Static and dynamic contact angle measurements using a custom-made contact angle goniometer

Hanbyeol Pak,김정현 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.8

Contact angle is a physical quantity used to evaluate the interaction between a solid surface and a liquid. However, many research laboratories or educational institutions with budget constraints have limited access to a commercial contact-angle goniometer with a highresolution imaging system. In this study, we fabricated a custom-made contact angle goniometer with a smartphone and quantified the contact angles of water on various surfaces. We found that the receding contact angles on the surfaces were sensitive to the change in flow rates. The receding angle sharply decreases when the flow rate exceeds 50 μl/min, indicating that accurate flow control is required in contact angle measurements. The dynamic contact angles could also be quantified by the developed goniometer in an extremely low-capillary number regime. The dynamic advancing and receding contact angles on tested surfaces followed the molecular-kinetic theory.

Contact angle control of sessile drops on a tensioned web

Park, Janghoon,Kim, Dongguk,Lee, Changwoo Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.437 No.-

<P><B>Abstract</B></P> <P>In this study, the influence of the change of tension applied to flexible and thin web substrate on the contact angle of sessile drop in roll-to-roll system was investigated. Graphene oxide and deionized water solutions were used in the experiments. Tension was changed to 29, 49, and 69 N, and the casting distance of the micropipette and the material was set to 10, 20, and 40 mm, and the droplet volume was set to 10, 20, and 30 μL, respectively. Statistical analysis of three variables and analysis of the variance methodology showed that the casting distance was most significant for the contact angle change, and the most interesting tension variable was also affected. The change in tension caused the maximum contact angle to change by 5.5°. The tension was not uniform in the width direction. When the droplet was applied in the same direction in the width direction, it was confirmed that the tension unevenness had great influence on the contact angle up to 11°. Finally, the casting distance, which has a large effect on the contact angle, was calibrated in the width direction to reduce the width direction contact angle deviation to 1%. This study can be applied to fine patterning research using continuous inkjet printing and aerosol jet printing, which are roll-to-roll processes based on droplet handling.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The droplet contact angle can be varied by web tension. </LI> <LI> The lateral web tension difference has a significant impact on the contact angle. </LI> <LI> The contact angle in the width direction can be calibrated by the casting distance. </LI> </UL> </P>

복합재료의 계면특성 평가를 위한 접촉각 방법의 정확도 비교

권동준,김종현,박종만 한국접착및계면학회 2022 접착 및 계면 Vol.23 No.3

To analyze the interfacial property between the fiber and the matrix, work of adhesion was used generally that was calculated by surface energies. In this paper, it was determined what types of contact angle measurement methods were more accurate between static and dynamic contact angle measurements. 4 types of glass fiber and epoxy resin were used each other to measure the contact angle. The contact angle was measured using two types, static and dynamic contact angle methods, and work of adhesion, Wa was calculated to compare interfacial properties. The interfacial property was evaluated using microdroplet pull-out test. Generally, the interfacial property was proportional to work of adhesion. In the case of static contact angle, however, work of adhesion was not consistent with interfacial property. It is because that dynamic contact angle measurement comparing to static contact angle could delete the error due to microdroplet size to minimize the surface area as well as the meniscus measuring error.

