Yena Kim

Effect of Viscosity on the Morphology of Electrospun Polyacrylonitrile Fibers as a Linear Actuator and Artificial Muscles

Polyacrylonitrile (PAN) nanofibers, which are pH-sensitive and exhibit soft actuation as a linear actuator and artificial muscles, were prepared by electrospinning to investigate the effect of viscosity on the morphology of PAN fibers. Experimental results revealed that higher viscosity is critical for the formation of unbeaded nanofibers because surface tension is almost constant throughout the experiment. Uniform, smooth, and continuous fibers with diameters of about 700 nm were achieved for the 10 wt% PAN fibers at a flow rate of 0.5 mL/h and an electric field of 0.875 kV/cm.

Electrospun Calcium Metaphosphate Nanofibers: I. Fabrication

Calcium metaphosphate (CMP) nanofibers with a diameter of ~600 ㎚ were prepared using electrospun CMP/polyvinylpyrrolidone (PVP) fibers through a process of drying for 5 h in air followed by annealing for 1 h at 650℃ in a vacuum. The viscosity of the CMP/PVP precursor containing 0.15 g/㎖ of PVP was 76 cP. Thermal analysis results revealed that the fibers were crystallized at 569℃. The crystal phase of the as-annealed fiber was determined to be δ-CMP (δ-Ca(PO₃)₂). However, the morphology of the fibers changed from smooth and uniform (as-spun fibers) to linked-particle characteristics with a tubular form, most likely due to the decomposition of the inner PVP matrix. It is expected that this large amount of available surface area has the potential to provide unusually high bioactivity and fast responses in clinical hard tissue applications.

Gas sensing properties of polyacrylonitrile/metal oxide nanofibrous mat prepared by electrospinning

Polyacrylonitrile(PAN)/metal oxide(MO) nanocomposite mats with a thickness of 0.12 mm were electrospun by adding 0 to 10 wt% of MO nanoparticles (, ZnO, , ) into PAN. Pt electrode was patterned on substrate by DC sputtering and then the PAN(/MO) mats on the Pt patterned were electrically wired to investigate the gas sensing properties. As the MO content rose, the fiber diameter decreased due to the presence of lumps caused by the presence of MOs in the fiber. The PAN/2% ZnO mat revealed a faster response time of 93 s and a relatively short recovery of 54 s with a of 0.031 M at a concentration of 200 ppm. The difference in sensitivity was not observed significantly for the PAN/MO fiber mats in the concentration range of 100 to 500 ppm. It can be concluded that an appropriate amount of MO nanoparticles in the PAN backbone leads to improvement of the gas sensing properties.

Electrospun Nanofibrous Polyacrylonitrile(PAN)/ Fe 2 O 3 Membrane as Co 2 Gas Sensor

Polyacrylonitrile (PAN)/Fe₂O₃ nanocomposite membranes with a thickness of 0.02 ㎜ were electrospun by adding 0 to 5 wt% of Fe₂O₃ into PAN. The surface tension, density, kinematic viscosity and dynamic viscosity of the PAN solution were determined to be 33.8±1 mN/m, 0.9794 g/㎖, 1548.6 ㎟/sec and 1516.7 cP, respectively. The average diameters of PAN fibers containing 0, 1, 2, 3, and 4 wt% Fe₂O₃ particles were 300, 260, 210, 130, and 90 nm, respectively. Fourier-transform infrared spectroscopy results showed that the addition of Fe₂O₃ nanoparticles to the PAN mat reduced the absorption peak intensity at 2242 ㎝ -1 (C≡N bond) while it caused a sharp increase in the peak intensity at 2356 ㎝ -1 (C=O bond). Thus, it appears that an appropriate amount of Fe₂O₃ nanoparticles in the PAN backbone leads to an improvement of the performance of the CO₂ gas sensor, most likely due to the change of functional groups in the membrane.