1
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Park HJ, Kim M, Lee J, Kwak MK. Restoration Temperature Control through Glass Transition Temperature Modulation of Shape Memory Polymer for Thermally Switchable Adhesive. Adv Sci (Weinh) 2024:e2309393. [PMID: 38704689 DOI: 10.1002/advs.202309393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2023] [Revised: 02/26/2024] [Indexed: 05/07/2024]
Abstract
Shape memory polymers (SMPs) undergo changes between arbitrary shapes and programmed shapes upon exposure to specific stimulus, allowing them to restore their original shape. All kinds of external stimuli have a threshold to change the shape of the SMP. Especially, for the thermal type SMP, the critical temperature for shape restoration is typically near the glass transition temperature (Tg). In this study, the controllability of the restoration temperature is analyzed by adjusting the Tg of the polymer using Norland Optical Adhesive 63, which can be cured with UV irradiation. By varying the ambient temperature from 20 to 120 °C during UV exposure, Tg changes ranging from 35.84 to 50.50 °C are obtained, with corresponding changes in restoration temperature. As a practical application, a thermal-activated SMP dry adhesive is developed with programmable Tg and switchable adhesion. The fabricated SMP dry adhesive exhibited strong adhesion to substrates with various surface roughness. Additionally, the shape memory effect allowed for easy detachment through shape recovery, and different adhesive performances at different temperatures are achieved by programming various Tg values. Moreover, the simple manufacturing process of the SMP dry adhesive is confirmed to be suitable for continuous fabrication processes based on roll-to-roll methods.
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Affiliation(s)
- Han Jun Park
- Department of Mechanical Engineering, Kyungpook National University, Daegu, 41566, Republic of Korea
| | - Minsu Kim
- Department of Mechanical Engineering, Kyungpook National University, Daegu, 41566, Republic of Korea
| | - Jihoon Lee
- Department of Mechanical Engineering, Kyungpook National University, Daegu, 41566, Republic of Korea
| | - Moon Kyu Kwak
- Department of Mechanical Engineering, Kyungpook National University, Daegu, 41566, Republic of Korea
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2
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Choi S, Kang B, Yang E, Kim K, Kwak MK, Chang PS, Jung HS. Author Correction: Precise control of liposome size using characteristic time depends on solvent type and membrane properties. Sci Rep 2024; 14:5331. [PMID: 38438475 PMCID: PMC10912658 DOI: 10.1038/s41598-024-55878-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/06/2024] Open
Affiliation(s)
- Sunghak Choi
- Center for Food and Bioconvergence, Department of Food Science and Biotechnology, Seoul National University, Seoul, 08826, South Korea
| | - Bongsu Kang
- Center for Food and Bioconvergence, Department of Food Science and Biotechnology, Seoul National University, Seoul, 08826, South Korea
- School of Mechanical Engineering, Kyungpook National University, Daegu, 41566, South Korea
| | - Eunhye Yang
- Department of Agricultural Biotechnology, Seoul National University, Seoul, 08826, Republic of Korea
| | - Keesung Kim
- Research Inst. of Advanced. Materials, Collage of Engineering, Seoul National University, Seoul, 08826, South Korea
| | - Moon Kyu Kwak
- School of Mechanical Engineering, Kyungpook National University, Daegu, 41566, South Korea.
| | - Pahn-Shick Chang
- Center for Food and Bioconvergence, Department of Food Science and Biotechnology, Seoul National University, Seoul, 08826, South Korea.
- Department of Agricultural Biotechnology, Seoul National University, Seoul, 08826, Republic of Korea.
- Center for Agricultural Microorganism and Enzyme, Seoul National University, Seoul, 08826, Republic of Korea.
- Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul, 08826, Republic of Korea.
| | - Ho-Sup Jung
- Center for Food and Bioconvergence, Department of Food Science and Biotechnology, Seoul National University, Seoul, 08826, South Korea.
- Nbiocell Inc, Siheung SNU Start-up Campus, Gyeonggi-do, 15011, Republic of Korea.
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3
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Yoo SH, Kim M, Park HJ, Lee GI, Lee SH, Kwak MK. Vacuum-powered soft actuator with oblique air chambers for easy detachment of artificial dry adhesive by coupled contraction and twisting. Sci Technol Adv Mater 2023; 24:2274818. [PMID: 38024796 PMCID: PMC10653703 DOI: 10.1080/14686996.2023.2274818] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/22/2023] [Accepted: 10/19/2023] [Indexed: 12/01/2023]
Abstract
A gecko foot-inspired, mushroom-shaped artificial dry adhesive exploiting intermolecular forces between microstructure and surface has drawn research attention for its strong adhesive force. However, the high pull-off strength corresponding to the adhesive force matters when detaching fragile substrates. In this study, we report a vacuum-powered soft actuator having oblique air chambers and a dry adhesive. The soft actuator performs coupled contraction and twisting by applying negative pneumatic pressure inward and exhibits not only high pull-off strength but also easy detachment. This effective detachment can be achieved thanks to the twisting motion of the soft actuator. The detachment performances of the actuator models are assessed using a 6-degrees-of-freedom robot arm. Results show that the soft actuators exhibit remarkable pull-off strength decrement from ~20 N cm-2 to ~2 N cm-2 due to the twisting. Finally, to verify a feasible application of this study, we utilize the inherent compliance of the actuators and introduce a glass transfer system for which a glass substrate on a slope is gripped by the flexibility of the soft actuators and delivered to the destination without any fracture.
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Affiliation(s)
- Seung Hoon Yoo
- Department of Mechanical Engineering, Kyungpook National University, Daegu, Republic of Korea
| | - Minsu Kim
- Department of Mechanical Engineering, Kyungpook National University, Daegu, Republic of Korea
| | - Han Jun Park
- Department of Mechanical Engineering, Kyungpook National University, Daegu, Republic of Korea
| | - Ga In Lee
- Department of Mechanical Engineering, Kyungpook National University, Daegu, Republic of Korea
| | - Sung Ho Lee
- Department of Mechanical Engineering, Dong-A University, Busan, Republic of Korea
| | - Moon Kyu Kwak
- Department of Mechanical Engineering, Kyungpook National University, Daegu, Republic of Korea
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4
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Han I, Song J, Kim K, Kim H, Son H, Kim M, Lee U, Choi K, Ji H, Lee SH, Kwak MK, Ok JG. Demonstration of a roll-to-roll-configurable, all-solution-based progressive assembly of flexible transducer devices consisting of functional nanowires on micropatterned electrodes. Sci Rep 2023; 13:11980. [PMID: 37488145 PMCID: PMC10366188 DOI: 10.1038/s41598-023-38635-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Accepted: 07/12/2023] [Indexed: 07/26/2023] Open
Abstract
We demonstrate continuous fabrication of flexible transducer devices consisting of interdigitated (IDT) Ag microelectrodes interconnected by ZnO nanowires (ZNWs), created via serially connected solution-processable micro- and nanofabrication processes. On an Ag layer obtainable from the mild thermal reduction of an ionic Ag ink coating, the roll-to-roll-driven photolithography process [termed photo roll lithography (PRL)] followed by wet-etching can be applied to continuously define the IDT microelectrode structure. Conformal ZNWs can then be grown selectively on the Ag electrodes to interconnect them via an Ag-mediated hydrothermal ZNW growth that does not require high-temperature seed sintering. Given that all of these constitutive processes are vacuum-free and solution-processable at a low temperature, and are compatible with continuous processing onto flexible substrates, they can be eventually configured into the roll-to-roll-processable progressive assembly. Through parametric optimizations of processes consisting of the roll-to-roll-configurable, solution-based progressive assembly of nanostructures (ROLSPAN), a flexible transducer consisting of ZNW-interconnected, PRL-ed IDT Ag electrodes can be developed. This flexible architecture faithfully performs UV sensing as well as optoelectronic transduction. The ROLSPAN concept along with its specific applicability to flexible devices may inspire many diverse functional systems requiring high-throughput low-temperature fabrication over large-area flexible substrates.
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Affiliation(s)
- Inhui Han
- Department of Mechanical and Automotive Engineering, Seoul National University of Science and Technology, 232 Gongneung-Ro, Nowon-Gu, Seoul, 01811, Republic of Korea
| | - Jungkeun Song
- Department of Mechanical and Automotive Engineering, Seoul National University of Science and Technology, 232 Gongneung-Ro, Nowon-Gu, Seoul, 01811, Republic of Korea
| | - Kwangjun Kim
- Department of Mechanical and Automotive Engineering, Seoul National University of Science and Technology, 232 Gongneung-Ro, Nowon-Gu, Seoul, 01811, Republic of Korea
| | - Hyein Kim
- Department of Mechanical and Automotive Engineering, Seoul National University of Science and Technology, 232 Gongneung-Ro, Nowon-Gu, Seoul, 01811, Republic of Korea
| | - Hyunji Son
- Department of Mechanical and Automotive Engineering, Seoul National University of Science and Technology, 232 Gongneung-Ro, Nowon-Gu, Seoul, 01811, Republic of Korea
| | - Minwook Kim
- Department of Mechanical and Automotive Engineering, Seoul National University of Science and Technology, 232 Gongneung-Ro, Nowon-Gu, Seoul, 01811, Republic of Korea
| | - Useung Lee
- Department of Mechanical and Automotive Engineering, Seoul National University of Science and Technology, 232 Gongneung-Ro, Nowon-Gu, Seoul, 01811, Republic of Korea
| | - Kwangjin Choi
- Department of Mechanical and Automotive Engineering, Seoul National University of Science and Technology, 232 Gongneung-Ro, Nowon-Gu, Seoul, 01811, Republic of Korea
| | - Hojae Ji
- Department of Mechanical and Automotive Engineering, Seoul National University of Science and Technology, 232 Gongneung-Ro, Nowon-Gu, Seoul, 01811, Republic of Korea
| | - Sung Ho Lee
- Department of Mechanical Engineering, Dong-A University, 37 Nakdong-Daero 550-Gil, Saha-Gu, Busan, 49315, Republic of Korea.
| | - Moon Kyu Kwak
- School of Mechanical Engineering, Kyungpook National University, 80 Daehak-Ro, Buk-Gu, Daegu, 41566, Republic of Korea.
- Ncoretechnology Inc., 80 Daehak-Ro, Buk-Gu, Daegu, 41566, Republic of Korea.
| | - Jong G Ok
- Department of Mechanical and Automotive Engineering, Seoul National University of Science and Technology, 232 Gongneung-Ro, Nowon-Gu, Seoul, 01811, Republic of Korea.
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5
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Choi S, Kang B, Yang E, Kim K, Kwak MK, Chang PS, Jung HS. Precise control of liposome size using characteristic time depends on solvent type and membrane properties. Sci Rep 2023; 13:4728. [PMID: 36959258 PMCID: PMC10036480 DOI: 10.1038/s41598-023-31895-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Accepted: 03/20/2023] [Indexed: 03/25/2023] Open
Abstract
Controlling the sizes of liposomes is critical in drug delivery systems because it directly influences their cellular uptake, transportation, and accumulation behavior. Although hydrodynamic focusing has frequently been employed when synthesizing nano-sized liposomes, little is known regarding how flow characteristics determine liposome formation. Here, various sizes of homogeneous liposomes (50-400 nm) were prepared according to flow rate ratios in two solvents, ethanol, and isopropyl alcohol (IPA). Relatively small liposomes formed in ethanol due to its low viscosity and high diffusivity, whereas larger, more poly-dispersed liposomes formed when using IPA as a solvent. This difference was investigated via numerical simulations using the characteristic time factor to predict the liposome size; this approach was also used to examine the flow characteristics inside the microfluidic channel. In case of the liposomes, the membrane rigidity also has a critical role in determining their size. The increased viscosity and packing density of the membrane by addition of cholesterol confirmed by fluorescence anisotropy and polarity lead to increase in liposome size (40-530 nm). However, the interposition of short-chain lipids de-aligned the bilayer membrane, leading to its degradation; this decreased the liposome size. Adding short-chain lipids linearly decreased the liposome size (130-230 nm), but at a shallower gradient than that of cholesterol. This analytical study expands the understanding of microfluidic environment in the liposome synthesis by offering design parameters and their relation to the size of liposomes.
