• Progress in Superconductivity and Cryogenics
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• v.24 no.4
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• pp.6-10
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• 2022

We report on the fabrication and measurements of metallic Josephson junctions (JJs) consisting of Au nanoribbon and NbTi superconducting electrodes. The maximum supercurrent density in the junction reaches up to ~ 3×10⁵ A/cm² at 2.5 K, much larger than that of JJ using single-crystalline Au nanowire. Temperature dependence of the critical current exhibits an exponential decay behavior with increasing temperature, which is consistent with a long and diffusive junction limit. Under the application of a magnetic field, monotonous decrease of the critical current was observed due to a narrow width of the Au nanoribbon. Our observatons suggest that NbTi/Au/NbTi JJ would be a useful platform to develop an integrated superconducing quantum circuit combined with the superconducting coplanar waveguide and ferromagnetic π junctions.

• Journal of Sensor Science and Technology
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• v.32 no.6
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• pp.386-390
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• 2023

Stiffness-engineered stretchable substrate technology has been widely used to produce stretchable displays, transistors, and integrated circuits because it is compatible with various flexible electronics technologies. However, the stiffness-engineering technology has never been applied to transistor-based stretchable strain sensors. In this study, we developed thin-film transistor-based strain sensors on stiffness-engineered stretchable substrates. We designed and fabricated strain-sensitive stretchable resistors capable of inducing changes in drain currents of transistors when subjected to stretching forces. The resistors and source electrodes of the transistors were connected in series to integrate the developed stretchable resistors with thin-film transistors on stretchable substrates by printing the resistors after fabricating transistors. The thin-film transistor-based stretchable strain sensors demonstrate feasibility as strain sensors operating under strains of 0%-5%. This strain range can be extended with further investigations. The proposed stiffness-engineering approach will expand the potential for the advancement and manufacturing of innovative stretchable strain sensors.

• Tribology and Lubricants
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• v.40 no.4
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• pp.118-132
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• 2024

The triboelectric nanogenerator (TENG) has emerged as a groundbreaking technology for harvesting clean and sustainable energy cost effectively. For reliable TENG design, minimizing wear damage at the friction layers is crucial. This review provides a comprehensive overview of tribometer-integrated TENG testing configurations used in the simultaneous investigation of both tribological and electrical performance. It considers configurations such as plate-on-plate, ball-on-disc, and ball-on-flat tribometers designed for linear reciprocating or rotating sliding friction tests. These tribometers are either specifically designed or adapted for TENG testing. Triboelectric material holders facilitate friction tests by establishing electrical connections from the triboelectric materials or electrodes, thereby enabling accurate measurement of electrical signals. Electrometers and oscilloscopes record electrical outputs such as short-circuit current and open-circuit voltage. This integration enables the simultaneous measurement of both friction and electrical outputs, providing a thorough understanding of TENG performance. The review also summarizes how factors such as normal force, sliding frequency, and rotating speed affect friction coefficients and TENG performance. It also examines the relationship between the coefficient of friction and tribocharges under various loads and frequencies. The review emphasizes the importance of these testing configurations for evaluating both friction and electrical performance, which are crucial for optimizing TENG efficiency. Finally, the review explores future prospects for developing innovative tribometer designs suited for both tribology and TENG testing.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.4
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• pp.323-330
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• 2009

The objective of this research was to develop a practical integrated approach using extracted features from electrical resistance measurements and coupled electromechanical models of damage, for in-situ damage detection and sensing in carbon fiber reinforced plastic(CFRP) composites. To achieve this objective, we introduced specific known damage (in terms of type, size, and location) into CFRP laminates and established quantitative relationships with the electrical resistance measurements. For processing of numerous measurement data, an autonomous data acquisition system was devised. We also established a specimen preparation procedure and a method for electrode setup. Coupon and panel CFRP laminate specimens with several known damage were tested. Coupon specimens with various sizes of artificial delaminations obtained by inserting Teflon film were manufactured and the resistance was measured. The measurement results showed that increase of delamination size led to increase of resistance implying that it is possible to sense the existence and size of delamination. A quasi-isotropic panel was manufactured and electrical resistance was measured. Then three different sizes of holes were drilled at a chosen location. The panel was prepared using the established procedures with six electrode connections on each side making a total of twenty-four electrodes. Vertical, horizontal, and diagonal pairs of electrodes were chosen and the resistance was measured. The measurement results showed the possibility of the established measurement system for an in-situ damage detection method for CFRP composite structures.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.6
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• pp.37-45
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• 2018

