Water-solid Interactions Research Articles

Molecular dynamics characterization of the interfacial structure and forces of the methane-ethane sII gas hydrate interface

The nucleation of gas hydrates is of great interest in flow assurance, global energy demand, and carbon capture and storage. A complex molecular understanding is critical to control hydrate nucleation and growth in potential applications. Molecular dynamics is employed combined with the mechanical definition of surface tension to assess the surface stresses controlling interfacial behavior. We characterize the interfacial tension for sII methane/ethane hydrate and gas mixtures for different temperatures and pressures. We find that the surface tension trends positively with temperature in a balance of water-solid and water-gas interactions. The molecular dipole shows the complexities of water molecule behavior in small, compressed pre-melting layer that emerges as a quasi-liquid. These behaviors contribute to the developing knowledge base surrounding practical applications of this interface.

Surface-induced water crystallisation driven by precursors formed in negative pressure regions

Ice nucleation is a crucial process in nature and industries; however, the role of the free surface of water in this process remains unclear. To address this, we investigate the microscopic freezing process using brute-force molecular dynamics simulations. We discover that the free surface assists ice nucleation through an unexpected mechanism. The surface-induced negative pressure enhances the formation of local structures with a ring topology characteristic of Ice 0-like symmetry, promoting ice nucleation despite the symmetry differing from ordinary ice crystals. Unlike substrate-induced nucleation via water-solid interactions that occurs directly on the surface, this negative-pressure-induced mechanism promotes ice nucleation slightly inward the surface. Our findings provide a molecular-level understanding of the mechanism and pathway behind free-surface-induced ice formation, resolving the longstanding debate. The implications of our discoveries are of substantial importance in areas such as cloud formation, food technology, and other fields where ice nucleation plays a pivotal role.

Influence of Water-Solid Interaction and Surface Charge on Thermal Resistance Length

Influence of Water-Solid Interaction and Surface Charge on Thermal Resistance Length

Electricity generation via metal oxide-air moist interaction

Harvesting electricity from ambient moisture and water droplets through the innovative technology of hydrovoltaics has lately gained attraction as it only requires water molecules' intrinsic energy and is applicable in different weather conditions. We present a device prototype for electricity generation from air humidity. The study investigates the complex interplay of water-solid interactions, focusing on band gap differences of n-type and p-type couple metal oxides and their performance in electricity generation. The research develops Moist-Electric Generators (MEGs) using ZnO as an n-type metal oxide with various p-type metal oxides (MnOx, CuO, and CoOx) on carbon paper substrates. Among these, the ZnO/CoOx MEG exhibits superior performance, producing an open circuit voltage of nearly 0.5 V, a current of around 9.5 µA for more than 7 days, with an areal and maximum power density of 1.48 µWcm2- and 4.5 µWcm2- at 95 % RH. Detailed characterization techniques, including XRD, XPS, and SEM, confirm the successful synthesis of ZnO and CoOx electrodes. The study demonstrates the sensitivity of the ZnO/CoOx MEG to changes in relative humidity and investigates its long-term stability. The results highlight the significance of water dissociation and minor redox processes for efficient energy generation, paving the way for advanced applications in renewable energy technologies.

Physicochemical properties of wheat granular flour and quality characteristics of the corresponding fresh noodles as affected by particle size

Wheat granular flour (GF) is highly nutritious due to low machining precision but the large particle size leads to poor processability. By reducing the particle size from 224 μm to 62 μm without sifting in the present study, flour chemical compositions, dough rheology, and fresh noodle qualities were tracked, and the underlying mechanism was preliminarily explored through the changes in corresponding dough's gluten quality, water–solid interaction, and microstructures. Results indicated that only moisture significantly decreased and damaged starch signally increased with the reduction in particle size. Compared with refined flour, all the GF samples had higher ash, dietary fiber, beneficial lipids, and intact endosperm cells. Noticeably, the GF samples with particle size from 91 μm to 68 μm developed higher gluten quality and quantity, stronger water-solids interplay, and optimal gluten networks; therefore, the resultant doughs displayed a super balance between viscosity and elasticity. Accordingly, the noodles possessed excellent consumer acceptability with higher water absorption, lower cooking loss, and higher smoothness and chewiness after optimum cooking. These observations provide a theoretical basis for wheat flour processing and the development of healthier wheat-based noodles using the GF as raw material.

