Digital selective growth of a ZnO nanowire array by large scale laser decomposition of zinc acetate.

Hong, Sukjoon,Yeo, Junyeob,Manorotkul, Wanit,Kang, Hyun Wook,Lee, Jinhwan,Han, Seungyong,Rho, Yoonsoo,Suh, Young Duk,Sung, Hyung Jin,Ko, Seung Hwan RSC Pub 2013 Nanoscale Vol.5 No.9

<P>We develop a digital direct writing method for ZnO NW micro-patterned growth on a large scale by selective laser decomposition of zinc acetate. For ZnO NW growth, by replacing the bulk heating with the scanning focused laser as a fully digital local heat source, zinc acetate crystallites can be selectively activated as a ZnO seed pattern to grow ZnO nanowires locally on a larger area. Together with the selective laser sintering process of metal nanoparticles, more than 10,000 UV sensors have been demonstrated on a 4 cm 4 cm glass substrate to develop all-solution processible, all-laser mask-less digital fabrication of electronic devices including active layer and metal electrodes without any conventional vacuum deposition, photolithographic process, premade mask, high temperature and vacuum environment.</P>

Digital selective laser methods for nanomaterials: From synthesis to processing

Hong, Sukjoon,Lee, Habeom,Yeo, Junyeob,Ko, Seung Hwan Elsevier 2016 Nano Today Vol.11 No.5

<P><B>Abstract</B></P> <P>Laser has long been used for material processing, and its applications to nanomaterials for their direct synthesis, positioning and processing are currently active fields of study. The main mechanism of typical laser processes is photothermal reaction by a focused laser that remotely generates confined temperature field at a desired position with high controllability. The laser-induced elevated temperature enables direct synthesis of nanomaterials in both gas and liquid environment as well as photophysical processing of nanomaterials through melting or vaporization, represented by laser sintering and ablation processes, in spatially selective manners. On the other hand, recent advances in laser process further incorporates not only different optical responses such as optical forces and photochemical reactions for more advanced manipulation of nanomaterials, but also the interaction between electromagnetic waves, nanostructures and underlying substrates to facilitate novel processing those cannot be achieved by any other means including laser nanowelding for percolation network and laser thinning for two dimensional nanomaterials. At the same time, the shortcomings of laser process in nanomaterial processing such as limited resolution and low throughput are tackled through introducing different optical schemes together with the integration with other systems. In this review, we summarize the development and current status of digital selective laser methods for nanomaterials in broad aspects that cover from nanomaterial synthesis to its processing.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Digital selective laser processes for nanomaterials are summarized in this review. </LI> <LI> Nanomaterials are selectively synthesized, positioned, controlled and manipulated. </LI> <LI> These processes rely on photothermal, photochemical or photothermochemical reaction. </LI> <LI> More emphasis is placed on the processes for nanoparticles, nanowires and nanosheets. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Nonvacuum, Maskless Fabrication of a Flexible Metal Grid Transparent Conductor by Low-Temperature Selective Laser Sintering of Nanoparticle Ink

Hong, Sukjoon,Yeo, Junyeob,Kim, Gunho,Kim, Dongkyu,Lee, Habeom,Kwon, Jinhyeong,Lee, Hyungman,Lee, Phillip,Ko, Seung Hwan American Chemical Society 2013 ACS NANO Vol.7 No.6

<P>We introduce a facile approach to fabricate a metallic grid transparent conductor on a flexible substrate using selective laser sintering of metal nanoparticle ink. The metallic grid transparent conductors with high transmittance (>85%) and low sheet resistance (30 Ω/sq) are readily produced on glass and polymer substrates at large scale without any vacuum or high-temperature environment. Being a maskless direct writing method, the shape and the parameters of the grid can be easily changed by CAD data. The resultant metallic grid also showed a superior stability in terms of adhesion and bending. This transparent conductor is further applied to the touch screen panel, and it is confirmed that the final device operates firmly under continuous mechanical stress.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2013/ancac3.2013.7.issue-6/nn400432z/production/images/medium/nn-2013-00432z_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn400432z'>ACS Electronic Supporting Info</A></P>

Selective Laser Direct Patterning of Silver Nanowire Percolation Network Transparent Conductor for Capacitive Touch Panel.

