Femtosecond laser-induced surface wettability modification of polystyrene surface

• Published in: Science China. Physics, mechanics & astronomy mechanics & astronomy, 2016-12, Vol.59 (12), p.124211-5, Article 124211
• Main Authors: Wang, Bing, Wang, XinCai, Zheng, HongYu, Lam, YeeCheong
• Format: Article
• Language: English
• Subjects: Astronomy; Chemical bonds; Classical and Continuum Physics; Contact angle; Droplets; Electrons; Femtosecond; Grooves; Hydrophilicity; Hydrophobicity; Irradiation; Lasers; Observations and Techniques; Parameter modification; Parameters; Photoelectrons; Physics; Physics and Astronomy; Pits; Polystyrene resins; Scanning electron microscopy; Surface roughness; Water drops; Wettability; X ray photoelectron spectroscopy
• ISSN: 1674-7348; 1869-1927
• DOI: 10.1007/s11433-016-0307-1

In this paper, we demonstrated a simple method to create either a hydrophilic or hydrophobic surface. With femtosecond laser irradiation at different laser parameters, the water contact angle (WCA) on polystyrene’s surface can be modified to either 12.7° or 156.2° from its original WCA of 88.2°. With properly spaced micro-pits created, the surface became hydrophilic probably due to the spread of the water droplets into the micro-pits. While with properly spaced micro-grooves created, the surface became rough and more hydrophobic. We investigated the effect of laser parameters on WCAs and analyzed the laser-treated surface roughness, profiles and chemical bonds by surface profilometer, scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). For the laser-treated surface with low roughness, the polar (such as C—O, C=O, and O—C=O bonds) and non-polar (such as C—C or C—H bonds) groups were found to be responsible for the wettability changes. While for a rough surface, the surface roughness or the surface topography structure played a more significant role in the changes of the surface WCA. The mechanisms involved in the laser surface wettability modification process were discussed.