Small Surface Tension Research Articles

Aggregation behavior of two separate polymers confined between two membranes

An off-lattice Monte Carlo method is used to study the aggregation behavior of two separate confined polymer chains induced by membranes. A separation-to-combination transition occurs when the two separate chains are induced to combine and become a sphere by membranes for large surface tension σ at the critical distance dc. However, they still remain separate and each chain adopts a globular conformation for small surface tension σ at dc. For d dc, they keep separate and each chain becomes a sphere under compression of membranes for all σ. Formation of a membrane tunnel between two separate chains and entropy lead to the aggregation of separate polymer chains. In addition, dc and chain length N satisfy the relation: dc ∼ N0.46. This investigate can provide insights into the chromosome segregation/aggregation between two biological membranes, or single polymer manipulation through a membrane.

Effect of different surfactants on colloidal and polymer properties of fluorinated acrylate latex

Fluorinated acrylate latex was successfully prepared by semi-continuous seeded emulsion polymerization of dodecafluoroheptyl methacrylate (DFMA) with butyl acrylate (BA), methyl methacrylate (MMA) initiated by potassium persulfate in the water. The resultant latexes and their films are characterized with Fourier transform infrared (FTIR) spectrometry, contact angle determinator, dynamic light scattering detector and surface tension determinator. Effect of different surfactants on colloidal and polymer properties of fluorinated acrylate latex was studied. Results show that the latex prepared with sodium dodecyl benzene sulfonate surfactant has the smallest particle size and contact angle but the moderate surface tension. The latex prepared with perfluorooctanesulfonic acid potassium surfactant has the smallest surface tension, moderate particle size but the biggest contact angle. The latex prepared with sodium 2-hydroxy-3-(methacryloyloxy) prop- ane-1-sulfonate surfactant has the biggest particle size and surface tension but moderate contact angle. In addition, the latex prepared with sodium 2-hydroxy-3-(methacryloyloxy) prop- ane-1-sulfonate has higher electrolyte stability.

Theoretical Investigation of the Influence of Liquid Physical Properties on Effervescent Atomization Performance

Background. A comprehensive model in the Eulerian-Lagrangian scheme is used to investigate the performance of the gas-droplet two-phase flow for a typical effervescent atomization spray with different atomized liquids. Method of Approach. Based on the particle tracking method, the droplet primary and secondary breakup, droplets collision and coalescence are taken into consideration. Results. The predicted droplet mean size is compared well with the published experimental data. The influences of liquid physical properties are discussed not only on droplet mean size, but also on droplet velocity, distribution, events of breakup and collision, Weber number, Ohnesorge number and their evolutions. Conclusions. Results show liquid viscosity has a slight effect on the droplet size and its distribution. While a decrease in liquid surface tension serves to get finer droplets and wider droplet spatial distribution. Small liquid density, surface tension and viscosity are benefit for getting higher atomized droplet velocity.

Regularized shock solutions in coating flows with small surface tension

We study the dynamics of thin liquid films on the surface of a rotating horizontal cylinder in the presence of gravity in the small surface tension limit. Using dynamical system methods, we show that the continuum of shock solutions increasing across the jump point persists in the small surface tension limit, whereas the continuum of shock solutions decreasing across the jump point terminates in the limit. Using delicate numerical computations, we show that the number of steady states with equal mass increases as the surface tension parameter goes to zero. This corresponds to an increase in the number of loops on the mass-flux bifurcation diagram. If n is the number of loops in the mass-flux diagram with 2n + 1 solution branches, we show that n + 1 solution branches are stable with respect to small perturbations in the time evolution of the liquid film.

