Application of High-Surface Tension and Hygroscopic Ionic Liquid-Infused Nanostructured SiO2 Surfaces for Reversible/Repeatable Anti-Fogging Treatment

Anti-fogging coatings/surfaces have attracted much attention lately because of their practical applications in a wide variety of engineering fields. In this study, we successfully developed transparent anti-fogging surfaces using a non-volatile and hygroscopic ionic liquid (IL), bis(hydroxyethyl)dimethylammonium methanesulfonate ([BHEDMA][MeSO3]), with a high surface tension (HST, 66.4 mN/m). To prepare these surfaces, a layer of highly transparent, superhydrophilic silica (SiO2) nano-frameworks (SNFs) was first prepared on a glass slide using candle soot particles and the subsequent chemisorption of tetraethoxysilane (TEOS). This particulate layer of SNFs was then used as the support for the preparation of the [BHEDMA][MeSO3] layer. The resulting IL-infused SNF-covered glass slide was highly transparent, superhydrophilic, hygroscopic, and had self-healing and reasonable reversible/repeatable anti-fogging/frosting properties. This IL-infused sample surface kept its excellent anti-fogging performance in air for more than 8 weeks due to the IL’s non-volatile, HST, and hygroscopic nature. In addition, even if the water absorption limit of [BHEDMA][MeSO3] was reached, the anti-fogging properties could be fully restored reversibly/repeatably by simply leaving the samples in air for several tens of minutes or heating them at 100 °C for a few minutes to remove the absorbed water. Our IL-based anti-fogging surfaces showed substantial improvement in their abilities to prevent fogging when compared to other dry/wet (super)hydrophobic/(super)hydrophilic surfaces having different surface geometries and chemistries.