Solid-liquid Interfacial Tension Research Articles

Primary and Secondary Nucleation Threshold of Succinic Acid: From the Perspective of Dimensionless Solid–Liquid Interfacial Tension

Primary and Secondary Nucleation Threshold of Succinic Acid: From the Perspective of Dimensionless Solid–Liquid Interfacial Tension

Micro-scale crystallization thermodynamics study of typical energetic compounds integrating optofluidics and machine learning

With the aim of investigating the changing law of crystallization driving force of typical energetic compounds under micro-scale crystallization conditions, a thermodynamic parameter determination method based on optofluidics was proposed. Aimed at nitro, nitramine and nitrate explosives in energetic compounds, hexanitrostilbene (HNS), cyclotetramethylene tetranitramine (HMX) and pentaerythritol tetranitrate (PETN) were selected as representatives, the solubility of the three kinds of energetic compounds in their respective commonly used solvents (HNS: in DMF, DMSO, NMP; HMX: in DMF, DMSO, CYC; PETN: in DMF, DMSO, EAc) at different temperatures were determined. Furthermore, microfluidics and machine learning were combined, the solubility data of the explosives were processed using BP neural network. Moreover, the metastable zone widths of HNS, HMX and PETN in each solvent were determined using on-line Raman technique. Additionally, crystalline thermodynamic parameters such as solid–liquid interfacial tension, crystal surface entropy factor, enthalpy of dissolution and etc. were calculated for each system.

Peeling off behavior of centimeter-level molten pool subjected to subsonic tangential airflow during laser ablation process

In this paper, a computational fluid dynamics model considering the interaction between subsonic tangential airflow and centimeter-level molten pool was established to investigate the melt peeling off behavior during laser ablation process. The results showed that the airflow resulted in violent fluctuations on the surface of molten pool and then flowed upward at a velocity of 2–10.5 m/s, accelerating the surface melt to move upward. A liquid column was formed and elongated slender along the metal surface pushed by the subsonic tangential airflow. An upward-bending tail appeared at the end of the liquid column, which was accelerated up to 6 m/s and then cut off by the airflow, making the melt peel away from the molten pool. Compared with the partial melt peeling off at 0.3 Ma, almost all of the melt was pushed out of the molten pool to peel off when the airflow velocity was increased to 0.5 Ma. When the airflow velocity was further increased to 0.8 Ma, the metal on the surface was accelerated in short time, leading to the peel-off occurring in advance. In addition, the melt temperature decreased due to the forced convection cooling effect of airflow. When the melt solidified, the solid-liquid interfacial tension generated in the liquid column provided tangential force conducive to cutting off the liquid column and peeling off. The decrease rate of the melt temperature with time accelerated significantly and then expedited the melt solidifying and peeling off when the airflow velocity was increased to 0.5 Ma. The decrease rate further accelerated and the temperature decrease occurred earlier at 0.8 Ma, reaching a stable state in a shorter time.

Anomalous Water Wetting on a Hydrophilic Substrate under a High Electric Field.

Macroscopically, the traditional Young-Lippmann equation is used to describe the water contact angle under a weak electric field. Here we report a new wetting mechanism of deionized water under a strong electric field that defies the conventional Young-Lippmann equation. The contact angle of the deionized water droplet on a model hexagonal lattice with a different initial wettability is extensively modulated by the vertical electric field. The cosine of water contact angle on a hydrophilic substrate displays an anomalous linear relationship with the field, in contrast to the hydrophobic case, which shows an inverse parabolic relationship. Such anomalous wetting is verified by experimental measurements of water droplets on a pyroelectric substrate. Moreover, we identify that this anomaly arises from the linear modulation of the solid-liquid interfacial tension of hydrophilic substrates by the electric field. Our findings provide atomistic insight into the fundamental laws and new phenomena of water-surface interactions under extreme electric fields.

