Dispersed Droplets Research Articles

Assessing impact of intermittent window opening strategies on pathogen-laden droplet dispersion in a coach bus

Assessing impact of intermittent window opening strategies on pathogen-laden droplet dispersion in a coach bus

Modeling and simulation of air-water upward annular flow characteristics in a vertical tube using CFD

Annular flow refers to a special type of two-phase flow pattern in which liquid flows as a thin film at the periphery of a pipe, tube, or conduit, and gas with relatively high velocity flows at the center of the flow section. This gas also includes dispersed liquid droplets. The liquid film flow rate continuously changes inside the tube due to two processes-entrainment and deposition. To determine the liquid holdup, pressure drop, the onset of dryout, and heat transfer characteristics in annular flow, it is important to have proper knowledge of flow characteristics. Especially a better understanding of entrainment fraction is important for the heat transfer and safe operation of two-phase flow systems operating in an annular two-phase flow regime. Therefore, the objective of this work is to develop a computational model for the simulation of the annular two-phase flow regime and assess the various existing models for the entrainment rate. In this work, Computational Fluid Dynamics (CFD) in ANSYS FLUENT has been applied to determine annular flow characteristics such as liquid film thickness, film velocity, entrainment rate, deposition rate, and entrainment fraction for various gas-liquid flow conditions in a vertical upward tube. The gas core with droplets was simulated using the Discrete Phase Model (DPM) which is based on the Eulerian-Lagrangian approach. The Eulerian Wall Film (EWF) model was utilized to simulate liquid film on the tube wall. Three different models of Entrainment rate were implemented and assessed through user-defined functions (UDF) in ANSYS. Finally, entrainment for fully developed flow was determined and compared with the experimental data available in the literature. From the simulations, it was obtained that the Bertodano correlation performed best in predicting entrainment fraction and the results were within the ±30 % limit when compared to experimental data.

Transient charge-driven 3D conformal printing via pulsed-plasma impingement

Seamless integration of microstructures and circuits on three-dimensional (3D) complex surfaces is of significance and is catalyzing the emergence of many innovative 3D curvy electronic devices. However, patterning fine features on arbitrary 3D targets remains challenging. Here, we propose a facile charge-driven electrohydrodynamic 3D microprinting technique that allows micron- and even submicron-scale patterning of functional inks on a couple of 3D-shaped dielectrics via an atmospheric-pressure cold plasma jet. Relying on the transient charging of exposed sites arising from the weakly ionized gas jet, the specified charge is programmably deposited onto the surface as a virtual electrode with spatial and time spans of ~mm in diameter and ~μs in duration to generate a localized electric field accordantly. Therefore, inks with a wide range of viscosities can be directly drawn out from micro-orifices and deposited on both two-dimensional (2D) planar and 3D curved surfaces with a curvature radius down to ~1 mm and even on the inner wall of narrow cavities via localized electrostatic attraction, exhibiting a printing resolution of ~450 nm. In addition, several conformal electronic devices were successfully printed on 3D dielectric objects. Self-aligned 3D microprinting, with stacking layers up to 1400, is also achieved due to the electrified surfaces. This microplasma-induced printing technique exhibits great advantages such as ultrahigh resolution, excellent compatibility of inks and substrates, antigravity droplet dispersion, and omnidirectional printing on 3D freeform surfaces. It could provide a promising solution for intimately fabricating electronic devices on arbitrary 3D surfaces.

Impact of wave action on the entrainment rate and droplet size of oil

Oil dispersed on the water surface undergoes fragmentation into droplets, subsequently entering the water column under wave action. The oil entrainment rate and the droplet size distribution (DSD) significantly influence the subsequent migration and transformation of oil in the water column. A wave tank system was employed to investigate the impact of wave action on oil entrainment rate and DSD. The experimental results revealed that increased wave height and wave frequency facilitated the entry of oil into the water column and fragmented it into dispersed droplets. Relationships between oil entrainment rate and energy dissipation, as well as DSD, were established and supported by mathematical regression analyses. Non-linear regression analysis indicated that the cumulative frequency distribution of DSD adhered to the Log-Normal and Rosin-Rammler distributions. These findings contribute to a comprehensive understanding of natural oil dispersion and subsea transport, valuable for estimating the origin of oil spills.

