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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. [ABSTRACT FROM AUTHOR]

Fractal branching networks are structures that are ubiquitous in nature, possessing multiple transport characteristics, and have been the subject of long-term attention by many researchers. Currently, in the field of textiles, research on the ability of tree-like structures to enhance the water transport property of fabrics is mostly focused on the thickness direction of the fabric. However, there is little research on the liquid water transfer rate in the horizontal direction. In this article, the water transport performance of liquid water in tree-like fractal nonwoven fabrics with different shapes (tree-like and rectangular) was investigated, and the liquid water transport rate was measured using the horizontal wicking method. It was found that when the sum of the cube of the branch width was equal to the cube of the main stem width, the water transport efficiency of liquid water in the fabric is optimal. At the same time, a summary of the experimental data was made by comparing the water transport property of fabrics with corresponding equal areas but different widths or heights. It was found that for nonwoven fabrics with the same area size, tree-like structures can transport liquid water to a farther distance in the same amount of time. Furthermore, the liquid water transport ability of tree-like nonwoven fabrics in the horizontal direction was simulated using finite element analysis in COMSOL Multiphysics, and the results were in good agreement with the experimental values. [ABSTRACT FROM AUTHOR]

Optimization of proton exchange membrane water electrolyzers (PEMWE) has become a focus of researchers looking for a reliable way to generate power. A vital component to PEMWE operation is the porous transport layer (PTL) on the anode side, which is where oxygen is produced. The PTL must allow water access to the catalyst layer and remove oxygen simultaneously. In this work, a previously developed imaging technique is used to generate bilayer PTL structures. A multiscale modeling approach was used to study the effect of a bilayer PTL on oxygen evolution and PEMWE performance. First, a micro scale model was used to predict oxygen transport pathways through different PTL structures. Results showed that the bilayer PTL results in higher oxygen saturation and faster oxygen transport through the PTL. Second, a macro scale model was used to predict performance using bilayer PTLs. Predictions showed potential values between 10 and 20 mV below single layer potential values. This points to the bilayer improving PEMWE operation. Findings from this work show how the addition of a mesoporous layer to a PTL substrate will improve oxygen transport and removal from the catalyst surface, which will improve PEMWE performance. [ABSTRACT FROM AUTHOR]

Limited attention has been paid to repellency and wettability‐confined transport of low‐surface‐tension liquids, such as oils, alcohols, and hydrocarbons. This is because repellency becomes very difficult for fluids with surface tension below 30 mN m−1. This situation is encountered in many engineering applications using organic liquids and thus, oleophobic surfaces are of high technological importance. In this work, a nanocomposite coating comprising of fluorinated silica micro‐ and nanoparticles (filler), a copolymer (binder), and traces of fluorinated polyhedral oligomeric silsesquioxane (additive, lowest surface‐energy crystalline material reported to date) is spray‐deposited on a surface pretextured by laser etching, a technique that requires no lithographic processing. The approach results in surfaces that can repel liquid hydrocarbons with surface tension as low as 21.14 mN m−1 and also hinder the spreading of heptane (19.74 mN m−1) at room temperature. The repellency of several organic liquids with surface tensions in the range of 19.7 – 27 mN m−1 is experimentally investigated and compared with water (baseline case). To study the effect of fluid properties, comparisons are performed between the distances traveled and the velocities of microliter droplets transported pumplessly on wedge‐shaped wettability‐patterned tracks that confine the liquids by the superoleophobic background surrounding the wettable tracks. [ABSTRACT FROM AUTHOR]

Abstract Limited attention has been paid to repellency and wettability‐confined transport of low‐surface‐tension liquids, such as oils, alcohols, and hydrocarbons. This is because repellency becomes very difficult for fluids with surface tension below 30 mN m−1. This situation is encountered in many engineering applications using organic liquids and thus, oleophobic surfaces are of high technological importance. In this work, a nanocomposite coating comprising of fluorinated silica micro‐ and nanoparticles (filler), a copolymer (binder), and traces of fluorinated polyhedral oligomeric silsesquioxane (additive, lowest surface‐energy crystalline material reported to date) is spray‐deposited on a surface pretextured by laser etching, a technique that requires no lithographic processing. The approach results in surfaces that can repel liquid hydrocarbons with surface tension as low as 21.14 mN m−1 and also hinder the spreading of heptane (19.74 mN m−1) at room temperature. The repellency of several organic liquids with surface tensions in the range of 19.7 – 27 mN m−1 is experimentally investigated and compared with water (baseline case). To study the effect of fluid properties, comparisons are performed between the distances traveled and the velocities of microliter droplets transported pumplessly on wedge‐shaped wettability‐patterned tracks that confine the liquids by the superoleophobic background surrounding the wettable tracks.

Polymer Electrolyte Membrane Water Electrolyzers (PEMWE) depend on a porous transport layer (PTL) to remove gaseous oxygen from the catalyst layer produced by the oxygen evolution reaction. PEMWEs are a promising technology for energy production and storage. In this work, five PTLs are reconstructed from X-ray Tomography Scans to create real three-dimensional structures. During the geometry generation process, porosity and a pore size distribution were calculated. Two different numerical models were used to simulate physical properties and expected performance for the different PTL samples. First, a two-phase flow micro-scale ex-situ model was used to predict in-plane permeability, through-plane permeability, and oxygen evolution. Adaptive meshing and adaptive time scale was used to produce a more accurate prediction of bubble interaction with the solid structure and liquid water. Second, a macro-scale model of a real PEMWE was used to predict performance behavior for each PTL sample. Outcomes from this work will provide insight into PTL design for more efficient PEMWE operation. • Porous Transport Layer is crucial for the removal of oxygen at the anode catalyst surface during PEMWE operation. • Oxygen saturation is dependent on the geometric structure of the Porous Transport Layer. • Oxygen evolution will follow the path of least resistance through the Porous Transport Layer. • Predictions of O 2 evolution through porous medias help pinpoint which material will be best suited for experimental testing. [ABSTRACT FROM AUTHOR]

