Publications by authors named "Jaehong Lee"

24 Publications

  • Page 1 of 1

Testing on the move: South Korea's rapid response to the COVID-19 pandemic.

Transp Res Interdiscip Perspect 2020 May 21;5:100111. Epub 2020 Apr 21.

KAIST, Republic of Korea.

The emergence of COVID-19 in South Korea, and the public and private sector response to it, serves as a valuable case study for countries facing similar outbreaks. This article focuses on how Korean health officials implemented drive-through and walk-through diagnostic testing, and extensive movement and contact tracing, to identify and inform exposed members of the public. Mobile applications from both government agencies and private developers played an important role in guiding people to testing centers, communicating movement trajectories of confirmed cases on digital maps, and tracking the health and movements of travelers and others at risk of exposure. This case study illustrates the importance of rapid adaptation of transportation infrastructure and location-based information technology to respond to public health crises, and how governments can learn from experimentation and past experience to accelerate these responses.
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http://dx.doi.org/10.1016/j.trip.2020.100111DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7172645PMC
May 2020

Out-of-core GPU 2D-shift-FFT algorithm for ultra-high-resolution hologram generation.

Opt Express 2021 Jun;29(12):19094-19112

We propose a novel out-of-core GPU algorithm for 2D-Shift-FFT (i.e., 2D-FFT with FFT-shift) to generate ultra-high-resolution holograms. Generating an ultra-high-resolution hologram requires a large complex matrix (e.g., 100K) with a size that typically exceeds GPU memory. To handle such a large-scale hologram plane with limited GPU memory, we employ a 1D-FFT based 2D-FFT computation method. We transpose the column data to have a continuous memory layout to improve the column-wise 1D-FFT stage performance in both the data communication and GPU computation. We also combine the FFT-shift and transposition steps to reduce and hide the workload. To maximize the GPU utilization efficiency, we exploit the concurrent execution ability of recent heterogeneous computing systems. We also further optimize our method's performance with our cache-friendly chunk generation algorithm and pinned-memory buffer approach. We tested our method on three computing systems having different GPUs and various sizes of complex matrices. Compared to the conventional implementation based on the state-of-the-art GPU FFT library (i.e., cuFFT), our method achieved up to 3.24 and 3.06 times higher performance for a large-scale complex matrix in single- and double-precision cases, respectively. To assess the benefits offered by the proposed approach in an actual application, we applied our method to the layer-based CGH process. As a result, it reduced the time required to generate an ultra-high-resolution hologram (e.g., 100K) up to 28% compared to the use of the conventional algorithm. These results demonstrate the efficiency and usefulness of our method.
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http://dx.doi.org/10.1364/OE.422266DOI Listing
June 2021

Regulation of cell locomotion by nanosecond-laser-induced hydroxyapatite patterning.

Bioact Mater 2021 Oct 26;6(10):3608-3619. Epub 2021 Mar 26.

Center for Biomaterials, Biomedical Research Institute, Korea Institute of Science and Technology (KIST), Seoul, 02792, Republic of Korea.

Hydroxyapatite, an essential mineral in human bones composed mainly of calcium and phosphorus, is widely used to coat bone graft and implant surfaces for enhanced biocompatibility and bone formation. For a strong implant-bone bond, the bone-forming cells must not only adhere to the implant surface but also move to the surface requiring bone formation. However, strong adhesion tends to inhibit cell migration on the surface of hydroxyapatite. Herein, a cell migration highway pattern that can promote cell migration was prepared using a nanosecond laser on hydroxyapatite coating. The developed surface promoted bone-forming cell movement compared with the unpatterned hydroxyapatite surface, and the cell adhesion and movement speed could be controlled by adjusting the pattern width. Live-cell microscopy, cell tracking, and serum protein analysis revealed the fundamental principle of this phenomenon. These findings are applicable to hydroxyapatite-coated biomaterials and can be implemented easily by laser patterning without complicated processes. The cell migration highway can promote and control cell movement while maintaining the existing advantages of hydroxyapatite coatings. Furthermore, it can be applied to the surface treatment of not only implant materials directly bonded to bone but also various implanted biomaterials implanted that require cell movement control.
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http://dx.doi.org/10.1016/j.bioactmat.2021.03.025DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8022786PMC
October 2021

Soft Electronics Based on Stretchable and Conductive Nanocomposites for Biomedical Applications.

