• 펄프종이기술
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• 제35권3호
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• pp.43-52
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• 2003

The new principle to measure a sizing degree by a contact angle was developed using an automatic determination of the 3-end point coordinates of the water droplet on a sheet, which could diminish the operator's bias during measurement. A constant amount of water was first placed on a sample sheet by a water dispenser, and then an image of the liquid droplet was captured by a digital camera and then transmitted to a computer. The program measuring for contact angle extracted a liquid contour by Gaussian function combined with a 8-direction chain code. The Euclidean equation was applied to the binary image of the liquid contour in order to measure the diameter of the contour. Finally, the contact angle of the liquid was calculated by using the diameter and the top coordinates. In addition, a surface free energy of the sample sheet and an elapsed time taken up to the complete absorption into the sheet were simultaneously measured with the contact angle.

• 한국정밀공학회지
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• 제30권4호
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• pp.414-420
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• 2013

We developed inkjet based measurement system for micro-droplet behavior on a substrate. By using the inkjet dispenser, a droplet, which is as small as few pico-liter in volume, can be jetted and the amount can be controlled. After jetting, the droplet image on the substrate is acquired from side view camera. Then, droplet profile is extracted to measure droplet volume, contact angle and evaporation characteristics. Also top view image of the droplet is acquired for better understanding of droplet shape. The previous contact angle measurement method has limitations since it mainly measures the ratio of height and contact diameter of droplet on a substrate. Unlike previous measurement system, our proposed method has advantages because various behavior of droplet on substrate can be effectively analyzed by extracting the droplet profile.

• 한국생산제조학회지
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• 제22권1호
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• pp.15-21
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• 2013

In this paper, a high-speed imaging and an image processing technique have been applied to detect the position of a meniscus as a function of time in the micro capillary flows. Two fluids with low and high viscosities, ethylene glycol and glycerin, were dropped into the entrance well of a circular capillary tube. The filling times of the meniscus in both cases of ethylene glycol and glycerin were compared with the theoretical models - Washburn model and its modified model based on Newman's dynamic contact angle equation. To evaluate the model coefficients of Newman's dynamic contact angle, time-varying contact angles under the capillary flows were measured using an image processing technique. By considering the dynamic contact angle, the estimated filling time from the modified Washburn model agrees well with the experimental data. Especially, for the lower-viscosity fluid, the consideration of dynamic contact angle is more significant than for the higher-viscosity fluid.

• Journal of Biosystems Engineering
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• 제35권4호
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• pp.257-261
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• 2010

Surface energy is the principal factor of anti-condensation. High surface energy appears hydrophilic itself and low surface energy represents hydrophobic itself. The contact angle is widely being used for measurement of surface energy of materials, evaluation of coating performances, measurement of wettability, and so on. However, the existing contact angle measuring system is so expensive for purchasing and complicated, so it takes a lot of time and money to use. This study was conducted to develop the algorithm for evaluating hydrophilic performance through measuring the contact angle of water droplet automatically, and fabricate relatively simple measuring system using a low-cost monochrome camera and image processing. A constant amount of water was firstly allocated on a slide by a micropipette, and then the image of water droplet was captured by monochrome digital camera and sent to a computer. The image was binarized and then reduced noises by labeling. Finally, the contact angle of water droplet was computed by using three points (left, right, and top coordinates), simple linear mathematics, and trigonometric function. The experimental results demonstrated the accuracy and reproducibility of the developed system showing less deviations and deviation ratio.

• 감성과학
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• 제5권3호
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• pp.67-74
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• 2002

Testing device was newly designed and built to measure the dynamic contact angle. The measurement was made using microscope interfaced with computerized image analysis system while the dynamic condition being controled using Instron. As specimens for the experiment, two different types of fibers, i.e., hydrophilic and hydrophobic, were prepared. In case of hydrophilic fiber, the increase of twist level gave the increase of contact angle. However, in hydrophobic yarn the increase of twist level gave the decrease of contact angle. When saline was used as a telling liquid, the increase of the concentration gave the increase of contact angle. The results rationalized clearly on the basis of known concepts could be used in designing fabric structure for the improvement of comport performance.

