Recent Advances in Unconventional Lithography for Challenging 3D Hierarchical Structures and Their Applications

Figure 2

Schematic illustrations of fabrication process for 3D hierarchical micro- and nanostructures via (a) two-step photolithography and soft lithography, (c) sequential t-NIL, and (e) vacuum-assisted CFL. (b) SEM images showing the fabricated 3D micro/nano-hierarchical structures via two-step photolithography, followed by molding. Reproduced with permission from [59]. Copyright 2009 WILEY-VCH Verlag GmbH & Co. KGaA. The bottom left SEM image shows close-up view of the selected area in top SEM image. Right SEM image of the bottom shows single-level pillars. (d) SEM images show the tilted cross section of the primary imprint 2 μm (top left) grating mold and the secondary imprint 250 nm (top right) grating mold. The hierarchical structures were obtained from two steps (bottom left) and three steps (bottom right) of imprinting. Reproduced with permission from [61]. Copyright 2006 IOP Publishing Ltd. (f) SEM images show the several connected bridges of different width and density for given base structures via vacuum-assisted CFL. Reproduced with permission from [71]. Copyright 2009 Wiley-VCH Verlag GmbH & Co. KGaA.