• International Journal of Precision Engineering and Manufacturing
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• 제7권4호
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• pp.14-17
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• 2006

A thin GaN semiconducting film that grows on sapphires due to metalorganic chemical vapor deposition was machined for nanophotonic applications. The thin film had multilayered superlattice structures, including nanoscaled InGaN layers. Eight alternating InGaN/GaN multilayers provided a blue light emission source. Nanoscaled holes, 150 nm in diameter, were patterned on polymethylmethacrylate (PMMA) film using an electron beam lithography system. The PMMA film blocked the etching species. Air holes, 75 nm in diameter, which acted as blue light diffraction sources, were etched on the top GaN layer by an inductively coupled plasma etcher. Hexagonal lattice photonic crystals were fabricated with 230-, 460-, 690-, and 920-nm pitches. The 450-nm wavelength blue light provided the nanodiffraction destructive and constructive interferences phenomena, which were dependent on the pitch of the holes.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.198-198
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• 2012

Graphene has been the subject of intense study in recent years owing to its good optoelectronic properties, possibility for stretchable electronics, and so on. Especially, many research groups have studied about graphene nanostructures with various sizes and shapes. Graphene needs to be fabricated into useful devices with controllable electrical properties for its successful device applications. However, this been far from satisfaction owing to a lack of reliable pattern transfer techniques. Photolithography, nanowire etching, and electron beam lithography methods are commonly used for construction of graphene patterns, but those techniques have limitations for getting controllable GNRs. We have developed a novel nanoscale pattern transfer technique based on an electro-hydrodynamic lithography providing highly scalable versatile pattern transfer technique viable for industrial applications. This technique was exploited to fabricate nanoscale patterned graphene structures in a predetermined shape on a substrate. FE-SEM, AFM, and Raman microscopy were used to characterize the patterned graphene structures. This technique may present a very reliable high resolution pattern transfer technique suitable for graphene device applications and can be extended to other inorganic materials.

• 대한기계학회논문집A
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• 제31권6호
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• pp.679-685
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• 2007

Superhydrophobic surface, with a water contact angle greater than $150^{\circ}$, has a self-cleaning effect termed 'Lotus effect'. This surface is created by the combination of rough surface and the low surface energy. We proposed square pillar and square shapes to control surface roughness. Microstructure arrays are fabricated by DRIE(Deep Reactive Ion Etching) process and followed by PPFC(Plasma Polymerized Fluorocarbon) deposition. On the experimental result, contact angle at square pillar arrays is well matched with Cassie's model and largest contact angle is $173.37^{\circ}$. But contact angle of square pore shape arrays is lower than Cassie's theoretical contact angle about $5{\sim}10%$. Nevertheless, square pore arrays have more rigidity than square pillar arrays.

• 한국전기전자재료학회논문지
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• 제26권3호
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• pp.171-176
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• 2013

In this paper, we present a MEMS (micro-electro-mechanical system) implantable blood pressure sensor which has designed and fabricated with consideration of size, design flexibility, and wireless detection. Mechanical and electrical characterizations of the sensor were obtained by mathematical analysis and computer aided simulation. The sensor is composed of two coils and a air gap capacitor formed by separation of the coils. Therefore, the sensor produces its resonant frequency which is changed by external pressure variation. This frequency movement is detected by inductive coupling between the sensor and an external antenna coil. Theoretically analyzed resonant frequency of the sensor under 760 mmHg was calculated to 269.556 MHz. Fused silica was selected as sensor material with consideration of chemical and electrical reaction of human body to the material. $2mm{\times}5mm{\times}0.5mm$ pressure sensors fitted to radial artery were fabricated on the substrates by consecutive microfabrication processes: sputtering, etching, photolithography, direct bonding and laser welding. Resonant frequencies of the fabricated sensors were in the range of 269~284 MHz under 760 mmHg pressure.

