Flash regeneration of superhydrophilicity and antifog performance of laser induced molybdenum based micro-nano structures by flame treatment

In this study, a low cost laser marker fast ablation of molybdenum (Mo) coated glass substrate was adopted to fabricate superhydrophilic micro-nano structure. A hierarchical micro-nano structure with quasi-periodical hillock-hollow micron structure and widely distributed nanoparticles were shown on the treated surface, which resulted in a contact angle of 0°. The treated glass showcased remarkable antifog performance without apparent degradation for over 12 months, which was an impressive record free of apparent degradation. It also exhibited apparent antifog performance with increased water contact angle (WCA) to 5.5° after two weeks salt spray test, such low WCA and impressive antifog performance after such long salt spray test has not been reported before. However, the sample surface exhibited a marked decline in superhydrophilicity and antifog performance after over 15 months storage in the laboratory, which was attributed to the deposition of organic pollutants in the ambient. Thermal annealing at 400 °C for 1 h partially restored the antifog and superhydrophilic properties, reducing the contact angle to 7.4°. Remarkably, a one-second flame treatment fully restored the superhydrophilicity and antifog properties, which induced surface chemistry redistribution and was not reported before. Additionally, the treated glass demonstrated self-cleaning properties and enhanced broadband transmission. This brief and straightforward treatment highlights the potential of laser-ablated glass for a wide range of practical applications.