Adv Healthc Mater 2021 02 17;10(3):e2001397. Epub 2020 Nov 17.

Department of Robotics Engineering, Daegu Gyeongbuk Institute of Science and Technology (DGIST), 333 Techno jungan-dareo, Daegu, 42988, South Korea.

Research on the field of implantable electronic devices that can be directly applied in the body with various functionalities is increasingly intensifying due to its great potential for various therapeutic applications. While conventional implantable electronics generally include rigid and hard conductive materials, their surrounding biological objects are soft and dynamic. The mechanical mismatch between implanted devices and biological environments induces damages in the body especially for long-term applications. Stretchable electronics with outstanding mechanical compliance with biological objects effectively improve such limitations of existing rigid implantable electronics. In this article, the recent progress of implantable soft electronics based on various conductive nanocomposites is systematically described. In particular, representative fabrication approaches of conductive and stretchable nanocomposites for implantable soft electronics and various in vivo applications of implantable soft electronics are focused on. To conclude, challenges and perspectives of current implantable soft electronics that should be considered for further advances are discussed.
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http://dx.doi.org/10.1002/adhm.202001397DOI Listing
February 2021

Ultrasensitive and Stretchable Conductive Fibers Using Percolated Pd Nanoparticle Networks for Multisensing Wearable Electronics: Crack-Based Strain and H Sensors.

ACS Appl Mater Interfaces 2020 Oct 24;12(40):45243-45253. Epub 2020 Sep 24.

School of Electrical and Electronic Engineering, Yonsei University, Seoul 03722, Republic of Korea.

The need for wearable electronic devices continues to grow, and the research is under way for stretchable fiber-type sensors that are sensitive to the surrounding atmosphere and will provide proficient measurement capabilities. Currently, one-dimensional fiber sensors have several limitations for their extensive use because of the complex structures of the sensing mechanisms. Thus, it is essential to miniaturize these materials with durability while integrating multiple sensing capabilities. Herein, we present an ultrasensitive and stretchable conductive fiber sensor using PdNP networks embedded in elastomeric polymers for crack-based strain and H sensing. The fiber multimodal sensors show a gauge factor of ∼2040 under 70% strain and reliable mechanical deformation tolerance (10,000 stretching cycles) in the strain-sensor mode. For H sensing, the fiber multimodal sensors exhibit a wide sensing range of high sensitivity: -0.43% response at 5 ppm (0.0005%) H gas and -27.3% response at 10% H gas. For the first time, we demonstrate highly stretchable H sensors that can detect H gas under 110% strain with mechanical durability. As demonstrated, their stable performance allows them to be used in wearable applications that integrate fiber multimodal sensors into industrial safety clothing along with a microinorganic light-emitting diode for visual indication, which exhibits proper activation upon H gas exposure.
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http://dx.doi.org/10.1021/acsami.0c10460DOI Listing
October 2020

Opto-E-Dura: A Soft, Stretchable ECoG Array for Multimodal, Multiscale Neuroscience.

Adv Healthc Mater 2020 09 21;9(17):e2000814. Epub 2020 Jul 21.

Laboratory of Neural Circuit Dynamics, Brain Research Institute, University of Zurich, Zurich, 8057, Switzerland.

Soft, stretchable materials hold great promise for the fabrication of biomedical devices due to their capacity to integrate gracefully with and conform to biological tissues. Conformal devices are of particular interest in the development of brain interfaces where rigid structures can lead to tissue damage and loss of signal quality over the lifetime of the implant. Interfaces to study brain function and dysfunction increasingly require multimodal access in order to facilitate measurement of diverse physiological signals that span the disparate temporal and spatial scales of brain dynamics. Here the Opto-e-Dura, a soft, stretchable, 16-channel electrocorticography array that is optically transparent is presented. Its compatibility with diverse optical and electrical readouts is demonstrated enabling multimodal studies that bridge spatial and temporal scales. The device is chronically stable for weeks, compatible with wide-field and 2-photon calcium imaging and permits the repeated insertion of penetrating multielectrode arrays. As the variety of sensors and effectors realizable on soft, stretchable substrates expands, similar devices that provide large-scale, multimodal access to the brain will continue to improve fundamental understanding of brain function.
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http://dx.doi.org/10.1002/adhm.202000814DOI Listing
September 2020

Recent Advances in 1D Stretchable Electrodes and Devices for Textile and Wearable Electronics: Materials, Fabrications, and Applications.

