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Showing papers on "Sessile drop technique published in 2011"


Journal ArticleDOI
TL;DR: In this paper, an infrared camera coupled with a microscopic lens giving a spatial resolution of 10 μm was used to observe the evaporation of sessile drops in infrared wavelengths, including ethanol, methanol and FC-72.

160 citations


Journal ArticleDOI
12 Oct 2011-Langmuir
TL;DR: This work uses a perturbation solution of the Bashforth-Adams equation to estimate the contact angles of sessile drops of water, ethylene glycol, and diiodomethane on an omniphobic surface using direct measurements of the maximum drop width and height to quantify the extent of gravity-induced sagging.
Abstract: Gravity-induced sagging can amplify variations in goniometric measurements of the contact angles of sessile drops on super-liquid-repellent surfaces. The very large value of the effective contact angle leads to increased optical noise in the drop profile near the solid–liquid free surface and the progressive failure of simple geometric approximations. We demonstrate a systematic approach to determining the effective contact angle of drops on super-repellent surfaces. We use a perturbation solution of the Bashforth–Adams equation to estimate the contact angles of sessile drops of water, ethylene glycol, and diiodomethane on an omniphobic surface using direct measurements of the maximum drop width and height. The results and analysis can be represented in terms of a dimensionless Bond number that depends on the maximum drop width and the capillary length of the liquid to quantify the extent of gravity-induced sagging. Finally, we illustrate the inherent sensitivity of goniometric contact angle measurement t...

142 citations


Journal ArticleDOI
22 Nov 2011-Langmuir
TL;DR: In this paper, the influence of the surface properties of substrates on the evaporation process is investigated, and it is shown that the dynamics of the evaporative rate are proportional to the dynamic of the wetting radius.
Abstract: In this article, we investigate the influence of the surface properties of substrates on the evaporation process. Using various nanocoatings, it is possible to modify the surface properties of substrates, such as the roughness and the surface energy, while maintaining constant thermal properties. Experi- ments are conducted under atmospheric conditions with five fluids (methanol, ethanol, propanol, toluene and water) and four coatings (PFC, PTFE, SiOC, and SiOx). The various combinations of these fluids and coatings allow for a wide range of drop evaporation properties to be studied: the dynamics of the triple line, the volatility of fluids, and a large range of wettabilities (from 17 to 135). The experimental data are in verygoodquantitative agreementwithexisting models ofquasi-steady, diffusion-drivenevaporation. Theexperimentalresultsshow that the dynamics of the evaporative rate are proportional to the dynamics of the wetting radius. Thus, the models succeed in describing the evaporative dynamics throughout the evaporation process regardless of the behavior of the triple line. Moreover, the use of various liquids reveals the validity of the models regardless of their volatility. The results also confirm the recent finding of a universal relation for the time evolution of the drop mass, independent of the drop size and initial contact angle. Finally, this study highlightstheseparateandcoupledrolesofthetriplelineandthewettabilityonthesessiledropevaporationprocess.Datarevealthat the more wet and pinned a drop, the shorter the evaporation time.

139 citations


Journal ArticleDOI
TL;DR: In this article, the authors investigated the range of applicability of a commonly used assumption for evaporation models of sessile drops, that the transport mechanism that controls the eva-oration is vapor diffusion.

