Optofluidic Assembly of Colloidal Photonic Crystals with Controlled Sizes, Shapes, and Structures

Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology, Daejeon, 305-701 (Korea)
Advanced Materials (Impact Factor: 17.49). 05/2008; 20(9):1649 - 1655. DOI: 10.1002/adma.200703022


The fabrication of various photonic structures with negligible cracking through evaporation-free colloidal self-assembly using silica particles dispersed in ethoxylated trimethylolpropane triacrylate (ETPTA) resin was investigated. The spherical photonic crystal balls, all of the same size, was prepared by using simple and high-throughput microfluidic devices. The emulsion drops were elongated initially but relaxed to a spherical shape if the particle concentration was not too high to immobilize the interface. The microfluidic device produced highly monodisperse emulsion drops, of which the size was proportional to the diameter of the inner capillary. It was observed that the proposed fabrication scheme was effective for creating non-close-packed colloidal crystals with well-controlled shapes and lattice constants.

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Available from: Shin-Hyun Kim, Oct 04, 2015
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    • "To progress in our understanding of the stability behavior of Pickering emulsions, it is therefore important to prepare droplets of both controlled size and controlled surface coverage using well defined NPs as stabilizers. The past decade has seen the rise of microfluidic tools, see for a non-exhaustive review [6], that allow, among other, a good control of emulsions, i.e. monodisperse droplets [7] and surface coverage by particles [8] [9]. In this article we have set-up a microfluidic system allowing such a coupled control. "
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    ABSTRACT: We study the stability of a model Pickering emulsion system. A special counter-flow microfluidics set-up was used to prepare monodisperse Pickering emulsions, with oil droplets in water. The wettability of the monodisperse silica nanoparticles (NPs) could be tuned by surface grafting and the surface coverage of the droplets was controlled using the microfluidics setup. A surface coverage as low as 23$\%$ is enough to stabilize the emulsions and we evidence a new regime of Pickering emulsion stability where the surface coverage of emulsion droplets of constant size increases in time, in coexistence with a large amount of dispersed phase. Our results demonstrate that the previously observed limited coalescence regime where surface coverage tends to control the average size of the final droplets must be put in a broader perspective.
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    • "Scale bars b = 10 lm and c = 100 lm. This image is reproduced with permission from Kim et al. (2008). Ó 2008 Wiley–VCH Verlag GmbH & Co. KGaA Microfluid Nanofluid energy requirements (Tao et al. 2008). "
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    ABSTRACT: This paper is a review of microfluidics for particle synthesis from photocrosslinkable materials. Microfluidics for particle synthesis is rapidly gaining attention as a viable method for the synthesis of particles with applications in drug delivery, security, abrasives, rheology, catalysis and other areas. Particle synthesis can follow several schemes, but the focus of this review is particle synthesis from photocrosslinkable materials. In these systems, solid particles are formed by the light-initiated cross-linking of precursor materials. This review begins with a discussion of photocrosslinkable materials, typically synthetic hydrogels for particle synthesis applications. Next, polydimethyl siloxane and glass devices are presented as the primary microfluidic devices for synthesis from photocrosslinkable materials. Then, the review discusses three types of polymeric particles: spherical, spheroidal and Janus. Subsequently, composite particles and metal or metal oxide particles are discussed. The review closes with a discussion of particle throughput and the outlook for the field of particle synthesis from photocrosslinkable materials.
    Microfluidics and Nanofluidics 01/2014; DOI:10.1007/s10404-014-1333-y · 2.53 Impact Factor
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    ABSTRACT: A study was conducted to demonstrate a simple method for patterning photonic domes and balls, by dispensing colloidal suspension drops through a capillary nozzle over a substrate. It was demonstrated that hemispherical domes and spherical colloidal crystal ball have the unique optical property that the stop band for normal incident light is independent of the direction of light propagation. It was found that this property arises, as colloidal crystallization occurs from the spherical interface, resulting in concentric particle arrangements. The study also an alternative approach, where arrays of hemispherical domes of colloidal crystals were fabricated using colloidal particles dispersed in a refractive-index matching solvent with high polarity.
    Advanced Materials 09/2008; 20(17):3211 - 3217. DOI:10.1002/adma.200800782 · 17.49 Impact Factor
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