Effect of Three-Phase Contact Line Topology on Dynamic Contact Angles on Heterogeneous Surfaces

Langmuir ◽  
2007 ◽  
Vol 23 (23) ◽  
pp. 11673-11676 ◽  
Author(s):  
Neeharika Anantharaju ◽  
Mahesh V. Panchagnula ◽  
Srikanth Vedantam ◽  
Sudhakar Neti ◽  
Svetlana Tatic-Lucic
Keyword(s):  
Contact Line ◽  
Dynamic Contact ◽  
Contact Angles ◽  
Heterogeneous Surfaces ◽  
Phase Contact ◽  
Three Phase

Direct Numerical Simulation of the Microscale Fluid Flow and Heat Transfer in the Three-Phase Contact Line Region During Evaporation

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Stefan Batzdorf ◽  
Tatiana Gambaryan-Roisman ◽  
Peter Stephan
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Contact Line ◽  
Thin Liquid Film ◽  
Contact Angles ◽  
Length Scale ◽  
Phase Contact ◽  
Flow And Heat Transfer ◽  
Three Phase

The heat and mass transfer close to the apparent three-phase contact line is of tremendous importance in many evaporation processes. Despite the extremely small dimensions of this region referred to as the microregion compared to the macroscopic length scale of a boiling process, a considerable fraction of heat can be transferred in this region. Due to its small characteristic length scale, physical phenomena are relevant in the microregion, which are completely negligible on the macroscopic scale, including the action of adhesion forces and the interfacial heat resistance. In the past, models have been developed taking these effects into account. However, so far these models are based on the assumption of one-dimensional (1D) heat conduction, and the flow within the thin liquid film forming the microregion near the apparent three-phase contact line is modeled utilizing the lubrication approximation. Hence, the application of existing models is restricted to small apparent contact angles. Moreover, the effects of surface structures or roughness are not included in these lubrication models. To overcome these limitations, a direct numerical simulation (DNS) of the liquid flow and heat transfer within the microregion is presented in this paper. The DNS is employed for validation of the existing lubrication model and for investigation of the influence of surface nanostructures on the apparent contact angle and in particular on the heat transfer within the microregion.

scholarly journals Sessile Droplets on Deformable Substrates

2018 ◽  
Vol 2 (4) ◽  
pp. 56
Author(s):  
Gulraiz Ahmed ◽  
Nektaria Koursari ◽  
Anna Trybala ◽  
Victor M. Starov
Keyword(s):  
Free Energy ◽  
Contact Line ◽  
Liquid Droplet ◽  
Excess Free Energy ◽  
Surface Elasticity ◽  
Contact Angles ◽  
Interfacial Behavior ◽  
Phase Contact ◽  
Technological Advances ◽  
Three Phase

Wetting of deformable substrates has gained significant interest over the past decade due to a multiplicity of industrial and biological applications. Technological advances in the area of interfacial science have given rise to the ability to capture interfacial behavior between a liquid droplet and an elastic substrate. Researchers have developed several theories to explain the interaction between the two phases and describe the process of wetting of deformable/soft substrates. A summary of the most recent advances on static wetting of deformable substrates is given in this review. It is demonstrated that action of surface forces (disjoining/conjoining pressure) near the apparent three-phase contact line should be considered. Any consideration of equilibrium droplets on deformable (as well as on non-deformable) substrates should be based on consideration of the excess free energy of the system. The equilibrium shapes of both droplet and deformable substrate should correspond to the minimum of the excess free energy of the system. It has never been considered in the literature that the obtained equilibrium profiles must satisfy sufficient Jacobi’s condition. If Jacobi’s condition is not satisfied, it is impossible to claim that the obtained solution really corresponds to equilibrium. In recently published studies, equilibrium of droplets on deformable substrates: (1) provided a solution that corresponds to the minimum of the excess free energy; and (2) the obtained solution satisfies the Jacobi’s condition. Based on consideration of disjoining/conjoining pressure acting in the vicinity of the apparent three-phase contact line, the hysteresis of contact angle of sessile droplets on deformable substrates is considered. It is shown that both advancing and receding contact angles decrease as the elasticity of the substrate is increased and the effect of disjoining/conjoining pressure is discussed. Fluid inside the droplet partially wets the deformable substrate. It is shown that just these forces coupled with the surface elasticity determine the deformation of the deformable substrates.

scholarly journals Dependency of Contact Angles on Three-Phase Contact Line: A Review

2021 ◽  
Vol 5 (1) ◽  
pp. 8
Author(s):  
H. Yildirim Erbil
Keyword(s):  
Contact Angle ◽  
Contact Line ◽  
Contact Angle Hysteresis ◽  
Contact Angles ◽  
Contact Radius ◽  
Phase Contact ◽  
Sessile Droplet ◽  
Line Energy ◽  
Three Phase ◽  
Tension Term