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Affiliation(s)
- Sunghak Choi
- Center for Food and Bioconvergence, Department of Food Science and Biotechnology, Seoul National University, Seoul, 08826, South Korea
| | - Bongsu Kang
- Center for Food and Bioconvergence, Department of Food Science and Biotechnology, Seoul National University, Seoul, 08826, South Korea
- School of Mechanical Engineering, Kyungpook National University, Daegu, 41566, South Korea
| | - Eunhye Yang
- Department of Agricultural Biotechnology, Seoul National University, Seoul, 08826, Republic of Korea
| | - Keesung Kim
- Research Inst. of Advanced. Materials, Collage of Engineering, Seoul National University, Seoul, 08826, South Korea
| | - Moon Kyu Kwak
- School of Mechanical Engineering, Kyungpook National University, Daegu, 41566, South Korea.
| | - Pahn-Shick Chang
- Center for Food and Bioconvergence, Department of Food Science and Biotechnology, Seoul National University, Seoul, 08826, South Korea.
- Department of Agricultural Biotechnology, Seoul National University, Seoul, 08826, Republic of Korea.
- Center for Agricultural Microorganism and Enzyme, Seoul National University, Seoul, 08826, Republic of Korea.
- Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul, 08826, Republic of Korea.
| | - Ho-Sup Jung
- Center for Food and Bioconvergence, Department of Food Science and Biotechnology, Seoul National University, Seoul, 08826, South Korea.
- Nbiocell Inc, Siheung SNU Start-up Campus, Gyeonggi-do, 15011, Republic of Korea.
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6
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Kim M, Yoo S, Jeong HE, Kwak MK. Fabrication of Salvinia-inspired surfaces for hydrodynamic drag reduction by capillary-force-induced clustering. Nat Commun 2022; 13:5181. [PMID: 36056031 PMCID: PMC9440115 DOI: 10.1038/s41467-022-32919-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Accepted: 08/23/2022] [Indexed: 11/09/2022] Open
Abstract
For decades, bioinspired functional materials have been attracting the interest of many researchers for their remarkable characteristics. In particular, some plant leaves are well known for their inherent superhydrophobic nature. Salvinia molesta, a free-floating aquatic fern, has egg-beater-shaped hierarchical trichomes on its surface of leaves. Due to the unique structure and complex wettability of the hairs, this plant has the ability to maintain a stable thick air layer upon the structure when it is submerged underwater. Often referred to as the “Salvinia Effect,” this property is expected to be suitable for use in hydrodynamic drag reduction. However, due to the complex shape of the trichome, currently applied fabrication methods are using a three-dimensional printing system, which is not applicable to mass production because of its severely limited productivity. In this work, artificial Salvinia leaf inspired by S. molesta was fabricated using a conventional soft lithography method assisted with capillary-force-induced clustering of micropillar array. The fabrication method suggested in this work proposes a promising strategy for the manufacturing of Salvinia-inspired hydrodynamic drag reduction surfaces. Salvinia molesta plant has the ability to maintain a stable air layer when submerged underwater due to its specific form. The authors propose here a soft lithography fabrication method of artificial Salvinia leaf assisted with capillary-force induced clustering of micropillar array, for hydrodynamic drag reduction.
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Affiliation(s)
- Minsu Kim
- Department of Mechanical Engineering, Kyungpook National University, Daegu, 41566, Republic of Korea
| | - Seunghoon Yoo
- Department of Mechanical Engineering, Kyungpook National University, Daegu, 41566, Republic of Korea
| | - Hoon Eui Jeong
- Department of Mechanical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, Republic of Korea
| | - Moon Kyu Kwak
- Department of Mechanical Engineering, Kyungpook National University, Daegu, 41566, Republic of Korea.
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7
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Kang M, Seong M, Lee D, Kang SM, Kwak MK, Jeong HE. Self-Assembled Artificial Nanocilia Actuators. Adv Mater 2022; 34:e2200185. [PMID: 35417603 DOI: 10.1002/adma.202200185] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2022] [Revised: 03/17/2022] [Indexed: 06/14/2023]
Abstract
Self-assembly of nanoparticles (NPs) is a powerful route to constructing higher-order structures. However, the programmed self-assembly of NPs into non-close-packed, 3D, shape-morphing nanocilia arrays remains elusive, whereas dynamically actuated nanometer cilia are universal in living systems. Here, a programmable self-assembly strategy is presented that can direct magnetic NPs into a highly ordered responsive artificial nanocilia actuator with exquisite nanometer 3D structural arrangements. The self-assembled artificial NP cilia can maintain their structural integrity through the interplay of interparticle interactions. Interestingly, the nanocilia can exhibit a field-responsive actuation motion through "rolling and sliding" between assembled NPs rather than bending the entire ciliary beam. It is demonstrated that oleic acid coated over the NPs acts as a lubricating bearing and enables the rolling/sliding-based actuation of the cilia.
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Affiliation(s)
- Minsu Kang
- Department of Mechanical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, Republic of Korea
| | - Minho Seong
- Department of Mechanical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, Republic of Korea
| | - Donghyuk Lee
- Department of Mechanical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, Republic of Korea
| | - Seong Min Kang
- Department of Mechanical Engineering, Chungnam National University, Daejeon, 34134, Republic of Korea
| | - Moon Kyu Kwak
- Department of Mechanical Engineering, Kyungpook National University, Daegu, 41566, Republic of Korea
| | - Hoon Eui Jeong
- Department of Mechanical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, Republic of Korea
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8
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Lee SH, Kang BS, Kwak MK. Magneto-Responsive Actuating Surfaces with Controlled Wettability and Optical Transmittance. ACS Appl Mater Interfaces 2022; 14:14721-14728. [PMID: 35289610 DOI: 10.1021/acsami.1c24556] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The wettability of surfaces can be manipulated using actuating micro/nanostructures, as in the manipulation of water droplets with magnetic forces. Controlling water droplets with magneto-responsive surfaces is limited to optical applications, however, because these surfaces are normally opaque. Herein, we introduce a magneto-responsive actuating surface that is capable of controlling not only the wettability but also the optical transmittance. The magneto-responsive actuating surface is fabricated using a composite of iron particles with polydimethylsiloxane (PDMS). Thanks to the elastic properties of PDMS, fabricated microstructures' bending is induced by applying magnetic force. Therefore, the static/dynamic water contact angle and the optical transmittance can be controlled. Furthermore, as a feasible application, a sliding angle control system that depends on the magnet location is implemented. On the basis of the interesting characteristics of not only wettability but also optical transmittance, this study is expected to be widely used in various fields such as optics, surface self-cleaning systems of solar cells, and smart windows.
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Affiliation(s)
- Sung Ho Lee
- Department of Electrical Electronics and Computer Science, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Bong Su Kang
- Department of Mechanical Engineering, Kyungpook National University, Daegu 41566, Republic of Korea
| | - Moon Kyu Kwak
- Department of Mechanical Engineering, Kyungpook National University, Daegu 41566, Republic of Korea
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9
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Lee SH, Song HW, Park HJ, Kwak MK. Surface Adaptable and Adhesion Controllable Dry Adhesive with Shape Memory Polymer. Macromol Rapid Commun 2022; 43:e2200012. [PMID: 35132723 DOI: 10.1002/marc.202200012] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Revised: 02/01/2022] [Indexed: 11/08/2022]
Abstract
Gecko foot consist of numerous micro/nano hierarchical hairs and exhibit a high adhesion onto various surfaces by the "van der Waals force". The gecko, despite its mighty adhesion, can travel efficiently with a rapid adhesion switching given that the end of hair in the gecko foot is slanted in one direction. Herein, we report a shape memory polymer (SMP)-based switchable dry adhesive (SSA), inspired by gecko foot, having tremendous surface adaptability and adhesion switching capability. The SSA shows not only high adhesion to the various surfaces (approximately 332.8 kPa) but also easy detachment (nearly 3.73 kPa) due to the characteristic of SMP, which can reversibly recover from a deformed shape to its initial shape. On the basis of the novel adhesion switching property, we suggest the SSA-applied advanced glass transfer system as a feasible application. This experiment confirms that an ultra-thin and light glass film is transferred easily and sustainably, and we believe that the SSA might be a breakthrough and a powerful alternative for not only conventional dry adhesive but also the next-level transfer systems. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Sung Ho Lee
- Department of Electrical Electronics and Computer Science, University of Michigan, Ann Arbor, 48109, United States
| | - Hyun Woo Song
- Department of Mechanical Engineering, Kyungpook National University, Daegu, 41566, Republic of Korea
| | - Han Jun Park
- Department of Mechanical Engineering, Kyungpook National University, Daegu, 41566, Republic of Korea
| | - Moon Kyu Kwak
- Department of Mechanical Engineering, Kyungpook National University, Daegu, 41566, Republic of Korea
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10
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Choi S, Kang B, Taguchi S, Umakoshi H, Kim K, Kwak MK, Jung HS. A Simple Method for Continuous Synthesis of Bicelles in Microfluidic Systems. Langmuir 2021; 37:12255-12262. [PMID: 34645269 DOI: 10.1021/acs.langmuir.1c02024] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Bicelle has great potential for drug delivery systems due to its small size and biocompatibility. The conventional method of bicelle preparation contains a long process and harsh conditions, which limit its feasibility and damage the biological substances. For these reasons, a continuous manufacturing method in mild conditions has been demanded. Here, we propose a novel method for DMPC/DHPC bicelle synthesis based on a microfluidic device without heating and freezing processes. Bicelles were successfully prepared using this continuous method, which was identified by the physicochemical properties and morphologies of the synthesized assemblies. Experimental and analytical studies confirm that there is critical lipid concentration and critical mixing time for bicelle synthesis in this microfluidic system. Furthermore, a linear relation between the actual composition of bicelle and initial lipid ratio is deduced, and this enables the size of bicelles to be controlled.
