Large-scale hot embossing of 1 µm high-aspect-ratio textures on ABS polymer

Hot embossing is the most promising method for surface micropatterning of low-value-added products made of cheap polymers such as acrylonitrile butadiene styrene (ABS). In hot embossing, a polymeric part is compressed with a micropatterned mold at a temperature slightly above the glass transition temperature (T_g), held at this temperature for some time, and then cooled below T_g for demolding. However, through this study, we demonstrate that using this conventional strategy to replicate 1 µm structures on a large area on ABS results in defective replicas or damaged molds. We propose a viscous embossing strategy, wherein the polymer is embossed far above its T_g and demolded shortly thereafter in the viscous state. The absence of cooling is the key for damage-less demolding of 1 µm structures on a large area. Yet, an excessive increase of the temperature and time results in the formation of a thermally-induced tensile skin on the polymer surface, as evidenced by the experimental and theoretical analyses performed in this study. In this study, 100 million 1–6 µm wide high-aspect-ratio (1–4) holes were embossed on a smartphone-sized area on the ABS polymer in a few seconds. This proposed strategy exhibits several advantages such as highly precise and more productive replication, which are not observed in the conventional hot embossing technique.