Sci. Adv. 2, e1601660 (2016)

Printing electronic devices with very small features in a short time and in a reproducible way over large areas represents a significant technological challenge. Some printing techniques achieve nanoscale structures, yet they are not compatible with high-throughput production. Relief printing, also known as flexography, is one of the most common techniques used in roll-to-roll manufacturing. The smallest feature size that can be obtained by the method is tens of micrometres, which is a serious limitation for applications in flexible electronics.

Now, Kim et al. report on a new flexography method with sub-micrometre resolution that works on both rigid and flexible surfaces. The method is based on nanoporous printing stamps comprising vertically grown carbon nanotubes embedded in a polymeric matrix. The pore size is chosen in such a way that it is larger than the ink particles but appreciably smaller than the printed features. Complex printing designs are achieved via controlled nanotube growth on photolithographically pre-patterned silicon substrates. Once loaded with an ink, the stamp coated by mechanically robust carbon nanotube arrays comes into uniform contact with the target substrate and enables the printing of high resolution images. This technique is readily scalable to roll-to-roll manufacturing and offers at least tenfold resolution improvement over current industrial flexographic printing.