Controlling surface wettability and directing the flow of working fluids have crucial implications in various natural and engineering contexts. Understanding the fundamental principles of wettability and directional wetting is essential for effectively leveraging these phenomena to enhance the performance of engineering systems, such as microfluidics or heat exchangers. This comprehensive review summarizes of previous research, emphasizing recent advances by categorizing the structures and working principles associated with directional wetting surfaces. The efforts of researchers who have employed diverse strategies to manipulate the wetting behavior of liquids through both passive and active control mechanisms are highlighted. Passive directional transport surfaces require no additional energy while enabling large‐scale and continuous fluid control. Conversely, active directional wetting surfaces offer enhanced flexibility and precise control of liquid movement. Furthermore, insights into recent studies that focused on practical applications are provided and the current challenges that need to be addressed are discussed. This study serves as a guide for future research directions on the development of directional wetting surfaces and offers valuable recommendations for practical implementation. [ABSTRACT FROM AUTHOR]

Sustainable power supply via triboelectric nanogenerator (TENG) is attractive for self‐powered actuation systems in the era of the Internet of Things (IoTs). Herein, a low‐power actuation scheme enabled by the multilayered TENG for piezoelectric actuators, including the stack, unimorph, and micro‐fiber composite (MFC) actuator, is reported. The working principles of TENG‐powered piezoelectric actuators and their displacement characteristics in direct current (DC) and alternating current (AC) modes are theoretically investigated. Compared with conventional high‐voltage power sources, the multilayered TENG delivers a maximum power of only 10.17 mW, providing a low‐power alternative for piezoelectric actuator with self‐powered capability and operational safety. Meanwhile, the hysteresis of the stack actuator that is critical in precise positioning control is reduced by 58.1%. A precise positioning system is demonstrated by utilizing the TENG‐powered stack actuator as an object stage for microscope focusing applications. The feasibility of vibration control with a 76.7% reduction in vibration amplitude is also verified via two TENG‐powered MFC actuators. A rectifying control circuit comprising the rectifier and gas discharging tube is established to implement AC–DC conversion and discharging control, achieving a larger displacement of the unimorph actuator. The TENG‐powered piezoelectric micropump demonstrates its potential application in liquid transport through straightforward operation. [ABSTRACT FROM AUTHOR]

[Display omitted] • A bionic unidirectional liquid transport platform over long distance was proposed. • Crescent-shaped groove was designed to overcome the liquid resistance at the joints. • The platforms with customized liquid transport trajectories were flexibly designed. • Liquid transport, such as anti-gravity transport and liquid splitting, were realized. Spontaneous liquid transport is increasingly being applied in various fields such as microfluidics, fuel cells, phase change heat transfer, water harvesting, etc. However, long-distance spontaneous liquid transport with path-customizable motion trajectories is still challenging. Drawing multi-inspirations from the wedge-shaped structures of iris petals, the continuous structures of bamboo joints, and the microgroove structures of Nepenthes mouth edge, we fabricate a modular, pump-free biomimetic liquid transport platform by 3D printing and surface modification. The platform is composed of sequential wedge notches, and a crescent-shaped groove is designed at the joint of every two connected wedge structures. The platform is characterized by path-customizable liquid transport trajectories and can be used to achieve long-distance liquid transport without the need of external energy fields, and the multi-level nested structures along the depth significantly facilitates the liquid transport. Experimental study and theoretical force analysis show that the crescent-shaped grooves enable the liquid to overcome joint barriers by converting potential energy accumulated at joints into kinetic energy, achieving a maximum velocity of 18 mm/s. Taking advantage of the flexibility of 3D printing and long-distance transport capability, the modular structure of the platform enables customization of the transport distance and trajectory. By assembling 14 bamboo-like wedge-shaped units in series, we realized a transport distance up to 350 mm, which could be further increased by connecting more units. Furthermore, we develop various modular and multifunctional liquid transport platforms for anti-gravity transport, liquid diversion, and customized transport trajectories, which demonstrate that our design strategy could be an available solution for path-customizable liquids transport in fields like bio-sensing, fuel cells, etc. [ABSTRACT FROM AUTHOR]

Smart membranes with stimuli-modulated liquid-selective permeation hold promise for on-demand separation of oil/water mixtures, yet the facile preparation of membranes with sensitive and easily implemented responsiveness still remains a challenge. Herein, we present the sensitive manipulation of water-selective permeation using a weak electric field with ultra-low voltages and the resulting on-demand separation of oil-in-water emulsions on a facilely prepared laminar membrane. Fabricated via simple vacuum filtration, the MXene membrane possesses high conductivity and molecule-scaled transport channels, both of which facilitate the sensitive modulation. A voltage of just several negative volts (−4 V) can significantly switch the wetting and permeation of water on the membrane, which is distinctly lower than that previously reported (hundreds of volts and even several kV). In addition, the negatively charged membrane, under the applied bias, enhances the rejection of surfactant-wrapped oil droplets, preventing the fouling of material surfaces. Consequently, the separation of oil-in-water emulsions was achieved with high oil rejection rate (99 %) and considerable flux for a variety of oil types and percentages. Particularly for the crude oil/water mixtures, the rejection rate reached 99 % and the flux achieved 69.72 L m−2 h−1. This study presents a novel example for achieving easy and economical smart separation of oil/water mixtures using highly conductive materials, and should also spark research in areas such as water purification, drug delivery, microfluidic valves, etc. [Display omitted] • On-demand separation of oil/water emulsions was achieved by ultra-low voltage. • The separation membrane was facilely prepared using highly conductive two-dimensional MXene. • The weak electric field triggers and promotes water permeation while blocks oil passage. • Molecule-scaled transport channels and high conductivity contribute to the efficient separation. • Electrostatic repulsion between oil droplets and membrane improves oil anti-fouling. [ABSTRACT FROM AUTHOR]