탄성 고무인상재의 접촉각이 작업모형 표면에 미치는 영향

김주원 한국치위생과학회 2010 치위생과학회지 Vol.10 No.3

This study was begun to search effect of contact angles of elastic rubber impression materials on the surface of working cast. Of elastic rubber impression materials with a Type III consistency, such as polysulfide, polyether and addition silicone, we selected one and then measured the contact angle after dripping a distilled water 3.3ml. Then, after pouring a dental anhydrite in three types of impression materials, we prepared a working cast and then examined its surface. Contact angle was measured using a full automatic contact angle measuring system (DM-700, KYOWA, Japan),and the surface of working cast was observed using a field emission scanning electron microscope (JSM-6700F, JEOL Ltd., JAPAN). The following results were obtained: 1) Mean±SD (SD: standard deviation) of the initial contact angles were 91.3±20.5o in the addition silicone materials, 90.0±2.2o in the polyethers and 101.5±2.3o in the polysulfides. These results indicate that mean values were similar but standard deviations of the three materials showed a great discrepancy. 2) As the time elapsed, addition silicone materials were found to have a contact angle decreased abruptly as compared with the remaining two types. That is, the initial contact angle was 91.3o and it was abruptly decreased to 29.4o after 25seconds. 3) In the polyethers, the initial contact angle was 101.5o and it was decreased to 90.7o after 25 seconds. In the polysulfides, however, the initial contact angle was 90.0o and it was 84.2o after 25 seconds. This showed almost no changes in the initial contact angles. Moreover, its magnitude was greater than that seen in additional silicones. 4) There were significant differences in the contact angles between the three types of elastic rubber impression materials as the time elapsed (p<0.001). On an observation on the surface of working cast, addition silicone materials were found to have the most dense surface. This was followed by polysulfides and polyethers in a descending order.

포비돈 및 히알루론산염을 포함한 인공누액에 대한 하이드로젤 콘택트렌즈의 물성 변화 비교

조선아,성아영 대한시과학회 2013 대한시과학회지 Vol.15 No.3

Purpose: The impacts of artificial tear that is a common material for the treatment of dry eye including povidone and hyaluronic acid on the hydrogel contact lens were analyzed in various conditions. Methods: The cross-linking agent, EGDMA(ethylene glycol dimethacrylate) and HEMA (2-hydroxyethyl methacrylate) were determined to be used as the basic combination to produce a soft hydrogel contact lens. Also, 20% each of NVP (n-vinyl-2-pyrrolidone) and MMA (methyl methacrylate) were added to this combination for classification of water content. The copolymerized contact lenses were stored in artificial tear for 3, 5, 10 min. and 1, 2, 72hrs. respectively. Also, the physical properties such as water content and contact angel of produced contact lenses were measured. Results: The measurement of the physical properties of the Ref. sample for povidone showed that water content and contact angle were in the range of 27.22~48.13% and 70.48~41.43°, respectively. Also, the measurement of Ref. sample for hyaluronic acid showed that water content and contact angle were in the range of 26.42~48.42% and 70.21~44.66° respectively. In addition, the measurement of physical property after soaking into artificial tear containing povidone, the water content and contact angle were in the range of 26.10~47.90% and 43.54~81.23° respectively. Also, in case of the measurement of sample soaked in hyaluronic acid, the water content and contact angle were in the range of 24.89~48.35% and 38.56~68.58°, respectively. In case of povidone, the changes of the physical property with soaking time showed decrease of water content and increase of contact angle. For hyaluronic acid, the measurement showed the decrease of water content and contact angle. Conclusions: Artificial tear including povidone and hyaluronic acid influenced on water content and contact angle of a hydrogel contact lenses. 목 적: 안구건조증의 일반적인 치료제로 사용되는 포비돈과 히알루론산염이 포함된 인공누액이 하이드로젤 콘택트렌즈에 미치는 영향을 다양한 조건에서 분석 하였다. 방 법: 본 연구에 사용된 친수성 하이드로젤 콘택트렌즈의 제조를 위해 교차결합제인 EGDMA(ethylene glycol dimethacrylate)와 HEMA(2-hydroxyethyl methacrylate)를 기본 조합으로 사용하여 참조물을 제조하였다. 또한 20%의 NVP(n-vinyl-2-pyrrolidone)와 MMA (methyl methacrylate)를 첨가하여 함수율별로 다양하게 중합하였다. 공중합된 콘택트렌즈를 인공누액에 각각 1시간, 2시간 그리고 72시간 침지시킨 후 제조된 렌즈의 함수율과 접촉각을 측정하였다. 결 과: 제조된 콘택트렌즈의 기본 물성을 측정한 결과, 포비돈 참조물의 경우, 함수율 27.22~48.13%, 접촉각 70.48~41.43°의 범위로, 히알루론산염 참조물의 경우, 함수율 26.42~48.42%, 접촉각 70.21~ 44.66°의 범위로 나타났다. 또한 제조된 콘택트렌즈를 인공누액에 침지시킨 후 측정한 물리적 특성은 포비돈을 포함한 인공누액의 경우, 함수율 26.10~47.90%, 접촉각 43.54~81.23°의 범위로, 히알루론산염을 포함한 인공누액의 경우, 함수율 24.89~48.35%, 접촉각 38.56~68.58°의 범위로 나타났다. 침지 시간에 따른 물성 변화는 포비돈의 경우 함수율의 감소 및 접촉각의 증가, 히알루론산염의 경우 함수율 및 접촉각의 감소를 나타내었다. 결 론: 포비돈과 히알루론산염을 포함한 인공누액은 친수성 하이드로젤 콘택트렌즈의 함수율과 접촉각에 영향을 주는 것으로 나타났다.

