Liquid Transport Research Articles

Bioinspired self-flowing wood chemical treatment

Wood has complex composition and structure, which make it difficult to achieve consistent and controllable treatment. A self-flowing process presented for the chemical treatment of wood is inspired by liquid transportation in trees during photosynthesis and tree growth, whereby liquid in the soil is brought through the natural vessels and/or fiber tracheids. In this process, wood lumbers are placed in a tank containing treatment chemicals such as preservatives, fire retardants, or reactive agents. Through an absorbent sheet bridging the untreated lumber to an overflow tank, the chemicals are drawn into the lumber under capillary force and pressure difference, so that continuous treatment occurs inside the wood. Effectiveness of the self-flowing process is evaluated and compared to conventional immersion and vacuum wood treatment methods. The self-flowing method is very effective for wood delignification, which is six and four times more effective than that from immersion and vacuum pressure treatment methods, respectively. The self-flowing process allows a more uniform wood treatment compared to that from the immersion and vacuum pressure methods. A mathematical model was developed to describe the self-flowing process. This model can accurately predict the treatment time required for achieving desired results under various conditions.

Electrically switched asymmetric interfaces for liquid manipulation.

External field driven fluid manipulation, in particular electric field, offers the advantages of real-time control and exceptional flexibility, rendering it highly promising for applications in microfluidic devices, liquid separation and energy catalysis. However, it is still challenging for controlled liquid transport and fine control of droplet splitting. Herein, we demonstrate a strategy to achieve direction-controlled liquid transport and fine droplet splitting on an anisotropic groove-microstructured electrode surface via an electrically switched asymmetric interface. The balance of asymmetric capillary force generated by microstructures and electro-capillary force is critical in determining directional liquid transport and fine droplet splitting. Asymmetric bubbles generated by liquid electrolysis form an asymmetric liquid-gas-solid interface and result in gradient liquid wetting behavior on the two neighboring electrode surfaces. The electric field further enhances the asymmetric wetting of a liquid droplet on the electrode surface, exhibiting electric field direction-dependent motion. Moreover, the groove-microstructured electrode surface can strengthen the liquid droplet anisotropic wetting and correspondingly refine the volume range of the splitting sub-droplet. Even unidirectional/bidirectional liquid droplet transport can be controlled in collaboration with the asymmetric groove-microstructure and electric field. Thus, this work provides a new route for liquid transport and droplet splitting, showing great potential in controllable separation, microreaction and microfluidic devices.

Antibacterial cellulose-based membrane with heat dissipation and liquid transportation for food packaging applications

Food spoilage, caused by fungi and bacteria, has drawn increasing attention due to the lack of suitable temperature and humidity control, resulting in food waste and health risks. It is still a great challenge to develop green packaging materials with excellent antibacterial activities and effective temperature/humidity control for food preservation. Herein, a new strategy is proposed to obtain food packaging material with antibacterial ability, heat dissipation, and liquid transportation functions. In this strategy, Zn-Al layered double hydroxide (LDH)@cellulose was obtained by extracting cellulose from sugarcane husks, followed by in-situ growth of LDH nanosheets on the surface of cellulose. Then, asymmetric structured packaging material, namely cellulose acetate/LDH@cellulose (CALC) membrane, was prepared by the combination of electrospinning and hydrophobic modification. The characterization results confirmed that the CALC membrane exhibits asymmetric surface structure and wettability properties, endowing heat dissipation and liquid transportation for food packaging applications. Due to the asymmetric reflectivity and infrared emissivity, the CALC membrane exhibited excellent heat dissipation properties with a surface temperature of 10.3℃, which is lower than that of commercial food packaging material. Furthermore, the excellent liquid transport properties of the CALC membrane are demonstrated by the fact that water can penetrate from the hydrophobic side to the hydrophilic side within 32s, providing the appropriate storage temperature and dry environment for foods. In addition, compared with PE film, the CALC membrane also has antibacterial properties and UV resistance, which is beneficial to improving the storage conditions for foods. This study shows that the developed CALC membrane and corresponding design strategy can be extended for the preparation of other packaging materials for applications in research and food industrial fields.