Engineered surfaces play a vital role in various fluid applications, serving specific functions such as self-cleaning, anti-icing, thermal management, and water energy harvesting. In nature, biological surfaces, particularly those displaying physiochemical heterogeneity, showcase remarkable fluid behaviors and functionalities, offering valuable insights for artificial designs. In this Review, we focus on exploring the fascinating fluid phenomena observed on natural biological surfaces and the manipulation of fluids on bioengineered surfaces, with a particular emphasis on droplets, liquid flows, and vapor flows. We delve into the fundamental principles governing symmetric fluid motion on homogeneous surfaces and directed fluid motion on heterogeneous surfaces. We discuss surface design strategies tailored to different fluid scenarios, outlining the strengths and limitations of engineered surfaces for specific applications. Additionally, the challenges faced by engineered surfaces in real-world fluid applications are put forward. By highlighting promising research directions, we hope to stimulate advancements in bioinspired engineering and fluid science, paving the way for future developments.

The current research on wearable electrochemical sensors for urine monitoring is relatively rare, which is primarily limited by the lack of an active management mechanism to effectively manipulate the transportation of excessive liquids. In this work, a Janus fabric with hexagonal microcavity channels (HMJ-FT) was assembled based on a disposable facial towel, which was further introduced to develop the wearable electrochemical sensor (HMJ-Sensor) for the directional manipulation of urine transportation and simultaneous detection of dopamine (DA) and uric acid (UA). The designed hexagonal microcavity structure can synergistically promote horizontal migration and vertical transport of liquid, thus ensuring efficient and rapid manipulation of urine transportation and preventing its accumulation and reflux, which are essential for accurate, real-time monitoring. Therefore, the constructed HMJ-Sensor demonstrated a lower limit of detection (LOD) compared to most reported wearable sensors, which is 10.0770 nM for DA and 1.4100 nM for UA, respectively. Additionally, it also has the widest detection range known to date (DA: 0.0360-4000 μM; UA: 0.0050-6000 μM), which can better adapt to the large volume of urine transport and significant fluctuations on urine concentration in practical applications. After being subjected to a 120-day storage period along with multiple bending, rubbing, and washing treatments, the HMJ-Sensor maintained its excellent detection performance, indicating its high stability and reliability. This work not only provided a novel strategy for the manipulation of urine transport but also enhanced the detection capabilities of urine monitoring, which holds significant potential for boosting wearable applications and medical monitoring in physiological and clinical settings.

Abstract Warp knitted mesh fabric was usually applied to sportswear due to good air transmission, but without multilayer structure and one-way transport property. In order to solve this problem, the miss-lapping structure was applied to examine the possibility to fabricate multilayer and improve water transport in warp knitting structure. Besides, the effect of thread type and warp density on comfort properties were also exploited to enhance the moisture management. The moisture management test, water vapor permeability and air permeability were examined. Long float at the back side in structure I formed by miss-lapping could improve liquid transport and air permeability, but slightly reduce water vapor permeability. With proper density, there existed the optimal one-way transport capacity and overall moisture management. Warp density in 20 cpc was an optimal parameter of knitting process. Taking advantage of miss-lapping, sample 5 where polypropylene was partly threaded on GB1 provided best moisture management, water vapor permeability and air permeability.

• Novel method integrates 3D printing and ITO glass for phase change visualization. • Matching pore size to bubble nucleation enables boiling to thin film transition. • Enhanced heat transfer via continuous vapor escape channels. • Strong capillary forces stabilize vapor escape and liquid transport. • Ideal evaporators possess strong liquid locking and optimized pore structures. Porous evaporators have become the core component of energy systems such as thermal management of electronic equipment, solar steam power generation, and wet power generation by the advantages of their large specific surface area, high-efficiency heat transfer, and liquid self-transportation. How direct observation of the heat and mass transfer process inside the porous evaporator has always puzzled researchers, resulting in a lack of a theoretical foundation for the optimization of the porous structure. This limitation has significantly hindered improvements in the performance of energy systems. To address this challenge, this study proposes a novel visualization approach that integrates three-dimensional (3D) printing and Indium-Tin Oxide (ITO) glass observation of the phase change region in the evaporator. The key novel findings are that: (1) By controlling the pore size to match the bubble nucleation size, the phase change mode can transition from boiling to thin film evaporation, forming a continuous easy vapor escape channel and enhancing heat transfer. (2) The larger the capillary force of the porous structure, the stronger the locking force at the vapor–liquid interface, which ensured the stability of vapor escape and liquid transport at higher heat flux. (3) An ideal porous evaporator should possess strong liquid locking ability, feature pore structures at the phase change point within the size range of vapor nucleation, and simultaneously exhibit large pore size conducive to vapor escape. This investigation casts a new light on the fluid transport and phase change characteristics of porous evaporators, laying a theoretical foundation for the design of porous evaporators. [ABSTRACT FROM AUTHOR]

In rotary tube reactors, rotary evaporators, or rotary atomizers, liquid is transported through a partially filled axially rotating pipe. The flow is annular when the pipe rotation is fast enough, as in most engineering applications; in this research, we investigated the steady and transient behavior of annular flows in a partially filled axially rotating pipe. First, the governing equations of a laminar annular flow were derived, solved, and verified. Then, the theory was used to study the transient flow behavior. The responses of the outlet flowrate to inlet flowrate variations and pressure fluctuations were investigated. To clarify the system parameters in which the theory holds, we also conducted experiments to find flow mode boundaries between the non-annular flow and the annular flow. Steady state solutions of the theory were then used to find system parameters in which the flow is laminar. The effects that a screw inserted inside the pipe has, on both the flow mode boundaries and the transient flow characteristics, are also demonstrated. To the best of our knowledge, this is the first inspection of the transient characteristics of an annular flow and the effects of an inserted screw on this type of flow. • We proposed a relationship between system parameters and flow mode boundaries. • The outlet to inlet flowrate relation is a first-order system with time delay. • Pressure disturbances at resonance frequencies badly fluctuate the outlet flowrate. • A screw structure inserted in the rotating pipe promotes the onset of annular flow. • The screw structure also modifies the annular flow's transient behaviors. [ABSTRACT FROM AUTHOR]