128 citations


Journal ArticleDOI
TL;DR: In this paper, a series of injection experiments were performed in a five-spot glass micromodel after saturation with the heavy oil, and the results showed that the silica nanoparticles caused enhanced oil recovery during polymer flooding by a factor of 10%.
Abstract: It is well known that the oil recovery is affected by wettability of porous medium; however, the role of nanoparticles on wettability alteration of medium surfaces has remained a topic of debate in the literature. Furthermore, there is a little information of the way dispersed silica nanoparticles affect the oil recovery efficiency during polymer flooding, especially, when heavy oil is used. In this study, a series of injection experiments were performed in a five-spot glass micromodel after saturation with the heavy oil. Polyacrylamide solution and dispersed silica nanoparticles in polyacrylamide (DSNP) solution were used as injected fluids. The oil recovery as well as fluid distribution in the pores and throats was measured with analysis of continuously provided pictures during the experiments. Sessile drop method was used for measuring the contact angles of the glass surface at different states of wettability after coating by heavy oil, distilled water, dispersed silica nanoparticles in water (DSNW), polyacrylamide solution, and DSNP solution. The results showed that the silica nanoparticles caused enhanced oil recovery during polymer flooding by a factor of 10%. The distribution of DSNP solution during flooding tests in pores and throats showed strong water-wetting of the medium after flooding with this solution. The results of sessile drop experiments showed that coating with heavy oil, could make an oil-wet surface. Coating with distilled water and polymer solution could partially alter the wettability of surface to water-wet and coating with DSNW and DSNP could make a strongly water-wet surface.

120 citations


Journal ArticleDOI
TL;DR: In this article, the relationship between wettability and roughness has been studied on micro-roughened titanium surface after different cleaning procedures, and the interplay between surface roughness, the wetting behavior and in particular the (super)-hydrophilicity of high surface energy substrates, in non water miscible liquid environments.

108 citations


Journal ArticleDOI
TL;DR: In this paper, a simple and straightforward theoretical model to calculate accurately the mechanical and the thermodynamic properties of metal surfaces due to their important application in materials processes and in the understanding of a wide range of surface phenomena is presented.

103 citations


Journal ArticleDOI
TL;DR: In this article, a theoretical model for evaporation of pure liquid drops that includes Marangoni forces due to the thermal gradients produced by non-uniform evapsoration, and heat conduction effects in both liquid and solid phases is presented.
Abstract: We consider theoretically, computationally and experimentally spontaneous evaporation of water and isopropanol drops on smooth silicon wafers. In contrast to a number of previous works, the solid surface we consider is smooth and therefore the droplets' evolution proceeds without contact line pinning. We develop a theoretical model for evaporation of pure liquid drops that includes Marangoni forces due to the thermal gradients produced by non-uniform evaporation, and heat conduction effects in both liquid and solid phases. The key ingredient in this model is the evaporative flux. We consider two commonly used models: one based on the assumption that the evaporation is limited by the processes originating in the gas (vapour diffusion-limited evaporation), and the other one which assumes that the processes in the liquid are limiting. Our theoretical model allows for implementing evaporative fluxes resulting from both approaches. The required parameters are obtained from physical experiments. We then carry out fully nonlinear time-dependent simulations and compare the results with the experimental ones. Finally, we discuss how the simulation results can be used to predict which of the two theoretical models is appropriate for a particular physical experiment.

96 citations


Journal ArticleDOI
Qiaoli Lin1, Ping Shen1, Longlong Yang1, Shenbao Jin1, Qi-Chuan Jiang1 
TL;DR: In this paper, an improved sessile drop method was used for the wetting of titanium carbide (TiC 0.7 ) by liquid Al. The initial contact angles were 77-79°, almost independent of temperature, and the final equilibrium contact angles between 17° and 12°, slightly decreasing with increasing temperature.