• 대한화학회지
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• 제57권4호
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• pp.432-438
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• 2013

기초 화학 실험에서 쉽게 만들고 운용할 수 있는 접촉각 측정기를 구성했다. LED 손전등과 시료 거치대, 디지털 카메라를 광학보드에 고정했고, 시료부는 양쪽에 구멍이 뚫린 암실 상자로 덮었다. 공개된 영상분석 프로그램(ImageJ)과 플러그인(Drop_analysis)을 이용해서 고체 표면 위에 형성된 액체 방울의 사진으로부터 접촉각을 측정했다. 구성된 측정기와 해석 프로그램을 이용해 여러 액체와 다양한 표면에서의 접촉각을 측정해 측정기의 성능을 확인했다. 측정된 $H_2O$와 $CH_2I_2$ 접촉각으로부터 결정된 고체의 표면에너지들은 알려진 값들과 대체로 일치하며 표면의 특성과 개질, 비극성 및 극성 기여도 등을 충실히 보여준다. 이 논문에 소개된 수제 접촉각 측정기와 측정법을 활용해 기초 화학을 배우는 학생들이 젖음성, 친수성, 발수성 등 표면 특성들과 분자 간 상호작용을 이해하고 관련된 힘의 평형, 광학, 수식의 전개 등을 경험할 수 있다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.662-665
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• 2008

We experimentally investigate the evaporation characteristics of water droplet on surfaces of various wettabilities in the range of contact angle from 30$^{circ}$ to 150$^{circ}$. When a liquid droplet on a solid surface evaporates, the contact angle generally decreases with time and the evaporation rate varies with the droplet geometry such as the contact angle and the radius of curvature. Experimental data on the contact angle as a function of the droplet volume obtained by digital image analysis techniques cannot be explained by the existing theories. By measuring the temporal evolutions of the droplet radius and contact angle, we find the qualitative difference between the evaporation patterns on the hydrophilic surfaces where the contact radius remains constant initially and those on the superhydrophobic surfaces where the contact angle remains constant. Also, the evaporation rate is observed to depend on the surface material although the currently available models assume that the rate is solely determined by the droplet geometry. Despite the fact that the theory to explain this dependence on the surface remains to be pursued by the future work, we give the empirical relations that can be used to predict the droplet volume evolution for each surface. It is expected that the present study will contribute to interpreting the effect of droplet geometry on the evaporation.

• 펄프종이기술
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• 제44권2호
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• pp.18-28
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• 2012

This study was to develop a novel automatic system for measuring St$\ddot{o}$ckigt sizing degree and contact angle at a time. The conventional methods to measure sizing degree had serious problems in obtaining significant differences according to different dosages of a sizing agent, and moreover they disclosed unique limitation due to liquid types used and tester's subjectivity. However, the newly developed system could get reproducible results through total automation of all procedures including liquid dropping, image acquisition and measurement of both St$\ddot{o}$ckigt sizing degree and contact angle. For the St$\ddot{o}$ckigt sizing test, the automatic system could measure sizing degree with more definite differences according to different dosage of AKD, compared to the conventional method. For the contact angle test, the automatic system showed a similar trend to the conventional method but had smaller contact angles due to distortion of an image focus by a sheet curl than the conventional testing machine. The problem from the image out of focus due to specimen curl will be overcome with adopting a new specimen holder for the future system.

• 한국컴퓨터정보학회:학술대회논문집
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• 한국컴퓨터정보학회 2016년도 제53차 동계학술대회논문집 24권1호
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• pp.251-252
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• 2016

접촉각을 이용한 표면에너지 측정방법은 부품소재분야를 비롯한 폴리머 화학제품 등에서 널리 사용되고 있다. 그중 측정할 대상의 고체 표면에 액체 방울을 떨어뜨리고 측면 접점 방향에 대한 영상을 촬영하여 고체 표면과 액체 방울이 이루고 있는 각도를 측정하는 방식을 가장 많이 사용하고 있다. 본 논문에서는 기존 접촉각 측정기의 배경과 액체 방울 사이의 명암 차를 이용하여 경계선을 찾는 Sessile-drop 영상처리 기법을 보완 및 개선하기 위하여 캐니 에지 검출 알고리즘을 적용하였다.

• 풍력에너지저널
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• 제14권4호
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• pp.43-49
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• 2023

We have studied biofouling in Korea's offshore wind farms by using image analysis through monitoring and surface energy analysis. To observe the biofouling characteristics, samples were fabricated using Micron extra 2 and PropOne, which have a self-polishing property, and Hempathane HS 55610, which is used in substructure coatings. The manufactured samples were installed at the bottom of a ladder in a substructure, and monitored for 10 months. The most biofouling occurred in the sample without the self-polishing property, and algae, barnacles and corallinales were observed. The surface energy analysis used the Owens-Wendt-Rabel and Kaelble (OWRK) model, which uses the contact angles of two standard fluids. As a result of calculating the surface energy using contact angle measurement, the sample without the self-polishing property showed the highest value. This result was consistent with the biofouling incidence observed through monitoring.