Liquid transport is of great significance to industry and life, such as microfluidic chip, liquid separation, fluidic gates, and tissue fluid discharge. However, there are still some challenges to achieve well‐controlled directional transports, and the delamination often occurs for the now existing Janus membranes. Herein, fibrous assembly with hierarchically fibrous helix architecture bioinspired by tendrils through electrospinning combined with mechanical twisting technology is engineered and demonstrated. The liquid transport behavior using as fluidic gates by connecting light‐emitting diode (LED) and the resulting liquid separation mechanism were characterized and investigated, respectively. Different from previous materials, due to the existence of distinct periodic alternate gradient interface topology, the hierarchically fibrous helix exhibits a long‐range order and directional liquid transport trajectory as well as improved water management property. This strategy is cost‐effective and can be extended to other fields. The resultant materials are highly promising for applications in actuators, microfluidic chips, and fluidic gates. [ABSTRACT FROM AUTHOR]

Warp knitted mesh fabric was usually applied to sportswear due to good air transmission, but without multilayer structure and one-way transport property. In order to solve this problem, the miss-lapping structure was applied to examine the possibility to fabricate multilayer and improve water transport in warp knitting structure. Besides, the effect of thread type and warp density on comfort properties were also exploited to enhance the moisture management. The moisture management test, water vapor permeability and air permeability were examined. Long float at the back side in structure I formed by miss-lapping could improve liquid transport and air permeability, but slightly reduce water vapor permeability. With proper density, there existed the optimal one-way transport capacity and overall moisture management. Warp density in 20 cpc was an optimal parameter of knitting process. Taking advantage of miss-lapping, sample 5 where polypropylene was partly threaded on GB1 provided best moisture management, water vapor permeability and air permeability. [ABSTRACT FROM AUTHOR]

Directional liquid transport (DLT) on fibrous systems has been widely used in both natural organisms and practical applications as an important mass transfer strategy. So far, DLTs on fibers are heavily dependent on the conical structure that enables generating the Laplace pressure difference. For the cylindrical fibers, liquid can only transport evenly along both directions of the axis driven by the capillary forces between fibers, which however hardly proceeds directionally in a controllable way. Here, the authors revealed that the dual cylindrical hairs bear the ability of DLT, which is attributable to the wet‐rebuilt open‐wedged scales. Capillary forces along wedge corners facilitate the liquid transport in the against‐scale direction, while the pinning effect at the sharp edges of open‐wedges works cooperatively with the anisotropic retention force imparted by the ratchet structures to inhibit liquid spreading in the with‐scale direction. Consequently, liquid prefers to transport in the against‐scale direction on dual cylindrical hairs. Drawing inspirations, the authors develop the conceptual‐model of dual cylindrical fibers that is capable of DLT, and moreover the DLT with different rectification ratios can be well‐controlled depending on the opening angle of wedges. The result offers new insights for manipulating liquid using cylindrical fibrous systems. [ABSTRACT FROM AUTHOR]

Padding is an essential component in a multilayer compression bandaging system, used inside the compression bandage through which substantial amount of pressure is exerted on the limb of patient for treatment of venous leg ulcers. As a result, the liquid transmission behavior of padding is also critical in managing body fluids or sweat exuded from the affected limb, reducing the excessive moisture build-up around the wound and thereby ensuring comfort to and hence a better compliance from the patients. This study investigates the in-plane fluid transport characteristics of needle-punched nonwoven padding bandages. It first reviewed the existing studies related to the problems, and discussed their limits and possible improvements in dealing with complex fluid transport issues in textile porous media. The measurement of fluid transport under different pressure levels was then done using a newly designed apparatus capable of simultaneously tracing the liquid in-plane spreading along different directions, and obtaining several transport characteristics of a testing sample, e.g. the liquid flow anisotropy, the rate of movement, the area of wet surface with time, etc. Also the effects of several important factors, such as the levels of pressure applied, the specimen bulk density, and needling density of the padding products, have been experimentally investigated. In addition, based on an extended Lucas-Washburn theory, we calculated the liquid flow distance, both instantaneous speed and a more useful time-averaged speed v(av) at any given direction, and also defined a flow anisotropy index I(A) as a convenient parameter to represent the material flow anisotropy. The applications of v(av) and I(A) to actual samples have demonstrated the usefulness of these parameters in characterizing the flow nature and behavior of the materials.

Accurate metering and transport of samples and reagents are a critical process in many microfluidic applications, such as biochemical analysis, diagnostics and drug delivery. However, as the liquid volume to be processed is usually rather small, its sensoring and metering remains a challenging problem. Though some studies on this issue have been reported so far, there is still much room for improvement regarding the metering accuracy, system simplicity and control flexibility. In this work, we propose a simple, automatic and cost-effective method for microfluidic metering and transport. To improve the accuracy, the geometric metering approach with hydrophobic valves of minimum dead volumes is adopted. Besides, an on-chip Bernoulli pump is designed to reduce the hardware requirement, and a pulse width modulation (PWM) scheme is used to facilitate the operation. Testing results show that for metering of 20 μL liquid, the averaged error is − 1.3%, the relative standard deviation is 0.42%. The liquid transport can also be well regulated via PWM method. [ABSTRACT FROM AUTHOR]