Dynamic contact angle measurement of hydrophilic open microchannels: The role of surface wettability

Wetting dynamics play a major role in many practical applications; however, many fundamental problems remain unresolved, especially in relation to the dynamic contact angle. The present study investigates the movement of a gas–liquid interface in an open microchannel with different materials and wettability. Using a high-speed microscope camera, the shape of the dynamic equilibrium of the gas–liquid interface in a flowing state was recorded, including the microscopic regions near the contact line. The results show that the effects of the surface wetting condition play a crucial role in altering the apparent dynamic contact angle. During the experiment, we observed an interesting phenomenon where the dynamic equilibrium contact angle under flow conditions is larger than the contact angle predicted by the Cox–Voinov law. This may be attributed to the existence of friction between the fluid and the wall surface under flow, which reduces the additional pressure at the gas–liquid interface, and the magnitude of friction is manifested through the hysteresis contact angle. The instability and periodic variation of the microscopic contact angle are caused by the surface heterogeneity near the contact line, namely, the spatial variation of solid–gas and solid–liquid interfacial tensions. Understanding the surface properties can help optimize the interface system's design and improve its efficiency for use.

Molecular insights into fluid-solid interfacial tensions in water + gas + solid systems at various temperatures and pressures.

The fluid-solid interfacial tension is of great importance to many applications including the geological storage of greenhouse gases and enhancing the recovery of geo-resources, but it is rarely studied. Extensive molecular dynamics simulations are conducted to calculate fluid-solid interfacial properties in H2O + gas (H2, N2, CH4, and CO2) + rigid solid three-phase systems at various temperatures (298-403K), pressures (0-100 MPa), and wettabilities (hydrophilic, neutral, and hydrophobic). Our results on the H2O + solid system show that vapor-solid interfacial tension should not be ignored in cases where the fluid-solid interaction energy is strong or the contact angle is close to 90°. As the temperature rises, the magnitude of H2O's liquid-solid interfacial tension declines because the oscillation of the interfacial density/pressure profile weakens at high temperatures. However, the magnitude of H2O vapor-solid interfacial tension is enhanced with temperature due to the stronger adsorption of H2O. Moreover, the H2O-solid interfacial tension in H2O + gas (H2 or N2) + solid systems is weakly dependent on pressure, while the pressure effects on H2O-solid interfacial tensions in systems with CH4 or CO2 are significant. We show that the assumption of pressure independent H2O-solid interfacial tensions should be cautiously applied to Neumann's method for systems containing non-hydrophilic surfaces with strong gas-solid interaction. Meanwhile, the magnitude of gas-solid interfacial tension increases with pressure and gas-solid interaction. High temperatures generally decrease the magnitude of gas-solid interfacial tensions. Further, we found that the increment of contact angle due to the presence of gases follows this order: H2 < N2 < CH4 < CO2.

A Simple Method to Measure the Contact Angle of Metal Droplets on Graphite

The determination of solid–liquid interfacial tension plays an important role in science and technology. Here, we propose a simple method to directly measure the contact angle between metal droplets and a graphite substrate for the determination of metal–graphite interfacial tension. The proposed method involves the synthesis of micro- and nanosized metal droplets on graphite by arc melting. Owing to its small volume, the rapid cooling of the prepared metal droplets on the graphite substrate leads to the freezing of equilibrium contact configuration after solidification. We observe that the measured contact angle between micro- and nanosized Au (or Ag) particles and the graphite substrate is almost size independent, even though the size of the particles synthesized herein is 1–3 orders of magnitude smaller than that studied in previous works. In addition, the interfacial tensions of Au and Ag on the step edges (edge plane) of graphite are found to be larger than that on the (0001) plane (basal plane). The proposed method provides a simple approach to determine the solid–liquid interfacial tension and may be effective in the study of interface related science and technology.

Simplified surface wettability determination defined by new interfacial interaction compatibility expressions for composites

To date, the compatibility of two different materials of composites has been determined solely by the empirical surface wettability approach, using methods such as contact angle measurement. However, this method can be quite cumbersome, requiring specific equipment and different liquid probes. Therefore, this paper aims to develop a simplified approach to determining surface wettability, incorporating novel generalized expressions that account for the interfacial interaction compatibility of various constituents within composites. First, an economical, simplistic, and verified water probe method is employed to measure apparent contact angles. The determined apparent contact angles are shown to fit well within the thresholds established from the available findings. Then, new mathematical expressions incorporating the adhesion concept are derived to describe the constitutive relationship between the ratios of apparent contact angles of two materials for composites formation and their liquid-solid interfacial tension by fitting data gathered from existing studies. The newly developed constitutive equations offer a convenient and reliable means to determine the compatibility relationships of numerous composite constituent mixes for varying contact angle ratios. This approach enables a simple and cost-effective estimation of surface interaction via the apparent contact angle between water and the composite constituents.