An electric vehicle is an environmentally friendly vehicle because there is no exhaust gas, unlike gasoline automobiles. On the other hand, because the electric vehicle is driven by electric power charged in batteries, the distance to go through a single charge depends on the energy density of the batteries. Therefore, a lithium-ion battery with a high energy density is a good candidate for batteries in electric vehicles. Because the electrode is an essential component that governs the efficiency of a lithium-ion battery, the electrode manufacturing process plays a vital role in the entire production process of lithium-ion batteries. In particular, the drying process during the electrode manufacturing process is a critical process that has a significant influence on the performance. This paper proposes an innovative process for improving the efficiency and productivity of the drying process in electrode manufacturing and describe the equipment design method and development results. In particular, the design procedure and development method for enhancing the electrode adhesion power, atmospheric pressure superheated steam drying technology, and drying furnace slimming technologies are presented. As a result, high-speed drying technology was developed for battery electrodes through the world's first turbo dryer technology for mass production using open/integrated atmospheric pressure superheated steam. Compared to the conventional drying process, the drying furnace improved the productivity (Dry Lead Time $0.7min{\rightarrow}0.5min$).

• Korean Journal of Materials Research
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• v.30 no.6
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• pp.285-291
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• 2020

Recent advances in technology using ultra-thin noble metal film in oxide/metal/oxide structures have attracted attention because this material is a promising alternative to meet the needs of transparent conduction electrodes (TCE). AZO/Ag/AZO multilayer films are prepared by magnetron sputtering for Cu₂ZnSn(S,Se)₄ (CZTSSe) of kesterite solar cells. It is shown that the electrical and optical properties of the AZO/Ag/AZO multilayer films can be improved by the very low resistivity and surface plasmon effects due to the deposition of different thicknesses of Ag layer between oxide layers fixed at AZO 30 nm. The AZO/Ag/AZO multilayer films of Ag 15 nm show high mobility of 26.4 ㎠/Vs and low resistivity and sheet resistance of 3.58^⁎10^-5 Ωcm and 5.0 Ω/sq. Also, the AZO/Ag (15 nm)/AZO multilayer film shows relatively high transmittance of more than 65 % in the visible region. Through this, we fabricated CZTSSe thin film solar cells with 7.51 % efficiency by improving the short-circuit current density and fill factor to 27.7 mV/㎠ and 62 %, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05b
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• pp.111-118
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• 2002

A new lithium niobate optical modulator with a polymer buffer layer on Ni in-diffused optical waveguide is proposed for the fist time, successfully fabricated and examined at a wavelength of 1.3 mm. By determining the diffusion parameters of Ni in-diffused waveguide to achieve more desirable mode size which is well matched to the mode in the fiber, the detailed results on the achievement of high optical throughput are reported. In addition, the usefulness of polymer buffer layer which can be applicable to a buffer layer in Ni in-diffused waveguide devices is demonstrated. Several sets of channel waveguides fabricated on Z-cut lithium niobate by Ni in-diffusion were obtained and on which coplanar traveling-wave type electrodes with a polymer-employed buffer layer were developed by a conventional fabrication method for characterizing of electro-optical performances of the proposed device. The experimental results show that the measured half-wave voltage is of ~10 V and the total measured fiber-to-fiber insertion loss is of ~6.4 dB for a 40 mm long at a wavelength of =1.3 mm, respectively. From the experimental results, it is confirmed that the polymer-employed buffer layer in LiNbO3 optical modulator can be a substitute material instead of silicon oxide layer which is usually processed at a high temperature of over $300^{\circ}C$. Moreover, the fabrication tolerances by using polymer materials in LiNbO3 optical modulators are much less strict in comparison to the case of dielectric buffer layer.