Adv Mater 2020 Feb 9;32(5):e1902532. Epub 2019 Sep 9.

School of Electrical and Electronic Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-Gu, Seoul, 03722, Republic of Korea.

Research on wearable electronic devices that can be directly integrated into daily textiles or clothes has been explosively grown holding great potential for various practical wearable applications. These wearable electronic devices strongly demand 1D electronic devices that are light-weight, weavable, highly flexible, stretchable, and adaptable to comport to frequent deformations during usage in daily life. To this end, the development of 1D electrodes with high stretchability and electrical performance is fundamentally essential. Herein, the recent process of 1D stretchable electrodes for wearable and textile electronics is described, focusing on representative conductive materials, fabrication techniques for 1D stretchable electrodes with high performance, and designs and applications of various 1D stretchable electronic devices. To conclude, discussions are presented regarding limitations and perspectives of current materials and devices in terms of performance and scientific understanding that should be considered for further advances.
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http://dx.doi.org/10.1002/adma.201902532DOI Listing
February 2020

3D Printed Templating of Extrinsic Freeze-Casting for Macro-Microporous Biomaterials.

ACS Biomater Sci Eng 2019 May 1;5(5):2122-2133. Epub 2019 Apr 1.

Department of Mechanical Engineering, The University of Utah, Salt Lake, Utah 84112, United States.

As with most biological materials, natural bone has hierarchical structure. The microstructural features of compact bone are of various length scales with its porosity consisting of larger osteons (∼100 μm diameter) and vascular channels, as well as smaller lacuna spaces (∼10 μm diameter). In this study, the freeze-casting process, which has been previously used to form biocompatible porous scaffolds (made with hydroxyapatite, HA) has been improved to mimic the intrinsic hierarchical structure of natural bone by implementing an extrinsic 3D printed template. The results of pore characterization showed that this novel combined method of 3D printing and freeze-casting is able to produce porosity at multiple length scales. Nonporous, microporous (created with freeze-casting alone), and macro-micro porous (created with freeze-casting and 3D printed templating) scaffolds were compared as substrates to evaluate cellular activities using osteoblast-like MG63 cell lines. The number of cells oriented parallel to the HA wall structures in the freeze-cast scaffold was found to increase on the microporous and macro-micro porous samples when compare to the nonporous samples, mimicking the natural alignment of the lamella of natural bone. Regarding the cell morphologies, cells on microporous and macro-micro porous samples showed narrowly aligned shapes, whereas those on nonporous samples had polygonal shapes with no discernible orientation. Proliferation and differentiation tests demonstrated that no toxicity or functional abnormalities were found in any of the substrates due to potential chemical and mechanical residues that may have been introduced by the freeze-casting process. Monitoring of the three-dimensional distribution of cells in the scaffolds through microcomputed tomography indicates that the cells were well distributed in the interior pore spaces via the interpenetrating macro-micro pore networks. In summary, we demonstrate this novel approach can create porosity at multiple length scales and is highly favorable in creating a biocompatible, osteoconductive, and structurally hierarchical HA scaffolds for biomedical applications.
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http://dx.doi.org/10.1021/acsbiomaterials.8b01308DOI Listing
May 2019

High On-Current Ge-Channel Heterojunction Tunnel Field-Effect Transistor Using Direct Band-to-Band Tunneling.

Micromachines (Basel) 2019 Jan 24;10(2). Epub 2019 Jan 24.

Department of Electrical and Computer Engineering, Ajou University, Suwon 16499, Korea.