Using urea-shifting to create a natural blue, antioxidant emulsifier from phycocyanin

Phycocyanin (PC) is an algae-derived blue protein that can serve as an antioxidant colorant and emulsifier. Urea was used as an emulsification aid by balancing PC's hydrophilic-lipophilic character and was removed by dialysis after emulsification processes. With increasing concentration, urea gradually dissociated and denatured the PC polymers. By using spectroscopic methods, the aromatic amino acids and chromophores appeared to fold inward, and the secondary helix structure devolved into the unordered structure. Structural changes caused the hydrophilic PC to become more hydrophobic, resulting in an increase of its emulsifying capacity with a concomitant cost to PC's natural blue color. The partially denatured PC increased the amount of PC surface adsorption at the O/W interface by 39.89% of adsorbing percentage and the O/W interfacial protein concentration was 1.56 mg m−2, resulting in finer and more dispersed emulsion droplets. Therefore, although the denaturation resulted in a partial weakening of the protein's antioxidant properties (from 7.70 to 5.54 nmol L−1 Trolox equivalent), the stabilized droplets allowed the emulsions to exhibit higher apparent antioxidant properties (from 7.80 to 7.87 nmol L−1 Trolox equivalent). In the 37 °C storage stability evaluation, emulsions with lower starting urea concentrations remained blue longer, while those with higher starting urea concentrations remained more stable to long-term storage and showed lower oxidation levels. The urea concentration of 5 M was chosen because it maintained a relatively stronger blue color while keeping the emulsion more stable and protecting the oils from further oxidation.

The Emulsification and Stabilization Mechanism of an Oil-in-Water Emulsion Constructed from Tremella Polysaccharide and Citrus Pectin.

The objective of this study was to investigate the feasibility of the mixture of tremella polysaccharide (TP) and citrus pectin (CP) as an emulsifier by evaluating its emulsifying ability/stability. The results showed that the TP:CP ratio of 5:5 (w/w) could effectively act as an emulsifier. CP, owing its lower molecular weight and highly methyl esterification, facilitated the emulsification of oil droplets, thereby promoting the dispersion of droplets. Meanwhile, the presence of TP enhanced the viscosity of emulsion system and increased the electrostatic interactions and steric hindrance, therefore hindering the migration of emulsion droplets, reducing emulsion droplets coalesce, and enhancing emulsion stability. The emulsification and stabilization performances were influenced by the molecular weight, esterified carboxyl groups content, and electric charge of TP and CP, and the potential mechanism involved their impact on the buoyant force of droplet size, viscosity, and steric hindrance of emulsion system. The emulsions stabilized by TP-CP exhibited robust environmental tolerance, but demonstrated sensitivity to Ca2+. Conclusively, the study demonstrated the potential application of the mixture of TP and CP as a natural polysaccharide emulsifier.

Assessing charge accumulation and flashover phenomena on silicone rubber surface exposed to salt-containing droplets under direct current voltage

In damp and salt-fog environments, silicone rubber composite insulators are prone to forming dispersed droplets that absorb airborne salt nuclei, leading to charge accumulation and potentially causing flashovers that threaten transmission line stability. Regrettably, these concerns have not yet received sufficient attention from relevant researchers. This study examines the surface charge accumulation and flashover characteristics of silicone rubber insulators with droplets of varying electrical conductivity. The droplets can fix charges, as the conductivity of droplets on insulator surfaces increases, the migration rate of surface charges accelerates, causing distortion of the electric field and a significant increase the area of high-density charge regions on the sample surface. Compared with dry surfaces, increasing the equivalent salt density of salt-containing droplets attached to the surface from mild to severe (with conductivity increasing from 800 μS/cm to 2800 μS/cm) leads to a 25 %-40 % increase in the average surface charge density. After adsorbing charges, the salt droplets shorten the discharge development path, making it easier to trigger interface discharge. Compared with dry surfaces, the average flashover voltage of the salt droplets is reduced by at least 30 %. This study offers valuable analysis on charge accumulation and flashover for silicone rubber insulators in salt-fog environments.