78 citations


Journal ArticleDOI
05 May 2011-Langmuir
TL;DR: Analytical analysis indicates that contact line pinning represents frustration in surface free energy, and the equilibrium shape corresponds to a nondifferential minimum instead of a local minimum in the adhesion model.
Abstract: Contact angle hysteresis of a sessile drop on a substrate consists of continuous invasion of liquid phase with the advancing angle (θ(a)) and contact line pinning of liquid phase retreat until the receding angle (θ(r)) is reached. Receding pinning is generally attributed to localized defects that are more wettable than the rest of the surface. However, the defect model cannot explain advancing pinning of liquid phase invasion driven by a deflating bubble and continuous retreat of liquid phase driven by the inflating bubble. A simple thermodynamic model based on adhesion hysteresis is proposed to explain anomalous contact angle hysteresis of a captive bubble quantitatively. The adhesion model involves two solid–liquid interfacial tensions (γ(sl) > γ(sl)′). Young’s equation with γ(sl) gives the advancing angle θ(a) while that with γ(sl)′ due to surface rearrangement yields the receding angle θ(r). Our analytical analysis indicates that contact line pinning represents frustration in surface free energy, and the equilibrium shape corresponds to a nondifferential minimum instead of a local minimum. On the basis of our thermodynamic model, Surface Evolver simulations are performed to reproduce both advancing and receding behavior associated with a captive bubble on the acrylic glass.

75 citations


Journal ArticleDOI
TL;DR: In this article, the authors used Gibbsian surface thermodynamics to provide a physical understanding for the case where the droplet is thermodynamically favored to nucleate heterogeneously.
Abstract: When a vapor phase is in contact with a solid or nonvolatile fluid, under conditions where the vapor is thermodynamically metastable to condensation, a droplet may nucleate from the vapor either homogenously within the vapor phase, or heterogeneously at the solid or fluid substrate interface. The case where the droplet is thermodynamically favored to nucleate heterogeneously is the subject of this article. The heterogeneous nucleation of a sessile drop on a soft surface has been studied many times experimentally and theoretically. It has been observed experimentally that heterogeneous nucleation happens faster on a soft surface in comparison with a rigid surface. Here we use Gibbsian surface thermodynamics to provide a physical understanding for this observation. Due to the difficulties of considering soft-elastic surfaces, we demonstrate that by considering only the fluidity of a surface (i.e., by considering a fluid surface as an infinitely soft material and comparing a fluid surface with a rigid surface), thermodynamics will predict that heterogeneous nucleation is easier on soft surfaces compared with rigid surfaces. We first investigate the effect of contact angle on the barrier for heterogeneous nucleation on rigid substrates at constant vapor phase pressure. Then we find a lower energy barrier for heterogeneous nucleation at a fluid surface in comparison with heterogeneous nucleation at a rigid surface which explains the faster nucleation on soft surfaces compared with rigid surfaces. Finally we inspect the role of each contribution to the energy barrier.

Journal ArticleDOI
Longlong Yang1, Ping Shen1, Qiaoli Lin1, Feng Qiu1, Qi-Chuan Jiang1 
TL;DR: In this paper, the isotherm wetting and spreading behaviors of the molten Cu-Cr alloys with 0.5, 1.0 and 2.0% Cr on porous graphite substrates were investigated at 1373 K in a flowing Ar atmosphere using a modified sessile drop method.

Journal ArticleDOI
TL;DR: In this article, the wettability of molten aluminum on solid alumina substrate has been investigated by the sessile drop technique in a 10−8 bar vacuum or under argon atmosphere in the temperature range from 1273 K to 1673 K (1000 −8 K to 1400 K).
Abstract: The wettability of molten aluminum on solid alumina substrate has been investigated by the sessile drop technique in a 10−8 bar vacuum or under argon atmosphere in the temperature range from 1273 K to 1673 K (1000 °C to 1400 °C). It is shown that the reduction of oxide skin on molten aluminum is slow under normal pressures even with ultralow oxygen potential, but it is enhanced in high vacuum. To describe the wetting behavior of the Al-Al2O3 system at lower temperatures, a semiempirical calculation was employed. The calculated contact angle at 973 K (700 °C) is approximately 97 deg, which indicates that aluminum does not wet alumina at aluminum casting temperatures. Thus, a priming height is required for aluminum to infiltrate a filter. Wetting in the Al-Al2O3 system increases with temperature.

Journal ArticleDOI
TL;DR: In this article, an empirical model for drop evaporation is proposed to predict the temporal evolution of a sessile water drop volume when the drop evaporates on surfaces of various wettabilities widely adopted in microelectronic engineering.