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Affiliation(s)
- Sunghak Choi
- Center for Food and Bioconvergence, Department of Food Science and Biotechnology, Seoul National University, Seoul 08826, South Korea
| | - Bongsu Kang
- School of Mechanical Engineering, Kyungpook National University, Daegu 41566, South Korea
| | - Shogo Taguchi
- Department of Chemical Engineering and Materials Science, Graduate School of Engineering, University of Hyogo, 2167 Shosha, Himeji, Hyogo 671-2280, Japan
| | - Hiroshi Umakoshi
- Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama-cho, Toyonaka, Osaka 560-8531, Japan
| | - Keesung Kim
- Research Institute of Advanced Materials, College of Engineering, Seoul National University, Seoul 08826, South Korea
| | - Moon Kyu Kwak
- School of Mechanical Engineering, Kyungpook National University, Daegu 41566, South Korea
| | - Ho-Sup Jung
- Center for Food and Bioconvergence, Department of Food Science and Biotechnology, Seoul National University, Seoul 08826, South Korea
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11
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Kang B, Choi S, Kim K, Jung HS, Kwak MK. Precise Microfluidic Luminescent Sensor Platform with Controlled Injection System. ACS Omega 2021; 6:23412-23420. [PMID: 34549140 PMCID: PMC8444323 DOI: 10.1021/acsomega.1c03347] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/26/2021] [Accepted: 08/18/2021] [Indexed: 06/13/2023]
Abstract
Efforts have been devoted to screening various prevalent diseases, such as severe acute respiratory syndrome (SARS) and coronavirus disease 2019 (COVID-19). Real-time polymerase chain reaction (RT-PCR), which is currently the most widely used, has high accuracy, but it requires several facilities and takes a relatively long time to check; so, new testing technology is necessary for a higher test efficiency. A chemiluminescence (CL) sensor is a relatively simple device and suitable as an alternative because it can detect very precise specimens. However, in measurements via CL, the quantitative formulation of reagents that cause color development is important. In the case of mixing using micropipettes, precise analysis is possible, but this technique is limited by uncontrollable errors or deviations in detection amounts. In addition, in using a microfluidic chip to increase field applicability, a syringe pump or other quantification injection tools are required, so problems must be overcome for practical use. Therefore, in this study, a microchip was designed and manufactured to supply a sample of a certain volume by simply blowing air and injecting a sample into the chamber. By utilizing the luminescence reaction of luminol, CuSO4 and H2O2 the performance of the prepared chip was confirmed, and the desired amount of the sample could be injected with a simple device with an error rate of 2% or less. For feasible applications, an experiment was performed to quantitatively analyze thrombin, a biomarker of heart disease. Results demonstrated that biomarkers could be more precisely detected using the proposed microchips than using micropipettes.
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Affiliation(s)
- Bongsu Kang
- School
of Mechanical Engineering, Kyungpook National
University, Daegu 41566, South Korea
| | - Sunghak Choi
- Center
for Food and Bioconvergence, Department of Food Science and Biotechnology, Seoul National University, Seoul 08826, South
Korea
| | - Keesung Kim
- Research
Inst. of Advanced Materials, College of Engineering, Seoul National University, Seoul 08826, South Korea
| | - Ho-Sup Jung
- Center
for Food and Bioconvergence, Department of Food Science and Biotechnology, Seoul National University, Seoul 08826, South
Korea
| | - Moon Kyu Kwak
- School
of Mechanical Engineering, Kyungpook National
University, Daegu 41566, South Korea
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12
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Lee SH, Kang BS, Kim GM, Roh YR, Kwak MK. Fabrication and Performance Evaluation of the Helmholtz Resonator Inspired Acoustic Absorber Using Various Materials. Micromachines (Basel) 2020; 11:mi11110983. [PMID: 33142730 PMCID: PMC7692332 DOI: 10.3390/mi11110983] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Revised: 10/24/2020] [Accepted: 10/30/2020] [Indexed: 12/05/2022]
Abstract
A soundwave is transmitted by adjacent molecules in the medium, and depending on the type of sound, it exhibits various characteristics such as frequency, sound pressure, etc. If the acoustic wavelength of the soundwave is sufficiently long compared with the size of an acoustic element, physical analysis within the sound element could be simplified regardless of the shape of the acoustic element: this is called “long wavelength approximation”. A Helmholtz resonator, a representative acoustic element which satisfies the “long wavelength theory”, consists of a neck part and a cavity part. The Helmholtz resonators can absorb certain frequencies of sound through resonance. To exhibit attenuation properties at ultrasound range, the Helmholtz resonator should be made into a microscale since Helmholtz resonators should satisfy the “long wavelength approximation”. In this study, Helmholtz resonator inspired acoustic elements were fabricated using MEMS technology, and acoustic attenuation experiments in a water bath were conducted using various shapes and materials. As a result, the fabricated samples showed admirable attenuation properties up to ~13 dB mm−1 at 1 MHz. The results were analyzed to derive the necessary conditions for the fabrication of acoustic elements with acoustic attenuation properties in ultrasound range.
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13
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Kim M, Hwang I, Seong M, Choi J, Kim M, Lee HD, Shin KJ, Son H, Sohn H, Choi J, Jeong HE, Kwak MK. Multifunctional Smart Ball Sensor for Wireless Structural Health Monitoring in a Fire Situation. Sensors (Basel) 2020; 20:s20154328. [PMID: 32756512 PMCID: PMC7435786 DOI: 10.3390/s20154328] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 07/29/2020] [Accepted: 08/01/2020] [Indexed: 11/16/2022]
Abstract
A variety of sensor systems have been developed to monitor the structural health status of buildings and infrastructures. However, most sensor systems for structural health monitoring (SHM) are difficult to use in extreme conditions, such as a fire situation, because of their vulnerability to high temperature and physical shocks, as well as time-consuming installation process. Here, we present a smart ball sensor (SBS) that can be immediately installed on surfaces of structures, stably measure vital SHM data in real time and wirelessly transmit the data in a high-temperature fire situation. The smart ball sensor mainly consists of sensor and data transmission module, heat insulator and adhesive module. With the integrated device configuration, the SBS can be strongly attached to the target surface with maximum adhesion force of 233.7-N and stably detect acceleration and temperature of the structure without damaging the key modules of the systems even at high temperatures of up to 500 °C while ensuring wireless transmission of the data. Field tests for a model pre-engineered building (PEB) structure demonstrate the validity of the smart ball sensor as an instantly deployable, high-temperature SHM system. This SBS can be used for SHM of a wider variety of structures and buildings beyond PEB structures.
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Affiliation(s)
- Minsu Kim
- Department of Mechanical Engineering, Kyungpook National University, Daegu 41566, Korea; (M.K.); (M.K.K.)
| | - Insol Hwang
- Department of Mechanical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Korea; (I.H.); (M.S.); (M.K.); (H.S.)
| | - Minho Seong
- Department of Mechanical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Korea; (I.H.); (M.S.); (M.K.); (H.S.)
| | - Jaemook Choi
- Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea; (J.C.); (H.S.)
| | - Myunggun Kim
- Department of Mechanical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Korea; (I.H.); (M.S.); (M.K.); (H.S.)
| | - Hee-Du Lee
- Department of Architectural Engineering, Kyungpook National University, Daegu 41566, Korea; (H.-D.L.); (K.-J.S.)
| | - Kyung-Jae Shin
- Department of Architectural Engineering, Kyungpook National University, Daegu 41566, Korea; (H.-D.L.); (K.-J.S.)
| | - Hungsun Son
- Department of Mechanical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Korea; (I.H.); (M.S.); (M.K.); (H.S.)
| | - Hoon Sohn
- Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea; (J.C.); (H.S.)
| | - Junho Choi
- Department of Fire Protection Engineering, Pukyong National University, Busan 48513, Korea
- Correspondence: (J.C.); (H.E.J.)
| | - Hoon Eui Jeong
- Department of Mechanical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Korea; (I.H.); (M.S.); (M.K.); (H.S.)
- Correspondence: (J.C.); (H.E.J.)
| | - Moon Kyu Kwak
- Department of Mechanical Engineering, Kyungpook National University, Daegu 41566, Korea; (M.K.); (M.K.K.)
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Baek SH, Song HW, Lee S, Kim JE, Kim YH, Wi JS, Ok JG, Park JS, Hong S, Kwak MK, Lee HJ, Nam SW. Gold Nanoparticle-Enhanced and Roll-to-Roll Nanoimprinted LSPR Platform for Detecting Interleukin-10. Front Chem 2020; 8:285. [PMID: 32528922 PMCID: PMC7264386 DOI: 10.3389/fchem.2020.00285] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2019] [Accepted: 03/23/2020] [Indexed: 12/18/2022] Open
Abstract
Localized surface plasmon resonance (LSPR) is a powerful platform for detecting biomolecules including proteins, nucleotides, and vesicles. Here, we report a colloidal gold (Au) nanoparticle-based assay that enhances the LSPR signal of nanoimprinted Au strips. The binding of the colloidal Au nanoparticle on the Au strip causes a red-shift of the LSPR extinction peak, enabling the detection of interleukin-10 (IL-10) cytokine. For LSPR sensor fabrication, we employed a roll-to-roll nanoimprinting process to create nanograting structures on polyethylene terephthalate (PET) film. By the angled deposition of Au on the PET film, we demonstrated a double-bent Au structure with a strong LSPR extinction peak at ~760 nm. Using the Au LSPR sensor, we developed an enzyme-linked immunosorbent assay (ELISA) protocol by forming a sandwich structure of IL-10 capture antibody/IL-10/IL-10 detection antibody. To enhance the LSPR signal, we introduced colloidal Au nanocube (AuNC) to be cross-linked with IL-10 detection antibody for immunogold assay. Using IL-10 as a model protein, we successfully achieved nanomolar sensitivity. We confirmed that the shift of the extinction peak was improved by 450% due to plasmon coupling between AuNC and Au strip. We expect that the AuNC-assisted LSPR sensor platform can be utilized as a diagnostic tool by providing convenient and fast detection of the LSPR signal.
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Affiliation(s)
- Seung Hee Baek
- Department of Molecular Medicine, School of Medicine, Kyungpook National University, Daegu, South Korea
| | - Hyun Woo Song
- Department of Mechanical Engineering, School of Mechanical Engineering, Kyungpook National University, Daegu, South Korea
| | - Sunwoong Lee
- Department of Molecular Medicine, School of Medicine, Kyungpook National University, Daegu, South Korea
| | - Jung-Eun Kim
- Department of Molecular Medicine, School of Medicine, Kyungpook National University, Daegu, South Korea
| | - Yeo Hyang Kim
- Department of Pediatrics, School of Medicine, Kyungpook National University, Daegu, South Korea
| | - Jung-Sub Wi
- Center for Nano-Bio Measurement, Korea Research Institute of Standards and Science, Daejeon, South Korea
| | - Jong G Ok
- Department of Mechanical and Automotive Engineering, Seoul National University of Science and Technology, Seoul, South Korea
| | - Jun Seok Park
- Department of Surgery, School of Medicine, Kyungpook National University, Daegu, South Korea
| | - Seonki Hong
- Department of Emerging Materials Science, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, South Korea
| | - Moon Kyu Kwak
- Department of Mechanical Engineering, School of Mechanical Engineering, Kyungpook National University, Daegu, South Korea
| | - Hye Jin Lee
- Department of Chemistry and Green Nano Materials Research Center, Kyungpook National University, Daegu, South Korea
| | - Sung-Wook Nam
- Department of Molecular Medicine, School of Medicine, Kyungpook National University, Daegu, South Korea
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Abstract
The remoras are marine species that can effectively move by clinging onto other marine species via a suction disk on their dorsal side, which is composed of complex structures. The inner suction disk could be divided into three large parts, namely, lip, lamella, and spinule. The lamella is deformed actively to generate pressure difference between the inside and outside of the suction disk, and the lip maintains the sealing. The spinule, which is composed of hairs with diameter of 300 μm or less hair, enhances the frictional force. In this study, we easily fabricated polymer-based adhesive inspired by the suction disk of the remora and conducted an experiment to determine its performance. The adhesive exhibited admirable performance with a 26.68 N cm-2 (266.8 kPa) pull-off strength and a 19.42 N cm-2 (194.2 kPa) shear strength in water. The durability test result indicated that the adhesion and friction characteristics of the adhesive were well maintained even after multiple uses.
