Relationship between contact angle of liquid droplet and light beam position in optoelectrowetting

2007 ◽  
Vol 140 (1) ◽  
pp. 123-130 ◽  
Author(s):  
N. Inui
Keyword(s):  
Contact Angle ◽  
Light Beam ◽  
Liquid Droplet ◽  
Beam Position

scholarly journals Molecular Dynamics Simulation of Wetting Behavior: Contact Angle Dependency on Water Potential Models

2021 ◽  
Vol 1 (1) ◽  
pp. 10
Author(s):  
Lukman Hakim ◽  
Irsandi Dwi Oka Kurniawan ◽  
Ellya Indahyanti ◽  
Irwansyah Putra Pradana
Keyword(s):  
Molecular Dynamics ◽  
Contact Angle ◽  
Liquid Droplet ◽  
Center Of Mass ◽  
Contact Angles ◽  
Surface Wettability ◽  
Dynamics Simulation ◽  
Potential Models ◽  
Surface Hydrophilicity ◽  
Dynamics Simulations

The underlying principle of surface wettability has obtained great attentions for the development of novel functional surfaces. Molecular dynamics simulations has been widely utilized to obtain molecular-level details of surface wettability that is commonly quantified in term of contact angle of a liquid droplet on the surface. In this work, the sensitivity of contact angle calculation at various degrees of surface hydrophilicity to the adopted potential models of water: SPC/E, TIP4P, and TIP5P, is investigated. The simulation cell consists of a water droplet on a structureless surface whose hydrophilicity is modified by introducing a scaling factor to the water-surface interaction parameter. The simulation shows that the differences in contact angle described by the potential models are systematic and become more visible with the increase of the surface hydrophilicity. An alternative method to compute a contact angle based on the height of center-of-mass of the droplet is also evaluated, and the resulting contact angles are generally larger than those determined from the liquid-gas interfacial line.

Determining Micro Droplet Profile Using Internal Reflection Interference Fringes

2020 ◽  
Author(s):  
Iltai Isaac Kim ◽  
Yang Li ◽  
Jaesung Park
Keyword(s):  
Contact Angle ◽  
Liquid Droplet ◽  
Surface Profile ◽  
Morphological Features ◽  
Internal Reflection ◽  
Sessile Droplet ◽  
Spherical Droplet ◽  
Interference Fringes ◽  
The One ◽  
Air Liquid Interface

Abstract We introduce an optical diagnostics to determine the morphological features of liquid droplet such as the thickness, the contact angle, and the dual profile using internal reflection interferometry. A coherent laser beam is internally reflected on the air/liquid interface of a sessile droplet placed on a prism-based substrate to produce an interference fringe on a screen far from the substrate. The reflected laser rays consist of the reflection from the center spherical droplet profile and the one from the lower hyperbola-like droplet profile. The reflected rays are interfered each other to form the interference fringes. Ray tracing simulation is conducted using a custom-designed computer program. The simulation shows that the interfering rays reflected near the inflection point produce the outer-most fringes of the concentric interference pattern on the screen, and the reflected rays from the apex of the spherical profile and the contact line of the lower hyperbola-like profile construct the fringes at the center of the interference patterns. The simulated results are compared with the experimental observation to show a good agreement in the number and the location of the fringes and the radius of the outer-most-fringe where the number of the fringes is dependent on the droplet thickness and the radius of the fringe depends on the contact angle of the droplet. This result provides a new measurement technique to determine the morphological features of very small microdroplet such as the thickness (< a few micron thickness), the contact angle (< a few degree), and the dual-surface profile.

scholarly journals Slippery surface based on lubricant infused hierarchical silicon nanowire film

RSC Advances ◽  
2017 ◽  
Vol 7 (88) ◽  
pp. 55812-55818 ◽  
Author(s):  
Tian Hang ◽  
Hui-Jiuan Chen ◽  
Chengduan Yang ◽  
Shuai Xiao ◽  
Guishi Liu ◽  
...  
Keyword(s):  
Contact Angle ◽  
Liquid Droplet ◽  
Silicon Nanowire ◽  
Repellent Property ◽  
Si Nanowire ◽  
Slippery Surface

Slippery surface based on lubricant infused hierarchical Si nanowire films was developed, which provided low contact angle with liquid droplet, while possessing liquid repellent property upon slight tilting.

