• Composites Research
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• v.36 no.3
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• pp.224-229
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• 2023

Due to the increasing demand for wearable devices and miniaturization of various electronic devices, the trend of nanofabrication in IT devices is underway. In order to overcome the limitations of battery size and capacity, there has been a lot of research interest in energy harvesting technology, also known as triboelectric nanogenerator. AAO(Anodic Aluminum oxide) coated with fluoride is a structure that includes an anode layer with high properties in the triboelectric series, an dielectric layer that helps transfer the triboelectrically generated charges to the electrode without loss, and the electrode. For these reasons, AAO has been a lot of research on its application to frictional energy harvesting nanogenerators. In this work, we analyzed the correlation of AAO between the surface morphology and thickness of the insulating layer by utilizing aluminum oxide, which is advantageous for the application of triboelectric nanogenerators, and adjusting the thickness of the insulating layer.

• Journal of the Microelectronics and Packaging Society
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• v.25 no.3
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• pp.49-53
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• 2018

Since various methods to form well-aligned nano-/micro- patterns are underlying technologies to fabricate next generation wearable electronic devices, many efforts have been made to realize finer patterns in recent years. Among lots of patterning methods, the present invention includes a nano-transfer printing (n-TP) process which is advantageous in that a processing cost is low and high-resolution patterns can be formed within a short processing time. We successfully achieved pattern formation of highly ordered Pt lines with line-width of 250 nm, 500 nm, and $1{\mu}m$ on transparent and flexible substrates. In addition, we analyzed the durability of the patterns, showing excellent stability of line-shape even after a physical and repeated bending test of 500 times using a bending machine. As a result, it is expected that a n-TP process is very useful for forming various metal patterns, and it is also expected to be applied to wiring and interconnection technology of next generation flexible electronic devices.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2019.05a
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• pp.510-512
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• 2019

Recently, there have been growing requirements in the public safety sector to ensure safety through detection of hazardous situations or preemptive predictions. It is noteworthy that various sensor data can be analyzed and utilized as a result of mobile device's dissemination, and many advantages can be used in terms of safety and security. An effective modeling technique is needed to combine sensor data generated by smart-phones and wearable devices to analyze users' moving patterns and behavioral patterns, and to ensure public safety by fusing location-based crime risk data provided.

• Transactions of the KSME C: Technology and Education
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• v.5 no.1
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• pp.1-6
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• 2017

From early simple bulky detectors to show the existence of some specific material, sensor has been developed to miniature smart sensors embedded signal capabilities with a help of nano/micro engineering such as innovative nano materials and semiconductor process technologies. Due to recently fast sales of smart phones with simple telephone function plus many sensors, internet accessing capabilities, easy user downloadable "app" softwares, smart sensor industry market has expanded very fast. If driver-less cars, wearable electronic devices and smart robots will be introduced into market in near future, development of many various smart sensors will be needed.

• Ceramist
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• v.21 no.4
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• pp.312-330
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• 2018

Energy storage/conversion has become crucial not only to meet the present energy demand but also more importantly to sustain the modern society. Particularly, electrical energy storage is critical not only to support electronic, vehicular and load-levelling applications but also to efficiently commercialize renewable energy resources such as solar and wind. While Li-ion batteries are being intensely researched for electric vehicle applications, there is a pressing need to seek for new battery chemistries aimed at stationary storage systems. In this aspect, Zn-ion batteries offer a viable option to be utilized for high energy and power density applications since every intercalated Zn-ion yields a concurrent charge transfer of two electrons and thereby high theoretical capacities can be realized. Furthermore, the simplicity of fabrication under open-air conditions combined with the abundant and less toxic zinc element makes aqueous Zn-ion batteries one of the most economical, safe and green energy storage technologies with prospective use for stationary grid storage applications. Also, Zn-ion batteries are very safe for next-generation technologies based on flexible, roll-up, wearable implantable devices the portable electronics market. Following this advantages, a wide range of approaches and materials, namely, cathodes, anodes and electrolytes have been investigated for Zn-ion batteries applications to date. Herein, we review the progresses and major advancements related to aqueous. Zn-ion batteries, facilitating energy storage/conversion via $Zn^{2+}$ (de)intercalation mechanism.

• Journal of Information Processing Systems
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• v.16 no.6
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• pp.1238-1249
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• 2020

Throughout the world, aging populations and doctor shortages have helped drive the increasing demand for smart healthcare systems. Recently, these systems have benefited from the evolution of the Internet of Things (IoT), big data, and machine learning. However, these advances result in the generation of large amounts of data, making healthcare data analysis a major issue. These data have a number of complex properties such as high-dimensionality, irregularity, and sparsity, which makes efficient processing difficult to implement. These challenges are met by big data analytics. In this paper, we propose an innovative analytic framework for big healthcare data that are collected either from IoT wearable devices or from archived patient medical images. The proposed method would efficiently address the data heterogeneity problem using middleware between heterogeneous data sources and MapReduce Hadoop clusters. Furthermore, the proposed framework enables the use of both fog computing and cloud platforms to handle the problems faced through online and offline data processing, data storage, and data classification. Additionally, it guarantees robust and secure knowledge of patient medical data.

