• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.1
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• pp.96-101
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• 2017

We have developed a compact desktop-sized nanopatterning system driven by the Roll-to-Roll (R2R) nanoimprinting (NIL) principle. The system realizes the continuous and high-speed stamping of various nanoscale patterns on a large-area flexible substrate without resorting to ponderous and complicated instruments. We first lay out the process principle based on continuous NIL on a UV-curable resin layer using a flexible nanopatterned mold. We then create conceptual and specific designs for the system by focusing on two key processes, imprinting and UV curing, which are performed in a continuous R2R fashion. We build a system with essential components and optimized modules for imprinting, UV curing, and R2R conveying to enable simple but effective nanopatterning within the desktop volume. Finally, we demonstrate several nanopatterning results such as nanolines and nanodots, which are obtained by operating the built desktop R2R NIL system on transparent and flexible substrates. Our system may be further utilized in the scalable fabrication of diverse flexible nanopatterns for many functional applications in optics, photonics, sensors, and energy harvesters.

• Journal of the Microelectronics and Packaging Society
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• v.25 no.3
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• pp.49-53
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• 2018

Since various methods to form well-aligned nano-/micro- patterns are underlying technologies to fabricate next generation wearable electronic devices, many efforts have been made to realize finer patterns in recent years. Among lots of patterning methods, the present invention includes a nano-transfer printing (n-TP) process which is advantageous in that a processing cost is low and high-resolution patterns can be formed within a short processing time. We successfully achieved pattern formation of highly ordered Pt lines with line-width of 250 nm, 500 nm, and $1{\mu}m$ on transparent and flexible substrates. In addition, we analyzed the durability of the patterns, showing excellent stability of line-shape even after a physical and repeated bending test of 500 times using a bending machine. As a result, it is expected that a n-TP process is very useful for forming various metal patterns, and it is also expected to be applied to wiring and interconnection technology of next generation flexible electronic devices.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.244-245
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• 2010

최근 광전자 분야에서는 미래 에너지 자원에 대한 관심과 함께 GaN 기반 발광다이오드 및 태양전지 연구가 활발히 진행되고 있다. GaN는 높은 전자 이동도와 높은 포화 속도 등의 광전자 소자에 유리한 특성을 가지고 있으나, 고 인듐 함유량과 막질의 우수한 특성을 동시에 구현하는 것은 매우 어렵다. 이를 극복하기 위한 방법으로써 선택 영역 박막 성장법(Selective Area Growth)은 마스크 패터닝을 통해 제한된 영역에서만 박막을 성장하는 방법으로써 GaN의 막질을 향상 시킬 수 있는 방법으로 주목받고 있다. 본 논문에서는 대면적 기판에서 GaN의 막질 향상뿐만 아니라 고인듐 InGaN 박막 성장을 위하여 서브마이크로미터 주기와 크기를 갖는 홀 패턴을 포토리소그라피 공정 최적화를 통해 구현할 수 있는 방법에 대해 논의한다. 그림. 1은 사파이어 기판 위에 선택 영역 박막 성장법을 이용하여 성장한 n-GaN/활성층/p-GaN의 구조를 나타낸 그림이다. 이를 통하여 서브마이크로미터 스케일의 반극성 InGaN면 위에 높은 인듐 함유량을 가지면서도 우수한 특성을 갖는 박막을 얻을 수 있다. 본 실험을 위하여 사파이어 기판 위에 SiO2를 증착한 후 포토레지스트(AZ5206)을 도포하고 포토리소그라피 공정을 진행하여 2um 크기 및 간격을 갖는 패턴을 형성했다. 그림. 2는 AZ5206에 UV를 조사(5초)하고 현상(23초)한 패턴을 윗면(그림. 2(a))과 $45^{\circ}$ 기울인 면(그림. 2(b)) 에서 본 SEM(Scanning Electron Microscope) 사진이다. 이를 통해 약 2.2um의 홀 패턴이 선명하게 형성 됨을 볼 수 있다. 그 후 수백나노 직경의 홀을 만들기 위해서 리플로우 공정을 수행한다. 그림. 3은 리플로우 온도에 따른 패턴의 홀 모양을 AFM(Atomic Force Microscope)을 이용하여 측정한 표면의 사진이다. 이를 통해 2차원 평면에서 리플로우 온도 및 시간에 따른 변화를 볼 수 있다. 그림.3의 (a)는 리플로우 공정을 진행하기 전 패턴이고, (b)는 $150^{\circ}C$에서 2분, (c)는 $160^{\circ}C$에서 2분 (d)는 $170^{\circ}C$에서 2분 동안 리플로우 공정을 진행한 패턴이다. $150^{\circ}C$와 $160^{\circ}C$에서는 직경에 큰 변화가 없었고, $160^{\circ}C$에서는 시료별 현상 시간 오차에 따라 홀의 크기가 커지는 경향이 나타났다. 그러나 $170^{\circ}C$에서 2분간 리플로우 한 시료 (그림. 3(d))의 경우는 홀의 직경이 ~970nm 정도로 줄어든 것을 볼 수 있다. 홀의 크기를 보다 명확히 표현하기 위해 그림.3에 대응시켜 단면을 스캔한 그래프가 그림.4에 나타나 있다. 그림.4의 (a) 및 (b)의 경우 포토레지스트의 높이 및 간격이 일정하므로, 리플로우에 의한 영향은 거의 없었다. 그림. 4(c)의 경우 포토레지스트의 높이가 그림.4(a)에 비해 ~25nm 정도 낮은 것으로 볼 때, 과도 현상 및 약간의 리플로우가 나타났을 가능성이 크다. 그림. 4(d)에서는 ~970nm의 홀 크기가 나타나서 본 연구에서 목표로 하는 나노 홀 크기에 가장 가까워짐을 확인할 수 있었다. 따라서, $170^{\circ}C$ 이상의 온도와 2분 이상의 리플로우 시간 조건에서 선택 영역 성장을 위한 나노 홀 마스크의 크기를 제어할 수 있음을 확인하였다.