CO₂ 가스의 존재 여부와 용액의 pH가 Silica/Pb(II) 용액 계면에서 Silica 표면의 특성에 미치는 영향

이상은,Lee, Sang-Eun 한국토양비료학회 2003 한국토양비료학회지 Vol.36 No.5

$CO_2$ 가스 존재여부와 pH가 Pb(II)와 sodium dodecyl sulfonate(SDS, $C_{12}H_{25}SO_3Na$) 흡착에 따른 silca 표면의 특성 변화에 미치는 영향을 contact angle 과 AFM을 이용한 힘 측정을 통하여 살펴보았다. 대기와 접촉하여 $CO_2$가 용해되는 조건에서 Pb와 SDS가 $10^{-4}M$ 씩 들어 있는 혼합용액을 처리하였을 때, fused silica 표면의 contact angle은 $PbCO_3$의 침전 때문에 최대 $46^{\circ}$로 낮았다. 반면에 $N_2$ 개스를 불어넣는 $CO_2$ 부재조건에서는 $PbCO_3$의 침전이 없었기 때문에 contact angle이 최대 $90^{\circ}$로 크게 증가되었다. $CO_2$ 부재조건에서 pH에 따른 contact angle과 AFM에서 측정한 점착력($F_{ad}$) 변화 양상은 $PbOH^+$ 화학종 분포와 유사하였으므로, Pb(II)의 silica 표면 흡착형태는 $PbOH^+$ 로 판단되었다. 한편 contact angle 과 AFM 측정결과 모두 Pb 단독처리에서 소수성을 발현하였다. 이 결과는 현재까지의 알려진 이론으로 설명할 수 없었으며 이를 위하여 원자수준에서의 심도 깊은 연구가 필요하다고 판단되었다. Effects of the existence of $CO_2$ gas and pH on the silica surface characteristics at silica/Pb(II) and sodium dodecyl sulfonate (SDS, $C_{12}H_{25}SO_3Na$) solution interface were studied. The hydrophobic characteristics of silica surface was delineated by contact angle measurement and surface force measurement using atomic force microscopy (AFM). In $CO_2$ free condition provided by purging $N_2$ gas, the contact angle of fused silica surface in $10^{-4}M$ Pb(II) and SDS solution increased greatly up to $90^{\circ}$ compared with $40^{\circ}$ in atmospheric condition. It was due to the precipitation of $PbCO_3$ in atmospheric condition. In $CO_2$ free condition the change of contact angle and adhesion force ($F_{ad}$) in AFM, affected by pH change, was similar to the distribution of $PbOH^+$ ion in speciation diagram corresponding to $10^{-4}M$ total Pb(II). Therefore, it was convinced that the $PbOH^+$ ion among Pb(II) species would be the main adsorbing type on silica surface. Both of contact angle measurement and surface force measurement using AFM showed that the Pb only treatment made the silica surface hydrophobic. However, it could not be explained theoretically by current knowledge, and required further study in atomic level to solve the problem.

