Publications by authors named "Ji Sun Yun"

The exposure of workers to propylene glycol monomethyl ether acetate (PGMEA) in manufacturing environments can result in potential health risks. Therefore, systems for PGMEA removal are required for indoor air quality control. In this study, core-shell zeolite socony mobil-5 (ZSM-5)/polyvinylpyrrolidone-polyvinylidene fluoride nanofibers were directly electrospun and partially wet-etched on a mesh substrate to develop a cover-free compact PGMEA air filter.

View Article and Find Full Text PDF

Multifunctional nanofibers for particulate matter (PM) and volatile organic compounds (VOCs) removal from the indoor atmospheric environment were manufactured from eco-friendly natural cellulose materials via electrospinning using an optimized solvent system containing 1-ethyl-3-methylimidazolium acetate (EmimAC) and dimethylformide (DMF) in a 3:7 volume ratio. EmimAC improved the cellulose stability, whereas DMF improved the electrospinnability of the material. Various cellulose nanofibers were manufactured using this mixed solvent system and characterized according to the cellulose type, such as hardwood pulp, softwood pulp, and cellulose powder, and cellulose content ranging from 6.

View Article and Find Full Text PDF

Ceramics are high-strength and high-temperature resistant materials that are used in various functional parts. However, due to the high strength and brittleness properties, there are many difficulties in the fabrication of complex shapes. Therefore, there are many studies related to the fabrication of ceramic parts using 3D printing technology optimized for complex shapes.

View Article and Find Full Text PDF

Highly porous-cellulose-acetate (CA) nanofibers were prepared by an electrospinning process based on a nonsolvent-induced phase separation (NIPS) mechanism, and their PM capture efficiencies were evaluated. The NIPS condition during the electrospinning process was achieved by selecting appropriate good and poor solvents based on the Hansen solubility parameters of CA. ,-dimethylacetamide (DMAc) was used as the good solvent, while dichloromethane (DCM), tetrahydrofuran (THF), and acetone were used as poor solvents.

View Article and Find Full Text PDF

A 3YSZ (3 mol% yttria-stabilized zirconia) ceramic green body with 50 vol% of ceramic content was 3D-printed by supportless stereolithography under optimal drying, debinding, and sintering conditions in order to achieve high strength and density. The viscosity and flowability of the ceramic nanocomposite resins were optimized by adjusting the amounts of non-reactive diluents. The ceramic 3D-printed objects have a high polymer content compared to ceramics samples manufactured by conventional manufacturing processes, and the attraction between layers is weak because of the layer-by-layer additive method.

View Article and Find Full Text PDF

An all-in-one energy harvester module comprising a top piezoelectric layer, a bottom piezoelectric layer, and a middle triboelectric layer was fabricated based on flexible piezoceramic nanofibers to serve as a power source for wearable devices. The top and bottom piezoelectric layers were manufactured by modularizing electrospun piezoceramic nanofibers with an interdigitated electrode, and the energy harvesting characteristics were maximized by laminating the single modules in -axis array arrangements. The triboelectric layer was manufactured by attaching polydimethylsiloxane on both sides of an electrode layer, and the energy harvesting characteristics were controlled according to the surface roughness of the triboelectric modules.

View Article and Find Full Text PDF

In an effort to fabricate a wearable piezoelectric energy harvester based on core-shell piezoelectric yarns with external electrodes, flexible piezoelectric nanofibers of BNT-ST (0.78BiNaTiO₃-0.22SrTiO₃) and polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) were initially electrospun.

View Article and Find Full Text PDF

Flexible lead-free piezoelectric nanofibers, based on BNT-ST (0.78BiNaTiO₃-0.22SrTiO₃) ceramic and poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) copolymers, were fabricated by an electrospinning method and the effects of the degree of alignment in the nanofibers on the piezoelectric characteristics were investigated.

View Article and Find Full Text PDF

Silane coupling agents (SCAs) with different organofunctional groups were coated on the surfaces of Al₂O₃ ceramic particles through hydrolysis and condensation reactions, and the SCA-coated Al₂O₃ ceramic particles were dispersed in a commercial photopolymer based on interpenetrating networks (IPNs). The organofunctional groups that have high radical reactivity and are more effective in UV curing systems are usually functional groups based on acryl, such as acryloxy groups, methacrloxy groups, and acrylamide groups, and these silane coupling agents seem to improve interfacial adhesion and dispersion stability. The coating morphology and the coating thickness distribution of SCA-coated Al₂O₃ ceramic particles according to the different organofunctional groups were observed by FE-TEM.

View Article and Find Full Text PDF

The functionalization of single-walled carbon nanotubes (SWCNTs) by forming self-assembled supramolecular structure of 10,12-pentacosadiynoic acid (PCDA) on the carbon nanotube wall is reported. PCDA assemblies on SWCNTs (PCDA/SWCNTs) were polymerized by UV irradiation to extensively conjugated polydiacetylene (PDA). PDA/SWCNT was identified by absorption and emission spectroscopy, scanning and transmission electron microscopies (SEM and TEM) and atomic force microscopy (AFM).

View Article and Find Full Text PDF
Article Synopsis
  • Developed efficient microvalve systems using an ionic polymer-metal composite (IPMC) diaphragm actuator that operates through applied voltages and lithium ion flux.
  • The IPMC was enhanced with platinum nanoparticles on Nafion film, which improved its actuation performance as confirmed by SEM imaging.
  • Successful flow control in microfluidic channels was demonstrated, indicating the potential for IPMC-based microvalves in various applications.
View Article and Find Full Text PDF

Graphene nanosheet hybridized with polydiacetylene (PDA) can be used as the electrochemical biosensor applications. Self-assembly and photo-polymerization chemistry of diacetylenic monomers on reduced graphene oxide (RGO) for non-covalent functionalization were used for high solubility and further functionality of graphene in water necessary for biosensor application. This enables regular graphene micropatterns to be formed on large substrates with chemical bonding and biological interactions.

View Article and Find Full Text PDF