Control of the wetting properties of stainless steel by ultrashort laser texturing using multi-parallel beam processing

The laser surface microtexturing is increasingly used for the production of surfaces with desired wetting characteristics (i.e., superhydrophobicity). For this not only precise but also fast laser processing is needed. Microtextures not based entirely on laser induced material self-organization require relatively tight focusing of the laser beam which can not be achieved using fast beam scanning systems. Therefore, in this work, the possibility to use parallel laser processing by multi-beam array for control of the EN 1.4301 (AISI 304) stainless steel surface was investigated. High-energy picosecond laser pulses were used to pattern the polished steel surface using 8 x 8 beam array with two different patterning strategies: mesh and dot. The multi-beam patterning inevitably brings some irregularities due to variation of properties of the beams in the array. However, after the investigation of the influence of laser patterning parameters on the wetting properties of the steel surface, it was determined that multi-beam mesh patterning allows obtaining superhydrophobic surface properties through the right combination of texture depth, surface chemical properties and laser induced surface ripples. The dot patterning was even more promising and was found suitable for obtaining a broad spectrum of wetting states ranging from superhydrophobic to superhydrophilic, when appropriate patterning parameters were used, mostly by controlling selforganized surface structure shape by changing texture period (laser spot overlap).