Janus Membrane Research Articles

A novel strategy for retarding membrane wetting under electrical field: Embedding silver nanowires into UiO-66-NH2/graphene oxide composite thin membrane

Membrane distillation (MD) is a promising desalination technology that combines traditional distillation processes with membrane separation technology, but when the feed solution contains amphiphilic substances such as surfactant, the hydrophobic membrane is prone to being wetting, which hinders its widespread application. In this study, a novel Janus membrane was developed by embedding Zr-MOF and silver nanowires into the modified graphene oxide composite membrane to improve its separation performance, and the effect of high-concentration SDS on the membrane performance was studied. The experimental results showed that the conductive membrane exhibited excellent performance when powered on for 5 min every 2.5 h under 2 V voltage. The flux stabilized at 19.6 L/(m2h) with a desalination rate up to 99.9 % and no obvious signs of membrane wetting. It was found that the effect of electric field caused a negative charge on the membrane surface, forming a charge repulsion force with the SDS. Simultaneously, intermittent electrical flotation can effectively remove SDS that has accumulated on the membrane surface, thus achieving efficient and stable operation of MD system. Moreover, a machine learning approach with Catboost was applied to predict and unveil the complex effects on membrane performance, providing a deep insight to treat wastewater containing surfactant.

Fabrication of robust, durable and integrated Janus coating for corrosion and fouling protection in marine environment

Janus membranes with different valuable characteristics and integrated structures have attracted a great interest of researches in order to achieve important breakthroughs in the related fields. However, the application of Janus membranes for development of anticorrosion coatings on metallic structures has been limited, which is due to weak interfacial bonding within the Janus structure and its vulnerability to damage. To address the aforementioned drawbacks, a novel strategy based on multifunction Janus membranes is presented. In this research, the steel is coated with polyurethane, followed by electrospinning a coating composed of polyurethane nanofibers with kaolin nanoparticles, and finally coated with epoxy resin containing modified ZnO to obtain the Janus membrane. The interface of the Janus membrane is accompanied by covalent bonds, leading to 10-fold enhancement in interface adhesion compared to the resin coating. The obtained Janus coating has a top surface that is superhydrophobic and a bottom surface that is hydrophilic, with excellent antiwetting and antibacterial properties. Moreover, the Janus coating shows outstanding barrier properties and the corresponding impedance modulus is maintained about 109 Ω•cm2 after 75 immersion days. Notably, the coating surface has retained superhydrophobicity after abrasion test with 600-grit sandpaper under a load of 1000 g for 60 m distance. The antibacterial tests have shown the Janus coating could decrease the bacterial coverage on the surface by 25 %. This study has revealed the potential of the Janus electrofibrous membrane as directly coatings on the metallic substrates for the first time, and in this way, multifunction coating with corrosion and fouling protection performances has been achieved.

Janus Zn-IV-VI: Robust Photocatalysts with Enhanced Built-In Electric Fields and Strain-Regulation Capability for Water Splitting.

The use of 2D materials to produce hydrogen (H2 ) fuel via photocatalytic water splitting has been intensively studied. However, the simultaneous fulfillment of the three essential requirements-high photon utilization, rapid carrier transfer, and low-barrier redox reactions-for wide-pH-range production of H2 still poses a significant challenge with noadditional modulation. By employing the first-principles calculations, it has been observed that the Janus ZnXY2 structures (X = Si/Ge/Sn, Y = S/Se/Te) exhibit significantly enhanced built-in electric fields (0.20-0.36eVÅ-1 ), which address the limitations intrinsically. Compared to conventional Janus membranes, the ductile ZnSnSe2 and ZnSnTe2 monolayers have stronger regulation of electric fields, resulting in improved electron mobility and excitonic nature (Ebinding = 0.50/0.35eV). Both monolayers exhibit lower energy barriers of hydrogen evolution reaction (HER, 0.98/0.86eV, pH = 7) and resistance to photocorrosion across pH 0-7. Furthermore, the 1% tensile strain can further boost visible light utilization and intermediate absorption. The optimal AC-type bilayer stacking configuration is conducive to enhancing electric fields for photocatalysis. Overall, Janus ZnXY2 membranes overcome the major challenges faced by conventional 2D photocatalysts via intrinsic polarization and external amelioration, enabling efficient and controllable photocatalysis without the need for doping or heterojunctions.

