• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.606-606
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• 2013

ZnO nanowire를 기반으로 하는 nanogenerator는 미세한 움직임을 전기 에너지로 변환 시키는 압전 에너지 하베스팅 기술로 기존 에너지 하베스터와 비교하여 사용환경의 제약이 적고, 소형화가 가능한 장점으로 주목을 받고 있다. 특히 혈류, 심장박동, 호흡 등 인체 활동 에너지를 이용한 발전 소자 등의 활용이 가능하여 활발한 연구가 진행되고 있다. 하지만, 최근 발표된 film like generator나 lateral 구조의 nanogenerator는 nanowire의 구조 취약성으로 인해 내구성이 좋지 못한 단점이 있다. 본 연구에서는 nanogenerator의 내구성을 향상시키기 위해 capping layer로 실리콘 계 유무기 하이브리드를 적용하고자 하였다. 또한 상부 전극을 CNT-Ag소재로 대체하여 유연기판에 대응코자 하였다. 코팅 물질 및 코팅 방법을 최적화하고, 내구성 테스트를 실시하였고, 소자의 발전 특성은 PVDF generator와 비교분석하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.283.1-283.1
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• 2013

ZnO nanowire를 기반으로 하는 nanogenerator는 미세한 움직임을 전기 에너지로 변환 시키는 압전 에너지 하베스팅 기술로 기존 에너지 하베스터와 비교하여 사용환경의 제약이 적고, 소형화가 가능한 장점으로 주목을 받고 있다. 특히 혈류, 심장박동, 호흡 등 인체 활동 에너지를 이용한 발전 소자 등의 활용이 가능하여 활발한 연구가 진행되고 있다. 하지만, 최근 발표된 film like Vertical 구조의 nanogenerator는 nanowire의 구조 취약성으로 인해 내구성이 좋지 못한 단점이 있다. 또한 ZnO nanowire의 내부 O2 결함 및 표면 OH-기의 흡착에 의한 특성 저하가 나타난다. 본 연구에서는 nanogenerator의 내구성을 향상시키기 위해 capping layer로 실리콘 계 유무기 하이브리드를 적용하여 코팅 물질 및 코팅 방법을 최적화 하였으며 상부 전극을 CNT-Ag nanowire 소재로 대체하여 유연기판에 대응코자 하였다. 또한 APP(Atmosphere Pressure Plasma)와 ICP(Inductively Coupled Plasma)장비를 사용하여 ZnO nanowire를 표면처리하였고, 각각의 플라즈마 표면처리의 영향에 대해 조사하였다. XPS를 통하여 OH-기의 제거 유무를 확인하였으며, 소자의 발전 특성의 향상을 확인 하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.5
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• pp.719-730
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• 2021

We have demonstrated a sandwich-type ZnO-based piezoelectric energy harvesting nanogenerator, namely ZCZ-NG device, composed of symmetrically stacked layers of ZnO/carbon tape/ZnO structure. Especially, we have adopted a conductive double-sided adhesive carbon tape in an effort to fabricate a high-quality ZCZ-NG device, leading to its superior output performance in terms of the peak-to-peak output voltage. Effects of the device size, ZnO layer thickness, and bending strain rate on the device performance have been investigated by measuring the output voltage. Moreover, to evaluate the effectiveness of the fabricated ZCZ-NG devices, we have experimentally implemented a sensor network testbed which can utilize the output voltages of ZCZ-NG devices. This sensor network testbed consists of several components such as Arduino-based transmitter and receiver nodes, wirelessly transmitting the sensed information of each node. We hope that this research combining the ZnO-based energy harvesting devices and IoT sensor networks will contribute to the development of more advanced energy harvester-driven IoT sensor networks in the future.

• Electronics and Telecommunications Trends
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• v.25 no.5
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• pp.11-19
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• 2010

유비쿼터스 시대의 모바일 전력원으로서 가장 유용한 리튬이차전지의 충전방식은 1991년 리튬이온전지의 상용화 이후 정전류-정전압 방식의 충전법이 고수되어 왔다. 그러나 압전, 열전 등 신재생에너지에 의한 에너지 하베스팅으로 생성되는 전력의 성질이 전압과 전류의 범위가 매우 다양하므로 효율적으로 저장할 수 있는 에너지 매니지먼트 체계가 필요하다. 이에 대한 기반연구로서 리튬이차전지의 고효율 충전을 위한 다양한 방식이 고려되어 왔으며, 본 동향분석서에서는 이러한 충전방식에 따라 리튬이차전지 내부 소재가 받는 영향과 여러 충전방식의 장단점을 분석하고, 최적 충전방식의 기준을 정리한다.

