• Archives of Plastic Surgery
• /
• v.46 no.5
• /
• pp.399-404
• /
• 2019

Background The objectives of this study were to design polycaprolactone nanofibers with a radial pattern using a modified electrospinning method and to evaluate the effect of radial nanofiber deposition on mechanical and biological properties compared to non-patterned samples. Methods Radially patterned polycaprolactone nanofibers were prepared with a modified electrospinning method and compared with randomly deposited nanofibers. The surface morphology of samples was observed under scanning electron microscopy (SEM). The tensile properties of nanofibrous mats were measured using a tabletop uniaxial testing machine. Fluorescence-stained human bone marrow stem cells were placed along the perimeter of the radially patterned and randomly deposited. Their migration toward the center was observed on days 1, 4, and 7, and quantitatively measured using ImageJ software. Results Overall, there were no statistically significant differences in mechanical properties between the two types of polycaprolactone nanofibrous mats. SEM images of the obtained samples suggested that the directionality of the nanofibers was toward the central area, regardless of where the nanofibers were located throughout the entire sample. Florescence images showed stronger fluorescence inside the circle in radially aligned nanofibers, with significant differences on days 4 and 7, indicating that migration was quicker along radially aligned nanofibers than along randomly deposited nanofibers. Conclusions In this study, we successfully used modified electrospinning to fabricate radially aligned nanofibers with similar mechanical properties to those of conventional randomly aligned nanofibers. In addition, we observed faster migration along radially aligned nanofibers than along randomly deposited nanofibers. Collectively, the radially aligned nanofibers may have the potential for tissue regeneration in combination with stem cells.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2009.06a
• /
• pp.347-348
• /
• 2009

• Polymer(Korea)
• /
• v.34 no.3
• /
• pp.185-190
• /
• 2010

Recently, an electrospinning process, which is one of various nanotechnologies, has been used in fabricating micro/nanosized fibers. The fabricated electrospun micro/nanofibers has been widely applied in biomedical applications, specially in tissue regeneration. In this study, we fabricated highly aligned electrospun biodegradable and biocompatible poly(${\varepsilon}$-caprolactone)(PCL) micro/nanofibers by using a modified electrospinning process supplemented with a complex electric field. From this process, we can attain highly aligned electrospun nanofibers compared to that fabricated with the normal electrospinning process. To observe the feasibility of the highly aligned electrospun mat as a biomedical scaffold, nerve cells(PC-12) was cultured and it was found that the cells those were well oriented to the direction of aligned fibers.

• Proceedings of the Polymer Society of Korea Conference
• /
• 2006.10a
• /
• pp.299-299
• /
• 2006

Polydioxanone nanofibers for TEM observation can be produced. To collect parallelly aligned nanofibers can crystallize them partially. The SAED pattern of nanofibers drawn and/or heat-treated shows a well-developed fiber pattern, and in the patterns we can observe crystalline reflections up to third layer line.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2010.11a
• /
• pp.61-62
• /
• 2010

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.17 no.1
• /
• pp.30-34
• /
• 2007

[ $TiO_2/PVP$ ] nanofibers were electrospun by varying the collector grounding design to improve the axial alignment of fibers. The collectors are composed of two pieces of conductive substrates separated by a gap f3r the uniaxial alignment of fibers (X design). The collectors consisting of two sets of substrates placed by $90^{\circ}$ (XY design) equipped with a timer are also prepared for biaxial alignment of fibers. Both collectors show that the charged nanofibers are stretched to span across the gap between the electrodes. Experimental results reveal that the latter collector is more effective on the directionality of electrospun $TiO_2/PVP$ nanofibers due to the dissipation of accumulated electric charge between the collectors.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.06a
• /
• pp.680-685
• /
• 2005

Multi-walled carbon nanotubes were purified by using the nitric acid after the mechanical cutting, which carboxylic group might be introduced into the surface of nanotubes. To enhance the dispersion of CNTs, carboxylic groups were substituted in the reaction with octadecyl amine containing a long alkyl group. Nanofibers were manufactured by electrospinning, the solution that mixed with PMMA and ODA-fuctionalized CNTs in dimethyl formamide and dispersed with ultrasonication. Diameter and alignment of nanofibers with various electrospinning parameters, such as the CNT and PMMA concentration in solution, the applied voltage, and the distance to the collector were investigated. As a result, the nanofiber diameter was increased with the increment of PMMA concentration, whereas it was reduced as the applied voltage and the spinning distance was increased. The spinning area became smaller with the distance. The nanofibers were formed without the defect on surface and well aligned in a specific concentration of PMMA and nanotubes.

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

• Composites Research
• /
• v.26 no.3
• /
• pp.160-164
• /
• 2013

In this study, the effect of phosphoric acid (PA) as a fiber spinning aid on the strength increase of polyacrylonitrile (PAN) nano-fibers by using modified mechano-electrospinning technologies has been analyzed. The medium carbonization temperature of $800^{\circ}C$ has been selected for the future economic production of these new materials. The concentration of PAN in dimethyl sulfoxide (DMSO) was fixed as 5 wt%. The weight fraction of PA was selected as being 2%, 4%, 6%, and 8% in comparison to PAN. These solutions have been used to make the nanofibers. The mechano-electrospinning apparatus installed in KRICT was made by our own design. By using this apparatus the continous and highly aligned precursor nano-fibers have been obtained. The bundle of 50 well aligned nano diameter continuous fibers with the diametr of 10 microns with 6 wt% phosphoric acid for addition showed maximum mechanical properties of 1.6 GPa as tensile strength and 300 GPa as Young's modulus. The weight of final product can be increased 19%, which can improve the economical benefits for the application of these new materials.

• Journal of the Korean Society for Precision Engineering
• /
• v.33 no.3
• /
• pp.225-230
• /
• 2016

Since the development of anodic aluminum oxide (AAO), extensive studies have been conducted ranging from fundamental research to the applications of AAO. Most of the research on AAO structures have focused on well-aligned nanoporous structures fabricated under specific conditions. This study investigated fabricable AAO structures with anodization performed with various temperatures, electrical potentials, and basal plane surfaces. As a result, nanoporous and nanofibrous structures were fabricated. The nanopores were formed at a relatively lower temperature and potential, and the nanofibers were formed at a relatively higher temperature and potential regardless of the basal plane surface. The shape of the base surface was found to influence the structural arrangement in nanoporous morphologies. These interesting findings relating to new morphologies have the potential to broaden the possible applications of AAO materials.