The wetted area of a sessile droplet on a practical substrate is limited by the three-phase contact line and characterized by contact angle, contact radius and drop height. Although, contact angles of droplets have been studied for more than two hundred years, there are still some unanswered questions. In the last two decades, it was experimentally proven that the advancing and receding contact angles, and the contact angle hysteresis of rough and chemically heterogeneous surfaces, are determined by interactions of the liquid and the solid at the three-phase contact line alone, and the interfacial area within the contact perimeter is irrelevant. However, confusion and misunderstanding still exist in this field regarding the relationship between contact angle and surface roughness and chemical heterogeneity. An extensive review was published on the debate for the dependence of apparent contact angles on drop contact area or the three-phase contact line in 2014. Following this old review, several new articles were published on the same subject. This article presents a review of the novel articles (mostly published after 2014 to present) on the dependency of contact angles on the three-phase contact line, after a short summary is given for this long-lasting debate. Recently, some improvements have been made; for example, a relationship of the apparent contact angle with the properties of the three-phase line was obtained by replacing the solid–vapor interfacial tension term, γSV, with a string tension term containing the edge energy, γSLV, and curvature of the triple contact line, km, terms. In addition, a novel Gibbsian thermodynamics composite system was developed for a liquid drop resting on a heterogeneous multiphase and also on a homogeneous rough solid substrate at equilibrium conditions, and this approach led to the same conclusions given above. Moreover, some publications on the line energy concept along the three-phase contact line, and on the “modified” Cassie equations were also examined in this review.

Contact Angle Measurement Through Atomic Force Microscopy

2011 ◽  
Author(s):  
Jiapeng Yu ◽  
Hao Wang
Keyword(s):  
Thin Film ◽  
Atomic Force Microscopy ◽  
Contact Line ◽  
Contact Angles ◽  
Angle Measurement ◽  
Optical Methods ◽  
Phase Contact ◽  
Force Microscopy ◽  
Atomic Force ◽  
Three Phase

Understanding the structure near the three-phase contact line is critical for a comprehensive understanding of the thin-film region when a liquid partially wets a planer substrate. Despite numerous theoretical and simulation efforts found literature, an accurate experiment is difficult to conduct because of how small its scale. In the present work the accurate geometry of the region near the three-phase contact line was obtained by directly scanning the thin-film region with atomic force microscopy (AFM). The contact angles were directly extracted from the results and compared with the ones measured from traditional optical methods.

The interaction of a moving fluid/fluid interface with a flat plate

1995 ◽  
Vol 296 ◽  
pp. 325-351 ◽  
Author(s):  
J. Billingham ◽  
A. C. King
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Flat Plate ◽  
Contact Line ◽  
Large Time ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Phase Contact ◽  
Three Phase ◽  
Time Problem

A well-known technique for metering a multiphase flow is to use small probes that utilize some measurement principle to detect the presence of different phases surrounding their tips. In almost all cases of relevance to the oil industry, the flow around such local probes is inviscid and driven by surface tension, with negligible gravitational effects. In order to study the features of the flow around a local probe when it meets a droplet, we analyse a model problem: the interaction of an infinite, initially straight, interface between two inviscid fluids, advected in an initially uniform flow towards a semi-infinite thin flat plate oriented at 90° to the interface. This has enabled us to gain some insight into the factors that control the motion of a contact line over a solid surface, for a range of physical parameter values.The potential flows in the two fluids are coupled nonlinearly at the interface, where surface tension is balanced by a pressure difference. In addition, a dynamic contact angle boundary condition is imposed at the three-phase contact line, which moves along the plate. In order to determine how the interface deforms in such a flow, we consider the small- and large-time asymptotic limits of the solution. The small-time and linearized large-time problems are solved analytically, using Mellin transforms, whilst the general large-time problem is solved numerically, using a boundary integral method.The form of the dynamic contact angle as a function of contact line velocity is the most important factor in determining how an interface deforms as it meets and moves over the plate. Depending on this, the three-phase contact line may, at one extreme, hang up on the leading edge of the plate or, at the other extreme, move rapidly along the surface of the plate. At large times, the solution asymptotes to an interface configuration where the contact line moves at the far-field velocity.

Test of the stability of a three-phase contact line with negative line tension

1999 ◽  
Vol 96 (9) ◽  
pp. 1335-1339 ◽  
Author(s):  
ALAN E. VAN GIESSEN, DIRK JAN BUKMAN, B.
Keyword(s):  
Contact Line ◽  
Line Tension ◽  
Phase Contact ◽  
Three Phase ◽  
The Stability
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