• The Journal of the Acoustical Society of Korea
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• v.43 no.2
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• pp.168-177
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• 2024

When designing an underwater Piezoelectric Energy Harvester (PEH), Vortex Induced Vibration (VIV) is generated throughout the cantilever through a change in curvature, and the generation of VIV increases the vibration displacement of the curved cantilever PEH, which is an important factor in increasing actual power. The material of the curved PEH selected a Polyvinyline Di-Floride (PVDF) piezoelectric film, and the flow velocity is set at 0.1 m/s to 0.50 m/s for 50 mm, 130 mm, and 210 mm with various curvatures. The strain energy change of PEH by VIV was observed. The smaller the radius of curvature, the larger the VIV, and as the flow rate increased, more VIV appeared. Rapid shape transformation due to the small curvature was effective in generating VIV, and strain energy, normalized voltage, average power, etc. To increase the amount of power of the PEH, it is considered that the average power will increase as the number of curved PEHs increases as well as the steep curvature is improved.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.34 no.2
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• pp.90-98
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• 2021

Piezoelectric ceramic fiber composite (PCFC) was fabricated using a planar electrode printed piezoelectric ceramic fiber driven in transverse mode for small-scale wind energy harvester applications. The PCFC consisted of an epoxy matrix material and piezoelectric ceramic fibers sandwiched by interdigitated electrode (IDE) patterned polyimide films. The PCFC showed an excellent mechanical performance under a continuous stress. For the fabrication of PCB cantilever harvester, five -PCFCs were vertically attached onto a flexible printed circuit board (PCB) substrate, and then PCFCs were serially connected through a printed Cu circuit. The energy harvesting performance was evaluated applying an inverted structure, which imples its free leading edge located at an open end but the trailing edge at a clamped end, to enhance strain energy in a wind tunnel. The output voltage of the PCB cantilever harvester was increased as the wind speed increased. The maximum output power was 17.2 ㎼ at a resistance load of 200 ㏀ and wind speed of 9 m/s. It is considered that the PCB cantilever energy harvester reveals a potential use for wind energy harvester applications.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.1
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• pp.89-94
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• 2018

This paper investigated the design method of the smart sensor for implementing IoT (Internet of Things) service. The power supply of sensor consistently acquisting data is based on the energy harvesting technology and designed with piezoelectric transducer not affected by surrounding circumstances. The wireless communication interface for the transmission of data is designed with BLE (Bluetooth Low Energy). BLE is highly adequate wireless communication technology for low power consumption and short distance wireless communication. The main application of BLE is beacon whose usage range is extended from O2O (Online to Offline) service, navigator based on indoor positioning technology, and anti-theft/lost child prevention service to mobile game. This paper studied the method to extend wireless coverage for complementing the short wireless transmission distance of BLE. The wireless sensor network based on CATV network is proposed for the easy construction of BLE sensor network and extended wireless coverage.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.477-480
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• 2015

In this paper a low-voltage vibration energy harvesting circuit with MPPT(Maximum Power Point Tracking) control is proposed. By employing bulk-driven technique, the minimum operating voltage of the proposed circuit is as low as 0.8V. The designed MPPT control circuit traces the maximum power point by periodically sampling the open circuit voltage of a full-wave rectifier circuit connected to the piezoelectric device output and delivers the maximum available power to load. The proposed circuit is designed using a $0.35{\mu}m\;CMOS$ process, and the chip area including pads is $1.33mm{\times}1.31mm$. Simulation results show that the maximum power efficiency of the designed circuit is 85.49%.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.9
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• pp.1347-1356
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• 2022

In this paper, we investigate the properties of CoGe thin film-based galvanic cells as a function of their dimension (cell length, width, etc.) and show their application as sensors to Arduino-based IoT sensor networks to detect water contact. Because these CoGe thin film-based galvanic cells do not require mechanical strains or temperature gradients unlike piezoelectric and thermoelectric energy harvesters, we think that these thin film-based galvanic cells are more suitable for self-powered sensor networks demanding sustainable and robust energy harvesters. In the past, a sputter-deposited CoGe thin film has not been intensively investigated for energy harvesting appilcations. Thus, in this study, we perform a feasibility study of galvanic cells composed of a sputter-deposited CoGe thin film to see if they can be applied as potential self-powered sensors. We believe that this paper will be of great help in developing even more enhanced sensor networks.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.277-277
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• 2009

In this paper, PMPG (Piezoelectric Micro Power Generator) was investigated by ANSYS FEA (Finite Element Analysis) to decrease operating frequency and improve out power. The micro power generator was designed to convert ambient vibration energy to electrical power as a ZnO piezoelectric material. To find optimal model in low vibration ambient, the shape of power generator was changed with different membrane width, thickness, length, and proof mass size. Used the ANSYS modal analysis, bending mode and stress distribution of optimal model were analyzed. Also, the displacement with the frequency range was analyzed by harmonic analysis. From the simulation results, the resonance frequency of optimal model is about 373 Hz and confirmed the possibility of ZnO micro power generator for wireless sensor node applications.