The main challenge for tunnel field-effect transistors (TFETs) is achieving high on-current (on) and low subthreshold swing (SS) with reasonable ambipolar characteristics. In order to address these challenges, Ge-channel heterostructure TFET with Si source and drain region is proposed, and its electrical characteristics are compared to other TFET structures. From two-dimensional (2-D) device simulation results, it is confirmed that the Si/Ge heterostructure source junction improves on and SS characteristics by using the direct band-to-band tunneling current. Furthermore, the proposed structure shows suppressed ambipolar behavior since the Ge/Si heterostructure is used at the drain junction.
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http://dx.doi.org/10.3390/mi10020077DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6412961PMC
January 2019

Highly Conductive Fiber with Waterproof and Self-Cleaning Properties for Textile Electronics.

ACS Appl Mater Interfaces 2018 Oct 28;10(42):36094-36101. Epub 2018 Sep 28.

Nanobio Device Laboratory, School of Electrical and Electronic Engineering , Yonsei University , 50 Yonsei-ro , Seodaemun-Gu, Seoul 03722 , Republic of Korea.

Major concerns in the development of wearable textile electronics are exposure to moisture and contamination. The exposure can cause electrical breakdown of the device and its interconnections, and thus continuous efforts have been made to fabricate textile electronics which are free from moisture and pollution. Herein, we developed a highly conductive and waterproof fiber with excellent electrical conductivity (0.11 Ω/cm) and mechanical stability for advanced interconnector components in wearable textile electronics. The fabrication process of the highly conductive fiber involves coating of a commercial Kevlar fiber with Ag nanoparticle-poly(styrene- block-butadiene- block-styrene) polymer composites. The fabricated fiber then gets treated with self-assembled monolayer (SAM)-forming reagents, which yields waterproof and self-cleaning properties. To find optimal SAM-forming reagents, four different kinds of reagents involving 1-decane thiol (DT), 1 H,1 H,2 H,2 H-perfluorohexanethiol, 1 H,1 H,2 H,2 H-perfluorodecyltrichlorosilane, 1 H,1 H,2 H,2 H-perfluodecanethiol (PFDT) were compared in terms of their thiol group and carbon chain lengths. Among the SAM-forming reagents, the PFDT-treated conductive fiber showed superior waterproof and self-cleaning property, as well as great sustainability in the water with varying pH because of nanoscale roughness and low surface energy. In addition, the functionality of the conductive fiber was tested under mechanical compression via repeated washing and folding processes. The developed conductive fiber with waterproof and self-cleaning property has promising applications in the interconnector operated under water and textile electronics.
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http://dx.doi.org/10.1021/acsami.8b10217DOI Listing
October 2018

Highly Sensitive Multifilament Fiber Strain Sensors with Ultrabroad Sensing Range for Textile Electronics.

ACS Nano 2018 05 6;12(5):4259-4268. Epub 2018 Apr 6.

School of Electrical and Electronic Engineering , Yonsei University , 50 Yonsei-ro, Seodaemun-Gu, Seoul 03722 , Republic of Korea.

Highly stretchable fiber strain sensors are one of the most important components for various applications in wearable electronics, electronic textiles, and biomedical electronics. Herein, we present a facile approach for fabricating highly stretchable and sensitive fiber strain sensors by embedding Ag nanoparticles into a stretchable fiber with a multifilament structure. The multifilament structure and Ag-rich shells of the fiber strain sensor enable the sensor to simultaneously achieve both a high sensitivity and largely wide sensing range despite its simple fabrication process and components. The fiber strain sensor simultaneously exhibits ultrahigh gauge factors (∼9.3 × 10 and ∼659 in the first stretching and subsequent stretching, respectively), a very broad strain-sensing range (450 and 200% for the first and subsequent stretching, respectively), and high durability for more than 10 000 stretching cycles. The fiber strain sensors can also be readily integrated into a glove to control a hand robot and effectively applied to monitor the large volume expansion of a balloon and a pig bladder for an artificial bladder system, thereby demonstrating the potential of the fiber strain sensors as candidates for electronic textiles, wearable electronics, and biomedical engineering.
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http://dx.doi.org/10.1021/acsnano.7b07795DOI Listing
May 2018

Single-Droplet Multiplex Bioassay on a Robust and Stretchable Extreme Wetting Substrate through Vacuum-Based Droplet Manipulation.

ACS Nano 2018 02 16;12(2):932-941. Epub 2018 Jan 16.

