• 반도체디스플레이기술학회지
• /
• 제19권1호
• /
• pp.73-78
• /
• 2020

There appears lateral capillary force in a hydrophilic flat needle employed for the fabrication of fine organic thin-film stripes, bringing in an increase of the stripe width. It also causes the stripe thickness to increase with increasing coating speed, which is hardly observed in a normal coating process. Through computational fluid dynamics (CFD) simulations, we demonstrate that the lateral capillary flow can be substantially suppressed by increasing the contact angle of the needle end. Based on the simulation results, we have coated the outer surface of the flat needle with a hydrophobic material (polytetrafluoroethylene (PTFE) with the water contact angle of 104°). Using such a hydrophobic needle, we can suppress the lateral capillary flow of an aqueous poly(3,4-ethylenedioxythiophene): poly(4-styrenesulfonate) (PEDOT:PSS) to a great extent, rendering the stripe narrow (63 ㎛ at 30 mm/s). Consequently, the stripe thickness is decreased as the coating speed increases. To demonstrate its applicability to solution-processable organic light-emitting diodes (OLEDs), we have also fabricated OLED with the fine PEDOT: PSS stripe and observed the strong light-emitting stripe with the width of about 68 ㎛.

• 공업화학
• /
• 제21권3호
• /
• pp.317-322
• /
• 2010

본 연구에서는 폴리메틸메타아크릴에이트(polymethylmethacrylate : PMMA) 표면을 친수성으로 개질하기 위하여 불소와 산소의 혼합비율을 변수로 하여 함산소불소화를 실시하였다. 함산소불소화 처리 된 PMMA 표면 및 광투과 특성을 접촉각, 표면자유에너지. X-ray 광전자 분광기(XPS), UV-Vis 분광기를 통하여 분석하였다. 함산소불소화 처리된 PMMA의 표면은 친수화 되어 물 접촉각이 $69^{\circ}$에서 $44^{\circ}$로 감소하였다. 또한 PMMA의 표면자유에너지가 $46\;mN\;m^{-1}$ 에서 $58\;mN\;m^{-1}$로 증가하였다. 이는 함산소불소화를 통한 PMMA표면에 친수성 관능기의 형성으로 기인하였다. 또한, XPS 분석 결과로부터 함산소불소화 처리 시 PMMA 표면에 O/C비율이 증가하였고, 불소 부분압이 증가할수록 친수성을 나타내는 C-OH 결합의 �t량이 6.7%에서 24.8%로 증가하는 것을 알 수 있었다. 본 함산소불소화 조건(상온, 총압 1 bar, 불소 및 산소 혼합비 5 : 5)에서는 함산소불소화가 PMMA의 광투과 특성에 영향을 주지 않으면서도 그 표면특성이 개선됨을 관찰할 수 있었다. 이 결과로부터 함산소불소화는 PMMA 표면을 친수성으로 개질하는데 효과적인 방법으로 기대된다.

• 접착 및 계면
• /
• 제5권2호
• /
• pp.31-42
• /
• 2004

Many animals possess on their legs adhesive pads, which have undergone evolutionary optimization to be able to attach to variable substrates and to control adhesive forces during locomotion. Insect adhesive pads are either relatively smooth or densely covered with specialized adhesive hairs. Theoretical models predict that adhesion can be increased by splitting the contact zone into many microscopic, elastic subunits, which provides a functional explanation for the widespread 'hairy' design. In many hairy and all smooth attachment systems, the adhesive contact is mediated by a thin film of liquid secretion between the cuticle and the substrate. By using interference reflection microscopy (IRM), the thickness and viscosity of the secretion film was estimated in Weaver ants (Oecophylla smaragdina). 'Footprint' droplets deposited on glass are hydrophobic and form low contact angles. IRM of insect pads in contact showed that the adhesive liquid is an emulsion consisting of hydrophilic, volatile droplets dispersed in a persistent, hydrophobic phase. I tested predictions derived from film thickness and viscosity by measuring friction forces of Weaver ants on a smooth substrate. The measured friction forces were much greater than expected assuming a homogenous film between the pad and the surface. The findings indicate that the rubbery pad cuticle directly interacts with the substrate. To achieve intimate contact between the cuticle and the surface, secretion must drain away, which may be facilitated by microfolds on the surface of smooth insect pads. I propose a combined wet adhesion/rubber friction model of insect surface attachment that explains both the presence of a significant static friction component and the velocity-dependence of sliding friction.

• 대한의용생체공학회:학술대회논문집
• /
• 대한의용생체공학회 1991년도 추계학술대회
• /
• pp.96-97
• /
• 1991

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
• /
• pp.1457-1458
• /
• 2009

The fundamental parameters controlling ink-jet printing liquids are the viscosity and surface energy. The wetting contact angle determines the spread of a liquid drop on the surface and depends on the relative surface energy. The characteristics of silver ink-jet printing were studied with control of surface energy and head temperature. Polyethylene terephthalate(PET) film and Si-wafer(ptype) were used as substrates and atmospheric plasma was treated to control the surface energy. With silver ink, the hydrophilic surface treatment could reduce the radius of droplets due to the hydrophobic nature of silver ink.

