Contact Line Pinning on Microstructured Surfaces for Liquids in the Wenzel State

Langmuir ◽  
2010 ◽  
Vol 26 (2) ◽  
pp. 860-865 ◽  
Author(s):  
Pontus S. H. Forsberg ◽  
Craig Priest ◽  
Martin Brinkmann ◽  
Rossen Sedev ◽  
John Ralston
Keyword(s):  
Contact Line ◽  
Wenzel State ◽  
Microstructured Surfaces ◽  
Contact Line Pinning

Droplet spreading and absorption on rough, permeable substrates

2015 ◽  
Vol 784 ◽  
pp. 465-486 ◽  
Author(s):  
Leonardo Espín ◽  
Satish Kumar
Keyword(s):  
Surface Roughness ◽  
Contact Line ◽  
Nonlinear Evolution ◽  
Precursor Film ◽  
Radial Coordinate ◽  
Droplet Spreading ◽  
Liquid Spreading ◽  
Line Region ◽  
Influence Of Substrate ◽  
Contact Line Pinning

Wetting of permeable substrates by liquids is an important phenomenon in many natural and industrial processes. Substrate heterogeneities may significantly alter liquid spreading and interface shapes, which in turn may alter liquid imbibition. A new lubrication-theory-based model for droplet spreading on permeable substrates that incorporates surface roughness is developed in this work. The substrate is assumed to be saturated with liquid, and the contact-line region is described by including a precursor film and disjoining pressure. A novel boundary condition for liquid imbibition is applied that eliminates the need for a droplet-thickness-dependent substrate permeability that has been employed in previous models. A nonlinear evolution equation describing droplet height as a function of time and the radial coordinate is derived and then numerically solved to characterize the influence of substrate permeability and roughness on axisymmetric droplet spreading. Because it incorporates surface roughness, the new model is able to describe the contact-line pinning that has been observed in experiments but not captured by previous models.

Modeling of Transport During Droplet Deposition and Spreading on Smooth and Microstructured Superhydrophilic Surfaces

2016 ◽  
Author(s):  
Jordan P. Mizerak ◽  
Van P. Carey
Keyword(s):  
Contact Angle ◽  
Contact Angles ◽  
Ansys Fluent ◽  
Effective Contact ◽  
Microstructured Surfaces ◽  
Static Contact ◽  
Droplet Behavior ◽  
Contact Line Pinning ◽  
The Impact ◽  
Superhydrophilic Surfaces

The dynamic behavior of impinging water droplets is studied in the context of varying surface morphologies on smooth and microstructured superhydrophilic surfaces. The goal of this study is to evaluate the capability of contact angle wall adhesion models to accurately produce spreading phenomena seen on a variety of surface types. We analyze macroscale droplet behavior, specifically spreading extent and impinging regime, in situations of varying microscale wetting character and surface morphology. Axisymmetric, volume of fluid (VOF) simulations with static contact angle wall adhesion are conducted in ANSYS Fluent. Simulations are performed on water for low Weber numbers (We<20) on surfaces with features of length scale 5–10μm. Advanced microstructured surfaces consisting of unique wetting characteristics and lengths on each face are also tested. Results show that while the contact angle wall adhesion model shows fair agreement for conventional surfaces, the model underestimates spreading by over 60% for surfaces exhibiting estimated contact angles below approximately 0.5°. Microstructured surfaces adapt the wetting behavior of smooth surfaces with higher effective contact angles based on contact line pinning on morphology features. The propensity of the model to produce Wenzel and Cassie-Baxter states is linked to the spreading radius, introducing an interdependency of microscale wetting and macroscale spreading behavior. Conclusions describing the impact of results on evaporative cooling are also discussed.