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Affiliation(s)
- Sung Ho Lee
- Department of Mechanical Engineering , Kyungpook National University , Daegu 41566 , Republic of Korea
| | - Hyun Woo Song
- Department of Mechanical Engineering , Kyungpook National University , Daegu 41566 , Republic of Korea
| | - Bong Su Kang
- Department of Mechanical Engineering , Kyungpook National University , Daegu 41566 , Republic of Korea
| | - Moon Kyu Kwak
- Department of Mechanical Engineering , Kyungpook National University , Daegu 41566 , Republic of Korea
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Kwak MK, Lee EJ, Park JW, Park SY, Kim BJ, Kim TH, Suh K, Koh JM, Lee SH, Byun DW. Correction to: CD4 T cell count is positively associated with lumbar spine bone mass in HIV-infected men under the age of 50 years. Osteoporos Int 2019; 30:2363. [PMID: 31506788 DOI: 10.1007/s00198-019-05115-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Two sentences in the Discussion section were incorrect.
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Affiliation(s)
- M K Kwak
- Division of Endocrinology and Metabolism, Asan Medical Center, University of Ulsan College of Medicine, 88 Olympic-ro 43-gil, Songpa-gu, Seoul, 05505, South Korea
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Soonchunhyang University Hospital, University College of Medicine, Soonchunhyang, Seoul, 04401, South Korea
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Hallym University Dongtan Sacred Heart Hospital, 7, Keunjaebong-gil, Hwaseong-Si, Gyeonggi-Do, 18450, South Korea
| | - E J Lee
- Division of Infectious Diseases, Department of Internal Medicine, College of Medicine, Soonchunhyang University Hospital, Soonchunhyang University, 59 Daesagwan-ro, Yongsan-gu, Seoul, 04401, South Korea
| | - J W Park
- Division of Infectious Diseases, Department of Internal Medicine, Soonchunhyang University Cheonan Hospital, Soonchunhyang, University College of Medicine, 31 Suncheonhyang 6-gil, Dongnam-gu, Cheonan-si, Chungcheongnam-do, 31151, South Korea
| | - S Y Park
- Division of Infectious Diseases, Department of Internal Medicine, College of Medicine, Soonchunhyang University Hospital, Soonchunhyang University, 59 Daesagwan-ro, Yongsan-gu, Seoul, 04401, South Korea
| | - B-J Kim
- Division of Endocrinology and Metabolism, Asan Medical Center, University of Ulsan College of Medicine, 88 Olympic-ro 43-gil, Songpa-gu, Seoul, 05505, South Korea
| | - T H Kim
- Division of Infectious Diseases, Department of Internal Medicine, College of Medicine, Soonchunhyang University Hospital, Soonchunhyang University, 59 Daesagwan-ro, Yongsan-gu, Seoul, 04401, South Korea
| | - K Suh
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Soonchunhyang University Hospital, University College of Medicine, Soonchunhyang, Seoul, 04401, South Korea
| | - J-M Koh
- Division of Endocrinology and Metabolism, Asan Medical Center, University of Ulsan College of Medicine, 88 Olympic-ro 43-gil, Songpa-gu, Seoul, 05505, South Korea
| | - S H Lee
- Division of Endocrinology and Metabolism, Asan Medical Center, University of Ulsan College of Medicine, 88 Olympic-ro 43-gil, Songpa-gu, Seoul, 05505, South Korea.
| | - D-W Byun
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Soonchunhyang University Hospital, University College of Medicine, Soonchunhyang, Seoul, 04401, South Korea.
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Park JB, Lee KH, Han SH, Chung TH, Kwak MK, Rho H, Jeong T, Ha JS. Stable and efficient transfer-printing including repair using a GaN-based microscale light-emitting diode array for deformable displays. Sci Rep 2019; 9:11551. [PMID: 31399605 PMCID: PMC6689111 DOI: 10.1038/s41598-019-47449-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Accepted: 06/05/2019] [Indexed: 11/16/2022] Open
Abstract
GaN-based microscale light-emitting diodes (μLEDs) are reported for assembly into deformable displays and repair systems. A stamp-imprinting method that enables large area assembly without spatial limitation is involved in the system, and a selective pick-up method is presented that includes a method for removing detected defective chips through micro-pulsed laser scanning. The photosensitive functional material, which is an accepted layer for the stable imprinting of chips, is determined by controlling the adhesion. In addition, selective pick-up and adhesion-controlled functional materials allow the implementation of defect-free displays through two pick-and-place cycles. Displays and related systems fabricated with this method can offer interesting optical and electrical properties.
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Affiliation(s)
- Jun-Beom Park
- Korea Photonics Technology Institute, Photonic Device Research Center, 124, Cheomdanventure-ro, Buk-gu, Gwangju, 61007, Republic of Korea.,Chonnam National University, Optoelectronics Convergence Research Center, 77, Yongbong-ro, Buk-gu, Gwangju, 61186, Republic of Korea
| | - Keon Hwa Lee
- Korea Photonics Technology Institute, Photonic Device Research Center, 124, Cheomdanventure-ro, Buk-gu, Gwangju, 61007, Republic of Korea
| | - Sang Hoon Han
- Korea Photonics Technology Institute, Photonic Device Research Center, 124, Cheomdanventure-ro, Buk-gu, Gwangju, 61007, Republic of Korea
| | - Tae Hun Chung
- Korea Photonics Technology Institute, Photonic Device Research Center, 124, Cheomdanventure-ro, Buk-gu, Gwangju, 61007, Republic of Korea
| | - Moon Kyu Kwak
- Kyungpook National University, Mechanical Engineering, 80, Daehak-ro, Buk-gu, Daegu, 41566, Republic of Korea
| | - Hokyun Rho
- Chonnam National University, Optoelectronics Convergence Research Center, 77, Yongbong-ro, Buk-gu, Gwangju, 61186, Republic of Korea
| | - Tak Jeong
- Korea Photonics Technology Institute, Photonic Device Research Center, 124, Cheomdanventure-ro, Buk-gu, Gwangju, 61007, Republic of Korea.
| | - Jun-Seok Ha
- Chonnam National University, Optoelectronics Convergence Research Center, 77, Yongbong-ro, Buk-gu, Gwangju, 61186, Republic of Korea.
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Lee SH, Hwang I, Kang BS, Jeong HE, Kwak MK. Highly flexible and self-adaptive dry adhesive end-effectors for precision robotics. Soft Matter 2019; 15:5827-5834. [PMID: 31232414 DOI: 10.1039/c9sm00431a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Many research groups have studied biomimetic functional surfaces for practical applications. Dry adhesives inspired by the gecko foot consist of hierarchical and numerous micro/nano hairs and can achieve pull-off strengths for vertical and shear adhesion of up to 20 N cm-2. However, when detachment of the nearly dry adhesive is carried out by peeling, the pull-off strength of the dry adhesive in the tilted state is remarkably reduced. In this study, an enhanced pull-off strength dry adhesive in the tilted state was fabricated by using a strategy that reduces the restoring force from the bending moment. An experiment with various column-type dry adhesives was implemented to find the relation between the pull-off strength in the tilted state and the bending resistance of the dry adhesive. The feasibility of using a dry adhesive in the tilted state was observed through a glass-lifting experiment. This strategy could be widely utilized in many practical applications, such as robotics.
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Affiliation(s)
- Sung Ho Lee
- School of Mechanical Engineering, Kyungpook National University, Daegu, 41566, Korea.
| | - Insol Hwang
- Department of Mechanical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea.
| | - Bong Su Kang
- School of Mechanical Engineering, Kyungpook National University, Daegu, 41566, Korea.
| | - Hoon Eui Jeong
- Department of Mechanical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea.
| | - Moon Kyu Kwak
- School of Mechanical Engineering, Kyungpook National University, Daegu, 41566, Korea.
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Kwak MK, Lee EJ, Park JW, Park SY, Kim BJ, Kim TH, Suh K, Koh JM, Lee SH, Byun DW. CD4 T cell count is inversely associated with lumbar spine bone mass in HIV-infected men under the age of 50 years. Osteoporos Int 2019; 30:1501-1510. [PMID: 30915506 DOI: 10.1007/s00198-019-04942-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/28/2018] [Accepted: 03/14/2019] [Indexed: 01/21/2023]
Abstract
UNLABELLED HIV-infected men under the age of 50 years had a lower bone mass compared to that of HIV-uninfected men. Lower CD4 T cell counts, independent of whether antiretroviral therapy (ART) was used, were associated with lower BMD. HIV-infected patients with low CD4 T cell counts may need follow-up and intervention regarding bone health, including younger patients. INTRODUCTION HIV-infected patients have a low bone mineral density (BMD) owing to multifactorial interaction between common osteoporosis risk factors and HIV-related factors, including chronic inflammation and ART. Although HIV infection and ART might affect bone metabolism, little data is available for patients aged under 50 years. We aimed to investigate the association of HIV infection-induced low CD4 T cell counts and ART with BMD in men aged under 50 years. METHODS We performed an age- and body mass index-matched case-control study. BMD values of HIV-infected and HIV-uninfected men (< 50 years) were compared, and HIV-infected men were stratified by CD4 T cell counts and ART use. RESULTS After adjusting confounders, HIV-infected men with CD4 T cell counts ≥ 500 cells/μL (n = 28) and < 500 cells/μL (n = 139) had lower BMD at the femoral neck (FN, p < 0.001) and total hip (TH, p < 0.001) than HIV-uninfected men (n = 167). HIV-infected men with CD4 T cell counts < 500/μL had lower BMD at the lumbar spine (LS, p = 0.034) than those with counts of ≥ 500 cells/μL, but not at FN and TH. The CD4 T cell count (γ = 0.169, p = 0.031) was positively correlated with BMD at LS. There was no significant difference in the BMD (p = 0.499-> 0.999) between the ART-naïve (n = 75) and ART-user group (n = 92). CONCLUSIONS Despite their relatively younger age, HIV-infected men had a lower BMD than HIV-uninfected men. Lower CD4 T cell counts, irrespective of ART, might result in lower bone mass.
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Affiliation(s)
- M K Kwak
- Division of Endocrinology and Metabolism, Asan Medical Center, University of Ulsan College of Medicine, 88 Olympic-ro 43-gil, Songpa-gu, Seoul, 05505, South Korea
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Soonchunhyang University Hospital, Soonchunhyang University College of Medicine, Seoul, 04401, South Korea
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Hallym University Dontan Sacred Heart Hospital, 7, Keunjaebong-gil, Hwaseong-Si, Gyeonggi-Do, 18450, South Korea
| | - E J Lee
- Division of Infectious Diseases, Department of Internal Medicine, Soonchunhyang University Hospital, Soonchunhyang University College of Medicine, 59 Daesagwan-ro, Yongsan-gu, Seoul, 04401, South Korea
| | - J W Park
- Division of Infectious Diseases, Department of Internal Medicine, Soonchunhyang University Cheonan Hospital, Soonchunhyang University College of Medicine, 31 Suncheonhyang 6-gil, Dongnam-gu, Cheonan-si, Chungcheongnam-do, 31151, South Korea
| | - S Y Park
- Division of Infectious Diseases, Department of Internal Medicine, Soonchunhyang University Hospital, Soonchunhyang University College of Medicine, 59 Daesagwan-ro, Yongsan-gu, Seoul, 04401, South Korea
| | - B -J Kim
- Division of Endocrinology and Metabolism, Asan Medical Center, University of Ulsan College of Medicine, 88 Olympic-ro 43-gil, Songpa-gu, Seoul, 05505, South Korea
| | - T H Kim
- Division of Infectious Diseases, Department of Internal Medicine, Soonchunhyang University Hospital, Soonchunhyang University College of Medicine, 59 Daesagwan-ro, Yongsan-gu, Seoul, 04401, South Korea
| | - K Suh
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Soonchunhyang University Hospital, Soonchunhyang University College of Medicine, Seoul, 04401, South Korea
| | - J -M Koh
- Division of Endocrinology and Metabolism, Asan Medical Center, University of Ulsan College of Medicine, 88 Olympic-ro 43-gil, Songpa-gu, Seoul, 05505, South Korea
| | - S H Lee
- Division of Endocrinology and Metabolism, Asan Medical Center, University of Ulsan College of Medicine, 88 Olympic-ro 43-gil, Songpa-gu, Seoul, 05505, South Korea.
| | - D -W Byun
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Soonchunhyang University Hospital, Soonchunhyang University College of Medicine, Seoul, 04401, South Korea.