Center for Biomaterials, Biomedical Research Institute, Korea Institute of Science and Technology (KIST) , Seoul 02792, Republic of Korea.

Herein, a droplet manipulation system with a superamphiphobic (SPO)-superamphiphilic (SPI) patterned polydimethylsiloxane (PDMS) substrate is developed for a multiplex bioassay from single-droplet samples. The SPO substrate is fabricated by sequential spraying of adhesive and fluorinated silica nanoparticles onto a PDMS substrate. It is subsequently subjected to oxygen plasma with a patterned mask to form SPI patterns. The SPO layer exhibits extreme liquid repellency with a high contact angle (>150°) toward low surface tension and viscous biofluidic droplets (e.g., ethylene glycol, blood, dimethyl sulfoxide, and alginate hydrogel). In contrast, the SPI exhibits liquid adhesion with a near zero contact angle. Using the droplet manipulation system, various liquid droplets can be precisely manipulated and dispensed onto the predefined SPI patterns on the SPO PDMS substrate. This system enables a multiplex colorimetric bioassay, capable of detecting multiple analytes, including glucose, uric acid, and lactate, from a single sample droplet. In addition, the detection of glucose concentrations in a plasma droplet of diabetic and healthy mice are performed to demonstrate the feasibility of the proposed system for efficient clinical diagnostic applications.
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http://dx.doi.org/10.1021/acsnano.7b05826DOI Listing
February 2018

Rough-Surface-Enabled Capacitive Pressure Sensors with 3D Touch Capability.

Small 2017 11 19;13(43). Epub 2017 May 19.

Department of Materials Science and Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-Gu, Seoul, 03722, Republic of Korea.

Fabrication strategies that pursue "simplicity" for the production process and "functionality" for a device, in general, are mutually exclusive. Therefore, strategies that are less expensive, less equipment-intensive, and consequently, more accessible to researchers for the realization of omnipresent electronics are required. Here, this study presents a conceptually different approach that utilizes the inartificial design of the surface roughness of paper to realize a capacitive pressure sensor with high performance compared with sensors produced using costly microfabrication processes. This study utilizes a writing activity with a pencil and paper, which enables the construction of a fundamental capacitor that can be used as a flexible capacitive pressure sensor with high pressure sensitivity and short response time and that it can be inexpensively fabricated over large areas. Furthermore, the paper-based pressure sensors are integrated into a fully functional 3D touch-pad device, which is a step toward the realization of omnipresent electronics.
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http://dx.doi.org/10.1002/smll.201700368DOI Listing
November 2017

Graphene Oxide Hierarchical Patterns for the Derivation of Electrophysiologically Functional Neuron-like Cells from Human Neural Stem Cells.

ACS Appl Mater Interfaces 2016 Jul 5;8(28):17763-74. Epub 2016 Jul 5.

Department of Biotechnology, Yonsei University , Seoul 120-749, Republic of Korea.

Graphene has shown great potential for biomedical engineering applications due to its electrical conductivity, mechanical strength, flexibility, and biocompatibility. Topographical cues of culture substrates or tissue-engineering scaffolds regulate the behaviors and fate of stem cells. In this study, we developed a graphene oxide (GO)-based patterned substrate (GPS) with hierarchical structures capable of generating synergistic topographical stimulation to enhance integrin clustering, focal adhesion, and neuronal differentiation in human neural stem cells (hNSCs). The hierarchical structures of the GPS were composed of microgrooves (groove size: 5, 10, and 20 μm), ridges (height: 100-200 nm), and nanoroughness surfaces (height: ∼10 nm). hNSCs grown on the GPS exhibited highly elongated, aligned neurite extension along the ridge of the GPS and focal adhesion development that was enhanced compared to that of cells grown on GO-free flat substrates and GO substrates without the hierarchical structures. In particular, GPS with a groove width of 5 μm was found to be the most effective in activating focal adhesion signaling, such as the phosphorylation of focal adhesion kinase and paxillin, thereby improving neuronal lineage commitment. More importantly, electrophysiologically functional neuron-like cells exhibiting sodium channel currents and action potentials could be derived from hNSCs differentiated on the GPS even in the absence of any of the chemical agents typically required for neurogenesis. Our study demonstrates that GPS could be an effective culture platform for the generation of functional neuron-like cells from hNSCs, providing potent therapeutics for treating neurodegenerative diseases and neuronal disorders.
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http://dx.doi.org/10.1021/acsami.6b01804DOI Listing
July 2016

The effects of attractive vs. repulsive instructional cuing on balance performance.