Hong, Sukjoon,Yeo, Junyeob,Lee, Jinhwan,Lee, Habeom,Lee, Phillip,Lee, Seung S,Ko, Seung Hwan American Scientific Publishers 2015 Journal of nanoscience and nanotechnology Vol.15 No.3

<P>We introduce a facile method to enhance the functionality of a patterned metallic transparent conductor through selective laser ablation of metal nanowire percolation network. By scanning focused nanosecond pulsed laser on silver nanowire percolation network, silver nanowires are selectively ablated and patterned without using any conventional chemical etching or photolithography steps. Various arbitrary patterns of silver nanowire transparent conductors are readily created on the percolation network by changing various laser parameters such as repetition rate and power. The macroscopic optical and electrical properties of the percolation network transparent conductor can be easily tuned by changing the conductor pattern design via digital selective laser ablation. Further investigation on the silver nanowire based electrode line prepared by the ablation process substantiates that the general relation for a conducting thin film fails at a narrow width, which should be considered for the applications that requires a high resolution patterns. Finally, as a proof of concept, a capacitive touch sensor with diamond patterns has been demonstrated by selective laser ablation of metal nanowire percolation network.</P>

Study on the oxidation of copper nanowire network electrodes for skin mountable flexible, stretchable and wearable electronics applications

Hong, Insic,Lee, Seunggon,Kim, Dongkwan,Cho, Hyunmin,Roh, Yeonwook,An, Hyeongi,Hong, Sukjoon,Ko, Seung Hwan,Han, Seungyong IOP 2019 Nanotechnology Vol.30 No.7

<P>Copper nanowires (Cu NWs) are suitable material as an electrode for flexible, stretchable and wearable devices due to their excellent mechanical properties, high transparency, good conductivity, and low cost, but oxidation problem limits their practical use and application. In order to use Cu NWs as an electrode for advanced flexible, stretchable and wearable devices attached directly to the skin, the influence of the body temperature on the oxidation of Cu NWs needs to be investigated. In this paper, the oxidation behavior of Cu NWs at high temperature (more than 80 °C) as well as body temperature is studied which has been remained largely questionable to date, and an effective encapsulation method is proposed to prevent the oxidation of Cu NWs electrode in the range of body temperatures.</P>

Low-Temperature Rapid Fabrication of ZnO Nanowire UV Sensor Array by Laser-Induced Local Hydrothermal Growth

Hong, Sukjoon,Yeo, Junyeob,Manorotkul, Wanit,Kim, Gunho,Kwon, Jinhyeong,An, Kunsik,Ko, Seung Hwan Hindawi Limited 2013 Journal of nanomaterials Vol.2013 No.-

<P>We demonstrate ZnO nanowire based UV sensor by laser-induced hydrothermal growth of ZnO nanowire. By inducing a localized temperature rise using focused laser, ZnO nanowire array at<I>~</I>15 <I>μ</I>m size consists of individual nanowires with<I>~</I>8 <I>μ</I>m length and 200<I>~</I>400 nm diameter is readily synthesized on gold electrode within 30 min at the desired position. The laser-induced growth process is consecutively applied on two different points to bridge the micron gap between the electrodes. The resultant photoconductive ZnO NW interconnections display 2<I>~</I>3 orders increase in the current upon the UV exposure at a fixed voltage bias. It is also confirmed that the amount of photocurrent can be easily adjusted by changing the number of ZnO NW array junctions. The device exhibits clear response to the repeated UV illumination, suggesting that this process can be usefully applied for the facile fabrication of low-cost UV sensor array.</P>

선택적 레이저 공정을 통한 나노물질 기반 투명전극 생성

홍석준(Sukjoon Hong) 한국정밀공학회 2018 한국정밀공학회 학술발표대회 논문집 Vol.2018 No.5월

Patient sample-oriented analysis of gene expression highlights extracellular signatures in breast cancer progression

Hong, Yourae,Kim, Nayoung,Li, Chao,Jeong, Euna,Yoon, Sukjoon Elsevier 2017 Biochemical and biophysical research communication Vol. No.