On the migration of a droplet driven by thermocapillary action in a wettability-confined track

We report a study of the thermocapillary migration of droplets under a radial thermal gradient and in a wettability-confined track. A three-dimensional mathematical model is established based on the lubrication approximation. By considering the contact-line dynamics, a method for determining the velocity of the contact line in different directions is proposed for a three-dimensional droplet. Numerical simulations are performed to investigate the variations in the droplet profile, contact angle, and contact line. Three substrate-wettability cases are considered: uniform, temperature-dependent, and track-dependent wettability. The results show that when the substrate wettability is uniform, the droplet height initially decreases rapidly, and its center becomes concave and then gradually evolves into a ring-like morphology. Reducing the temperature sensitivity of the liquid–gas interfacial tension or increasing the temperature sensitivity of the liquid–solid interfacial tension decreases the equilibrium contact angle and accelerates thermocapillary migration. When a droplet spreads in a wettability-confined track, a wave-like peak is formed on each side of the droplet along the track direction until it finally separates into two distinct parts. As the track width is decreased, the time taken for a droplet to split into two smaller droplets advances, and the separation time presents a linear relationship with the track width.

The application of chitosan as an eco-filler of polymeric composites

The aim of the study was the synthesis of polymer biocomposites based on acrylates with the addition of various amounts of chitosan as an eco-filler. The composites (BPA.DA + NVP) were prepared using the photopolymerization technique. The obtained materials were subjected to physicochemical tests, determining, among others, their hardness and thermal properties by the DSC and TG/DTG methods. The ATR/FT-IR analysis and optical profilometer as well as the values of the solid surface tension calculated from the contact angle of model liquids and van Oss et al. approach to the solid-liquid interface tension were performed to confirm the chemical structure of the obtained biocomposites.

Surfactants Improving the Wetting Behavior and Adhesion Mechanism of Pesticide Dilution Droplets on Jujube Leaf Surfaces.

Fruit tree leaves have different chemical compositions and diverse wax layer structures that result in different patterns of wetting and pesticide solution spreading on their surface. Fruit development is a time when pests and diseases occur, during which a large number of pesticides are needed. The wetting and diffusion properties of pesticide droplets on fruit tree leaves were relatively poor. To solve this problem, the wetting characteristics of leaf surfaces with different surfactants were studied. The contact angle, surface tension, adhesive tension, adhesion work, and solid-liquid interfacial tension of five surfactant solution droplets on jujube leaf surfaces during fruit growth were studied by the sessile drop method. C12E5 and Triton X-100 have the best wetting effects. Two surfactants were added to a 3% beta-cyfluthrin emulsion in water, and field efficacy tests were carried out on peach fruit moths in a jujube orchard at different dilutions. The control effect is as high as 90%. During the initial stage when the concentration is low, due to the surface roughness of the leaves, the surfactant molecules adsorbed at the gas-liquid and solid-liquid interfaces reach an equilibrium, and the contact angle on the leaf surface changes slightly. With increasing surfactant concentration, the pinning effect in the spatial structure on the leaf surface is overcome by liquid droplets, thereby significantly decreasing the contact angle. When the concentration is further increased, the surfactant molecules form a saturated adsorption layer on the leaf surface. Due to the existence of a precursor water film in the droplets, surfactant molecules on the interface continuously move to the water film on the surface of jujube tree leaves, thus causing interactions between the droplets and the leaves. The conclusion of this study provides theoretical guidance for the wettability and adhesion of pesticides on jujube leaves, so as to achieve the purpose of reducing pesticide use and improving pesticide efficacy.

