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Gunpo, South Korea

Rhee D.K.,Sungkyunkwan University | Jung B.,Samsung | Kim Y.H.,Sungkyunkwan University | Yeo S.J.,Sungkyunkwan University | And 6 more authors.
ACS Applied Materials and Interfaces | Year: 2014

A novel multiscale porous architecture where an individual particle is nested inside a hollow chamber of inverse-opal (IO) frame is created using a large scale self-Assembly of core-shell structured colloidal particles and subsequent selective removal of the outer shells of the colloids. Since the nested particle is smaller than the size of individual IO chamber, the interconnected nanochannels are spontaneously formed within the structured frame. The size of internal nanochannels is readily tuned to have high permeability and size-selective separation capability, which is successfully tested for nanoparticle separation. © 2014 American Chemical Society. Source

Yi H.,Ulsan National Institute of Science and Technology | Hwang I.,Ulsan National Institute of Science and Technology | Lee J.H.,Kyungpook National University | Lee D.,Ulsan National Institute of Science and Technology | And 7 more authors.
ACS Applied Materials and Interfaces | Year: 2014

A simple yet scalable strategy for fabricating dry adhesives with mushroom-shaped micropillars is achieved by a combination of the roll-to-roll process and modulated UV-curable elastic poly(urethane acrylate) (e-PUA) resin. The e-PUA combines the major benefits of commercial PUA and poly(dimethylsiloxane) (PDMS). It not only can be cured within a few seconds like commercial PUA but also possesses good mechanical properties comparable to those of PDMS. A roll-type fabrication system equipped with a rollable mold and a UV exposure unit is also developed for the continuous process. By integrating the roll-to-roll process with the e-PUA, dry adhesives with spatulate tips in the form of a thin flexible film can be generated in a highly continuous and scalable manner. The fabricated dry adhesives with mushroom-shaped microstructures exhibit a strong pull-off strength of up to ∼38.7 N cm -2 on the glass surface as well as high durability without any noticeable degradation. Furthermore, an automated substrate transportation system equipped with the dry adhesives can transport a 300 mm Si wafer over 10 000 repeating cycles with high accuracy. © 2014 American Chemical Society. Source

Bae W.-G.,Seoul National University | Kim S.M.,Seoul National University | Choi S.-J.,MCNet Co. | Oh S.G.,Seoul National University | And 3 more authors.
Advanced Materials | Year: 2014

An asymmetric ratchet structure within microchannels is demonstrated by directionally guided light transmission for controlled liquid flow. A direct and facile method is presented to realize programmed asymmetric structures, which control the fluid direction and speed. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Yoon H.,Seoul National University of Science and Technology | Sung S.H.,Seoul National University | Koh J.H.,Seoul National University | Kim S.M.,Seoul National University | And 3 more authors.
Macromolecular Research | Year: 2015

Directional wetting or spreading on asymmetric structures have received much attention because of their potential to control the liquid flow in microfluidic devices. Although there have been many reports on directional liquid flows, the flow speeds of the directional flows could not be predicted. Here, we present a controllable strategy for directional flow on a multiscale two-face prism array, one face is smooth and the other face is roughened. The polymeric surface of the prism is roughened by oxygen plasma while the other side is blocked by a coated metal film. With the designed structure, we demonstrate a unidirectional liquid flow and manipulate the flow speed in an open channel. From a simplified model suggested here, the flow speed could be predicted quantitatively.[Figure not available: see fulltext.] © 2015, The Polymer Society of Korea and Springer Sciene+Business Media Dordrecht. Source

Suh D.,Hoseo University | Tak H.,Korea Basic Science Institute | Tak H.,Sungkyunkwan University | Choi S.-J.,MCNet Co. | And 2 more authors.
ACS Applied Materials and Interfaces | Year: 2015

A permeability- and surface-energy-controllable polyurethane acrylate (PUA) mold, a "capillary-force material (CFM)" mold, is introduced for capillary-force lithography (CFL). In CFL, the surface energy and gas permeability of the mold are crucial. However, the modulation of these two main factors at a time is difficult. Here, we introduce new CFM molds in which the surface energy and permeability can be modified by controlling the degree of cross-linking of the CFM. As the degree of cross-linking of the CFM mold increases, the surface energy and air permeability decrease. The high average functionality of the mold material makes it possible to produce patterns relatively finely and rapidly due to the high rate of capillary rise and stiffness, and the low functionality allows for patterns to form on a curved surface with conformal contact. CFMs with different functionality and controllable-interfacial properties will extend the capabilities of capillary force lithography to overcome the geometric limitations of patterning on a scale below 100 nm and micro- and nanopatterning on the curved region. © 2015 American Chemical Society. Source

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