• KSBB Journal
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• v.22 no.6
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• pp.371-377
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• 2007

Polyhydroxyalkanoates (PHAs) are a family of microbial polyesters that can be produced by fermentation from renewable resources. PHAs can be used as completely biodegradable plastics or elastomers. In this paper, novel applications of PHAs in biosensor are described. A general platform technology was developed by using the substrate binding domain (SBD) of PHA depolymerase as a fusion partner to immobilize proteins of interest on PHA surface. It could be shown that the proteins fused to the SBD of PHA depolymerase could be specifically immobilized onto PHA film, PHA microbead, and microcontact printed PHA surface. We review the results obtained for monitoring the specific interaction between the SBO and PHA by using enhanced green fluorescent protein, red fluorescent protein, single chain antibody against hepatitis B virus preS2 surface protein and severe acute respiratory syndrome coronavirus surface antigen as model proteins. Thus, this system can be efficiently used for studying protein-protein and possibly protein-biomolecule interactions for various biotechnological applications.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.6
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• pp.1047-1055
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• 2006

We patterned nano-width lines on a super hard bulk diamond substrate by varying the ion beam current and ion beam sources with a dual beam field ion beam (FIB). In addition, we successfully fabricated two-dimensional nano patterns and three-dimensional nano plate modules. We prepared nano lines on a diamond and a silicon substrate at the beam condition of 30 kV, 10 pA $\sim$ 5 nA with $Ga^+$ ion and $H_2O$ assisted ion sources. We measured each of the line-width, line-depth, etched line profiles, etch rate, and aspect ratio, and then compared them. We confirmed that nano patterning was possible on both a bulk diamond and a silicon substrate. The etch rate of $H_2O$ source can be enhanced about two times than that of Ga source. The width of patterns on a diamond was smaller than that on a silicon substrate at the same ion beam power The sub-100 nm patterns on a diamond were made under the charge neutralization mode to prevent charge accumulation. We successfully made a two-dimensional, 240 nm-width text of the 300-lettered Lord's Prayer on a gem diamond with 30 kV-30 pA FIB. The patterned text image was readable with a scanning electron microscope. Moreover, three dimensional nano-thick plate module fabrication was made successfully with an FIB and a platinum deposition, and electron energy loss spectrum (EELS) analysis was easily performed with the prepared nano plate module.