포비돈 및 히알루론산염을 포함한 인공누액에 대한 하이드로젤 콘택트렌즈의 물성 변화 비교

조선아,성아영 대한시과학회 2013 대한시과학회지 Vol.15 No.3

목 적: 안구건조증의 일반적인 치료제로 사용되는 포비돈과 히알루론산염이 포함된 인공누액이 하이드로 젤 콘택트렌즈에 미치는 영향을 다양한 조건에서 분석 하였다. 방 법: 본 연구에 사용된 친수성 하이드로젤 콘택트렌즈의 제조를 위해 교차결합제인 EGDMA(ethylene glycol dimethacrylate)와 HEMA(2-hydroxyethyl methacrylate)를 기본 조합으로 사용하여 참조물을 제조하였다. 또한 20%의 NVP(n-vinyl-2-pyrrolidone)와 MMA (methyl methacrylate)를 첨가하여 함수율 별로 다양하게 중합하였다. 공중합된 콘택트렌즈를 인공누액에 각각 1시간, 2시간 그리고 72시간 침지시킨후 제조된 렌즈의 함수율과 접촉각을 측정하였다. 결 과: 제조된 콘택트렌즈의 기본 물성을 측정한 결과, 포비돈 참조물의 경우, 함수율 27.22~48.13%, 접촉각 70.48~41.43°의 범위로, 히알루론산염 참조물의 경우, 함수율 26.42~48.42%, 접촉각 70.21~44.66°의 범위로 나타났다. 또한 제조된 콘택트렌즈를 인공누액에 침지시킨 후 측정한 물리적 특성은 포비돈을 포함한 인공누액의 경우, 함수율 26.10~47.90%, 접촉각 43.54~81.23°의 범위로, 히알루론산염을 포함한 인공누액의 경우, 함수율 24.89~48.35%, 접촉각 38.56~68.58°의 범위로 나타났다. 침지 시간에 따른 물성 변화는 포비돈의 경우 함수율의 감소 및 접촉각의 증가, 히알루론산염의 경우 함수율 및 접촉각의 감소를 나타내었다. 결 론: 포비돈과 히알루론산염을 포함한 인공누액은 친수성 하이드로젤 콘택트렌즈의 함수율과 접촉각에 영향을 주는 것으로 나타났다. Purpose: The impacts of artificial tear that is a common material for the treatment of dry eye including povidone and hyaluronic acid on the hydrogel contact lens were analyzed in various conditions. Methods: The cross-linking agent, EGDMA(ethylene glycol dimethacrylate) and HEMA (2-hydroxyethyl methacrylate) were determined to be used as the basic combination to produce a soft hydrogel contact lens. Also, 20% each of NVP (n-vinyl-2-pyrrolidone) and MMA (methyl methacrylate) were added to this combination for classification of water content. The copolymerized contact lenses were stored in artificial tear for 3, 5, 10 min. and 1, 2, 72hrs. respectively. Also, the physical properties such as water content and contact angel of produced contact lenses were measured. Results: The measurement of the physical properties of the Ref. sample for povidone showed that water content and contact angle were in the range of 27.22~48.13% and 70.48~41.43°, respectively. Also, the measurement of Ref. sample for hyaluronic acid showed that water content and contact angle were in the range of 26.42~48.42% and 70.21~44.66° respectively. In addition, the measurement of physical property after soaking into artificial tear containing povidone, the water content and contact angle were in the range of 26.10~47.90% and 43.54~81.23° respectively. Also, in case of the measurement of sample soaked in hyaluronic acid, the water content and contact angle were in the range of 24.89~48.35% and 38.56~68.58°, respectively. In case of povidone, the changes of the physical property with soaking time showed decrease of water content and increase of contact angle. For hyaluronic acid, the measurement showed the decrease of water content and contact angle. Conclusions: Artificial tear including povidone and hyaluronic acid influenced on water content and contact angle of a hydrogel contact lenses.

