• 대한전기학회논문지
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• 제37권3호
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• pp.163-170
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• 1988

In order to investigate the mechanism of pyroelectricity on polyvinylidene fluoride film, the observations were carried out on the characteristics of infrared spectra, thermally stimulated current and pyroelectric current. As the results obtained from the study, it was concluded that the origin for thermally stimulated current exhibited above room temperature can be attributed to hole injected from anode during poling process. Futhermore it is clarified also that the origin of pyroelectricity observed on the specimen concerned is to spontaneous polarization of CF dipole attached to molecular chain segment, however, the fraction of spontaneous polarization is largely influenced by the amount of hole injected from anode.

• 센서학회지
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• 제28권6호
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• pp.366-370
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• 2019

In this study, we have successfully fabricated a highly conductive transparent electrode using Ag nanowires, based on piezoelectric polyvinylidene difluoride (PVDF) film, that can be applied as transparent and flexible speakers. The structural morphology of the Ag nanowires was confirmed by a detailed scanning electron microscopy. Ultraviolet-visible spectroscopy demonstrated that the transparent electrode fabricated by the Ag nanowires exhibited a transmittance of above 70%. The transparent electrode also showed very low sheet resistance with high flexibility. We have further developed an anti-oxidation coating layer by using a tetraethyl orthosilicate-poly trimethyloxyphenylsilane (TEOS-PTMS) slurry technique. It was confirmed that the transmittance and sheet resistance of the antioxidant film depends critically on the humidity of the film surface. We believe such Ag nanowire electrodes are a very promising next-generation transparent electrode technology that can be used in future flexible and transparent devices.

• 대한의용생체공학회:의공학회지
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• 제35권3호
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• pp.55-61
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• 2014

In sleep monitoring system, polysomnography (PSG) is the gold-standard but previous studies revealed that attaching numerous amount of sensors disturb sleep during the test which is the fundamental disadvantage of PSG. We suggest an unconstrained rapid-eye-movement (REM) sleep monitoring method measured with polyvinylidene (PVDF) film-based sensor for the normal and the obstructive sleep apnea (OSA) patients. Nine normal subjects and seventeen OSA patients have participated in the study. During REM sleep, rate and variability of respiration are known to be greater than in other sleep stages. Based on this phenomena, respiratory signals of participants were unconstrainedly measured using the PVDF-based sensor with the PSG and REM sleep were extracted from the average rate and variability of respiration. In epoch-by-epoch REM sleep detection, proposed method classified REM sleep with an average sensitivity of 72.3%, specificity of 92.5%, accuracy of 88.9%, and kappa statistic of 0.60 compared to the results of PSG. Student's t-test showed no significant difference between the results of normal and OSA group. This method is potentially applicable to REM sleep detection in homing environment or ambulatory monitoring.

• 한국진공학회지
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• 제6권2호
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• pp.122-128
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• 1997

본 연구는 건식 프로세스의 일종인 열증착법을 이용하여 PVDF유기박막을 제조하는 데 있다. 발열원과 기판간의 거리는 5cm로 하였고, 기판의 온도를 $30^{\circ}C$로 유지시키면서 반 응조의 진공도가 $2.0\times10^{-5}$Torr로 되었을 때 발열원의 온도를 6~$8^{\circ}C$/min로 상승시켜, 발열 원의 온도가 $270^{\circ}C$될 때 셔터(shutter)를 열고 증착을 개시하였다. 전계인가 강도의 증가에 따라 $\alpha$형 피크들인 $530\textrm{cm}^{-1},795\textrm{cm}^{-1},1182\textrm{cm}^{-1}$ 피크는 점점 작아지고 $\beta$형 피크 인 $510\textrm{cm}^{-1},1273\textrm{cm}^{-1}$ 피크가 증가함을 알 수 있었다. 전계인가강도 71.4kV/cm 이하에서는 $530\textrm{cm}^{-1}$ 피크가 $510\textrm{cm}^{-1}$피크의 강도보다 큰 것을 알 수 있는데 이는 $\beta$형 성분보다 $\alpha$형 성분이 필름의 특성을 지배함을 알 수 있었다. 이상의 결과로 전계인가 강도의 증가에 따라 PVDF 유기박막의 분자쇄는 $\alpha$형인 TGT 또는 TG'T에서 $\beta$형인 평면지그재그 TT형태로 변화함을 알 수 있다.

• E2M - 전기 전자와 첨단 소재
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• 제5권3호
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• pp.295-301
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• 1992

본 연구는 고분자 압전 재료인 PVDF 필름을 시료로 사용하고 분극 조건을 변화시켜 가며 분극화 시킨후 압전계수를 측정하였다. 또한 X-선 회절 장치와 DSC 장치를 이용하여 결정구조 변화를 조사하였으며 또한 분극에 의해 생성된 결정의 용융특성도 관찰하였다. 분극되지 않은 시료의 용융 온도는 약 175.deg.C 부근에서 나타났으나 분극된 시료는 분극 전압이 증가함에 따라 184.deg.C부근에서 새로운 용융점이 나타나기 시작하였으며 분극 전압이 증가할수록 새로운 용융점이 점차 뚜렷해졌다.

