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Surface dipole enhanced instantaneous charge pair generation in triboelectric nanogenerator
Kim, Kyeong Nam,Jung, Yun Kyung,Chun, Jinsung,Ye, Byeong Uk,Gu, Minsu,Seo, Eunyong,Kim, Seongsu,Kim, Sang-Woo,Kim, Byeong-Su,Baik, Jeong Min Elsevier 2016 Nano energy Vol.26 No.-
<P><B>Abstract</B></P> <P>Developing a successful strategy to maximize the surface charge density is crucial to speed-up the commercialization success of triboelectric nanogenerator. Here, for the first time, the fabrication of positive triboelectric material to donate electrons efficiently to dielectrics is reported, by increasing the stretchability for the uniform contact and by introducing a functional group for the surface potential control. A highly stretchable and conductive film with Ag nanowires and PDMS was fabricated as a base material, in which the portion of nanowires exposed above the embedding surface should be accurately controlled. In specific, positively charged 4-(dimethylamino)pyridine (DMAP) coated Au nanoparticles, prepared by phase transfer method, are coated. The DMAP lowers the effective work function of the nanoparticles by a permanent dipole induced at the DMAP-Au interface and enhances the electron transfer to the dielectrics, confirmed by the Kelvin probe force microscope measurement. The designed nanogenerator gives an output performance up to 80V and 86μA, and 2.5mW in output power, 2.5 times enhancement compared with the conventional TENG. With the integration with AC to DC converting circuit and buck-boost circuit, the nanogenerator produces a constant voltage of 2.6V. The wireless sensing system, which operates the remote controller, were also demonstrated, turning on a siren.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A positive triboelectric material to donate electrons efficiently to dielectrics is developed. </LI> <LI> The keynote is to increase the stretchability and to introduce a functional group. </LI> <LI> It was proven to be effective for the uniform contact and surface potential control. </LI> <LI> The TENG gave an output performance up to 80 V and 86 μA, and 2.5 mW in output power. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Seongsu Kang,Bolam Kim,Se-Jun Yim,Jin-Oh Kim,Dong-Pyo Kim,Yeu-Chun Kim 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.88 No.-
Electroporation technique has recently emerged as a tool for delivery of foreign molecules into cells. However, the electroporation has many critical hurdles to overcome in cell viability, delivery efficiency,and productivity. To overcome the hurdles with a single platform, we devised a polyimide (PI)film-basedon- chip electroporation system that shields the cells from the electrodes with four sheathflows,enabling a 3Dflow focusing. This on-chip electroporation with a double forced-flow (OE-DFF)configuration enhances the cell viability to such an extent that even with a long spiral channel for highmolecular delivery efficiency, which is detrimental to the cell viability due to longer exposure to theelectricfield, the cell viability is still increased substantially. The advantages provided by the OE-DFFsystem is demonstrated with afluorescent probe molecule (FITC-BSA) and pPtCrCFP plasmid deliveredinto Chlamydomonas reinhardtii, one of the challenging cell lines to transform. The continuous nature oftheflow system assures high throughput. This novel approach in microfluidic science is expected togreatly contribute to algal research as an efficient electroporation tool as well as to broad applications.
New 4V-Class and Zero-Strain Cathode Material for Na-Ion Batteries
Kim, Jongsoon,Yoon, Gabin,Lee, Myeong Hwan,Kim, Hyungsub,Lee, Seongsu,Kang, Kisuk American Chemical Society 2017 Chemistry of materials Vol.29 No.18
<P>Here, we introduce Na<SUB>3</SUB>V(PO<SUB>3</SUB>)<SUB>3</SUB>N as a novel 4V-class and zero-strain cathode material for Na-ion batteries. Structural analysis based on a combination of neutron and X-ray diffraction (XRD) reveals that the Na<SUB>3</SUB>V(PO<SUB>3</SUB>)<SUB>3</SUB>N crystal contains three-dimensional channels that are suitable for facile Na diffusion. The Na (de)intercalation is observed to occur at ∼4 V vs Na/Na<SUP>+</SUP> in the Na cell via the V<SUP>3+</SUP>/V<SUP>4+</SUP> redox reaction with ∼67% retention of the initial capacity after over 3000 cycles. The remarkable cycle stability is attributed to the near-zero volume change (∼0.24%) and unique centrosymmetric distortion that occurs during a cycle despite the large ionic size of Na ions for (de)intercalation, as demonstrated by <I>ex situ</I> XRD analysis and first-principles calculations. We also demonstrate that the Na<SUB>3</SUB>V(PO<SUB>3</SUB>)<SUB>3</SUB>N electrode can display outstanding power capability with ∼84% of the theoretical capacity retained at 10C, even though the particle sizes are on the micrometer scale (>5 μm), which is attributed to its intrinsic three-dimensional open-crystal framework. The combination of this high power capability and extraordinary cycle stability makes Na<SUB>3</SUB>V(PO<SUB>3</SUB>)<SUB>3</SUB>N a new potential cathode material for Na-ion batteries.</P> [FIG OMISSION]</BR>
