency is significant to a variety of applications, including automotive lighting. Current energy-neutral approaches mostly rely on engineering the surface wettability, but suffer from contaminant deposition and lack of robustness and hence require frequent maintenance or renewal. This is particularly bothersome when the coating is within an enclosure, such as that of an automotive headlamp. Here, we design a maintenance-free, transparent, light-activated, photothermal composite material coating, to fully mitigate fogging-related issues. The coating contains dispersed indium tin oxide (ITO) nanoparticles in a dielectric matrix and is most absorptive in the near-infrared range, where a significant fraction of the thermal energy source lies, thus maintaining visible transparency. Based on nucleation thermodynamics, the photo-induced heating effect enables sustained and superior fog removal, also prevention when compared to uncoated samples. The coating is fabricated with readily and cost-effectively scalable industrial methods such as spray or dip coating. Its functionality is evidenced with standard visible thermal sources and on predominant materials employed in car headlights (glass and polycarbonate), which enables its direct application also on existing such surfaces, or similar.