Topological isomerism design of Demulsifiers: A fusion of molecular dynamics simulation and experiment

Demulsifiers are crucial for enhancing crude oil extraction and transportation efficiency by facilitating the separation of oil–water emulsions. However, research conducted on the design and synthesis of demulsifiers based on the results of molecular dynamics simulation remains scarce. Herein, we designed eight block polyethers, and explored their interfacial behaviors at the oil–water interface via molecular dynamics simulation. Correspondingly, eight block polyether demulsifiers were synthesized, and their interface properties were tested. The simulation results were consistent with the experimental results, indicating that the energy of simulation systems could be efficiently reduced by designed molecules, and that the prepared demulsifiers with the same structure could achieve effective demulsification correspondingly. Based on the simulation and experimental results, a “hand-shaped” demulsification mechanism model was proposed. The demulsifiers with hydrophobic “palm” and hydrophilic “fingers” demonstrated a more efficient performance in demulsification. The hydrophobic “palm” was stable in the continuous oil phase, and the hydrophilic “fingers” could attract dispersed water droplets to aggregate, facilitating demulsification. The study also finds that longer hydrophilic “fingers” exert stronger molecular force. Combining molecular dynamics simulation and experiment significantly accelerates the development of new demulsifiers, highlighting the utility of this approach in the research on demulsifiers.

Lagrangian statistics of concentrated emulsions

The dynamics of stabilised concentrated emulsions presents a rich phenomenology including chaotic emulsification, non-Newtonian rheology and ageing dynamics at rest. Macroscopic rheology results from the complex droplet microdynamics and, in turn, droplet dynamics is influenced by macroscopic flows via the competing action of hydrodynamic and interfacial stresses, giving rise to a complex tangle of elastoplastic effects, diffusion, breakups and coalescence events. This tight multiscale coupling, together with the daunting challenge of experimentally investigating droplets under flow, has hindered the understanding of concentrated emulsions dynamics. We present results from three-dimensional numerical simulations of emulsions that resolve the shape and dynamics of individual droplets, along with the macroscopic flows. We investigate droplet dispersion statistics, measuring probability density functions (p.d.f.s) of droplet displacements and velocities, changing the concentration, in the stirred and ageing regimes. We provide the first measurements, in concentrated emulsions, of the relative droplet–droplet separations p.d.f. and of the droplet acceleration p.d.f., which becomes strongly non-Gaussian as the volume fraction is increased above the jamming point. Cooperative effects, arising when droplets are in contact, are argued to be responsible of the anomalous superdiffusive behaviour of the mean square displacement and of the pair separation at long times, in both the stirred and in the ageing regimes. This superdiffusive behaviour is reflected in a non-Gaussian pair separation p.d.f., whose analytical form is investigated, in the ageing regime, by means of theoretical arguments. This work paves the way to developing a connection between Lagrangian dynamics and rheology in concentrated emulsions.

Characteristics of droplet dispersion and interpersonal exposure in indoor and outdoor dining areas of urban street: Elementary numerical investigations

Indoor and outdoor dining areas are special spaces where people generally sit close and talk face-to-face for a long time (∼hour). Semi-open dining area is of popularity among them, one of the reason is the thoughts that outdoor dining area have experienced small infectious risks, even though this opinion has not been thoroughly validated yet. As a novelty, this study conducts CFD simulations to investigate droplet dispersion and face-to-face exposure risk of customers in the indoor and outdoor dining areas of typical street canyons (H/W = 1) by coupling indoor/outdoor airflows. Different scenarios are considered including index patient locations, the setting of the desk isolation board (DIB, HDIB = 0.6 m or 1.2 m), and the outdoor semi-open street roof (SSR).Results show that indoor dining spaces with single-sided ventilation experience one-order poorer ventilation (net escape velocity NEV∼0.036 m/s) and subsequently 10–200 times higher face-to-face droplet trap fraction than those in outdoor dining areas (NEV∼0.407 m/s, TF∼3–102 ppm). Indoor desk isolation board can decrease face-to-face TF by 50 %, but in outdoors, TF without desk-isolation board is 6.5 ppm for 50 μm droplet and this value changes little or slightly increases as HDIB is 0.6 m (∼8.9 ppm) or 1.2 m (∼7.7 ppm), indicating DIB seems not helpful to reduce airborne exposure risk in outdoors. Moreover, the setting of an outdoor semi-open street roof (SSR) may reduce NEV in the indoor or outdoor dining area by half or 90 % respectively. Therefore, SSR may raise indoor and outdoor customers' face-to-face exposure risk (e.g. TF) by hundreds of times and seventy times respectively.