On-chip mixing of cancer cells and drug using LED enabled 2D opto-wetting droplet platforms

Droplets of microliter size serve as miniaturized reaction chambers for practical lab on a chip (LoC) applications. The transportation and coalescence of droplets are indispensable for realizing microfluidic mixing. Light can be used as an effective tool for droplet manipulation. We report a novel platform for LED-based transport and mixing of cell-encapsulated microdroplets for evaluating dose response of cancer drugs. Microcontroller enabled LEDs (Light-emitting diodes) were used to actuate droplet movement on Azobenzene coated planar silicon substrates. Droplet transport was initiated by the spatial gradient in solid-liquid interfacial tension developed through LED triggered photoisomerization of Azobenzene substrate. Detailed UV-Visible characterization of Azobenzene molecule was performed for different LED light intensities and wavelengths. A complete standalone opto-wetting toolbox was developed by integrating various components such as a microcontroller, UV LED (385 nm), blue LED (465 nm), and Azobenzene coated photoresponsive substrate. 2D transport of DI water droplets (10–30 μl) along simple trajectories was demonstrated using this device. Subsequently, the proposed opto-wetting platform was used for performing drug evaluation through on-chip mixing of droplets containing cancer cells (A549—Lung cancer cells) and cancer drug (paclitaxel). Separate cell viability analysis was performed using MTT assays, where the cytocompatibility of Azobenzene and UV light (385 nm) on A549 cells were studied. The dosage response of paclitaxel drug was studied using both MTT (3-(4,5-Dimethylthiazolyl-2)−2,5-diphenyltetrazolium bromide) and live-dead cell assays. The results obtained indicate the potential use of our device as a cost-effective, reliable opto-wetting microfluidic platform for drug screening experiments.

Liquid Concentration Measurement Based on Liquid Contact Angle

Different concentrations of the same liquid or liquids with different solutes have different surface tensions. The macroscopic phenomenon is that they have different wetting effects on the same solid surface. The liquid contact angle can describe the wetting effect. Therefore, this paper proposes a method for measuring the liquid concentration using the liquid contact angle. A glass plate with a hydrophobic layer and an angle-measuring device forms the detection part. The glass plate is placed horizontally, and the solution to be tested is dropped on the surface of the glass plate. Solutions with different concentrations have different liquid-solid interfacial tension and liquid-gas interfacial tension, resulting in different liquid contact angles, which can achieve rapid and accurate measurement of solution concentration. Experiments show that the liquid contact angle of ethanol solution decreases with the increase of liquid concentration. Different volumes of ethanol solutions with the same concentration have substantially the same liquid contact angle. This experimental method has the advantages of being simple and easy to operate, having a wide range of applications, not easily limited by the type of detection solution, having a large concentration measurement range, having less sample usage, free from electromagnetic interference, and having real-time online detection.

The effective interfacial tensions between pure liquids and rough solids: a coarse-grained simulation study.

The effective solid-liquid interfacial tension (SL-IFT) between pure liquids and rough solid surfaces is studied through coarse-grained simulations. Using the dissipative particle dynamics method, we design solid-liquid interfaces, confining a pure liquid between two explicit solid surfaces with different roughness degrees. The roughness of the solid phase is characterized by Wenzel's roughness factor and the effective SL-IFT is reported as a function of it also. Two solid-liquid systems, different from each other by their solid-liquid repulsion strength, are studied to measure the effects caused by the surface roughness on the calculation of . It is found that the roughness changes the structure of the liquid, which is observed in the first layer of liquid near the solid. These changes are responsible for the effective SL-IFT increase, as surface roughness increases. Although there is a predominance of surface roughness in the calculation of it is found that the effective SL-IFT is directly proportional to the magnitude of the solid-liquid repulsion strength. The insights provided by these simulations suggest that the increase of Wenzel's roughness factor increases the number of effective solid-liquid interactions between particles, yielding significant changes in the local values of the normal and tangential components of the pressure tensor.

