Fluid-surface Interactions Research Articles

Molecular simulation of gas entrapment near a nanoscale cavity: The interplay of surface wettability, cavity shape, and gas type

Surface cavities play a crucial role in trapping and stabilizing gases, a phenomenon that can be used to facilitate applications in separation and drying processes. Understanding surface characteristics in relation to fluid-surface interactions is essential for designing interfacial properties that enable effective processes. In this work, we adopt a molecular simulation approach to investigate gas adsorption and entrapment in surface defects (cavities), focusing on the influence of surface wettability, cavity shape, and gas type. For this purpose, two types of silica-based surfaces with different levels of wettability (methylated and hydroxylated, with the former having lower water wettability), two cavity shapes with identical opening width and depth (V-shaped and square-shaped), and two types of gas (carbon dioxide and nitrogen) are considered. Our observations indicate that a stable gas nanobubble forms when a methylated surface combines with a square-shaped cavity, regardless of the gas type. In contrast, for hydroxylated surface, gas type becomes important; in a square-shaped cavity, nitrogen forms a stable nanobubble while CO2 is trapped in a monolayer fashion. The interfacial forces between the gas and surface which affects gas configuration near the surface, along with the gas molecules’ self-interaction manifested by solubility, are key to the different entrapment modes for N2 and CO2. Moreover, the square-shaped cavity exhibits better capability in trapping gas compared to the V-shaped cavity due to its higher surface area and smaller opening-to-interior ratio. The results of our molecular simulations can guide the design of surface features and processing systems to modify gas entrapment modes and stabilize nanoscale gas bubbles without altering thermodynamic conditions or fluid properties.

A Critical Review on the Advancements in Exploration and Production of Shale Gas

The exploration and production of shale gas have seen significant advancements in recent years, driven by the increasing global demand for clean energy sources. These advancements encompass the understanding of a wide range of areas, including the formation theory of shale gas reservoirs, evaluation methods, well drilling, completion, and simulation techniques. Innovative design, modelling, and field practices have been developed for shale gas well drilling and completion, as well as its production techniques. Furthermore, new simulation techniques, software, algorithms, and other tools have been introduced to improve the modelling and simulation of shale gas production. Experimental and simulation research in shale gas exploration, development, and production using hydraulic fracturing has also seen considerable progress. These advancements are contributing significantly to the global demand for clean energy sources with a promise to achieve sustainable development goals. This review work explores the exploration and exploitation of shale gas with a detailed description of multidisciplinary research efforts, providing valuable insights into shale reservoir/rock characterization and geo-mechanics, fluid-surface interactions, gas adsorption behaviours and single- and multi-phase flow mechanics. These advancements are not only increasing the efficiency and productivity of shale gas extraction but also paving the way to meet the future global energy demand while also contributing to the goal of achieving net-zero carbon emissions. The novelty of the review work is that it exhibits a combined qualitative and quantitative study of recent advancements in the sphere of exploration and production of shale gas reserves and its discoveries around the globe.

Ultrathin silicon nitride microchip for in situ/operando microscopy with high spatial resolution and spectral visibility.

Utilization of in situ/operando methods with broad beams and localized probes has accelerated our understanding of fluid-surface interactions in recent decades. The closed-cell microchips based on silicon nitride (SiNx) are widely used as "nanoscale reactors" inside the high-vacuum electron microscopes. However, the field has been stalled by the high background scattering from encapsulation (typically ~100 nanometers) that severely limits the figures of merit for in situ performance. This adverse effect is particularly notorious for gas cell as the sealing membranes dominate the overall scattering, thereby blurring any meaningful signals and limiting the resolution. Herein, we show that by adopting the back-supporting strategy, encapsulating membrane can be reduced substantially, down to ~10 nanometers while maintaining structural resiliency. The systematic gas cell work demonstrates advantages in figures of merit for hitherto the highest spatial resolution and spectral visibility. Furthermore, this strategy can be broadly adopted into other types of microchips, thus having broader impact beyond the in situ/operando fields.

Correlating Surface Chemistry to Surface Relaxivity via TD-NMR Studies of Polymer Particle Suspensions.

