Showing papers on "Contact angle published in 1975"
TL;DR: In this article, the shape of the advancing liquid-air interface has been studied in a glass capillary over the range in which viscous and interfacial forces are the dominant factors controlling the system.
853 citations
TL;DR: It is concluded that on PHEMA gels water does not spread spontaneously, and large hysteresis has been observed in the advancing and receding contact angles, suggesting that this hydrogel surface is capable of changing its free energy through reorientation of the polymer side chains and chain segments depending on the nature of the adjacent phase.
Abstract: The wettability characteristics of the contact lens material, PHEMA, with respect to water have been determined by using the sessile drop, and the captive air bubble techniques of contact angle goniometry. It is concluded that on PHEMA gels water does not spread spontaneously. Large hysteresis has been observed in the advancing and receding contact angles. This suggests that this hydrogel surface is capable of changing its free energy through reorientation of the polymer side chains and chain segments depending on the nature of the adjacent phase. The water content of the gels does not appear to have an effect on water wettability in the hydration range investigated. The minor wettability differences among the various gels studied were most likely due to differences in surface structure and segmental mobility due to inherent variations in the method of preparation. Small but consistent differences were found between the contact angles measured by the captive bubble method and those obtained by the sessile drop method, the former values being higher. These differences may not be method-related artifacts and cannot be explained at the present time.
317 citations
TL;DR: In this article, the thermodynamics of an idealized rough surface is treated, using the geometry of a vertical plate partially immersed in a liquid, and gravity is included explicitly in the theory.
263 citations
237 citations
TL;DR: In this paper, the problem of the definition of the film thickness and its influence on the other thermodynamic quantities is discussed and a detailed analysis of the contact angle between the film and the meniscus is presented.
Abstract: The problem of the definition of the film thickness and its influence on the other thermodynamic quantities is discussed It is shown that at given physical state of the system, the film thickness can have various values depending on the way it has been defined A detailed analysis of the contact angle between the film and the meniscus is presented and is shown that the value of this angle depends on the definition of the film thickness If the thickness is assumed zero, the contact angle proves to be directly related to the film tension This yields a possibility for the film tension to be measured Formulae relating the parameters of the generatrix of the meniscus surface and the capillary pressure have been obtained for the topographic method ofScheludko et al
124 citations
TL;DR: In this paper, a method to obtain contact angle by observing the shape of a liquid drop attached to a monofilament was described. But it was not shown that this method has practical utility for measurement of the contact angle between liquid and polyurethane.
Abstract: This paper describes a method to obtain contact angle by observing the shape of a liquid drop attached to a monofilament. The relations between contact angle and the dimensions of drops are theoretically obtained. Thus, it is possible to calculate the contact angle if drop shape is measured. Through use of this method, the contact angles of epoxy resin on various kinds of monofilaments were measured. It was found that this method has practical utility for measurement of the contact angle between liquid and monofilament.
102 citations
80 citations
80 citations
TL;DR: In this article, the contact of human fingers with solid surfaces and their subsequent separation have been studied microscopically, using electron microscopy and contact angle measurements to examine the deposit film, which is either a distribution of droplets on a thin contaminating layer of adsorbed molecules, or a continuous film.
Abstract: The contact of human fingers with solid surfaces and their subsequent separation have been studied microscopically. Scanning electron microscopy and contact angle measurements have been applied to examine the deposit film. When a finger touches a surface, a film of liquid present on the finger spreads to produce apparent contact over much of the fingerprint ridge area. Lifting of the finger causes the film to recede and leave a deposit which may be either a distribution of droplets on a thin contaminating layer of adsorbed molecules, or a continuous film: which type is dependent on both the composition of the fingerprint and the nature of the substrate.
75 citations
TL;DR: In this paper, the effect of crystal growth on the temperature gradient ahead of the growth interface has been calculated in terms of the ribbon thickness and an empirical parameter characterizing the radiating environment of a growth apparatus.