Ring-Shaped Sessile Droplet

2011 ◽  
Author(s):  
Svyatoslav S. Chugunov ◽  
Douglas L. Schulz ◽  
Iskander S. Akhatov
Keyword(s):  
Contact Angle ◽  
Liquid Droplet ◽  
Liquid Structure ◽  
Solid Substrate ◽  
Contact Angles ◽  
Equilibrium Contact Angle ◽  
Sessile Droplet ◽  
System Equilibrium ◽  
Energy Consideration ◽  
External Forces

It is recognized that small liquid droplet placed on the solid substrate forms equilibrium contact angle that can be obtained from well-known Young’s law. Previously, deviations from Young’s law were demonstrated for the droplets exposed to external fields (gravity, electric, etc) and for the droplets on non-homogeneous substrates. This work reveals that the Young’s equilibrium contact angle can be altered by geometrical reasons only. We consider a ring-shaped droplet on a solid substrate as a test structure for our discussion. We use the global energy consideration for analysis of system equilibrium for the case of freely deposited liquid with no external forces applied. The theoretical analysis shows that steady ring-shaped liquid structure on a solid substrate does exist with contact angles on both contact lines to be different from the Young’s equilibrium contact angle.

Wettability Analysis of Orthopaedic Materials Using Optical Contact Angle Methods

2006 ◽  
Vol 309-311 ◽  
pp. 1199-1202 ◽  
Author(s):  
Abraham Salehi ◽  
Stanley Tsai ◽  
Vivek Pawar ◽  
Jeff Sprague ◽  
Gordon Hunter ◽  
...  
Keyword(s):  
Contact Angle ◽  
Liquid Droplet ◽  
Sample Surface ◽  
Contact Angles ◽  
Radius Of Curvature ◽  
Oxide Ceramic ◽  
Optical Contact ◽  
Dlc Coating ◽  
Femoral Heads ◽  
Bearing Materials

The wettability behavior of orthopaedic materials influences the fluid film layer that affects both the friction and wear of the articulating surfaces in total joint arthroplasty. This study examined the wettability of various orthopaedic bearing materials such as alumina, zirconia, cobalt chrome (CoCr), and oxidized zirconium (OxZr). Diamond-like carbon (DLC) coating on CoCr was also examined. Additionally, the effect of radius of curvature was examined using OxZr femoral heads of various diameters. The contact angle of the liquid droplet on the surface of the material was measured using a optical contact angle method. Both water and bovine serum with 20 g/L protein concentration were used during testing, with a droplet size of 0.25 -L. The droplet was dispensed from an automated syringe and brought into contact with the sample surface. The contact angle was then measured by fitting polynomial curves to the sample surface and drop geometry. Ten individual drops were analyzed on each test component, with at least three test components for each material. There were no differences in contact angles with changing head size or when using serum compared to water. The alumina, OxZr, and zirconia femoral heads all exhibited a similar contact angle, while CoCr and DLC showed significantly greater contact angles. The smaller contact angles for the oxide ceramic surfaces indicate that they tend to be more wettable than the metals, which may help explain their lower friction and superior adhesive wear performance.