(Invited) Nanoscale Wetting and Its Connection with Macroscopic Young's Equation

Wetting plays a key role in the cleaning process to remove impurities as one of the essential processes for the fabrication of semiconductor device, where cleaning of trenches with water, replacement with IPA (isopropyl-alcohol) and its removal are iteratively carried out. This process is still required upon recent reduction of the line width under 10 nm; however, this size is already at the border of the continuum limit where the theories of fluid mechanics can be applied. The authors adopted molecular dynamics (MD) simulations to examine the liquid behavior, especially regarding wetting at the nanoscale with respect to simple Lennard-Jones fluid [1-3], water [4,5], methanol as well as IPA as the liquids [6,7], while simple non-polar crystal [1-3,6], silica partially terminated with OH as the solids [4,5,7]. In these series of studies, we have shown how the solid-liquid, solid-vapor and liquid-vapor interfacial tensions can be defined in nanoscale to be consistent with Young’s equation as the macroscopic description about wetting.In the presentation, we will discuss how the interfacial tensions as the free energy can be properly calculated by MD simulations from mechanical and thermodynamic viewpoints.[1] Y. Yamaguchi, H. Kusudo, D. Surblys, T. Omori and G. Kikugawa, J. Chem. Phys. 150 (2019), 044701.[2] H. Kusudo, T. Omori, Y. Yamaguchi, J. Chem. Phys. 151 (2019), 154501.[3] Y. Imaizumi, T. Omori, H. Kusudo, C. Bistafa, Y. Yamaguchi, J. Chem. Phys., 153 (2020), 034701.[4] D. Surblys, F. Leroy, Y. Yamaguchi, F. Mueller-Plathe, J. Chem. Phys. 148 (2018), 134707.[5] C. Bistafa, D. Surblys, H. Kusudo, Y. Yamaguchi, J. Chem. Phys., 155 (2021), 064703.[6] D. Surblys, Y. Yamaguchi, K. Kuroda, M. Kagawa, T. Nakajima, and H. Fujimura, J. Chem. Phys. 140 (2014), 034505.[7] Y. Yamaguchi, S. Nakaoka, T. Hayashi, M. Kawakami, D. Yano, ECS Trans. 92 (2019), 87.

Molecular interactions at the metal-liquid interfaces.

We reported molecular simulations of the interactions among water, an epoxy prepolymer diglycidic ether of bisphenol A (DGEBA), and a hardener isophorone diamine (IPDA) on an aluminum surface. This work proposes a comprehensive thermodynamic characterization of the adhesion process from the calculation of different interfacial tensions. The cross-interactions between the atoms of the metal surface and different molecules are adjusted so as to reproduce the experimental work of adhesion. Water nanodroplets on the metal surface are then simulated to predict their contact angle. Liquid-vapor surface tensions of the epoxy prepolymer (DGEBA) and hardener (IPDA) and the solid-vapor surface tension of the aluminum surface are also calculated to provide the solid-liquid interfacial tension that remains very difficult to obtain from the mechanical definition.

Air nanobubbles retard calcite crystal growth

Demands for “green” additives that control the crystal growth and inhibit the scale formation in industrial processes are growing as never before. Nanobubbles can be the green additive for inhibiting and/or promoting the crystal growth of calcium carbonate, given their well-known unique physicochemical properties. This paper reports for the first time the changes in the crystal growth rate of calcite in liquid in the presence of air nanobubbles. We injected the air nanobubbles into the solution and studied the calcite crystal growth for the first 4 h in a static condition at 20 °C and 88 °C. We found that air nanobubbles retarded the growth rate of calcite crystal by up to 53 % and 33 % at 20 °C and 88 °C, respectively. The retardation of calcite crystal growth could differ with different number densities of air nanobubbles added to the solution. A higher number density of nanobubbles generally showed slightly greater retardation throughout the tested 4 h. Air nanobubbles may influence the crystal growth either by changing solid-liquid interfacial tension on the crystal surface, reducing the free growth sites, adsorbing Ca2+ ions, playing roles in bubble mattress and thermal buffering on the crystal surface, or combinations of them. Our findings suggest that air nanobubbles can be utilized as a green inhibitor of calcite crystal growth and calcium carbonate scale in broad industrial areas.