Abstract: The development of edge-defined, film-fed growth (EFG) techniques for silicon ribbons has prompted analyses of appropriate die materials, die shapes, meniscus shapes and thermal gradients. The requirement for high electronic quality of the ribbons, in conjunction with the high effective solute distribution coefficients expected for EFG, narrows the choice of die materials primarily to graphite and fused silica. The shape of the meniscus between crystal and die has been calculated. This shape, together with contact angle information, is used to determine design criteria for both graphite and silica dies. The effect of crystal growth on the temperature gradient ahead of the growth interface has been calculated in terms of the ribbon thickness and an empirical parameter characterizing the radiating environment of the growth apparatus. Numerous 25 mm wide × 0.3 mm thick ribbons from carbon dies and a few small ribbons from silica dies have so far been grown. The ribbon quality is discussed.
72 citations
01 Jan 1975
TL;DR: In this paper, various physical factors that influence the instability and subsequent beading are examined in detail and the static equilibrium configuration of the beads attained at the completion of the dewetting process is derived.
Abstract: When a fine wire or fiber is coated with a liquid film, the latter breaks up spontaneously into beads. Such unusual wetting behavior is a particular manifestation of the general phenomenon of liquid column instability first studied by Plateau and Rayleigh. In this work various physical factors that influence the instability and the subsequent beading are examined in detail. In the first part hydrodynamic equations are solved to obtain the rate of growth of disturbances and the wavelength of the most rapidly growing disturbance. These quantities are governed primarily by the viscosity of the liquid and the thickness of the liquid film as compared to the wire radius. In the second part the static equilibrium configuration of the beads attained at the completion of the dewetting process is derived. The bead shape is determined by the contact angle of the liquid on wire and the volume of liquid available per bead. It is shown that even when the contact angle is zero, not more than three quarters of the wire surface is covered by the liquid beads.
TL;DR: In this paper, measurements of refractive indices and droplet profiles of fingerprint deposits on flat solid surfaces have been made using transmitted light interference microscopy, and from these measurements inferences are made on the structure of the droplets.
Abstract: Measurements of refractive indices and droplet profiles of fingerprint deposits on flat solid surfaces have been made using transmitted light interference microscopy. Changes in the profile with time and relative humidity have been determined. From these measurements inferences are made on the structure of the droplets. The absence of significant variation in contact angle for fingerprints on substrates of different surface energy is explained in terms of a contaminant film over the area of finger ridge contact. The thickness of this film corresponds closely to that expected for a monolayer of contamination.
01 Jan 1975
TL;DR: The angle made by a drop of saline in contact with a monolayer of Salmonella typhimurium orphagocytic cells, the contact angle, is a measure of their relative interfacial tension, and is predictive of a successful phagocytosis.
Abstract: The angle made by a drop of saline in contact with a monolayer of Salmonella typhimurium or phagocytic cells, the contact angle, is a measure of their relative interfacial tension, and is predictive of a successful phagocytosis. Smooth strains of S. typhimurium possess a contact angle lower than the phagocytic cells and resist phagocytosis. Rough strains have an angle higher than the phagocytes and are readily engulfed. The lower contact angle of smooth strains can be increased by treatment with specific antibody resulting in more efficient phagocytosis.
TL;DR: In this article, the free energies of lipid films were determined from measurements of their contact angles. The contact angles were calculated from the interference fringes formed in monochromatic light reflected from either the Plateau-Gibbs border or from lenses of bulk lipid solution trapped in the films.
Abstract: Free energies of formation of 'black' lipid films have been determined from measurements of their contact angles. The contact angles were calculated from the interference fringes formed in monochromatic light reflected from either the Plateau-Gibbs border or from lenses of bulk lipid solution trapped in the films. It is concluded that the electrostatic repulsion between the two surfaces of a film is negligibly small and that the 'steric' interaction between the adsorbed monolayers of lipid molecules is of such short range that the free energy change during film formation originates almost entirely from work done by the van der Waals forces. The free energies determined for a range of different films all agree to within a factor of three with the free energy calculated from Lifshitz theory for water phases interacting across an isotropic layer of liquid hydrocarbon. Nevertheless, a systematic trend in the experimental data suggests that this picture of the lipid film is too simple and that either the polar groups of the lipid or the structure of the hydrocarbon region (or both) of the film have a significant influence on the results.