• 접착 및 계면
• /
• 제20권4호
• /
• pp.146-154
• /
• 2019

본 연구에서는 소수성 PPO 사슬과 친수성 PEO 사슬들이 동시에 존재하고, 반응성 알콕시 실란기를 가지고 있는 알콕시 실란 기능화 양친성 고분자 전구체 (Alkoxysilane-functionalized Amphiphilic Polymer, AFAP)를 합성하여, 이를 TEOS과의 Hydrolysis- Polycondensation 반응에서 분산안정제 및 반응속도 조절제로 이용하여서 유-무기 하이브리드 나노입자가 안정적으로 분산된 졸 (Sol)을 제조하였다. 제조된 Sol에 불소 함유 실란화합물을 혼합·반응하여서 불소함유 유-무기 하이브리드 Sol을 제조하였고, 이를 유리 기재에 코팅하고 저온 경화를 통해 기재위에 경화필름을 형성하였다. 형성된 경화 필름은 AFAP 및 불소 함유 실란화합물의 첨가량, 용매 종류에 따라서 표면 경도 및 발수 특성이 변화하였다. 최적의 용매 및 불소 함유 실란화합물 첨가량에서 태양전지나 디스플레이에 적용가능한 투명하면서도 견고한 유-무기 하이브리드 형태의 코팅필름 형성이 가능하였다.

• 통합자연과학논문집
• /
• 제4권3호
• /
• pp.182-186
• /
• 2011

Chemical modification of porous silicon surface has been investigated to have different physical surface properties. Porous silicon modified with dodecyl functionality exhibits hydrophobic feature, however the oxidation of porous silicon to modify with hydroxyl group displays hydrophilic properties. Surface characterization for both dodecyl and hydroxyl derivatized porous silicon was investigated by FT-IR spectroscopy. To determine the surface coverage, the amine functionalized surface was reduced by dithiothreitol (DTT) and the released 2-thiopyridone was quantified by UV/vis spectroscopy.

• 마이크로전자및패키징학회지
• /
• 제9권4호
• /
• pp.31-34
• /
• 2002

For the mold die sticking mechanism, the major explanation is that the silica as a filler in EMC (epoxy molding compound) wears die surface to be roughened, which results in increase of adhesion strength. As the sticking behavior, however, showed strong dependency on the EMC models based on the experimental results from different semiconductor manufacturers, chemisorption or acid-base interaction is apt to be also functioning as major mechanisms. In this investigation, the plasma source ion implantation (PSII) using $O_2, N_2$, and $CF_4$ modifies sample surface to form a new dense layer and improve surface hardness, and change metal surface condition from hydrophilic to hydrophobic or vice versa. Through surface energy quantification by measuring contact angle and surface ion coupling state analysis by Auger, major governing mechanism for sticking issue was figured out to be a complex of mechanical and chemical factors.

• Interaction and multiscale mechanics
• /
• 제5권4호
• /
• pp.399-405
• /
• 2012

A dissipative particle dynamics (DPD) simulation was presented to analyze surface wettability and contact angles of a droplet on a solid platform. The many-body DPD, capable of modeling vapor-liquid coexistence, was used to resolve the vapor-liquid interface of a droplet. We found a constant density inside a droplet with a transition along the droplet boundary where the density decreased rapidly. The contact angle of a droplet was extracted from the isosurfaces of the density generated by the marching cube and a spline interpolation of 2D cutting planes of the isosurfaces. A wide range of contact angles from $55^{\circ}$ to $165^{\circ}$ predicted by the normalized parameter ($|A_{SL}|/B_{SL}$) were reported. Droplet with the parameters $|A_{SL}|>5.84B{_{SL}}^{0.297}$ was found to be hydrophilic. If $|A_{SL}|$ was much smaller than $5.84B{_{SL}}^{0.297}$, the droplet was found to be superhydrophobic.

• Macromolecular Research
• /
• 제16권7호
• /
• pp.609-613
• /
• 2008

Poly($\varepsilon$-caprolactone)-poly(ethylene glycol)-poly($\varepsilon$-caprolactone) (PCL-PEG-PCL) multiblock copolymers at various hydrophobic-hydrophilic ratios were successfully synthesized by the chain extension of triblock copolymers through isocyanate (hexamethylene diisocyanate). Biodegradable films were prepared from the resulting multiblock copolymers using the casting method. The mechanical properties of the films were improved by chain extension of the triblock copolymers, whereas the films prepared by the triblock copolymers were weak and brittle. Atomic force microscopy (AFM) of the multiblock copolymer film showed that the hydrophilic PEG had segregated on the film surface. This is consistent with the observed contact angle of the films.