Effects of Salt Content and Freeze-Thaw Conditions on Dynamic characteristics and its microscopic mechanism of Chloride Silty Clay

Generally, artificial ground freezing (AGF) technology is utilized to guarantee tunnel safety during construction. However, the soil structure changes significantly after freeze-thaw, resulting in uneven deformation of the tunnel under traffic loading from subway vibration. To solve this problem effectively, it is necessary to consider the combined impact of freeze-thaw, salt, and traffic loading damage that marine soft soil must withstand simultaneously. For this reason, cyclic triaxial test and NMR test were performed on the silty clay saturated with NaCl solution in this study. The influence of three main factors on dynamic properties has been thoroughly investigated, namely freeze-thaw, salt content, and confining pressure. According to cyclic triaxial test, the shape of the hysteresis loop of the specimens after freeze-thaw changed more significantly with increasing loading cycles. The dynamic elastic modulus was weakened by freeze-thaw, while improved by the addition of NaCl. Damping ratio was consistent with the dynamic elastic modulus law. It was worth noting that the different freezing temperatures (−10 °C, −20 °C and − 30 °C) had only a slight impact on dynamic elastic modulus, as well as damping ratio. Mathematical models were proposed to forecast the dynamic elastic modulus and damping ratio regarding marine soft clay. NMR test indicated that the addition of salt made the internal pore environment of the specimens tend to be consistent and enhanced the water-solid interaction. The increase in porosity resulted in the decrease in dynamic elastic modulus. The results have provided valuable insights into the mechanical characteristics of marine soft clay when AGF technology is applied.

Demarcating quality improvement mechanisms in fresh yellow alkaline noodles: Insights into water-solid interaction, gluten network development, and starch properties during noodles resting

This work explored, for the first time, the impact of noodles resting on the edible quality of fresh yellow alkaline noodles and demonstrated the promotion mechanism through analysis of physicochemical properties of principal components and microstructure of the noodles. According to the results, after resting for 18 h, fresh noodles exhibited reduced cooking loss and incresed water absorption. The chewiness and hardness of cooked noodles increased by 40.34% and 18.52%, respectively. An increase in the proportion of weakly bound water in the rested noodles was observed. indicating a more even distribution of moisture in noodles. Furthermore, a stronger gluten network structure and more organized secondary structure of gluten proteins were noted. The analysis of gluten network microstructure revealed a shorter average gluten network length, average protein width, higher branching rate, and lower terminal rate. Additionally, a higher peak viscosity of starch was found in the rested noodles.

Theoretical and Three-Dimensional Molecular Dynamics Study of Droplet Wettability and Mobility on Lubricant-Infused Porous Surfaces.

Profiting from their slippery nature, lubricant-infused porous surfaces endow with droplets excellent mobility and consequently promise remarkable heat transfer improvement for dropwise condensation. To be a four-phase wetting system, the droplet wettability configurations and the corresponding dynamic characteristics on lubricant-infused porous surfaces are closely related to many factors, such as multiple interfacial interactions, surface features, and lubricant thickness, which keeps a long-standing challenge to promulgate the underlying physics. In this work, thermodynamically theoretical analysis and three-dimensional molecular dynamics simulations with the coarse-grained water and hexane models are carried out to explore droplet wettability and mobility on lubricant-infused porous surfaces. Combined with accessible theoretical criteria, phase diagrams of droplet configurations are constructed with a comprehensive consideration of interfacial interactions, surface structures, and lubricant thickness. Subsequently, droplet sliding and coalescence dynamics are quantitatively defined under different configurations. Finally, in terms of the promotion of dropwise condensation, a non-cloaking configuration with the encapsulated state underneath the droplet is recommended to achieve high droplet mobility owing to the low viscous drag of the lubricant and the eliminated pinning effect of the contact line. On the basis of the low oil-water and water-solid interactions, a stable lubricant layer with a relatively low thickness is suggested to construct slippery surfaces.