Anomalous Contact Angle Hysteresis of a Captive Bubble: Advancing Contact Line Pinning

Langmuir ◽  
2011 ◽  
Vol 27 (11) ◽  
pp. 6890-6896 ◽  
Author(s):  
Siang-Jie Hong ◽  
Feng-Ming Chang ◽  
Tung-He Chou ◽  
Seong Heng Chan ◽  
Yu-Jane Sheng ◽  
...  
Keyword(s):  
Contact Angle ◽  
Contact Line ◽  
Contact Angle Hysteresis ◽  
Contact Line Pinning

Contact Line Pinning Effects Influence Determination of the Line Tension of Droplets Adsorbed on Substrates

2018 ◽  
Vol 122 (30) ◽  
pp. 17184-17189 ◽  
Author(s):  
Hongguang Zhang ◽  
Shan Chen ◽  
Zhenjiang Guo ◽  
Yawei Liu ◽  
Fernando Bresme ◽  
...  
Keyword(s):  
Contact Line ◽  
Line Tension ◽  
Contact Line Pinning

scholarly journals Contact Line Pinning Is Not Required for Nanobubble Stability on Copolymer Brushes

2018 ◽  
Vol 9 (15) ◽  
pp. 4239-4244 ◽  
Author(s):  
David S. Bull ◽  
Nathaniel Nelson ◽  
Danielle Konetski ◽  
Christopher N. Bowman ◽  
Daniel K. Schwartz ◽  
...  
Keyword(s):  
Contact Line ◽  
Copolymer Brushes ◽  
Contact Line Pinning

Contact Line Pinning and Depinning Prior to Rupture of an Evaporating Droplet in a Simulated Soil Pore

2020 ◽  
Author(s):  
Partha P. Chakraborty ◽  
Melanie M. Derby
Keyword(s):  
Contact Line ◽  
Pressure Difference ◽  
Liquid Droplet ◽  
Liquid Droplets ◽  
Water Contact ◽  
Marginal Rate ◽  
Vapor Interface ◽  
Hydrophobic Pore ◽  
Contact Line Pinning ◽  
Liquid Vapor

Abstract Altering soil wettability by inclusion of hydrophobicity could be an effective way to restrict evaporation from soil, thereby conserving water resources. In this study, 4-μL sessile water droplets were evaporated from an artificial soil millipore comprised of three glass (i.e. hydrophilic) and Teflon (i.e. hydrophobic) 2.38-mm-diameter beads. The distance between the beads were kept constant (i.e. center-to-center spacing of 3.1 mm). Experiments were conducted in an environmental chamber at an air temperature of 20°C and 30% and 75% relative humidity (RH). Evaporation rates were faster (i.e. ∼19 minutes and ∼49 minutes at 30% and 75% RH) from hydrophilic pores than the Teflon one (i.e. ∼24 minutes and ∼52 minutes at 30% and 75% RH) due in part to greater air-water contact area. Rupture of liquid droplets during evaporation was analyzed and predictions were made on rupture based on contact line pinning and depinning, projected surface area just before rupture, and pressure difference across liquid-vapor interface. It was observed that, in hydrophilic pore, the liquid droplet was pinned on one bead and the contact line on the other beads continuously decreased by deforming the liquid-vapor interface, though all three gas-liquid-solid contact lines decreased at a marginal rate in hydrophobic pore. For hydrophilic and hydrophobic pores, approximately 1.7 mm2 and 1.8–2 mm2 projected area of the droplet was predicted at 30% and 75% RH just before rupture occurs. Associated pressure difference responsible for rupture was estimated based on the deformation of curvature of liquid-vapor interface.

scholarly journals On-demand contact line pinning during droplet evaporation

2020 ◽  
Vol 312 ◽  
pp. 127983
Author(s):  
Wei Wang ◽  
Qi Wang ◽  
Kaidi Zhang ◽  
Xubo Wang ◽  
Antoine Riaud ◽  
...  
Keyword(s):  
Contact Line ◽  
Droplet Evaporation ◽  
On Demand ◽  
Contact Line Pinning
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