Film Tension Research Articles

Improved Liver Intravital Microscopic Imaging Using a Film-Assisted Stabilization Method.

Intravital microscopy (IVM) is a valuable method for biomedical characterization of dynamic processes, which has been applied to many fields such as neuroscience, oncology, and immunology. During IVM, vibration suppression is a major challenge due to the inevitable respiration and heartbeat from live animals. In this study, taking liver IVM as an example, we have unraveled the vibration inhibition effect of liquid bridges by studying the friction characteristics of a moist surface on the mouse liver. We confirmed the presence of liquid bridges on the liver through fluorescence imaging, which can provide microscale and nondestructive liquid connections between adjacent surfaces. Liquid bridges were constructed to sufficiently stabilize the liver after abdominal dissection by covering it with a polymer film, taking advantage of the high adhesion properties of liquid bridges. We further prototyped a microscope-integrated vibration-damping device with adjustable film tension to simplify the sample preparation procedure, which remarkably decreased the liver vibration. In practical application scenarios, we observed the process of liposome phagocytosis by liver Kupffer cells with significantly improved image and video quality. Collectively, our method not only provided a feasible solution to vibration suppression in the field of IVM, but also has the potential to be applied to vibration damping of precision instruments or other fields that require nondestructive ″soft″ vibration damping.

Dynamics of sphere impact on a suspended film with glycerol and surfactant

Understanding the dynamics and inherent mechanisms of sphere impact on suspended films is important for improving sphere-film separation techniques. In this study, we conducted experiments to investigate the dynamics of sphere impact on suspended films and examine typical phenomena. We revealed the effects of dynamic viscosity and surface tension of films by altering the glycerol content (G) and the relative surfactant concentration (C*) and elucidated the characteristics of film deformation, sphere trajectory (hs), and contact time (tc). Moreover, we obtained the influences of sphere and film properties on bubble volume (Vbub) by analyzing force balance. The results indicate that three modes are observed and divided using the dimensionless energy parameter E* = Ek0/(ΔEfs + Evis) based on energy analysis, considering the sphere kinetic energy (Ek0), film surface energy increment (ΔEfs), and viscous dissipation (Evis): satisfying E* < 1, retention occurs; satisfying 1 < E* < 127.7(Ds/Df)2 (where Ds is the sphere diameter, Df is the film diameter), bubble entrainment passing appears; satisfying E* > 127.7(Ds/Df)2, non-bubble entrainment passing emerges. During retention, increasing G and C* causes film surface elasticity and hs to present a trend of first rising and then falling. For passing, the increase in G reduces deformability, leading hs to decrease, while increasing C* makes the film more susceptible to deformation, causing hs to increase. In addition, a film vibration period (τf) is introduced to measure tc, satisfying tc > 2τf for retention, while satisfying tc < τf/3 for passing. Inspection of the relationship between film deformation and falling height indicates that Vbub enlarges with increasing Ds and C* but shrinks with increasing G and release height Hs0.

Film lifting and drainage of third-grade fluid on a vertical belt with surface tension

Understanding the film lifting and draining of fluid on a vertical belt with surface tension is crucial for improving predictive models in coating and lubrication processes. This paper presents a theoretical study on the film lifting and drainage of a third-grade fluid with surface tension. The driving mechanisms on a vertical belt are the belt’s upward movement, the gradient of surface tension, and gravity. The formulated nonlinear ordinary differential equation (ODE) is solved for a series-form solution using the Adomian decomposition method. Numerical computations are used to determine the stationary point placements and the thickness of the uniform film. The study elucidated that lift velocity shows a decreasing trend, while drainage velocity exhibits an increasing trend with increasing values of inverse capillary number C and Stokes number [Formula: see text]. The lift velocity shows an increase, whereas the drainage velocity demonstrates a decrease with an increase in the Deborah number De. With increasing values of [Formula: see text] and C, the stationary points shift away from the fluid–air interface, while an increase in De causes them to move towards the interface. Surface tension plays a role in supporting drainage and leads to a shift in the stationary points towards the belt. Newtonian and third-grade fluids are also compared in terms of velocity, stationary points, uniform film, and surface tension, providing insight into their behavior.