Stretching of viscous threads at low Reynolds numbers

AbstractWe investigate the classical problem of the extension of an axisymmetric viscous thread by a fixed applied force with small initial inertia and small initial surface tension forces. We show that inertia is fundamental in controlling the dynamics of the stretching process. Under a long-wavelength approximation, we derive leading-order asymptotic expressions for the solution of the full initial-boundary value problem for arbitrary initial shape. If inertia is completely neglected, the total extension of the thread tends to infinity as the time of pinching is approached. On the other hand, the solution exhibits pinching with finite extension for any non-zero Reynolds number. The solution also has the property that inertia eventually must become important, and pinching must occur at the pulled end. In particular, pinching cannot occur in the interior as can happen when inertia is neglected. Moreover, we derive an asymptotic expression for the extension.

Synthesis and characterization of a novel silicone containing vinylic macromonomer and its uses in the preparation of poly (silicone‐co‐styrene‐co‐butylacrylate) with montmorillonite nanocomposite emulsion

AbstractA new silicone containing macromonomer, 4‐(methacrylamido) phenoxy polymethylhydrosiloxane (4‐MPMHS) with a vinyl group, was successfully synthesized. Then poly (silicone‐co‐styrene‐co‐butylacrylate) with montmorillonite, P (Si‐co‐St‐co‐BA) with MMT nanocomposite emulsion was prepared by in situ intercalative emulsion polymerization of styrene (St), butyl acrylate (BA), and 4‐MPMHS, in the presence of organic modified montmorillonite (OMMT) with different OMMT contents (0, 0.5, 1.0, 1.5, and 2 wt %). Potassium persulphate (KPS) was used as an initiator and sodium lauryl sulfoacetate (SLSA) and nonyl phenol ethylene oxide—40 U (NP‐40) were used as anionic and nonionic emulsifiers, respectively. The resulting macromonomer was characterized by elemental analysis, Fourier transformer infrared (FT‐IR), proton (1H NMR), and carbon (13C NMR) nuclear magnetic resonance spectroscopes. The OMMT was characterized by FT‐IR and X‐ray diffraction (XRD). The nanocomposite emulsions were characterized by using Fourier Transform infrared spectroscopy (FT‐IR), laser light scattering, and surface tension method. Thermal properties of the copolymers were studied using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) and then the effects of OMMT percent on the water absorption ratio and drying speed were examined. Results showed that OMMT could improve the properties of emulsion. In other words, the properties of nanocomposite emulsions were better when compared with those of the silicone‐acrylate emulsion. The property of nanocomposite emulsion containing 1 wt % OMMT was the best one, and the following advantages were obtained: smaller particle size, faster drying speed, smaller surface tension, and improved water resistance by the incorporation of OMMT. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Numerical solution to the Saffman--Taylor finger problem with kinetic undercooling regularisation

