Toward Long-Lasting Low-Haze Antifog Coatings through the Deposition of Zeolites

High-performance antifog coatings are critical for devices operating in high-humidity environments, such as endoscopes. However, existing antifog coatings have been unable to achieve good antifogging capability with low haze, uniform color, and high durability. The relationships between the properties of the cast solution and the quality of the resulting coatings remain unclear. This work was aimed to investigate the spreading dynamics of zeolite cast solutions on a glass substrate to elucidate the relationship between the wetting behavior and thin-film quality, as quantified by transmittance and haze. The fundamental understanding will lead to the development of highly stable zeolite-based antifog coatings with low haze and free from the interference effect. We used direct wet deposition to coat a glass substrate with a layer of pure-silica zeolite MFI, whose surface had a silanol density. The solvent and composition of the zeolite suspensions were varied with the aim of optimizing the uniformity of the coating. We found that the bulk transmittance and haze of the coating were dominantly controlled by the packing of zeolite particles at the micrometer scale, which was affected by the wetting property of the cast solution on the substrate. Our results demonstrated that long-lasting low-haze antifog coatings can be produced from pure-silica zeolite MFI suspended in ethanol in the absence of amorphous silica colloids.