Structural studies of amorphous polymer films: Experiment and calculation

To analyze X-ray diffraction patterns obtained from polyimide films subjected to external influence (uniaxial tension and exposure at liquid helium temperature), radial distribution function (RDF) curves were constructed and the geometry of the 4,4′-oxydiphenylene-pyromellitimide monomer (PM) was calculated. From the RDF analysis, it follows that uniaxial tension of PM polymer films leads to a change in the geometry of the monomer, and exposure at low temperatures leads to mutual ordering of the polymer chains.

Line Tension in a Thick Soap Film.

The thickness of freshly made soap films is usually in the micron range, and interference colors make thickness fluctuations easily visible. Circular patterns of constant thickness are commonly observed, either a thin film disc in a thicker film or the reverse. In this Letter, we evidence the line tension at the origin of these circular patterns. Using a well controlled soap film preparation, we produce a piece of thin film surrounded by a thicker film. The thickness profile, measured with a spectral camera, leads to a line tension of the order of 10^{-10} N which drives the relaxation of the thin film shape, initially very elongated, toward a circular shape. A balance between line tension and air friction leads to a quantitative prediction of the relaxation process. Such a line tension is expected to play a role in the production of marginal regeneration patches, involved in soap film drainage and stability.

A theoretical model to determine solid surface tension through droplet on film configuration and experimental verification

Determination of the surface tension of solids has been a challenging issue. This work presents an approach to the issue based on the configuration of a droplet spreading on a free standing film. Firstly, a theoretical model for the equilibrium configuration of a droplet spreading on a film is developed, which reveals that the surface elasticity has little contribution to the equilibrium configuration, and the effective strain of the film is determined by the bulge angle analytically. Based on these observations, a new procedure is presented to measure the surface tension of the film through droplet loading, which is realized by extrapolating the film tension as a function of the product of the film thickness and the effective strain. Finally, as a validation, we use this approach to extract the surface tension of soft elastomers. This work provides a viable and robust approach to determination of the surface tension of solids.

Controlled mechanism of dynamic behavior of water-based ultrasonic cavitation in coal pore microstructure

Coal pores are sealed as a result of water lock effect, which in turn inhibits coalbed methane (CBM) from desorbing and diffusing. It seriously restricts the efficient development of CBM in the complex geological environment. Relieving pore water lock (RPWL) in coal reservoirs is a scientific problem that puzzles CBM development. Currently, the widely-interested technology of enhancing coalbed methane recovery (ECBM) can not effectively break through the pore water lock. Ultrasonic cavitation can generate shaped charge micro-jets, high temperature, and high pressure, which may be a potential strategy to realize RPWL in coal reservoirs. It has been maturely applied in numerous fields such as medicine, chemical industry, and manufacturing industry. Therefore, water-based ultrasonic cavitation-enhanced coalbed methane recovery (WUC-ECBM) was proposed in this study. This technology has enormous application potential for the efficient and green development of CBM. However, as the theoretical key to the successful application of WUC-ECBM, its RPWL mechanism is still blank. In this paper, X-ray nondestructive testing and fluid invasion methods were used to reconstruct the digital model of coal pore microstructure. Through ultrasonic cavitation numerical simulation, the dynamic behavior mechanism of water-based ultrasonic cavitation was studied in coal pore systems, revealing the microscopic RPWL mechanism of WUC-ECBM. Results show that low metamorphic coal has a larger and fuller pore system, which reflects a stronger topological advantage. Small pores and throats are the main locations of ultrasonic cavitation. This spatial feature is consistent with pore water locking phenomenon. During the formation of a cavitation bubble, ultrasonic energy instantly weakens the surface tension of the water film and activates RPWL. When the cavitation bubble collapses, the micro-jets, high temperature, and high pressure wreak mechanical damage and thermal shock to pore water, accelerating the RPWL process. Ultrasonic frequency affects the cavitation threshold. Increasing ultrasonic power will significantly boost cavitation intensity in pores, particularly in high metamorphic coal. The research results contribute to the green, efficient and intelligent development of CBM in the harsh geological environment, and provide theoretical guidance for WUC-ECBM.

