• Carbon letters
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• v.27
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• pp.98-107
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• 2018

Free-standing electrodes of CuO nanorods in carbon nanotubes (CNTs) are developed by synthesizing porous CuO nanorods throughout CNT webs. The electrochemical performance of the free-standing electrodes is evaluated for their use in flexible lithium ion batteries (LIBs). The electrodes comprising CuO@CNT nanocomposites (NCs) were characterized by charge-discharge testing, cyclic voltammetry, and impedance measurement. These structures are capable of accommodating a high number of lithium ions as well as increasing stability; thus, an increase of capacity in long-term cycling and a good rate capability is achieved. We demonstrate a simple process of fabricating free-standing electrodes of CuO@CNT NCs that can be utilized in flexible LIBs with high performance in terms of capacity and cycling stability.

• Composites Research
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• v.31 no.6
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• pp.355-364
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• 2018

Flexible energy-storage devices (FESDs) have been studied and developed extensively over the last few years because of demands in various fields. Since electrochemical performance and mechanical flexibility must be taken into account together, different framework from composition of conventional energy-storage devices (ESDs) is required. Numerous types of electrodes have been proposed to implement the FESDs. Herein, we review the works related to the FESDs so far and focus on free-standing electrodes and, especially substrate-based ones. The way to utilize carbon woven fabric (CF) or carbon cloth (CC) as flexible substrates is quite simple and intuitive. However, it is meaningful in the point of that the framework exploiting CF or CC can be extended to other applications resulting in multifunctional composites. Therefore, summary, which is on utilization of carbon-based material and conductive substrate containing CF and CC for ESDs, turns out to be helpful for other researchers to have crude concepts to get into energy-storage multi-functional composite. Moreover, polymer electrolytes are briefly explored as well because safety is one of the most important issues in FESDs and the electrolyte part mainly includes difficult obstacles to overcome. Lastly, we suggest some points that need to be further improved and studied for FESDs.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.605-608
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• 2008

The preparation and characteristics of flexible indium tin oxide electrodes grown on polyethylene terephthalate (PET) substrates using a specially designed roll-to-roll sputtering system for use in flexible optoelectronics In spite of low a PET substrate temperature, we can obtain the flexible electrode with a sheet resistance of 47.4 ohm/square and an average optical transmittance of 83.46 % in the green region of 500~550 nm wavelength. Both x-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) analysis results showed that all flexible ITO electrodes grown on the PET substrate were an amorphous structure with a very smooth and featureless surface, regardless of the Ar/$O_2$ flow ratio due to the low substrate temperature, which is maintained by a cooling drum. In addition, the flexible ITO electrode grown on the Ar ion beam treated PET substrates showed more stable mechanical properties than the flexible ITO electrode grown on the wet cleaned PET substrate, due to an increased adhesion between the flexible ITO and the PET substrates.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.578-578
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• 2012

Graphene, a flat one-atom-thick two-dimensional layer of carbon atoms, is considered to be a promising candidate for nanoelectronics due to its exceptional electronic properties. Most of all, future nanoelectronics such as flexible displays and artificial electronic skins require low cost manufacturing process on flexible substrate to be integrated with high resolutions on large area. The solution based printing process can be applicable on plastic substrate at low temperature and also adequate for fabrication of electronics on large-area. The combination of printed electronics and graphene has allowed for the development of a variety of flexible electronic devices. As the first step of the study, we prepared the gate electrodes by printing onto the gate dielectric layer on PET substrate. We showed the performance of graphene field-effect transistor with electrohydrodynamic (EHD) inkjet-printed Ag gate electrodes.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.3
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• pp.406-412
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• 2018

This paper describes the fabrication process of laser induced graphene (LIG) and its transfer method on to a flexible and stretchable PDMS substrate. By irradiating CO2 laser on a polyimide(PI) film surface, a localized high temperature is created, resulting in a three-dimensional porous graphene network structure with good conductivity. This LIG electrode is relatively easy to fabricate and since it is very weak the LIG electrode was transferred to a flexible PDMS substrate to increase the sturdiness as well as possible use in flexible applications. Sheet resistance, thickness, and electrochemical activity of the fabricated in-situ LIG electrodes have been examined and compared with the LIG electrodes after transferring to PDMS elastomer. The properties of the LIG electrodes were also examined depending on the $CO_2$ laser power. As the irradiated laser power increased, the LIG electrode resistance decreases and the LIG electrode thickness increased. At 4.8 W of laser power, the average sheet resistance and thickness of the fabricated LIG electrodes were approximately $31.7{\Omega}/{\Box}$ and $62.67{\mu}m$, respectively. Moreover, the electrochemical activity of the fabricated LIG electrode at 4.8 W of laser power showed a high oxidation current of $28.2{\mu}A$ after transferring to PDMS.