This study elucidates the impact of surface chemistry on solvent spin relaxation rates via time-domain nuclear magnetic resonance (TD-NMR). Suspensions of polymer particles of known surface chemistry were prepared in water and n-decane. Trends in solvent transverse relaxation rates demonstrated that surface polar functional groups induce stronger interactions with water with the opposite effect for n-decane. NMR surface relaxivities (ρ2) calculated for the solid-fluid pairs ranged from 0.4 to 8.0 μm s-1 and 0.3 to 5.4 μm s-1 for water and n-decane, respectively. The values of ρ2 for water displayed an inverse relationship to contact angle measurements on surfaces of similar composition, supporting the correlation of the TD-NMR output with polymer wettability. Surface composition, i.e., H/C ratios and heteroatom content, mainly contributed to the observed surface relaxivities compared to polymer % crystallinity and mean particle sizes via multiple linear regression. Ultimately, these findings emphasize the significance of surface chemistry in TD-NMR measurements and provide a quantitative foundation for future research involving TD-NMR investigations of wetted surface area and fluid-surface interactions. A comprehensive understanding of the factors influencing solvent relaxation in porous media can aid the optimization of industrial processes and the design of materials with enhanced performance.

Stochastic models of free-molecular nanopore flows.

In gas transport systems of the nanoscale, fluid-surface interactions become the main forces governing the evolution of the flow state. In ideal nanoscale systems, such as atomically smooth carbon nanotubes, the characteristic lengths reduce to such an extent that the non-equilibrium entrance region comprises a large proportion of the domain. In this regime, the added effective resistance induced by the non-equilibrium entrance region becomes large enough that classical effusion models break down. The mechanisms behind the resistance in this regime are still poorly understood. A stochastic model of interfacial resistance is developed here, which allows for the determination of the effective diffusion coefficient via a novel finite-difference solution. We use this method to model free-molecular gas flow through long nanotubes, showing that such non-equilibrium effects may be present in systems of length scales currently within manufacturing capabilities. Finally, this model is used to discuss gas separation through aligned carbon nanotube arrays, with a focus on the effect of membrane length on the separation of a H2-CH4 mixture.

Regulation of droplet impacting on superhydrophobic surfaces: Coupled effects of macrostructures, wettability patterns, and surface motion

Superhydrophobic surfaces have shown great application prospects due to their excellent water repellency in many applications involving fluid–surface interactions. As a ubiquitous fluid–surface interaction phenomenon, droplet impacting dynamics has a crucial effect on the application of superhydrophobic surfaces. In this Perspective, we summarize the basic process of droplet impacting on superhydrophobic surfaces and introduce the two most concerned parameters that describe the droplet impacting dynamics, i.e., the maximum spreading coefficient and the contact time. We then review two improvement strategies for superhydrophobic surfaces: one is to construct macrostructures and the other is to set wettability patterns on the surface. The former strategy shows great potential in reducing the droplet contact time, and the latter one can accurately regulate the behavior of impacting droplets. The motion of superhydrophobic surfaces also changes the droplet impacting dynamics due to the additional aerodynamic effect or energy input, which arouses attention recently. However, only the individual influence of each factor (e.g., macrostructures, wettability patterns, or surface motion) on the droplet impacting dynamics has been focused in literature, so we write this Perspective to emphasize the importance and urgency of studying the coupled effects of these three factors.

Direct Observation of the Vapor-Liquid Phase Transition and Hysteresis in 2 nm Nanochannels.

The characterization of fluid phase transitions in nanoscale pores remains a challenging problem that can significantly affect various applications, such as drug delivery, carbon dioxide storage, and enhanced oil recovery. Previous theoretical and experimental studies have shown that the fluid phase transition changes drastically when the fluid is confined within nanocapillaries with dimensions of <10 nm, potentially due to the dominance of fluid-surface interactions compared to bulk effects. However, due to challenges in performing experiments at the nanoscale, there have been limited experimental observations of the phase transition at this scale. Recent advances in lab-on-a-chip (LOC) technology have enabled the observation of many nanoscale phenomena. In this study, for the first time, we present the direct observation and visualization of n-butane vapor-liquid phase transitions in a 2 nm slit pore using LOC technology. Our experiments, for the first time, measured and directly visualized the deviation of the vapor-liquid phase transition pressure in a 2 nm slit pore compared to the associated unconfined or bulk value. We also measured the liquid-vapor phase transition pressure and observed a significant difference from the vapor-liquid phase transition pressure. We complemented our experimental observations with grand canonical ensemble Monte Carlo molecular simulations to understand the underlying molecular-level mechanisms.