Journal ArticleDOI
TL;DR: In this article, a combined analysis of the evolution of sessile drop parameters in contact with surface layer jointly with the data, obtained by electrochemical methods, gives the possibility to study the variation in the state of the surface due to the electrochemical reaction, associated with a corrosion process.

Journal ArticleDOI
TL;DR: In this paper, the wettability and interface thermal resistance (ITR) of a copper/graphite (Cu/Gr) system with an addition of chromium (Cr) was studied.

Journal ArticleDOI
28 Feb 2011-Langmuir
TL;DR: It was shown that the drop height is the most important experimental parameter affecting the accuracy of the surface tension measurement, and larger drop heights yield lower surface tension errors, and it is suggested that a minimum nondimensional drop height (drop height divided by capillary length) of 1.7 is required.
Abstract: Axisymmetric drop-shape analysis-no apex (ADSA-NA) is a recent drop-shape method that allows the simultaneous measurement of contact angles and surface tensions of drop configurations without an apex (i.e., a sessile drop with a capillary protruding into the drop). Although ADSA-NA significantly enhanced the accuracy of contact angle and surface tension measurements compared to that of original ADSA using a drop with an apex, it is still not as accurate as a surface tension measurement using a pendant drop suspended from a holder. In this article, the computational and experimental aspects of ADSA-NA were scrutinized to improve the accuracy of the simultaneous measurement of surface tensions and contact angles. It was found that the results are relatively insensitive to different optimization methods and edge detectors. The precision of contact angle measurement was enhanced by improving the location of the contact points of the liquid meniscus with the solid substrate to subpixel resolution. To optimize ...

Journal ArticleDOI
TL;DR: In this article, the authors measured the advancing and receding contact angles on six polymer surfaces (polystyrene, poly(ethylene terephthalate), poly(methyl methacrylate), polycarbonate, unplasticized poly(vinyl chloride), and poly(tetrafluoroethylene)) with water, ethylene glycol and formamide using the sessile drop and captive bubble methods.
Abstract: In order to characterize a solid surface, the commonly used approach is to measure the advancing and receding contact angles, i.e., the contact angle hysteresis. However, often an estimate of the average wettability of the solid–liquid system is required, which involves both the dry and wetted states of the surface. In this work, we measured advancing and receding contact angles on six polymer surfaces (polystyrene, poly(ethylene terephthalate), poly(methyl methacrylate), polycarbonate, unplasticized poly(vinyl chloride), and poly(tetrafluoroethylene)) with water, ethylene glycol and formamide using the sessile drop and captive bubble methods. We observed a general disagreement between these two methods in the advancing and receding contact angles values and the average contact angle determined separately by each method, although the contact angle hysteresis range mostly agreed. Surface mobility, swelling or liquid penetration might explain this behaviour. However, we found that the 'cross' averages of th...

Journal ArticleDOI
28 Jun 2011-Langmuir
TL;DR: A novel extension of this study by adding the effects of roughness to both methods for contact angle measurement found that the symmetry between the surface roughness problem and the chemical heterogeneity problem breaks down for drops and bubbles subjected to stick-slip effects.
Abstract: Quasi-static experiments using sessile drops and captive bubbles are the most employed methods for measuring advancing and receding contact angles on real surfaces. These observable contact angles are the most easily accessible and reproducible. However, some properties of practical surfaces induce certain phenomena that cause a built-in uncertainty in the estimation of advancing and receding contact angles. These phenomena are well known in surface thermodynamics as stick–slip phenomena. Following the work of Marmur (Marmur, A. Colloids Surf., A1998, 136, 209–215), where the stick–slip effects were studied with regard to sessile drops and captive bubbles on heterogeneous surfaces, we developed a novel extension of this study by adding the effects of roughness to both methods for contact angle measurement. We found that the symmetry between the surface roughness problem and the chemical heterogeneity problem breaks down for drops and bubbles subjected to stick–slip effects.

