Wettability modification

Wetting phenomena are ubiquitous in nature and technology. The wetting characteristics of materials play a central role in many scientific and technological applications, for example: oil recovery, water draining, self-cleaning surfaces, cell-adhesion, etc.

Wettability of materials can be tailored by modifying the surface chemistry or the topography of the surface. Using methods such as plasma treatment, silanization, or for example, with the coating with fluorinated compounds, the chemistry of the surface of materials can be modified, and hence their wetting characteristics. Another possible approach is by the modification of the topography. By using these two approaches, wettability of materials can be tailored from hydrophilic to hydrophobic.

Water contact angle for hydrophilic (i.e., with high surface energy), and hydrophobic materials (i.e., with low surface energy).
Extracted from: Riveiro A, et al. (2018) Laser Surface Texturing of Polymers for Biomedical Applications. Front. Phys. 6:16. doi: 10.3389/fphy.2018.00016

Laser texturing or laser surface texturing is one of the simplest techniques to modify both surface topography and chemistry of many different materials, from metals to polymers. In this technique, a focused laser beam is directed onto the surface of the material; then, the laser radiation is absorbed by the topmost layer. The optical energy provided by the laser beam induces the heating of the material, reaching the melting, or even the vaporization temperatures. This way a selective material removal is achieved, and the surface topography is modified. On the other hand, if the photons of the laser beam are sufficiently energetic, e.g., using UV-lasers, they are able, for example in polymeric materials, to break chemical bonds, and then modifying the surface chemistry of the material.

Schematic of the principle of operation of laser surface texturing (LST).
Extracted from: Riveiro A, et al. (2018) Laser Surface Texturing of Polymers for Biomedical Applications. Front. Phys. 6:16. doi: 10.3389/fphy.2018.00016

Under this research line, we investigate the application of lasers to produce superhydrophobic or superhydrophilic surfaces in different materials, self-cleaning surfaces, or we study the influence of the wettability in the biological response of the surface.

SEM images of laser treated PEEK surfaces under 1,064, 532, 355 nm laser wavelengths, and for the base material.
Extracted from: Riveiro A, et al. (2018) Laser Surface Texturing of Polymers for Biomedical Applications. Front. Phys. 6:16. doi: 10.3389/fphy.2018.00016
Laser texturing of PTFE to produce self-cleaning surfaces
Extracted from: Riveiro, A., et al. “Influence of laser texturing on the wettability of PTFE.” Applied Surface Science 515 (2020): 145984.