Superhydrophilic soda-lime glass with a two-dimensional periodic surface fabricated by femtosecond laser processing

Laser surface texturing enables superhydrophilicity on glass surfaces, but increased roughness often reduces optical transmittance due to enhanced scattering. In this study, two-dimensional (2D) periodic structures were fabricated on soda-lime glass using femtosecond laser ablation as an extension of our previous one-dimensional (1D) groove design. The effects of periodic spacing and laser parameters on contact angle and optical transmittance were systematically investigated. Compared with 1D grooves, the 2D structures exhibited lower contact angles at the same period, while showing a slight reduction in transparency. Superhydrophilic glass (contact angle < 10°) was achieved at a processed area ratio of approximately 6%, while maintaining high transparency (~89%). The results indicate that the processed area ratio is a key structural parameter governing the trade-off between wettability and optical performance. These findings provide structural design guidelines for ultrafast laser manufacturing of transparent functional glass surfaces.