Understanding the roles of interdendritic bridging on hot tearing formation during alloy solidification

Dendritic bridging plays a key role in hot tearing formation and crack propagation, but it has yet to be clearly understood. This article describes the formation process of interdendritic bridging and its effect on the propagation of hot tearing. Two types of interdendritic bridging are proposed: mechanical bridging where dendrites are in contact with each other but are connected only by the surface tension of liquid film and metallurgical bridging where dendrites are metallurgically bonded at their contact points. Mechanical bridging cannot effectively impede crack propagation, thus exhibiting a brittle fracture characteristic, while metallurgical bridging can hinder crack propagation, resulting in a ductile fracture characteristic. Experiments on a high manganese steel were carried out to provide evidence of these two types of bridging and illustrate unique features on fractured surface that are associated with these two types of bridging. In this paper, the process of dendritic bridge formation is clearly described and its effect on hot tearing propagation is discussed.

PLA-Mg film degradation under in vitro environments supplemented with glucose and/or ketone bodies

Materials used for the manufacture of implants may suffer alterations in their surface properties as a result of continuous contact with physiological fluids. Moreover, in biodegradable and bioabsorbable materials, such as polylactic acid (PLA), these changes may be more accentuated, and their biological response may be affected by the presence of proteins, enzymes or other compounds of an oxidizing character. This research proposes to study the degradation of PLA in a close-to-reality environment by supplementing the physiological buffer m-SBF with concentrations of glucose and ketone bodies of healthy individuals. To this end, parameters such as hydrophobicity, surface tension, topography and surface chemical composition of PLA films and PLA films doped with magnesium particles after degradation were evaluated to determine how these components influence these properties compared to degradation in standard buffer. The presence of glucose and/or ketone bodies in the degradation medium of PLA doped with magnesium particles altered the composition of the salt layers absorbed on the surface of the material due to the action of gluconate and/or hydroxybutyrate anions, which were able to coordinate with ions from the solution as well as Mg2+ cations from polymer degradation. The salt accumulation on polymeric films changes the surface mechanical response increasing the Young's modulus after degradation.

A Novel Strategy for the Demulsification of Peanut Oil Body by Caproic Acid.

The aqueous enzymatic method is a form of green oil extraction technology with limited industrial application, owing to the need for the demulsification of the oil body intermediate product. Existing demulsification methods have problems, including low demulsification rates and high costs, such that new methods are needed. The free fatty acids produced by lipid hydrolysis can affect the stability of peanut oil body (POB) at a certain concentration. After screening even-carbon fatty acids with carbon chain lengths below ten, caproic acid was selected for the demulsification of POB using response surface methodology and a Box-Behnken design. Under the optimal conditions (caproic acid concentration, 0.22%; solid-to-liquid ratio, 1:4.7 (w/v); time, 61 min; and temperature, 79 °C), a demulsification rate of 97.87% was achieved. Caproic acid not only adjusted the reaction system pH to cause the aggregation of the POB interfacial proteins, but also decreased the interfacial tension and viscoelasticity of the interfacial film with an increasing caproic acid concentration to realize POB demulsification. Compared to pressed oil and soxhlet-extracted oil, the acid value and peroxide value of the caproic acid demulsified oil were increased, while the unsaturated fatty acid content and oxidation induction time were decreased. However, the tocopherol and tocotrienol contents were higher than those of the soxhlet-extracted oil. This study provides a new method for the demulsification of POB.

Lifting and drainage of Sisko fluid film with surface tension: A theoretical study on stationary points and thickness of uniform film

This paper accords with the theoretical study of lifting and drainage of Sisko fluid film on a vertically upward moving cylinder with surface tension. The flow on cylinder is induced by the upward motion of the cylinder, gravity and surface tension gradient. The resulting nonlinear ordinary differential equation is solved for a series form solution by making use of the Adomian decomposition method (ADM). Expressions for the flow variables like velocity, volume flow rate, shear stress and surface tension are derived. Positions of stationary points and thickness of uniform film are computed numerically in MATHEMATICA. The inverse capillary number C, Stokes number [Formula: see text], Sisko fluid parameter [Formula: see text] and fluid behavior index n emerged as flow control parameters. The study showed that the positions of stationary points relocate towards the surface of the cylinder by the increase of C and [Formula: see text] while their positions relocate towards the fluid–air interface with increasing [Formula: see text] and n. Thickness of uniform film decreases when the values of C and [Formula: see text] are increased whilst it increases with the increase of [Formula: see text] and n. Analogy between the Newtonian fluid and the Sisko fluid’s shear thinning and shear thickening behaviors for positions of stationary points, thickness of uniform film and surface tension is also made.

