• Korean Journal of Materials Research
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• v.29 no.6
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• pp.371-377
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• 2019

A flexible piezoelectric energy harvester(f-PEH) that converts tiny mechanical and vibrational energy resources into electric signals without any restraints is drawing attention as a self-powered source to operate flexible electronic systems. In particular, the nanocomposites-based f-PEHs fabricated by a simple and low-cost spin-coating method show a mechanically stable and high output performance compared to only piezoelectric polymers or perovskite thin films. Here, the non-piezoelectric polymer matrix of the nanocomposite-based f-PEH is replaced by a P(VDF-TrFE) piezoelectric polymer to improve the output performance generated from the f-PEH. The piezoelectric hybrid nanocomposite is produced by distributing the perovskite PZT nanoparticles inside the piezoelectric elastomer; subsequently, the piezoelectric hybrid material is spin-coated onto a thin metal substrate to achieve a nanocomposite-based f-PEH. A fabricated energy device after a two-step poling process shows a maximum output voltage of 9.4 V and a current of 160 nA under repeated mechanical bending. Finite element analysis(FEA) simulation results support the experimental results.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.5
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• pp.9-15
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• 2022

Discarded bio-wastes, such as seeds and rinds, cause environmental problems. Multiple studies have recycled bio-wastes as eco-friendly energy sources to solve these problems. This study uses bio-waste to fabricate a mandarin peel powder based triboelectric nanogenerator (MPP-TENG). The MPP-TENG is based on the contact separation mode. It generates an open-circuit voltage and short-circuit current of 156V and 2µA, respectively. In addition, MPP-TENG shows stable operation over continuous 3000s without any deviation in output. Also, the device exhibits maximum power density of 5.3㎼/cm² when connected to a resistance of 100MΩ. In an energy storage capacity test for 1000s, the MPP-TENG stores an energy of 171.6µJ in a 4.7µF capacitor. The MPP-TENG can power 9 blue LEDs and 54 green lettering LEDs. These results confirm that the MPP-TENG can provide a new avenue for eco-friendly energy harvesting device fabrication.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.10
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• pp.777-784
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• 2017

Energy harvesting through a thermoelectric module normally makes use of the temperature gradient in the system's operational environment. Therefore, it is difficult to obtain the desired output power when the system is subjected to an environment in which a low temperature gradient is generated across the module, because the power generation efficiency of the thermoelectric device is not optimized. The utilization of solar energy, which is a form of renewable energy abundant in nature, has mostly been limited to photovoltaic solar cells and solar thermal energy generation. However, photovoltaic power generation is capable of utilizing only a narrow wavelength band from the sunlight and, thus, the power generation efficiency might be lowered by light scattering. In the case of solar thermal energy generation, the system usually requires large-scale facilities. In this study, a simple and small size thermoelectric power generation system with a solar concentrator was designed to create a large temperature gradient for enhanced performance. A solar tracking system was used to concentrate the solar thermal energy during the experiments and a liquid circulating chiller was installed to maintain a large temperature gradient in order to avoid heat transfer to the bottom of the thermoelectric module. Then, the setup was tested through a series of experiments and the performance of the system was analyzed for the purpose of evaluating its feasibility and validity.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.11
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• pp.831-835
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• 2013

In this study, we fabricated a micro $Pb(Zr,Ti)O_3$ (PZT) film piezoelectric cantilever with a Si proof mass and dual beams through MEMS process. The size of the beam and the integrated Si proof mass were about $4,320{\mu}m{\times}290{\mu}m{\times}12{\mu}m$ and $1,380{\mu}m{\times}880{\mu}m{\times}450{\mu}m$ each. To reduce the air damping and have the larger displacement of dual beams was used for design. After mounting micro PZT film piezoelectric cantilever on shaker, we measured the resonance frequency and a output voltage while making resonant frequency changed. The resonant frequency and the highest average power of the cantilever device were 110.2 Hz and 0.36 ${\mu}W$ each, at 0.8 g acceleration and 23.7 $k{\Omega}$ load resistance, respectively.

• Journal of Sensor Science and Technology
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• v.31 no.6
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• pp.376-382
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• 2022

A triboelectric nanogenerator (TENG) can obtain electrical output due to the reciprocal motion between two objects (i.e., rubbing), in which repetitive contact is made. High reliability, stable output, and high reproducibility are important aspects of the electrical output obtained through a TENG as a sensor or generator, thus enabling its meaningful use. Therefore, many researchers fabricated TENGs into individual parts in the form of one module type to obtain high reproducibility and reliability. Since a TENG manufactured as a module type operates as a single device, it is possible to collect kinetic energy and convert it into electrical energy through the interaction between internally configured elements without the need for a separate structure. In addition, it is relatively easy to apply the size to the body, machine tools, and natural environment by simply adjusting the size suitable for use and surrounding environmental conditions. In this paper, the application cases of module-type TENGs are divided into four areas, and the research progress of module-type TENGs in each area is extensively reviewed.