J Neuroeng Rehabil 2016 Mar 16;13:29. Epub 2016 Mar 16.

Department of Mechanical Engineering, University of Michigan, G.G. Brown Laboratory, 2350 Hayward St., 48109, Ann Arbor, MI, USA.

Background: Torso-based vibrotactile feedback has been shown to improve postural performance during quiet and perturbed stance in healthy young and older adults and individuals with balance impairments. These systems typically include tactors distributed around the torso that are activated when body motion exceeds a predefined threshold. Users are instructed to "move away from the vibration". However, recent studies have shown that in the absence of instructions, vibrotactile stimulation induces small (~1°) non-volitional responses in the direction of its application location. It was hypothesized that an attractive cuing strategy (i.e., "move toward the vibration") could improve postural performance by leveraging this natural tendency.

Findings: Eight healthy older adults participated in two non-consecutive days of computerized dynamic posturography testing while wearing a vibrotactile feedback system comprised of an inertial measurement unit and four tactors that were activated in pairs when body motion exceeded 1° anteriorly or posteriorly. A crossover design was used. On each day participants performed 24 repetitions of Sensory Organization Test condition 5 (SOT5), three repetitions each of SOT 1-6, three repetitions of the Motor Control Test, and five repetitions of the Adaptation Test. Performance metrics included A/P RMS, Time-in-zone and 95 % CI Ellipse. Performance improved with both cuing strategies but participants performed better when using repulsive cues. However, the rate of improvement was greater for attractive versus repulsive cuing.

Conclusions: The results suggest that when the cutaneous signal is interpreted as an alarm, cognition overrides sensory information. Furthermore, although repulsive cues resulted in better performance, attractive cues may be as good, if not better, than repulsive cues following extended training.
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http://dx.doi.org/10.1186/s12984-016-0131-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4793655PMC
March 2016

Textile-Based Electronic Components for Energy Applications: Principles, Problems, and Perspective.

Nanomaterials (Basel) 2015 Sep 7;5(3):1493-1531. Epub 2015 Sep 7.

Nanobio Device Laboratory, School of Electrical and Electronic Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-Gu, Seoul 120-749, Korea.

Textile-based electronic components have gained interest in the fields of science and technology. Recent developments in nanotechnology have enabled the integration of electronic components into textiles while retaining desirable characteristics such as flexibility, strength, and conductivity. Various materials were investigated in detail to obtain current conductive textile technology, and the integration of electronic components into these textiles shows great promise for common everyday applications. The harvest and storage of energy in textile electronics is a challenge that requires further attention in order to enable complete adoption of this technology in practical implementations. This review focuses on the various conductive textiles, their methods of preparation, and textile-based electronic components. We also focus on fabrication and the function of textile-based energy harvesting and storage devices, discuss their fundamental limitations, and suggest new areas of study.
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http://dx.doi.org/10.3390/nano5031493DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5304632PMC
September 2015

Topical Application of Angelica sinensis Improves Pruritus and Skin Inflammation in Mice with Atopic Dermatitis-Like Symptoms.

J Med Food 2016 Jan 25;19(1):98-105. Epub 2015 Aug 25.

1 Department of Convergence Korean Medical Science, College of Korean Medicine and Institute of Korean Medicine, Kyung Hee University , Seoul, Republic of Korea.

