Instantaneous and Repeatable Self-Healing of Fully Metallic Electrodes at Ambient Conditions

Park, Young-Geun,Kim, Hyobeom,Park, Sun-Young,Kim, Ju-Young,Park, Jang-Ung American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.44

<P>Recent approaches in self-healable electrodes use polymers with exhibiting significantly low electrical conductivity, compared to conventional metals. Such self-healable electrodes also require external stimuli to initiate self-healing, or present slow restoration for their intrinsic healing. Herein, we introduce an instantaneous and repeatable self-healing of highly conductive, fully metallic electrodes at ambient conditions. These electrodes consist of silver and liquid metal (with no polymer), and exhibit a sufficiently high conductivity of 2 S/μm. The liquid metal (LM) component enables instantaneous and repeatable self-healing of these electrodes (within a few milliseconds) under no external energy as well as high stretchability. Additionally, the inclusion of silver in this LM improves the mechanical strength of this composite, thereby overcoming the limitation of a pristine LM that has low mechanical strength. Moreover, this composite formation can be effective in preventing the penetration of gallium atoms into different metals, while preserving electrical contact properties. Also the self-healable nature of electrodes enables their outstanding sustainability against electrical breakdown at relatively high electric fields. Furthermore, the compatibility of these self-healable electrodes with conventional photolithography and wet etching facilitates high-resolution patterning for device fabrications, as demonstrated in an example with a self-healable organic light-emitting diode display.</P> [FIG OMISSION]</BR>

Flexible Transparent Conductive Films with High Performance and Reliability Using Hybrid Structures of Continuous Metal Nanofiber Networks for Flexible Optoelectronics

Park, Juyoung,Hyun, Byung Gwan,An, Byeong Wan,Im, Hyeon-Gyun,Park, Young-Geun,Jang, Junho,Park, Jang-Ung,Bae, Byeong-Soo American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.24

<P>We report an Ag nanofiber-embedded glass-fabric reinforced hybrimer (AgNF-GFRHybrimer) composite film as a reliable and high-performance flexible transparent conducting film. The continuous AgNF network provides superior optoelectronic properties of the composite film by minimizing transmission loss and junction resistance. In addition, the excellent thermal/chemical stability and mechanical durability of the GFRHybrimer matrix provides enhanced mechanical durability and reliability of the final AgNF-GFRHybrimer composite film. To demonstrate the availability of our AgNF-GFRHybrimer composite as a transparent conducting film, we fabricated a flexible organic light-emitting diode (OLED) device on the AgNF-GFRHybrimer film; the OLED showed stable operation during a flexing.</P>

Wearable, wireless gas sensors using highly stretchable and transparent structures of nanowires and graphene

Park, Jihun,Kim, Joohee,Kim, Kukjoo,Kim, So-Yun,Cheong, Woon Hyung,Park, Kyeongmin,Song, Joo Hyeb,Namgoong, GyeongHo,Kim, Jae Joon,Heo, Jaeyeong,Bien, Franklin,Park, Jang-Ung The Royal Society of Chemistry 2016 Nanoscale Vol.8 No.20

<P>Herein, we report the fabrication of a highly stretchable, transparent gas sensor based on silver nanowire-graphene hybrid nanostructures. Due to its superb mechanical and optical characteristics, the fabricated sensor demonstrates outstanding and stable performances even under extreme mechanical deformation (stable until 20% of strain). The integration of a Bluetooth system or an inductive antenna enables the wireless operation of the sensor. In addition, the mechanical robustness of the materials allows the device to be transferred onto various nonplanar substrates, including a watch, a bicycle light, and the leaves of live plants, thereby achieving next-generation sensing electronics for the 'Internet of Things' area.</P>

Partial Cloning of Catalase Gene from Vitreoscilla sp .

Park, Chung Ung,Park, Kie In,Jang, Mi Young 한국유전학회 1996 Genes & Genomics Vol.18 No.4

Oxidants such as hydrogen peroxide (H₂O₂) and superoxide anion (O₂) is dangerous in cells and tissues under physiological condition. Catalase is a hemoprotein that is ubiquitously present in aerobic and aerotolerent cells containg a cytochrome system and decomposes the peroxide into water and molecular oxygen. Gram-negative bacterium Vitreoscilla, a member of the Beggiatoa family, is an abligate aerobe and produce hemoglobin. The presence of catalase in these cells could present the accumulation of peroxide, thus protecting the cells from self destruction when the oxygen concentration is high. To identify Vitreoscilla catalase gene, Southern hybridization containing Vitreoscilla genomic DNA fragment was performed using a oulionucleotide probe. Also Vitreoscilla genomic library constructed 20∼25 kb fragments of digested Vitreoscilla genomic DNA using broadhost-range cosmid vector pVK102 with Escherichia coli Le392 as a host. Since pVK102 is sensitive kanamycin and is resistant tetracycline, these transformants containing recombinant vectors was selected using antibiotics. These transformants were screened by colony hybridization. We identified catalase gene of Vitreoscilla by Southern and colony hybridization.

