Fused Deposition Modeling 3D Printing-based Flexible Bending Sensor

Sun Kon Lee(이선곤),Young Chan Oh(오영찬),Joo Hyung Kim(김주형) 한국기계가공학회 2020 한국기계가공학회지 Vol.19 No.1

Recently, to improve convenience, flexible electronics are quickly being developed for a number of application areas. Flexible electronic devices comprise characters such as being bendable, stretchable, foldable, and wearable. Effectively manufacturing flexible electronic devices requires high efficiency, low costs, and simple processes for manufacturing technology. Through this study, we enabled the rapid production of multifunctional flexible bending sensors using a simple, low-cost Fused Deposition Modeling (FDM) 3D printer. Furthermore, we demonstrated the possibility of the rapid production of a range of functional flexible bending sensors using a simple, low-cost FDM 3D printer. Accurate and reproducible functional materials made by FDM 3D printers are an effective tool for the fabrication of flexible sensor electronic devices. The 3D-printed flexible bending sensor consisted of polyurethane and a conductive filament. Two patterns of electrodes (straight and Hilbert curve) for the 3D printing flexible sensor were fabricated and analyzed for the characteristics of bending displacement. The experimental results showed that the straight curve electrode sensor sensing ability was superior to the Hilbert curve electrode sensor, and the electrical conductivity of the Hilbert curve electrode sensor is better than the straight curve electrode sensor. The results of this study will be very useful for the fabrication of various 3D-printed flexible sensor devices with multiple degrees of freedom that are not limited by size and shape.

유연전자소자를 위한 차세대 유연 투명전극의 개발 동향

김주현,천민우,좌성훈,Kim, Joo-Hyun,Chon, Min-Woo,Choa, Sung-Hoon 한국마이크로전자및패키징학회 2014 마이크로전자 및 패키징학회지 Vol.21 No.2

Flexible transparent conductive electrodes (TCEs) have recently attracted a great deal of attention owing to rapid advances in flexible electronic devices, such as flexible displays, flexible photovoltanics, and e-papers. As the performance and reliability of flexible electronics are critically affected by the quality of TCE films, it is imperative to develop TCE films with low resistivity and high transparency as well as high flexibility. Indium tin oxide (ITO) has been the most dominant transparent conducting material due to its high optical transparency and electrical conductivity. However, ITO is susceptible to cracking and delamination when it is bent or deformed. Therefore, various types of flexible TCEs, such as carbon nanotube, conducting polymers, graphene, metal mesh, Ag nanowires (NWs), and metal mesh have been extensively investigated. Among several options to replace ITO film, Ag NWs and metal mesh have been suggested as the promising candidate for flexible TCEs. In this paper, we focused on Ag NWs and metal mesh, and summarized the current development status of Ag NWs and metal mesh. The several critical issues such as high contact resistance and haze are discussed, and newly developed technologies to resolve these issues are also presented. In particular, the flexibility and durability of Ag NWs and metal mesh was compared with ITO electrode.

Flexible heatsink based on a phase-change material for a wearable thermoelectric generator

Lee, Gyusoup,Kim, Choong Sun,Kim, Seongho,Kim, Yong Jun,Choi, Hyeongdo,Cho, Byung Jin Elsevier 2019 ENERGY Vol.179 No.-

<P><B>Abstract</B></P> <P>Thermoelectric generators (TEGs) represent a promising technology for self-powered wearable systems. Since the conventional TEGs have limitation to be used on the human body due to its structural rigidity, flexible TEGs have been studied and developed so that TEGs can be attached to an arbitrarily shaped surface on the human body. However, flexible TEGs require a good heatsink with good flexibility to allow them to produce enough power for wearable devices. In this study, a high-performance flexible heatsink based on a phase-change material (PCM) was proposed. PCM blocks were arranged in an array and good flexibility was realized with an elastomer that filled the space between the PCM blocks. Given that PCM can absorb a large amount of heat at the phase-change temperature, the heatsink can hold the temperature difference across the TEG constant for a relatively long period of time. Thus, the generated power from the flexible TEG was maintained at around 20 μW/cm<SUP>2</SUP> for 33 min. The flexible heatsink can be reused because the PCM solidifies at room temperature. Furthermore, the PCM-based flexible heatsink is smaller and lighter than the conventional metal heatsink. The proposed heatsink is expected to contribute to the commercialization of self-powered wearable devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A phase-change material based flexible heatsink (f-HS) is developed. </LI> <LI> Design guideline of the f-HS for wearable applications is proposed. </LI> <LI> Performance of the f-HS is better than that of the metal heatsink of the same size. </LI> <LI> A thermoelectric generator with the f-HS generates high power for 33 min. </LI> </UL> </P>

