Controlling the Wettability of Steel Surfaces Processed with Femtosecond Laser Pulses

Abstract

The wettability of a material surface is an essential property that can define the range of applications it can be used for. In the particular case of steel, industrial applications are countless but sometimes limited because of the lack of control over its surface properties. Although different strategies have been proposed to tune the wetting behavior of metal surfaces, most of them require the use of processes such as coatings with different materials or plasma/chemical etching. In this work, we present two different laser-based direct-write strategies that allow tuning the wetting properties of 1.7131 steel over a wide range of contact angles using a high repetition rate femtosecond laser. The strategy consists in the writing of parallel and crossed lines with variable spacing. A detailed morphological analysis confirmed the formation of microstructures superimposed with nanofeatures, forming a hierarchical surface topography that influences the wetting properties of the material surface. Contact angle measurements with water confirm that this behavior is mostly dependent on the line-to-line spacing and the polarization-dependent orientation of the structures. Moreover, we demonstrate that the structures can be easily replicated in a polymer using a laser-fabricated steel master, which enables low-cost mass production. These findings provide a practical route for developing user-defined wetting control for new applications of steel and other materials functionalized by rapid laser structuring.

Controlling the wettability of stainless steel from highly-hydrophilic to super-hydrophobic by femtosecond laser-induced ripples and nanospikes

“…[5][6][7][8] The articial fabrication of functional surfaces is not a simply accomplishable task. The dual-scale hierarchical structures with resolution ranging from nano to micro are needed to successfully mimic a particular surface with optical, 9-11 wetting 12,13 or tribological 14,15 properties. Due to the conned laser-matter interaction area, the ultrashort laser pulses gives a possibility to reach a precise structuring in the scale of micrometres by direct laser writing technique via ablation.…”

“…The laser-based processes for stainless steel surface wettability control were investigated by ablation of trenches and generation of LIPSS. 13,24 The laser processing parameters, as interline separation for grid patterning and polarisation for LIPSS generation, are proven to be key factors for the fabrication of super-hydrophobic surfaces. The static contact angle coverage for steel via laser structuring is between $90 -150 .…”

“…The static contact angle coverage for steel via laser structuring is between $90 -150 . 13,[24][25][26] Ultrashort laser structuring provides the signicant advantages versus the other techniques like radiofrequency plasma treatment 27 or additional surface layer coating 28 as it does not require the multiple-steps, vacuum environment or additional chemical consumables. However, to the best of our knowledge, there is no research work found in scientic literature exploring a single-step technique with the ability of tuning wetting state of stainless steel from highly-hydrophilic to superhydrophobic.…”

Tuning the period of femtosecond laser induced surface structures in steel: From angled incidence to quill writing

“…Also for the particular case of metals, this strategy has allowed its functionalization in an unprecedented manner including, among others, the fine control of surface wettability, the significant reduction in friction and wear, or the fabrication of materials with tailored optical or electrochemical properties. These applications are only a glimpse of what can be achieved with this technology [1][2][3][4][5][6].…”

Bioinspired Superhydrophobic Surfaces via Laser-Structuring

“…There are a number of natural surfaces that show properties such as superhydrophobicity as well as the ability to self-clean, including rose petals, reed leaves, and even the skin of some animals (Martinez-Calderon et al, 2016a). It has been fully demonstrated that such superhydrophobicity is decided by both surface chemistry and unique surface micro-nanostructures (Florian et al, 2018), which provides the basic strategy for developing bioinspired superhydrophobic surfaces. In rose petals, the surfaces consist of densely packed microhills covered by a large number of microtrenches, whose wetting regime corresponds to the Wenzel state (Feng et al, 2011).…”