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20
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Kim BJ, Yoo HJ, Park SJ, Kwak MK, Lee SH, Kim SJ, Hamrick MW, Isales CM, Ahn SH, Koh JM. Association of blood n-3 fatty acid with bone mass and bone marrow TRAP-5b in the elderly with and without hip fracture. Osteoporos Int 2019; 30:1071-1078. [PMID: 30719549 DOI: 10.1007/s00198-019-04881-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2018] [Accepted: 01/27/2019] [Indexed: 10/27/2022]
Abstract
UNLABELLED The plasma n-3 fatty acid level was 26.2% lower in patients with osteoporotic hip fracture than in those with osteoarthritis. In all patients, n-3 fatty acid was positively associated with bone mineral density and inversely associated with tartrate-resistant acid phosphatase-5b level in bone marrow aspirates, reflecting the bone microenvironment. INTRODUCTION Despite the potential beneficial role of n-3 fatty acid (FA) on bone metabolism, the specific mechanisms underlying these effects in humans remain unclear. Here, we assessed whether the plasma n-3 level, as an objective indicator of its status, is associated with osteoporosis-related phenotypes and bone-related markers in human bone marrow (BM) samples. METHODS This was a case-control and cross-sectional study conducted in a clinical unit. n-3 FA in the blood and bone biochemical markers in the BM aspirates were measured by gas chromatography/mass spectrometry and immunoassay, respectively. BM fluids were collected from 72 patients who underwent hip surgery because of either osteoporotic hip fracture (HF; n = 28) or osteoarthritis (n = 44). RESULTS After adjusting for confounders, patients with HF had 26.2% lower plasma n-3 levels than those with osteoarthritis (P = 0.006), and each standard deviation increment in plasma n-3 was associated with a multivariate-adjusted odds ratio of 0.40 for osteoporotic HF (P = 0.010). In multivariate analyses including all patients, a higher plasma n-3 level was associated with higher bone mass at the lumbar spine (β = 0.615, P = 0.002) and total femur (β = 0.244, P = 0.045). Interestingly, the plasma n-3 level was inversely associated with the tartrate-resistant acid phosphatase-5b level (β = - 0.633, P = 0.023), but not with the bone-specific alkaline phosphatase level, in BM aspirates. CONCLUSIONS These findings provide clinical evidence that n-3 FA is a potential inhibitor of osteoclastogenesis that favors human bone health.
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Affiliation(s)
- B-J Kim
- Division of Endocrinology and Metabolism, Asan Medical Center, University of Ulsan College of Medicine, 88 Olympic-ro 43-gil, Songpa-gu, Seoul, 05505, South Korea.
| | - H J Yoo
- Department of Convergence Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea
| | - S J Park
- Asan Institute for Life Sciences, Seoul, South Korea
| | - M K Kwak
- Division of Endocrinology and Metabolism, Asan Medical Center, University of Ulsan College of Medicine, 88 Olympic-ro 43-gil, Songpa-gu, Seoul, 05505, South Korea
| | - S H Lee
- Division of Endocrinology and Metabolism, Asan Medical Center, University of Ulsan College of Medicine, 88 Olympic-ro 43-gil, Songpa-gu, Seoul, 05505, South Korea
| | - S J Kim
- Department of Convergence Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea
| | - M W Hamrick
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, Augusta, GA, USA
| | - C M Isales
- Department of Orthopedic Surgery, Medical College of Georgia, Augusta University, Augusta, GA, USA
| | - S H Ahn
- Department of Endocrinology, Inha University School of Medicine, Incheon, South Korea
| | - J-M Koh
- Division of Endocrinology and Metabolism, Asan Medical Center, University of Ulsan College of Medicine, 88 Olympic-ro 43-gil, Songpa-gu, Seoul, 05505, South Korea
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Chen X, Lee SH, Zhang C, Li Q, Yamada K, Kwak MK, Guo LJ. Plasmonic roller lithography. Nanotechnology 2019; 30:105202. [PMID: 30657742 DOI: 10.1088/1361-6528/aaf9dc] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Photo roller lithography systems can generate patterns continuously over large areas by employing flexible photomasks on rotating quartz cylinders. In comparison, plasmonic lithography systems can reach deep sub-wavelength resolution utilizing evanescent waves carrying high spatial frequency components. In this work, we demonstrate a plasmonic roller system by integrating a quartz mechanical roller with a specially designed photomask based on plasmonic waveguide lithography. Deep sub-wavelength uniform patterns with high aspect ratios were printed continuously over a moving substrate. The plasmonic roller system may find practical applications in the large-scale production of electronic and photonic devices in a cost-effective way.
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Affiliation(s)
- Xi Chen
- Applied Physics, University of Michigan, Ann Arbor, MI 48109, United States of America
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Park JB, Choi WS, Chung TH, Lee SH, Kwak MK, Ha JS, Jeong T. Transfer printing of vertical-type microscale light-emitting diode array onto flexible substrate using biomimetic stamp. Opt Express 2019; 27:6832-6841. [PMID: 30876260 DOI: 10.1364/oe.27.006832] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2018] [Accepted: 01/16/2019] [Indexed: 06/09/2023]
Abstract
We report the transfer printing of GaN-based microscale vertical-type light-emitting diodes (μ-VLEDs) using a functional layer and a biomimetic stamp. An oxide-based functional layer is inserted onto the structure of a μ-VLED and used to separate the chip from the μ-VLED wafer by absorbing the pulse of a UV pulse laser during pick-up of the transfer printing process. Polydimethylsiloxane (PDMS)-based biomimetic stamps have been fabricated to mimic the gecko lizard cilia for improved adhesion and repeatability. The biomimetic stamp has an adhesion force of 25.6 N/cm2, which is 12 times the adhesion of a flat stamp; an adhesion force of 10 N/cm2 or more was maintained after 100,000 repeated adhesion tests. A flexible 10 × 10 prototype array on a polyimide substrate was fabricated, and its bending test results indicated that the strain effect on the forward voltage and the output power was less than 1%. The stable bending test results of the prototype indicate that μ-VLEDs using biomimetic stamps allow the necessary stability for practical transfer printing.
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Lee SH, Seong M, Kwak MK, Ko H, Kang M, Park HW, Kang SM, Jeong HE. Tunable Multimodal Drop Bouncing Dynamics and Anti-Icing Performance of a Magnetically Responsive Hair Array. ACS Nano 2018; 12:10693-10702. [PMID: 30248255 DOI: 10.1021/acsnano.8b05109] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Anti-icing materials that can efficiently limit ice formation have a strong potential to replace existing anti-icing techniques, such as Joule heating, chemical release, or mechanical removal, which are usually inefficient, expensive, and environmentally harmful. In this study, an anti-icing material based on a magnetically responsive hierarchical hair array that can actively modulate drop bouncing dynamics is presented. The magnetically responsive hair array exhibits an immediate and reversible structural bending motion in response to an external magnetic field. The array also exhibits superhydrophobicity, regardless of its tilt angle, due to the tapered geometry of the hairs and the multiscale surface roughness of the array. Due to its dynamic structure and water-repellent characteristics, the array can induce distinct multiple modes of drop bouncing behavior by adjusting its structural bending state in a reversible fashion. Three different types of bouncing behavior, namely, quasi-pancake bouncing, directional bouncing, and macrotexture-induced droplet fragmentation, can be obtained with the vertical, tilted, and fully bent hair arrays, respectively. We demonstrate that the dynamically controllable drop bouncing behavior of the magnetically responsive hierarchical array enables the efficient and robust prevention of ice formation and accumulation.
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Affiliation(s)
- Sang-Hyeon Lee
- Department of Mechanical Engineering , Ulsan National Institute of Science and Technology (UNIST) , Ulsan , Republic of Korea 44919
| | - Minho Seong
- Department of Mechanical Engineering , Ulsan National Institute of Science and Technology (UNIST) , Ulsan , Republic of Korea 44919
| | - Moon Kyu Kwak
- Department of Mechanical Engineering , Kyungpook National University , Daegu , Republic of Korea 41566
| | - Hyunwook Ko
- Department of Mechanical Engineering , Ulsan National Institute of Science and Technology (UNIST) , Ulsan , Republic of Korea 44919
| | - Minsu Kang
- Department of Mechanical Engineering , Ulsan National Institute of Science and Technology (UNIST) , Ulsan , Republic of Korea 44919
| | - Hyung Wook Park
- Department of Mechanical Engineering , Ulsan National Institute of Science and Technology (UNIST) , Ulsan , Republic of Korea 44919
| | - Seong Min Kang
- Department of Mechanical Engineering , Chungnam National University , Daejeon , Republic of Korea 34134
| | - Hoon Eui Jeong
- Department of Mechanical Engineering , Ulsan National Institute of Science and Technology (UNIST) , Ulsan , Republic of Korea 44919
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Kim BJ, Kwak MK, Ahn SH, Kim JS, Lee SH, Koh JM. The association of cortisol and adrenal androgen with trabecular bone score in patients with adrenal incidentaloma with and without autonomous cortisol secretion. Osteoporos Int 2018; 29:2299-2307. [PMID: 29971455 DOI: 10.1007/s00198-018-4608-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Accepted: 06/15/2018] [Indexed: 12/22/2022]
Abstract
UNLABELLED Despite ethnic differences in cortisol sensitivity, only one study in Caucasians has assessed trabecular bone score (TBS) in patients with subclinical hypercortisolism (SH). We showed that both subtle cortisol excess and reduced adrenal androgen may contribute to impaired bone quality in Asian women with SH. INTRODUCTION One study in Caucasians has assessed trabecular bone score (TBS), an index of bone microstructure, in adrenal incidentaloma (AI) patients with subclinical hypercortisolism (SH). There are ethnic differences in cortisol sensitivities between Caucasian and Asian populations. We investigated the associations of cortisol and the adrenal androgen dehydroepiandrosterone-sulfate (DHEA-S) with TBS in AI patients with SH, adrenal Cushing's syndrome (CS), and nonfunctional AI (NFAI). METHODS We measured TBS, cortisol levels after the overnight 1 mg dexamethasone suppression test (1 mg DST), and cortisol/DHEA-S in 61 patients with SH (30 men; 31 women), 19 with adrenal CS (4 men; 15 women), and 355 with NFAI (213 men; 142 women). RESULTS After adjusting for confounders, the serum cortisol level after 1 mg DST was inversely correlated with TBS in men (β = -0.133, P = 0.045) and women (β = - 0.140, P = 0.048). Higher cortisol/DHEA-S ratio was associated with lower TBS in women (β = - 0.252, P < 0.001), but not men. This inverse association of cortisol/DHEA-S ratio in women remained statistically significant after adjusting for the serum cortisol level after 1 mg DST (β = - 0.221, P = 0.008). Compared with women with NFAI, women with SH had 2.2% lower TBS (P = 0.040). Deteriorated bone microstructure (TBS < 1.230) was associated with the serum cortisol level after 1 mg DST (odds ratio [OR], 2.18; 95% confidence interval [CI], 1.04-4.53) and cortisol/DHEA-S ratio (OR, 2.05; 95% CI, 1.03-4.08). CONCLUSIONS Subtle cortisol excess in both genders and reduced DHEA-S, especially in women, may contribute to impaired bone quality in Asian patients with SH.