Assessment of wettability and rock-fluid interfacial tension of caprock: Implications for hydrogen and carbon dioxide geo-storage

Underground hydrogen (H 2 ) storage (UHS) and carbon dioxide (CO 2 ) geo-storage (CGS) are prominent methods of meeting global energy needs and enabling a low-carbon global economy. The pore-scale distribution, reservoir-scale storage capacity, and containment security of H 2 and CO 2 are significantly influenced by interfacial properties, including the equilibrium contact angle ( θ E ) and solid-liquid and solid-gas interfacial tensions ( γ S L and γ S G ). However, due to the technical constraints of experimentally determining these parameters, they are often calculated based on advancing and receding contact angle values. There is a scarcity of θ E , γ S L , and γ S G data, particularly related to the hydrogen structural sealing potential of caprock, which is unavailable in the literature. Young's equation and Neumann's equation of state were combined in this study to theoretically compute these three parameters ( θ E , γ S L , and γ S G ) at reservoir conditions for the H 2 and CO 2 geo-storage potential. Pure mica, organic-aged mica, and alumina nano-aged mica substrates were investigated to explore the conditions for rock wetting phenomena and the sealing potential of caprock. The results reveal that θ E increases while γ S G decreases with increasing pressure, organic acid concentration, and alkyl chain length. However, γ S G decreases with increasing temperatures for H 2 gas, and vice versa for CO 2 . In addition, θ E and γ S L decrease, whereas γ S G increases with increasing alumina nanofluid concentration from 0.05 to 0.25 wt%. Conversely, θ E and γ S L increase, whereas γ S G decreases with increasing alumina nanofluid concentration from 0.25 to 0.75 wt%. The hydrogen wettability of mica (a proxy of caprock) was generally less than the CO 2 wettability of mica at similar physio-thermal conditions. The interfacial data reported in this study are crucial for predicting caprock wettability alterations and the resulting structural sealing capacity for UHS and CGS. • The equilibrium contact angle ( θ E ) increases with pressure and organic concentration but decreases with temperature. • The solid-gas interfacial tension ( γ S G ) decreases with pressure and organic concentration but increases with temperature. • The solid-liquid interfacial tension ( γ S L ) and θ E decreases, whereas γ S G increases with increasing alumina nanofluid concentration. • Mica hydrogen wettability is less than mica CO 2 wettability in all physio-thermal conditions.

Nucleation Behaviors of Adipic Acid in Different Polarity Solvent Based on Metastable Zone Width

In this contribution, we experimentally determined the metastable zone width (MSZW) of adipic acid (AA) in different polar solvents to reveal the nucleation behavior. We performed analyses for different cooling rates, saturation temperatures and polar solvents. The findings showed that the MSZW increased as the cooling rate increased, or saturation temperature or polarity decreased. Here, we suggest that the hydrogen bond donor capacity decreases as the polarity of the solvent decreases, which weakens the solute and solvent interaction and makes the desolvation process more difficult during nucleation. Furthermore, we found that the MSZW is mainly determined by the cooling rate, when the cooling rate is large enough. On account of the classical nucleation theory, it was found that the sizes of the critical nucleus and Gibbs nucleation energy do not increase monotonously with increasing driving force. Moreover, this study confirms that solid–liquid interface tension is associated with crystallization driving force.

Combination of Universal Chemical Deposition and Unique Liquid Etching for the Design of Superhydrophobic Aramid Paper with Bioinspired Multiscale Hierarchical Dendritic Structure.

It is urgent and significant for the further development of superhydrophobic materials to exploit a facile, low-cost, scalable, and eco-friendly method for the manufacture of superhydrophobic materials with self-cleaning, antifouling, directional transportation, and other characteristics. Herein, an outstanding superhydrophobic material composed of a flexible microconvex aramid paper substrate, micron-scale cone-shaped copper, micro-nanoscale dendritic copper oxide, and hydrophobic copper stearate film has been successfully constructed through delicate architectural design and a convenient preparation approach. Based on the microstructure evolution and composition analysis results, it is revealed that the cone-shaped copper was etched into a dendritic copper oxide structure step by step from the top to bottom and from the outside to inside in an alkaline liquid environment. Moreover, by virtue of the compositional features and structural characteristics, the constructed superhydrophobic material showcased a high contact angle (CA), low sliding angle (SA), high porosity, low surface free energy, and adhesion work. Meanwhile, the dendritic microstructure analysis, the calculation of solid-liquid interfacial tension, and the force analysis of water droplets jointly revealed the mechanism of the bounce and merged bounce of water droplets. Finally, this superhydrophobic material has the functions of self-cleaning, antifouling, and directional transportation, especially by controlling the deformation of the material to realize the transportation of water droplets in a specified direction.