TL;DR: In this article, the effect of surface roughness on cloud condensation was investigated and it was shown that the effect is only small in the case of surfaces with an air-water contact angle less than 20°.
Abstract: Condensation of water vapor an various surfaces was studied experimentally. For surfaces with an airwater contact angle θ less than 20° the experimentally determined values of critical supersaturation Sc. agreed with those given by the Volmer theory. At higher θ the experimental values of Sc. were below the Volmer theory values. When the applied supersaturation was less than Sc, condensation was avoided for periods as long as 20 h. Thus, if adsorption of water tends to negate the Volmer theory, the process is a slow one. It was determined both by experiment and theoretical analysis that the effect of surface roughness is to decrease Sc only Slightiy. These results suggest that most insoluble airborne particles are not likely to serve as cloud condensation nuclei.
01 May 1975
TL;DR: In this article, the Lippmann equation is used to find the interfacial tension between bulk oil and water phases and check the accuracy of the nonabsolute direct methods, such as the drop-volume technique, which have to be employed in such systems.
Abstract: An optically black lipid film in aqueous media approximates closely to an ideally polarizable system and, in this respect, can be described by a form of the Lippmann equation This equation is derived and integrated assuming the film capacitance to be independent of applied potential Measurements of the contact angle and of the bulk interfacial tension are used to find accurate values of the film tension and it is shown that, for a range of lipid films, the integrated equation is obeyed for potential differences up to approximately 100 mV Various ways are then described in which the Lippmann equation may be used to find film properties not readily accessible by other methods Thus, for phospholipid films the accurate measurement of both film and bulk interface tensions presents difficulties, but these can be overcome if the specific capacitance is known In this way the specific free energy of thinning of the film may be obtained Conversely, for films in media of low conductivity or in systems in which film area measurements are difficult the determination of the specific capacitance is not readily achieved A knowledge of the tension of the Plateau-Gibbs border together with the contact angle at different applied potentials, however, circumvents this problem Finally it is pointed out that the use of the Lippmann equation provides an independent means of finding the interfacial tension between bulk oil and water phases and hence of checking the accuracy of the nonabsolute direct methods, such as the drop-volume technique, which have to be employed in such systems
TL;DR: In this paper, a modified Gibbs adsorption isotherm, applied to the liquid gas interface, is introduced to describe the stepwise pattern of the liquid-gas interfacial tension curve.
Abstract: Stepwise bulk association is correlated to the stepwise pattern of some liquid-gas and solid-liquid interfacial parameters. On the basis of continuous distribution and aGibbs approach, a modifiedGibbs adsorption isotherm, applying to the liquid gas interface, is introduced. The latter describes the stepwise pattern of the liquid-gas interfacial tension curve. The behaviour of adsorption density, zeta potential, contact angle, settling rate of calcite suspensions and carbonate content in solutions were discussed in terms of a proposed stepwise adsorption model.
01 Aug 1975
TL;DR: In this paper, the influence of octaethyleneglycol dodecyl ether on both the contact angle and film thickness of water on polished fused silica was studied and it was found that the ability of the surfactant to produce dewetting depended extensively on the chemical (pH) and thermal history of the silica surface.