Assessment of physicochemical parameters in argentinian Yerba Mate: Variability among different commercial brands

Yerba mate (YM) is a traditional plant-based product used in the preparation of hot beverages. YM is composed of dried leaves of Ilex paraguariensis A. St.-Hil., which are slightly toasted and milled. The present study analyses the variability of physicochemical sensorial-linked characteristics among six of the most renowned argentinian brands of YM. The samples consist of particles that were categorised as coarse (61%), intermediate (34%), and fine (5%). The average moisture and ash content were 7.8% and 5.4%, respectively, and their average loose bulk density was 285 g/L. The average colour parameters were L* = 49, a* = − 1.25, b* = 15.5, with the total colour difference being lower than 1 among samples of the same brand. On average, 1 g of YM absorb 2.6 g of hot water. This study introduced a description of the mechanical response to compression for YM. All samples underwent easy compression under small stresses owing to the material’s open structure; compressibility exhibited a positive correlation with moisture due to the plasticizing effect of water. The relaxation response of the YM was associated with its spatial arrangement and the presence of smaller particles that could facilitate elastic behaviour. Mate tea presented an average pH of 5.77 and a refractive index of 1.3340. The content of phenolics in mate teas significantly differs among the studied YM brands, with its average equivalent to 2.32 g of chlorogenic acid per litre and its antioxidant capacity equivalent to 15 mM of Trolox. The phenolic concentration showed a negative correlation with the quantity of fine fraction and moisture content, and positive correlation was observed with water absorption capacity. This suggests that greater microporosity of the material might facilitate increased water-solid interaction, consequently leading to higher phenolic extraction. These results may contribute to explaining certain sensory attributes observed in YM samples.

Precooking treatments affect the sensory and tensile properties of autoclaved recooked noodles via moisture distribution and protein structure.

To improve the quality of autoclaved recooked noodles (ARNs), this study explored the effects of precooking on the sensory and tensile properties of ARNs from the perspectives of changes in protein structure and water distribution. The results showed that the ARNs of two kinds of pretreatments (Boiling 2min, Boiling 1min+Steaming 2min) presented the best sensory quality (average score≥7.50) and high tensile properties (tensile distance≥45.24mm). After autoclaving and recooking, the proportion of tightly bound water increased by 11.30%-12.52%, resulting in stronger water-solid interaction. The results of laser confocal microscopy (CLSM) proved that a strengthened gluten network (protein percentage area≥40.28%; junction density≥10.96×10-4) appeared. Therefore, appropriate precooking treatment could effectively improve the sensory quality and tensile properties of ARNs by enhancing the tightly bound water ratio and strengthening the gluten network.

Study on the hydraulic classification characteristics of micron‐sized silica particles

AbstractThe present study investigates the motion characteristics of micron‐sized silica particles and how solid–water interaction regulates hydraulic classification. Two methods were evaluated for classifying micron‐sized silica particles. Using the small‐diameter cyclone for hydraulic classification of micron‐sized silica particles resulted in poor separation due to the short residence time of particles in the cyclone. Particle settling in still water showed that settling velocity, drag force, and virtual mass force increased with particle size, providing a basis for size classification. In the particle sedimentation process, drag force and gravity were dominant, with drag force reaching equilibrium with gravity in a fast time. The upward water flow was introduced to classify silica particles, with its superficial velocity between the settling terminal velocities of large and small particles, allowing large and small particles to flow to the overflow and underflow, respectively. The upward flow velocity was higher near the center of the flow field and lower near the wall, leading to a parabolic distribution pattern of the particle group along the radial position. In hydraulic sedimentation classification experiments of silica particles, the average particle size of the overflow sample was lower than that of the feed, and its size range was narrower, indicating the feasibility of hindered sedimentation by upward flow for classifying micron‐sized silica particles.