The Saffman--Taylor finger problem is to predict the shape and, in particular, width of a finger of fluid travelling in a Hele--Shaw cell filled with a different, more viscous fluid. In experiments the width is dependent on the speed of propagation of the finger, tending to half the total cell width as the speed increases. To predict this result mathematically, nonlinear effects on the fluid interface must be considered; usually surface tension is included for this purpose. This makes the mathematical problem sufficiently difficult that asymptotic or numerical methods must be used. We adapt numerical methods used to solve the Saffman--Taylor finger problem with surface tension to instead include the effect of kinetic undercooling, a regularisation effect important in Stefan melting-freezing problems, for which Hele--Shaw flow serves as a leading order approximation when the specific heat of a substance is much smaller than its latent heat. We find the existence of a solution branch where the finger width tends to zero as the propagation speed increases, disagreeing with some aspects of the asymptotic analysis of the same problem. We also find a second solution branch, supporting the idea of a countably infinite number of branches as for the surface tension problem. References P. G. Saffman and G. Taylor. The penetration of a fluid into a porous medium or Hele--Shaw cell containing a more viscous liquid. Proc. R. Soc. London, Ser. A , 245:312--329, 1958. doi:10.1098/rspa.1958.0085 J. W. McLean and P. G. Saffman. The effect of surface tension on the shape of fingers in a Hele--Shaw cell. J. Fluid. Mech. , 102:455--469, 1981. doi:10.1017/S0022112081002735 J. M. Vanden-Broeck. Fingers in a Hele--Shaw cell with surface tension. Phys. Fluids , 26(8):2033--2034, 1983. doi:10.1063/1.864406 S. J. Chapman. On the role of Stokes lines in the selection of Saffman--Taylor fingers with small surface tension. Eur. J. Appl. Math. , 10(06):513--534, 1999. doi:10.1017/S0956792599003848 R. Combescot, T. Dombre, V. Hakim, Y. Pomeau, and A. Pumir. Shape selection of Saffman--Taylor fingers. Phys. Rev. Lett. , 56(19):2036--2039, May 1986. doi:10.1103/PhysRevLett.56.2036 R. Combescot, V. Hakim, T. Dombre, Y. Pomeau, and A. Pumir. Analytic theory of the Saffman--Taylor fingers. Phys. Rev. A , 37(4):1270--1283, February 1988. doi:10.1103/PhysRevA.37.1270 M. Reissig, S. V. Rogosin, and F. Hubner. Analytical and numerical treatment of a complex model for Hele--Shaw moving boundary value problems with kinetic undercooling regularization. Eur. J. Appl. Math. , 10(6):561--579, 1999. doi:10.1017/S0956792599003939 S. J. Chapman and J. R. King. The selection of Saffman--Taylor fingers by kinetic undercooling. J. Eng. Math. , 46(1):1--32, 2003. doi:10.1023/A:1022860705459 D. Bensimon. Stability of viscous fingering. Phys. Rev. A , 33(2):1302--1309, 1986. doi:10.1103/PhysRevA.33.1302 D. A. Kessler and H. Levine. Theory of the Saffman--Taylor ``finger'' pattern. {I}. Phys. Rev. A , 33(4):2621--2633, 1986. doi:10.1103/PhysRevA.33.2621 D. A. Kessler and H. Levine. Theory of the Saffman--Taylor ``finger'' pattern. {II}. Phys. Rev. A , 33(4):2634--2639, 1986. doi:10.1103/PhysRevA.33.2634 A. J. Degregoria and L. W. Schwartz. A boundary integral method for two-phase displacement in Hele--Shaw cells. J. Fluid Mech. , 164:383--400, 1986. doi:10.1017/S0022112086002604 T. Y. Hou, Z. Li, S. Osher, and H. Zhao. A hybrid method for moving interface problems with application to the Hele--Shaw flow. J. Comput. Phys. , 134(2):236--252, 1997. doi:10.1006/jcph.1997.5689 G. Tryggvason and H. Aref. Numerical experiments on Hele--Shaw flow with a sharp interface. J. Fluid Mech. , 136:1--30, 1983. doi:10.1017/S0022112083002037 N. Whitaker. Some numerical methods for the Hele--Shaw equations. J. Comput. Phys. , 111(1):81--88, 1994. doi:10.1006/jcph.1994.1046

Performance tests on a novel vapor chamber

Abstract Experiments on vapor chamber performance with working fluid of water, methanol or acetone were conducted using our novel vapor chambers. Water has remarkably larger latent heat and surface tension, and acetone has similar surface tension as methanol but smallest latent heat. A sintered two-layer 100 + 200 mesh wick was adopted, and the volumetric fluid charges were the same. The footprint of the vapor chamber was 90 mm × 100 mm. The vapor chamber was loaded at its central bottom with a dummy heater of 1.21, 4.41 or 9.61 cm2. Water presents the largest maximum heat loads and acetone the smallest, in the same sequence of their figures of merit. However, the differences are not as distinct as in their figures of merit, due to the short cycling distance in the novel design. As for the minimum vapor chamber resistances, water presents the smallest value and acetone the largest, as acetone presents the largest average evaporating film thickness primarily due to its small surface tension. For all three working fluids, the minimum vapor chamber resistances strongly decreased with increasing heated area. For sufficiently large heated area, this can be mainly attributed to a smaller average evaporating film thickness for a larger evaporation area.