A non-substrate-specific technique of antifouling and antiwetting Janus membrane fabrication for membrane distillation

Although Janus membranes (comprising a hydrophilic antifouling layer on a wetting-resistant membrane substrate) have shown promise in sustainable membrane distillation (MD) processes for treating industrial wastewaters, most fabrication methods are substrate-specific and lack a universal technique for robust Janus MD membranes. Here, we present a non-substrate-specific technique using polydopamine-assisted, surface-initiated atom-transfer radical-polymerization (ATRP) that grafts a zwitterionic polymer layer onto any wetting-resistant substrate. We first prepare a model omniphobic substrate by surface fluorination of a quartz fiber mat, followed by polydopamine-assisted ATRP to complete Janus membrane fabrication. The grafting of zwitterionic polymer layer with a tunable thickness (∼1–10 μm) on one side of the membrane surface, while preserving the omniphobicity of the membrane substrate, is demonstrated. The binding robustness of the two layers of disparate wettability is then shown. An excellent antifouling functionality of the Janus membrane is confirmed by complete oil detachment in a static oil-fouling test, and by the stable desalination with nearly perfect salt rejection (> 99 %) in direct contact MD using a surfactant-stabilized, crude oil-in-brine emulsion, as simulated high-salinity industrial wastewater feed. Finally, we apply our modification technique to other lab-fabricated as well as commercial non-wetting substrates to demonstrate its universal applicability for Janus membrane fabrication.

Asymmetric Triple-Functional Janus Membrane for Blood Oxygenation.

The oxygenation membrane, a core material of extracorporeal membrane oxygenation (ECMO), is facing challenges in balancing anti-plasma leakage, gas exchange efficiency, and hemocompatibility. Here, inspired by the asymmetric structural features of alveolus pulmonalis, a novel triple-functional membrane for blood oxygenation with a Janus architecture is proposed, which is composed of a hydrophobic polydimethylsiloxane (PDMS) layer to prevent plasma leakage, an ultrathin polyamide layer to enhance gas exchange efficiency with a CO2 :O2 permeance ratio of ≈10.7, and a hydrophilic polyzwitterionic layer to improve the hemocompatibility. During the simulated ECMO process, the Janus oxygenation membrane exhibits excellent performance in terms of thrombus formation and plasma leakage prevention, as well as adequate O2 transfer rate (17.8 mL min-1 m-2 ) and CO2 transfer rate (70.1 mL min-1 m-2 ), in comparison to the reported oxygenation membranes. This work presents novel concepts for the advancement of oxygenation membranes and demonstrates the application potential of the asymmetric triple-functional Janus oxygenation membrane in ECMO.

Janus superwetting fabric for effective emulsion separation

Abstract Superwetting membranes have superior advantages in the treatment of oil contaminated wastewater, especially when it is in an emulsified state. However, these types of membranes suffer from size-sieving limitations. Here, a Janus membrane was constructed by integration of superhydrophobic/underwater superoleophilic and superhydrophilic/underwater superoleophobic fabrics. Under gravity induced flow, water rapidly passes from the superhydrophobic to the superhydrophilic sides of this membrane while oil droplets are retained by the superwetting interface via an “attraction-aggregation-coalescence” process, realizing highly efficient emulsion separation.

