• Tribology and Lubricants
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• 제22권5호
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• pp.243-251
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• 2006

Molecular dynamics simulations of nanoimprint lithography NIL) are performed in order to investigate effects of process parameters, such as stamp shape, imprinting temperature and adhesive energy, on nanoimprint lithography process and pattern transfer. The simulation model consists of an amorphous $SiO_{2}$ stamp with line pattern, an amorphous poly-(methylmethacrylate) (PMMA) film and an Si substrate under periodic boundary condition in horizontal direction to represent a real NIL process imprinting long line patterns. The pattern transfer behavior and its related phenomena are investigated by analyzing polymer deformation characteristics, stress distribution and imprinting force. In addition, their dependency on the process parameters are also discussed by varying stamp pattern shapes, adhesive energy between stamp and polymer film, and imprinting temperature. Simulation results indicate that triangular pattern has advantages of low imprinting force, small elastic recovery after separation, and low pattern failure. Adhesive energy between surface is found to be critical to successful pattern transfer without pattern failure. Finally, high imprinting temperature above glass transition temperature reduces the imprinting force.

• 한국가시화정보학회지
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• 제5권1호
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• pp.3-8
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• 2007

We present simple methods for fabricating high aspect-ratio polymer nanostructures on a solid substrate by rigiflex lithography with tailored capillarity and adhesive force. In the first method, a thin, thermoplastic polymer film was prepared by spin coating on a substrate and the temperature was raised above the polymer's glass transition temperature ($T_g$) while in conformal contact with a poly(urethane acrylate) (PUA) mold having nano-cavities. Consequently, capillarity forces the polymer film to rise into the void space of the mold, resulting in nanostructures with an aspect ratio of ${\sim}4$. In the second method, very high aspect-ratio (>20) nanohairs were fabricated by elongating the pre-formed nanostructures upon removal of the mold with the aid of tailored capillarity and adhesive force at the mold/polymer interface. Finally, these two methods were further used to fabricate micro/nano hierarchical structures by sequential application of the molding process for mimicking nature's functional surfaces such as a lotus leaf and gecko foot hairs.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 춘계학술대회 논문집
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• pp.280-281
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• 2009

Piezoelectric vibrators can be good replacements of electric motors to excite touch screen of a mobile device owing to small volume and low power consumption. One problem to be solved yet for real application is larger excitation force or moment than available currently. More efficient excitation by a piezoelectric vibrator could be achieved by operating at one of resonance frequencies of the system, which must also be as close as possible to frequency range where index finger is most sensitive and increasing transmission force or moment at that frequency. In this study, dynamic models are derived for the piezoelectric exciter and an adhesive viscoelastic layer, which connect the exciter to the screen. The adhesive layer is modeled as distributed stiffness by considering its geometric shape to relative to the piezoelectric exciter. Then, equations of motion for the piezoelectric exciter and the adhesive layer are derived using Hamilton's principle. Based on this model, dynamic characteristics of the exciter will be designed to maximize the force or moment transmitted onto the screen structure.

• 전자공학회논문지 IE
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• 제44권3호
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• pp.42-50
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• 2007

거칠기를 고려한 응착모델들에 있어서 탄성 응착 지수와 소성 응착 지수가 중요한 매개변수이며, 본 논문에서는 매개 변수를 변화시켜 무차원화 된 하중과 분리힘의 특성을 시뮬레이션 하고 분석하였다. AFM을 이용하여 실험 샘플의 표면 거칠기 관련 특성 값들을 얻었으며, 이를 이용하여 상호작용을 고려한 경우와 고려하지 않은 경우의 분리힘을 계산하였다. 계산된 분리힘들을 팁과 샘플 표면 사이의 측정된 분리힘과 비교하였고, 이를 통하여 표면 거칠기 돌기의 상호작용으로 인한 변형이 응착 특성에 중요한 영향을 미치는 인자임을 알 수 있었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 B
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• pp.1000-1002
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• 2002

