• Composites Research
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• v.18 no.4
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• pp.21-26
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• 2005

Nondestructive damage sensing and load transfer mechanisms of carbon nanotube (CNT) and nanofiber (CNF)/epoxy composites have been investigated by using electro-micromechanical technique. The electrospun PVDF nanofibers were also prepared as a piezoelectric sensor. The electro-micromechanical techniques were applied to evaluate sensing response of carbon nanocomposites by measuring electrical resistance under an uniform cyclic loading. Composites with higher volume content of CNT showed significantly higher tensile properties than neat and low volume$\%$ CNT composites. CNT composites showed humidity sensing within limited temperature range. CNT composites with smaller aspect ratio showed higher apparent modulus due to high volume content in case of shorter aspect ratio. Thermal treated electrospun PVDF nanofiber showed higher mechanical properties than the untreated case due to crystallinity increase, whereas load sensing decreased in heat treated case. Electrospun PVDF nanofiber web also showed sensing effect on humidity and temperature as well as stress transferring. Nanocomposites and electrospun PVDF nanofiber web can be applicable for sensing application.

• Composites Research
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• v.26 no.1
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• pp.14-20
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• 2013

The electrospun PVDF containing CNT was made for fabricating materials of the actuator. The electrochemical and their actuating movement were evaluated for the actuator performance in the electrochemical environment. The actuator (which was fabricated by electrospinning) had some advantages, i.e., good dispersion and flexible properties. In the electrospinning process, the final product would have different forms based on different essential factors. In this work, electrospun nanofibers were aligned by using the drum-type collector, and the morphology was identified via the field emission-scanning electron microscope (FE-SEM). The uniform dispersion of CNT in PVDF nanofiber was observed by electron probe X-ray micro-analysis (EPMA) test. The results of tensile strength and electrical resistivity provided the aligned state. The electrospun CNT/PVDF nanofiber sheet on the aligned direction showed better mechanical and electrical properties than the case of the vertically-aligned direction. The efficiency and electrical capacities of electrospun CNT/PVDF nanofiber sheets were compared with the cast PVDF sheet for actuator application. Electrospun CNT/PVDF nanofiber sheet exhibited much better the case of actuator performance than cast neat PVDF actuator, due to the excellent electrical connecting areas.

• Proceedings of the Korean Fiber Society Conference
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• 2003.10b
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• pp.271-272
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• 2003

Electrospinning is a novel process for forming fibers with submicron scale diameters through the action of electrical force. In the previous study, we performed study on the ultrafine PVDF nanofiber production in the stable spinning condition. Recently it would be great interest to fabricate IP(inorganic particle) assemblies in nanofibe. since such IP/nanofiber hybrid materials might be used in a nonwoven form as nanowires, medical gauges for bums healing and cell growing, sensors, chemical and gas filteration. (omitted)

• Development and Reproduction
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• v.24 no.2
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• pp.135-147
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• 2020

Polyvinylidene fluoride (PVDF) is a stable and biocompatible material that has been broadly used in biomedical applications. Due to its piezoelectric property, the electrospun nanofiber of PVDF has been used to culture electroactive cells, such as osteocytes and cardiomyocytes. Here, taking advantage of the piezoelectric property of PVDF, we have fabricated a PVDF nanofiber scaffolds using an electrospinning technique for differentiating human embryonic stem cells (hESCs) into neural precursors (NPs). Surface coating with a peptide derived from vitronectin enables hESCs to firmly adhere onto the nanofiber scaffolds and differentiate into NPs under dual-SMAD inhibition. Our nanofiber scaffolds supported the differentiation of hESCs into SOX1-positive NPs more significantly than Matrigel. The NPs generated on the nanofiber scaffolds could give rise to neurons, astrocytes, and oligodendrocyte precursors. Furthermore, comparative transcriptome analysis revealed the variable expressions of 27 genes in the nanofiber scaffold groups, several of which are highly related to the biological processes required for neural differentiation. These results suggest that a PVDF nanofiber scaffold coated with a vitronectin peptide can serve as a highly efficient and defined culture platform for the neural differentiation of hESCs.

• Macromolecular Research
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• v.16 no.3
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• pp.212-217
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• 2008

PVDF ($Kynar^{(R)}$ 761) nanofibers were made by electrospinning with an external voltage of 6-10 kV, a traveling distance of 7-15 cm and a flow rate of 0.4-1 mL/h. Although the mean diameter of the fibers has not changed significantly, the conditions affected the change in diameter distribution. This was attributed to interactions, both attraction and repulsion, between the positive charges on the polymer solutions and the electrically grounded collector. Higher voltages and traveling distance increased the level of attraction between the positive charge on the polymer solution and the electrically grounded collector, resulting in a narrow diameter distribution, In addition, a high flow rate allowed a high population of uniformly charged solutions to travel to the grounded collector, which resulted in a narrow diameter distribution. The optimum conditions for electrospinning of PVDF in DMAc/acetone (3/7 by wt) were a collector voltage of 6 kV, a syringe tip to collector of 7 cm, a flux rate of 0.4 mL/h and 10 kV, 10 cm, 1 mL/h, Since PVDF is widely used as a filtration membrane, it was electrospun on a PET support with a rotating drum as a grounded collector. Surprisingly, some straight nanofibers were separated from the randomly deposited nanofibers. The straight nanofiber area was transparent, while the randomly deposited nanofiber area was opaque. Both straight nanofibers and aligned nanotibers could be obtained by manipulating the PET drum collector. These phenomena were not observed when the support was changed to an Al sheet. This suggests that a pseudo dual collector was generated on the PET sheet. No negative charge was created because the PET sheet was not a conductive material. However, less charge was created when the sheet was not perfectly attached to the metal drum. Hence, the nanotibers jumped from one grounded site to the nearest one, yielding a straight nanofiber.

• Journal of Industrial and Engineering Chemistry
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• v.68
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• pp.416-424
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• 2018

Oil spill and oily wastewater have now become a serious threat to the freshwater and marine environments. Porous materials with super-hydrophobicity and super-oleophilicity are good candidates for the oil adsorption and oil/water separation. Here, flexible hybrid nanofibrous membrane (FHNM) containing $SiO_2$/polyvinylidene fluoride (PVDF) microspheres was prepared by simultaneous electrospinning and electrospraying. The obtained FHNM combined the flexibility of the nanofiber mat and super-hydrophobicity of the microspheres, which could not be achieved by either only electrospinning or only electrospraying. It was found that when the weight ratio between the $SiO_2$ and PVDF reached a critical value, the $SiO_2$ nanoparticles were present on the PVDF microsphere surface, significantly improving the surface roughness and hence the contact angle of the FHNM. Compared with the pure electrospun PVDF nanofiber mat, most of the FHNMs have a higher oil adsorption capacity. The FHNM could separate the oil with water quickly under the gravity and displayed a high efficiency and good reusability for the oil/water separation. More importantly, the FHNM could not only separate the oil with the pure water but also the corrosive solution including the salt, acid and alkali solution.