Contact Angle Measurements

Hebbar, Raghavendra S.; Isloor, Arun M.; Ismail, Ahmad Fauzi

doi:10.1016/b978-0-444-63776-5.00012-7

Cited by 139 publications

(107 citation statements)

References 108 publications

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“…A hydrophobic surface enables a reagent to combine with a bioparticle or sample to form a droplet; the reagent can then be heated, cooled, and mixed by exerting a voltage on the droplet. The CA, which generally represents the wettability of a solid surface by a liquid, is defined by the angle between the liquid–vapor interface and solid–liquid interfaces [ 27 , 28 ]. In general, the shape of the liquid–vapor interface is determined by Young’s equation [ 29 ].…”

Section: Fundamental Theorymentioning

confidence: 99%

Surface Wettability and Electrical Resistance Analysis of Droplets on Indium-Tin-Oxide Glass Fabricated Using an Ultraviolet Laser System

Tsai

Hsu

et al. 2021

Micromachines

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Indium tin oxide (ITO) is widely used as a substrate for fabricating chips because of its optical transparency, favorable chemical stability, and high electrical conductivity. However, the wettability of ITO surface is neutral (the contact angle was approximately 90°) or hydrophilic. For reagent transporting and manipulation in biochip application, the surface wettability of ITO-based chips was modified to the hydrophobic or nearly hydrophobic surface to enable their use with droplets. Due to the above demand, this study used a 355-nm ultraviolet laser to fabricate a comb microstructure on ITO glass to modify the surface wettability characteristics. All of the fabrication patterns with various line width and pitch, depth, and surface roughness were employed. Subsequently, the contact angle (CA) of droplets on the ITO glass was analyzed to examine wettability and electrical performance by using the different voltages applied to the electrode. The proposed approach can succeed in the fabrication of a biochip with suitable comb-microstructure by using the optimal operating voltage and time functions for the catch droplets on ITO glass for precision medicine application. The experiment results indicated that the CA of droplets under a volume of 20 μL on flat ITO substrate was approximately 92° ± 2°; furthermore, due to its lowest surface roughness, the pattern line width and pitch of 110 μm exhibited a smaller CA variation and more favorable spherical droplet morphology, with a side and front view CA of 83° ± 1° and 78.5° ± 2.5°, respectively, while a laser scanning speed of 750 mm/s was employed. Other line width and pitch, as well as scanning speed parameters, increased the surface roughness and resulted in the surface becoming hydrophilic. In addition, to prevent droplet morphology collapse, the droplet’s electric operation voltage and driving time did not exceed 5 V and 20 s, respectively. With this method, the surface modification process can be employed to control the droplet’s CA by adjusting the line width and pitch and the laser scanning speed, especially in the neutral or nearly hydrophobic surface for droplet transporting. This enables the production of a microfluidic chip with a surface that is both light transmittance and has favorable electrical conductivity. In addition, the shape of the microfluidic chip can be directly designed and fabricated using a laser direct writing system on ITO glass, obviating the use of a mask and complicated production processes in biosensing and biomanipulation applications.

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Section: Fundamental Theorymentioning

confidence: 99%

Surface Wettability and Electrical Resistance Analysis of Droplets on Indium-Tin-Oxide Glass Fabricated Using an Ultraviolet Laser System

Tsai

Hsu

et al. 2021

Micromachines

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“…Finally, to evaluate the wettability of nylon coatings treated and untreated with plasma, the contact angle was measured [32][33] via the sessile drop (10 µl) method using water as a liquid. The images were recorded with a Micro View 1000x digital microscope and the contact angle values were obtained from the geometric analysis of the images of drops using the software Image J (version 1.52p).…”

Section: Coating Characterization Of Plasma Treatmentmentioning

confidence: 99%

Superficial Surface Treatment using Atmospheric Plasma on Recycled Nylon 6,6

Rodríguez

Vázquez‐Vélez

Martı́nez

et al. 2021

J. Nucl. Phy. Mat. Sci. Rad. A.

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Polymers currently represent materials that are cost-effective, while its recycled nature is significant in terms of environmental protection. However, the surface properties of polymers often do not meet the demands of wettability, adhesion, and friction, among others. Atmospheric plasma treatment on the surface of polymers improves its physical-chemistry properties. In this work, a recycled nylon coating was prepared by the spin coating technique and characterized by Fourier transform infrared spectroscopy and X-ray diffraction. This coating was treated by atmospheric plasma, and Raman spectroscopy was performed to analyze the signals related to different functional groups present in the coating surface after plasma treatment. The action of plasma on the surface morphology was observed by scanning electron microscopy. The contact angle results showed an improvement in surface wettability.

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“…The main drawbacks of these techniques is that the camera/telescope is tilted down (at 1-2 degrees from the horizon of the liquid sample), there is the need for a strong background light and there is an increase in the complexity of the approach to make the reading, due to the cylindrical shape and small size of the optical fiber used. In addition, particular skill is needed by the experimentalist to use the technique well and thus create reproducible and accurate results [18], [19]. However, from a review of the literature undertaken, it would appear that creating a sensor based on monitoring the CMH by using an optical fiber sensor emerging vertically from the air/liquid and from the liquid/liquid interfaces and then calculating the CA (all without the use of cameras), is innovative and this approach has not been investigated in any detail.…”

Section: Introductionmentioning

confidence: 99%

Monitoring of the Critical Meniscus of Very Low Liquid Volumes Using an Optical Fiber Sensor

et al. 2020

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A novel sensing system based on single mode optical fiber in reflective configuration has been developed to measure the critical meniscus height (CMH) of low volumes of liquids, which is then used to calculate the contact angle. The sensing system has been designed especially for very low volumes of liquids (e.g. bioliquids) and the work has demonstrated that measurements are possible with a minimum liquid volume of 5 µL. The sensing system is based on monitoring the spectral variation induced by the difference in the refractive index regions surrounding the fiber tip, at the air-liquid or liquid-liquid interfaces. From the experiments performed in water, (by immersing and extracting the fiber sensor in the liquid sample), it can be concluded that the CMH forming on the fiber decreases as the temperature increases. The change of temperature (in this experiment from 22 to 60 ℃) does not influence the CMH of the sample used in the evaluation (P3 mineral oil), giving an indication of its thermal stability. In addition, a fixed fiber was used to measure the variation in the liquid level when another fiber is immersed in the liquid. The error in the liquid level obtained in the work was small, at 0.34 ± 0.04 %. Such a sensor, allowing accurate measurements with very small quantities is especially useful where liquid sample volumes are limited e.g. biologically sourced liquids or specialized, expensive industrial material in the liquid phase.

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Contact Angle Measurements

Cited by 139 publications

References 108 publications

Surface Wettability and Electrical Resistance Analysis of Droplets on Indium-Tin-Oxide Glass Fabricated Using an Ultraviolet Laser System

Surface Wettability and Electrical Resistance Analysis of Droplets on Indium-Tin-Oxide Glass Fabricated Using an Ultraviolet Laser System

Superficial Surface Treatment using Atmospheric Plasma on Recycled Nylon 6,6

Monitoring of the Critical Meniscus of Very Low Liquid Volumes Using an Optical Fiber Sensor

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