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Affiliation(s)
- B-J Kim
- Division of Endocrinology and Metabolism, Asan Medical Center, University of Ulsan College of Medicine, Seoul, 05505, South Korea
| | - M K Kwak
- Division of Endocrinology and Metabolism, Asan Medical Center, University of Ulsan College of Medicine, Seoul, 05505, South Korea
| | - S H Ahn
- Department of Endocrinology, Inha University School of Medicine, Incheon, 22332, South Korea
| | - J S Kim
- Department of Nuclear Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, 05505, South Korea
| | - S H Lee
- Division of Endocrinology and Metabolism, Asan Medical Center, University of Ulsan College of Medicine, Seoul, 05505, South Korea.
| | - J-M Koh
- Division of Endocrinology and Metabolism, Asan Medical Center, University of Ulsan College of Medicine, Seoul, 05505, South Korea.
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25
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Hwang I, Kim HN, Seong M, Lee SH, Kang M, Yi H, Bae WG, Kwak MK, Jeong HE. Multifunctional Smart Skin Adhesive Patches for Advanced Health Care. Adv Healthc Mater 2018; 7:e1800275. [PMID: 29757494 DOI: 10.1002/adhm.201800275] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Revised: 04/12/2018] [Indexed: 12/21/2022]
Abstract
A skin adhesive patch is the most fundamental and widely used medical device for diverse health-care purposes. Conventional skin adhesive patches have been mainly utilized for routine medical purposes such as wound management, fixation of medical devices, and simple drug release. In contrast to traditional skin adhesive patches, recently developed patches incorporate multiple key functions of bulky medical devices into a thin, flexible patch based on emerging nanomaterials and flexible electronic technologies. Consequently, the meaning of the term "skin adhesive patch" becomes broader and smarter compared to the traditional term. This review summarizes recent efforts undertaken in the development of multifunctional advanced skin adhesive patches, and briefly describes future directions and challenges toward the next generation of smart skin adhesive patches for ubiquitous personalized health care.
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Affiliation(s)
- Insol Hwang
- Department of Mechanical Engineering; Ulsan National Institute of Science and Technology (UNIST); Ulsan 44919 Republic of Korea
| | - Hong Nam Kim
- Center for BioMicrosystems; Brain Science Institute; Korea Institute of Science and Technology (KIST); Seoul 136-791 Republic of Korea
| | - Minho Seong
- Department of Mechanical Engineering; Ulsan National Institute of Science and Technology (UNIST); Ulsan 44919 Republic of Korea
| | - Sang-Hyeon Lee
- Department of Mechanical Engineering; Ulsan National Institute of Science and Technology (UNIST); Ulsan 44919 Republic of Korea
| | - Minsu Kang
- Department of Mechanical Engineering; Ulsan National Institute of Science and Technology (UNIST); Ulsan 44919 Republic of Korea
| | - Hoon Yi
- Department of Mechanical Engineering; Ulsan National Institute of Science and Technology (UNIST); Ulsan 44919 Republic of Korea
| | - Won Gyu Bae
- School of Electrical Engineering; Soongsil University (SSU); Seoul 06978 Republic of Korea
| | - Moon Kyu Kwak
- Department of Mechanical Engineering; Kyungpook National University; Daegu 41566 Republic of Korea
| | - Hoon Eui Jeong
- Department of Mechanical Engineering; Ulsan National Institute of Science and Technology (UNIST); Ulsan 44919 Republic of Korea
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26
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Lee SH, Kim SW, Kang BS, Chang PS, Kwak MK. Scalable and continuous fabrication of bio-inspired dry adhesives with a thermosetting polymer. Soft Matter 2018; 14:2586-2593. [PMID: 29442124 DOI: 10.1039/c7sm02354e] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Many research groups have developed unique micro/nano-structured dry adhesives by mimicking the foot of the gecko with the use of molding methods. Through these previous works, polydimethylsiloxane (PDMS) has been developed and become the most commonly used material for making artificial dry adhesives. The material properties of PDMS are well suited for making dry adhesives, such as conformal contacts with almost zero preload, low elastic moduli for stickiness, and easy cleaning with low surface energy. From a performance point of view, dry adhesives made with PDMS can be highly advantageous but are limited by its low productivity, as production takes an average of approximately two hours. Given the low productivity of PDMS, some research groups have developed dry adhesives using UV-curable materials, which are capable of continuous roll-to-roll production processes. However, UV-curable materials were too rigid to produce good adhesion. Thus, we established a PDMS continuous-production system to achieve good productivity and adhesion performance. We designed a thermal roll-imprinting lithography (TRL) system for the continuous production of PDMS microstructures by shortening the curing time by controlling the curing temperature (the production speed is up to 150 mm min-1). Dry adhesives composed of PDMS were fabricated continuously via the TRL system.
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Affiliation(s)
- Sung Ho Lee
- School of Mechanical Engineering, Kyungpook National University, Daegu, 41566, Korea
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27
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Abstract
A hydrogel-based wet adhesive with bioinspired microstructures can exhibit strong and reversible adhesion to wet and underwater surfaces.
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Affiliation(s)
- Hoon Yi
- Department of Mechanical Engineering
- Ulsan National Institute of Science and Technology
- Ulsan 689-798
- Republic of Korea
| | - Sung Ho Lee
- Department of Mechanical Engineering
- Kyungpook National University
- Daegu 702-701
- Republic of Korea
| | - Minho Seong
- Department of Mechanical Engineering
- Ulsan National Institute of Science and Technology
- Ulsan 689-798
- Republic of Korea
| | - Moon Kyu Kwak
- Department of Mechanical Engineering
- Kyungpook National University
- Daegu 702-701
- Republic of Korea
| | - Hoon Eui Jeong
- Department of Mechanical Engineering
- Ulsan National Institute of Science and Technology
- Ulsan 689-798
- Republic of Korea
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28
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Kwak R, Park HH, Ko H, Seong M, Kwak MK, Jeong HE. Partially Cured Photopolymer with Gradient Bingham Plastic Behaviors as a Versatile Deformable Material. ACS Macro Lett 2017; 6:561-565. [PMID: 35610879 DOI: 10.1021/acsmacrolett.7b00233] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We present rheological and mechanical behaviors of a partially cured photopolymer. When an ultraviolet (UV)-curable resin is exposed to UV light in atmospheric conditions, a partially cured layer is formed on the top of the resin owing to inhibitory effects of oxygen. Interestingly, such a partially cured resin behaves like a Bingham plastic with a yield stress, being a rigid solid at low shear stress and a viscous liquid at high stress. Unlike typical Bingham plastic materials, however, deformation rate saturation is observed with an increase in applied stress, which is attributed to the gradient in the degree of photopolymerization of the resin (termed "gradient Bingham plastic"). This gradient Bingham plastic can be utilized for the robust fabrication of diverse 3D, multiscale structures.
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Affiliation(s)
- Rhokyun Kwak
- Center
for BioMicrosystems, Korea Institute of Science and Technology, Seoul, 02792, Republic of Korea
| | - Hyun-Ha Park
- Department
of Mechanical Engineering, Ulsan National Institute of Science and Technology, Ulsan, 44919, Republic of Korea
| | - Hangil Ko
- Department
of Mechanical Engineering, Ulsan National Institute of Science and Technology, Ulsan, 44919, Republic of Korea
| | - Minho Seong
- Department
of Mechanical Engineering, Ulsan National Institute of Science and Technology, Ulsan, 44919, Republic of Korea
| | - Moon Kyu Kwak
- Department
of Mechanical Engineering, Kyungpook National University, Daegu, 41566, Republic of Korea
| | - Hoon Eui Jeong
- Department
of Mechanical Engineering, Ulsan National Institute of Science and Technology, Ulsan, 44919, Republic of Korea
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29
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Lee JH, Na M, Kim J, Yoo K, Park J, Kim JD, Oh DK, Lee S, Youn H, Kwak MK, Ok JG. Rapid and conformal coating of polymer resins by airbrushing for continuous and high-speed roll-to-roll nanopatterning: parametric quality controls and extended applications. Nano Converg 2017; 4:11. [PMID: 28529841 PMCID: PMC5411404 DOI: 10.1186/s40580-017-0105-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Accepted: 04/13/2017] [Indexed: 05/16/2023]
Abstract
We present a facile and scalable coating method based on controlled airbrushing, which is suitable for conformal resin coating in continuous roll-to-roll (R2R) nanoimprint lithography (NIL) process. By controlling the concentration of UV-curable polymeric resin with mixing the volatile solvent and its airbrushing time, the coated resin film thickness can be readily tuned. After R2R NIL using a flexible nanoscale line pattern (nanograting) mold is conducted upon the airbrushed resin film, a large-area uniform nanograting pattern is fabricated with controlled residual layer thickness (RLT) based on the initial film thickness. We investigate the faithful airbrushing condition that can reliably create the uniform thin films as well as various nanopatterns with controlled morphologies. Using more diluted resin and shorter airbrushing time can reduce the RLTs favourably for many applications, yet is apt to induce the nanoscale pores and discontinued lines. We also discuss how to further improve the quality and scalability of resin airbrushing and its potential applications particularly requiring high-speed and conformal coating on highly topographic and flexible surfaces.
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Affiliation(s)
- Jae Hyuk Lee
- Department of Mechanical and Automotive Engineering, Seoul National University of Science and Technology, Seoul, 01811 South Korea
| | - Minho Na
- Department of Mechanical and Automotive Engineering, Seoul National University of Science and Technology, Seoul, 01811 South Korea
| | - Jiyeop Kim
- Department of Mechanical and Automotive Engineering, Seoul National University of Science and Technology, Seoul, 01811 South Korea
| | - Kangeun Yoo
- Department of Mechanical and Automotive Engineering, Seoul National University of Science and Technology, Seoul, 01811 South Korea
| | - Jaekyu Park
- Department of Mechanical and Automotive Engineering, Seoul National University of Science and Technology, Seoul, 01811 South Korea
| | - Jeong Dae Kim
- Department of Mechanical and Automotive Engineering, Seoul National University of Science and Technology, Seoul, 01811 South Korea
| | - Dong Kyo Oh
- Department of Mechanical and Automotive Engineering, Seoul National University of Science and Technology, Seoul, 01811 South Korea
| | - Seungjo Lee
- Department of Mechanical and Automotive Engineering, Seoul National University of Science and Technology, Seoul, 01811 South Korea
| | - Hongseok Youn
- Department of Mechanical Engineering, Hanbat National University, 125 Dongseodaero, Yuseong-gu, Daejeon, 34158 South Korea
| | - Moon Kyu Kwak
- School of Mechanical Engineering, Kyungpook National University, Daegu, 41566 South Korea
| | - Jong G Ok
- Department of Mechanical and Automotive Engineering, Seoul National University of Science and Technology, Seoul, 01811 South Korea
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30
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Lee J, Kim JY, Choi JH, Ok JG, Kwak MK. Scalable Fabrication of Flexible Microstencils by Using Sequentially Induced Dewetting Phenomenon. ACS Omega 2017; 2:1097-1103. [PMID: 31457492 PMCID: PMC6640947 DOI: 10.1021/acsomega.7b00070] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Accepted: 03/08/2017] [Indexed: 05/16/2023]
Abstract
We present the physics of sequential dewetting phenomenon and continuous fabrication of a polymeric microstencil using dewetting phenomenon with roll-to-roll imprinting equipment. To realize dewetting-assisted residual-free imprinting, mold material, polymer resin, and substrate were selected via interfacial surface energy analysis. In addition, optimal parameters of the continuous process were also studied by experimentally comparing the resultant shape of the microstencil depending on the process speed, aspect ratio of the mold, and applied pressure. As a result, the polymeric microstencil was produced continuously in very high yields, and its maximum resolution reached 20 μm in diameter. For an easy, continuous demolding during the roll-to-roll process, the material chosen for the substrate film was paraffin-coated film, which has the surface energy low enough for dewetting while having a higher adhesion value than polydimethylsiloxane mold. This versatile, high-throughput microstencil fabrication process can be used in many applications requiring flexibility, scalability, and specific material, and high productivity.