유연성 소자용 금속 전극의 신뢰성 연구 동향

김병준,Kim, Byoung-Joon 한국마이크로전자및패키징학회 2013 마이크로전자 및 패키징학회지 Vol.20 No.4

Recently, various types of flexible devices such as flexible displays, batteries, e-skins and solar cell panels have been reported. Most of the researches focus on the development of high performance flexible device. However, to realize these flexible devices, the long-term reliability should be guaranteed during the repeated deformations of flexible devices because the direct mechanical stress would be applied on the electronic devices unlike the rigid Si-based devices. Among various materials consisting electronics devices, metal electrode is one of the weakest parts against mechanical deformation because the mechanical and electrical properties of metal films degrade gradually due to fatigue damage during repeated deformations. This article reviews the researches of fatigue behavior of thin metal film, and introduces the methods to enhance the reliability of metal electrode for flexible device.

Nano-Floating Gate Memory Devices

Jang-Sik Lee 대한금속·재료학회 2011 ELECTRONIC MATERIALS LETTERS Vol.7 No.3

In recent decades, memory device technology has advanced through active research and the development of innovative technologies. Single transistor-based flash memory device is one of the most widely used forms of memory devices because their device structure is simple and the scaling is feasible. A nano-floating gate memory (NFGM) device is a kind of flash memory devices that uses nanocrystals as a charge-trapping element. The use of nanocrystals has advantages over memory devices that rely on other methods such as discontinuous trap sites and controllable trap levels. Nowadays considerable progress has been made in the field of NFGM devices, and novel application areas have been explored extensively. This review article focuses on new technologies that are advancing these developments. The discussion highlights recent efforts and research activities regarding the fabrication and characterization of nonvolatile memory devices that use a nanocrystal layer asa charge-trapping element. The review concludes with an analysis of device fabrication strategies and device architectures of NFGM devices for possible applicationto devices that are organic, printed, and flexible.

플렉서블 디스플레이 디바이스(상품) 신시장 창출을 위한 차세대사용자 의식조사 연구

이철호 ( Lee Cheol Ho ),정형기 ( Jung Hyeong Gi ) 한국상품문화디자인학회 2016 상품문화디자인학연구 Vol.46 No.-

In the 2000s, flexible display is considered to expand in various areas of society, including medical service, health, and infotainment. In addition, it is expected to apply rapidly flexible display to digital device design convergence technology, infotainment and game design convergence technology, and industrial and military design convergence technology. In particular, flexible display devices appearing at the time when smart devices type changed from ``belonging`` to ``wearing`` are accepted to be the best alternative to solve national impending issues, such as the creation of a new market in each industrial area, the drive engine for the future new growth, and the creation of the next-generation jobs. From the perspective, the purose of this study is to survey and analyze the next-generation users`` perception in order to create the new market of flexible display, and to lay the foundation for finding the direction of the future flexible display R&D technology and design convergence R&D. The study method and scope are presented as follows: First, related work and theoretical research are performed to find the domestic and foreign research trend of flexible display and to predict the expected effects. Secondly, by analyzing the perception of the next-generation users of flexible display devices and their attitudes, this study provides an empirical material necessary for setting the direction for the leading development of futuristic flexible display devices and establishing a system. More specifically, the survey on the next-generation users` perception of wearable devices is descriptive statistics of SAS 9.3 Chi-square & Fisher``s Exact Test Questionnaire. For reliable and valid questionnaire survey, Cronbach`s technique which is the most proper statistical method for all processes, including survey plan, questionnaire, sampling, main survey, data input, and data analysis, was applied. Based on that, statistical significance was analyzed. Thirdly, the study subjects participating in the questionnaire survey were 80 university students in their 20s living in the metropolitan areas, who are the main next-generation users of flexible display devices. They had person-to-person in-depth interview. The questionnaire items include information understanding, interest, a degree of interest desire, a degree of purchase desire, purchase purpose, purchase factor, purchase region, non-purchase factor, something to improve in non-purchase case, and purchase intention when improved. The study drew the following conclusions: In the questions about information understanding, interest, a degree of interest desire, a degree of purchase desire, purchase purpose, purchase factor, purchase region, non-purchase factor, something to improve in non-purchase case, and purchase intention when improved, they answered positively regardless of gender, and their answers were statistically significant. The reliability of each question was high. The correlation between questions was not independent, but was found. The most important factors of non-purchase of the next-generation users were found to be price, design, and interface. Therefore, it is necessary to improve them.