Angelica sinensis (AS) is one of the most popular medicinal foods used as a hematopoietic herb and also traditionally applied topically for skin disorders. However, the effectiveness of AS on atopic dermatitis (AD) has not been reported yet. This study was conducted to evaluate the antipruritic and anti-inflammatory effects of AS on regulating AD-related mediators in DNCB (2,4-dinitrochlorobenzene)-induced mice. AS was topically applied to the dorsal skin of DNCB-challenged mice for 11 days. Alteration of skin thickness was measured for assessment of histological improvement. In addition, the number of mast cells, the level of serum immunoglobulin E (IgE), the counting of scratching behavior, and the expression of substance P were evaluated. Also, the expressions of cytokines, nuclear factor κB (NF-κB), phospho-IκBα, and mitogen-activated protein kinases (MAPKs) were measured for evaluating the improvement of skin inflammation. The repeated treatment of AS significantly inhibited the skin thickness, the number of mast cells, and the level of serum IgE. Moreover, AS significantly suppressed the increased scratching behavior and the expression of substance P compared to the DNCB group. Topical application of AS also reduced the level of cytokines (IL-4, IL-6, TNF-α, and IFN-γ) as well as the expressions of NF-κB, phospho-IκBα, and phospho-MAPKs in the dorsal skin. The results of our study suggest that topical application of AS might have efficacy for modulating pruritus and inflammation in AD. Further studies are required to further characterize the mechanism of actions of AS.
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http://dx.doi.org/10.1089/jmf.2015.3489DOI Listing
January 2016

Path-programmable water droplet manipulations on an adhesion controlled superhydrophobic surface.

Sci Rep 2015 Jul 23;5:12326. Epub 2015 Jul 23.

School of Electrical and Electronic Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-Gu, Seoul 120-749, Republic of Korea.

Here, we developed a novel and facile method to control the local water adhesion force of a thin and stretchable superhydrophobic polydimethylsiloxane (PDMS) substrate with micro-pillar arrays that allows the individual manipulation of droplet motions including moving, merging and mixing. When a vacuum pressure was applied below the PDMS substrate, a local dimple structure was formed and the water adhesion force of structure was significantly changed owing to the dynamically varied pillar density. With the help of the lowered water adhesion force and the slope angle of the formed dimple structure, the motion of individual water droplets could be precisely controlled, which facilitated the creation of a droplet-based microfluidic platform capable of a programmable manipulation of droplets. We showed that the platform could be used in newer and emerging microfluidic operations such as surface-enhanced Raman spectroscopy with extremely high sensing capability (10(-15) M) and in vitro small interfering RNA transfection with enhanced transfection efficiency of ~80%.
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http://dx.doi.org/10.1038/srep12326DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4511949PMC
July 2015

Conductive fiber-based ultrasensitive textile pressure sensor for wearable electronics.

Adv Mater 2015 Apr 18;27(15):2433-9. Epub 2015 Feb 18.

Nanobio Device Laboratory, School of Electrical and Electronic Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-Gu, Seoul, 120-749, Republic of Korea.

A flexible and sensitive textile-based pressure sensor is developed using highly conductive fibers coated with dielectric rubber materials. The pressure sensor exhibits superior sensitivity, very fast response time, and high stability, compared with previous textile-based pressure sensors. By using a weaving method, the pressure sensor can be applied to make smart gloves and clothes that can control machines wirelessly as human-machine interfaces.
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http://dx.doi.org/10.1002/adma.201500009DOI Listing
April 2015

The effects of mouth opening on changes in the thickness of deep cervical flexors in normal adults.

J Phys Ther Sci 2015 Jan 9;27(1):239-41. Epub 2015 Jan 9.

Department of CAM & Naturopathy, DaeJeon Institute of Science and Technology, Republic of Korea.

[Purpose] The purpose of this study was to identify changes in the thickness of the deep cervical flexors (DCFs) according to the degree of mouth opening (MO) in normal adults. [Subjects] The study's subjects were 50 normal adults (30 men, 20 women). [Methods] Ultrasound was used to obtain images of muscles, and the NIH ImageJ software was used to measure the thickness of each muscle. [Results] An increase in MO resulted in a corresponding increase in the thickness of the DCFs, and in isometric exercises (IEs), the thickness of the DCFs further increased during MO. [Conclusion] During MO, the thickness of the DCFs increased. This may be due to correlations between mandibular movements and DCFs. Therefore, the results are likely to be utilized as new clinical research data.
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http://dx.doi.org/10.1589/jpts.27.239DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4305572PMC
January 2015

Capillary force-induced glue-free printing of Ag nanoparticle arrays for highly sensitive SERS substrates.

