Processing and wetting behavior of hierarchically microstructured polymer foils

The demand for surface functionalized plastics is constantly rising. Therefore, industrial-scalable methods capable to provide surfaces with new functions are necessary. In this study, we demonstrate a strategy to apply hierarchical microstructures to transparent polyethylene terephthalate (PET) foils by plate-to-plate hot embossing. To that end, a stainless-steel stamp was patterned using two laser-based processes, namely Direct Laser Writing (DLW) and Direct Laser Interference Patterning (DLIP). Several single scale and multi scale structures with feature sizes in the range 3 µm up to 50 µm and depths between 0.1 µm and 10 µm were processed on the metal master and transferred to the PET surface. The topography characterization by confocal microscopy and scanning electron microscopy revealed a satisfactory replication of the microstructures from the stamp to the polymer, even for the smallest features with lateral sizes of ~100 nm. The patterned surfaces showed an increased hydrophobic behavior characterized by static water contact angles up to 10sBL.