• E2M - 전기 전자와 첨단 소재
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• 제5권2호
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• pp.166-174
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• 1992

본 논문에서는 열자격 전류 기법을 이용하여 폴리비닐덴 후로라이드필름에 대한 하전 입자의 거동 상황을 살펴보았는데 결과로 .betha.2, .betha.1, .alpha. 그리고 .alpha.'의 4개의 피크가 -35[.deg.C], -10[.deg.C], 60[.deg.C], 그리고 85[.deg.C]부근의 온도에서 관측되었다. 처음 .betha.2 피크와 .betha.1 피크에서의 온도는 항상 일정하였고 .alpha. 피크와 .alpha.'피크는 형성온도에 의존하였다. .betha.2 피크와 .betha.1 피크의 기원은 쌍극자의 기여로 .alpha. 피크는 결정질 영역의 얕게 트랩된 하전 입자의 탈트랩으로 그리고 .alpha.'피크는 형성온도에 따라 발생되는 Langmurian Model과 Henry Model에 의하여 나타났다. 이러한 해석을 위해 분리된 단일 완화곡선에 점근해법에 의한 수치해석 기법을 적용함으로서 사용시료의 제정수에 대한 계산을 보다 정확하게 구할수 있었으며 특히 적분항에 대한 계산오차가 감소함을 확인하였다.

• 소음진동
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• 제5권3호
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• pp.313-325
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• 1995

Two active/passive vibration dampers were designed to control a cantilever beam first mode of vibration. The active element was a piezoelectric polymer, polyvinlidene fluoride (PVDF). The passive damping was provided by the application of a viscoelastic layer on the surface of the steel beam. Two substantially different damper configurations were designed and tested. One damper consisted of a piezoelectric actuator bonded to one face of the beam, with a viscoelastic layer applied to the other surface of the beam. The second one was composed of a layer viscoeastic layer with one surface bonded to the beam, and with other being constrained by nine piezoelectric actuators connected in parallel. A control law based on the sign of the angular velocity of the cantilever beam was implemented to control the beam first mode of vibration. The piezoelectric sensor output was digitally differentiated to obtain the transverse linear velocity, and its sign was used in the control algorith. Two dampers provided the system a damping increase of a factor of four for the first damper and three for the second damper. Both dampers were found to work well at low levels of vibration, suggesting that they can be used effectively to prevent resonant vibrations in flexible structure from initiating and building up.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.1073-1078
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• 2003

This paper presents the vibration characteristics of a cantilever beam in contact with a fluid using a PZT actuator and PVDF film. dynamic behaviors of a flexible beam-water interaction system are examined. The effect of the liquid level on free vibration of the composite beam in a partially liquid-filled circular cylinder is investigated. The coupled system is subject to an undisturbed boundary condition un the fluid domain. In the vibration analysis of a wetted beam. the decoupled analyses between beam and fluid have been conventionally employed by considering first the composite beam vibration in the all and secondly Performing the correction taking account for surrounding fluid effects. That is, this investigation was to look at how natural frequencies, mode shapes. and damping are affected by liquid level variations. The signals from the sensor according to the applied input voltage are digitalized and filtered in order to obtain the dynamic characteristics of the composite beam in contact with fluid. It was found that the coupled natural frequencies decreased with the fluid level for the identical composite beam due to added mass effect. In case of the free-free boundary condition, the natural frequency gently decreased at fluid water level between 20% and 80% in the first tending mode and we found out the bends of stair shape for added mass effect of the fluid.

• 센서학회지
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• 제20권2호
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• pp.114-117
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• 2011

A thick 25 ${\mu}m$ thickness poled P(VDF/TrFE) film pyroelectric infrared ray sensor has been fabricated and then thin 1.6 ${\mu}m$ thickness P(VDF/TrFE) film pyroelectric infrared ray sensor has been fabricated also. These thick and thin P(VDF/TrFE) film pyroelectric infrared ray sensor was mounted in TO-5 housing to detect infrared light of 5.5 ~ 14 ${\mu}m$ wavelength for human body detecting with each other. The noise output voltage of the thick P(VDF/TrFE) film pyroelectric infrared ray sensor were 380 mV and NEP(noise equivalent power) is $3.95{\times}10^{-7}$ W which is the similar value with the commercial pyroelectric infrared ray sensor using ceramic materials as a sensing material. The NEP and specific detectivity $D^*$ of the thin P(VDF/TrFE) film pyroelectric infrared ray sensor were $2.13{\times}10^{-8}$ W and $9.37{\times}106$ cm/W under emission energy of 13 ${\mu}W/cm^2$ respectively. These result caused by lower thermal diffusion coefficient of a thin 1.6 ${\mu}m$ thickness PVDF/TrFE film than the thick 25 ${\mu}m$ thickness poled P(VDF/TrFE) film pyroelectric infrared ray sensor.

• 한국전기전자재료학회논문지
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• 제24권5호
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• pp.422-426
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• 2011

Piezoelectric materials can be used to convert mechanical energy into electrical energy. In this study, we investigated the possibility of harvesting from mechanical vibration force using a high efficient piezoelectric material-polyvinylidene fluoride (PVDF). A piezoelectric energy harvesting system consists of rectifier, filter capacitor, resistance. The experiments were carried out with impacting force to PVDF film with the thickness of 1 ${\mu}m$. The output power was measured with change in the load resistance value from 100 ${\Omega}$ to 2.2 $M{\Omega}$. The highest power was obtained under optimization by selection of suitable resistive load and capacitance. A power of 0.3082 ${\mu}W/mm^2$ was generated at the external vibration force of 5 N (10 Hz) across a 1 $M{\Omega}$ optimal resistor. Also, the maximum power of 0.345 ${\mu}W/mm^2$ was generated at 22 ${\mu}F$ and 1 $M{\Omega}$. The developed system was expected at a solution to overcome the critical problem of making up small size energy harvester.