Abstract: The existence of thick stable films of water on silica has been confirmed in several laboratories. There is much evidence which shows that their thicknesses can be substantially accounted for with electrical double layer theory. Aqueous films on silica can be destabilized by a third agent that can alter either double layer, hydrogen bonding, or van der Waals components of the disjoining pressure. For example, aqueous films on silica are thinned in the presence of simple electrolytes or are rendered unstable by prior methylation of the silica surface. The ability of cationic surfactants to produce dewetting of silica is well-known in flotation technology. Here nonionic surfactants are also shown to possess autophobic activity towards silica. In particular, the influence of octaethyleneglycol dodecyl ether on both the contact angle and film thickness of water on polished fused silica was studied. It was found that the ability of the surfactant to produce dewetting depended extensively on the chemical (pH) and thermal history of the silica surface. Metastable thick aqueous films could be formed and maintained on silica in the presence of nonionic surfactant under conditions that rendered the silica hydrophobic (θ > 0). The thicknesses of these films were virtually identical with those of stable films in the absence of surfactant, e.g., 100–200 nm at hydrostatic pressures in the range 300–1600 dynes/cm 2 .
TL;DR: A thermodynamic approach to the problem of platelet adsorption out of a suspension on to a smooth and homogeneous solid surface is developed and implications in situations where plasma proteins are present and the biomaterials surfaces may be heterogeneous and rough are discussed.
Abstract: A thermodynamic approach to the problem of platelet adsorption out of a suspension on to a smooth and homogeneous solid surface is developed. The interfacial tension values required may be estimated from contact angle data by means of an equation of state relation. According to the thermodynamic approach the functional dependence of platelet adsorption on surface tension of the solid differs according to whether the surface tension of the platelets is smaller or larger than the surface tension of the liquid in which they are suspended. The implications of this thermodynamic approach in situations where plasma proteins are present and the biomaterials surfaces may be heterogeneous and rough are discussed. Previous analyses using the critical surface tension of wetting and other surface-related parameters are compared with the thermodynamic analysis given here.
TL;DR: In this paper, a technique developed by Studebaker and Snow was used to determine the contact angle of water (cosθH2O) on porous carbons which were electrochemically treated in phosphoric acid.
TL;DR: In this paper, a series of experiments elucidating the interaction of molybdenum and graphite at temperatures between 2000 and 3000°C were described, and the kinetics of the reaction were studied by a layer growth technique, perpendicular and parallel to the plane of deposition of a layered pyrocarbon.
Abstract: This paper describes a series of experiments elucidating the interaction of molybdenum and graphite at temperatures between 2000 and 3000° C The kinetics of the reaction were studied by a layer growth technique, perpendicular and parallel to the plane of deposition of a layered pyrocarbon The variation of contact angle with temperature was measured optically The behaviour of Mo wire embedded in natural graphite powder was studied The electron microprobe was used to determine diffusion of Mo in C and C in Mo Electron scanning was shown to be a powerful tool for following the movement of Mo particles on graphite surfaces A model and related mechanism are proposed to explain these results Additional work is reported to compare the above behaviour with the reaction of Mo with glassy carbon and other metals with pyrocarbon
TL;DR: In this article, an ideal solid-liquid-vapor system of positive contact angle was proposed. But this was based on the ideal contact angle hysteresis and was not suitable for the case of dynamic contact angles.
01 Feb 1975
TL;DR: In this paper, the optimal contact angle of a disc-type spacer is determined according to the relative permittivity of the spacer for R2/R1 (ratio of inner and outer electrode radii) = 1/3.
Abstract: By adopting the suitable contact angle of a disc-type spacer, the surface flashover may be effectively suppressed on account of the decrease of the maximum field strength at the spacer surface. The calculation has clarified that the optimal contact angle of the spacer is 60–70° according to the relative permittivity of the spacer for R2/R1 (ratio of inner and outer electrode radii) = 1/3, and that 20–30% decrease in the maximum strength can be brought about in various spacer-electrode arrangements. The effect on the field-relaxation of R2R1, the relative permittivity of the spacer, and the spacer shape have been studied. Experiments in air at atmospheric pressure and in compressed SF6 have verified that very few flashovers take place at the surface of the field-relaxing spacers.
01 Jul 1975
TL;DR: In this paper, the conditions of phase equilibria were examined for a system consisting of two phases in mutual contact and occupying a conical pore in a third rigid phase, where the three phases meet at a line of triple contact at the pore wall, the radius of pore at this line being denoted by r and the pressure difference across the meniscus separating the enclosed phases and the equilibrium with respect to material transport are both functions of r whether the line tension is included or not.
