National Creative Research Initiative Center for Integrated Optofluidic Systems

Daejeon, South Korea

National Creative Research Initiative Center for Integrated Optofluidic Systems

Daejeon, South Korea
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Jeong W.-C.,KAIST | Jeong W.-C.,National Creative Research Initiative Center for Integrated Optofluidic Systems | Lim J.-M.,KAIST | Lim J.-M.,National Creative Research Initiative Center for Integrated Optofluidic Systems | And 11 more authors.
Lab on a Chip - Miniaturisation for Chemistry and Biology | Year: 2012

Submicron emulsions could be produced via the tip-streaming process in a flow-focusing microfluidic device. In this article, the stability of the liquid cone and thread for tip-streaming mode could be significantly improved by employing a three-dimensional flow-focusing device, in which the hydraulic resistance was adjusted by modulating the channel heights in the flow focusing area, orifice, downstream and dispersed phase inlet channel. The pressure range for tip-streaming mode was enlarged significantly compared with two-dimensional flow-focusing devices. Therefore, monodisperse emulsions were produced under this tip-streaming mode for as long as 48 hours. Furthermore, we could control the size of emulsion drops by changing the pressure ratio in three-dimensional flow-focusing devices while the liquid cone was easily retracted during the adjustment of pressure ratio in two-dimensional flow-focusing devices. Furthermore, using the uniform submicron emulsion droplets as confining templates, polyethylene glycol (PEG) particles were produced with a narrow size distribution at the sub-micrometre scale. In addition, magnetic nanoparticles were added to the emulsion for magnetic PEG particles, which can respond to magnetic field and would be biocompatible. © The Royal Society of Chemistry.


Cho S.,KAIST | Cho S.,National Creative Research Initiative Center for Integrated Optofluidic Systems | Shim T.S.,KAIST | Shim T.S.,National Creative Research Initiative Center for Integrated Optofluidic Systems | And 2 more authors.
Proceedings of the 16th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2012 | Year: 2012

We present the optofluidic system to generate compositionally featured microfibers. A photopolymerizable core liquid is stably transformed into a microfiber and safely conveyed to the outlet with the help of inert carrier liquid flows. The composition and dimension of microfibers was readily manipulated by changing core liquid materials and the input pressure of flows. Moreover, pneumatic valves were employed to fabricate sequentially segmented microfibers by switching on/off each core liquid flow. Finally, microfibers in the desired configurations are expected to be used to the multiplex biomolecular analysis.


Jeong W.-C.,KAIST | Jeong W.-C.,National Creative Research Initiative Center for Integrated Optofluidic Systems | Choi M.,KAIST | Lim C.H.,KAIST | And 3 more authors.
Lab on a Chip - Miniaturisation for Chemistry and Biology | Year: 2012

A facile PDMS-glass hybrid microfluidic device is developed for generating uniform submicrometer-scale double emulsion droplets with unprecedented simplicity and controllability. Compared with planar flow-focusing geometries, our three-dimensional flow-focusing geometry is advantageous for stably producing femto- to atto-liter droplets without the retraction problem of the dispersed phase fluid. In addition, this microfluidic platform can withstand the use of strong organic solvents (e.g. tetrahydrofuran (THF) and toluene) as a dispersed phase without deforming PDMS devices because the dispersed phase containing organic solvents does not directly contact the PDMS wall. In particular, monodisperse double emulsions are generated spontaneously via the internal phase separation of single emulsions driven by the diffusion of a co-solvent (tetrahydrofuran) in microfluidic devices. Finally, we demonstrated that the double emulsions can be used as morphological templates of ultrafine spherical silica capsules with controlled hierarchical pore networks via the evaporation-induced self-assembly (EISA) method. During EISA, triblock copolymers (Pluronic F127) act as a surfactant barrier separating the internal droplet from the continuous oil phase, resulting in the 'inverse' morphology (i.e. hydrophobic polymer-in-water-in-oil emulsions). Depending on the precursor composition and kinetic condition, various structural and morphological features, such as mesoporous hollow silica spheres with a single central core, multi-cores, or a combination of these with robust controllability can be seen. Electron microscopy (SEM, STEM, HR-TEM), small angle X-ray scattering (SAXS), and N2 adsorption-desorption confirm the well-controlled hierarchical pore structure of the resulting particles. © 2012 The Royal Society of Chemistry.

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