title: Osmotic-pressure-controlled concentration of colloidal particles in thin-shelled capsules.
abstract: Colloidal crystals are promising structures for photonic applications requiring dynamic control over optical properties. However, for ease of processing and reconfigurability, the crystals should be encapsulated to form 'ink' capsules rather than confined in a thin film. Here we demonstrate a class of encapsulated colloidal photonic structures whose optical properties can be controlled through osmotic pressure. The ordering and separation of the particles within the microfluidically created capsules can be tuned by changing the colloidal concentration through osmotic pressure-induced control of the size of the individual capsules, modulating photonic stop band. The rubber capsules exhibit a reversible change in the diffracted colour, depending on osmotic pressure, a property we call osmochromaticity. The high encapsulation efficiency and capsule uniformity of this microfluidic approach, combined with the highly reconfigurable shapes and the broad control over photonic properties, make this class of structures particularly suitable for photonic applications such as electronic inks and reflective displays.
authors.affiliation: 1] Department of Physics, School of Engineering and Applied Sciences, Harvard University, 29 Oxford street, Cambridge, Massachusetts 02138, USA [2] Department of Chemical and Biomolecular Engineering, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Korea.
authors.forename: Shin-Hyun
authors.initials: SH
authors.lastname: Kim
authors.affiliation: Department of Physics, School of Engineering and Applied Sciences, Harvard University, 29 Oxford street, Cambridge, Massachusetts 02138, USA.
authors.forename: Jin-Gyu
authors.initials: JG
authors.lastname: Park
authors.affiliation: Department of Chemical and Biomolecular Engineering, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Korea.
authors.forename: Tae Min
authors.initials: TM
authors.lastname: Choi
authors.affiliation: Department of Physics, School of Engineering and Applied Sciences, Harvard University, 29 Oxford street, Cambridge, Massachusetts 02138, USA.
authors.forename: Vinothan N
authors.initials: VN
authors.lastname: Manoharan
authors.affiliation: Department of Physics, School of Engineering and Applied Sciences, Harvard University, 29 Oxford street, Cambridge, Massachusetts 02138, USA.
authors.forename: David A
authors.initials: DA
authors.lastname: Weitz