Transport of lithium droplets between two nonparallel iron plates: A molecular dynamics study

The use of bionic structures for the efficient and passive directional transportation of liquid droplets is crucial in numerous industrial applications. Compared with conventional fluids, liquid metals are stable under a wide range of environmental conditions owing to their excellent physicochemical properties. However, the directional transportation of liquid metals remains challenging. Herein, inspired by the pecking feeding mode of shorebirds, we performed a series of systematic molecular dynamics simulations to study the directional transport of liquid lithium (Li) between non-parallel iron (Fe) plates. The simulations demonstrate that cyclically closing and opening the Fe plates induces the movement of Li droplets toward the tip of the beak-shaped plate. Increasing the opening angle and applying a positive strain of the Fe plates can increase the transport velocity of the Li droplets. Nevertheless, the dissolution of Fe atoms in the liquid Li due to corrosion hinders the transportation of Li droplet across the Fe plate. We simulated the impact of two surface nanostructures on Li transport behavior and found that saw-tooth nanostructures decrease transport efficiency and lead to droplet breakup, whereas nanogrooves improve transport capacity by promoting the capillary effect. This work indicates that understanding the mechanism and influencing factors of liquid Li transport between non-parallel plates is essential for the design of bionic structures for the efficient transport of liquid metals.

Retinal organoid chip: engineering a physiomimetic oxygen gradient for optimizing long term culture of human retinal organoids.

An oxygen gradient across the retina plays a crucial role in its development and function. The inner retina resides in a hypoxic environment (2% O2) adjacent to the vitreous cavity. Oxygenation levels rapidly increase towards the outer retina (18% O2) at the choroid. In addition to retinal stratification, oxygen levels are critical for the health of retinal ganglion cells (RGCs), which relay visual information from the retina to the brain. Human stem cell derived retinal organoids are being engineered to mimic the structure and function of human retina for applications such as disease modeling, development of therapeutics, and cell replacement therapies. However, rapid degeneration of the retinal ganglion cell layers are a common limitation of human retinal organoid platforms. We report the design of a novel retinal organoid chip (ROC) that maintains a physiologically relevant oxygen gradient and allows the maturation of inner and outer retinal cell phenotypes for human retinal organoids. Our PDMS-free ROC holds 55 individual retinal organoids that were manually seeded, cultured for extended periods (over 150 days), imaged in situ, and retrieved. ROC was designed from first principles of liquid and gas mass transport, and fabricated from biologically- and chemically inert materials using rapid prototyping techniques such as micromachining, laser cutting, 3D printing and bonding. After computational and experimental validation of oxygen gradients, human induced pluripotent stem cell derived retinal organoids were transferred into the ROC, differentiated, cultured and imaged within the chip. ROCs that maintained active perfusion and stable oxygen gradients were successful in inducing higher viability of RGCs within retinal organoids than static controls, or ROC without oxygen gradients. Our physiologically relevant and higher-throughput retinal organoid culture system is well suited for applications in studying developmental perturbations to primate retinogenesis, including those driven by inherited traits, fetal environmental exposure to toxic agents, or acquired by genetic mutations, such as retinoblastoma.

Copper fiber wick with scaly fins fabricated by multi-tooth cutting for directional heat transfer

Wicks with directional liquid transport properties are the decisive factor in fabricating high-performance directional heat transfer devices. Aiming at the lack of wicks that can maintain directional liquid transport performance after high-temperature processes, sintered copper fiber wicks (SCFWs) with scaly fins were prepared. The copper fibers with scaly fins were fabricated by multi-tooth cutting and the additional driving force of scaly fins on ethanol was used to achieve directional capillary flow. The effects of scaly fin direction, sintering parameters, and porosity on the capillary performance of SCFWs were studied. The results show that the direction of scaly fins can adjust the liquid flow direction. The capillary performance parameter of SCFW3, with the same fin direction as the flow direction of ethanol, is 65.5% higher than that of SCFW1 with the opposite fin direction. Sintering temperature and holding time affect the formation of sintered necks and micropores, which affects the capillary performances of SCFWs. The effects of sintered necks on the capillary performances of SCFWs are more obvious than micropores on copper fibers. In addition, the relatively low porosity in the range of 70–80% helps improve the capillary performance of SCFWs. The SCFWs provide a feasible method for the fabrication of phase change heat transfer devices with directional heat transfer performances.

