Direct Patterning of Robust One-Dimensional, Two-Dimensional, and Three-Dimensional Crystalline Metal Oxide Nanostructures Using Imprint Lithography and Nanoparticle Dispersion Inks

Dimensionally stable one-dimensional (1-D), two-dimensional (2-D), and three-dimensional (3-D) high aspect ratio crystalline metal oxide nanostructures are fabricated using soft nanoimprint lithography with inks comprised of nanoparticle (NP) dispersions in solvent or in sol–gel precursors for the metal oxide. Crystalline TiO2 and indium tin oxide (ITO) NP dispersions in solvent are imprinted using a solvent permeable patterned poly­(dimethylsiloxane) (PDMS) stamp to yield robust crystalline nanostructures that are dimensionally stable to calcination (less than 8% linear shrinkage in imprinted feature heights upon heat treatment at 500 °C). Inks comprised of 80% crystalline NPs dispersed in 20% sol–gel binder are patterned using thermal- or UV-assisted imprinting with a PDMS stamp. The composition and physical properties of the dimensionally stable imprinted metal oxides (TiO2 and ITO) can be altered by varying the composition of the ink. Rapid printing of high aspect ratio nanostructures and sub-100 nm features are easily realized. Residual layer free, direct imprinting of isolated features is achieved by using an ink with the appropriate surface energy to ensure dewetting at the stamp–substrate interface. The technique is extended to create 3-D mesh nanostructures by deploying a simple layer-by-layer imprint strategy. TiO2 3-D mesh nanostructures are robust and mechanically stable to calcination at temperatures of 1000 °C, which results in an anatase to rutile transition. The direct fabrication of high quality dimensionally stable metal oxide nanostructures opens the door to solution based and roll-to-roll processing of robust and efficient inorganic electronic, optical, and energy generation and storage devices.