Recent Announcement


New Article in Science Advances

posted Jun 24, 2018, 6:39 PM by Shin-Hyun Kim

Sang Seok Lee, Jong Bin Kim, Yun Ho Kim, and Shin-Hyun Kim, "Wavelength-tunable and shape-reconfigurable photonic capsule resonators containing cholesteric liquid crystals", Science Advances, published online (2018)(Corresponding author) [pdf]

Cholesteric liquid crystals (CLCs) have a photonic bandgap due to the periodic change of refractive index along their helical axes. The CLCs containing optical gain have served as band-edge lasing resonators. In particular, CLCs in a granular format provide omnidirectional lasing, which are promising as a point light source. However, there is no platform that simultaneously achieves high stability in air and wavelength tunability. We encapsulate CLCs with double shells to design a capsule-type laser resonator. The fluidic CLCs are fully enclosed by an aqueous inner shell that promotes the planar alignment of LC molecules along the interface. The outer shell made of silicone elastomer protects the CLC core and the inner shell from the surroundings. Therefore, the helical axes of the CLCs are radially oriented within the capsules, which provide a stable omnidirectional lasing in the air. At the same time, the fluidic CLCs enable the fine-tuning of lasing wavelength with temperature. The capsules retain their double-shell structure during the dynamic deformation. Therefore, the CLCs in the core maintain the planar alignment along the deformed interface, and a lasing direction can be varied from omnidirectional to bi- or multidirectional, depending on the shape of deformed capsules.


New Article in Chemistry of Materials

posted May 9, 2018, 12:59 AM by Shin-Hyun Kim

Gun Ho Lee, Tae Yoon Jeon, Jong Bin Kim, Byungjin Lee, Chang-Soo Lee, Su Yeon Lee, and Shin-Hyun Kim, "Multicompartment Photonic Microcylinders toward Structural Color Inks", Chemistry of Materials, Accepted for publication (2018)(Co-corresponding author)

Structural coloration is promising as an alternative to chemical coloration because it has characteristics of their high color brightness, no fading, and low toxicity. Here, we report a pragmatic micromolding technique to create functional photonic microcylinders which are useful as structural color pigments. Photocurable dispersions of silica particles with interparticle repulsion are molded to spontaneously form regular arrays in confined volumes, which are instantly stabilized by photopolymerization. The resulting photonic microcylinders, released from the mold, exhibit pronounced structural colors from the entire visible range. In addition, multiple compartments can be integrated into single microcylinders through volatile-solvent-mediated sequential molding. As each compartment can be independently rendered to be structurally-colored, transparent, or magneto-responsive, the multicompartment microcylinders show advanced functionalities, such as color-brightness tunability and switchable color properties. These photonic microcylinders will serve as structural color pigments in a wide range of aesthetic coatings and authentication tags.



Jong Bin won a best poster award in Graduate Students Symposium

posted Apr 13, 2018, 6:10 AM by Shin-Hyun Kim

Congrats, Jong Bin!!


Ji-Won won a best oral presentation award in PSK spring meeting!

posted Apr 13, 2018, 6:07 AM by Shin-Hyun Kim

Congrats, Ji-Won!!



New Article in ACS AM&I

posted Feb 21, 2018, 5:49 PM by Shin-Hyun Kim

Chan Ho Park, Sang Min Lee, Ghasidit Pornnoppadol, Yoon Sung Nam, Shin-Hyun Kim, and Bumjoon J. Kim, "Microcapsules Containing pH-Responsive, Fluorescent Polymer-Integrated MoS2: Effective Platform for in-situ pH Sensing and Photothermal Heating", ACS Applied Materials & InterfacesAccepted for publication (2018). (Co-corresponding author, Park and Lee contributed equally)