Investigation on sub-to-supercritical transition of diesel: Gas–liquid interface properties

ABSTRACT By establishing a high-temperature droplet evaporation test device, the influence of ambient temperature on droplet morphology and droplet diameter is studied using diesel oil (D100). The variation of droplet evaporation characteristics is studied. The phase transition model of n-heptane in a supercritical environment is established and verified by the molecular dynamics simulation method. The diffusion coefficient, radial distribution function (RDF), surface tension, interfacial thickness, and liquid film temperature of n-heptane liquid film are analyzed. The results show that when the environmental conditions change from subcritical to supercritical, the diffusion coefficient decreases first and then increases from 8.55 × 10−4 cm/s−1 to 71.75 × 10−4 cm/s−1. The peak value of RDF decreases from 1627 to 438, and the smaller peaks after the main peaks tend to be smooth, indicating that n-heptane appears as a gas under supercritical conditions, and the phase transition changes from evaporation to diffusion. Cases 5(T = 973 K P = 5 MPa), 6(T = 573 K P = 7 MPa), 8(T = 773 K P = 7 MPa), and 9(T = 973 K P = 7 MPa) are high-supercritical calculation cases, with MSD of 1.71 × 105 Å2, 4.03 × 105 Å2, 2.49 × 105 Å2, 4.07 × 105 Å2, compare with case 1(T = 573 K P = 3 MPa), MSD increased by 11 times. When T/Tc ≥1.5 and P/Pc ≥1.5, n-heptane undergo three stages of transition from subcritical state to supercritical state. The first stage is the subcritical evaporation stage. With the evaporation of n-heptane, the fuel surface tension gradually disappears, the subcritical evaporation stage ends, and the transition stage begins. When the liquid film temperature exceeds the critical value, the transition phase ends, and the supercritical diffusion phase begins. In addition, when the ambient pressure is 5 MPa and 7MPa, the ambient temperature rises from 773 K to 973 K. The proportion of the transition process in the evaporation process increases by 19% and decreases by 3%, respectively.

Surface Morphing of Azopolymers toward Advanced Anticounterfeiting Enabled by a Two-Step Method: Light Writing and Then Reading in Liquid

Surface morphing of organic materials is necessary for advances in semiconductor processing, optical gratings, anticounterfeiting etc., but it is still challenging, especially for its fundamental explanation and further applications like advanced anticounterfeiting. Here, we report one strategy to acquire surface deformation of the liquid-crystalline azopolymer film using a two-step method: selective photoisomerization of azopolymers and then solvent development. In the first step, surface tension of the polymer film can be patterned by the selective photoisomerization of azopolymers, and then in the second step, the flowing solvent drags the underlying polymer to transport, leading to the formation of surface deformation. Interestingly, the direction of mass transport is opposite to the traditional Marangoni flow, and the principle of solvents' choice is the matching of surface tensions between the azopolymer and the solvent. The two-step method shows characteristics of efficient surface morphing, which could be applied in advanced anticounterfeiting by the way of photomask-assistant information writing or microscale direct writing, and then reading in a specific liquid environment. This paves a new way for understanding the mechanism of mass transport toward numerous unprecedented applications using various photoresponsive materials.

Effect of ambient pressure on the performance of a gas-centered swirl coaxial injector

In this study, water and air were used as simulated media to investigate the spray characteristics of a gas-centered swirl coaxial (GCSC) injector under different ambient pressures through experimental, simulation, and theoretical approaches. The results showed that for the same liquid mass flow rate, the breakup length of the liquid film decreased with increasing ambient pressure, with the extent of the decrease diminishing as the ambient pressure increased. In addition, it was found that under the same ambient pressure, the larger the liquid mass flow rate, the shorter the liquid film breakup length. Moreover, for any gas–liquid mass flow ratio (GLR), the spray angle increased significantly with ambient pressure, and the liquid film suddenly expanded compared to the no-ambient pressure condition. At the same time, the breakup length of the liquid film increased. As ambient pressure increased, the spray angle increased while the breakup length decreased. When the GLR was small, self-pulsation occurred, which gradually disappeared with increasing ambient pressure. The frequency of self-pulsation decreased with increasing ambient pressure. The periodic self-pulsation of the spray was the result of the combined effects of the centrifugal force of the rotating liquid film, surface tension of the liquid film, aerodynamic force, and pressure difference inside and outside the liquid film. Overall, these findings provide insight into the spray characteristics of GCSC injectors under different ambient pressures, which can be of importance to the design and optimization of liquid rocket engines.