Molecular dynamics calculations of small drops surface tension

In our paper the results of molecular dynamics calculations of nanodrops are presented. The density profiles, the Irving–Kirkwood pressure tensors, the chemical potentials of the systems, the equimolar radii of the drops and the radii of tension, the mechanical and thermodynamic surface tensions have been calculated. It is shown that both the mechanical and thermodynamic surface tension decrease with the decrease of the equimolar radius of the drop, and reach zero at the same R 0 depending on temperature. The radii of tension surfaces also reach zero. The notion of surface tension which is used in macroscopic theory cannot be applied to small droplets with equimolar radius less than R 0.

Effect of Surface Tension and Rotation on Rayleigh-Taylor Instability of Two Superposed Fluids with Suspended Particles

The Rayleigh–Taylor instability of two superposed incompressible fluids of different densities in the presence of small rotation, surface tension and suspended dust particles is investigated. The linearized equations of the problem are constructed and the general dispersion relation is obtained using normal mode analysis by applying the appropriate boundary conditions. The effects of surface tension, the Atwood number, small rotation and suspended dust particles are studied on both conditions of Rayleigh–Taylor instability and growth rate of the unstable Rayleigh–Taylor mode. The numerical calculations have been performed to see the effect of rotation, the Atwood number, relaxation frequency and mass concentration of suspended dust particles. It is found that the growth rate of Rayleigh–Taylor instability depends upon the mass concentration and relaxation frequency of suspended dust particles. The uniform small rotation, relaxation frequency and mass concentration of suspended dust particles all have stabilizing influence on the growth rate of Rayleigh–Taylor instability. It is also found that the Atwood number has destabilizing influence on the growth rate of the considered Rayleigh–Taylor configuration.

Design and use of mini-phantoms for high resolution planar gamma cameras

There is now wide spread interest in the application of small field of view gamma cameras for clinical use in operating theatres, intensive care units and bedside imaging. The development of these imaging systems some of which have improved spatial resolution has necessitated a reappraisal of the suitability of conventional phantoms intended for use with gamma cameras. The testing of imagers having increased system resolution requires phantoms and test objects of smaller dimensions. We have investigated the use of high resolution mini-phantoms for the evaluation of planar imaging devices with spatial resolution of the order of 1 mm. We present images of a number of phantoms that show their suitability for evaluating high resolution planar gamma cameras. It is also apparent that there are a number of practical difficulties that have not been previously reported when using liquid filled phantoms with hole sizes between 1 and 4 mm. In particular problems of filling small diameter holes and liquid surface tension effects can limit the utility of these phantoms. Initial observations when imaging mini-phantoms with a high resolution CCD based gamma camera are presented.

Additional Support for a Revised Gibbs Analysis

Gibbs-determined areas of >60 A(2)/molecule for many common surfactants cause rather small surface tension reductions when measured on a Langmuir film balance. This is inconsistent with an air/water interface being saturated throughout the steep linear decline in plots of surface tension versus ln [surfactant]. In support for a gradually populating interface in the linear region, we have found that sodium docosanyl sulfate lowers the surface tension by only 7 mN/m when compressed to 50 A(2)/molecule. When docosanyltrimethylmmonium bromide is compressed to 65 A(2)/molecule, the surface tension is lowered about 15 mN/m as compared to a 30-40 mN/m drop occurring within the range of typical Gibbs analysis. Saturation of the interface is often obscured by competitive micelle formation that levels the surface tension versus ln [surfactant] plot before saturation has a chance to do so.

Macroscopic liquid phase separation of Fe–Sn immiscible alloy investigated by both experiment and simulation

The macroscopic phase separation of undercooled liquid Fe50Sn50 immiscible alloy was investigated by both drop tube experiment and the modified Model H. Core-shell structures with two, three, and five layers were formed during experiment. The concentric shells comprised of Fe-rich phase and Sn-rich phase distribute periodically in the solidified droplet, and the Sn-rich phase is always located at the sample surface owing to its smaller surface tension. The simulated results of modified Model H reproduce core-shell structures with the same layers, which justifies the prediction of this model. If the fluidity parameter Cf and solute concentration ϕ satisfy the physical conditions of both Cf<1 and 0<ϕ<0.45 or Cf≥1, the phase separation morphology exhibits the double-layer core-shell structure, whereas the multilayer core-shell structure is expected to form under the conditions of both Cf<1 and 0.45≤ϕ<0.5. The forming ability of core-shell structure for various immiscible alloys can be predicted accordingly.

