Subwavelength LIPSS formation on SS304 by picosecond laser irradiation under water confinement

Abstract

Laser induced periodic surface structures were generated in a single step by applying picosecond laser irradiation at different repetition rates on a surface area of 15 × 15 mm2 of a stainless steel-304 probe immersed in a confinement liquid medium and on ambient air. Periodicity modification from high to low spatial surface frequency LIPSS was observed by modifying the pulse repetition rate from 1.3 to 402 kHz at a constant fluence (7 J/cm2) under water confinement. Additional experiments at lower fluences (1.78 and 5.33 J/cm2) were performed to evaluate the periodicity under water confinement. Wettability analysis of the processed area yielded significative changes on the drop contact angle showing a wetting transition from hydrophilicity to hydrophobicity of the samples surface treated by multiple impact pulses under water confinement.