Journal ArticleDOI
TL;DR: In this paper, a simple model is proposed to describe temporal dynamics of both the shape of the drop and the volume fraction of the colloidal particles inside the drop, and the concentration dependence of the viscosity is taken into account.
Abstract: Using lubrication theory, drying processes of sessile colloidal droplets on a solid substrate are studied. A simple model is proposed to describe temporal dynamics of both the shape of the drop and the volume fraction of the colloidal particles inside the drop. The concentration dependence of the viscosity is taken into account. It is shown that the final shapes of the drops depend on both the initial volume fraction of the colloidal particles and the capillary number. The results of our simulations are in a reasonable agreement with the published experimental data. Computations for the drops of aqueous solution of human serum albumin are presented.

Journal ArticleDOI
TL;DR: In this article, the surface tension of Sn-3.0Ag-0.5Cu melt alloy was investigated at temperatures ranging from 503-K to 673-K on Cu, Ni, stainless steel and quartz, respectively.

Journal ArticleDOI
TL;DR: In this article, the authors consider the classical model of capillarity coupled with a rate independent dissipation mechanism due to frictional forces acting on the contact line, and prove the existence of solutions with prescribed initial conguration for the corresponding quasistatic evolution.
Abstract: We consider the classical model of capillarity coupled with a rate- independent dissipation mechanism due to frictional forces acting on the contact line, and prove the existence of solutions with prescribed initial conguration for the corresponding quasistatic evolution. We also discuss in detail some explicit solutions to show that the model does account for contact angle hysteresis, and to compare its predictions with experimental observations.

Journal ArticleDOI
TL;DR: In this article, the isotherm wetting of B4C, TiC and graphite substrates by molten Mg was studied in a flowing Ar atmosphere at 973-1173 K using an improved sessile drop method.

Journal ArticleDOI
TL;DR: In this article, the authors examined the contact angle hysteresis on the poly(ethylene terephthalate), PET, film was exposed to atmospheric pressure plasma under various plasma processing parameters.
Abstract: The poly(ethylene terephthalate), PET, film was exposed to atmospheric pressure plasma under various plasma processing parameters. The wettability of the PET film immediately after the exposure and after storage in air, which was determined by the sessile drop method, was strongly dependent on the plasma processing parameters. The contact angle hysteresis on the plasma-exposed PET film was examined by the Wilhelmy method. It was found that the hydrophobic recovery of the PET surface on storage after the plasma exposure was observed only for the advancing contact angle and that the receding angle remained almost the same. These experimental findings were explained on the basis of the calculation by Johnson and Dettre for the advancing and receding contact angles on model heterogeneous surfaces.

Journal ArticleDOI
TL;DR: In this paper, the authors explore the steady component of a sessile drop response to MHz order vibration, found to be dependent on its initial wettability, and reveal the competing effects between the radiation pressure exerted at the bulk air/water interface and the acoustic streaming force on the contact line.
Abstract: We explore the peculiar steady component of a sessile drop response to MHz order vibration, found to be dependent on its initial wettability. Placed on a vibrating hydrophobic substrate, the drop elongates vertically in the direction of the incident sound wave while remaining hydrophobic. In contrast, the drop is seen to spread on a slightly hydrophilic substrate. We elucidate this discrepancy by revealing the competing effects between the radiation pressure exerted at the bulk air/water interface and the acoustic streaming force on the contact line, revealing the critical role of the flow in the viscous boundary layer.

Journal ArticleDOI
TL;DR: In this paper, the effect of surface coverage, morphology (i.e., size and distribution) of the oxides on the reaction kinetics was examined, and the Zn wettability was determined by sessile drop contact angle measurement method and the Fe-Al interfacial layer was investigated by the use of a novel hot temperature spinning process.