Nanoconfined Fluid Critical Properties Variation over Surface Wettability

The characterization of nanoconfined fluid critical properties is critical for nanoconfined fluid phase behavior and flow capacity evaluation. To date, fluid–surface interaction strength is considered as the original cause for the shift of fluid critical properties, which is closely related to pore size and surface wettability. However, the majority of research is devoted to investigating the impact of pore size, while investigations about surface wettability on nanoconfined fluid critical properties are lacking. In order to fill the knowledge gap, in-depth investigations have been carried out to shed light on the wettability effect on nanoconfined fluid critical properties. First, focusing on the relative strength between fluid–fluid interactions and fluid–surface interactions, a robust correlation is proposed to relate surface contact angle, a macroscopic form of wettability effect, to critical property shift. Then, a linear correlation between the wettability effect and the adsorption thickness is established, and as a result, effective pore size can be described as a function of wettability as well. Finally, a prediction model for nanoconfined fluid critical properties is developed, and its reliability is well-clarified against 86 cases, collected from previous molecular simulation results or experiments. The results show the following: (a) The magnitude of the shift of fluid critical property can reach as high as 60%, dominating the variation characteristics of nanoconfined fluid phase behavior. (b) Both the pore size shrinkage and strong fluid-affinity surface are underlying mechanisms for suppressed critical properties at nanoscale. (c) The confined effect arisen from the cylindrical geometry is 2.24 times greater than that for slit nanopores, essentially stemming from the fluid force condition exerted by the pore surface.

Capillary-size flow of human blood plasma: Revealing hidden elasticity and scale dependence.

The dynamical mechanical analysis of blood generally uses models inspired by conventional flows, assuming scale-independent homogeneous flows and without considering fluid-surface boundary interactions. The present experimental study highlights the relevance of using an approach in line with physiological reality providing a strong interaction between the fluid and the boundary interface. New dynamic properties of human blood plasma are found: a finite shear elastic response (solid-like property) is identified in nearly static conditions, which also depends on the scale (being reinforced at small scales). The elastic behavior is confirmed by the induction, without heat transfer, of local hot and cold thermodynamic states evidencing a thermo-mechanical coupling in blood plasma so far known only in elastic materials. This finding opens new routes for medical diagnosis and device fabrication.

Cotton fabrics modified for use in oil/water separation: a perspective review

This article provides a perspective review on the use of modified cotton fabrics for oil–water separation. The principles of surface hydrophobicity of cotton fabrics are first described, from which the basis for producing superhydrophobic surfaces is presented. Then the preparation methods to convert hydrophilic cotton fabrics to hydrophobic fabrics are reviewed and discussed. Based on literature results the way to design novel preparation methods, the need to summarize testing protocols, and the comprehensive technoeconomic and sustainability analyses, are proposed. A demonstrative cotton fabrics test is used to reveal the significant role of conjugated fluid flows and surface interactions under different application scenarios for determining the separation efficiency of the oil–water mix.

Comprehensive Model for Oil Transport Behavior in Nanopores: Interactions between Oil and Pore Surface

A clear knowledge of fluid flow at the nanoscale will greatly contribute to recovery of unconventional oil/gas reservoirs. The distinction of nanoconfined fluid flow behavior with that of the bulk phase stems from strong fluid–surface interactions, which favor the emergence of slip phenomenon as well as spatial variation of viscosity and further affects transport capacity. However, elaboration of the above essential relationship remains challenging nowadays. Oil possesses a complex molecular structure and therefore leads to fruitful technical content regarding oil–surface interplay, posing a huge resistance to gaining a good understanding. Furthermore, the physical properties of tight oil reservoirs exhibit a wide variation range, including rock wettability, pore dimensions, and temperature, and their influences on oil transport are fascinating for in-depth investigation. The aim of this research is to establish a physics fully coupled model for nanoconfined oil transport behavior, which is capable of quantifying the contribution of each influential factor. The excellent agreement against the collected data from published literature claims the reliability of the proposed model. Results indicate the following: (i) A wide pore size can effectively suppress the nanoscale-induced influence on the oil flow behavior, including slip boundary and spatial viscosity variation features. (ii) The velocity distribution characteristic exhibits a plug-like shape as a result of a relatively large slip length by tuning surface wettability. (iii) Slip length shows a negative correlation with increasing temperature, and the feasibility of thermal recovery for tight oil reservoirs is not beneficial compared with that applied in conventional heavy oil reservoirs.