Enhancing the stretch ratio of a vertically stacked wavy circuit in stretchable devices

Oluwabukola Adebisi,윤정훈 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.4

Recently, improving the integrity of stretchable wavy circuits in flexible devices has become important and stacking wavy circuits is a prominent issue observed in flexible devices. This study aims to increase the maximum stretch ratio of vertically stacked wavy circuits in stretchable devices. Various parameters of the stretching stack of wavy circuits have been studied in the literature, including the stacking distance, thickness of the wavy section, and tilting angle of the circuit. This study indicates that tightly stacked wavy circuits have a higher maximum stretch ratio compared to the sparsely stacked samples. Moreover, an increase in the tilting angle increases the maximum stretch ratio of the wavy circuit as the thickness of the wavy circuit increases as well.

A new approach to high-performance flexible supercapacitors: Mesoporous three-dimensional Ni-electrodes

Kim, Sun-I.,Kang, Ji-Hun,Kim, Sung-Wook,Jang, Ji-Hyun Elsevier 2017 Nano energy Vol.39 No.-

<P><B>Abstract</B></P> <P>The demand for portable electronic devices is driving the development of flexible supercapacitor, while current devices still need to improve the performance for practical applications. Here, we report a cost-efficient flexible three-dimensional-Ni (3D-Ni) electrode for a flexible supercapacitor with excellent energy density and power density. The meso-porous 3D-Ni electrode provides a large number of active sites to store charges and good accessibility to the ions in polymer electrolytes, leading to excellent capacitance, high energy density, as well as high power density. The Ni(OH)<SUB>2</SUB>/3D-Ni positive electrode showed an outstanding specific capacitance of ~3400F/g at 10A/g and retained 80% of the initial capacitance at 200A/g. The negative MnO<SUB>2</SUB>/3D-Ni electrode exhibited a specific capacitance of 1250F/g at 10A/g and excellent capacitance retention of 82% at 200A/g. The Ni(OH)<SUB>2</SUB>/3D-Ni//MnO<SUB>2</SUB>/3D-Ni hybrid supercapacitor delivered an excellent energy density of 75Wh/kg and a high power density of 5.3kW/kg, and these values did not change under bending conditions. The 3D-Ni electrode introduced here represents a new type of ideal electrode that can be easily applied to various flexible/wearable electronic device with excellent performance.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The flexible solid-state supercapacitor delivered an outstanding specific capacitance of ~3400F/g at 10A/g, an excellent energy density of 75Wh/kg, and a high power density of 5.3kW/kg. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>The highly meso-porous 3D-Ni electrode provides a large number of active sites to store charges and provide good accessibility to the ions in electrolytes, leading to excellent electrochemical performance. The Ni(OH)2/3D-Ni electrode showed an outstanding specific capacitance of ~3400F/g at 10A/g and retained 80% of the initial capacitance at 200A/g. The flexible hybrid supercapacitor delivered an excellent energy density of 75Wh/kg and a high power density of 5.3kW/kg.</P> <P>[DISPLAY OMISSION]</P>

Metal grid technologies for flexible transparent conductors in large-area optoelectronics

Fakharan Zahra,Dabirian Ali 한국물리학회 2021 Current Applied Physics Vol.31 No.-

Mechanically flexible optoelectronic devices such as flexible displays, touch-screens, wearable electronics and solar cells are attracting significant commercial interest. In these devices, a transparent conductor is an essential element that delivers or collects the electrical current to the active material while it allows light to enter or exit from the device. The transparent conductor is composed of a transparent conductive film and a metallic grid providing electrical conduction over the large area. In this article, we review the established processes used by the industry as well as emerging solution-based methods for processing metal grids. Furthermore, we review the issues and potentials of these emerging processes facing for large-area deployment. In the final section, we evaluate three applications of flexible transparent conductors in: perovskite-based solar cells, organic light emitting diodes and electrochromic windows.

Flexible Thermoelectric Device Using Thick Films for Energy Harvesting from the Human Body

Cho, Han Ki,Kim, Da Hye,Sin, Hye Sun,Cho, Churl-Hee,Han, Seungwoo The Korean Ceramic Society 2017 한국세라믹학회지 Vol.54 No.6

A flexible thermoelectric device using body heat has drawn attention as a power source for wearable devices. In this study, thermoelectric thick films were fabricated by cold pressing method using p-type antimony telluride and n-type bismuth telluride powders in accordance with specific loads. Thermoelectric thick films were denser and improved the electrical and thermoelectric properties while increasing the load of the cold pressing. The thickness of the specimen can be controlled by the amount of material; specimens were approximately 700 um in thickness. Flexible thermoelectric devices were manufactured by using the thermoelectric thick films on PI (Polyimide) substrate. The process is cheap, efficient, easy and scalable. Evaluation of power generation performance and flexibility on the fabricated flexible thermoelectric device was carried out. The flexible thermoelectric device has great flexibility and good performance and can be applied to wearable electronics as a power source.