<P><B>Abstract</B></P> <P>Although a large collection of cancer cell lines are useful surrogates for patient samples, the physiological relevance of observed molecular phenotypes in cell lines remains controversial. Because transcriptome data are a representative set of molecular phenotypes in cancers, we systematically analyzed the discrepancy of global gene expression profiles between patient samples and cell lines in breast cancers. While the majority of genes exhibited general consistency between patient samples and cell lines, the expression of genes in the categories of extracellular matrix, collagen trimers, receptor activity, catalytic activity and transporter activity were significantly up-regulated only in tissue samples. Genes in the extracellular matrix, particularly collagen trimers, showed a wide variation of expression in tissue, but minimal expression and variation in cell lines. Further analysis of tissue samples exclusively revealed that collagen genes exhibited a cancer stage-dependent expressional variation based on their supramolecular structure. Prognostic collagen biomarkers associated with survival rate were also readily predicted from tissue-oriented transcriptome analysis. This study presents the limitations of cell lines and the exclusive features of tissue samples in terms of functional categories of the cancer transcriptome.</P>

Selective Sintering of Metal Nanoparticle Ink for Maskless Fabrication of an Electrode Micropattern Using a Spatially Modulated Laser Beam by a Digital Micromirror Device

An, Kunsik,Hong, Sukjoon,Han, Seungyong,Lee, Hyungman,Yeo, Junyeob,Ko, Seung Hwan American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.4

<P>We demonstrate selective laser sintering of silver (Ag) nanoparticle (NP) ink using a digital micromirror device (DMD) for the facile fabrication of 2D electrode pattern without any conventional lithographic means or scanning procedure. An arbitrary 2D pattern at the lateral size of 25 μm × 25 μm with 160 nm height is readily produced on a glass substrate by a short exposure of 532 nm Nd:YAG continuous wave laser. The resultant metal pattern exhibits low electrical resistivity of 10.8 uΩ · cm and also shows a fine edge sharpness by the virtue of low thermal conductivity of Ag NP ink. Furthermore, 10 × 10 star-shaped micropattern arrays are fabricated through a step-and-repeat scheme to ensure the potential of this process for the large-area metal pattern fabrication.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-4/am405323c/production/images/medium/am-2013-05323c_0007.gif'></P>

Somatic Mutaome Profile in Human Cancer Tissues

Kim, Nayoung,Hong, Yourae,Kwon, Doyoung,Yoon, Sukjoon Korea Genome Organization 2013 Genomics & informatics Vol.11 No.4

Somatic mutation is a major cause of cancer progression and varied responses of tumors against anticancer agents. Thus, we must obtain and characterize genome-wide mutational profiles in individual cancer subtypes. The Cancer Genome Atlas database includes large amounts of sequencing and omics data generated from diverse human cancer tissues. In the present study, we integrated and analyzed the exome sequencing data from ~3,000 tissue samples and summarized the major mutant genes in each of the diverse cancer subtypes and stages. Mutations were observed in most human genes (~23,000 genes) with low frequency from an analysis of 11 major cancer subtypes. The majority of tissue samples harbored 20-80 different mutant genes, on average. Lung cancer samples showed a greater number of mutations in diverse genes than other cancer subtypes. Only a few genes were mutated with over 5% frequency in tissue samples. Interestingly, mutation frequency was generally similar between non-metastatic and metastastic samples in most cancer subtypes. Among the 12 major mutations, the TP53, USH2A, TTN, and MUC16 genes were found to be frequent in most cancer types, while BRAF, FRG1B, PBRM1, and VHL showed lineage-specific mutation patterns. The present study provides a useful resource to understand the broad spectrum of mutation frequencies in various cancer types.