Characterization of the micro-scale surface roughness effect on immiscible fluids and interfacial areas in porous media using the measurements of interfacial partitioning tracer tests

This study presents a model-based methodology to characterize the surface roughness effect on immiscible fluids in porous media using the measurements obtained with the gas-phase interfacial partitioning tracer test (IPTT). The characterization approach captures how adsorbed wetting film configuration on grain surfaces influences fluid-fluid interfaces in unsaturated porous media. The method establishes a novel representation of surface and interface roughness that delineates the micro-scale fractal nature of grain surfaces and the fluid-surface interactions at these scales. The method was tested using reported experimental data for several soils. The results showed that the methodology was effective for natural porous media comprising a range of physical and geochemical properties. Comparisons between characterized parameters of different media revealed that micro-scale surface roughness was only partially correlated to soil texture properties. Images of the test media obtained with scanning electron microscopy (SEM) illustrates the complexity of micro-scale surface roughness, and its variability among different media. Tests with an organic liquid–water system validated the generalness of surface roughness properties generated by the model. The proposed methodology is anticipated to provide a means to characterize and quantify the effects of surface roughness on fluid-solid interaction and fluid-fluid interfacial area, which are critical to various environmental disciplines.

Mesoscopic method to study water flow in nanochannels with different wettability.

Molecular dynamics (MD) simulations is currently the most popular and credible tool to model water flow in nanoscale where the conventional continuum equations break down due to the dominance of fluid-surface interactions. However, current MD simulations are computationally challenging for the water flow in complex tube geometries or a network of nanopores, e.g., membrane, shale matrix, and aquaporins. We present a novel mesoscopic lattice Boltzmann method (LBM) for capturing fluctuated density distribution and a nonparabolic velocity profile of water flow through nanochannels. We incorporated molecular interactions between water and the solid inner wall into LBM formulations. Details of the molecular interactions were translated into true and apparent slippage, which were both correlated to the surface wettability, e.g., contact angle. Our proposed LBM was tested against 47 published cases of water flow through infinite-length nanochannels made of different materials and dimensions-flow rates as high as seven orders of magnitude when compared with predictions of the classical no-slip Hagen-Poiseuille (HP) flow. Using the developed LBM model, we also studied water flow through finite-length nanochannels with tube entrance and exit effects. Results were found to be in good agreement with 44 published finite-length cases in the literature. The proposed LBM model is nearly as accurate as MD simulations for a nanochannel, while being computationally efficient enough to allow implications for much larger and more complex geometrical nanostructures.

Coupled influences of particle shape, surface property and flow hydrodynamics on rod-shaped colloid transport in porous media

HypothesisNatural or engineered colloidal particles are often non-spherical in shape. In contrast to the widely-used “homogeneous sphere” assumption, the non-spherical particle shape is expected to alter particle–fluid-surface interactions, which in turn affect particle transport and retention. Experiments and SimulationsPolystyrene microspheres were stretched to rod-shaped particles of two aspect ratios (2:1, 6:1). The transport and retention behaviors of rods versus spheres were investigated in packed quartz sand columns and impinging jet systems. In parallel, a 3D trajectory model was employed to simulate particle translation and rotation, and to elucidate the role and underlying mechanisms of particle shape impact on transport. FindingsRods were observed to undergo rotating and tumbling motions in response to fluid shear from experiments and simulations. However, no distinct retention trends between rods and spheres were observed from column studies, despite BSA-coating on particles, Fe-coating on sand or velocity change. This was primarily due to the super-hydrophobic nature of colloid surfaces acquired from stretching process, which in hydrophilic sand columns, dominated particle–surface charge interactions. Simulations using colloids with randomly distributed charge patches qualitatively produced the observed insensitivity in retention respecting aspect ratio under low charge coverage (<30%). Hence, particle shape influences were strongly coupled with colloid surface properties and flow hydrodynamics.

Lattice Boltzmann simulation of immiscible three-phase flows with contact-line dynamics.