Structural Investigation of Chloride Ion-Containing Acrylate-Based Imidazolium Poly(Ionic Liquid) Homopolymers and Crosslinked Networks: Effect of Alkyl Spacer and N-Alkyl Substituents.

Understanding the interplay between the molecular structure of the ionic liquid (IL) subunit, the resulting nanostructure and ion transport in polymerized ionic liquids (PILs) is necessary for the realization of high-performance solid-state electrolytes required in various advanced applications. Herein, we present a detailed structural characterization of a recently synthesized series of acrylate-based PIL homopolymers and networks with imidazolium cations and chloride anions with varying alkyl spacer and terminal group lengths designed for organic solid-state batteries based on X-ray scattering. The impact of the concentrations of both the crosslinker and added tetrabutylammonium chloride (TBACl) conducting salt on the structural characteristics is also investigated. The results reveal that the length of both the spacer and terminal group influence the chain packing and, in turn, the nanophase segregation of the polar domains. Long spacers and terminal groups seem to induce denser polar aggregates sandwiched between more compact alkyl spacer and terminal group domains. However, the large inter-backbone spacing achieved seems to limit the ionic conductivity of these PILs. More importantly, our findings show that the previously reported general relationships between the ionic conductivity and the structural parameters of the nanostructure of PILs are not always attainable for different molecular structures of the IL side group.

In Situ Electrospinning of a Composite Janus Nanofiber Membrane with Antibacterial Activity, UV Radiation Protection, and Directional Liquid Transport Property

In Situ Electrospinning of a Composite Janus Nanofiber Membrane with Antibacterial Activity, UV Radiation Protection, and Directional Liquid Transport Property

Optimized Gas–Liquid Transport via Local Flow Field Management for Efficient Overall Water Splitting

Optimized Gas–Liquid Transport via Local Flow Field Management for Efficient Overall Water Splitting

Mask-Enabled Topography Contrast on Aluminum Surfaces.

Patterned solid surfaces with wettability contrast can enhance liquid transport for applications such as electronics thermal management, self-cleaning, and anti-icing. However, prior work has not explored easy and scalable blade-cut masking to impart topography patterned wettability contrast on aluminum (Al), even though Al surfaces are widely used for thermal applications. Here, we demonstrate mask-enabled topography contrast patterning and quantify the resulting accuracy of the topographic pattern resolution, spatial variations in surface roughness, wettability, drop size distribution during dropwise condensation, and thermal emissivity of patterned Al surfaces. The method uses blade-cut vinyl mask templates and a commercially available lacquer resin that serves as a polymer resist against etching. Programmable mask templates enable complex patterning of wettability and emissivity contrast with feature sizes down to ∼1.5 mm. As-fabricated patterned samples show a water contact angle (θ) contrast from <5° to 80° between etched and smooth zones, while patterned samples that are further coated with a hydrophobic promoter show θ contrast between 150° and 120° on etched and smooth zones, respectively. In addition to measuring this wettability contrast via contact angle goniometry, we use condensation visualization experiments to study the spatially controlled condensate morphologies and drop size distributions. These condensation studies demonstrate enhanced droplet shedding on the superhydrophobic regions of striped patterned surfaces compared to homogeneous superhydrophobic surfaces. Motivated by the role of thermal radiation in many phase change processes, we use infrared thermography to map topography-mediated thermal emissivity (ε) contrast between etched (ε ≈ 0.65) and smooth (ε ≈ 0.26) regions. Thus, our study provides a route for researchers to readily create complex and scalable topography-patterned Al surfaces for potential applications in vapor chamber thermal rectification, radiative cooling condensation heat transfer, and high-temperature Leidenfrost or film boiling processes.

