원자 현미경에서 마찰력 측정을 위한 새로운 실험 기법

최덕현(Dukhyun Choi),황운봉(Woonbong Hwang),윤의성(Euisung Yoon),김준원(Joonwon Kim),김동식(Dongsik Kim) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.11

A new method has been proposed for the calibration of frictional forces in atomic force microscopy. Angle conversion factor is defined using the relationship between torsional angle and frictional signal. Once the factor is obtained from a cantilever, it can be applied to other cantilevers without additional experiments. Moment balance equations on the flat surface and top edge of a commercial step grating are used to obtain angle conversion factor. Proposed method is verified through another step grating test and frictional behavior of Mica.

원자 현미경을 이용한 접촉 면적에 따른 마찰 및 마멸 특성 분석

최덕현(Dukhyun Choi),황운봉(Woonbong Hwang) Korean Society for Precision Engineering 2004 한국정밀공학회지 Vol.21 No.12

Recently, it has been reported that frictional behavior at nanometer scale can be different from that at macro scale. In this article, friction and wear tests were conducted using an AFM to investigate the effect of real contact area on the coefficient of friction and wear property. SiO₂, Mica, and SiGe were used in friction test and the AFM tip was Si₃N₄.The real contact area between an AFM tip and flat surface was calculated by the Johnson-Kendall-Roberts (JKR) theory. Wear specimen was Mica, and the diamond tip was used. We found that the coefficient of friction is constant below a critical area, but it is degraded over the area. Moreover, it is found that wear depth increased rapidly from a certain load and was degraded as a function of the number of the scanning cycles. Also, the range of scanning velocity used in this study had little effect on the wear depth.

정전 발전 기반 소프트 로봇 응용 최신 기술

성정빈 ( Zhengbing Ding ),최덕현 ( Dukhyun Choi ) 한국복합재료학회 2022 Composites research Vol.35 No.6

마찰전기 나노발전기(이하 TENG)의 새로운 발전 기술은 에너지 수집 및 자가 전력 공급 감지 응용 분야의 긍정적 전망으로 인해 점점 더 많은 관심을 받고 있다. 또한 최근 소프트로봇의 부상은 플렉시블과 소프트센서, 액추에이터 개발에 대한 폭넓은 관심을 불러 일으키고 있다. TENG는 액추에이터와 자가 전력 공급 센서를 구동하는 유망한 전원으로 간주되어 소프트웨어 로봇, 소프트 센서 및 액추에이터 개발을 위한 독창적인 방법을 제공한다. 이 리뷰에서는 TENG를 기반으로 다양한 형태와 기능을 가진 소프트웨어 로봇을 소개하려 한다. 그 중 자연계의 구조, 표면 형태, 재료 특성과 센싱/발전 메커니즘을 모방한 바이오닉 소프트 로봇의 설계는 TENG 성능 향상에 큰 도움이 되었다. 또한 다양한 바이오닉 소프트 로봇은 TENG의 간단한 구조, 자체 전력 공급 특성 및 조정 가능한 출력으로 인해 이전 구동 방식보다 향상되었다. 그리하여 이 리뷰에서는 TENG가 활성화한 소프트 로봇 응용의 특정 핵심 영역에서 다양한 연구를 종합적으로 검토하려 한다. 리뷰를 요약하자면 먼저 최근 개발된 다양한 TENG 기반 소프트웨어 로봇을 정리하고 다양한 장비 구조, 표면 형태 및 자연적으로 영감을 받은 재료를 비교 분석하여 그에 따른 TENG 성능 개선을 수행한다. 자연계에 사용되는 다양한 유비쿼터스 감지 원리와 발전 메커니즘 및 유사한 인공 TENG 설계가 확인되었고 촉각 디스플레이 및 웨어러블 기기, 인공 전자 피부 등의 기기에 TENG를 활성화하는 바이오닉 응용에 대해 논의한다. 마지막으로 TENG 기반 센서 및 구동 장비의 로봇 실제 적용에 대한 발전 기회, 도전 및 미래 전망을 분석한다. As an emerging power generation technology, triboelectric nanogenerators (TENGs) have received increasing attention due to their boundless promise in energy harvesting and self-powered sensing applications. The recent rise of soft robotics has sparked widespread enthusiasm for developing flexible and soft sensors and actuators. TENGs have been regarded as promising power sources for driving actuators and self-powered sensors, providing a unique approach for the development of soft robots with soft sensors and actuators. In this review, TENG-based soft robots with different morphologies and different functions are introduced. Among them, the design of biomimetic soft robots that imitate the structure, surface morphology, material properties, and sensing/generating mechanisms of nature has greatly benefited in improving the performance of TENGs. In addition, various bionic soft robots have been well improved compared to previous driving methods due to the simple structure, self-powering characteristics, and tunable output of TENGs. Furthermore, we provide a comprehensive review of various studies within specific areas of TENG-enabled soft robotics applications. We first explore various recently developed TENG-based soft robots and a comparative analysis of various device structures, surface morphologies, and nature-inspired materials, and the resulting improvements in TENG performance. Various ubiquitous sensing principles and generation mechanisms used in nature and their analogous artificial TENG designs are demonstrated. Finally, biomimetic applications of TENG enabled in tactile displays as well as in wearable devices, artificial electronic skin and other devices are discussed. System designs, challenges and prospects of TENGs-based sensing and actuation devices in the practical application of soft robotics are analyzed.