• 한국표면공학회지
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• 제57권1호
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• pp.49-56
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• 2024

Superhydrophobic surfaces have been expected to be able to provide considerable performance improvements and introduce innovative functions across diverse industries. However, representative methods for fabricating superhydrophobic surfaces include etching the substrate or attaching nanosized particles, but they have been limited by problems such as applicability to only a few materials or low adhesion between particles and substrates, resulting in a short lifetime of superhydrophobic properties. In this work, we report a novel coating technique that can achieve superhydrophobicity by electrophoretic deposition of aluminum nitride (AlN) nanopowders and their self-bonding to form a surface structure without the use of binder resins through a hydrolysis reaction. Furthermore, by using a water-soluble adhesive as a temporary shield for the electrophoretic deposited AlN powders, hierarchical aluminum hydroxide structures can be strongly adhered to a variety of electrically conductive substrates. This binder-free technique for creating hierarchical structures that exhibit strong adhesion to a variety of substrates significantly expands the practical applicability of superhydrophobic surfaces.

• 마이크로전자및패키징학회지
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• 제23권2호
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• pp.73-78
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• 2016

집적회로(Integrated Circuit) 소자의 트랜지스터(transistor) 밀도 증가는 소자에서 발생하는 열 방출(heat dissipation)의 급격한 상승을 초래하여 열 문제를 발생시키고, 이는 소자의 성능과 열적 신뢰성에 영향을 크게 미친다. 열문제의 해결방안 중 본 연구에서는 냉매를 이용한 액체 냉각방법을 연구하였으며, 실리콘 웨이퍼에 관통실리콘비아(through Si via)와 마이크로 채널(microchannel)을 딥 반응성 이온 애칭(deep reactive ion etching)로 구현한 후 유리기판과 어노딕본딩을 통하여 액체 냉각 구조를 제작하였다. 제작된 마이크로 채널 위에 Ag, Cu 또는 Cr/Au/Cu bump를 스크린프린팅(screen printing) 방법으로 형성하였고, 범프의 유무를 통해 액체 냉각 전후의 냉각 모듈의 실리콘 표면온도의 변화를 적외선현미경으로 분석하였다. Cr/Au/Cu bump가 탑재된 액체 냉각 모듈의 경우 가열온도 $200^{\circ}C$에서 냉각 전후의 실리콘 표면 온도 차이는 약 $45.2^{\circ}C$이고, 전력밀도 감소는 약 $2.8W/cm^2$ 이었다.

• 한국재료학회지
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• 제22권2호
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• pp.66-70
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• 2012

Ti-Ni alloys are widely used in numerous biomedical applications (e.g., orthodontics, cardiovascular science, orthopaedics) due to their distinctive thermomechanical and mechanical properties, such as the shape memory effect, superelasticity and low elastic modulus. In order to increase the biocompatibility of Ti-Ni alloys, many surface modification techniques, such as the sol-gel technique, plasma immersion ion implantation (PIII), laser surface melting, plasma spraying, and chemical vapor deposition, have been employed. In this study, a Ti-49.5Ni (at%) alloy was electrochemically etched in 1M $H_2SO_4$+ X (1.5, 2.0, 2.5) wt% HF electrolytes to modify the surface morphology. The morphology, element distribution, crystal structure, roughness and energy of the surface were investigated by scanning electron microscopy (SEM), energy-dispersive Xray spectrometry (EDS), X-ray diffractometry (XRD), atomic force microscopy (AFM) and contact angle analysis. Micro-sized pores were formed on the Ti-49.5Ni (at%) alloy surface by electrochemical etching with 1M $H_2SO_4$+ X (1.5, 2.0, 2.5) wt% HF. The volume fractions of the pores were increased by increasing the concentration of the HF electrolytes. Depending on the HF concentration, different pore sizes, heights, surface roughness levels, and surface energy levels were obtained. To investigate the osteoblast adhesion of the electrochemically etched Ti-49.5Ni (at%) alloy, a MTT test was performed. The degree of osteoblast adhesion was increased at a high concentration of HF-treated surface structures.