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Affiliation(s)
- Jihoon Lee
- School
of Mechanical Engineering, Kyungpook National
University, 80 Daehak-ro, Buk-gu, Daegu 41566, Repulic of Korea
| | - Jun Yeol Kim
- School
of Mechanical Engineering, Kyungpook National
University, 80 Daehak-ro, Buk-gu, Daegu 41566, Repulic of Korea
| | - Jin Ho Choi
- Department
of Mechanical Engineering, Gumi University, 37 Yaeun-ro, Gumi, Gyeongsangbuk-do 39213, Repulic of Korea
| | - Jong G. Ok
- Department
of Mechanical and Automotive Engineering, Seoul National University of Science and Technology, 232 Gongneung-ro, Nowon-gu, Seoul 01811, Repulic of Korea
| | - Moon Kyu Kwak
- School
of Mechanical Engineering, Kyungpook National
University, 80 Daehak-ro, Buk-gu, Daegu 41566, Repulic of Korea
- Research
Center, Ncoretechnology Co., Ltd., 80 Daehak-ro, Buk-gu, Daegu 41566, Repulic of
Korea
- E-mail: (M.K.K.)
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31
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Wi JS, Lee S, Lee SH, Oh DK, Lee KT, Park I, Kwak MK, Ok JG. Facile three-dimensional nanoarchitecturing of double-bent gold strips on roll-to-roll nanoimprinted transparent nanogratings for flexible and scalable plasmonic sensors. Nanoscale 2017; 9:1398-1402. [PMID: 28070589 DOI: 10.1039/c6nr08387k] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
We develop scalable 3D plasmonic nanoarchitectures comprising a double-bent nanoscale Au strip array integrated within the transparent nanograting framework, which can be continuously fabricated on a large-area flexible substrate via roll-to-roll nanoimprint lithography and angled Au deposition, realizing localized surface plasmon resonance with higher sensitivity in a smaller footprint.
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Affiliation(s)
- Jung-Sub Wi
- Center for Nano-Bio Measurement, Korea Research Institute of Standards and Science, Daejeon 34113, Korea
| | - Seungjo Lee
- Department of Mechanical and Automotive Engineering, Seoul National University of Science and Technology, Seoul 01811, Korea.
| | - Sung Ho Lee
- School of Mechanical Engineering, Kyungpook National University, Daegu 41566, Korea.
| | - Dong Kyo Oh
- Department of Mechanical and Automotive Engineering, Seoul National University of Science and Technology, Seoul 01811, Korea.
| | - Kyu-Tae Lee
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Inkyu Park
- School of Mechanical and Aerospace Engineering, KAIST, Daejeon 34141, Korea
| | - Moon Kyu Kwak
- School of Mechanical Engineering, Kyungpook National University, Daegu 41566, Korea.
| | - Jong G Ok
- Department of Mechanical and Automotive Engineering, Seoul National University of Science and Technology, Seoul 01811, Korea.
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Yi H, Kang M, Kwak MK, Jeong HE. Simple and Reliable Fabrication of Bioinspired Mushroom-Shaped Micropillars with Precisely Controlled Tip Geometries. ACS Appl Mater Interfaces 2016; 8:22671-22678. [PMID: 27548917 DOI: 10.1021/acsami.6b07337] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We present a simple yet scalable method with detailed process protocols for fabricating dry adhesives with mushroom-shaped micropillars of controlled tip geometries. The method involves using photo-lithography with a bilayer stack combining SU-8 and lift-off resist, and subsequent replica molding process. This approach utilizes widely used and commercially available materials and can thus be used to generate mushroom-shaped micropillars with precisely controlled tip diameters and thicknesses in a simple, reproducible, and cost-effective manner. The fabricated mushroom-shaped micropillar arrays exhibited highly different tendencies in adhesion strength and repeatability depending on tip geometries, such as tip diameter and thickness, thereby demonstrating the importance of precise tunability of tip geometry of micropillars. The fabricated dry adhesives with optimized tip geometries not only exhibited strong pull-off strength of up to ∼34.8 N cm(-2) on the Si surface but also showed high durability. By contrast, dry adhesives with nonoptimized tips displayed low pull-off strength of ∼3.6 N cm(-2) and poor durability.
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Affiliation(s)
- Hoon Yi
- Department of Mechanical Engineering, Ulsan National Institute of Science and Technology , Ulsan 689-798, Republic of Korea
| | - Minsu Kang
- Department of Mechanical Engineering, Ulsan National Institute of Science and Technology , Ulsan 689-798, Republic of Korea
| | - Moon Kyu Kwak
- Department of Mechanical Engineering, Kyungpook National University , Daegu 702-701, Republic of Korea
| | - Hoon Eui Jeong
- Department of Mechanical Engineering, Ulsan National Institute of Science and Technology , Ulsan 689-798, Republic of Korea
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Park J, Kim DH, Kim HN, Wang CJ, Kwak MK, Hur E, Suh KY, An SS, Levchenko A. Directed migration of cancer cells guided by the graded texture of the underlying matrix. Nat Mater 2016; 15:792-801. [PMID: 26974411 PMCID: PMC5517090 DOI: 10.1038/nmat4586] [Citation(s) in RCA: 121] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Accepted: 01/27/2016] [Indexed: 05/03/2023]
Abstract
Living cells and the extracellular matrix (ECM) can exhibit complex interactions that define key developmental, physiological and pathological processes. Here, we report a new type of directed migration-which we term 'topotaxis'-guided by the gradient of the nanoscale topographic features in the cells' ECM environment. We show that the direction of topotaxis is reflective of the effective cell stiffness, and that it depends on the balance of the ECM-triggered signalling pathways PI(3)K-Akt and ROCK-MLCK. In melanoma cancer cells, this balance can be altered by different ECM inputs, pharmacological perturbations or genetic alterations, particularly a loss of PTEN in aggressive melanoma cells. We conclude that topotaxis is a product of the material properties of cells and the surrounding ECM, and propose that the invasive capacity of many cancers may depend broadly on topotactic responses, providing a potentially attractive mechanism for controlling invasive and metastatic behaviour.
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Affiliation(s)
- JinSeok Park
- Department of Biomedical Engineering, Yale University, New Haven, CT 06520, USA
- Yale Systems Biology Institute, Yale University, West Haven, CT 06516, USA
- Departments of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Deok-Ho Kim
- Department of Bioengineering, University of Washington, Seattle, WA 98195, USA
| | - Hong-Nam Kim
- Department of Mechanical & Aerospace Engineering, Seoul National University, Seoul, Republic of Korea
| | - Chiaochun Joanne Wang
- Departments of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Moon Kyu Kwak
- Department of Mechanical & Aerospace Engineering, Seoul National University, Seoul, Republic of Korea
| | - Eunmi Hur
- Departments of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Kahp-Yang Suh
- Department of Mechanical & Aerospace Engineering, Seoul National University, Seoul, Republic of Korea
| | - Steven S. An
- Department of Environmental Health Sciences, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA
- Department of Chemical and Biomolecular Engineering, The Johns Hopkins University, Baltimore, MD 21218, USA
- Physical Sciences-Oncology Center, Johns Hopkins University, Baltimore, MD 21218, USA
- To whom correspondence should be addressed: Steven S. An, Ph D. (), Andre Levchenko, Ph.D. ()
| | - Andre Levchenko
- Department of Biomedical Engineering, Yale University, New Haven, CT 06520, USA
- Yale Systems Biology Institute, Yale University, West Haven, CT 06516, USA
- To whom correspondence should be addressed: Steven S. An, Ph D. (), Andre Levchenko, Ph.D. ()
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Kim JH, Kang SM, Lee BJ, Ko H, Bae WG, Suh KY, Kwak MK, Jeong HE. Remote Manipulation of Droplets on a Flexible Magnetically Responsive Film. Sci Rep 2015; 5:17843. [PMID: 26648418 PMCID: PMC4673453 DOI: 10.1038/srep17843] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Accepted: 10/26/2015] [Indexed: 11/30/2022] Open
Abstract
The manipulation of droplets is used in a wide range of applications, from lab-on-a-chip devices to bioinspired functional surfaces. Although a variety of droplet manipulation techniques have been proposed, active, fast and reversible manipulation of pure discrete droplets remains elusive due to the technical limitations of previous techniques. Here, we describe a novel technique that enables active, fast, precise and reversible control over the position and motion of a pure discrete droplet with only a permanent magnet by utilizing a magnetically responsive flexible film possessing actuating hierarchical pillars on the surface. This magnetically responsive surface shows reliable actuating capabilities with immediate field responses and maximum tilting angles of ~90°. Furthermore, the magnetic responsive film exhibits superhydrophobicity regardless of tilting angles of the actuating pillars. Using this magnetically responsive film, we demonstrate active and reversible manipulation of droplets with a remote magnetic force.
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Affiliation(s)
- Jeong Hun Kim
- School of Mechanical and Aerospace Engineering, Seoul National University, Seoul 151-742, Republic of Korea
| | - Seong Min Kang
- School of Mechanical and Aerospace Engineering, Seoul National University, Seoul 151-742, Republic of Korea
| | - Byung Jun Lee
- School of Mechanical and Aerospace Engineering, Seoul National University, Seoul 151-742, Republic of Korea
| | - Hangil Ko
- Department of Mechanical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Republic of Korea
| | - Won-Gyu Bae
- School of Mechanical and Aerospace Engineering, Seoul National University, Seoul 151-742, Republic of Korea
| | - Kahp Yang Suh
- School of Mechanical and Aerospace Engineering, Seoul National University, Seoul 151-742, Republic of Korea
| | - Moon Kyu Kwak
- Department of Mechanical Engineering, Kyungpook National University, Daegu 702-701, Republic of Korea
| | - Hoon Eui Jeong
- Department of Mechanical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Republic of Korea
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Jung HS, Park KM, Kang DH, Kwak MK, Lim S, Chang PS, Kim K. Gas-sensing array application for on-line monitoring in a heat-responsive bioprocess of Streptomyces griseus HUT 6037. Food Sci Biotechnol 2015. [DOI: 10.1007/s10068-015-0113-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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36
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Yi H, Hwang I, Lee JH, Lee D, Lim H, Tahk D, Sung M, Bae WG, Choi SJ, Kwak MK, Jeong HE. Continuous and scalable fabrication of bioinspired dry adhesives via a roll-to-roll process with modulated ultraviolet-curable resin. ACS Appl Mater Interfaces 2014; 6:14590-14599. [PMID: 25115997 DOI: 10.1021/am503901f] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
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.