Using an improved SPH algorithm to simulate thermo-hydro-mechanical-damage coupling problems in rock masses

The Thermo-Hydro-Mechanical-Damage (THMD) process inside rock structures is a complex multi-field coupling problem, which is also regarded as the hotspot worldwide. In view of this situation, a fracture mark ξ is introduced to reflect the “active” or “failure” mode of Smoothed Particle Hydrodynamics (SPH) particles, which can simulate rock progressive cracking characteristics. The solid-water interaction modes and the damaged particles - water particles transformation algorithms are embedded into traditional SPH program to simulate the water-stress coupling problems. The heat conduction equations are programmed into SPH, which can reach the goal of modeling the temperature-stress coupling problems. Results show that: By coupling the parameter transformations between water and solid particles, the thermo-hydro-mechanical-damage simulation is then realized. Three numerical examples are carried out to validate the improved THMD method. Finally, an engineering numerical model of a typical tunnel is established, and the THMD coupling processes under complex conditions are simulated, which shows that the improved SPH method can simulate rock THMD multi-field coupling problems. The research results will help understanding the rock THMD coupling mechanisms, meanwhile, it can also promote the applications of SPH method into THMD modeling.

Atomic-scale engineering of cation vacancies in two-dimensional unilamellar metal oxide nanosheets for electricity generation from water evaporation

Water evaporation-induced electricity generation, as an emerging energy harvesting technology, has recently attracted extensive attention owing to its ability to harvest electricity directly from the natural water evaporation process. However, the crucial issue that has restricted its practical applications is the low power density and conversion efficiency presented thus far, which generally originated from the weak water-solid interaction between evaporation-induced water flow and nanostructured materials. Exploration of a regulatory approach that can enhance water-solid interaction at an atomic level is highly demanded. Herein, we propose the Ti vacancy engineering at the atomic scale in two-dimensional (2D) unilamellar titanium oxide (Ti1−δO2) nanosheets for efficient water evaporation-induced electricity generation. 2D Ti0.87O2 and Ti0.91O2 nanosheets with precisely controlled concentrations of Ti atomic vacancies are rationally designed. The water flow passes through the 2D gallery of nanosheets while the Ti atomic vacancies can effectively enhance the water-solid interaction between Ti1−δO2 nanosheets and water flow during the water evaporation process for electricity generation. As a result, a stable open-circuit voltage of ∼1.32 V for the hydrovoltaic device made of Ti0.87O2 nanosheets can be maintained for more than 250 h, outperforming those for the commercial TiO2 and Ti0.91O2 nanosheets. This work indicates a promising way to utilize defective 2D materials for hydrovoltaic technology.

Bio-inspired water-driven electricity generators: From fundamental mechanisms to practical applications

Harvesting water energy in various forms of water motion, such as evaporation, raindrops, river flows, ocean waves, and other, is promising to relieve the global energy crisis and reach the aim of carbon neutrality. However, this highly decentralized and distributed water energy poses a challenge on conventional electromagnetic hydropower technologies that feature centralization and scalization. Recently, this problem has been gradually addressed by the emergence of a myriad of electricity generators that take inspiration from natural living organisms, which have the capability to efficiently process and manage water and energy for survival in the natural competition. Imitating the liquid–solid behaviors manifested in ubiquitous biological processes, these generators allow for the efficient energy conversion from water–solid interaction into the charge transfer or electrical output under natural driving, such as gravity and solar power. However, in spite of the rapid development of the field, a fundamental understanding of these generators and their ability to bridge the gap between the fundamentals and the practical applications remains elusive. In this review, we first introduce the latest progress in the fundamental understanding in bio-inspired electricity generators that allow for efficient harvesting water energy in various forms, ranging from water evaporation, droplet to wave or flow, and then summarize the development of the engineering design of the various bio-inspired electricity generator in the practical applications, including self-powered sensor and wearable electronics. Finally, the prospects and urgent problems, such as how to achieve large-scale electricity generation, are presented.