• 센서학회지
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• 제24권6호
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• pp.373-378
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• 2015

The structure of the human ear is divided into the outer ear, the middle ear, and the inner ear. The inner ear includes the cochlea that plays a very important role in hearing. Recently, the development of an artificial cochlear device for the hearing impaired with cochlear damage has been actively researched. Research has been carried out on the biomimetic piezoelectric thin film ABM (Artificial Basilar Membrane) in particular. In an effort to improve the frequency separation performance of the existing piezoelectric thin film ABM, this paper presents the design, fabrication, and characterization of the production and performance of a partially etched-type ABM material. $O_2$ plasma etching equipment was used to partially etch a piezoelectric thin film ABM to make it more flexible. The mechanical-behavior characterization of the manufactured partially etched-type ABM showed that the overall separation frequency range shifted to a lower frequency range more suitable for audible frequency bandwidths and it displayed an improved frequency separation performance. In addition, the maximum magnitude of the vibration displacement at the first local resonant frequency was enhanced by three times from 38 nm to 112 nm. It is expected that the newly designed, partially etched-type ABM will improve the issue of cross-talk between nearby electrodes and that the manufactured partially etched-type ABM will be utilized for next-generation ABM research.

• Tribology and Lubricants
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• 제37권5호
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• pp.189-194
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• 2021

A straightforward, yet effective surface modification method of stainless steel mesh and its interesting anti-wetting characteristics are reported in this study. The stainless steel mesh is electrochemically etched, and the specimen has both micro and nano-scale structures on its surface. This process transforms the two types of mesh specimens known as the regular and dense specimens into hydrophobic specimens without applying any hydrophobic chemical coating process. The fundamental wettability of the modified mesh is analyzed through a dedicatedly designed experiment to investigate the waterproof characteristics, for instance, the penetration threshold. The waterproof characteristics are evaluated in a manner that the modified mesh resists as high as approximately 2.7 times the pressure compared with the bare mesh, i.e., the non-modified mesh. The results show that the penetration threshold depends primarily on the advancing contact angles, and the penetration stop behaviors are affected by the contact angle hysteresis on the surfaces. The findings further confirm that the inexpensive waterproof meshes created using the proposed straightforward electrochemical etching process are effective and can be adapted along with appropriate designs for various practical applications, such as underwater devices, passive valves, and transducers. In general, , additional chemical coatings are applied using hydrophobic materials on the surfaces for the applications that require water-repelling capabilities. Although these chemical coatings can often cause aging, the process proposed in this study is not only cost-effective, but also durable implying that it does not lose its waterproof properties over time.

• 대한기계학회논문집B
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• 제39권4호
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• pp.301-307
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• 2015

MC-50 사이클로트론에서 방출되는 양성자 빔은 직경이 2-3 mm 의 가우시안 분포를 가진다. 이렇게 넓게 조사되는 양성자 빔은 작은 스팟과 정밀한 위치정밀도를 요구하는 반도체 식각, 마이크로 머시닝 등에는 사용될 수 없다. 본 연구에서는 좀 더 경제적인 대안으로 양성자 빔을 마이크로 홀에 통과시켜 수십 ${\mu}m$ 의 직경을 가지도록 조형하는 방법을 제시하였다. 양성자 빔의 조형을 위하여 평균 직경 $21{\mu}m$, 두께 9mm 의 세장비 428 의 마이크로 홀을 제작하였다. 마이크로 홀과 양성자 빔을 정밀하게 정렬하여 양성자 빔을 조형하였다. 이렇게 조형된 양성자 빔을 이용하여 수십 ${\mu}m$ 크기의 마이크로 구조물의 가공성 확인 실험을 실시하였다. 또한 GEANT4 를 이용한 전산모사를 이용하여 해석한 후, 실험결과와 비교하고 분석하였다. 본 연구를 통하여 MC-50 사이클로트론이 조형 장치와 함께 20 마이크론 대의 3 차원 구조물 제작을 위한 마이크로 공정기술에의 사용 가능성을 확인하였다.