유연한 광학전기소자용 ZnO 의 제작 및 특성 연구

유진호(Jin ho You),최덕현(Dukhyun Choi),이상민(Sang min Lee) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10

This paper presents the fabrication of zinc oxide (ZnO) nanorods with various structures by aqueous solution method (ASM) and the characterization of their optical properties. ZnO nanorods with various structures were prepared by controlling the thickness of seed layers and the temperature of main growth. We measured the array shape and growth direction of the fabricated ZnO by scanning electron microscope (SEM), and their optical properties by UV-visible spectrophotometer. We confirmed that their optical properties could be controlled by the density and diameter of ZnO nanorods. Since our strategy can be applied to flexible large-area optical electronics, it may provide a wide range of opportunities for piezoelectric energy generator and transparency solar cell.

유수분리 기술의 최신 동향

박홍렬 ( Hong Ryul Park ),황운봉 ( Woonbong Hwang ),최덕현 ( Dukhyun Choi ) 한국복합재료학회 2023 Composites research Vol.36 No.2

유수분리는 석유 생산, 폐수 처리 및 식품 가공을 포함한 다양한 산업 응용 분야와 해양 기름 유출과 같은 환경 분야에서 중요한 과정이다. 물-기름 혼합물의 분리 효율은 혼합물의 유형, 기름과 물의 상태, 적용하고자 하는 기술을 포함한 여러 요인에 의해 영향을 받을 수 있으며, 수년에 걸쳐 물리적, 화학적 및 생물학적 방법으로 물과 기름을 분리하기 위한 다양한 기술이 개발되어 오고 있다. 본 논문은 중력에 의한 분리, 원심 분리, 흡착재, 필터 등을 이용한 유수분리를 포함하여 물-기름 분리에 사용할 수 있는 다양한 방법과 기술에 대해 개략적으로 설명하고자 한다. 각 방법의 장점과 한계를 최근 연구 동향 및 향후 전망과 함께 논의한다. 또한 본 논문에서는 지속 가능하고 환경 친화적인 접근 방식에 특히 중점을 두고 유수분리 분야의 향후 연구와 산업 적용을 위한 방향성을 제시하고자 한다. 결론적으로 본 논문에서는 유수분리 분야의 연구자 및 산업 종사자에게 유용할 수 있는 최근 유수 분리 기술에 대한 포괄적인 개요를 제공하고자 한다. Oil-water separation is a critical process for several industrial applications, including oil production, wastewater treatment, food processing, and environmental area such as marine oil spills. The separation efficiency of oil-water mixtures can be influenced by various factors such as mixture composition, oil and water conditions, and the separation technology used. Over the years, various technologies have been developed to separate water and oil by physical, chemical and biological methods. This paper presents an overview of the various methods and technologies available for oil-water separation, including gravity separation, centrifugal separation, and separation using adsorbents, filters. The strengths and limitations of each method are discussed, along with recent research trends and future prospects. Furthermore, this paper aims to provide direction for future research and industrial application of sustainable and environmentally friendly oil-water separation technologies. In conclusion, we provide a comprehensive overview of recent oil-water separation technologies that will be beneficial to researchers and industrialists in the field of oil-water separation.

