• Journal of Fashion Business
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• v.18 no.5
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• pp.159-170
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• 2014

Recent concerns about the PFOA(perfluorooctanoic acid), have been increasing, which is generally applied in the water-repellent finishing process of textile products. It has been proven through animal testing to be harmful to humans, as possible carcinogens and neuro-toxic material. Thus U. S. Environmental Agency has gone as far as requiring the material to be eliminated in its entirety by 2015. As a viable alternative to this water-repellent finishing agent, the development of C6 product is gaining its popularity. The effects of PFOA finishing on the silk fabrics were examined, and we reviewed parameters of the needed process for optimizing appearance and functionality of silk fabrics treated with eco-friendly water-repellent finishing agent. Cross-linking agent affected the most on black color of reactive ink, among the physical properties. The contact angle reading was the highest in $8g/{\ell}$ of concentration for all fabrics. All the fabric specimens, subjected to the DTP and water repellent finishing, exhibited higher stiffness, where rayon specimen showed the highest, compared to the untreated specimens. The results may provide basic information leading to the development of value-added silk fabrics with water-repellency without excessive deterioration of the delicate appearance and inherent soft touch.

• Journal of Appropriate Technology
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• v.6 no.2
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• pp.226-237
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• 2020

As the number of reported COVID-19 cases rises around the world, regions affected by the virus are taking serious measures to contain its spread. Face shields are one of the highest-need personal protective equipment (PPE) during COVID-19 pandemic. Beyond traditional face masks, as known cases of the coronavirus soar, currently there is a significant shortage of face shields around the world. In response, the protective face shields were designed and fabricated with open-source 3D modelling software and 3D printing technology, respectively. Our face shield consisted of two parts only; a reusable 3D printed headband and a visor made of transparent plastic sheet, as barrier. The resulting 3D printed face shields are affordable, lightweight, one-size-fits-most and ready-to-wear with minimal assemblies, and go on easily over glass, goggle and face mask. To ensure being donated to the healthcare professionals without risk infected by any pathogens, the 3D printed face shields were successfully be disinfected with ultraviolet germicidal irradiation (UVGI dosage of 1000 mJ/cm²) and 70% alcohol. For routine disinfection a UVGI chamber was designed and optimized to provide uniform UV-C illumination with an appreciated fluence for complete decontamination. More than 1,000 face shields were produced already and donated to the special hospitals for COVID-19 patients, quarantines, government and medical agencies in Ethiopia as well as in East-African countries. With certainty, our intention goes beyond the hospitals and other first responders, but not limited for all those who have to stay in the service or be in contact with many other people in the time of COVID-19 pandemic.

• Electronics and Telecommunications Trends
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• v.38 no.6
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• pp.41-51
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• 2023

Heat dissipation technology for semiconductors and electronic packaging has a substantial impact on performance and lifespan, but efficient heat dissipation is currently facing limited improvement. Owing to the high integration density in electronic packaging, heat dissipation components must become thinner and increase their performance. Therefore, heat dissipation materials are being devised considering conductive heat transfer, carbon-based directional thermal conductivity improvements, functional heat dissipation composite materials with added fillers, and liquid-metal thermal interface materials. Additionally, in heat dissipation structure design, 3D printing-based complex heat dissipation fins, packages that expand the heat dissipation area, chip embedded structures that minimize contact thermal resistance, differential scanning calorimetry structures, and through-silicon-via technologies and their replacement technologies are being actively developed. Regarding dry cooling using single-phase and phase-change heat transfer, technologies for improving the vapor chamber performance and structural diversification are being investigated along with the miniaturization of heat pipes and high-performance capillary wicks. Meanwhile, in wet cooling with high heat flux, technologies for designing and manufacturing miniaturized flow paths, heat dissipating materials within flow paths, increasing heat dissipation area, and reducing pressure drops are being developed. We also analyze the development of direct cooling and immersion cooling technologies, which are gradually expanding to achieve near-junction cooling.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.115-116
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• 2012

