Creating superhydrophobic surface structures via the rose petal effect on stainless steel with a picosecond laser

A sub-five picosecond laser was used to create a range of surface structures on stainless steel. The stainless steel exhibited a transition in surface from laser-induced periodic surface structures (LIPSS), of the order of 1 µm, to grains via a LIPSS/mountainous double structure. The wettability of the stainless steel surface was characterized by measuring the contact angle and was observed to have changed from a hydrophilic surface (63.6°) to a superhydrophobic one (160.0°) due to the laser processing. This equated to an increase in contact angle of approximately 100.0°. This has been attributed to the creation of hierarchical surface structures that exhibit the rose petal effect. Additionally the contact angle hysteresis and the surface roughness have been measured and characterized. The use of a picosecond laser to generate such surfaces demonstrates a viable, low-cost alternative to using a femtosecond laser.