• Science of Emotion and Sensibility
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• v.26 no.2
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• pp.129-140
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• 2023

Following ISO 20471, in this study, first, two sets of safety clothes and safety vests were made by designing and attaching animal and bird patterns preferred by children to retroreflective films and black fabrics on those fluorescent fabrics and retroreflective materials prescribed by international standards. Second, by mounting a smart photonic device on the safety clothing so that the body can be recognized from a distance even without an ambient light source at night, children can emit three types of light depending on the situation with just one-touch of the button. From a result of comparison with visibility a day and night by dressing a mannequin in the made smart safety clothing, the difference in visibility was evident at night, it was confirmed that we can see the figure of a person even at a distance of approximately 70 m. Therefore, it is expected to contribute to the prevention of traffic and other accidents on the road, as the drivers driving at night or in bad weather can recognize a person from a distance. Third, in case of the energy is exhausted and cannot maintain the stability of the light-emitting function of the optical faber, we can use energy harvesting device, and the light-emitting time will be extended. As a result it comes up to emit light stably for a long time. And this prove that smart photonic safety clothing can also be used for night workers. Therefore, optical fiber safety clothing is expected to be highly wearable not only in real life but also in dark industrial sites due to stable charging by applying the energy harvesting provided by solar cells.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.565-568
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• 2014

This paper presents a 0.2V DC/DC boost converter with regulated output for thermoelectric energy harvesting. To use low voltages from a thermoelectric device, a start-up circuit consisting of native NMOS transistors and resistors boosts an internal VDD, and the boosted VDD is used to operate the internal control block. When the VDD reaches a predefined value, a detector circuit makes the start-up block turn off to minimize current consumption. The final boosted VSTO is achieved by alternately operating the sub-boost converter for VDD and the main boost converter for VSTO according to the comparator outputs. When the VSTO reaches 2.4V, a buck converter starts to operate to generate a stabilized output VOUT. Simulation results shows that the designed converter generates a regulated 1.8V output from an input voltage of 0.2V, and its maximum power efficiency is 60%. The chip designed using a $0.35{\mu}m$ CMOS process occupies $1.1mm{\times}1.0mm$ including pads.

• Carbon letters
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• v.21
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• pp.8-15
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• 2017

The thermoelectric Seebeck and Peltier effects of a single walled carbon nanotube (SWCNT) quantum dot nanodevice are investigated, taking into consideration a certain value of applied tensile strain and induced ac-field with frequency in the terahertz (THz) range. This device is modeled as a SWCNT quantum dot connected to metallic leads. These two metallic leads operate as a source and a drain. In this three-terminal device, the conducting substance is the gate electrode. Another metallic gate is used to govern the electrostatics and the switching of the carbon nanotube channel. The substances at the carbon nanotube quantum dot/metal contact are controlled by the back gate. Results show that both the Seebeck and Peltier coefficients have random oscillation as a function of gate voltage in the Coulomb blockade regime for all types of SWCNT quantum dots. Also, the values of both the Seebeck and Peltier coefficients are enhanced, mainly due to the induced tensile strain. Results show that the three types of SWCNT quantum dot are good thermoelectric nanodevices for energy harvesting (Seebeck effect) and good coolers for nanoelectronic devices (Peltier effect).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.7
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• pp.525-530
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• 2012

We present the results of a study of the polarizing photovoltaic (PV) effects in an aligned polymer bulk heterojuction PV layer. The fairly uniform in-plane uniaxial alignment of the PV layer with a macroscopic axial orientational order parameter of 0.40 was achieved by means of a simple rubbing technique. Moreover, reflective polarizing PSCs having the aligned PV layers were applied to power-generating reflective type liquid crystal displays (LCDs), which exhibited a maximum contrast ratio of 1.7. These results form a promising foundation for various energy harvesting polarization dependent opto-electrical LCD device applications.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.12
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• pp.955-960
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• 2012

We fabricated piezoelectric unimorph cantilever generators (UCG) using $Pb(Zr_{0.54}Ti_{0.46})O_3$ + 0.2 wt% $Cr_2O_3$ + 1.0 wt% $Nb_2O_5$ (PZCN) piezoelectric thick films, which were produced by a tape casting method. The PZCN thick films were tailored with same width and thickness but different lengths from 7.7 to 57.7 mm in order to evaluate optimized UCG for energy harvesting device applications. When the length of PZCN film was increased, the resonance frequency of UCG was slightly increased from 7 Hz to 8 Hz, which could be due to enlarged area of the highly stiff piezo-ceramic film. However, the output power was proportionally increased with the length of PZCT film and it reached 4.68 mW (1.221 $mW/cm^3$) when the film's length was 57.7 mm under 25 g of tip mass at 8 Hz, which is sufficient for micro-scale device applications.