ACS Appl Mater Interfaces 2014 Jun 9;6(12):9053-60. Epub 2014 Jun 9.

Nanobio Device Laboratory, School of Electrical and Electronic Engineering, Yonsei University , 50 Yonsei-ro, Seodaemun-Gu, Seoul 120-749, Republic of Korea.

The fabrication of well-ordered metal nanoparticle structures onto a desired substrate can be effectively applied to several applications. In this work, well-ordered Ag nanoparticle line arrays were printed on the desired substrate without the use of glue materials. The success of the method relies on the assembly of Ag nanoparticles on the anisotropic buckling templates and a special transfer process where a small amount of water rather than glue materials is employed. The anisotropic buckling templates can be made to have various wavelengths by changing the degree of prestrain in the fabrication step. Ag nanoparticles assembled in the trough of the templates via dip coating were successfully transferred to a flat substrate which has hydrophilic surface due to capillary forces of water. The widths of the fabricated Ag nanoparticle line arrays were modulated according to the wavelengths of the templates. As a potential application, the Ag nanoparticle line arrays were used as SERS substrates for various probing molecules, and an excellent surface-enhanced Raman spectroscopy (SERS) performance was achieved with a detection limit of 10(-12) M for Rhodamine 6G.
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http://dx.doi.org/10.1021/am5000382DOI Listing
June 2014

Effects of Home-based Exercise Training with Wireless Monitoring on the Left Ventricular Function of Acute Coronary Syndrome Patients.

J Phys Ther Sci 2013 May 29;25(5):631-3. Epub 2013 Jun 29.

Department of Physical Therapy, Daegu Health College.

[Purpose] While recent studies have reported that cardiac rehabilitation is an effective treatment, there have been few studies of its effects in rehabilitation for acute coronary syndrome (ACS). Therefore, the purpose of this study was to identify the effects of a home-based exercise training using a wireless electrocardiogram (ECG) monitoring device on ACS patients. [Subjects] Fifty ACS patients were randomly divided into a experimental group of 25 patients and a control group of 25 patients. [Methods] The experimental group received education on the training before discharge from hospital and started home-based exercise training two weeks after discharge from hospital. The control group received conventional treatments. The left ventricular function was measured in both groups before the intervention at and 12 weeks, at the end of the intervention. [Results] Both the experimental group and the control group showed significant improvements in the left ventricular ejection fraction and number of regional wall motion abnormalities. In the comparison of the two groups, the experimental group showed a significantly greater decline in regional wall motion abnormalities than the control group. [Conclusion] Home-based exercise training implemented with a wireless monitoring device was effective at improving the left ventricular function of ACS patients.
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http://dx.doi.org/10.1589/jpts.25.631DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3804989PMC
May 2013

Guided transport of water droplets on superhydrophobic-hydrophilic patterned Si nanowires.

ACS Appl Mater Interfaces 2011 Dec 30;3(12):4722-9. Epub 2011 Nov 30.

Nanobio Device Laboratory, School of Electrical and Electronic Engineering, Yonsei University, 134 Shinchon-Dong, Seodaemun-Gu, Seoul 120-749, Republic of Korea.

We present a facile method to fabricate hydrophilic patterns in superhydrophobic Si nanowire (NW) arrays for guiding water droplets. The superhydrophobic Si NW arrays were obtained by simple dip-coating of dodecyltrichlorosilane (DTS). The water contact angles (CAs) of DTS-coated Si NW arrays drastically increased and saturated at the superhydrophobic regime (water CA ≥ 150°) as the lengths of NWs increased. The demonstrated superhydrophobic surfaces show an extreme water repellent property and small CA hysteresis of less than 7°, which enable the water droplets to easily roll off. The wettability of the DTS-coated Si NW arrays can be converted from superhydrophobic to hydrophilic via UV-enhanced photodecomposition of the DTS, and such wettability conversion was reproducible on the same surfaces by repeating the DTS coating and photodecomposition processes. The resulting water guiding tracks were successfully demonstrated via selective patterning of the hydrophilic region on superhydrophobic Si NW arrays, which could enable water droplets to move along defined trajectories.
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http://dx.doi.org/10.1021/am2011756DOI Listing
December 2011