Development of test rig for optical diagnostics of cryogenic spray

Spray cooling is the primary method for conducting chilldown and fill of cryogenic propellant tanks. In a typical spray injection process, a liquid sheet/jet that exits the spray nozzle undergoes primary breakup by the development of surface instabilities. Droplets and ligaments generated after the primary breakup undergo secondary breakup to create a dispersion of droplets, which extract heat on impact with the tank walls. In the existing literature, there is limited data on the primary breakup of cryogenic sprays and their detailed visualization. Moreover, an insight into the spray characteristics such as primary breakup length and cone angle is vital to the development of computational models. In this investigation, optical diagnostics of cryogenic spray breakup and measurements of cryogenic spray characteristics have been conducted. Liquid nitrogen is the selected cryogen for the present analysis. To capture the transient nature of spray breakup after the injection, a novel shadowgraph technique is developed to photographically freeze the spray motion. Cryogenic spray characteristics such as cone angle and primary breakup length are obtained from the shadowgraph. In addition, droplet velocity measurement using Particle Image Velocimetry is explored. The comprehensive experimental dataset obtained herein not only provides insights into the mechanism of spray formation for cryogenic fluids but also helps in designing of spray cooling system for tank chilldown.

Insights on droplet drift and effective utilization of pesticide in “Third Pole”：Qinghai-Tibet Plateau of China

Crop protection pesticide spraying aims to greatly improve the utilization rate of pesticides. Controlling pesticides deposition requires a thorough understanding of the spatial behaviour of spray droplets.The Qinghai-Tibet Plateau, which is the headwaters of three largest water resources (Yangtze, Yellow and Lancang) in China, has exceptionally unique climatic characteristics. The goal is to reduce the amount of pesticides entering water resources. The wind tunnel experiment was used to validate the discrete phase method for tracking the trajectories. Cooperation between the smaller and larger droplets (greater than 150 μm) in the dense area around the nozzle can undoubtedly enhance the initial dispersion of droplet sizes. Droplet coalescence, which lowers the proportion of readily dispersed droplets, can greatly boost droplet deposition onto the target location.The crucial drift height is presented and clarified when droplets gradually disperse by identifying the descending length at which efficiency of mass transit starts towards decrease off quickly. The pesticide transport efficiency will not be enhanced by reducing the initial relative spread of droplets if the actual spray height surpasses the crucial drift height, and may even worsen drift loss. The temperature and relative humidity of the air have a greater influence on the evaporation losses of droplets smaller than 150 μm. In addition to providing information about pesticide spraying, the results of studies on droplet drift behaviors also suggest a method for controlling drift.

Comparison through a CFD approach of static mixers in an emulsification process

Emulsions, characterized by droplet dispersions of immiscible liquids in a continuous phase, are often found in many diverse fields of the chemical industry. The energy needed to break these droplets can be sourced from mechanical agitators in stirred tanks, active mixers like pulse-flow mixers, and ultrasonic mixers. However, static mixers serve as a convenient alternative due to their typically lower maintenance costs and increased resistance to failures. Static mixers are available in diverse shapes and dimensions, with two widely used types being the Kenics Static Mixers and the Sulzer Static Mixers. While these two static mixers have been extensively studied in the literature in terms of pressure drop and mixing efficiency, to the best of the authors’ knowledge there is no study comparing the two in emulsification processes. This work aims to compare the performance of these static mixers in the production of emulsions by employing a Computational Fluid Dynamics approach. Results showed that the Sulzer Static Mixers allow to obtain higher values of turbulent energy dissipation, which in turn leads to smaller droplet diameters.

Impact mechanism of active nanofluid on oil–water two-phase seepage during and after fracturing fluid invasion in tight oil reservoirs

Due to damage caused by fracturing fluid invasion, tight oil reservoirs exhibit slow post-hydraulic fracturing production recovery and low productivity. This study investigates the impact of a nanoclay-based active agent system on oil–water two-phase flow during and after fracturing fluid invasion, emphasizing its potential for enhancing recovery in tight oil reservoirs. Laboratory experiments using crude oil and natural core samples analyze the mechanism of how nanofluids affect oil–water distribution and flow characteristics during fracturing fluid invasion and oil recovery stages. Results show that nanofluids rapidly disrupt the emulsified state of “water-in-oil” emulsions, reducing emulsion viscosity by 84.19% and oil–water interfacial tension by two orders of magnitude, facilitating oil droplet dispersion and deformation and altering the wettability of oil-wet rock surfaces to aid crude oil detachment. Nanofluids increase the accessible volume of the water phase in pores and throats, enlarging flow paths for fracturing fluid flowback and oil recovery. The oil recovery process post-fracturing fluid invasion is delineated into three stages: substantial fracturing fluid flowback in the first stage, with nanofluids reducing the fluid return rate by 11.08% upon crude oil breakthrough; emulsion droplets occupying pores and throats in the second stage, with nanofluids reducing additional resistance during emulsion flow; and continuous oil production in the third stage, with nanofluids consistently and stably altering rock surface wettability to reduce invaded rock matrix resistance to oil flow. The findings of this study hold potential value in mitigating damage from fracturing fluid invasion in tight oil reservoirs.

