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 (Tg), held at this temperature for some time, and then cooled below Tg 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 Tg 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.