Adsorption and Desorption of Bile Salts at Air–Water and Oil–Water Interfaces

Bile Salts (BS) adsorb onto emulsified oil droplets to promote lipolysis and then desorb, solubilizing lipolytic products, a process which plays a crucial role in lipid digestion. Hence, investigating the mechanism of adsorption and desorption of BS onto the oil–water interface is of major importance to understand and control BS functionality. This can have implications in the rational design of products with tailored digestibility. This study shows the adsorption and desorption curves of BS at air–water and oil–water interfaces obtained by pendant drop tensiometry. Three BS have been chosen with different conjugation and hydroxyl groups: Sodium Taurocholate (NaTC), Glycodeoxycholate (NaGDC) and Sodium Glycochenodeoxycholate (NaGCDC). Experimental results show important differences between the type of BS and the nature of the interface (air/oil–water). At the air–water interface, Glycine conjugates (NaGDC and NaGCDC) are more surface active than Taurine (NaTC), and they also display lower surface tension of saturated films. The position of hydroxyl groups in Glycine conjugates, possibly favors a more vertical orientation of BS at the surface and an improved lateral packing. These differences diminish at the oil–water interface owing to hydrophobic interactions of BS with the oil, preventing intermolecular associations. Desorption studies reveal the presence of irreversibly adsorbed layers at the oil–water interface in all cases, while at the air–water interface, the reversibility of adsorption depends strongly on the type of BS. Finally, dilatational rheology shows that the dilatational response of BS is again influenced by hydrophobic interactions of BS with the oil; thus, adsorbed films of different BS at the oil–water interface are very similar, while larger differences arise between BS adsorbed at the air–water interface. Results presented here highlight new features of the characteristics of adsorption layers of BS on the oil–water interface, which are more relevant to lipid digestion than characteristics of BS adsorbed at air–water interfaces.

Antibacterial coating of corona treated Poly(lactic acid) / Poly(butylene succinate) film with Chitosan and Zinc oxide nanoparticle

The biodegradable PLA/PBS 90/10 wt% films were extruded and surface treated with corona discharge. Two electrical inputs of the corona treatment were used, 2 or 6 amperes, which the change of the surface tension was evaluated using corona measuring pens. The blend films were coated with the antibacterial mixture between chitosan and zinc oxide nanoparticles (ZnO-NP) in four concentrations: 1.0/0.4, 1.0/0.5, 1.5/0.5, and 1.5/0.5 wt%/wt%. This film could be used to replace transparent disposable packaging in the circular economy. It was found that the surface tension of the blend film was 30 dyne (mN/m) which was much like the neat PLA due to PLA being the main composition. Since the overall coated film thickness was kept constant, there was no significant difference in the coating weight among four coating concentrations. Compared to the uncoated PLA/PBS film, the tensile strength of the coated films tended to be higher with the increase of ZnO-NP content. However, the elongation at break of the coated films decreased significantly, which the stiffer coating layers became the stress concentrators. From SEM, it was seen that the good adhesion between the polymer and the coating layer was achieved. When the coated films were torn apart in the trouser tear testing, the failure was the breakage of the blend film with there was some coating layer delaminated.

Rayleigh–Taylor instability of viscoelastic self-rewetting film flowing down a temperature-controlled inclined substrate

Rayleigh–Taylor (RT) instability of gravity-driven viscoelastic self-rewetting film flowing under an inclined substrate uniformly heated or cooled is considered. The surface tension of self-rewetting film is considered as a quadratic function of temperature. The long wave hypothesis is used to derive a nonlinear free surface evolution equation of the thin viscoelastic film. Linear stability analysis shows that for a prescribed the viscoelastic coefficient, substrate cooling products instability, while substrate heating remains stability. Furthermore, we analyze the influence of viscoelastic coefficient on RT instability. Results show that the viscoelastic coefficient reinforces the RT instability whether the substrate is heated or cooled. Moreover, we use the line method to numerically simulate the nonlinear evolution equation and systematically examine the space-time variation of the film free surface. The numerical results illustrate that increasing the viscoelastic coefficient can enhance the disturbance amplitude and wave frequency. This means that the viscoelastic coefficient makes the system unstable, which is consistent with result of the linear stability analysis. In addition, the oscillation tends to accumulate downstream of the inclined substrate when the evolution time is long enough. Finally, the variation of film thickness with related parameters for different viscoelastic coefficients is investigated.

