Study of the Contact and the Evaporation Kinetics of a Thin Water Liquid Bridge between Two Hydrophobic Plates

Abstract

The evaporation of sessile water droplets on hydrophobic surfaces is a topic which led to numerous investigations. However, how does the liquid behave when the evaporation occurs between two of these particular substrates? The drying stage is governed by capillary phenomena which takes place in a confined space. In the field of material shaping, it is also possible that some regions of a green body exhibit hydrophobic properties. As part of a better understanding of the local mechanisms during drying, liquid bridges have been reproduced in an ideal case. Drying kinetics and parameters measurements from 303 to 343 K (relative humidity of 55%) of deionized water liquid bridges between two plates of hydrophobic substrates are presented. Experimental work was carried out using a specific device to create liquid bridges, coupled with image analysis within an adapted instrumented climatic chamber. While the volume and the exchange surface of liquid bridges decrease regularly throughout the process, contact angles constantly diminish and more significantly at the end. This is different from the evaporation between two hydrophilic plates. From these measurements, the change of curvature of the liquid bridges during evaporation is highlighted.

External Stefan and Internal Marangoni Thermo-Fluid Dynamics for Evaporating Capillary Bridges

“…For water droplets of 5 μL volume, the receding contact angle on the glass substrate is 20°. 43 Previous studies 13,16 have also evinced the instability characteristics of liquid bridges near this point. For the minimum volume instability, the liquid bridge ruptures from the neck region to form isolated droplets on both the top and bottom substrates.…”

“…In general, the contact line depins near this point, as reported in previous studies. 13,19 In the case of CCR mode of evaporation on hydrophilic surfaces (θ 0 = π/6, π/3), the liquid bridges may become unstable due to either minimum volume instability or depining instability. 20 The onset of depining may be characterized by specifying the receding contact angle of water.…”

“…Also, z denotes the vertical coordinate along the bridge axis and g is the gravitational acceleration. Equation reveals that the stability of a liquid bridge strongly depends upon the surface tension and the curvature of the liquid–vapor interface, which in turn are dictated by the wettability properties of the solid substrates. , Under low wetting conditions, when the depinning behavior of the contact line is frequent, a pressure disturbance, i.e., the disturbance generated at a constant pressure difference due to change in volume makes the capillary surfaces mostly unstable . Whereas for pinned contact lines the volume disturbance class stabilizes the liquid bridges most .…”

Effect of Hydrophobic Moieties on the Assembly of Silica Particles into Colloidal Crystals

“…The involvement of hydrophobic attraction between alkyl-modified particles during their assembly into CCs needs further confirmation because research on hydrophobic forces is limited to aqueous environments, and their magnitude in other solvents is still unexplored, particularly when there is chemical heterogeneity at the nanometer scale. Studies have shown that the presence of hydrophilic groups, immobilized on alkyl-modified surfaces or coexisting with hydrophobic domains in proteins, can modulate hydrophobic forces in different ways going from completely nullifying them to doubling their strength. ,, Moreover, during the wet stage and the late stage of nano dewetting (interparticle liquid bridges), the strength of capillary forces driven by the liquid–air interfacial tension between particles depends on the hydrophobicity of the particle surface because the contact angle of the solvent at the particle surface increases with its hydrophobicity. − Besides the effect on particle–particle interactions during evaporative assembly, particle surface hydrophobicity affects particle–hydrophilic substrate interactions. Only few studies have investigated similar asymmetric hydrophobic–hydrophilic surface interactions, all of which were measured in aqueous solutions. − Donaldson et al.…”

Characterization of interface properties of fluids by evaporation of a capillary bridge

“…The complex cases of the evaporation of a capillary bridge between one sphere and a surface [8] or between two spheres have been studied considering both evaporation kinetics [9] and bridge break-up [10]. Recently, the evaporation of a capillary bridge between two plates has been extensively explored in well-controlled conditions by Portuguez et al [11,12] for different wetting angles and air humidities. However, capillary forces of evaporating liquid bridges were not directly measured with their set-up.…”