In nature, the feathers of the goose Anser cygnoides domesticus stay superhydrophobic over a long term, thought as the main reason for keeping the surface clean. However, contaminants, especially those that are oleophilic or trapped within textures, cannot be removed off the superhydrophobic feathers spontaneously. Here, a different self‐cleaning strategy based on superhydrophilic feathers is revealed that is imparted by self‐coating of the amphiphilic saliva, which enables removing away low‐surface‐tension and/or small‐size contaminants by forming directional water sheeting depending on their unique anisotropic microstructures. Particularly, the surface superhydrophilicity is switchable to superhydrophobicity upon exposure to air for maintaining a clean surface for a long time, which is further enhanced by coating with self‐secreted preening oil. By alternate switching between a transient superhydrophilicity and a long‐term stable superhydrophobicity, the goose feathers exhibit an integrated smart self‐cleaning strategy, which is also shared by other aquatic birds. An attractive point is the re‐entrant structure of the feathers, which facilitates not only liquid spreading on superhydrophilic feathers, but also long‐term stability of the cleaned surface by shedding water droplets off the superhydrophobicity feathers. Thus, artificial self‐cleaning microtextures are developed. The result renews the common knowledge on the self‐cleaning of aquatic bird feathers, offering inspiration for developing bioinspired self‐cleaning microtextures and coatings. [ABSTRACT FROM AUTHOR]

Wider use of timber has the potential to greatly reduce the embodied carbon of construction. Improved chemical treatment could help overcome some of the barriers to wider application of timber, by furthering the durability and/or mechanical properties of this natural material. Improving timber treatment by treating the whole volume of a piece of timber, or tailored sections thereof, requires sound understanding and validated modelling of the natural paths for fluid flow through wood. In this study we carry out a robust analysis of three-dimensional X-ray CT measurements on kiln-dried softwood in the presence of flow and identify small portions of early-wood which are uniquely capable of transporting fluids—herein 'efficient transport pathways'. We successfully model the effects of these pathways on the liquid uptake by timber by introducing a spatial variability in the amount of aspiration of the bordered pits following kiln drying. The model demonstrates that fluid advances along these efficient transport paths between 10 and 30 times faster than in the remainder of the timber. Identifying these efficient transport pathways offers scope to improve and extend the degree to which timber properties are enhanced at an industrial scale through processes to impregnate timber. [ABSTRACT FROM AUTHOR]

• Terahertz pulsed imaging was used to investigate the liquid transport kinetics of α -alumina powder compacts. • A range of compaction forces and sintering conditions were used for the terahertz measurements. • The microstructure characteristics as well as the surface properties of the alumina compacts have an impact on the water ingress rate. • The mass transport mechanism of the water ingress into the alumina compacts is consistent with Darcy flow. • The hydraulic radius of the alumina compacts was determined. Investigating the liquid transport kinetics of solid catalysts is of great importance for gaining a better understanding of the manufacturing and performance of such catalysts during reaction upon contact with the liquid. Terahertz pulsed imaging (TPI) coupled with a newly designed flow cell was used to quantify the rate of water ingress into α -alumina pellets with a range of different porosities. A wide range of compaction forces (cold compaction, 7–58 kN) and sintering conditions (no firing and sintering at 1200 and 1300 °C) was investigated to explore the optimal pellet microstructure, i.e. mechanically strong but sufficiently porous for fast liquid transport kinetics. The results confirm that both the microstructure characteristics, particularly porosity, as well as the surface properties, i.e. wettability, influence the liquid transport kinetics. Fitting the TPI penetration rates with a power law shows that the type of observed mass transport characteristics is consistent with Darcy flow. The Lucas–Washburn equation was used to calculate the hydraulic radius based on the transport data. In summary, the results demonstrate that TPI has great potential to study the liquid transport kinetics of porous ceramic catalysts and catalyst supports and that can comfortably quantify transport processes at rates of 250 μm s−1 and beyond in such substrates for better quality control and optimised design and performance of such materials. [ABSTRACT FROM AUTHOR]

Natural systems contain surfaces with unique wettability that enable functionalities such as directional liquid transport. Such systems typically rely on nano/microscale structural anisotropy and/or chemical structures, which induce a directional friction at solid–liquid interfaces. Here, the origin of the solid–liquid interfacial tribo‐dynamics of the skin of Lampropeltis pyromelana (Arizona Mountain Kingsnake) is examined. Continuous and directional water transport phenomenon is found on its hydrophobic slippery ventral skin. Liquid is continuously supplied and spread on its skin in a rear to front direction although the surface is slippery. X‐ray tomography and spectroscopy reveal that the skin surface is composed of an asymmetric wrinkle structure and a homogeneous hydrophobic lipid layer. Owing to this surface feature, the rear directional water spreading is restricted by slant reentrant pinning, whereas the front directional water spreading is promoted by liquid bridging, which continued as long as water is supplied. Because this system type relies on a superhydrophilic sticky surface, it is expected that related biological design principles can be used to develop artificial mass fluid transport systems without undesirable adhesion losses. [ABSTRACT FROM AUTHOR]

Sanitary napkin is worn in direct skin contact and is an essential product for most women. Its liquid transport properties, depending on the material and design, affect skin wetness, skin irritating potential and comfortable feeling. Disposable sanitary napkin is commonly used whilst reusable sanitary napkin is also available in the market for sustainable reason. In this study, a measurement method originated from Forced Flow Water Transport Tester (FFWTT) was introduced which can characterize the direction of liquid transport of sanitary napkin under different pressure loadings. Disposable sanitary napkins with nonwoven or perforated film surface were compared against the reusable sanitary napkins. The results found that the reusable sanitary napkins tend to accumulate more next-to-skin moisture than the disposable sanitary napkin at equivalent loadings. Also, its transplanar wicking is poor. Besides, disposable sanitary napkins incorporated with superabsorbent polymer provide acceptable liquid transport property whilst those made of flex foam give the best performance. [ABSTRACT FROM AUTHOR]