Preliminary exploration of a novel high-performance air entraining agent based on sodium dodecyl sulfate added self-made fluorocarbon surfactant

Sodium dodecyl sulfate (SDS), an air entraining agent (AEA), is used to improve the frost resistance of concrete, but the effectiveness of SDS is urgent to be improved because it is easily weakened by many factors. In this work, a novel high-performance AEA (HPAEA) was prepared by compounding sodium dodecyl sulfate (SDS) with the self-made fluorocarbon surfactant (S-FC). The performance of HPAEA in cement paste solution and in mortar were evaluated and the improvement mechanism was explored. The results of foamability and foam stability in cement paste solution, air content and air-void parameters in cement mortar showed that S-FC could greatly promote the foam properties of SDS and optimize the air-void structure in entrained mortar. When the concentration of S-FC reached 0.2 wt%, foamability, foam stability, fresh air content of HPAEA was 2.9 times, 16.5 times, and 1.6 times higher than that of SDS, respectively. The air-void spacing factor in hardened mortar was reduced by more than 50%. The improvement mechanism of the effectiveness of HPAEA was revealed by the lower surface tension and better comprehensive property of the bubble liquid film, because there was synergistic effect between SDS and S-FC. It was concluded that the novel HPAEA obtained by compounding SDS with S-FC had a potential to significantly improve the frost resistance of concrete.

The velocity field characteristics of high‐viscosity fluids falling film flow down clamped channels

AbstractThe complexity of falling film flow has been studied in many industrial applications. In this work, the velocity field of high‐viscosity fluids falling film flow down clamped channels was investigated numerically and experimentally. The results show that the numerical simulation results are consistent with the experimental results, and the characteristics of the velocity field are related to the fluid properties, operating conditions, and structure of the clamped channels. When the fluid viscosity is greater than or equal to 10 Pa ⋅ s, the type of velocity field changes into I shape, U shape, and V shape. While the fluid viscosity drops to 0.89 Pa ⋅ s, the viscous force cannot resist the inertial force and gravity, resulting in a cardioid velocity field. By adjusting the structure of the clamped channels and operating conditions, the tension of the liquid film can be changed, and the velocity distribution of the liquid film can be manipulated. Significantly, under the fluctuating curtain flow, the liquid film coalesces and breaks frequently, which enlarges the surface area of the liquid film and strengthens the surface renewal frequency. Hence, this form of falling film flow can be applied to process intensification of high‐viscosity materials.

Quantitative analysis of biosurfactants in water samples by a modified oil spreading technique.

The oil spreading technique relies on biosurfactant to reduce the surface tension of an oil film and form an oil spreading ring in the center, and then judges the content of biosurfactant according to the diameter of the spreading ring. However, the instability and large errors of the traditional oil spreading technique limit its further application. In this paper, we modified the traditional oil spreading technique by optimizing the oily material, image acquisition and calculation method, which improves the accuracy and stability of the quantification of biosurfactant. We screened lipopeptides and glycolipid biosurfactants for rapid and quantitative analysis of biosurfactant concentrations. By selecting areas by color done by the software to modify image acquisition, the results showed that the modified oil spreading technique has a good quantitative effect, reflected in the concentration of biosurfactant being proportional to the diameter of the sample droplet. More importantly, using the pixel ratio method instead of the diameter measurement method to optimize the calculation method, the region selection was more exact, and the accuracy of the data results was high, and the calculation efficiency was improved significantly. Finally, the contents of rhamnolipid and lipopeptide in oilfield water samples were judged by the modified oil spreading technique, the relative errors were analyzed according to the different substances as the standard, and the quantitative measurement and analysis of oilfield water samples (the produced water of Zhan 3-X24 and the injected water of the estuary oil production plant) were realized. The study provides a new perspective on the accuracy and stability of the method in the quantification of biosurfactant, and provided some theoretical and data support for the study of the microbial oil displacement technology mechanism.