• Journal of Sensor Science and Technology
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• v.20 no.5
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• pp.357-362
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• 2011

This paper demonstrates a novel electrodynamic technique to remove particles from the wall of microchannels. Dielectrohporesis(DEP) is generated by applying alternating electric potentials to the interdigitated electrodes integrated at the bottom of the micro-channel. The proposed technique is applied to a general microfluidic channel as a feasibility test. To examine the wall loss reduction efficiency, 10 ${\mu}m$ diameter Polystyrene latexes(PSL) were supplied to the inlet of the device. Then, the concentration of collected particles through devices was measured. In the experiment for 10 ${\mu}m$ diameter PSL particles, the concentration of the injected particles was $174.25{\times}10^4$ particles/ml. However, the concentration of collected particles at the outlet was $52.25{\times}10^4$ particles/ml. Only 30 % of particles had arrived at the outlet and 70 % of particles had adhered to the wall of the microfluidic channel. By applying alternating electric potentials from 0 to 20 $V_{pp}$ at 3 MHz, the concentration of injected particles was 135.00${\times}10^4$ particles/ml, the concentration of collected particles was increased as $105.25{\times}10^4$ particles/ml at 20 $V_{pp}$ at the outlet. When the electric potential was 20 $V_{pp}$, the particle loss was decreased by 39 % (initial loss: 70 %, loss at 20 Vpp: 31 %) with 10 ${\mu}m$ particle. The particle loss was decreased along to the incensement of electric potentials and the enlargement of the diameter of particles. According to these measured results, it was confirmed that the proposal of using DEP technique could be a good candidate for particle loss reduction in micro-particle processing chip application. Moreover, it is expected that the proposed technique could enhance performance of microfluidic and biochip devices.

• The KIPS Transactions:PartA
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• v.17A no.3
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• pp.145-152
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• 2010

Most wearable system for mobile healthcare applications consists of three parts. The first part is the sensing elements based on bio-signal, the second is the circuit module for control, data acquisition and wireless communication and control and the third is garment with a built-in electrodes and circuits. The existing healthcare garment systems have to find a solution to signal-wire and uncomfortable and inappropriate electrode to long-term attachment. Even if the wireless communication is used for healthcare garment system, the interface between sensors and circuits have to use wires. To solve these problems, this paper use electrode using PEDOT coated PVDF nanoweb for ECG signal and PVDF film sensor for respiratory signal. And, we constructed garment network using digital yarn of 10um, and transmitted ECG and respiratory signal to mobile phone through the integrated circuit with bluetooth called station To evaluate feasibility of the proposed mobile healthcare garment system, we experimented with transmission and measurement of ECG and respiratory signal using nanoweb electrode and digital yarn. We got a successful result without noise and attenuation.

• Journal of Electrical Engineering and Technology
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• v.8 no.5
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• pp.1175-1181
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• 2013

The aim of this paper is to design and evaluate a high concentration, high penetration unipolar corona ionizer. The electrostatic characteristics in terms of voltage-current relationships of the present ionizer in the discharge zones for positive and negative coronas were discussed. Using ion current measurement, the concentration and penetration of ions were evaluated at corona voltages across the needle electrodes between 1 and 4 kV, flow rates between 1 and 5 L/min, and an operating pressure of 1 atm. In the discharge zone of the ionizer, the highest ion concentrations were found to be about $1.71{\times}10^{14}$ and $5.09{\times}10^{14}\;ions/m^3$ for positive and negative coronas, respectively. At the outlet of the ionizer, it was found that the highest ion concentration was about $1.95{\times}10^{13}$ and $1.91{\times}10^{13}\;ions/m^3$ for positive and negative coronas, respectively. The highest ion penetration for positive and negative coronas through the ionizer was found to be about 98 % and 33 %, respectively. The $N_it$ product for positive and negative coronas was also found to $1.28{\times}10^{13}$ and $7.43{\times}10^{13}\;ions/m^3s$, respectively. From the findings, this ionizer proved to be particularly useful as an aerosol charger for positive and negative charge before the detector in an electrical aerosol detector.