• Composites Research
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• v.15 no.2
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• pp.11-17
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• 2002

The piezoelectric thin film sensor can be used to interpret variations in structural and material properties, e.g. for structural integrity monitoring and assessment. To illustrate one of this potential benefit, PVDF (polyvinylidene fluoride) film sensors are used for monitoring impact damage in Gr/Ep composite panels. Both PVDF film sensors and strain gages are attached to the surface of Gr/Ep specimens. A series of impact tests at various impact energy by changing impact mass the height are performed on the instrumented drop weight impact tester. The sensor responses are carefully examined to predict the onset of impact damage such as indentation, matrix cracking, and delamination, etc. Test results show that the particular waveforms of sensor signals implying the damage initiation and development are detected above the damage initiation impact energy. As expected, the PVDF film sensor is found to be more sensitive to impact damage initiation event than the strain gage.

• Macromolecular Research
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• v.11 no.1
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• pp.9-13
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• 2003

Poly (vinylidene fluoride) (PVDF) samples were implanted by using high energy (MeV)F$^{2+}$ and Cl$^{2+}$ ions. We observed that AC dielectric constant of the ion-implanted PVDF samples decreased from 10.5 to 2.5 at 1 kHz as the ion dosage increased from 10$^{11}$ to 3 $\times$ 10$^{14}$ ions/$\textrm{cm}^2$. From differential scanning calorimetry experiments, we observed that PVDF samples become more disordered state through the ion implantation. The decrease of the number of bonding of C-H and C-F and the increase of unsaturated bonding were observed from X-ray photoelectron spectroscopy experiments. The emission of HF and H$_2$ molecules during the ion implantation was detected by residual gas analyzer spectrum. Based upon the results, we analyzed that the low AC dielectric constant of the MeV ion-implanted PVDF samples originated from the reduction of polarization due to the structural change of the CF$_2$ molecules in the MeV ion-implanted PVDF samples.les.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.1
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• pp.153-159
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• 2019

Respiration is one of the important vital signs to determine the condition of the patient. Especially during deep sedation, since the patient's apnea and hypopnea are difficult to detect without continuous monitoring, there is a need for a continuous respiration monitoring method that can accurately and simply determine the patient's respiratory condition. Currently, respiration monitoring methods using various devices have been developed, but these methods have not only late response time but also low reliability at the clinical stage. In this study, attachable sensor using PVDF(polyvinylidene fluoride) film and a monitoring device which could detect abnormal symptoms of breathing in early stage during deep sedation. The results of this study can be used in various medical fields including not only in the area of remote monitoring for respiration related sleep monitoring but also in routine monitoring during deep sedation.

• Proceedings of the Korean Vacuum Society Conference
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• 1994.06a
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• pp.53-53
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• 1994

• Composites Research
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• v.25 no.3
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• pp.70-75
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• 2012

Interfacial durability and electrical properties of CNT, ITO or xGnP coated PVDF nanocomposites were investigated for acoustic actuator applications. The xGnP coated PVDF nanocomposite exhibited better electrical conductivity than CNT and ITO case due to the unique electrical property of xGnP, and this nanocomposite also showed good sound characteristics. Interfacial adhesion durability between either neat CNT or plasma treated CNT and plasma treated PVDF were measured by static contact angle, surface energy, work of adhesion, and spreading coefficient tests. The optimum acoustic actuation performance of xGnP coated PVDF nanocomposite was measured using sound level meter with changing radius of curvature and coating conditions. As compared to CNT and ITO, the xGnP was known as more appropriate acoustic actuator due to the characteristic electrical property. It is the most appropriate condition when the radius of curvature is 15 degree. Although sound characteristics were different with various coating thicknesses, it is possible to manufacture transparent actuator with good sound quality.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.228-231
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• 2000