Journal ArticleDOI
TL;DR: In this paper, the sessile drop technique was used to determine the contact wetting angle of Pd43Ni10Cu27P20, Pt57.5Cu14.7Ni5.3P22.5, Au49Ag5.5Pd2.3Cu26.9Si16.3, and Zr57Nb5Cu15.4Ni12.6Al10 bulk metallic glass forming alloys.
Abstract: Contact wetting angle of Pd43Ni10Cu27P20, Pt57.5Cu14.7Ni5.3P22.5, Au49Ag5.5Pd2.3Cu26.9Si16.3, and Zr57Nb5Cu15.4Ni12.6Al10 bulk metallic glass forming alloys have been determined on materials that are used in micro and nano fabrication. Employing the sessile drop technique at a temperature above the corresponding melting temperatures, three kinds of wetting behaviors are observed, spanning from θ ≈ 140°, over neutral wetting, θ ≈ 80°, to almost complete wetting, θ < 5°. The origin for complete wetting is the formation of an interface phase promoting wetting. Estimations of the contact wetting angles are presented for temperatures in the supercooled liquid region where micro and nano fabrication is typically carried out. Consequences of the observed wetting behaviors for nanoforming are discussed.

Journal ArticleDOI
TL;DR: In this article, the density and surface tension of liquid high-purity gallium and indium as a function of temperature were studied, and the sessile drop method was used to obtain these parameters.
Abstract: The density and surface tension of liquid high-purity gallium and indium as a function of temperature were studied. The sessile drop method was used to obtain these parameters. Experiments were carried out from the melting points to ∼1300 K in a high vacuum. The confidence error of the experiments was 0.5 and 1% for density and surface tension, respectively. The results of this research are compared with recommended reference data in the literature.

Journal ArticleDOI
02 Sep 2011-Langmuir
TL;DR: In this article, a hydrophobic microsphere is brought into contact with a small sessile water drop resting on a polytetrafluoroethylene (PTFE) surface.
Abstract: A new method for studying the dynamics of a sessile drop by atomic force microscopy (AFM) is demonstrated. A hydrophobic microsphere (radius, r 20–30 μm) is brought into contact with a small sessile water drop resting on a polytetrafluoroethylene (PTFE) surface. When the microsphere touches the liquid surface, the meniscus rises onto it because of capillary forces. Although the microsphere volume is 6 orders of magnitude smaller than the drop, it excites the normal resonance modes of the liquid interface. The sphere is pinned at the interface, whose small (<100 nm) oscillations are readily measured with AFM. Resonance oscillation frequencies were measured for drop volumes between 5 and 200 μL. The results for the two lowest normal modes are quantitatively consistent with continuum calculations for the natural frequency of hemispherical drops with no adjustable parameters. The method may enable sensitive measurements of volume, surface tension, and viscosity of small drops

Journal ArticleDOI
TL;DR: In this article, both static and dynamic contact angle measurements were used to examine the impact of thickness on the wetting of highly viscoelastic films, which are composed of a thermally stripped, solvent-borne acrylic polymer.
Abstract: Both static and dynamic contact angle measurements were used to examine the impact of thickness on the wetting of highly viscoelastic films. The films are composed of a thermally stripped, solvent-borne acrylic polymer. Results show that wetting behavior is strongly influenced for polymer coatings < 10 μm thick and plateaus above this. This dependency is attributed to the extent to which surface tension forces can induce deformation. For thinner coatings, surface deformation is limited, which allows propagation of the three-phase line, resulting in low contact angles for sessile drop measurements and little or no discernible pinning in dynamic wetting measurements. With increasing film thickness, residual deformations due to the pinning of the wetting line start to appear and become quite distinct at thicknesses corresponding to the plateau wetting behavior. The onset of pinning is accompanied by nonwetting contact angles for sessile drops and stick-and-break propagations in dynamic measurements. The obse...