• Journal of the Korean Applied Science and Technology
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• v.36 no.4
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• pp.1253-1258
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• 2019

The solid-state electrolyte based on polymer is applicable to various electrochemical devices including supercapacitor, battery, sensor, actuator and has great attention to develop its ionic conductivity from conventional polymer electrolyte by uisng wide range of ionic liquids. The research about ion gel as a solid state electrolyte with the ionic liquid has focused on the wearable and flexible electronic device to use as the high electrical and electrochemical performances, mechanical strength of polymer. In this work, we have investigated and developed solid-state electrolyte based on the ionic liquid and polymer with enhanced ionic conductivity and stability.

• Journal of Sensor Science and Technology
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• v.27 no.3
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• pp.186-191
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• 2018

Smart textile industries have been precipitously developed and extended to electronic textiles and wearable devices in recent years. In particular, owing to an increasingly aging society, the elderly healthcare field has been highlighted in the smart device industries, and pressure sensors can be utilized in various elderly healthcare products such as flooring, mattress, and vital-sign measuring devices. Furthermore, elderly healthcare products need to be more lightweight and flexible. To fulfill those needs, textile-based pressure sensors is considered to be an attractive solution. In this research, to apply a textile to the second layer using a pressure sensing device, a novel type of conductive textile was fabricated using vapor phase polymerization of poly(3,4-ethylenedioxythiophene) (PEDOT). Vapor phase polymerization is suitable for preparing the conductive textile because the reaction can be controlled simply under various conditions and does not need high-temperature processing. The morphology of the obtained PEDOT-conductive textile was observed through the Field Emission Scanning Electron Microscope (FESEM). Moreover, the resistance was measured using an ohmmeter and was confirmed to be adjustable to various resistance ranges depending on the concentration of the oxidant solution and polymerization conditions. A 3-layer 81-point multi-pressure sensor was fabricated using the PEDOT-conductive textile prepared herein. A 3D-viewer program was developed to evaluate the sensitivity and multi-pressure recognition of the textile-based multi-pressure sensor. Finally, we confirmed the possibility that PEDOT-conductive textiles could be utilized by pressure sensors.

• Journal of the Microelectronics and Packaging Society
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• v.21 no.4
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• pp.15-24
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• 2014

Recently, a variety of printing technologies, including ink jet, gravure, and roll-to-roll (R2R) printing, has generated intensive interest in the application of flexible and wearable electronic devices. However, the actual use of printing technique is much limited because the sintering process of the printed nanoparticle inks remains as a huge practical drawback. In the fabrication of the conductive metal film, a post-sintering process is required to achieve high conductivity of the printed film. The conventional thermal sintering takes considerable sintering times, and requires high temperatures. For application to flexible devices, the sintering temperature should be as low as possible to minimize the damage of polymer substrate. Several alternative sintering methods were suggested, such as laser, halogen lamp, infrared, plasma, ohmic, microwave, and etc. Eventually, the new sintering technique should be applicable to large area, R2R, and polymer substrate as well as low cost. This article reviews progress in recent technologies for several sintering methods. The advantages and disadvantages of each technology will be reviewed. Several issues for the application in R2R process are discussed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.3
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• pp.569-575
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• 2020

Recently, research on renewable energy technologies has come into the spotlight due to rising concerns over the depletion of fossil fuels and greenhouse gas emissions. Demand for portable electronic and wearable devices is increasing, and electronic devices are becoming smaller. Energy harvesting is a technology for overcoming limitations such as battery size and usage time. In this paper, the V-I characteristic curve and internal resistance of thermal electric devices were analyzed, and MPPT control methods were compared. The Perturbation and Observation (P&O) control method is economically inefficient because two sensors are required to measure the voltage and current of a Thermoelectric Generator(TEG). Therefore, this paper proposes a new MPPT control method that tracks MPP using only one sensor for the regulation of the output voltage. The proposed MPPT control method uses the relationship between the output voltage of the load and the duty ratio. Control is done by periodically sampling the output voltage of the DC-DC converter to increase or decrease the duty ratio to find the optimal duty ratio and maintain the MPP. A DC-DC converter was designed using a cascaded boost-buck converter, which has a two-switch topology. The proposed MPPT control method was verified by simulations using PSIM, and the results show that a voltage, current, and power of V=4.2 V, I=2.5 A, and P=10.5 W were obtained at the MPP from the V-I characteristic curve of the TEG.