Analysis of the effect of rolling speed on the texture properties of noodle dough from water-solid interaction, development of gluten network, and bubble distribution

To explore the influence of rolling speed on texture property of the noodle dough with 34% and 38% water additions, the water status, development of gluten network, and bubble distribution were studied. The dough sheets with 38% water addition had more uniform gluten network, and fewer bubbles, but lower hardness and tensile force because of the softening effect of water. As rolling speed increased, the water mobility increased, gluten network became weakened, and bubble number increased, leading to decreases in texture properties. Dough sheets with 38% water addition were less responsive to changes in rolling speed than that with 34% water addition because of the higher hydration of gluten. With increasing rolling speed, the total length and number of gluten network lines in length direction (rolling direction) reduced more than those in width direction, corresponding to the greater reductions in the texture properties of the dough sheet in length direction.

A substructure model for water-solid interaction under obliquely incident earthquake in canyon site

Structures crossing irregular topography features such as canyons and mountains may suffer from spatially varying ground motions due to topographic effect. In this paper, a two-dimensional substructure model of water-solid interaction in canyon site is proposed to study the effect of canyon topography on the seismic responses of water-canyon system, in which the wave radiation effect of infinite solid domains is simulated by the combined zigzag-paraxial boundary and the solid-water interaction is considered by interface conditions. Moreover, to verify the proposed substructure model, it is used to calculate the seismic responses of a V-shaped water-canyon system and a semi-circular water-canyon system under obliquely incident P-SV waves in homogeneous half space. Afterwards, we conduct the seismic analysis of water-canyon system. The results indicate that the amplification and reduction of ground motion is affected by geometric shape of canyons and water depth, and the maximum amplification of V-shaped water-canyon system can beyond an order of 200%, and the maximum amplification of semi-circular water-canyon system is less than 200%.

Submolecular Insights into Interfacial Water by Hydrogen-Sensitive Scanning Probe Microscopy.

ConspectusWater-solid interfaces have attracted extensive attention because of their crucial roles in a wide range of chemical and physical processes, such as ice nucleation and growth, dissolution, corrosion, heterogeneous catalysis, and electrochemistry. To understand these processes, enormous efforts have been made to obtain a molecular-level understanding of the structure and dynamics of water on various solid surfaces. By the use of scanning probe microscopy (SPM), many remarkable structures of H-bonding networks have been directly visualized, significantly advancing our understanding of the delicate competition between water-water and water-solid interactions. Moreover, the detailed dynamics of water molecules, such as diffusion, clustering, dissociation, and intermolecular and intramolecular proton transfer, have been investigated in a well-controlled manner by tip manipulation. However, resolving the submolecular structure of surface water has remained a great challenge for a long time because of the small size and light mass of protons. Discerning the position of hydrogen in water is not only crucial for the accurate determination of the structure of H-bonding networks but also indispensable in probing the proton transfer dynamics and the quantum nature of protons.In this Account, we focus on the recent advances in the H-sensitive SPM technique and its applications in probing the structures, dynamics, and nuclear quantum effects (NQEs) of surface water and ion hydrates at the submolecular level. First, we introduce the development of high-resolution scanning tunneling microscopy/spectroscopy (STM/S) and qPlus-based atomic force microscopy (qPlus-AFM), which allow access to the degrees of freedom of protons in both real and energy space. qPlus-AFM even allows imaging of interfacial water in a weakly perturbative manner by measuring the high-order electrostatic force between the CO-terminated tip and the polar water molecule, which enables the subtle difference of OH directionality to be discerned. Next we showcase the applications of H-sensitive STM/AFM in addressing several key issues related to water-solid interfaces. The surface wetting behavior and the H-bonding structure of low-dimensional ice on various hydrophilic and hydrophobic solid surfaces are characterized at the atomic scale. Then we discuss the quantitative assessment of NQEs of surface water, including proton tunneling and quantum delocalization. Moreover, the weakly perturbative and H-sensitive SPM technique can be also extended to investigations of water-ion interactions on solid surfaces, revealing the effect of hydration structure on the interfacial ion transport. Finally, we provide an outlook on the further directions and challenges for SPM studies of water-solid interfaces.

