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

Figure 5

Applications of 3D hierarchical structures fabricated by integrated assembly with merged top-down with bottom-up approaches. (a-b) (a) Schematic illustration for the transfer procedure for developed QR code stickers that could be laminated on target products. (b) An example of a 1 cm² sticker containing one thousand 50 μm sized QR codes made of 28 nm β-NaYF₄ nanocrystals, integrated on a private official document (top) and optical microscopy image of the PL mapping at 545 nm of one of the QR codes (middle). After black and white conversion and inversion of the image, the 50 μm NC-QR code, which directs to the internet link, is readable using an appropriate smartphone application (bottom). Reproduced with permission from [129]. Copyright 2014 IOP Publishing Ltd. (c–e) (c) Conceptual illustration for the multichannel transistor with densely aligned sub-10 nm graphene nanoribbons. (d) SEM image showing well-oriented 9 nm half-pitch PDMS cylinders that were revealed from the segregated PS-b-PDMS film by O₂ plasma etching. (e) characteristic curves of the three multichannel FETs with ribbon-to-ribbon width variation of 7.4 nm (left), 5.1 nm (middle), and 2.4 nm (right). Reproduced with permission from [145]. Copyright 2012 American Chemical Society. (f–h) (f) SEM images show morphology control of the BCP thin films inside the hollow chamber of the inverse opal (IO) frame according to the BCP film thickness. Inset illustration depicts structures ranging from nanosieves (left) to nanodomes (middle) and corrugated structures containing both perpendicular and parallel cylinders (right). (g) Size-selective separation performance of the 3D nanocolander membrane with varying particulate size of Au nanoparticles (5 to 30 nm). The pore size of the BCP nanosieve was fixed at 18 nm in diameter (corresponding to the volume fraction of PMMA at 28%). The dotted line represents the estimated separated efficiency of filtration with 18 nm-sized pores. (h) Plot of pure water flux through membranes with respect to the operating pressure with varying numbers of BCP solution coatings. Reproduced with permission from [153]. Copyright 2014 WILEY-VCH Verlag GmbH & Co. KGaA.

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