The demand for flexible electronic systems such as wearable computers, E-paper, and flexible displays has increased due to their advantages of excellent portability, conformal contact with curved surfaces, light weight, and human friendly interfaces over present rigid electronic systems. This seminar introduces three recent progresses that can extend the application of high performance flexible inorganic electronics. The first part of this seminar will introduce a RRAM with a one transistor-one memristor (1T-1M) arrays on flexible substrates. Flexible memory is an essential part of electronics for data processing, storage, and radio frequency (RF) communication and thus a key element to realize such flexible electronic systems. Although several emerging memory technologies, including resistive switching memory, have been proposed, the cell-to-cell interference issue has to be overcome for flexible and high performance nonvolatile memory applications. The cell-to-cell interference between neighbouring memory cells occurs due to leakage current paths through adjacent low resistance state cells and induces not only unnecessary power consumption but also a misreading problem, a fatal obstacle in memory operation. To fabricate a fully functional flexible memory and prevent these unwanted effects, we integrated high performance flexible single crystal silicon transistors with an amorphous titanium oxide (a-TiO2) based memristor to control the logic state of memory. The $8{\times}8$ NOR type 1T-1M RRAM demonstrated the first random access memory operation on flexible substrates by controlling each memory unit cell independently. The second part of the seminar will discuss the flexible GaN LED on LCP substrates for implantable biosensor. Inorganic III-V light emitting diodes (LEDs) have superior characteristics, such as long-term stability, high efficiency, and strong brightness compared to conventional incandescent lamps and OLED. However, due to the brittle property of bulk inorganic semiconductor materials, III-V LED limits its applications in the field of high performance flexible electronics. This seminar introduces the first flexible and implantable GaN LED on plastic substrates that is transferred from bulk GaN on Si substrates. The superb properties of the flexible GaN thin film in terms of its wide band gap and high efficiency enable the dramatic extension of not only consumer electronic applications but also the biosensing scale. The flexible white LEDs are demonstrated for the feasibility of using a white light source for future flexible BLU devices. Finally a water-resist and a biocompatible PTFE-coated flexible LED biosensor can detect PSA at a detection limit of 1 ng/mL. These results show that the nitride-based flexible LED can be used as the future flexible display technology and a type of implantable LED biosensor for a therapy tool. The final part of this seminar will introduce a highly efficient and printable BaTiO3 thin film nanogenerator on plastic substrates. Energy harvesting technologies converting external biomechanical energy sources (such as heart beat, blood flow, muscle stretching and animal movements) into electrical energy is recently a highly demanding issue in the materials science community. Herein, we describe procedure suitable for generating and printing a lead-free microstructured BaTiO3 thin film nanogenerator on plastic substrates to overcome limitations appeared in conventional flexible ferroelectric devices. Flexible BaTiO3 thin film nanogenerator was fabricated and the piezoelectric properties and mechanically stability of ferroelectric devices were characterized. From the results, we demonstrate the highly efficient and stable performance of BaTiO3 thin film nanogenerator.

• Polymer(Korea)
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• v.38 no.6
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• pp.815-819
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• 2014

Scaffolds of tissue engineering should be biocompatible and biodegradable for cell attachment, proliferation and differentiation. In the various scaffold fabrication, 3D printing technique can make the three dimensional scaffold with interconnected pores for cell ingrowth. Polycaprolactone (PCL) is biodegradable polyester with a low melting temperature and has been approved by the Food and Drug Administration (FDA). In this study, PCL scaffold was fabricated by 3D bioprinting system and surface modification of PCL scaffold was controlled by NaOH treatment. Morphological change and wetability of NaOH-treated scaffold were observed by SEM and contact angle measurement system. The remnant of PCL treated with NaOH was measured by ATR-FTIR. In vitro study of scaffolds was evaluated with WST-1 and ALP activity assay. NaOH treatment of PCL scaffolds increased surface roughness, hydrophilicity, cell proliferation and osteogenic differentiation. These results indicate that NaOH-treated PCL scaffold made by 3D bioprinting has tissue engineered potential for the development of biocompatible material.