We report the design of a novel microcapsule platform for in-situ pH sensing and photothermal heating, involving the encapsulation of pH-responsive polymer-coated MoS2 nanosheets (NSs) in microcapsules with an aqueous core and a semipermeable polymeric shell. The MoS2 NSs were functionalized with pH-responsive polymers having fluorescent groups at the distal end to provide pH-sensitive Förster resonance energy transfer (FRET) effect. The pH-responsive polymers were carefully designed to produce a dramatic change in polymer conformation, which translated to a change in FRET efficiency near pH 7.0 in response to subtle pH changes, enabling the detection of cancer cells. The pH-sensitive MoS2 NSs were microfluidically encapsulated within semipermeable membranes to yield microcapsules with uniform size and composition. The microcapsules retained the MoS2 NSs without leakage, while allowing the diffusion of small ions and water through the membrane. At the same time, the membranes excluded adhesive proteins and lipids in the surrounding media, protecting the encapsulated MoS2 NSs from deactivation and enabling in-situ pH monitoring. Moreover, the encapsulated MoS2 NSs showed high-performance photothermal heating, rendering the dual-functional microcapsules highly suitable for cancer diagnosis and treatment.

New paper in Adv. Funct. Mater.

posted Feb 12, 2018, 4:04 PM by Shin-Hyun Kim

HanGyeol Lee, Tae Yoon Jeon, Su Yeon Lee, Seung Yeol Lee, and Shin-Hyun Kim, "Designing Multicolor Micropatterns of Inverse Opals with Photonic Bandgap and Surface Plasmon Resonance", Advanced Functional MaterialsAccepted for publication (2018). (Corresponding author)

Structural coloration provides unique features over chemical coloration, such as non-fading, color tunability, and high color brightness, rendering it useful in various optical applications. To develop the structural colors, two different mechanisms of coloration—photonic bandgap (PBG) and surface plasmon resonance (SPR)—have been separately utilized. In this work, we suggest a new method to create structurally-colored micropatterns by regioselectively employing SPR in a single film of inverse opal with PBG. The inverse opals are prepared by thermal embedding of opal into a negative photoresist and its subsequent removal. The inverse opals have a hexagonal array of open pores on the surface which serves as a template to make SPR-active nanostructures through a directional deposition of gold; perforated gold film and an array of curved gold disks are formed. With a shadow mask lithographically prepared, the gold is regioselectively deposited on the surface of the inverse opal, which results in two distinct regions of gold-free inverse opal with PBG and gold nanostructure with SPR. As PBG and SPR develop their own structural colors respectively, the resultant micropatterns exhibit pronounced dual colors. More importantly, the micropatterns show the distinguished optical response for evaporation of volatile liquids that occupy the pores.


New Article in Lab Chip

posted Feb 5, 2018, 9:37 PM by Shin-Hyun Kim

Hui-Sung Moon,* Kwanghwi Je, Jae-Woong Min, Donghyun Park, Kyung-Yeon Han, Seungho Shin, Woong-Yang Park, Chang Eun Yoo* and Shin-Hyun Kim,* "Inertial-Ordering-Assisted Droplet Microfluidic for High-Throughput Single-Cell RNA-Sequencing", Lab on a ChipAccepted for publication (2018). (Moon & Je contributed equally, Co-corresponding author) [pdf]

Single-cell RNA-seq reveals the cellular heterogeneity inherent in the population of cells, which is very important in many clinical and research applications. Recent advances in droplet microfluidics have achieved the automatic isolation, lysis, and labeling of single cells in droplet compartments without complex instrumentation. However, barcoding errors occurring in the cell encapsulation process because of the multi-beads-in-droplet and insufficient throughput because of the low concentration of beads for avoiding multi-beads-in-a-droplet remain important challenges for precise and efficient expression profiling of single cell. In this study, we developed a new droplet-based microfluidic platform that significantly improved throughput while reducing barcoding error through deterministic encapsulation of inertially ordered beads. Highly concentrated beads containing oligonucleotide barcodes were spontaneously ordered in a spiral channel by an inertial effect, which was in turn encapsulated in droplets one-by-one, while cells were simultaneously encapsulated in the droplets. The deterministic encapsulation of beads resulted in a high fraction of single-bead-in-a-droplet and rare multi-beads-in-a-droplet although the bead concentration increased to 1000 μL-1, which diminished barcoding error and enabled accurate high-throughput barcoding. We successfully validated our device with single-cell RNA-seq. In addition, we found that multi-beads-in-a-droplet, generated using a normal drop-seq device with a high concentration of beads, underestimated transcript numbers and overestimated cell numbers. This accurate high-throughput platform can expand the capability and practicality of Drop-Seq in single-cell analysis.