Analysis of Liquid Sweat Transport in Underwear Combined with Multilayer Fabric Assemblies for Firefighter Outfits.

A firefighter's outfit consists of several layers with distinct properties and functions. These layers serve as barriers against external hazards but also impede the transport of sweat generated by the human body. As a result, sweat vapor often fails to transfer effectively from the body through the firefighter's protective clothing (FPC) to the environment. This can lead to sweat condensation on the firefighter's skin, causing discomfort. To enhance the physiological comfort of firefighters during firefighting and other rescue operations, it is essential to consider the transport of condensed sweat within the multilayer textile system comprising both the underwear and the FPC. In this study, 16 assembly variants were tested, combining four types of knitted fabrics for underwear with four types of multilayer textile sets designed for FPC. The liquid moisture transport properties of these assemblies were evaluated using the Moisture Management Tester (MMT290), an innovative instrument manufactured by SDL Atlas. The results demonstrated that the knitted fabrics effectively transport liquid sweat, whereas in the case of multilayer textile sets for FPC, liquid sweat transport is primarily confined to the inner layer adjacent to the skin. Furthermore, the findings indicate that by selecting an appropriate combination of knitted fabric for underwear and the inner layer of the FPC, it is possible to optimize liquid moisture transport in a firefighter's outfit.

Nonlinear linear dynamics and numerical analysis of a sloshing tank

Sloshing motion in liquids refers to the phenomenon of oscillation or agitation that occurs when a liquid is subjected to movement or disturbance. This can happen in containers, tanks, ships, or any other object that contains liquid and is subject to movement, such as acceleration, deceleration, turning or tilting. These oscillations can be caused by several factors, such as sudden changes in speed, changes in the direction of movement, winds, waves, or even internal movements of the liquid due to its own inertia. Sloshing can have significant effects in different contexts, such as naval engineering, liquid cargo transportation, storage tank projects, among others. Therefore, the study of sloshing is important to ensure the safety and stability of structures that contain moving liquids, as the forces resulting from these oscillations can affect structural integrity and even lead to accidents if they are not properly considered and controlled. Mathematical models and computer simulations are often used to predict and mitigate the effects of sloshing in different applications. Thus, this work investigates a mathematical model that describes a tank coupled to an electric motor, and therefore we determine the parameter space of the Lyapunov Exponent, basins of attraction, bifurcation diagrams and phase maps. These numerical analyzes are important to determine the range of parameters that diagnose chaos in the system.

Coupled vibration of composite riser under gas–liquid internal flow

In this paper, a dynamic prediction model for coupled vortex-induced vibration (VIV) of the composite marine riser in cross-flow (CF) and in-line (IL) directions under the action of gas–liquid two-phase internal flow is proposed. Then, numerical simulations are performed to discuss the influences of the ocean current velocity, internal flow velocity of gas–liquid mixed transportation, gas volume fraction, and fiber orientation angle on the dynamic characteristics of coupled VIV in CF and IL directions of a composite riser. Of particular interest in this process is the combined influence of multiple factors on coupled vibration characteristics of a composite riser. The results show that due to the influence of the gas–liquid two-phase internal flow and composite materials, when the current velocity is large, the vibration modes in the CF and IL directions are not approximately twice the relationship. When the fiber orientation angle and gas volume fraction are changed, the vibration of the riser in the CF direction will appear as traveling wave characteristics. At this time, the vibration amplitude in the CF direction will increase significantly, and the vibration periodicity will decrease. In addition, the CF bending stress of the riser is more sensitive to the change of parameters. There is the jump phenomenon, and the change of fiber orientation angle will aggravate this phenomenon.

A stand-alone and point-of-care electrochemical immuno-device for Salmonella typhimurium testing.