Study on the effect of wax on hydrate formation in the presence/absence of span 80

Scholars have been unable to arrive at a consistent verdict on the effect of wax on hydrate nucleation, as the influence of emulsifiers on the dispersion of wax in oil has been neglected. Accordingly, we discuss the effects of wax, span 80, and their coupling on hydrate nucleation utilizing CO2 as the hydrate guest molecule to clarify the precise role of wax on hydrate nucleation. It was discovered that the incorporation of either 10 wt% wax or 2 vol% span 80 prolonged the induction period, and their combined addition led to a longer induction period. This phenomenon indicates that wax and span 80 negatively impact on hydrate nucleation, and their combination strengthens this process. A combination of macroscopic and microscopic techniques was employed to illustrate the mechanism underlying the effect of wax on hydrate nucleation. The study found that both wax and span 80, as well as their coupling, facilitated the dispersion of water droplets in the oil. However, the waxes alone had a needle-like shape and could not entirely encase the water droplets, resulting in the aggregation of hydrate particles. While span 80 changes the shape of the wax, the coupling effect completely encapsulates the water droplets, preventing gas mass transfer and inhibiting hydrate nucleation. Furthermore, the wax stabilizes the structure of the span 80-containing emulsion, thus enhancing the anti-aggregation of span 80.

3D Printing of TPU-Liquid Metal Composite Inks for the Preparation of Flexible Sensing Electronics.

Direct 3D printing of liquid metal is difficult to form and easy to destroy. In this paper, we developed a 3D printed composite material consisting of a thermoplastic polyurethane (TPU) matrix and liquid metal (LM) dispersed droplets, and introduced the method for realizing 3D printed devices with this composite material: First, the LM is added to 10~50wt %TPU at 190~200 °C through ultrasonic blending to prepare blended ink. After solid cooling, the LM-TPU composite fiber with a diameter of 600 μm was prepared by Wellzoom desktop extruder at 190 °C at an extrusion speed of 400 mm/min. It has excellent elasticity, with a tensile limit of 0.637 N/m2, and the TPU could evenly wrap LM droplets. Finally, the LM-TPU fiber is 3D printed at 240 °C by using a 3D printer, and 2D/3D flexible electronic devices with heating and conductive functions could be prepared. The microcircuit has good electrical conductivity; after adding voltage, the circuit has heat release; it could be used as heating equipment to keep warm and used in various flexible wearable electronic products.

Simulation-based suggestions for lockdown rules in dense urban areas considering indoor-outdoor droplet transmission under natural ventilation conditions

Lockdown rules have been arbitrarily applied to curtail respiratory disease outbreaks without being certain about indoor-outdoor droplet transmission mechanisms and associated infection risks, causing enormous economic losses and arousing social unrest. This study addressed these issues by proposing lockdown rules for dense urban areas using computational fluid dynamics (CFD) simulations of indoor-outdoor droplet dispersion originating from various source locations in single-sided and cross-ventilated spaces of a six-story building in idealized urban areas with plan area densities (λp) of 0.25, 0.44, 0.59, 0.69, and 0.82. The findings suggest issuing lockdown orders based on the relative locations of the patient and vulnerable persons. For example, droplets exhaled by a patient on the upper and middle floors can enter the apartments on one or two floors below under single-sided ventilation, while the droplets are transmitted to the same level downstream spaces by cross-ventilation. Although pedestrians and building occupants pose no infection risk to each other in urban areas with λp = 0.25, they are both exposed to high droplet concentrations in dense urban areas with λp = 0.69 and 0.82. Therefore, this study recommends area lockdowns for dense urban areas to protect residents and pedestrians from virus-laden droplets carried by indoor-outdoor droplet transmission.