The active vibration control of laminated composite shell has been performed with the optimized sensor/actuator system. PVDF film is used fur the material of sensor/actuator. Finite element method is utilized to model the whole structure including the piezoelectric sensor/actuator system, The distributed selective modal sensor/actuator system is established to prevent the adverse effect of spillover. In the finite element discretization process, the nine-node shell element with five nodal degrees of freedoms is used. Electrode patterns and lamination angles of sensor/actuator are optimized using genetic algorithm. Sensor is designed to minimize the observation spillover, and actuator is designed to minimize the system energy of the control modes under a given initial condition. Modal sensor/actuator profiles are optimized for the first and the second modes suppression of singly curved cantilevered composite shell structure. Discrete LQG method is used as a control law. The real time vibration control with profile optimized sensor/actuator system has been performed. Experimental result shows successful performance of the integrated structure for the active vibration control.

• Elastomers and Composites
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• v.50 no.4
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• pp.292-296
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• 2015

Biomimetic artificial basilar membrane being a core part of artificial cochlear requires performance evaluation through aging test. To evaluate the aging properties of PVDF piezoelectric membrane used for artificial basilar membrane, its mechanical properties such as tensile strength and elastic modulus and piezoelectric property such as piezoelectric constant were measured. The aging test conditions and acceleration constants were calculated based on Arrhenius model. The changes in tensile strengths and elastic moduli measured were less than 10~20% after aging test equivalent for 10 years. The piezoelectric constants were decreased drastically to 80% of its initial value in the early stage of the aging test and expected to decrease slowly down to 65% over 10 years. The experimental results show the reliability of totally implantable novel artificial cochlear and will contribute its commercialization.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.512-513
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• 2007

Carbon/polymer based composite electrodes were fabricated by using Super p. Black(SPB) as a conductor and polyvinylidene fluoride (PVDF) as a binder. This type of composite electrode are considered as excellent candidates for heating film and variable resistor applications. Aim of this work is the study of the Mechanical and Electrical properties on composite electrode by the contents of SPB and MWCNT, respectively. The composite electrode having 10~15 wt% of SPB show good electrical and mechanical properties. Mechanical and electrical properties are increased by the addition of MWCNT into the composite electrode.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.2
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• pp.51-56
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• 2003

The piezoelectric thin film(PVDF: polyvinylidene fluoride) sensors having good dynamic sensing charachteristics can be used to monitor low vwlocit impact on composite structures. The impact response function for composite sandwich beam was derved. The impact tests at low energy without inducing damage were performed on the instrumented drop weight impact tester. The measured signals of PVDF sensors attached on the surface of the beam agreed well with the simulated signals. And the inverse technique was applied to reconstruct the impact forces from the PVDF sensor signals. Most of reconstructed impact forces showed good agreement with the measured forces. The comparison results showed that the piezoelectric thin film sensor can be used to monitor the low velocity impact on composite sandwich structures.

• Journal of Biomedical Engineering Research
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• v.35 no.5
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• pp.169-176
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• 2014

As body postures on bed affects various sleep related diseases, it is considered as important information when monitoring sleeping in daily life. Though there have already been a few approaches to monitor body postures on bed conventionally, the development for simple and unconstrained methods is still needed to realize the long-term daily monitoring. Focusing on the fact that ballistocardiogram changes depending on the body postures on bed, we developed a novel method to estimate body posturesusing extremely simple, film-type ballistocardiogram sensor which is based on polyvinylidene fluoride(PVDF) film. With 10 subjects, we performed two experiments. One was for an estimation test to show that body postures on bed can be estimated by ballistocardiogram, and the other was for a reproducibility test to present the feasibility of ballistocardiogram based body postures monitoring. To estimate body postures on bed, we made an individual template set of body postures by designating one ballistocardiogram (BCG) sample as a template in each postures. Then, we calculated Pearson's correlation coefficients between a sample and each templates and estimated the body posture of the sample by choosing a posture which corresponds to the most significant correlation coefficients. As a result, we estimated body postures on bed with 99.2% accuracy in average and found that the estimation using ballistocardiogram is reproducible.