The rapid development of accurate and point-of-care diagnostic tools for foodborne diseases has made a massive impact in global health. Salmonella typhimurium (S. typhimurium) exemplifies an enteric pathogen, being a gram-negative bacteria responsible for several gastrointestinal and systemic illnesses. However, the existing electrochemical devices used to detect S. typhimurium have always been bulky or unfully integrated, implying a critical need for the design and development of stand-alone and point-of-care electrochemical sensors for portable S. typhimurium testing. Herein, we present the first instance of a stand-alone and point-of-care electrochemical immuno-device (SPEID) capable of conducting S. typhimurium analysis in actual specimens of purified drinking water that is mixed with S. typhimurium and watermelon juice that is mixed with S. typhimurium at point-of-care. The development of SPEID for S. typhimurium testing is achieved by overcoming substantial engineering challenges in seamlessly integrating an autonomous-transportation module (ATM) for microfluidic autonomous and directional liquid transportation, an immune-testing module (ITM) for S. typhimurium testing, and an electronic-integration module (EIM) for converting signal and wirelessly transmitting. The SPEID is a stand-alone one which possesses pump-free and cost-effective feature for measuring S. typhimurium at point of care.

Facile preparation of wood-based Janus membrane by hydrothermal ZnO with photoregulated wettability

This study developed a functional Janus wood (JW) membrane with designed wettability gradient through simple modification of balsa wood and evaluated its performance in liquid transport, fog collection, and oil–water separation. Zinc oxide (ZnO) nanoparticles were uniformly loaded into the wood membrane via vacuum impregnation and hydrothermal crystal growth, creating a stable hydrophobic layer. The single-side UV irradiation further induced the hydrophilic-hydrophobic gradually transitional structure. Uniform ZnO nanoparticle distribution was confirmed by SEM, XRD, XPS analyses, and so on. Increased surface area and targeted wettability differences were also detailly verified. UV treatment transformed ZnO to Zn(OH)2 altering the wettability transformation. The JW membrane demonstrated stable wettability under various pH, salinity, and abrasion conditions, with over 98.7% fog collection efficiency and reduced water evaporation. It also achieved over 99.6% separation efficiency for light and heavy oils with high flux and reusability. Due to its simple preparation process, cost effective, and excellent performance with durability, the JW membrane shows strong potential for applications in commercial environment. The study provided scenarios and solutions for multi-functional applications of sustainable wood and offered a new consideration for the design and preparation of Janus membranes.

Numerical study on gas-liquid transport uniformity in full-scale flow field of proton exchange membrane fuel cells

Distribution zone governs airflow transmission and distribution within large-scale flow field, which further affects the discharge of liquid water produced. This paper combines experimental validation and computational fluid dynamics (CFD) methods to elevate mass transfer coherence in full-scale flow field (375 cm2). For the first time, circulation number λ and drainage maldistribution (DM) are introduced to quantify variations in water and gas transport homogeneity attributable to the distribution zone. Effect on orientation and spacing of dot matrix, as well as main field structure are investigated. The results reveal that full-scale flow field inlet and outlet distribution zones manage the behavior of gas and liquid transport. Specifically, dot matrix flow field with an inclination angle α = 90° demonstrates superior flow uniformity, while α = 45° exhibits the fastest initial drainage rate. Optimal comprehensive mass transfer and drainage consistency are achieved with a vertical dot matrix spacing of S = 1.2 mm ∼ 1.5 mm, yielding the lowest maldistribution factor (MF) and DM number of 0.15 and 0.04 respectively. This configuration results in a maximum improvement of 58.4 % and 43.1 %. Notably, a novel aspect is that the drainage rate in full-scale flow field follows an exponential distribution, with peak efficiency factor R = 0.29 observed at α = 90°and S = 1.5 mm.