• Ceramist
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• v.21 no.1
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• pp.12-23
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• 2018

As the flexible displays have been considered as a breakthrough to make a new electronics category, transparent electrodes have also confronted with an emerging issue, i.e., they also need to be mechanically flexible. For this to be made possible, a transparent electrode capable of withstanding large amounts of strain must be developed. Indium tin oxide (ITO) has been one of the most widely adopted transparent electrodes for displays and other transparent electronics, mainly supported by its high electrical conductivity and optical transparency. However, its brittle nature has forced the display industry to search for other alternatives. Recently, advances in nano-material researches have opened the door for various transparent conductive materials, which include carbon nanotube, graphene, Ag and Cu nanowire, and printable metal grids. Here we reviewed recently-published research works introducing flexible displays, all of which are employing the novel candidates for a conducting material.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.2
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• pp.223-229
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• 2024

Laser-induced plasmonic sintering of metal nanoparticles (NPs) holds significant promise as a technology for producing flexible conducting electrodes. This method offers immediate, straightforward, and scalable manufacturing approaches, eliminating the need for expensive facilities and intricate processes. Nevertheless, the metal NPs come at a high cost due to the intricate synthesis procedures required to ensure long-term reliability in terms of chemical stability and the prevention of NP aggregation. Herein, we induced the self-generation of metal nanoparticles from Ag organometallic ink, and fabricated highly conductive electrodes on flexible substrates through laser-assisted plasmonic annealing. To demonstrate the practicality of the fabricated flexible electrode, it was configured in a mesh pattern, realizing multi-touchable flexible touch screen panel.

• Journal of Powder Materials
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• v.20 no.2
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• pp.120-124
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• 2013

This study is carried out to develop the new process for the fabrication of ultra-fine electrodes on the flexible substrates using superhydrophobic effect. A facile method was developed to form the ultra-fine trenches on the flexible substrates treated by plasma etching and to print the fine metal electrodes using conductive nano-ink. Various plasma etching conditions were investigated for the hydrophobic surface treatment of flexible polyimide (PI) films. The micro-trench on the hydrophobic PI film fabricated under optimized conditions was obtained by mechanical scratching, which gave the hydrophilic property only to the trench area. Finally, the patterning by selective deposition of ink materials was performed using the conductive silver nano-ink. The interface between the conductive nanoparticles and the flexible substrates were characterized by scanning electron microscope. The increase of the sintering temperature and metal concentration of ink caused the reduction of electrical resistance. The sintering temperature lower than $200^{\circ}C$ resulted in good interfacial bonding between Ag electrode and PI film substrate.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.217.2-217.2
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• 2014

We prepared a flexible and transparent CuO/Cu/CuO multilayer electrodes on a polyethylene terephthalate (PET) substrate using a specially designed roll-to-roll sputtering system at room temperature for GFF-type touch screen panels (TSPs). By the continuous roll-to-roll sputtering of the CuO and Cu layer, we fabricated a flexible CuO(150nm)/Cu(150nm)/CuO(150nm) multilayer electrodes with a sheet resistance of $0.289{\Omega}/square$, resistivity of $5.991{\times}10^{-23}{\Omega}-cm$, at the optimized condition without breaking the vacuum. To investigate the feasibility of the CuO/Cu/CuO multilayer as a transparent electrode for GFF-type TSPs, we fabricated simple GFF-type TSPs using the diamond patterned CuO/Cu/CuO electrode on PET substrate as function of mesh line width. Using diamond patterned CuO/Cu/CuO electrode of mesh line $5{\mu}m$ with sheet resistance of 38 Ohm/square, optical transmittance of 90% at 550 nm and an average transmittance of 89% at wavelength range from 380 to 780 nm, we successfully demonstrated GFF-type touch panel screens (TPSs). The successful operation of GFF-type TPSs with CuO/Cu/CuO multilayer electrodes indicates that the CuO/Cu/CuO multilayer is a promising transparent electrode for large-area capacitive-type TPSs due to its low sheet resistance and high transparency.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.8
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• pp.737-742
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• 2014

This paper reports a customized silver ink and its inkjet printing process on a cellulose electro-active paper (EAPap). To synthesize a silver ink, silver nanoparticle is synthesized from silver nitrate, polyvinylpyrrolidone and ethylene glycol, followed by adding a viscosifier, hydroxyethyl-cellulose solution, and a surfactant, diethylene glycol. The silver ink is used in an inkjet printer (Fujifilm Dimatix DMP-2800 series) to print silver electrodes on cellulose EAPap. After printing, the electrodes are heat treated at $200^{\circ}C$. The sintered electrodes show that the thickness of the electrodes linearly increases as the number of printing layers increases. The electrical resistivity of the printed electrodes is $23.5{\mu}{\Omega}-cm$. This customized ink can be used in inkjet printer to print complex electrode patterns on cellulose EAPap to fabricate flexible smart actuators, flexible electronics and sensors.