Development of Large-Area Stamps for Roll-to-Roll Nanoimprinting and Additive Nanopatterning of Functional Materials Using Topographical Discontinuous Dewetting

Nanoimprint lithography (NIL) is a highly effective method for creating large-area nanopatterns due to its high throughput, high resolution, and low cost. Its commercial applications are becoming increasingly important in fields such as photonics, surface engineering, and metamaterials. The NIL process starts with the fabrication of the master mold using techniques like optical or electron-beam lithography on a silicon wafer. This master mold is then used to produce imprinting stamps, which in turn creates nanopatterned substrate surfaces through the imprinting of UV-curable materials. However, scaling NIL to large-scale roll-to-roll (R2R) processes poses challenges, as conventional master pattern fabrication methods are limited to small areas. Typically, large-area stamps for R2R NIL are made by stitching together small-area stamps on a flexible substrate, which results in rough seams and nonuniform imprints. To mitigate these issues, we developed a method called “stamp and step,” based on UV nanoimprinting. This method involves making multiple imprints with a small-area stamp on a substrate, with minimal gaps between the imprints. The resulting patterned substrate serves as a master mold for creating large-area stamps for R2R NIL. The quality of the large-area master mold is dependent on the gaps and edge roughness from the small-area imprints.

The optimized master mold is then utilized to fabricate large-area imprinting stamps for R2R nanoimprinting of UV-curable Norland Optical Adhesive (NOA) at a web speed of 102 mm/min. NOA is selected for its unique thermally switchable wetting properties, which allow it to transition from a high-surface-energy state to a low-surface-energy state after annealing at 150 °C. This property makes NOA an ideal ink-receiving substrate for additive ink patterning via topographical discontinuous dewetting (TDD). During TDD, inks are selectively deposited into the recessed areas of the annealed NOA patterns, while dewetting occurs on the elevated surfaces.[1] As proof of concept, we demonstrate R2R additive nanopatterning of metal through TDD using the R2R nanoimprinted NOA. We anticipate that our printing platform, offering scalability, flexibility, and cost-efficiency, will drive the sustainable large-area production of functional nanopatterns with minimal environmental impact, across a wide spectrum of applications, including metamaterials and optoelectronics.

Reference
[1] Corletto, A. and Shapter, J.G., 2021. Thickness/morphology of functional material patterned by topographical discontinuous dewetting. Nano Select, 2(9), pp.1723-1740.