Article

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

ABSTRACT

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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    • "Increasing humidity involves a reduction of the evaporation rate and an increase of the internal drop pressure that may lead to swelling and/or disintegration of particles. Regarding the correlation between microparticle quality and colloidal particle concentration in suspension, two concentration values responsible for radical changes in particle morphology should be distinguished: 16 vol%., the percolation limit below which void particles may frequently occur [26]; 50 vol%, the concentration that initiates a liquid–solid phase transition in the colloidal system [15]. In the optimal concentration range, 16–33 vol%., the quality of microparticles is independent of concentration (but may depend on other parameters, for instance, the evaporation rate). "
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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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    • "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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