In the last years, the huge success of shale gas and oil exploitation in North America and enhanced oil recovery by injecting carbon dioxide have attracted more attentions in petroleum industry. The reasonable scheme for shale oil production is a key step for sustainable and high-efficiency products of shale resources, which is dependent on the basic law of liquid flow. In this paper, a multiscale model is established based on homogenization theory to investigate the law of liquid flow within shale system. Considering the results of molecular dynamics simulation, the Navier-Stokes equation coupled with slip boundary is used to describe the liquid flow within microscale domain and the slip-corrected Darcy-like transport model in which clear physical meaning can be shown for every parameter can be derived for macroscale domain. In order to validate derived model, three cases including water and oil flow within simple nanopores are implemented and the results show that homogenization models match well with the results of molecular dynamics simulation for water flow with different contact angle and oil flow within inorganic pore. However, high-order slip-corrected model will deviate from the molecular dynamics simulation for oil flow within simple organic pore when pore size is smaller than 5.24 nm. Then the fractal porous medias are reconstructed based on Monte Carlo simulation and the several critical parameters are discussed. Finally, the results of homogenization model are applied in reservoir scale model to investigate shale oil production performance for economic evaluation and production optimization. Image 1 • Homogenization model for liquid flow is established while coupled with Navier-Stokes equation and slip boundary which is compared with the results of the molecular simulation for simple pore structure. • The fractal porous medias are reconstructed based on Monte Carlo simulation. • The results of homogenization model are applied to predict shale oil production for economic evaluation and production optimization. [ABSTRACT FROM AUTHOR]

Liquid transport in porous materials is affected significantly by the geometry of the non-uniform capillaries. In this study, an N -section lotus-rhizome-node-like non-uniform capillary model was for the first time proposed based on the plane Poiseuille flow and capillary pressure equation to investigate the liquid transport in porous fibrous media. Normalized total flow time of the non-uniform capillary was obtained as a function of the height and width ratio between the converging and diverging nodes and their total number. The results indicated that the velocity of liquid transport greatly depended on the number of nodes in a certain liquid transport length. The non-uniform capillaries with frequent alterations between converging and diverging nodes have low liquid transport efficiency. The thick capillary exhibits fast liquid transport efficiency in those capillaries with the same self-similar geometry. The model was verified using polypropylene filament yarns and different liquids. The results agreed well with the theoretical prediction. This work not only provides a deeper understanding of liquid transport inside porous fibrous media with non-uniform capillaries, but can also guide the novel design and optimization of functional fibrous materials. [ABSTRACT FROM AUTHOR]

The ceramic materials' properties and the penetrating liquid both influence liquid transport into ceramic catalytic materials. Terahertz pulsed imaging (TPI) in combination with a flow cell was used to investigate the transport process of polar and less polar solvents into a range of α -alumina powder compacts. The TPI results show that the alumina samples with the largest heating rate (200 °C h−1) have the fastest water transport. The TPI results also reveal that 1-octanol takes much longer to transport through the alumina samples than water, as the viscosity of 1-octanol is much larger than that of water. Since 1-octanol is semi-transparent to terahertz radiation, it was possible to study the liquid transport process and the structural changes behind the liquid front, such as the change in the refractive index of the compact and the fill fraction of 1-octanol in the compact as a function of time. • The transport of solvents with different polarities into a range of α -alumina powder compacts was investigated using terahertz pulsed imaging. • The alumina samples with the largest heating rate of sintering (200 °C h−1) have the fastest water transport. • The properties of the solvent, e.g. viscosity, have an impact on its transport through the alumina samples. • Structural changes behind the liquid front were studied as 1-octanol is semi-transparent at terahertz frequencies. [ABSTRACT FROM AUTHOR]

Liquid transport (wicking) has great effect on the physiological comfort, since it directly determines the moisture management of fibrous assemblies. For elastic fabric structures, the wickability primarily depends on several factors, such as tensile strain and ambient conditions (e.g., temperature, relative humidity). The main purpose of this work was to systematically clarify the effects of water temperature and relative humidity on vertical liquid water transport of as-prepared cotton/lycra elastic woven fabric experimentally and theoretically. On the experimental side, the results indicated that our as-prepared fabric exhibited a water temperature-strengthening effect, while a humidity-weakening effect was produced simultaneously. In other words, a higher water temperature results in a higher equilibrium wicking height, whereas a higher relative humidity results in a decreased wicking height. Furthermore, the underlying wicking mechanism in each case was graphically unraveled. On the analytical side, the proposed Laughlin-Davies model turns out to be appropriate, it can replicate the wicking characteristics of fabric in both of these cases qualitatively and quantitatively. These findings are expected to provide a deep understanding of fabric wicking under a realistic regime.

Guided bone regeneration gathers significant interest in the realm of bone tissue engineering; however, the interplay between membrane thickness and permeability continues to pose a challenge that can be addressed by the water-collecting mechanism of spider silk, where water droplets efficiently move from smooth filaments to rough conical nodules. Inspired by the natural design of spider silk, an innovative silk fibroin membrane is developed featuring directional fluid transportation via harmoniously integrating a smooth, dense layer with a rough, loose layer; conical microchannels are engineered in the smooth and compact layer. Consequently, double-layered membranes with cone-shaped microporous passageways (CSMP-DSF membrane) are designed for in situ bone repair. Through extensive in vitro testing, it is noted that the CSMP-DSF membrane guides liquid flow from the compact layer's surface to the loose layer, enabling rapid diffusion. Remarkably, the CSMP-DSF membrane demonstrates superior mechanical properties and resistance to bacterial adhesion. When applied in vivo, the CSMP-DSF membrane achieves results on par with the commercial Bio-Gide collagen membranes. This innovative integration of a cross-thickness wetting gradient structure offers a novel solution, harmonizing the often-conflicting requirements of material transport, mechanical strength, and barrier effectiveness, while also addressing issues related to tissue engineering scaffold perfusion., (© 2023 Wiley‐VCH GmbH.)