A multiphase lattice Boltzmann method is developed to simulate immiscible three-phase flows with contact-line dynamics. In this method, the immiscible three-phase flow is modeled by a multiple-relaxation-time color-gradient model, which not only allows for a full range of interfacial tensions but also can produce viscosity-independent results especially when the fluid-surface interactions are considered. To achieve the desired contact angles, a weighted contact angle model is utilized to obtain a relatively smooth transition of contact angle for each fluid, which is enforced through a geometrical wetting condition. This method is first validated by simulations of a Janus droplet resting on a surface for various contact angles and fluid properties and dynamic capillary filling of ternary fluids with different viscosity ratios. It is then used to simulate a Janus droplet on a substrate subject to Poiseuille flow. Results show that the droplet may undergo three typical modes, namely, two stable deformation modes and breakup mode, which depend not only on the inlet velocity but also on the fluid viscosity. The terminal velocity of moving droplet increases linearly with the inlet velocity in both stable modes only when three fluids do not differ much in their viscosities.

Bubble Point Pressures of Hydrocarbon Mixtures in Multiscale Volumes from Density Functional Theory.

Accurate characterization of the bubble point pressure of hydrocarbon mixtures under nanoconfinement is crucial to the prediction of ultimate oil recovery and well productivity of shale/tight oil reservoirs. Unlike conventional reservoirs, shale has an extensive network of tiny pores in the range of a few nanometers. In nanopores, the properties of hydrocarbon fluids deviate from those in bulk because of significant surface adsorption. Many previous theoretical works use a conventional equation of state model coupled with capillary pressure to study the nanoconfinement effect. Without including the inhomogeneous molecular density distributions in nanoconfinement, these previous approaches predict only slightly reduced bubble points. In this work, we use density functional theory to study the effect of nanoconfinement on the hydrocarbon mixture bubble point pressure by explicitly considering fluid-surface interactions and inhomogeneous density distributions in nanopores. We find that as system pressure decreases, while lighter components are continuously released from the nanopores, heavier components accumulate within. The bubble point pressure of nanoconfined hydrocarbon mixtures is thus significantly suppressed from the bulk bubble point to below the bulk dew point, in line with our previous experiments. When bulk fluids are in a two-phase, the confined hydrocarbon fluids are in a single liquid-like phase. As pore size increases, bubble point pressure of confined fluids increases and hydrocarbon average density in nanopores approaches the liquid-phase density in bulk when bulk is in a two-phase region. For a finite volume bulk bath, we find that because of the competitive adsorption in nanopores, the bulk bubble point pressure increases in line with a previous experimental work. Our work demonstrates how mixture dynamics and nanopore-bulk partitioning influence phase behavior in nanoconfinement and enables the accurate estimation of hydrocarbon mixture bubble point pressure in shale nanopores.

Revisiting methane absolute adsorption in organic nanopores from molecular simulation and Ono-Kondo lattice model

Accurate characterization of methane absolute adsorption in shale plays an important role in estimation of gas-in-place and prediction of well productivity. Previously, methane adsorption in shale nanopores was considered as a single-layer structure. However, it has been shown that due to strong fluid-surface interactions, methane can form transition zone between the first adsorption layer and free gas phase. Such transition zone can negatively affect the accuracy of absolute adsorption estimation from excess adsorption, which is the mostly measured adsorption property in experiments. In this work, we use grand canonical Monte Carlo (GCMC) simulations to characterize the transition zone and propose a modified adsorption model. Based on the modified adsorption model, which can explicitly take into account the effect of transition zone, we use Ono-Kondo (OK) lattice model with multilayer structure to calculate the absolute adsorption in each layer and compare with GCMC simulations. The newly proposed OK model with multilayer structure only needs layer width as an input and calculates the density in each layer and subsequently the absolute adsorption by fitting the excess adsorption. While OK model can significantly reduce calculation time, discrepancy from GCMC simulation can be less than 6%. Our work should provide important insights into the accurate characterization of methane absolute adsorption from experimental measurement.

Mesoscopic Investigation of an “Immiscible” Cyclohexane and Water Micro-mixture in Carbon Micropores by Contrast Variation Small-angle Neutron Scattering

Microspaces can simultaneously capture “immiscible” molecules such as cyclohexane and water due to fluid-surface interactions. We investigated the mesoscopic structure of cyclohexane and water co-adsorbed in carbon micropores using contrast variation small-angle neutron scattering (CV-SANS). The results show that cyclohexane tends to adsorb near the carbon surface and that both molecules form relatively small domains (<1 nm).

