Counteracting surface fogging to maintain surface transparency is important for a variety of applications including eyewear, windows and displays. Energy-neutral, passive approaches predominantly rely on engineering the surface wettability, but suffer from non-uniformity, contaminant deposition and lack of robustness, all of which substantially degrade durability and performance. Here, guided by nucleation thermodynamics, we design a transparent, sunlight-activated, photothermal coating to inhibit fogging. The metamaterial coating contains a nanoscopically thin percolating gold layer and is most absorptive in the near-infrared range, where half of the sunlight energy resides, thus maintaining visible transparency. The photoinduced heating effect enables sustained and superior fog prevention (4-fold improvement) and removal (3-fold improvement) compared with uncoated samples, and overall impressive performance, indoors and outdoors, even under cloudy conditions. The extreme thinness (~10 nm) of the coating—which can be produced by standard, readily scalable fabrication processes—enables integration beneath other coatings, rendering it durable even on highly compliant substrates.
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We acknowledge the support of the cleanroom team at IBM research in Rüschlikon Switzerland, namely R. Stutz, U. Drechsler and A. Olziersky. Further, we acknowledge the technical assistance of L. Steinmann, J. Vidic, H. Albers, C. Germann, D. Trottmann and P. Feusi, all from ETH Zurich. We also acknowledge H. Lambley for help with condensation modelling and imaging, D. Kim for assistance with SEM imaging, the Scientific Center for Optical and Electron Microscopy (ScopeM) and P. Zeng for TEM imaging, H. Park for graphical assistance and fruitful discussions regarding experimental design, R. Ghosh for photocatalytic tests (all from ETH Zurich), Rodenstock Schweiz AG for providing the eyewear and MeteoSwiss for providing meteorological data. This work was financially supported by the Swiss National Science Foundation under grant number 179062 (D.P. and T.M.S.).
A patent has been filed by ETH Zürich and is pending (EP22161807.7: Heating device for preventing or removing a deposition). The inventors are I.H., D.P., G.S., T.M.S. and E.M. The remaining author (N.F.) has no conflict of interest.
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Supplementary Notes 1–10 and Figs. 1–10.
Outdoor test in Walenstadt, Switzerland (I0 ≈ 339 W m−2, Tamb ≈ 4 °C, RH ≈ 80%).
Visibility test in Davos, Switzerland (I0 ≈ 212 W m−2, Tamb ≈ 4 °C, RH ≈ 46%).
Outdoor test in Davos, Switzerland (I0 ≈ 212 W m−2, Tamb ≈ 4 °C, RH ≈ 46%).
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Haechler, I., Ferru, N., Schnoering, G. et al. Transparent sunlight-activated antifogging metamaterials. Nat. Nanotechnol. 18, 137–144 (2023). https://doi.org/10.1038/s41565-022-01267-1