At first glance the new roll-to-roll printer resembles a newspaper printing press, but it’s much more complex. The quality of the final nano product depends on achieving the right balance of properties in the printing materials. Silicon and other rigid materials used to make normal nanoimprint lithography stamps can’t be wrapped around a cylinder. So Guo selected a polymer that’s stiff enough to work as a reliable stamp, but also pliable enough to wrap around the printer’s rolls. The finished resist also should stick to the substrate without being too viscous, and it must cure rapidly without shrinking.
“This work is an important industrial advance, which should [enable] a wider application of nanoimprinting,” says Stephen Chou, professor of electrical engineering at Princeton University and a pioneer of nanoimprint lithography since the late 1990s.
The process developed by Guo’s group could be used to make nanophotonic devices on a large scale and high-performance printed electronics, adds Ali Javey, assistant professor of electrical engineering and computer sciences at the University of California, Berkeley. However, Javey, who is developing roller-printing methods for electronic materials such as silicon nanowires, cautions that the longevity of the molds must be resolved before the technique is likely to be widely adopted by the industry. “It would be quite attractive if the mold does not have to be replaced often, in order to make the process as continuous as possible,” Javey says.
The Michigan researchers will work on shrinking the resolution achieved by the technique and developing it for manufacturing. Guo says his group is working with companies that are interested in using the printing process for their products. “This is a baseline technique that can be used to make many things,” he says.