• Current Optics and Photonics
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• v.1 no.4
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• pp.358-363
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• 2017

In this study, we present a detailed investigation of luminescence properties of a blue light-emitting diode using InGaN/GaN (indium component is 17.43%) multiple quantum wells as the active region grown on patterned sapphire substrate by low-pressure metal-organic chemical vapor deposition (MOCVD). High-resolution X-ray diffraction (HRXRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), Raman scattering (RS) and photoluminescence (PL) measurements are employed to study the crystal quality, the threading dislocation density, surface morphology, residual strain existing in the active region and optical properties. We conclude that the crystalline quality and surface morphology can be greatly improved, the red-shift of peak wavelength is eliminated and the superior blue light LED can be obtained because the residual strain that existed in the active region can be relaxed when the LED is grown on patterned sapphire substrate (PSS). We discuss the mechanisms of growing on PSS to enhance the superior luminescence properties of blue light LED from the viewpoint of residual strain in the active region.

• Polymer(Korea)
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• v.37 no.5
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• pp.656-662
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• 2013

The flexible patterned cover film was made by a simple solution coating process using polymethyl methacrylate (PMMA) solution with glass beads. The effect of patterned cover film on the efficiency of solar cell has been investigated. It was found that the relative solar cell efficiency increased up to 3.4% with the incident light angle between $0-90^{\circ}$ by the sphere shape of glass bead coated on the film surface. This was understood that the loss of transmittance and scattering due to the light directional dependency on solar cell were minimized because the light entered glass beads normal to its surface regardless of incident light angle. The maximum relative solar cell efficiency was achieved when glass bead shape on the film is hemisphere and the relative efficiency increased with increasing the amount of glass bead on the film surface. However, too much glass beads on the film surface resulted in the lower relative solar cell efficiency due to the lowering of transmittance as well as the occurring of light interference.

• Journal of ILASS-Korea
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• v.20 no.3
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• pp.181-186
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• 2015

This study presents the dynamic wetting characteristics of an impact droplet on hole-patterned textured surfaces. The flat surfaces were manufactured by a drilling machine to generate the micro-order holes, leading to make the surface hydrophobic. Other flat surfaces were fabricated by the anodizing technique to make hydrophilic texture surfaces with a nanometer order. For hydrophilic and hydrophobic textured surfaces with similar texture area fractions, the impinging droplet experiments were conducted and compared with flat surface cases. As results, an anodized textured surface decreases apparent equilibrium contact angle and increases contact diameters, because of increase in contact area and surface energy. This is attributed to more penetration inside holes from larger capillary pressure on nanometer-order holes. On the other hand, temporal evolution of the contact diameter is smaller for the hydrophobic textured surface from less penetration on the micro-order holes.

• Korean Journal of Materials Research
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• v.23 no.3
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• pp.177-182
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• 2013

Nanosphere lithography is an inexpensive, simple, high-throughput nanofabrication process. NSL can be done in different ways, such as drop coating, spin coating or by means of tilted evaporation. Nitride-based light-emitting diodes (LEDs) are applied in different places, such as liquid crystal displays and traffic signals. The characteristics of gallium nitride (GaN)-based LEDs can be enhanced by fabricating nanopatterns on the top surface of the LEDs. In this work, we created differently sized (420, 320 and 140 nm) nanopatterns on the upper surfaces of GaN-based LEDs using a modified nanosphere lithography technique. This technique is quite different from conventional NSL. The characterization of the patterned GaN-based LEDs revealed a dependence on the size of the holes in the pattern created on the LED surface. The depths of the patterns were 80 nm as confirmed by AFM. Both the photoluminescence and electroluminescence intensities of the patterned LEDs were found to increase with an increase in the size of holes in the pattern. The light output power of the 420-nm hole-patterned LED was 1.16 times higher than that of a conventional LED. Moreover, the current-voltage characteristics were improved with the fabrication of differently sized patterns over the LED surface using the proposed nanosphere lithography method.

• 전자공학회논문지 IE
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• v.47 no.2
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• pp.8-12
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• 2010

TEM is a powerful tool for semiconductor material analyses in structure or biological sample in micro structure. TEM observation need to make to coincide specimens for special purpose. in this paper, we have experimented for minimum surface damage on bulk wafer and patterned specimen by various conditions such as accelerating energy, depth of ion beam, ion milling types, and etc. in various specimen preparation methods by FIB (Focus Ion Beam). The optimal qualified specimens are contain low mounts of surface damage(about 5 nm) on patterned specimen.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.29 no.2
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• pp.111-118
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• 2023

