In the Watkins group, we have developed a form of nanoimprint lithography (NIL) which allows for the direct patterning of nanoparticle and nanoparticle-polymer composite inks. The method, solvent-assisted soft NIL, provides a diverse platform for patterning nanostructures for a variety of applications such as optics, energy storage, and antimicrobial surfaces. This technique facilitates the patterning of different nanoparticles into sub-100 nm features on different substrates.  We are equpped for both batch and roll-to-roll nanoimprinting.  A descirption of the roll-to-roll tools can be found in the facilites section. 

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Figure. Photographs and micrographs of imprinted nanoparticle and nanoparticle/polymer hybrids on rigid and flexible substrates.

Composites

Solvent-assisted, soft NIL enables patterning of highly-loaded polymer/nanoparticle resins. For example, we have demonstrated patterning of 90/10 (by weight) TiO₂-nanoparticle based UV resins in the fabrication of photonic bandgap materials. By incorporating different nanoparticles such as ZrO₂, CeO₂, and Cu, we can target many different applications. Both the solvent and uncured UV resin provide fluidity for imprinting.

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Figure. Schematic of solvent-assisted soft NIL process (a) and SEM top-view of consecutively imprinted 50/50 organic/inorganic line gratings (b).

Inorganics

For fabrication of coatings or devices applicable in harsh environments, polymer/nanoparticle composites provide insufficient long-term stability and/or mechanical properties. Therefore, we have also extended our patterning technique to the direct patterning of inorganic, nanoparticle-based inks, relying on solvent transfer through a soft PDMS stamp.

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Figure. SEM images of imprinted inorganic TiO₂ nanoparticle-based inks on a large scale.

Related Publications:

• Beaulieu, M.R., Hendricks, N.R. and Watkins, J.J., 2014. Large-area printing of optical gratings and 3D photonic crystals using solution-processable nanoparticle/polymer composites. ACS Photonics, 1(9), pp.799-805.
• Kothari, R., Beaulieu, M.R., Hendricks, N.R., Li, S. and Watkins, J.J., 2017. Direct Patterning of Robust One-Dimensional, Two-Dimensional, and Three-Dimensional Crystalline Metal Oxide Nanostructures Using Imprint Lithography and Nanoparticle Dispersion Inks. Chemistry of Materials, 29(9), pp.3908-3918.
• Li, W., Zhou, Y., Howell, I.R., Gai, Y., Naik, A.R., Li, S., Carter, K.R. and Watkins, J.J., 2018. Direct Imprinting of Scalable, High-Performance Woodpile Electrodes for Three-Dimensional Lithium-Ion Nanobatteries. ACS applied materials & interfaces, 10(6), pp.5447-5454.