Abstract: The conditions of equilibrium are examined for a system consisting of two phases in mutual contact and occupying a conical pore in a third rigid phase The three phases meet at a line of triple contact at the pore wall, the radius of the pore at this line being denoted by r It is found that when a line tension is ascribed to the line of triple contact, the contact angle θ becomes a function of r, whereas it is independent of r if the line tension is ignored The pressure difference across the meniscus separating the enclosed phases and the equilibrium with respect to material transport are both functions of r whether the line tension is included or not However, because of the boundary condition imposed by the contact angle, the form of the functions very much depends on the inclusion or omission of line tension The consequences of the differing forms for phase equilibria are discussed for the memory effect in heterogeneous nucleation on porous solids and for capillary condensation from the vapor phase
TL;DR: In this paper, the measurement of the contact angles of E-glass sessile drops has been used to assess the wetting characteristics of platinum, iridium, palladium, rhodium and alloys of these materials.
Abstract: The measurement of the contact angles of E-glass sessile drops has been used to assess the wetting characteristics of platinum, iridium, palladium, rhodium and alloys of these materials. At each temperature studied platinum was wet more than palladium and iridium and markedly more than rhodium. The wetting behaviour has been associated with the stability of the metal oxide and a model has been proposed to explain qualitatively the relative degrees of wetting. The movement of molten glass drops situated at the junction between dissimilar metals is consistent with the proposed model.
TL;DR: In this article, the coupling performance of polymeric silane compounds was compared with that of the monomeric silanes for adhesion of polypropylene (PP) and polystyrene (PS) to glass.
Abstract: The coupling performance of some polymeric silane compounds was compared with that of the monomeric silanes for adhesion of polypropylene (PP) and polystyrene (PS) to glass. A silylated poly-1,2-butadiene was found to be effective for PP and, on the other hand, some copolymers derived from styrenyl triethoxysilane or γ-methacryloxypropyl trimethoxysilane for PS. Benzoyl peroxide also showed a pronounced effect on the adhesion of PP, rather than that of PS. The adhesion strength was approximately correlated with the contact angles of the resin melts on the coated glass, intensively suggesting the dependence of compatibility between resinous matrix and coupling agent on the adhesion. Their critical surface tensions, thermal behavior, and infrared spectra were also measured to discuss the relationship between the surface constitution and the adhesion effect.
01 Mar 1975
TL;DR: In this paper, a transfer mechanism was proposed and discussed for the deposition of stearic acid monolayers on collodion by the Langmuir-Blodgett method.
Abstract: The deposition of stearic acid monolayers on collodion by the Langmuir-Blodgett method was characterized by transfer ratio and withdrawal contact angle measurements. A transfer mechanism is proposed and discussed.
Patent•
22 May 1975
TL;DR: In this article, a screen assembly is presented which prevents rain drops from penetrating and which allows light and gas to be transmitted in a rain-free environment, but it is not suitable for outdoor use.
Abstract: A device is presented which prevents rain drops from penetrating and which allows light and gas to be transmitted in a rain-free environment. The device is a screen assembly whose outer surface (toward outdoors) has a contact angle with water of greater than 90° and whose inner surface has a contact angle with water of less than 90°.
TL;DR: In this article, a hydrogen glow discharge surface treatment followed by exposure to the atmosphere has been used to decrease the contact angle for distilled water on RTV-silicone and the change in contact angle has been studied in terms of vacuum ultraviolet irradiation, metastable bombardment, free-radical bombardment, and electrostatic charging.
Abstract: A hydrogen glow discharge surface treatment followed by exposure to the atmosphere has been used to decrease the contact angle for distilled water on RTV-silicone. The change in contact angle has been studied in terms of vacuum ultraviolet irradiation, metastable bombardment, free-radical bombardment, and electrostatic charging. The study demonstrates that the decrease in the contact angle is caused by the interaction of the hydrogen atoms produced in the glow discharge with the polymer surface.