In this study, the feasibility of laser patterning on the surface of food packaging polymer film was confirmed, and the surface patterning process conditions of femtosecond laser were established. In addition, it was proved that the surface properties of the film can be changed and controlled through the fabrication of various patterned films on the surface of food packaging films such as HDPE, PP, and PET. Various patterned surfaces, including large-scale circular patterns induced by a single femtosecond laser pulse, roughness patterns achieved by overlapping single pulses by 30%, straight line patterns, roughness patterns obtained by overlapping straight line patterns, and grid patterns formed by intersecting straight line patterns were fabricated. The characteristics of the patterned HDPE, PP, and PET films, based on the surface pattern structure and size, were analyzed using SEM, AFM, and contact angle measurements. Compared to the surface of each control film without femtosecond laser patterning, the contact angles of the surfaces of large-area circular patterning HDPE and PP films, large-area roughness patterning HDPE and PP films by overlapping 30% of single pulses, and large-area roughness patterning PET film by overlapping rectilinear patterning were in the range of 27.1-37.5 degree. This indicated that the HDPE, PP, and PET films became more hydrophilic after patterning. On the other hand, the HDPE film patterned with a large-scale grid pattern exhibited a contact angle of 120.4 degree, indicating that the HDPE film became more hydrophobic after patterning. Therefore, films that have been changed to hydrophilic surfaces through patterning can be used in anti-fouling applications where proteins, cells, viruses, and other food materials do not adhere or are easily detached. In addition, if a superhydrophobic surface of 150 degrees or more is fabricated through more precise lattice patterning in the future, it will be possible to use it for superhydrophobic surface applications such as self-cleaning.

• Journal of Biomedical Engineering Research
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• v.40 no.1
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• pp.1-6
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• 2019

Human mesenchymal stem cells (hMSC) are multipotent stromal cells that have great potential to differentiate into a variety of cell types such as osteocytes, chondrocytes, and myocytes. Although there have been many studies on their clinical availability, little is known about how intracellular signals can be modulated by topographic features of the extracellular matrix (ECM). In this study, we investigated whether and how microwavy-patterned extracellular matrix (ECM) could affect the signaling activity of focal adhesion kinase (FAK), a key cellular adhesion protein. The fluorescence resonance energy transfer (FRET)-based FAK biosensor-transfected cells are incubated on microwavy-patterned surfaces and then platelet derived growth factor (PDGF) are treated to trigger FAK signals, followed by monitoring through live-cell FRET imaging in real time. As a result, we report that PDGF-induced FAK was highly activated in cells cultured on microwavy-patterned surface with L or M type, while inhibited by H type-patterned surface. In further studies, PDGF-induced FAK signals are regulated by functional support of actin filaments, microtubules, myosin-related proteins, suggesting that PDGF-induced FAK signals in hMSC upon microwavy surfaces are dependent on cytoskeleton (CSK)-actomyosin networks. Thus, our findings not only provide new insight on molecular mechanisms on how FAK signals can be regulated by distinct topographical cues of the ECM, but also may offer advantages in potential applications for regenerative medicine and tissue engineering.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.471-474
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• 2004

We investigated field emission (FE) characteristics of multi-walled carbon nanotubes (CNTs) grown on all over patterned cathode electrode lines (CL pattern) and grown on along the central areas of the cathode lines(CL pattern). The CNTs grown on the SL pattern showed a lower threshold voltage and higher emission current than those on the CL pattern, due to the concentration of electric fields at the edges of the cathode lines. For the SL-patterned CNTs, however, the FE gradually spread out to the neighbors with time, and was instantly extinguished in some area and then slowly resumed again. Such areal- spread FE did not occur for the CL-patterned sample, leading to the stable FE together with the instant turn-on capability. It is suggested that the spread FE and instability for the SL-patterned CNTs may be related to the electrical charging on the insulator surface around the cathode line edges.

• Journal of Periodontal and Implant Science
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• v.47 no.6
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• pp.402-415
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• 2017

Purpose: The aim of this study was to determine the effects of patterned human periodontal ligament stem cell (hPDLSC) sheets fabricated using a thermoresponsive substratum. Methods: In this study, we fabricated patterned hPDLSC sheets using nanotopographical cues to modulate the alignment of the cell sheet. Results: The hPDLSCs showed rapid monolayer formation on various surface pattern widths. Compared to cell sheets grown on flat surfaces, there were no significant differences in cell attachment and growth on the nanopatterned substratum. However, the patterned hPDLSC sheets showed higher periodontal ligamentogenesis-related gene expression in early stages than the unpatterned cell sheets. Conclusions: This experiment confirmed that patterned cell sheets provide flexibility in designing hPDLSC sheets, and that these stem cell sheets may be candidates for application in periodontal regenerative therapy.

• Bulletin of the Korean Chemical Society
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• v.26 no.10
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• pp.1539-1542
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• 2005

We have introduced polyelectrolyte micro-patterning technique employing agarose plane stamp and a hard substrate having microscale features on its surface. With this method, chemically micropatterned surfaces with both positive and negative functionalities were successfully embedded in well-defined microstructures, and selective impartment of charge functionalities was confirmed by patterning bead bearing surface charge. Furthermore, this technique allows highly sensitive immobilization of protein onto targeted surface simply by endowing functionalities, which extends the potential of its use as a tool for high-throughput protein microarray and proteomics. Because plane agarose stamp is free of structures on its surface, there is no concern for pattern collapse, and the combination of agarose plane stamp with patterned substrate is more suited for selective protein patterning compared with adopting surface-patterned agarose stamp with flat substrate. Our technique using agarose plane stamp and a substrate having microscale features on its surface suggests a range of possible applications, including the micropatterning of biofunctionalized copolymer having polyelectrolyte block, immobilization of micro- and nanoparticle with biofunctionalities such as biotin and streptavidine, and establishing optoelectronic microstructures with micro-beads on various surfaces.