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Affiliation(s)
- Hoon Yi
- Department of Mechanical Engineering, Ulsan National Institute of Science and Technology , Ulsan 689-798, Republic of Korea
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Ok JG, Kwak MK, Huard CM, Youn HS, Guo LJ. Photo-roll lithography (PRL) for continuous and scalable patterning with application in flexible electronics. Adv Mater 2013; 25:6554-6561. [PMID: 24014277 DOI: 10.1002/adma.201303514] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2013] [Indexed: 06/02/2023]
Abstract
A novel nanofabrication methodology for continuous, scalable, and geometry-tunable lithography is developed, named photo-roll lithography (PRL), by integrating photolithography with rollable processing. As a flexible mask attached to a quartz cylinder containing a UV source rolls over a photoresistcoated substrate, PRL realizes continuous photolithographic fabrication of various micro/nanoscale patterns with geometry that is tunable by controlling mask-substrate motions.
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Affiliation(s)
- Jong G Ok
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan, 48109, USA; Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan, 48109, USA
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Kang SM, Lee C, Kim HN, Lee BJ, Lee JE, Kwak MK, Suh KY. Directional oil sliding surfaces with hierarchical anisotropic groove microstructures. Adv Mater 2013; 25:5756-5761. [PMID: 23913781 DOI: 10.1002/adma.201302083] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2013] [Indexed: 05/28/2023]
Abstract
A robust directional oil sliding surface is presented by utilizing re-entrant micro-groove arrays inspired from the microgrooves of rice leaf. The overhang micro-groove arrays are shown to provide two primary goals of "omniphobicty" and "anisotropic sliding" with DI water (γlv = 72.1 mN/m) as well as mineral oil (γlv = 28 mN/m) and conventional photoresist.
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Affiliation(s)
- Seong Min Kang
- Department of Mechanical and Aerospace Engineering, Seoul National University, Seoul, 151-742, Korea
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Kwak MK, Kim WY, Lee CW, Seo DW, Sohn CH, Ahn S, Lim KS, Donnino MW. The impact of saddle embolism on the major adverse event rate of patients with non-high-risk pulmonary embolism. Br J Radiol 2013; 86:20130273. [PMID: 24058095 DOI: 10.1259/bjr.20130273] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
OBJECTIVE Wider application of CT angiography (CTA) improves the diagnosis of acute pulmonary embolism (PE). It also permits the visualisation of saddle embolism (SE), namely thrombi, which are located at the bifurcation of the main pulmonary artery. The aim of this study was to assess the prevalence of SE and whether SE predicts a complicated clinical course in patients with non-high-risk PE. METHODS In total, 297 consecutive patients with non-high-risk PE confirmed using CTA in the emergency department were studied. The presence of SE and its ability to predict the occurrence of major adverse events (MAEs) within 1 month were determined. RESULTS Of the 297 patients, 27 (9.1%) had an SE. The overall mortality at 1 month was 12.5%; no significant difference was observed between the SE and non-SE groups (18.5% vs 11.9%, p=0.32). However, patients with SE were more likely to receive thrombolytic therapy (29.6% vs 8.1%, p<0.01) and had significantly more MAEs (59.3% vs 25.6%, p<0.01). CONCLUSION At the time of diagnosis, SE, as determined using CTA, is associated with the development of MAE within 1 month. It may be a simple method for risk stratification of patients with non-high-risk PE. ADVANCES IN KNOWLEDGE The prognosis of patients with SE, especially those who are haemodynamically stable, is unclear. This study shows that patients with SE, determined with CTA, is associated with the development of MAE.
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Affiliation(s)
- M K Kwak
- Department of Emergency Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea
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Abstract
INTRODUCTION Carbon monoxide (CO) is one of the leading causes of poisoning; it inhibits oxygen delivery, subsequently causing ischemic changes and ultimately death by multiorgan failure. Furthermore, thromboembolic episodes due to CO poisoning have been reported. However, intracardiac thrombus formation following exposure to CO has been very rarely described. Here, a case of right atrial large thrombus formation after CO poisoning is presented. CASE PRESENTATION A previously healthy 24-year-old woman was referred for CO poisoning. She has attempted suicide, and her initial mental status was drowsy with focal memory loss. Her initial CO fraction was 16%, and initial laboratory data showed creatinine kinase-myocardial bound of 90.6 ng/mL (upper limit 5 ng/mL) and troponin I of 1.899 ng/mL (upper limit 1.5 ng/mL). A transthoracic echocardiography was performed 24 h after the accident, revealing a 30 15 mm nodular echogenic mass in the right atrium. Anticoagulation with low-molecular-weight heparin was started along with hyperbaric oxygen therapy. After 7 days of heparinization, the large thrombus in right atrium had resolved. CONCLUSION This report describes an intracardiac thrombus formation induced by CO poisoning. Because intracardiac thrombus can result in pulmonary embolism and cerebral embolic infarction, its consideration following CO poisoning is important.
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Affiliation(s)
- S M Ryoo
- Department of Emergency Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea
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Bae WG, Kim D, Kwak MK, Ha L, Kang SM, Suh KY. Skin Patches: Enhanced Skin Adhesive Patch with Modulus-Tunable Composite Micropillars (Adv. Healthcare Mater. 1/2013). Adv Healthc Mater 2013. [DOI: 10.1002/adhm.201370001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Abstract
Modulus-tunable composite micropillars are presented by combining replica molding and selective inking for skin adhesive patch in "ubiquitous"-health diagnostic devices. Inspired from hierarchical hairs in the gecko's toe pad, a simple method is presented to form composite polydimethylsiloxane (PDMS) micropillars that are highly adhesive (∼1.8 N cm(-2) ) and mechanically robust (∼30 cycles).
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Affiliation(s)
- Won Gyu Bae
- Interdisciplinary Program of Bioengineering, Seoul National University, Seoul, Korea
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Kwak MK, Ok JG, Lee JY, Guo LJ. Continuous phase-shift lithography with a roll-type mask and application to transparent conductor fabrication. Nanotechnology 2012; 23:344008. [PMID: 22885240 DOI: 10.1088/0957-4484/23/34/344008] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We report the development of a near-field optical nanolithography method using a roll-type phase-shift mask. Sub-wavelength resolution is achieved using near-field exposure of photoresist through a cylindrical phase mask, allowing dynamic and high throughput continuous patterning. As an application, we present the fabrication of a transparent electrode in the form of a metallic wire grid by using the roller-based optical lithography method. To fabricate a mesh-type metal pattern, a specific phase-shift mask was designed and critical experimental parameters were also studied. As a result, a transparent conductor with suitable properties was achieved with a recently built cylindrical phase-shift lithography prototype designed to pattern on 100 mm(2) of substrate area.
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Affiliation(s)
- Moon Kyu Kwak
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109, USA
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Kwak MK, Lim YW. Multi-functional nanopatterned optical films fabricated using capillary force lithography. J Colloid Interface Sci 2012; 367:460-6. [PMID: 22074693 DOI: 10.1016/j.jcis.2011.09.033] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2011] [Revised: 09/16/2011] [Accepted: 09/17/2011] [Indexed: 11/16/2022]
Abstract
We demonstrate anisotropic optical films based on liquid crystalline polymer (LCP) using a capillary force lithography (CFL). The fabricated optical films can be used as both an optical component and a self-aligning capability of liquid crystal molecules introduced on the film. Additionally, HA or PA LC can be induced on same material by controlling the water repellency of LCP surface. Moreover, surface anchoring transitions could be controlled by variation of pattern sizes and surface treatment. In this point of view, one thin optical film can act both retarder and alignment layer and then shows good retardation, LC alignment, and transmittance at the same time.
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Affiliation(s)
- Moon Kyu Kwak
- School of Mechanical and Aerospace Engineering, Seoul National University, Seoul 151-742, Republic of Korea.
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Yoon H, Kwak MK, Kim SM, Sung SH, Lim J, Suh HS, Suh KY, Char K. Polymeric nanopillars reinforced with metallic shells in the lower stem region. Small 2011; 7:3005-3010. [PMID: 21898794 DOI: 10.1002/smll.201101114] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2011] [Indexed: 05/31/2023]
Affiliation(s)
- Hyunsik Yoon
- The National Creative Research Initiative Center for Intelligent Hybrids, School of Chemical and Biological Engineering, The WCU Program of Chemical Convergence for Energy and Environment, Seoul National University, Seoul 151-744, Korea
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Ok JG, Park HJ, Kwak MK, Pina-Hernandez CA, Ahn SH, Guo LJ. Continuous patterning of nanogratings by nanochannel-guided lithography on liquid resists. Adv Mater 2011; 23:4444-4448. [PMID: 21882262 DOI: 10.1002/adma.201102199] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2011] [Revised: 07/15/2011] [Indexed: 05/31/2023]
Affiliation(s)
- Jong G Ok
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109, USA
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47
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Kwak MK, Jeong HE, Suh KY. Rational design and enhanced biocompatibility of a dry adhesive medical skin patch. Adv Mater 2011; 23:3949-53. [PMID: 21796686 DOI: 10.1002/adma.201101694] [Citation(s) in RCA: 149] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2011] [Revised: 06/26/2011] [Indexed: 05/22/2023]
Affiliation(s)
- Moon Kyu Kwak
- School of Mechanical and Aerospace Engineering, Seoul National University, Seoul, Korea
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Kwak MK, Jeong HE, Bae WG, Jung HS, Suh KY. Anisotropic adhesion properties of triangular-tip-shaped micropillars. Small 2011; 7:2296-2300. [PMID: 21630445 DOI: 10.1002/smll.201100455] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Revised: 04/19/2011] [Indexed: 05/30/2023]
Abstract
Directional dry adhesive microstructures consisting of high-density triangular-tip-shaped micropillars are described. The wide-tip structures allow for unique directional shear adhesion properties with respect to the peeling direction, along with relatively high normal adhesion.
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Affiliation(s)
- Moon Kyu Kwak
- School of Mechanical and Aerospace Engineering, Seoul National University, Seoul 151-742, Korea
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You MH, Kwak MK, Kim DH, Kim K, Levchenko A, Kim DY, Suh KY. Synergistically enhanced osteogenic differentiation of human mesenchymal stem cells by culture on nanostructured surfaces with induction media. Biomacromolecules 2010; 11:1856-62. [PMID: 20568737 DOI: 10.1021/bm100374n] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
We have examined the effects of surface nanotopography on in vitro osteogenesis of human mesenchymal stem cells (hMSCs). UV-assisted capillary force lithography was employed to fabricate a scalable (4x5 cm), well-defined nanostructured substrate of a UV curable polyurethane polymer with dots (150, 400, 600 nm diameter) and lines (150, 400, 600 nm width). The influence of osteogenic differentiation of hMSCs was characterized at day 8 by alkaline phosphatase (ALP) assay, RT-PCR, and real-time PCR analysis. We found that hMSCs cultured on the nanostructured surfaces in osteogenic induction media showed significantly higher ALP activity compared to unpatterned PUA surface (control group). In particular, the hMSCs on the 400 nm dot pattern showed the highest level of ALP activity. Further investigation with real-time quantitative RT-PCR analysis demonstrated significantly higher expression of core binding factor 1 (Cbfa1), osteopontin (OP), and osteocalcin (OC) levels in hMSCs cultured on the 400 nm dot pattern in osteogenic induction media. These findings suggest that surface nanotopography can enhance osteogenic differentiation synergistically with biochemical induction substance.
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Affiliation(s)
- Mi-Hyeon You
- Department of Veterinary Pathology, Seoul National University, Seoul 151-742, Korea
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Kwak MK, Shin KH, Yoon EY, Suh KY. Fabrication of conductive metal lines by plate-to-roll pattern transfer utilizing edge dewetting and flexographic printing. J Colloid Interface Sci 2010; 343:301-5. [DOI: 10.1016/j.jcis.2009.11.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2009] [Revised: 09/14/2009] [Accepted: 11/02/2009] [Indexed: 10/20/2022]
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