Oil-Free Generation of Small Polymeric Particles Using a Coaxial Microfluidic Channel

In this study, a microfluidic method to generate small polymeric particles ( approximately 10 mum in diameter) via the control of interfacial tension without using oil and in situ photopolymerization immediately after drop generation was introduced. For the reduction in size, the selection of proper sample and sheath liquid to minimize the interfacial tension is extremely important, and 4-HBA (4-hydroxybutyl acrylate) and PVA (poly(vinyl acrylate)) were employed as core and sheath fluid pair because of much smaller surface tension than the case using oil. In addition, PVA is easily washable by aqueous solution, which is a strong advantage when the particle is applied in biomedical fields. The viscosity effect of sheath flow was also examined for further size reduction. The loading and release properties of proteins were evaluated using fluorescently labeled bovine serum albumin for the potential application as drug carrier. The protein was uniformly loaded into particles, and the protein release rate was dependent on the particle size. For utility in the biomedical area, the cyto-compatibility test of 4-HBA was performed by culturing glioma cells on the 4-HBA sheet, and the cells were alive well after 4 days culture. Conclusively, this oil-free particle generation methods facilitates the generation of uniform and small particles in a simple way without an oil-washing process.

Asymptotic expansions for solitary gravity-capillary waves in two and three dimensions

High-order asymptotic series are obtained for two- and three-dimensional gravity-capillary solitary waves. In two dimensions, the first term in the asymptotic series is the well-known sech 2 solution of the Korteweg–de Vries equation; in three dimensions, the first term is the rational lump solution of the Kadomtsev–Petviashvili equation I. The two-dimensional series is used (with nine terms included) to investigate how small surface tension affects the height and energy of large-amplitude waves and waves close to the solitary version of Stokes’ extreme wave. In particular, for small surface tension, the solitary wave with the maximum energy is obtained. For large surface tension, the two-dimensional series is also used to study the energy of depression solitary waves. Energy considerations suggest that, for large enough surface tension, there are solitary waves that can get close to the fluid bottom. In three dimensions, analytic solutions for the high-order perturbation terms are computed numerically, and the resulting asymptotic series (to three terms) is used to obtain the speed versus maximum amplitude curve for solitary waves subject to sufficiently large surface tension. Finally, the above asymptotic method is applied to the Benney–Luke (BL) equation, and the resulting asymptotic series (to three terms) is verified to agree with the solitary-wave solution of the BL equation.

Three-dimensional gravity–capillary waves on water — Small surface tension case

This paper considers three-dimensional gravity–capillary waves on water of finite-depth, which are uniformly translating in a horizontal propagating direction and periodic in a transverse direction. The exact Euler equations are formulated as a spatial dynamic system in which the variable used for the propagating direction is a time-like variable. The existence of the solutions of the system is determined by two non-dimensional constants, the Bond number b and the Froude number F , which in turn give the number of eigenvalues on the imaginary axis of the complex plane for the corresponding linearized operator around a uniform flow. Assume that λ = F − 2 , C 1 is the curve in the ( b , λ ) -plane on which the first two eigenvalues for three-dimensional waves collide at the imaginary axis, and the intersection point of C 1 with { λ = 1 } is b 1 > 0 . In this paper, the case for 0 < b < b 1 and ( b , λ ) near C 1 is considered. A center-manifold reduction technique and a normal form analysis are applied to show that the dynamical system can be reduced to a system of ordinary differential equations. Using the existence of a homoclinic orbit connecting to a two-dimensional periodic (called generalized solitary-wave, thereafter) solution for the reduced system, it is shown that such a generalized solitary-wave solution persists for the original system by applying a perturbation method and adjusting some appropriate constants.