Surface wettability effect on heat transfer across solid-water interfaces

• Mechanisms of surface wettability effect on interfacial heat transfer are unraveled. • Hydrophilic surface promotes heat transfer through enhanced hydrogen-bonded network. • Molecular roughness with high biphasic contact area is beneficial to heat transfer. • Multiple and shallow vacancies are better than the deep but fewer ones on substrate. Although it has been found that the heat transfer across solid–liquid interface can be affected by the surface wettability, the underlying mechanism remains ambiguous. Herein non-equilibrium molecular dynamics simulations are conducted to unravel the microscopic mechanisms of heat transfer across solid-water interfaces. Specifically, two aspects of the solid surface wettability are investigated including modifying surface chemistry and introducing molecular roughness. We find that enlarging the solid-water interaction strength facilitates the formation of hydrogen-bonded network of water, hence enhancing the interfacial heat transfer. In addition, introducing molecular roughness can promote heat transfer by increasing the solid-water contact area. When the contact area remains the same, the substrates with multiple and shallow vacancies are more beneficial to heat transfer than those with deep but fewer vacancies. This work sheds insights into the mechanistic understanding of the heat transfer process and provides theoretical guidance for the development of efficient heat transfer devices.

A Comprehensive Method for Liquid-to-Solid Interactions.

Realistic real-time water-solid interaction has been an open problem in Computer Graphics since its beginnings, mainly due to the complex interactions that happen at the interface between solid objects and liquids, both when objects are completely or partially wet, or when they are fully submerged.In this paper we present a method that tackles the two main aspects of this problem, namely the buoyancy of objects submerged into fluids, and the superficial liquid propagation and appearance changes that arises at the interface between the surface of solid objects in contact with a liquids.For the first problem (buoyancy) a method is proposed to realistically compute the fluid-to-solid coupling problem. Our proposal is suitable for a wide spectrum of cases, such as rigid or deformable objects, hollow or filled, permeable or impermeable, and with variable mass distribution. In the case of permeable materials, which allow liquid to pass through the object, the presented method incorporates the dynamics of the fluid in which the object is submerged, and decouples the computation of the physical quantities involved in the buoyancy force of the empty object with respect to to the liquid contained within it. On the other hand, the visual appearance of certain materials depends on their intrinsic light transfer properties, the lighting present and other environmental contributions. Thus, complementing the first approach in this paper, a new technique is introduced to model and render the appearance changes of absorbent materials when there is liquid on their surface. Also, a new method was developed to solve the problem of the interaction between the object surface and liquids, taking advantage of texture coordinates. An algorithm was proposed to model the main physical processes that occur on the surface of a wet or wet solid object. Finally, we model the change in appearance that typically arise in most materials in contact with fluids, and an algorithm is implemented achieving real-time performance. The complete solution is designed taking advantage of superscalar architectures and GPU acceleration, allowing a flexible integration with the pipelines of current graphic engines.

Contribution of catechin monomers in tea polyphenols to the structure and physicochemical properties of wheat gluten and its sub-fractions

Wheat gluten with unique viscoelasticity is a key component that affects the quality of wheat products. In this study, the four typical catechin monomers (EGCG, EGC, ECG, EC) on the physicochemical and structural properties of both wheat gluten and its sub-fractions were systematically studied to clarify the dough/gluten enhancing ability of tea polyphenols. It was found that the two ester-type catechin monomers, EGCG and ECG, played a major role in improving gluten strength, which dramatically extended dough stability from 2.9 min to 18.4 and 7.6 min, respectively. Tea polyphenols, EGCG, and ECG monomers induced a more compact network structure for gluten and glutenin-rich fraction, and resulted in a well-organized and ordered network for gliadin-rich fraction. EGC and EC monomers presented no significant effect on the strength and structure of gluten. Tea polyphenols and the monomers can break the -S-S- bonds in glutenin aggregates, and promote their repolymerization during gluten formation. Unlike most gluten-enhancing agents, tea polyphenols improve gluten strength by enhancing hydrogen bonding and hydrophobic interactions, water-solid interaction, and the strong binding between ester-type monomers and proteins, instead of promoting -S-S- bonds formation.