• Korean Journal of Optics and Photonics
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• v.14 no.1
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• pp.97-102
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• 2003

Multi-channel images of 11-MUA(11-Mercaptoundecanoic acid) and 11-MUOH(11-Mercaptoundecanol) self-assembled monolayers were obtained by using two-dimensional surface plasmon resonance (SPR) absorption. The patterning process was simplified by exploiting direct photo-oxidation of thiol bonding (photolysis) instead of conventional photolithography. Sharper images were resolved by using a white light source in combination with a narrow bandpass filter in the visible region, minimizing the diffraction patterns on the images. The line profile calibration of the image contrast caused by different resonance conditions at each point on the sensor surface (at a fixed incident angle) enables us to discriminate the monolayer thickness in nanometer scale. Furthermore, there is no signal degradation such as photo bleaching or quenching, which are common in the detection methods based on fluorescence.

• Journal of the Korean institute of surface engineering
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• v.49 no.6
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• pp.555-559
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• 2016

A biodegradable nanofiber scaffolds using electrospining provide fibrous guidance cues for controlling cell fate that mimic the native extracellular matrix (ECM). It can create a pattern using conventional electrospining method, but has a difficulty to generate one or more pattern structures. Femtosecond(fs) laser ablation has much interested in patterning on biomaterials in order to distinguish the fundamental or systemic interaction between cell and material surface. The ablated materials with a short pulse duration using femtosecond laser that allows for precise removal of materials without transition of the inherent material properties. In this study, linear grooves and circular craters were fabricated on electrospun nanofiber scaffolds (poly-L-lactide(PLLA)) by femtosecond laser patterning processes. As parametric studies, pulse energy and beam spot size were varied to determine the effects of the laser pulse on groove size. We confirmed controlling pulse energy to $5{\mu}J-20{\mu}J$ and variation of lens maginfication of 2X, 5X, 10X, 20X created grooves of width to approximately $5{\mu}m-50{\mu}m$. Our results demonstrate that femtosecond laser processing is an effective means for flexibly structuring the surface of electrospun PLLA nanofibers.

• KSBB Journal
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• v.23 no.3
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• pp.263-270
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• 2008

A poly-(dimethylsiloxane) (PDMS) surface modified by the successive deposition of the polyelectrolytes, poly-(allylamine hydrochloride) (PAH), poly-(diallyldimethylammoniumchloride) (PDAC), poly-(4-ammonium styrenesulfonic acid) (PSS), and poly-(acrylic acid) (PAA), was presented for the application of selective cell immobilization. It is formed via electrostatic attraction between adjacent layers of opposite charge. The modified PDMS surface was examined using static contact angle measurements and fourier transform infrared (FT-IR) spectrophotometer. The wettability of the PDMS surface could be easily controlled and functionalized to be biocompatible through regulation of layer numbers. The modified PDMS surface provides appropriate environment for adhesion to cells, which is essential technology for cell patterning with high yield and viability in the patterning process. This method is reproducible, convenient, and rapid. It could be applied to the fabrication of biological sensing, patterning, microelectronics devices, screening system, and study of cell-surface interaction.

• Journal of the Korean Magnetics Society
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• v.17 no.4
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• pp.156-161
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• 2007

To develop array magnetic sensors, specular-type giant magnetoresistive- spin valve (GMR-SV) film of Glass/Ta(5)MiFe(7)/IrMn(10)NiFe(5)/$O_2$/CoFe(5)/Cu(2.6)/CoFe(5)/$O_2$/NiFe(7)/Ta(5)(nm) was deposited by using a high-vacuum sputtering system. One of 15 way sensors in the area of $8{\times}8mm^2$ was Patterned a size of $20{\times}80{\mu}m^2$ in multilayer sample by Photo-lithography. All of 15 sensors with Cu electrodes were measured a uniform magnetic properties by 2-probe method. The highest magnetic sensitivity of MR and output voltage measured nearby an external magnetic field of 5 Oe were MS = 0.5%/Oe and ${\triangle}$V= 3.0 mV, respectively. An easy-axis of top-free layers of $CoFe/O_2/NiFe$ with shape anisotropy was perpendicular to one of bottom-pinned layers $IrMn/NiFe/O_2/CoFe$. When the sensing current increased from 1 mA to 10 mA, the output working voltage uniformly increased and the magnetic sensitivity was almost stable to use the nano-magnetic devices with good sensitive properties.