A Flexible Aptameric Graphene Field‐Effect Nanosensor Capable of Automatic Liquid Collection/Filtering for Cytokine Storm Biomarker Monitoring in Undiluted Sweat

AbstractA wearable sensor capable of directly detecting cytokines in external secretions external to the human body is pivotal for gauging the intensity of the immune response and circumventing inflammatory storms, a significant clinical concern. The detection of low‐concentration cytokines is often hampered due to interference from impurities in secretions. Addressing this challenge, a wearable detection system is developed by integrating a Janus membrane with water auto‐collection/filtering capabilities, and aptamer‐modified graphene field‐effect transistor sensors, enabling the detection of low‐concentration cytokines in undiluted sweat samples. The Janus membrane can automatically filter external secretions and transport them to the sensor surface, effectively eliminating impurity interference and enhancing the sensor's detection capabilities. The device can sensitively detect cytokines (such as TNF‐α, a marker for inflammation and cancer) in undiluted sweat, with a detection range spanning 0.5 to 500 pM, and a detection limit reaching 0.31 pM. The ultra‐flexibility of the sensor is also verified, maintaining stable electrical properties even after enduring up to 50 extreme deformations. These findings indicate that the wearable detection system has the potential to realize low‐concentration cytokines monitoring in the sweat of inflammatory patients, to assist the healthcare system in controlling the body's immune status.

Beyond Symmetry: Exploring Asymmetric Electrospun Nanofiber Membranes for Liquid Separation

AbstractComposite membranes with asymmetric traits have gained attention in liquid separation, featuring gradient chemical and physical attributes that align or oppose mass transfer direction. Chemically asymmetric configurations harness internal driving forces to heighten separation efficiency, rendering them an appealing option for heightened separation efficiency and fouling prevention. Concurrently, the internal hierarchical structure differences within composite membranes—such as fiber‐based structural adjustments and the gradient density of functional layers—yield the dual benefits of effective liquid repelling and heightened transport efficiency. Unlike conventional phase‐change methods, electrospinning technology possesses advantages in constructing and governing composite fibrous membrane materials with asymmetric chemistry and hierarchical structures, driven by its adaptable stacking methodologies. Notably, the inherent pore structure of electrospun nanofibrous membranes emerges as a proven solution for minimizing transport resistance. In recent times, interest has surged in electrospun nanofibrous membranes endowed with internal asymmetric properties. However, the spotlight has predominantly graced Janus membranes, spotlighting opposite wettability on different sides, leaving other facets of asymmetric membrane enhancement somewhat underexplored. This comprehensive work unveils recent strides in design, fabrication, facilitated transport mechanisms, and real‐world liquid separation applications, all under the aegis of electrospun nanofiber membranes, each endowed with distinct asymmetric properties.

Self-induced crystallization to form a shish-kebab structure on PLA-based Janus membrane to promote water transmission and interlayer binding force

Janus membranes are widely used in fields such as oil-water separation and wound dressings due to their asymmetric wetting properties. However, the weak interface binding force between the hydrophobic and hydrophilic layers can affect the liquid transport performance and membrane separation. In this study, we have reported a method using self-induced crystallization to grow shish-kebab (SK) structures in electrospinning polylactic acid-based fiber membranes. Peel testing revealed that the peel load after induced crystallization increased from 0 to 0.05 N to 0.05–0.15 N, and the time for droplets to penetrate from the hydrophobic side to the hydrophilic side decreased from 16S to 3S. This indicates that SK structures can enhance the adhesion between the hydrophilic and hydrophobic interface, as well as facilitating droplet transport. Through the oil-water separation experiment, it was discovered that the presence of SK structures can filter out more microemulsions. For different emulsions (kerosene, petroleum, n-hexane, petroleum ether, tea tree oil), the separation efficiency of Janus-SK membrane increased by 1.67 %, 2.5 %, 3.0 %, 9.7 %, 4.3 %, respectively. The development of Janus membranes has been provided with a new direction.