• Journal of the Korean Vacuum Society
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• v.19 no.2
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• pp.81-90
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• 2010

We introduce a novel and versatile approach for preparing self-assembled nanoporous multilayered films with antireflective properties. Protonated polystyrene-block-poly (4-vinylpyrine) (PS-b-P4VP) and anionic polystyrene-block-poly (acrylic acid) (PS-b-PAA) block copolymer micelles (BCM) were used as building blocks for the layer-by-layer assembly of BCM multilayer films. BCM film growth is governed by electrostatic and hydrogen-bonding interactions between the oppositely BCMs. Both film porosity and film thickness are dependent upon the charge density of the micelles, with the porosity of the film controlled by the solution pH and the molecular weight (Mw) of the constituents. PS7K-b-P4VP28K/PS2K-b-PAA8K films prepared at pH 4 (for PS7K-b-P4VP28K) and pH 6 (for PS2K-b-PAA8K) are highly nanoporous and antireflective. In contrast, PS7K-b-P4VP28K/PS2K-b-PAA8K films assembled at pH 4/4 show a relatively dense surface morphology due to the decreased charge density of PS2K-b-PAA8K. Films formed from BCMs with increased PS block and decreased hydrophilic block (P4VP or PAA) size (e.g., PS36K-b-P4VP12K/PS16K-b-PAA4K at pH 4/4) were also nanoporous. Furthermore, we demonstrate that the nanostructured electrochemical sensors based on patterning methods show the electrochemical activities. Anionic poly(styrene sulfonate) (PSS) layers were selectively and uniformly deposited onto the catalase (CAT)-coated surface using the micro-contact printing method. The pH-induced charge reversal of catalase can provide the selective deposition of consecutive PE multilayers onto patterned PSS layers by causing the electrostatic repulsion between next PE layer and catalase. Based on this patterning method, the hybrid patterned multilayers composed of platinum nanoparticles (PtNP) and catalase were prepared and then their electrochemical properties were investigated from sensing $H_2O_2$ and NO gas. This study was based on the papers reported by our group. (J. Am. Chem. Soc. 128, 9935 (2006); Adv. Mater. 19, 4364 (2007); Electro. Mater. Lett. 3, 163 (2007)).

• Journal of Periodontal and Implant Science
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• v.52 no.4
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• pp.338-350
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• 2022

Purpose: Various studies have investigated 3-dimensional (3D)-printed implants using Ti6Al-4V powder; however, multi-root 3D-printed implants have not been fully investigated. The purpose of this study was to explore the stability of multirooted 3D-printed implants with lattice and solid structures. The secondary outcomes were comparisons between the 2 types of 3D-printed implants in micro-computed tomographic and histological analyses. Methods: Lattice- and solid-type 3D-printed implants for the left and right mandibular third premolars in beagle dogs were fabricated. Four implants in each group were placed immediately following tooth extraction. Implant stability measurement and periapical X-rays were performed every 2 weeks for 12 weeks. Peri-implant bone volume/tissue volume (BV/TV) and bone mineral density (BMD) were measured by micro-computed tomography. Bone-to-implant contact (BIC) and bone area fraction occupancy (BAFO) were measured in histomorphometric analyses. Results: All 4 lattice-type 3D-printed implants survived. Three solid-type 3D-printed implants were removed before the planned sacrifice date due to implant mobility. A slight, gradual increase in implant stability values from implant surgery to 4 weeks after surgery was observed in the lattice-type 3D-printed implants. The marginal bone change of the surviving solid-type 3D-printed implant was approximately 5 mm, whereas the value was approximately 2 mm in the lattice-type 3D-printed implants. BV/TV and BMD in the lattice type 3D-printed implants were similar to those in the surviving solid-type implant. However, BIC and BAFO were lower in the surviving solid-type 3D-printed implant than in the lattice-type 3D-printed implants. Conclusions: Within the limits of this preclinical study, 3D-printed implants of double-rooted teeth showed high primary stability. However, 3D-printed implants with interlocking structures such as lattices might provide high secondary stability and successful osseointegration.

