Controlling the wetting characteristics of fluids (oil and water) on surfaces is highly desirable for a variety of industrial processes, such as painting, bonding, and lubrication applications. This can be achieved by altering the surface chemistry and/or topography of a material, which can be accomplished through a variety of techniques, including plasma treatment, chemical modification, surface coatings as well as microprocessing methods such as direct laser writing and direct laser interference patterning.
This study summarizes recent developments in the field of functionalization of polymer surfaces, including polyethylene terephthalate (PET), polycarbonate (PC) and polytetrafluoroethylene (PTFE) using hot-embossing methods as well as direct laser fabrication approaches.
The influence of different hot embossing parameters on the resulting texture topography was investigated. In case of the oil wettability tests (on PET), a method to characterize its spreading behavior was developed, allowing a comparison between the produced surface textures. In particular, a superoleophilicity state was reached, in which the contact angle approached zero. Furthermore, hierarchical structured surfaces showed fast wetting rates up to 1.4 mm²/s.
Regarding water-wettability, the microstructured PET surfaces showed an increased hydrophobic state rising from 76° on the flat reference up to 120°. In case of PC, similar results are obtained, reaching 140°, whereas on PTFE surfaces a super-hydrophobic state was achieved, characterized by water contact angles over 150° and a very small hysteresis (< 5°).