Effect of Materials’ Wettability on the Dynamic Behavior of Droplet Impact onto a Rough Solid Surface

2011 ◽  
Vol 320 ◽  
pp. 341-346
Author(s):  
Jing Cui ◽  
Yang Liu ◽  
Wei Zhong Li ◽  
Ning Zhang
Keyword(s):  
Contact Angle ◽  
Solid Surface ◽  
Liquid Droplet ◽  
Droplet Impact ◽  
Apparent Contact Angle ◽  
Bottom Surface ◽  
Roughness Elements ◽  
Hydrophilic Material ◽  
Boltzmann Method ◽  
Intrinsic Contact Angle

In this paper, the effect of material’s wettability on the droplet impact has been investigated by numerical apporach. The unsteady flow behaviors of liquid droplet impacting against the rough solid surface with different wettabilities have been simulated based on lattice Boltzmann method. The spreading and bounding characterisitcs of droplet have been discussed. For the hydrophilic material, the droplet will sink into the grooves among roughness bumps, and its apparent contact angle in steady stead will be smaller than its corresponding intrinsic contact angle; while for the hydrophilic material, droplet will flow into the grooves but suspend on the top of roughness elements without any contacting with the bottom surface, and the apparent contact angle is larger than its intrinsic contact angle.

Droplet Oscillation After Impact on a Solid Surface

2016 ◽  
Author(s):  
Yina Yao ◽  
Shuai Meng ◽  
Cong Li ◽  
Xiantao Chen ◽  
Rui Yang
Keyword(s):  
Contact Angle ◽  
Spray Deposition ◽  
Liquid Droplet ◽  
Droplet Diameter ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Oscillation Period ◽  
Droplet Spreading ◽  
Oscillation Phenomenon ◽  
The Impact

Droplet spreading and oscillation occur when a liquid droplet impacts on the solid surfaces. This process is vital in many industrial applications, such as ink-jet printing technologies, spray coating and agricultural spray deposition. However, the researches that have been done mainly focused on the spreading process, and less attention has been paid to the droplet oscillation phenomenon, which has influence on the solidification and evaporation process. Therefore, the study on droplet oscillation phenomenon after the impact is necessary and valuable. This paper aims at analyzing the droplet oscillation phenomenon using VOF method. Since the contact angle varies dramatically in the dynamic process, a dynamic contact angle model is introduced to improve the simulation accuracy. The dynamic contact angle model has been verified by comparing the numerical results with experimental and theoretical results. In order to study the factors that may influence the droplet oscillation period, different droplet diameters and impact velocities are utilized in this simulation. The results show that the oscillation period presents a positive relationship with droplet diameter. However, the impact velocity has no apparent influence on the oscillation period, which agrees well with the theoretical analysis.

Measurement of Liquid Film Thickness by a Fringe Method

2007 ◽  
Author(s):  
Akira Kariyasaki ◽  
Akiharu Ousaka ◽  
Yoshikazu Yamasaki ◽  
Masazumi Kagawa ◽  
Tohru Nagashima ◽  
...  
Keyword(s):  
Contact Angle ◽  
Liquid Film ◽  
Liquid Droplet ◽  
Estimation Error ◽  
Three Dimensional ◽  
Laser Speckle ◽  
Objective Lens ◽  
Laser Focus ◽  
Flow Phenomena ◽  
Small Contact Angle

A technique to measure the local thickness of a droplet or a liquid film by an interference fringe pattern that was formed by reflecting laser lights was developed and tested. Monochromatic epi-illumination through an objective lens of a microscope was provided by a 5mw-300mw laser and a filter to remove the noise caused by laser speckle. The incremental height difference of the liquid layer between neighboring maxima or minima of fringes was evaluated from the wavelength of the laser light and the refractive index of the liquid. Estimation error of a local inclination angle was discussed using ray tracing under parallel illumination approximation (Ku¨hner et al., 1996). Droplet profiles evaluated from the interferogram that were obtained by the present fringe method agreed well with those by Laser Focus Displacement Meter (LFD) (Fukamachi et al., 2003). Measurement was tried to make sure the usefulness of the present technique. It was made clear that a) contact angle of a liquid droplet could be obtained precisely and swiftly even in small size or small contact angle, and b) instantaneous three dimensional profile of a liquid film on a bubble moving in a micro-channel could be measured. The fringe method had sufficient potential to obtain more detailed information about three dimensional characteristics of liquid film in flow phenomena such as the generation, break down and growth of waves and the liquid film of a bubble at the beginning of movement.

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