Risk assessment of flammable liquid transportation on waterways: An ontology-driven dynamic Bayesian network approach

Accidents involving the transportation of flammable liquids on waterways often lead to severe consequences, highlighting the importance of effective risk assessment under conditions of uncertainty. This paper presents a novel methodology for evaluating the risk associated with the spatiotemporal evolution of flammable liquid transportation on waterways. By leveraging ontology models and dynamic Bayesian networks, the approach involves analyzing factors that impact risk, constructing a standardized knowledge representation model, and mapping this onto a dynamic Bayesian network for comprehensive risk assessment. The methodology incorporates fuzzy theory and the Best-Worst Method to calculate probabilities within the Bayesian framework, enabling detailed analysis of factor impacts on transportation risk. A practical application is illustrated through the development of a dynamic risk evaluation model for octane transportation in the Yangtze River, demonstrating the model's capability to predict risk under varying conditions. This ontology-driven Bayesian network model provides a robust foundation for making informed management decisions in the transportation of flammable liquids, effectively addressing the challenges of semantic expression and inferencing under uncertainty to enhance safety in waterway transportation.

Utilizing Distribution of Relaxation Times Analysis for Water Content Management in Anion Exchange Membrane Fuel Cells

Amid escalating concerns over air pollution and energy scarcity, Anion Exchange Membrane Fuel Cells (AEMFCs) are increasingly recognized as a viable solution for power generation, offering high efficiency, and zero emissions. Water plays a critical role within these systems as a reactant, consumed at the cathode and generated at the anode. This process can lead to disparities in water content, potentially compromising the cell's performance. Therefore, it is imperative to maintain optimal water distribution to facilitate effective charge transport and enhance electrochemical reaction kinetics. Consequently, devising a robust water management strategy is essential to ensuring the sustained operation and longevity of AEMFCs.Characterizing the water conditions at the anode and cathode under various operational states (normal, drying, or flooding) is a pivotal step underpinning effective water management strategies. Electrochemical Impedance Spectroscopy (EIS) provides a valuable tool for examining various resistances associated with kinetics, mass transport, and ohmic losses across different operational timescales, thereby facilitating a detailed assessment of water transport dynamics. Traditional analyses of EIS data often depend on equivalent circuit models, which require predefined assumptions and the selection of initial components. However, this study adopted the Distribution of Relaxation Times (DRT) methodology for its exceptional capability to disaggregate components, enabling a more nuanced analysis of the polarization processes. The DRT methodology was applied to scrutinize the patterns of loss and variation within each polarization process under varying water flooding and drying conditions at the anode and cathode. Moreover, to deepen our comprehension of how water content influences mass transport and electrochemical reaction kinetics, a three-dimensional multi-physics model for AEMFCs was developed. This model comprehensively integrates considerations of water phase transitions, heat and mass transfer, as well as the transport of liquid and dissolved water, alongside electrochemical reactions. These efforts collectively forge a comprehensive and systematic framework to advance the application of the distribution of relaxation times in optimizing fuel cell performance.

Engineered Porous Transport Electrode for Proton Exchange Membrane Water Electrolysers

Proton Exchange Membrane Water Electrolysers (PEMWEs) is among the most promising approaches for green hydrogen production due to its rapid response times and high-power density operation, which make this electrolysis technology well-suited to harvest the intermittent power from wind and solar plants. Nevertheless, the commercial breakthrough of PEMWE technology continues to face barriers due to its costs [1]. The porous transport layer (PTL) is one of the PEMWE components that facilitates the transport of incoming water to the catalyst layer and the removal of the product gases, hence it is very important for good electrolyser performance. The state-of-the-art PTLs are manufactured by high temperature sintering of titanium fibers or powders, which can generate oxidized surfaces that will reduce PEMWE performance. Furthermore, titanium is listed by the European Union as a critical raw material since 2020 [2], so it is advisable to reduce the amounts of its use to produce PTLs. Additionally, the (micro)structure of state-of-the-art PTLs is not optimized for efficient liquid and gas transport in electrolysis. The manufacturing process plays a key role in achieving PTLs with optimized liquid and gas transport as well as reducing the usage of titanium.In this work, we used lithography to manufacture PTLs in which the (micro-)structure can be optimized and the usage of titanium metal can be significantly reduced. The lithography manufactured PTLs were used as substrates to produce catalyst-coated electrodes (CCE) with (ultra-)low loadings of iridium and the PEMWE performance was evaluated, respect to CCEs manufactured on commercial PTLs. We demonstrate similar performance of the CCEs manufactured with the engineered PTL, with the advantage of using less titanium and being able to tune the (micro-)structure of the component.