Kim, Hyungsub,Park, Inchul,Seo, Dong-Hwa,Lee, Seongsu,Kim, Sung-Wook,Kwon, Woo Jun,Park, Young-Uk,Kim, Chul Sung,Jeon, Seokwoo,Kang, Kisuk American Chemical Society 2012 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.134 No.25
<P>New iron-based mixed-polyanion compounds Li<SUB><I>x</I></SUB>Na<SUB>4–<I>x</I></SUB>Fe<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>2</SUB>(P<SUB>2</SUB>O<SUB>7</SUB>) (<I>x</I> = 0–3) were synthesized, and their crystal structures were determined. The new compounds contained three-dimensional (3D)sodium/lithium paths supported by P<SUB>2</SUB>O<SUB>7</SUB> pillars in the crystal. First principles calculations identified the complex 3D paths with their activation barriers and revealed them as fast ionic conductors. The reversible electrode operation was found in both Li and Na cells with capacities of one-electron reaction per Fe atom, 140 and 129 mAh g<SUP>–1</SUP>, respectively. The redox potential of each phase was ∼3.4 V (vs Li) for the Li-ion cell and ∼3.2 V (vs Na) for the Na-ion cell. The properties of high power, small volume change, and high thermal stability were also recognized, presenting this new compound as a potential competitor to other iron-based electrodes such as Li<SUB>2</SUB>FeP<SUB>2</SUB>O<SUB>7</SUB>, Li<SUB>2</SUB>FePO<SUB>4</SUB>F, and LiFePO<SUB>4</SUB>.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2012/jacsat.2012.134.issue-25/ja3038646/production/images/medium/ja-2012-038646_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja3038646'>ACS Electronic Supporting Info</A></P>
An Efficient Rake Receiver Design for WCDMA System
Seongsu Yang,Jinyong Lee,Soojin Kim,Younglok Kim 대한전자공학회 2008 ITC-CSCC :International Technical Conference on Ci Vol.2008 No.7
In wideband code division multiple access system, Rake receiver is gernerally applied as its equalization algorithm. The equalizaer is the most critical part in terms of the computational complexity of the receiver. Hence more efficient receiver implementin is needed to save power consumption and reduce the computational complexity. In this paper, channel capacity and optimal energy allocation algorithm is applied to reduce the complexity of Rake receiver. We choose effective Rake fingers among multi-path components. Then we reallocate weight factors and combine effective Rake fingers. Applying proposed algorithm, we obtain advantage up to 2㏈ of performance at 0.1% of bit error rate. With about 0.57% additional computational complexity, we can find the optimal number of Rake fingers and reduce computations of unused Rake fingers.
Highly Stable Iron- and Manganese-Based Cathodes for Long-Lasting Sodium Rechargeable Batteries
Kim, Hyungsub,Yoon, Gabin,Park, Inchul,Hong, Jihyun,Park, Kyu-Young,Kim, Jongsoon,Lee, Kug-Seung,Sung, Nark-Eon,Lee, Seongsu,Kang, Kisuk American Chemical Society 2016 Chemistry of materials Vol.28 No.20
<P>The development of long-lasting and low-cost rechargeable batteries lies at the heart of the success of large-scale energy storage systems for various applications. Here, we introduce Fe- and Mn-based Na rechargeable battery cathodes that can stably cycle more than 3000 times. The new cathode is based on the solid-solution phases of Na4MnxFe3-x(PO4)(2)-(P2O7) (x = 1 or 2) that we successfully synthesized for the first time. Electrochemical analysis and ex situ structural investigation reveal that the electrodes operate via a one phase reaction upon charging and discharging with a remarkably low volume change of 2.1% for Na4MnFe2(PO4)(P2O7), which is one of the lowest values among Na battery cathodes reported thus far. With merits including an open framework structure and a small volume change, a stable cycle performance up to 3000 cycles can be achieved at 1C and room temperature, and almost 70% of the capacity at C/20 can be obtained at 20C. We believe that these materials are strong competitors for large-scale Na-ion battery cathodes based on their low costs, long-term cycle stability, and high energy density.</P>