고효율 회전형 정전 나노 발전기의 기구학적 설계

이지현 ( Jihyun Lee ),나성민 ( Seongmin Na ),최덕현 ( Dukhyun Choi ) 한국전기전자재료학회 2024 전기전자재료학회논문지 Vol.37 No.1

A triboelectric nanogenerator is a promising energy harvester operated by the combined mechanism of electrostatic induction and contact electrification. It has attracting attention as eco-friendly and sustainable energy generators by harvesting wasting mechanical energies. However, the power generated in the natural environment is accompanied by low frequencies, so that the output power under such input conditions is normally insufficient amount for a variety of industrial applications. In this study, we introduce a non-contact rotational triboelectric nanogenerator using pedaling and gear systems (called by P-TENG), which has a mechanism that produces high power by using rack gear and pinion gear when a large force by a pedal is given. We design the system can rotate the shaft to which the rotor is connected through the conversion of vertical motion to rotational motion between the rack gear and the pinion gear. Furthermore, the system controls the one directional rotation due to the engagement rotation of the two pinion gears and the one-way needle roller bearing. The TENG with a 2 mm gap between the rotor and the stator produces about the power of 200 __ and turns on 82 LEDs under the condition of 800 rpm. We expect that P-TENG can be used in a variety of applications such as operating portable electronics or sterilizing contaminated water.

ITO-based flexible electronics with optimized bendability using neutral axis engineering

Daesung Yoon(윤대성),Sangmin Lee(이상민),Woonbong Hwang(황운봉),Dukhyun Choi(최덕현) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10

The importance of flexibility for electronic devices have been emphasized for future potable and wearable electronics, and the buffer material has been employed to increase their bendability. However, because the material property and geometry of a buffer layer could be different for the purpose of the electronic devices, the bendability optimization of the flexible electronic devices is needed depending on the thickness and elastic modulus of that. Here, we report a design rule to optimize the bendability of ITO-based flexible electronics by neutral axis (NA) engineering, considering the correlation between the thickness and the elastic modulus of the buffer layer. Thus, our strategy may provide great advantages for flexible electrodic devices such as organic solar cells, organic light emitting diodes, and organic transistor.

초소수성 PMN-PT 표면에서의 액적 충돌을 통한 파이로 전력 생산

한정훈(Jeonghoon Han),오승태(Seungtae Oh),황희재(Hee Jae Hwang),최덕현(Dukhyun Choi),이충엽(Choongyeop Lee),남영석(Youngsuk Nam) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11

Single crystalline pyroelectric materials offers new opportunities for efficient thermal energy harvesting utilizing temperature fluctuation. Recent works have demonstrated the pyroelectric generators utilizing various thermal energy such as body heat and latent heat of fluids. However, the sustainable and high performance pyroelectric thermal harvesting has not been realized yet. In this work, we introduce the pyroelectric generator utilizing the rapid temperature fluctuation during a droplet impact. The thin single-crystalline PMN-PT of 100 μm thickness was incorporated to the generator in order to improve the pyroelectric coefficient with reducing the thermal mass. Based on the measured pyroelectric current and voltage values, the pyroelectric current prediction model was developed utilizing the correlation of the maximum spreading diameter during drop impact. We believe this work will help to develop efficient pyroelectric thermal energy harvesters.

액적 충돌 기반 고출력 초발수 초전 발전기

한정훈(Jeonghoon Han),신성종(Seongjong Shin),오승태(Seungtae Oh),황희재(Hee Jae Hwang),최덕현(Dukhyun Choi),이충엽(Choongyeop Lee),남영석(Youngsuk Nam) 대한기계학회 2024 대한기계학회 춘추학술대회 Vol.2024 No.4