Production and functional properties of beef lung protein concentrates

This work investigated the production and the properties of meat protein concentrates from beef lungs (BLPC) at pilot scale. Protein recovery and functional properties were compared to those of BLPC obtained using membrane technology in a previous work (Selmane, D., Vial, C., & Djelveh, G. (2008). Extraction of proteins from slaughterhouse by-products: Influence of operating conditions on functional properties. Meat Science, 79, 640–647). An alkaline solubilisation method was applied for protein extraction, followed by pI precipitation for concentration. The physicochemical properties of BLPC such as molecular mass, solubility, surface hydrophobicity, surface tension and interfacial tension, as well as technofunctional emulsifying and foaming properties were determined. These were compared to those of commercial protein ingredients, such as sodium caseinates, whey protein isolates, egg white proteins and soy protein isolates. Results showed that proteins from BLPC included a low-molecular-weight fraction and exhibited good solubility and high hydrophobicity with small surface and interfacial tensions. This explained their excellent emulsifying activity, better than sodium caseinates, and their good foaming properties.

キャピラリージェット形状を利用した動的表面張力の測定法 : 第1報,噴流形状の理論的解析(流体工学,流体機械)

A theoretical and experimental consideration is conducted to propose a novel method to measure the dynamic surface tension of surfactant solution. The trajectory of laminar jet injected from a horizontal capillary tube is considered from an approximate theory. The momentum balance is discussed between surface tension, gravitational force, pressure and viscous force. Since the effect of gravitational force is relatively small compared with the surface tension, the cross section of jet is assumed as a circle and the pressure inside the jet is approximately obtained from the Laplace equation. The ordinary differential equation of motion is solved numerically by the simple Runge Kutta's method to obtain the profile of jet trajectory. The trajectory profiles are measured experimentally for water and two kinds of ethanol solutions with smaller surface tension than that of water. The theoretical profiles agree well with experimental ones for each condition and the trajectories are strongly dependent on the surface tension. It is demonstrated that the change of surface tension of surfactant solution could be measured by the method proposed in this study.

The molecular face of lipid rafts in model membranes.

Cell membranes contain a large number of different lipid species. Such a multicomponent mixture exhibits a complex phase behavior with regions of structural and compositional heterogeneity. Especially domains formed in ternary mixtures, composed of saturated and unsaturated lipids together with cholesterol, have received a lot of attention as they may resemble raft formation in real cells. Here we apply a simulation model to assess the molecular nature of these domains at the nanoscale, information that has thus far eluded experimental determination. We are able to show the spontaneous separation of a saturated phosphatidylcholine (PC)/unsaturated PC/cholesterol mixture into a liquid-ordered and a liquid-disordered phase with structural and dynamic properties closely matching experimental data. The near-atomic resolution of the simulations reveals remarkable features of both domains and the boundary domain interface. Furthermore, we predict the existence of a small surface tension between the monolayer leaflets that drives registration of the domains. At the level of molecular detail, raft-like lipid mixtures show a surprising face with possible implications for many cell membrane processes.

Numerical and experimental investigation of heat transfer on heating surface during subcooled boiling flow of liquid nitrogen

Closure correlations describing bubble nucleation and departure on the heating surface is indispensable when modeling subcooled boiling flow using a two-fluid model. Due to the small contact angle and surface tension, nucleation and departure of nitrogen vapor bubble has different characteristics to those of high-boiling liquids. For the purpose of accurate two-fluid model formulation, these factors have to be taken into consideration. In this study, some closure correlations of the bubble departure diameter, active site density and bubble waiting time were tested in the frame of the two-fluid model and the CFX code. Benchmark experiments were then performed to evaluate the correlations. Comparison of the numerical results against the experimental data demonstrates that the surface tension is crucial to modeling the bubble departure diameter and the active site density. The bubble waiting time correlation formulated according to bubble growth is expected to be used as a criterion of judging the transition from subcooled to saturated boiling.