Long-term influence of laser-processing parameters on (super)hydrophobicity development and stability of stainless-steel surfaces

Gregorčič, Peter (author), Conradi, Marjetka (author), Hribar, Luka (author), Hočevar, Matej (author)

Controlling the surface wettability represents an important challenge in the field of surface functionalization. Here, the wettability of a stainless-steel surface is modified by 30-ns pulses of a Nd:YAG marking laser (λ = 1064 nm) with peak fluences within the range 3.3–25.1 J cm$^{−2}$. The short- (40 days), intermediate- (100 days) and long-term (1 year) superhydrophilic-to-(super)hydrophobic transition of the laser-textured surfaces exposed to the atmospheric air is examined by evaluating its wettability in the context of the following parameters: (i) pulse fluence; (ii) scan line separation; (iii) focal position and (iv) wetting period due to contact angle measurements. The results show that using solely a short-term evaluation can lead to wrong conclusions and that the faster development of the hydrophobicity immediately after laser texturing usually leads to lower final contact angle and vice versa, the slower this transition is, the more superhydrophobic the surface is expected to become (possibly even with self-cleaning ability). Depending on laser fluence, the laser-textured surfaces can develop stable or unstable hydrophobicity. Stable hydrophobicity is achieved, if the threshold fluence of 12 J cm$^{−2}$ is exceeded. We show that by nanosecond-laser texturing a lotus-leaf-like surface with a contact angle above 150° and roll-off angle below 5° can be achieved.

• Language: English
• Keywords: laser surface engineering, wetting, superhydrophobic surfaces, laser material processing, surface modification
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FS - Faculty of Mechanical Engineering
• Publication status: Published
• Publication version: Version of Record
• Year: 2018
• Number of pages: 15 str.
• Numbering: Vol. 11, iss. 11, art. 2240
• PID: 20.500.12556/RUL-105246
• UDC: 621.7(045)
• ISSN on article: 1996-1944
• DOI: 10.3390/ma11112240
• COBISS.SI-ID: 16343835
• Publication date in RUL: 14.11.2018

Record is a part of a journal

• Title: Materials
• Shortened title: Materials
• Publisher: MDPI
• ISSN: 1996-1944
• COBISS.SI-ID: 33588485

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.
• Licensing start date: 11.11.2018

Secondary language

• Language: Slovenian
• Keywords: laserski inženiring površin, superhidrofobne površine, laserske obdelave