Fast Generation and Restoration of Superhydrophilicity and Antifog Property by Flame Treatment

Abstract This study reports, for the first time, an ultrafast flame treatment lasting only a few seconds to create superhydrophilic surfaces on flat glass and fused quartz, achieving a 0° water contact angle （WCA） without reducing optical transmission. In contrast, conventional 900 K annealing for 2 h achieved superhydrophilicity but caused transmission loss and was effective only on soda lime glass. Laser‐ablated Si‐coated glass achieved superhydrophilicity and antifog effect, which performance had been maintained for approximately 2 years and 3 months—the longest reported. However, WCA increased over time due to airborne organic pollutant deposition, which deteriorated antifog performance. Traditionally, thermal annealing for ≥1 h was required to restore hydrophilicity, limiting scalability. To address this challenge efficiently, fast flame treatment within a few seconds was adopted regenerating the superhydrophilicity and antifog performance successfully. Additionally, the area density of capillary forces was proved a measure of hydrophilic strength, consistent with preliminary experimental results.