• The Journal of Advanced Prosthodontics
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• v.16 no.2
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• pp.126-138
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• 2024

PURPOSE. The aim of this study was to evaluate the influence of different 3D dental resins, using a manufacturer recommended printer and a third-party printer, on cellular responses of human gingival cells. MATERIALS AND METHODS. Three NextDent resins (Denture 3D+, C&B MFH and Crowntec) were used to produce specimens on printers NextDent 5100 (groups ND, NC and NT, respectively) and Phrozen Sonic Mini 4K (groups PD, PC and PT, respectively). Human gingival fibroblasts were cultured and biocompatibility was evaluated on days 1, 3 and 7. IL-6 and IL-8 concentrations were evaluated at 3 days using ELISA. Surface roughness was evaluated by a contact profilometer. SEM and fluorescence micrographs were analyzed at days 1 and 7. Statistical analyses were performed using SPSS and mean differences were tested using ANOVA and post-hoc Tukey tests (P < .05). RESULTS. There was an increase in cellular viability after 7 days in groups PC and PT, when compared to group PD. ND group resulted in higher concentration of IL-6 when compared to PT group. SEM and fluorescence micrographs showed less adhesion and thinner morphology of fibroblasts from group PD. No significant differences were found regarding surface roughness. CONCLUSION. The use of different printers or resins did not seem to influence surface roughness. NextDent 5100 and Phrozen Sonic Mini 4K produced resins with similar cellular responses in human gingival fibroblasts. However, Denture 3D+ resin resulted in significantly lower biocompatibility, when compared to C&B MFH and Crowntec resins. Further testing is required to support its long-term use, required for complete dentures.

• Journal of the Microelectronics and Packaging Society
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• v.31 no.2
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• pp.63-68
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• 2024

With the increasing use of transparent displays and flexible devices, polymer substrates offering excellent flexibility and strength are in demand. Since polymers are sensitive to heat, precise temperature control during the process is necessary. The study proposes a temperature measurement system for the laser processing area within the polymer base, aiming to address the drawbacks of using these polymer bases in laser-based selective processing technology. It presents the possibility of optimizing the process conditions of the polymer substrate through local temperature change measurements in the laser processing area. We developed and implemented the PDPT (Photodiode-based Planck Thermometry) to measure temperature in the laser-processing area. PDPT is a non-destructive, contact-free system capable of real-time measurement of local temperature increases. We monitored the temperature fluctuations during the laser processing of the polymer substrate. The study shows that the proposed laser-based temperature measurement technology can measure real-time temperature during laser processing, facilitating optimal production conditions. Furthermore, we anticipate the application of this technology in various laser-based processes, including essential micro-laser processing and 3D printing.

• Journal of the Korean Society of Radiology
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• v.15 no.7
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• pp.965-973
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• 2021

Since radiation therapy is irradiated with high-energy X-rays in a variety of at least 20 Gy to 80 Gy, a high dose is administered to the local area where the tumor is located, and various side effects of some normal tissues are expected. Currently, in clinical practice, lead, a representative material, is used as an effort to shield normal tissues, but lead is classified as a heavy metal harmful to the human body, and a large amount of skin contact can cause poisoning. Therefore, this study intends to manufacture a measurement sheet that can compensate for the limitations of lead using the materials Tungsten, Brass, and Copper of the 3D printer of the FDM (Fused Deposition Modeling) method and to investigate the penetration performance. Tungsten mixed filament transmission measurement sheet size was 70 × 70 mm and thickness 1, 2, 4 mm using a 3D printer, and a linear accelerator (TrueBeam STx, S/N: 1187) was measured by irradiating 100 MU at SSD 100 cm and 5 cm in water using a water phantom, an ion chamber (FC-65G), and an elcetrometer (PTW UNIDOSE), and the permeability was evaluated. As a result of increasing the measurement sheet of each material by 1 mm, in the case of Tungsten sheet at 3.8 to 3.9 cm in 6 MV, the thickness of the lead shielding body was thinner than 6.5 cm, and in case of Tungsten sheet at 4.5 to 4.6 cm in 15 MV. The sheet was thinner than the existing lead shielding body thickness of 7 cm, and equivalent performance was confirmed. Through this study, the transmittance measurement sheet produced using Tungsten alloy filaments confirmed the possibility of transmission shielding in the high energy region. It has been confirmed that the usability as a substitute is also excellent. It is thought that it can be provided as basic data for the production of shielding agents with 3D printing technology in the future.