Impact of Cardiovascular Risk Factors and Cardiovascular Diseases on Outcomes in Patients Hospitalized with COVID-19 in Daegu Metropolitan City

Park Bo Eun,Lee Jang Hoon,Park Hyuk Kyoon,Kim Hong Nyun,Jang Se Yong,Bae Myung Hwan,Yang Dong Heon,Park Hun Sik,Cho Yongkeun,Lee Bong Yul,Nam Chang Wook,Lee Jin Bae,Kim Ung,Chae Shung Chull,Daegu COVI 대한의학회 2021 Journal of Korean medical science Vol.36 No.2

Background: Data regarding the association between preexisting cardiovascular risk factors (CVRFs) and cardiovascular diseases (CVDs) and the outcomes of patients requiring hospitalization for coronavirus disease 2019 (COVID-19) are limited. Therefore, the aim of this study was to investigate the impact of preexisting CVRFs or CVDs on the outcomes of patients with COVID-19 hospitalized in a Korean healthcare system. Methods: Patients with COVID-19 admitted to 10 hospitals in Daegu Metropolitan City, Korea, were examined. All sequentially hospitalized patients between February 15, 2020, and April 24, 2020, were enrolled in this study. All patients were confirmed to have COVID-19 based on the positive results on the polymerase chain reaction testing of nasopharyngeal samples. Clinical outcomes during hospitalization, such as requiring intensive care and invasive mechanical ventilation (MV) and death, were evaluated. Moreover, data on baseline comorbidities such as a history of diabetes, hypertension, dyslipidemia, current smoking, heart failure, coronary artery disease, cerebrovascular accidents, and other chronic cardiac diseases were obtained. Results: Of all the patients enrolled, 954 (42.0%) had preexisting CVRFs or CVDs. Among the CVRFs, the most common were hypertension (28.8%) and diabetes mellitus (17.0%). The prevalence rates of preexisting CVRFs or CVDs increased with age (P < 0.001). The number of patients requiring intensive care (P < 0.001) and invasive MV (P < 0.001) increased with age. The in-hospital death rate increased with age (P < 0.001). Patients requiring intensive care (5.3% vs. 1.6%; P < 0.001) and invasive MV (4.3% vs. 1.7%; P < 0.001) were significantly greater in patients with preexisting CVRFs or CVDs. In-hospital mortality (12.9% vs. 3.1%; P < 0.001) was significantly higher in patients with preexisting CVRFs or CVDs. Among the CVRFs, diabetes mellitus and hypertension were associated with increased requirement of intensive care and invasive MV and in-hospital death. Among the known CVDs, coronary artery disease and congestive heart failure were associated with invasive MV and in-hospital death. In multivariate analysis, preexisting CVRFs or CVDs (odds ratio [OR], 1.79; 95% confidence interval [CI], 1.07–3.01; P = 0.027) were independent predictors of in-hospital death after adjusting for confounding variables. Among individual preexisting CVRF or CVD components, diabetes mellitus (OR, 2.43; 95% CI, 1.51–3.90; P < 0.001) and congestive heart failure (OR, 2.43; 95% CI, 1.06–5.87; P = 0.049) were independent predictors of in-hospital death. Conclusion: Based on the findings of this study, the patients with confirmed COVID-19 with preexisting CVRFs or CVDs had worse clinical outcomes. Caution is required in dealing with these patients at triage.