In electric motor coaches, the rolling stocks move by the adhesive effort between rail and driving wheel. Generally, the adhesive effort is defined by the function of both the weight of electric motor coach and the adhesive effort between rails and driving wheel. The characteristics of adhesive effort is strongly affected by the conditions between rails and driving wheel. When the adhesive effort decreases suddenly, the electric motor coach has slip phenomena. This paper proposes a re-adhesion control algorithm which uses the maximum adhesive effort by instantaneous estimation of adhesion force using disturbance observer. Based on this estimated adhesive effort, the re-adhesion control is performed to obtain the maximum transfer of the tractive effort.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.115-120
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• 2008

In this study, effects of surface roughness on adhesive strength of heat-resistant adhesive RTV88 were examined. Sandblast was used to generate rough surfaces on aluminum adherends, and then tensile-shear tests of Al/RTV88 single lap joints were performed. The shear strength was shown to be affected by the surface roughness. Effective area, peel failure area, and cohesive failure area were introduced to explain the effects of surface roughness on the adhesive strength. An empirical relation for the failure force was proposed based on these parameters and verified by the test results.

• Journal of Welding and Joining
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• 제20권5호
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• pp.99-105
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• 2002

One of the important advantage of adhesive bonded joint can combine the different materials. The joint that bonded by structural adhesive bond must keep a large force and its strength is affected by some environmental factors such as temperature and submergence time in water. In order to advance the fatigue strength of adhesive bonded joint, mostly put a surface treatment on the surface. This study was researched the effect of air temperature, submergence time, submergence temperature and surface treatment on the fatigue strength. We found that submergence temperature has the most effect and low plasma treatment specimens have the most fatigue strength.

• 한국염색가공학회지
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• 제31권2호
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• pp.107-117
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• 2019

In case of pure rubber materials, the initial quality of the rubber materials would be excellent, however, the durability against external impact might be poor. In order to overcome the relatively low durability, textile cord could be employed with silicone rubber. We have studied the improvement of heat-resistant adhesion properties of silicone adhesives between silicone rubber and PET fibers by applying various conditions including dip solution recipe. The silicone rubber used was a platinum catalyst curing type and platinum catalyst type silicone adhesive was used as an adhesive to obtain an optimum adhesive force. Furthermore, the bonding mechanism between silicone and PET fiber was established.

• Advanced Composite Materials
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• 제17권2호
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• pp.101-110
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• 2008

Metal nanohoneycomb structures were fabricated by E-beam evaporation and a two-step anodization process in phosphoric acid. Their tribological properties of adhesion and friction were investigated by AFM in relation to the pore size of the nanohoneycomb structures. Variations of the adhesive force are not found with pore size, but formation of the pore greatly reduces the adhesive force compared to the absence of pore structure. The coefficient of friction increased nonlinearly with pore size, due to surface undulation around the pore. Tribological properties do not differ greatly between the original nanohoneycomb structure and the metal nanohoneycomb structure.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1580-1581
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• 2008

We investigated the effects of intermittent hydrostatic pressure with various duration of resting period on changes in calcium ($Ca^{2+}$) concentration and adhesive forces of cells on substrates. The quantitive adhesive forces of cells were measured under various resting periods. When the pressure applied to the cells, the concentration of $Ca^{2+}$ increased. Under intermittent hydrostatic pressure, the concentration of $Ca^{2+}$ was maintained under a resting period of 15 min, while it was not decreased with other resting periods of less than 15 min. With a resting period of 15 min, the magnitudes of adhesive forces were significantly increase. In addition, the adhesive forces were measured with and without $Ca^{2+}$ chelating agents to evaluate the effect of $Ca^{2+}$ on cell adhesiveness. When $Ca^{2+}$ ions were chelated, the adhesive forces dramatically decreased, even under intermittent hydrostatic pressure. We conclude that $Ca^{2+}$ plays an crucial role in modulating the adhesive forces of cells, and that the concentration of $Ca^{2+}$ can be increased by intermittent hydrostatic stimuli.