Highlights • Bio-inspired "fluidic diode" for unidirectional water transport (transport velocity ≈ 1 mm/s). • Unidirectional water transport even against gravity. • Large-area, passive, based on disposable polymer, i.e. laser-engraved in poly(methyl methacrylate) (PMMA). • Possible applications: biomedical microfluidics, lab-on-a-chip, micro-analysis devices, lubrication, cooling etc. Abstract In this paper, we describe the design, fabrication and functional principle of microfluidic diodes – devices for directional liquid transport. They are passive (i.e., need no external energy input) and are capable of unidirectional water transport even vertically against gravity, i.e. they prevent backflow of liquid. In designing the devices with an area of several cm2, we used a capillary channel network that was bio-inspired by the skin of the Texas horned lizard (Phrynosoma cornutum). By means of a CO 2 laser, we engraved the microfluidic structures into plates made of poly(methyl methacrylate) (PMMA), a low-cost technical polymer commonly used in disposable microfluidics. We then characterized the topography of the fabricated 3D structures by optical coherence tomography (OCT). Theoretical analysis of the OCT data enabled us to determine their working principle which differs from that presented previously in the literature. We accessed the fluid transport properties of the device by measuring distance, velocity, wetted area and flow asymmetry. Biomimetic abstraction led to a simplified structure which was validated experimentally. All tested devices allowed unidirectional liquid transport at velocities in the range of a few mm/s in the forward direction while preventing backflow of volumes of about 0.5 ml in the backward direction on an area of approximately 28 mm x 14 mm. The transport velocity of about 1 mm/s was found to be nearly constant for a distance of approximately 2 cm, beyond which it decreased. The application spectrum ranges from biomedical microfluidics, lab-on-a-chip and micro-analysis devices to filtration, lubrication, cooling of electronics and e-ink displays. [ABSTRACT FROM AUTHOR]

The magnetic actuation of deposited drops has mainly relied on volume forces exerted on the liquid to be transported, which is poorly efficient with conventional diamagnetic liquids such as water and oil, unless magnetosensitive particles are added. Herein, we describe a new and additive-free way to magnetically control the motion of discrete liquid entities. Our strategy consists of using a paramagnetic liquid as a deformable substrate to direct, using a magnet, the motion of various floating liquid entities, ranging from naked drops to liquid marbles. A broad variety of liquids, including diamagnetic (water, oil) and nonmagnetic ones, can be efficiently transported using the moderate magnetic field (ca. 50 mT) produced by a small permanent magnet. Complex trajectories can be achieved in a reliable manner and multiplexing potential is demonstrated through on-demand drop fusion. Our paramagnetofluidic method advantageously works without any complex equipment or electric power, in phase with the necessary development of robust and low-cost analytical and diagnostic fluidic devices. [ABSTRACT FROM AUTHOR]

The kinetics of unidirectional penetration of NaOH aqueous solution into rectangular samples of wood oriented parallel to a stern axis were studied. Scots pine (Pinus sylvestris), European larch (Larix decidua), blackthorn (Prunus spinosa), white willow (Salix alba), and horse-chestnut wood (Aesculus hippocastanum) were studied in this work. The time dependence of liquid incorporation was measured by the volumetric method as a change of total volume of coexisting liquid (NaOH/H2O) phase. The total thickness of the swollen surface layer d and mean value of the apparent diffusion coefficient of aqueous NaOH solution at 22 °C were determined.

The “cocido”: alkaline treatment to eliminate bitterness is the main step involved in the process of elaboration of pickled green olives. Over time, this treatment has undergone a series of modifications in order to reduce the volume of its waste water and to avoid the storage of the fruits, prior to the lye treatment, in the Manzanilla variety. In this paper, a series of previous treatments related to the lye treatment and the principal modifications applied by the industry are optimized. As a previous treatment, related to the mechanical harvesting of the olives, the transport of the fruits freshly harvested in liquid (alkaline solutions of very low concentration) was studied. Also, the addition of calcium and / or sodium salts and a cooling of the lye was studied, with the additional aim of eliminating the storage step in the Manzanilla variety. On the basis of these results, it can be said that a previous storage of fruits of the Manzanilla variety in NaOH solution of low concentration is useful for the mechanical harvesting of olives without a loss in product quality. On the other hand, the addition of calcium and / or sodium salts in the lye solution and the cooling of it improved olive texture and avoided the blistering defect.

Liquid transportation is fundamentally important in microfluidics, water collection, biosensing, and printing, and has attracted enormous research interest in the past decades. However, despite substantial progress, it remains a big challenge to achieve the controlled transport of viscous liquids (>100 mPa s) commonly existing in daily life and the chemical industry. Inspired by the gastrointestinal peristalsis of mammalians that can efficiently transport viscous chyme (viscosity up to 2000 mPa s) by the synergistic combination of contraction driving force and lubrication, here, the design and construction of double-layered tubular hydrogel actuators for directional transport of highly viscous liquids ranging from ≈1000 mPa s to >80 000 mPa s under the control of an applied 808 nm laser, which is attributed to the cooperation of outer layer contraction and water film lubrication of the inner layer, is reported. It is demonstrated that the actuators are capable of transporting polymerizing liquid whose viscosity significantly increases to ≈11 182 mPa s in 2 h. This work paves a new avenue toward directional transport of highly viscous liquids, which not only expands the research scope of liquid transportation, but will spur the design of new liquid actuators with potential applications in viscous-liquid-based microfluidics, artificial blood vessels, and soft robots., (© 2023 Wiley-VCH GmbH.)

