Leveraging the Physics of Sunlight-Surface Interactions to Architecture Transparent Materials Preventing Fogging

Interfaces separating different kinds of matter, or different phases of the same matter, abandon in nature and technology. What is more, they invariably play a critical role in all systems where they occur, from regulating transport of energy and species, to dictating system shape and form. Interfaces differ in their structure and properties from the bulk matter they surround and can be engineered to effect remarkable outcomes in a broad palette of applications. Here, I will primarily focus on liquid/gas and liquid/solid interfaces and their interaction with sunlight, employed in the rational design of photothermal materials, to control atmospheric water condensation, according to our will (1-3). I will discuss the design and architecture of energy neutral photothermal metasurface coatings, which, when material transparency is required, prohibit condensation and resulting “fogging” of surfaces. These coatings function with selective sunlight absorption, which enables them to maintain surface transparency to visible light. The photothermal coatings are unprecedented in their thinness (less than 10 nm) and performance, absorbing about one third of the solar energy selectively, mostly in the near infrared range (3), where half of the energy of sunlight resides. They can be easily deposited also on deformable and soft materials and are fabricated with common industrial processes. These combined capabilities render them a perfect candidate for a host of applications such as eyewear, car windows and windshields, mirrors and building windows. Finally, I will discuss the surface architecting of transparent materials able to maintain transparency alone, in the case of most severe condensation conditions and vapor influx, such as in the direct neighborhood of boiling liquids (4). Again, such architectures can be readily fabricated and up-scaled via simple molding or roll-to-roll processes.<br/><br/>(1) Mitridis E., et al., ACS Nano, 2018, 12 (7), pp 7009–7017.<br/>(2) Walker C., et al., Nano Lett., 2019, 19 (3), pp 1595–1604.<br/>(3) Haehler at al,. Nature Nanotechnology, 2023, in press.<br/>(4) Park. H. et al., in review.