New paper in Adv. Mater. Technol.

posted Feb 5, 2018, 5:00 PM by Shin-Hyun Kim   [ updated Feb 5, 2018, 5:38 PM ]

Sangmin Lee, Tae Yong Lee, and Shin-Hyun Kim, "Microfluidic Production of Capsules-in-Capsules for Programmed Release of Multiple Ingredients", Advanced Materials TechnologiesAccepted for publication (2018). (Corresponding author)

Capsules with thin shells have a high loading capacity and are thus well-suited containers for reagents that must be stored in confined volumes. Capsules contained in larger capsules, so-called double capsules, allow the encapsulation of distinct reagents within small, defined, well-separated volumes. Therefore, they offer possibilities to initiate reactions in confined volumes and to release distinct bioactives sequentially while minimizing the risk for cross contaminations. Here, we present a new microfluidic capillary device that enables the assembly of water-oil-water-oil-water (W/O/W/O/W) quadruple-emulsion drops whose oil layers are ultra-thin. These quadruple emulsions can be converted into double capsules with thin membranes through either evaporation-induced consolidation of biodegradable polymers or photopolymerization of monomers. We demonstrate that the membrane composition of the inner and outer capsules can be independently selected to enable programmed release of distinct encapsulants. For example, we employ biodegradable polymers with two different degradation rates as the membrane materials that enable sequential release of two different encapsulants. In addition, the release of the encapsulants can be triggered by external stimuli such as osmotic pressure. This new class of double capsules provides new opportunities for drug delivery and screening assays that require sequential release of multiple water-soluble ingredients.


New paper in Adv. Mater. Interfaces

posted Jan 31, 2018, 11:50 PM by Shin-Hyun Kim

Ji-Won Kim, Joon-Seok Lee, and Shin-Hyun Kim, "Biodegradable Inverse Opals with Controlled Discoloration", Advanced Materials InterfacesAccepted for publication (2018). (Corresponding author)

Colloidal crystals and their derivatives possess photonic bandgap property, being useful in various applications, including structural coloration and colorimetric sensing. In this work, we prepare inverse opals with a biodegradable polymer, poly(lactic-co-glycolic acid) (PLGA), to provide a controlled discoloration. To make PLGA inverse opals, a monolayer of silica particles is first deposited on the surface of PLGA film by spin-coating, which is then partially embedded into the film by thermal annealing. Opal is deposited on the monolayer-coated PLGA film by dip-coating, and then embedded into the underlying PLGA film. Selective removal of silica particles leaves behind a face-centered cubic lattice of air cavity in PLGA matrix. The inverse opals whose framework is made of PLGA exhibit a pronounced structural color in dried state. When they are subjected to water, PLGA degrades by hydrolysis of ester groups, which results in the gradual discoloration. The discoloration rate is controllable by varying the pH of surrounding medium and cavity sizes, so that it can act as a colorimetric indicator of valid periods for drugs, foods, and cosmetics. In addition, high biocompatibility and unique optical appearance of PLGA further renders the inverse opals useful as edible anti-counterfeiting materials for valuable drugs.


Our work on SERS-active microgels is selected as 100 R&Ds for 2025

posted Dec 27, 2017, 4:12 PM by Shin-Hyun Kim

Our work on SERS-active microgels is selected as 100 R&Ds for 2025 by the national academy of engineering of Korea (2025년, 대한민국을 이끌 100대 기술과 주역, 한국공학한림원).



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