title: Flexible Near-Field Nanopatterning with Ultrathin, Conformal Phase Masks on Nonplanar Substrates for Biomimetic Hierarchical Photonic Structures.
abstract: Multilevel hierarchical platforms that combine nano- and microstructures have been intensively explored to mimic superior properties found in nature. However, unless directly replicated from biological samples, desirable multiscale structures have been challenging to efficiently produce to date. Departing from conventional wafer-based technology, new and efficient techniques suitable for fabricating bioinspired structures are highly desired to produce three-dimensional architectures even on nonplanar substrates. Here, we report a facile approach to realize functional nanostructures on uneven microstructured platforms via scalable optical fabrication techniques. The ultrathin form (∼3 μm) of a phase grating composed of poly(vinyl alcohol) makes the material physically flexible and enables full-conformal contact with rough surfaces. The near-field optical effect can be identically generated on highly curved surfaces as a result of superior conformality. Densely packed nanodots with submicron periodicity are uniformly formed on microlens arrays with a radius of curvature that is as low as ∼28 μm. Increasing the size of the gratings causes the production area to be successfully expanded by up to 16 in(2). The "nano-on-micro" structures mimicking real compound eyes are transferred to flexible and stretchable substrates by sequential imprinting, facilitating multifunctional optical films applicable to antireflective diffusers for large-area sheet-illumination displays.
authors.affiliation: Department of Cogno-Mechatronics Engineering, Department of Nano-Fusion Technology, Department of Optics and Mechatronics Engineering, College of Nanoscience and Nanotechnology, Pusan National University , Busan 609-735, Republic of Korea.
authors.forename: Young Woo
authors.initials: YW
authors.lastname: Kwon
authors.affiliation: Department of Materials Science and Engineering, KAIST Institute for The Nanocentury, Korea Advanced Institute of Science and Technology , Daejeon 305-701, Republic of Korea.
authors.forename: Junyong
authors.initials: J
authors.lastname: Park
authors.affiliation: Department of Materials Science and Engineering, KAIST Institute for The Nanocentury, Korea Advanced Institute of Science and Technology , Daejeon 305-701, Republic of Korea.
authors.forename: Taehoon
authors.initials: T
authors.lastname: Kim
authors.affiliation: Department of Cogno-Mechatronics Engineering, Department of Nano-Fusion Technology, Department of Optics and Mechatronics Engineering, College of Nanoscience and Nanotechnology, Pusan National University , Busan 609-735, Republic of Korea.
authors.forename: Seok Hee
authors.initials: SH
authors.lastname: Kang
authors.affiliation: Department of Materials Science and Engineering, KAIST Institute for The Nanocentury, Korea Advanced Institute of Science and Technology , Daejeon 305-701, Republic of Korea.
authors.forename: Hyowook
authors.initials: H
authors.lastname: Kim
authors.affiliation: Department of Materials Science and Engineering, KAIST Institute for The Nanocentury, Korea Advanced Institute of Science and Technology , Daejeon 305-701, Republic of Korea.
authors.forename: Jonghwa
authors.initials: J
authors.lastname: Shin
authors.affiliation: Department of Materials Science and Engineering, KAIST Institute for The Nanocentury, Korea Advanced Institute of Science and Technology , Daejeon 305-701, Republic of Korea.
authors.forename: Seokwoo
authors.initials: S
authors.lastname: Jeon
authors.affiliation: Department of Cogno-Mechatronics Engineering, Department of Nano-Fusion Technology, Department of Optics and Mechatronics Engineering, College of Nanoscience and Nanotechnology, Pusan National University , Busan 609-735, Republic of Korea.
authors.forename: Suck Won
authors.initials: SW
authors.lastname: Hong
keywords: antireflective diffusers; biomimetics; conformal phase masks; hierarchical structures; nanofabrication; near-field phase shift lithography