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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] [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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Yi H, Lee SH, Seong M, Kwak MK, Jeong HE. Bioinspired reversible hydrogel adhesives for wet and underwater surfaces. J Mater Chem B 2018; 6:8064-8070. [DOI: 10.1039/c8tb02598c] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A hydrogel-based wet adhesive with bioinspired microstructures can exhibit strong and reversible adhesion to wet and underwater surfaces.
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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] [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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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 CONVERGENCE 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] [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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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] [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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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] [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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Yi H, Kang M, Kwak MK, Jeong HE. Simple and Reliable Fabrication of Bioinspired Mushroom-Shaped Micropillars with Precisely Controlled Tip Geometries. ACS APPLIED MATERIALS & 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] [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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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. NATURE MATERIALS 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] [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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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] [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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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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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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 APPLIED MATERIALS & 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] [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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Ok JG, Kwak MK, Huard CM, Youn HS, Guo LJ. Photo-roll lithography (PRL) for continuous and scalable patterning with application in flexible electronics. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 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] [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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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 PMCID: PMC3856545 DOI: 10.1259/bjr.20130273] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Revised: 07/22/2013] [Accepted: 09/17/2013] [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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Kang SM, Lee C, Kim HN, Lee BJ, Lee JE, Kwak MK, Suh KY. Directional oil sliding surfaces with hierarchical anisotropic groove microstructures. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 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] [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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Ryoo SM, Sohn CH, Kim HJ, Kwak MK, Oh BJ, Lim KS. Intracardiac thrombus formation induced by carbon monoxide poisoning. Hum Exp Toxicol 2013; 32:1193-6. [PMID: 23357963 DOI: 10.1177/0960327112472991] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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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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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Bae WG, Kim D, Kwak MK, Ha L, Kang SM, Suh KY. Enhanced skin adhesive patch with modulus-tunable composite micropillars. Adv Healthc Mater 2013. [PMID: 23184425 DOI: 10.1002/adhm.201200098] [Citation(s) in RCA: 114] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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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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] [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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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] [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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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 (WEINHEIM AN DER BERGSTRASSE, GERMANY) 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] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2011] [Indexed: 05/31/2023]
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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. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 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] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2011] [Revised: 07/15/2011] [Indexed: 05/31/2023]
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Kwak MK, Jeong HE, Suh KY. Rational design and enhanced biocompatibility of a dry adhesive medical skin patch. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 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] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2011] [Revised: 06/26/2011] [Indexed: 05/22/2023]
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Kwak MK, Jeong HE, Bae WG, Jung HS, Suh KY. Anisotropic adhesion properties of triangular-tip-shaped micropillars. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 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] [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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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] [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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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] [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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