CFD-PBM coupled modeling of the liquid-liquid dispersion characteristics and structure optimization for Kenics static mixer

Kenics static mixers (KSM) are extensively used in industrial mixing–reaction processes by virtue of high mixing efficiency, low power homogenization and easy continuous production. Resolving liquid droplet size and its distribution and thus revealing the dispersion characteristics are of great significance for structural optimization and process intensification in the KSM. In this work, a computational fluid dynamics–population balance model (CFD–PBM) coupled method is employed to systematically investigate the effects of operating conditions and structural parameters of KSM on droplet size and its distribution, to further reveal the liquid–liquid dispersion characteristics. Results indicate that higher Reynolds numbers or higher dispersed phase volume fractions increase energy dissipation, reducing Sauter mean diameter (SMD) of dispersed phase droplets and with a shift in droplet size distribution (DSD) towards smaller size. Smaller aspect ratios, greater blade twist and assembly angles amplify shear rate, leading to smaller droplet size and a narrower DSD in the smaller range. The degree of impact exerted by the aspect ratio is notably greater. Notably, mixing elements with different spin enhance shear and stretching efficiency. Compared to the same spin, SMD becomes 3.7–5.8 times smaller in the smaller size range with a significantly narrower distribution. Taking into account the pressure drop and efficiency in a comprehensive manner, optimized structural parameters for the mixing element encompass an aspect ratio of 1–1.5, a blade twist angle of 180°, an assembly angle of 90°, and interlaced assembly of adjacent elements with different spin. This work provides vital theoretical underpinning and future reference for enhancing KSM performance.

Three-component deep eutectic solvent for revered-phase air-assisted liquid–liquid microextraction for the determination of furanic compounds in transformer oil by HPLC-UV

In this work, a revered-phase air-assisted liquid–liquid microextraction approach based on three-component deep eutectic solvent for pretreatment of petroleum oils was developed. The approach was utilized for the determination of furanic compounds in aged transformer oil by high-performance liquid chromatography with UV detection. The procedure assumed multiple aspiration of oil sample and deep eutectic solvent into a syringe and injection of the extraction mixture into an Eppendorf tube (11 instant extraction cycles). This process resulted in the formation of a cloudy solution, attributed to the dispersion of extraction solvent droplets into the oil sample. After centrifugation the obtained extract phase was introduced into a chromatographic system without additional purification and dilution. To establish the optimal microextraction procedure conditions, key parameters such as the extraction solvent composition, phase ratio and the number of extraction cycles were investigated. Cheap and available low viscosity deep eutectic solvent based on choline chloride, acetic acid and water provided the highest extraction recovery values (from 85 to 96 %). It was found, that acetic acid as precursor of extraction solvent acted key-role for maximum extraction recovery for all analytes. The phenomenon of the influence of hydroxyl groups in the structure of analytes on the extraction efficiency was revealed. Under optimal condition, the limits of detection were in the range from 3 to 6 μg L−1.

Heterogeneous wettability membrane for efficient demulsification and separation of oil-in-water emulsions

Single super-wetting membranes have been used to treat oily wastewater, but most membranes lack demulsification ability and often exhibit poor separation performance. Herein, we fabricate a desert beetle-like heterogeneous wettability membrane with a superhydrophilic fiber substrate and weakly hydrophilic discontinuous protrusions for demulsification and separation of oil-in-water emulsions. The unbalanced force formed by the difference in hydrophilicity between the substrate and protrusions promotes the demulsification of the emulsion. Additionally, the protrusions capture and gather dispersed oil droplets due to Laplace pressure, forming a layered oil slick. This synergistic effect overcomes the limitation of traditional size-sieving mechanism, enhances the separation performance, and avoids membrane fouling. The heterogeneous wettability membrane demonstrates a 99.8 % gravity-driven oil rejection for various oil-in-water emulsions with a permeability of 2600 L·m−2·h−1. It can also achieve effective separation of high viscosity crude oil emulsions without contamination. Furthermore, molecular dynamic simulations reveal that the heterogeneous wettability structure of the membrane surface promotes the demulsification and separation of emulsified oil droplets. And the presence of two hydration layers is found to be the main reason for the great antifouling property of the membrane. This study provides valuable insights for the design of separation membranes for oil-in-water emulsions and the advancement of separation technology.