In this paper, we study the liquid transport between particles of different sizes, as well as build a dynamic liquid bridge model to predict liquid transport between these two particles. Specifically, the drainage process of liquid adhering to two unequally-sized, non-porous wet particles is simulated using direct numerical simulations (DNS). Same as in our previous work (Wu et al., AIChE Journal, 2016, 62:1877–1897), we first provide an analytical solution of a proposed dynamic liquid bridge model. We find that such an analytical solution also describes liquid transport during collisions of unequally-sized particles very well. Finally, we show that our proposed model structure is sufficient to collapse all our direct numerical simulation data. Our model is hence able to predict liquid transport rates in size-polydisperse systems for a wide range of parameters. [ABSTRACT FROM AUTHOR]

We study dynamic liquid bridge formation, which is relevant for wet granular flows involving highly viscous liquids and short collisions. Specifically, the drainage process of liquid adhering to two identical, non-porous wet particles with different initial film heights is simulated using Direct Numerical Simulations (DNS). We extract the position of the interface, and define the liquid bridge and its volume by detecting a characteristic neck position. This allows us building a dynamic model for predicting bridge volume, and the liquid remaining on the particle surface. Our model is based on two dimensionless mobility parameters, as well as a dimensionless time scale to describe the filling process. In the present work model parameters were calibrated with DNS data. We find that the proposed model structure is sufficient to collapse all our simulation data, indicating that our model is general enough to describe liquid bridge formation between equally sized particles. © 2016 American Institute of Chemical Engineers AIChE J, 62: 1877-1897, 2016 [ABSTRACT FROM AUTHOR]

Transport is central for frost deterioration, though playing different roles before/after starting freeze/thaw. Liquid uptake (LU) during rapid freeze/thaw in water (RF) and frost/salt test (FS) and relations LU-scaling and -internal damage were investigated on non- and air-entrained (AE) concrete (w/b = 0.29–0.45, 50–130 MPa). 8–22 % of the air-voids became waterfilled during water-curing. Absorption during pre-saturation in FS correlated to initial scaling but without general LU - salt scaling correlation. LU (kg/m2) was lower in RF than in FS, indicating different transport/damage mechanisms. In RF, LU correlated to cracking and scaling (especially well-cured concrete). Air entrainment always reduced LU. FS to −52 °C increased both LU and scaling for internally damaged concretes compared to −20 °C but did not affect LU in undamaged well-cured concretes. Modelled and measured LU during RF correlated very well and indicates hydraulic pressure is more important than cryosuction for reducing LU in AE concrete. [ABSTRACT FROM AUTHOR]

We present in this study results from X-ray tomographic microscopy with synchrotron radiation performed both in attenuation and phase contrast modes on a limestone sample during two stages of water drying. No contrast agent was used in order to increase the X-ray attenuation by water. We show that only by using the phase contrast mode it is possible to achieve enough water content change resolution to investigate the drying process at the pore-scale. We performed 3D image analysis of the time-differential phase contrast tomogram. We show by the results of such analysis that it is possible to obtain a reliable characterization of the spatial redistribution of water in the resolved pore system in agreement with what expected from the theory of drying in porous media and from measurements performed with other approaches. We thus show the potential of X-ray phase contrast imaging for pore-scale investigations of reactive water transport processes which cannot be imaged by adding a contrast agent for exploiting the standard attenuation contrast imaging mode. [ABSTRACT FROM AUTHOR]

Biomimetics of the branching structure in textiles which can improve the water transport was proved by previous research on weft knitted fabrics. The present work focuses on the evaluation of a branching network in light-weight knitted fabrics for polo shirt which were made of 100 % cotton and 100 % polyester yarn. The sweating manikin test and wearer trial were applied to make objective and subjective evaluation on plant structured polo shirt against commercial polo shirt. The plant structured polo-shirt can provide lower insulation resistance, evaporation resistance tested by sweating manikin. As well, lower temperature and humidity values were observed in plant structured polo-shirt assessed by wearer trial test under both simulating outdoor/indoor environment and normal activity workload. All improved fabric and garment properties related to comfort are beneficial to clothing comfort. It is verified that the plant structured fabric for polo shirt can enhance the overall comfort and wearing experience. [ABSTRACT FROM AUTHOR]

Biomimetics of the branching structure in textiles which can improve the water transport was proved by previous research on weft knitted fabrics. The present work focuses on the development of a branching network in light-weight knitted fabrics for polo shirt. Vertical wicking test, water drop test, water vapor permeability as well as air resistance were employed in this study to measure the water transport behavior of fabrics. Besides, Kawabata evaluation system was applied to demonstrate the handle of produced fabric and control. Fabric appearance, skewness change and dimensional change after home laundering were applied to demonstrate the difference between plant structured fabric and control fabric. In conclusion, 100 % cotton and 100 % polyester fabrics developed with such a branching structure exhibited faster water absorption, water transport, improved handle and better normal wearing and washing application property compared with single pique fabric due to wide application for polo shirt. [ABSTRACT FROM AUTHOR]

Atmospheric-pressure discharge plasma is a promising tool for many applications due to its enhanced plasma chemistry. In this paper, a low-temperature atmospheric-pressure nitrogen plasma jet generated by bare metal electrode’s discharge is reported. The typical electrical and optical characteristics of the atmospheric-pressure plasma jet (APPJ) are studied. Optical emission spectrum shows that excited OH, NO, N2(C-B), N2+ (B-X), N2(B-A), and O emissions are produced by the plasma jet. When the applied voltage is 2.5 kV, the vibrational and rotational temperatures of the APPJ are, respectively, 2275 and 325 ± 5 K. Hydrophilic treatment of the superhydrophobic aluminum surface is also presented, and the results show that the wettability of the APPJ-treated areas is obviously improved, which was mainly due to the slight morphological changes and the incorporation of oxygen-containing functional groups. A pumpless antigravity water transport on APPJ-induced wettability contrast patterning surface is also presented to show the potential applications of the APPJ hydrophilic treatment of metals. These results demonstrate the application prospects of bare electrode’s discharge plasma jet, especially in metal-based smart surface fabrications. [ABSTRACT FROM PUBLISHER]