Effect of Histone Deacetylase Inhibitors on Differentiation of Human Bone Marrow-derived Stem Cells Into Neuron-like Cells

Jang, Sujeong,Park, Seokho,Cho, Hyong-Ho,Yang, Ung,Kang, Maru,Park, Jong-Seong,Park, Sah-Hoon,Jeong, Han-Seong The Basic Science Institute Chosun University 2019 조선자연과학논문집 Vol.12 No.4

Mesenchymal stem cells (MSCs) are known to differentiate into multiple lineages, making neurogenic differentiation an important target in the clinical field. In the present study, we induced the neurogenic differentiation of cells using histone deacetylase (HDAC) inhibitors and studied their mechanisms for further differentiation in vitro. We treated cells with the HDAC inhibitors, MS-275 and NaB; and found that the cells had neuron-like features such as distinct bipolar or multipolar morphologies with branched processes. The mRNA expressions encoding for NEFL, MAP2, TUJ1, OLIG2, and SYT was significantly increased following HDAC inhibitors treatment compared to without HDAC inhibitors; high protein levels of MAP2 and Tuj1 were detected by immunofluorescence staining. We examined the mechanisms of differentiation and found that the Wnt signaling pathway and downstream mitogen-activate protein kinase were involved in neurogenic differentiation of MSCs. Importantly, Wnt4, Wnt5a/b, and Wnt11 protein levels were highly increased after treatment with NaB; signals were activated through the regulation of Dvl2 and Dvl3. Interestingly, NaB treatment increased the levels of JNK and upregulated JNK phosphorylation. After MS-275 treatment, Wnt protein levels were decreased and GSK-3β was phosphorylated. In this cell, HDAC inhibitors controlled the non-canonical Wnt expression by activating JNK phosphorylation and the canonical Wnt signaling by targeting GSK-3β.

Wearable Electronics Using 1D-2D Hybrid Nanostructures

Jang-Ung Park 한국고분자학회 2016 한국고분자학회 학술대회 연구논문 초록집 Vol.41 No.2

Nanoscale, Electrified Liquid Jets for High-Resolution Printing of Charge

Park, Jang-Ung,Lee, Sangkyu,Unarunotai, Sakulsuk,Sun, Yugang,Dunham, Simon,Song, Taeseup,Ferreira, Placid M.,Alleyene, Andrew G.,Paik, Ungyu,Rogers, John A. American Chemical Society 2010 NANO LETTERS Vol.10 No.2

<P>Nearly all research in micro- and nanofabrication focuses on the formation of solid structures of materials that perform some mechanical, electrical, optical, or related function. Fabricating patterns of charges, by contrast, is a much less well explored area that is of separate and growing interesting because the associated electric fields can be exploited to control the behavior of nanoscale electronic and mechanical devices, guide the assembly of nanomaterials, or modulate the properties of biological systems. This paper describes a versatile technique that uses fine, electrified liquid jets formed by electrohydrodynamics at micro- and nanoscale nozzles to print complex patterns of both positive and negative charges, with resolution that can extend into the submicrometer and nanometer regime. The reported results establish the basic aspects of this process and demonstrate the capabilities through printed patterns with diverse geometries and charge configurations in a variety of liquid inks, including suspensions of nanoparticles and nanowires. The use of printed charge to control the properties of silicon nanomembrane transistors provides an application example.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2010/nalefd.2010.10.issue-2/nl903495f/production/images/medium/nl-2009-03495f_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl903495f'>ACS Electronic Supporting Info</A></P>

Tear Glucose Analysis between Using a Smart Contact Lens

Jang-Ung Park 한국자기학회 2023 한국자기학회 학술연구발표회 논문개요집 Vol.33 No.1

Synthesis of monolithic graphene??graphite integrated electronics

Park, Jang-Ung,Nam, SungWoo,Lee, Mi-Sun,Lieber, Charles M. Nature Publishing Group, a division of Macmillan P 2012 Nature materials Vol.11 No.2

Encoding electronic functionality into nanoscale elements during chemical synthesis has been extensively explored over the past decade as the key to developing integrated nanosystems with functions defined by synthesis. Graphene has been recently explored as a two-dimensional nanoscale material, and has demonstrated simple device functions based on conventional top-down fabrication. However, the synthetic approach to encoding electronic functionality and thus enabling an entire integrated graphene electronics in a chemical synthesis had not previously been demonstrated. Here we report an unconventional approach for the synthesis of monolithically integrated electronic devices based on graphene and graphite. Spatial patterning of heterogeneous metal catalysts permits the selective growth of graphene and graphite, with a controlled number of graphene layers. Graphene transistor arrays with graphitic electrodes and interconnects were formed from the synthesis. These functional, all-carbon structures were transferable onto a variety of substrates. The integrated transistor arrays were used to demonstrate real-time, multiplexed chemical sensing and more significantly, multiple carbon layers of the graphene??graphite device components were vertically assembled to form a three-dimensional flexible structure which served as a top-gate transistor array. These results represent substantial progress towards encoding electronic functionality through chemical synthesis and suggest the future promise of one-step integration of graphene??graphite based electronics.