title: Large-scale ordering of nanoparticles using viscoelastic shear processing.
abstract: Despite the availability of elaborate varieties of nanoparticles, their assembly into regular superstructures and photonic materials remains challenging. Here we show how flexible films of stacked polymer nanoparticles can be directly assembled in a roll-to-roll process using a bending-induced oscillatory shear technique. For sub-micron spherical nanoparticles, this gives elastomeric photonic crystals termed polymer opals showing extremely strong tunable structural colour. With oscillatory strain amplitudes of 300%, crystallization initiates at the wall and develops quickly across the bulk within only five oscillations. The resulting structure of random hexagonal close-packed layers is improved by shearing bidirectionally, alternating between two in-plane directions. Our theoretical framework indicates how the reduction in shear viscosity with increasing order of each layer accounts for these results, even when diffusion is totally absent. This general principle of shear ordering in viscoelastic media opens the way to manufacturable photonic materials, and forms a generic tool for ordering nanoparticles.
authors.affiliation: Nanophotonics Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge CB3 0HE, UK.
authors.forename: Qibin
authors.initials: Q
authors.lastname: Zhao
authors.affiliation: Department of Physics, Prifysgol Aberystwyth University, Wales SY23 3BZ, UK.
authors.forename: Chris E
authors.initials: CE
authors.lastname: Finlayson
authors.affiliation: Schlumberger Gould Research Center, Cambridge CB3 0EL, UK.
authors.forename: David R E
authors.initials: DR
authors.lastname: Snoswell
authors.affiliation: Nanophotonics Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge CB3 0HE, UK.
authors.forename: Andrew
authors.initials: A
authors.lastname: Haines
authors.affiliation: Deutsches Kunststoff-Institut (DKI), Darmstadt D-64289, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Schäfer
authors.affiliation: Deutsches Kunststoff-Institut (DKI), Darmstadt D-64289, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Spahn
authors.affiliation: Deutsches Kunststoff-Institut (DKI), Darmstadt D-64289, Germany.
authors.forename: Goetz P
authors.initials: GP
authors.lastname: Hellmann
authors.affiliation: Van't Hoff Laboratory for Physical and Colloid Chemistry, Department of Chemistry, Debye Institute for Nanomaterials Science, Utrecht University, Utrecht 3584 CH, The Netherlands.|Department of Chemical Engineering and Chemistry, Laboratory of Physical Chemistry, Eindhoven University of Technology, Eindhoven 5600 MB, The Netherlands.
authors.forename: Andrei V
authors.identifier: 0000-0001-9840-6014
authors.initials: AV
authors.lastname: Petukhov
authors.affiliation: Nanophotonics Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge CB3 0HE, UK.
authors.forename: Lars
authors.initials: L
authors.lastname: Herrmann
authors.affiliation: Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, UK.
authors.forename: Pierre
authors.identifier: 0000-0001-6870-9225
authors.initials: P
authors.lastname: Burdet
authors.affiliation: Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, UK.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Midgley
authors.affiliation: Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge CB2 3RA, UK.
authors.forename: Simon
authors.initials: S
authors.lastname: Butler
authors.affiliation: Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge CB2 3RA, UK.
authors.forename: Malcolm
authors.initials: M
authors.lastname: Mackley
authors.affiliation: Department of Electrical and Electronic Engineering, Synchrotron Light Application Center, Saga University, Saga 840-8502, Japan.
authors.forename: Qixin
authors.initials: Q
authors.lastname: Guo
authors.affiliation: Nanophotonics Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge CB3 0HE, UK.
authors.forename: Jeremy J
authors.identifier: 0000-0002-9606-9488
authors.initials: JJ
authors.lastname: Baumberg