Water Permeability and Oxygen Transport Resistance of Hydrophilic and Hydrophobic Composite Microporous Layer Coated Gas Diffusion Layer

Water management is vital to enhance the performance of polymer electrolyte fuel cells (PEFCs). Previously, a hydrophilic and hydrophobic composite microporous layer (MPL) coated gas diffusion layer (GDL) was developed to promote robustness to humidity. It was proved that the composite MPL containing hydrophilic and hydrophobic pores in the same layer was effective in reducing the oxygen transport resistance from measured limiting current density under conditions of the cell temperature of 35°C, supplied gas relative humidity of 200% and flow rate of 1000 cm3 min-1. However, directly distinguishing the hydrophobic and hydrophilic microporous structures in the composite MPL is difficult. In this study, we try to clarify the ratio of hydrophobicity and hydrophilicity contributed to liquid water distribution and oxygen transport resistance.The water permeability test across hydrophilic, hydrophobic, and composite MPLs established the relationship between water flow rates under varying pressure conditions. The water breakthrough pressure obtained with the composite MPL was similar to that obtained with hydrophilic MPL. The composite MPL demonstrated two different rising slopes of the water flow rate. The hydrophilic pores caused the initial slope, which followed the tendency of hydrophilic MPL because water could readily pass through the hydrophilic pores. The following slope changed when the water supply pressure was high enough to pass the hydrophobic pores, and the slope was close to the pure hydrophobic MPL. The water flow rate obtained with the composite MPL was much higher than that obtained with the hydrophobic MPL. Based on the water permeability characteristics, it is considered that the hydrophobic and hydrophilic pores were separately generated in the composite MPL.To further clarify the contribution of hydrophobicity and hydrophilicity ratio to water transport, liquid water flow rate values for MPLs were derived from Darcy's law to fit the water permeability test data under identical pressure. According to the fitting results, a composition comprising 4% hydrophilicity and 96% hydrophobicity was determined to yield results consistent with the water permeability test, in which the actual composite MPL possessed 10 mass% PVDF, 7.5 mass% Nafion, 2.5 mass% TiO2 and 80 mass% carbon black.Based on this ratio, the Leverett function was employed to assess the distribution of liquid water saturation within hydrophobic, hydrophilic, and composite MPLs. In the composite MPL, liquid water saturation reached higher levels from the substrate to the hydrophilic pores in the MPL and almost remained constant from the MPL to the MPL/catalyst layer (CL) interface, indicating that the hydrophilic pores were utilized as water transport pathways. Conversely, hydrophobic pores in the MPL were not fully saturated, leaving most pores empty for gas transport. This balanced configuration of hydrophilicity and hydrophobicity substantially reduced the oxygen transport resistance. An additional assessment of the properties ratio was conducted, assuming that the cell operating current density was 3 A cm-2 and the water flow generated in the reaction was obtained. Under the same water flow rate conditions, increasing the hydrophilicity ratio from 0% to 4% resulted in decreased oxygen transport resistance, attributed to a reduction in water breakthrough pressure at the interface between the MPL and CL, facilitated the expelling of liquid water at the MPL/CL interface more effectively compared with a conventional hydrophobic MPL. However, further elevating the hydrophilicity ratio from 4% to 30% resulted in lower water breakthrough pressure but higher water saturation within the MPL. The saturated MPL possessed fewer pathways for gas transport, raising the oxygen transport resistance. Therefore, the inappropriate hydrophilicity and hydrophobicity ratio disrupted the optimal water-gas equilibrium, causing increased oxygen transport resistance. Through a comparative analysis of experimental and calculated data, the optimal formulation emerges, comprising 10 mass% PVDF, 7.5 mass% Nafion, 2.5 mass% TiO2, and 80 mass% carbon black, delineating hydrophilicity and hydrophobicity ratios of 4% and 96%, respectively.