Condensation process and phase-change in the presence of obstacles inside a minichannel

In this paper, the condensation process, dynamic behaviour of fluid and phase-change inside a minichannel in the presence of square blocks are investigated numerically. The blocks are placed inside the minichannel with a tandem arrangement. The analysis is performed by using the lattice Boltzmann method based on the pseudo potential model. Fluid–fluid and fluid–surface interactions are fully considered in this model. Beside this, image processing is used to perform the validation and grid independent study. The effects of the distance between the blocks (D), the number of block (N) and the vertical blockage ratio (Z) on the condensation and nucleation processes are explored in details. The simulations are performed for different values of vertical blockage ratio ( $$0.05 \le Z \le 0.8$$ ), number of block ( $$0 \le N \le 4$$ ), and distance between the blocks (10Lu < D < 20Lu). It was found that the maximum value of the required time to transfer all the liquid phase to the bottom wall of the channel is occurred for the case of blocked channel. Moreover, the blocked channel phenomenon may be controlled with increase in N (number of block).

Nuclear magnetic resonance cryoporometry as a tool to measure pore size distribution of shale rock

Shale gas has recently emerged as an energy source that offers the opportunity for a number of countries for national energy independence and security. Shale gas is also less-carbon energy compared to coal and oil which can immediately serve as a blue bridge from carbon-intensive energy to renewables. In order to optimize the shale well productivity, characterization and quantification of shale pore architecture is one of the key parameters to model the gas flow behavior in subsurface shales. Transport properties, adsorption and diffusion, of shale gas are influenced, and sometimes even dominated by the pore structure of shales including the size, shape and connectivity of pore and pore networks. To accurately characterize the pore structure of shale is a challenging task in geoscience community. Various techniques, such as Scanning Electron Microscope (SEM), Mercury Intrusion Porosimetry (MIP) and Nitrogen Adsorption Method (NAM) and others, have been widely used to characterize pore structure of geomaterials. However, the built-in limitations of each technique were commonly reported in terms of applicability and accuracy due to the complexity and heterogeneity of the shale pore structure. Taking NAM and MIP for instance, these two techniques routinely involve material alteration which makes them potentially sensitive to contraction and pore interconnectivity, as well as the pressure-induced damage. The nuclear magnetic resonance cryoporometry, a novel and emerging technique, can probe pore size distributions from nano- to micro-scales based upon the depressed melting point of a confined liquid. Liquid and solid states in the NMR cryoporometry differ greatly in the transverse relaxation time, generally more than three orders of magnitude, which provides a relatively wide range for measuring pore size distribution. The resolution in NMR cryoporometry, are controled by the Gibbs-Thomoson coefficient of the liquid imbibed in a sample as well as the instrumental parameters such as temperature spread in the sample and temperature step size. In this study, two standard molecular sieves with pre-known pore structures were initially used to assess the applicability and the accuracy of this technique. Additionally, in order to evaluate the NMR cryoporometry results, both MIP and NAM were employed to characterize the pore structure on the same sample. We tested on both bulk matrix specimens and pulverized shale samples. The results demonstrate that MIP and NAM were comparable NMR cryoporometry and the pore size distributions were found to be similar across these techniques on both bulk and pulverized samples. The NMR cryoporometry was found to be a promising technique to analyze both total and effective porosities by measuring the same rock with pulverized and bulk sample, respectively. Besides pore size distribution and porosity, NMR cryoporometry has a unique feature to analyze larger and potentially arbitrarily-shaped objects and is applicable to samples in aqueous environment. Although it has not been widely used as a stand-alone technique, NMR cryoporometry has become a favored tool for calibrating NMR relaxometry due to its ability to provide accurate, reproducible, and unambiguous results. NMR cryoporometry is a promising and powerful tool when combined with other techniques including NMR relaxometry, spectroscopy, diffusion, and imaging. To summarize, NMR cryoporometry shows the applicability of pore characterization for porous absorbents and absorbates and it provides a wider spectrum of pore information including pore morphology, connectivity, heterogeneity, fluid-surface interactions, and the behavior of binary liquids. It is a promising and valuable technique for pore structure characterization for gas shales. In addition, it will help us improve the understanding of pore surface interactions and its related phenomena, and to discover the fundamental mechanisms behind the behavior of molecules in the confinement when combining with powerful computer modeling simulations.