A molecular dynamics study of Wenzel state water droplets on anisotropic surfaces

Ambrosia, Matthew Stanley,Ha, Man Yeong Elsevier 2018 Computers & fluids Vol.163 No.-

<P><B>Abstract</B></P> <P>Some phenomena at the nanoscale are different from those at the macroscale. One of these phenomena is represented by the Wenzel equation which predicts a droplet's contact angle on a textured surface under certain conditions at the macroscale. However, at the nanoscale a different trend is observed in some cases. The Wenzel equation predicts contact angles to decrease as the surface roughness factor increases for droplets with a Young contact angle under 90°. However, for these cases at the nanoscale contact angles become larger as the surface roughness factor increases. In this study molecular dynamic simulations were run to investigate this phenomenon. Five surface energies and five surface roughness factors were considered for a graphite-like surface. Contact angles of nanoscale water droplets on an anisotropic surface with nanoscale texture are plotted and an equation related to the surface roughness factor and Young contact angle that fits the trend is proposed.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Water droplets in the Wenzel state have larger contact angles at the nanoscale than the Wenzel equation predicts. </LI> <LI> At the nanoscale water droplets have a larger contact angles when the graphite layers are oriented vertically than horizontally. </LI> <LI> Water droplets at the nanoscale generally increase as the surface roughness factor increases regardless of the Young contact angle. </LI> <LI> A logarithmic equation dependent on the surface roughness factor models contact angles on pillared graphite at the nanoscale. </LI> </UL> </P>

원형 핀과 구멍의 접촉에서 헤르츠 응력장 가정을 위한 조건

김형규(Hyung-Kyu Kim) 한국트라이볼로지학회 2015 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.31 No.5

This paper focuses on the conformal contact problem. A typical example of conformal contact is the contact between a pin and hole. In particular, this paper focuses on the condition for assuming a contact stress field to be a Hertzian pressure profile by using well-known classical solutions associated with Hertzian contact. Persson first developed the conformal contact analysis method around half a century ago, but there have been no significant improvements since then. The present research also adopted this method, but developed new solutions from the viewpoint of application to structural design. The analysis began with a comparison between Persson° Øs conformal contact stress and the Hertzian stress fields. The next step was to check the differences in the normalized stress values of both. This study used the tolerance for the difference in the peak stresses of Persson° Øs solution and the Hertz solution to validate the Hertzian assumption. This gave the range for the difference in radii of the pin and hole when the contact force and mechanical properties of the material are specified. The results showed that, at a tolerance of 5%, the Hertzian assumption is valid if half of the contact angle is less than 35°ý. In addition, the Hertzian assumption holds even for a relatively long contact length, in contrast to the general incomplete contact problem. This paper discusses these results along with other aspects of the application to the design.

Analysis of the Drag Angle in Cone Drum False Twisting Mechanism

Lee, Choon Gil 한국의류산업학회 2001 한국의류산업학회지 Vol.3 No.5

The newly developed cone drum twister is one of the outer surface contacting friction-twisting devices in false-twist texturing. An investigation of the drag angle for the newly developed cone drum twister texturing mechanism is reported. An analysis is given from which equations can be derived that relate to the conical angle of cone drum, wrapping angle, drag angle, and yarn helix angle. Theoretical values of drag angle are calculated and discussed. It is shown that, as the helix angle and the projected wrapping angle increases, the drag angle also increases slowly until the helix angle of 40˚but after the helix angle of 40˚the drag angle increases rapidly. Furthermore the higher the projected wrapping angle and conical angle, the higher the drag angle of friction surface.