On-site catalytic wastewater remediation by sustainably produced H2O2 via scalable single-atomic Fe-incorporated Janus membrane

Electrosynthesis of hydrogen peroxide (H2O2) from oxygen is a green and sustainable route toward on-site wastewater treatment. Nevertheless, the performance mismatch of the catalyst species and gas-diffusion components gives rise to low O2 utilization efficiency and limited H2O2 production rate in a practical cell. Herein, we propose a flexible and scalable Janus electrode comprising hydrophilic single-atomic Fe-incorporated catalytic layer and hydrophobic gas-attraction layer. The hydrophobic layer enables efficient oxygen diffusion, and the hollow-structured catalysts allow oxygen gas trapping with a high local oxygen concentration, resulting in a high Faradaic efficiency and fast H2O2 production rate. Accordingly, an 80 h electrocatalytic H2O2 synthesis could be gained at 80 mA cm−2. The Janus electrode delivers a H2O2 selectivity of 92% and a yield of 592 mmol g−1 h−1 in a flow cell. The thus-produced H2O2 allows for an in situ antibiotic removal, with the potential for on-site eco-restoration.

Janus membrane with asymmetric wettability for efficient oil/water separation

The rapid development of society and industry as well as the frequent occurrence of oil spills cause the shortage of fresh water resources, which not only affects human safety and life, but also impedes the world-wide sustainable development. To address these challenges, novel membrane materials with unique wettability properties have gained significant attention, particularly in the field of oil/water separation. In this research, we modified the hydrophobic PET fabric to achieve superhydrophilic characteristics using impregnation method. Subsequently, we electrospun hydrophobic PVDF fibers onto the superhydrophilic fabric surface, and PVDF/Ca10(PO4)6(OH)2@PET Janus membrane with asymmetric wettability was obtained. The membrane has an excellent unidirectional liquid transport capacity, and can effectively separate heavy oil or light oil, the separation efficiency is more than 90 %. The results also show that the Janus membrane can be used under alkaline conditions and has satisfactory tensile resistance and re-use performance. This work provides a new idea for Janus membrane design and effectively improves the application potential of the Janus membrane in the field of oil/water separation.

A study on photocatalytic Janus membrane reactor for direct conversion of low concentration carbon dioxide in air to methane: Effects of combination of two-dimensional carbon nanosheets

Large CO2 emissions cause the greenhouse effect, which threatens human survival. Directly converting CO2 in the air into energy and valuable resources is the most effective way to address the greenhouse effect. Currently, the main problem with CO2 conversion is the poor conversion efficiency owing to low CO2 concentrations in the air. In this study, a Janus membrane with the functions of concentrating CO2 (gas separation layer) and photocatalytic reaction (photocatalytic reaction layer) was fabricated. The Janus membrane directly converted extremely low concentrations of CO2 in the air into CH4. Amine-functionalized graphene oxide was added to regulate the CO2 conversion efficiency and the structure of the gas separation layer. Graphene was added to the photocatalytic reaction layer to suppress electron-hole recombination and increase the probability of excited electrons colliding with CO2. The experimental results showed that the modification of the gas separation layer or the photocatalytic reaction layer effectively increased the CH4 yield of the Janus membrane. By maintaining a balance between the selectivity and permeability coefficients of the gas separation layer, the highest methane yield (8.9 ppm) was obtained. The CH4 yield of the Janus membrane was further improved (8.9 ppm to 11.1 ppm) by modifying the photocatalytic reaction layer with graphene. This study proposes a feasible method for improving the efficiency of the Janus membrane for converting low-concentration CO2 in air to CH4.

Development of a high flux Janus PVDF membrane for oily saline water desalination by membrane distillation via PDA-TEOS-APTES surface modification

Membrane distillation (MD) is a promising approach for water desalination. However, in practice, this process is hindered by poor water flux and severe membrane fouling. In this study, a series of Janus membranes were designed for the desalination of oily saline water via direct contact membrane distillation (DCMD). Janus membranes were fabricated by a simple and facile method, direct deposition of dopamine (DA), tetraethylorthosilicate (TEOS), and aminopropyltriethoxysilane (APTES) on one side of the polyvinylidene fluoride (PVDF) membrane, which was modified by hydrophobic SiO2 nanoparticles. In brief, one side of the optimum Janus membrane was strongly hydrophobic (WCA: 149.7 ± 1°) while another side exhibited in air hydrophilicity (WA: 36.3 ± 1.2°) and underwater superoleophobicity. Additionally, the optimum Janus membrane experienced a remarkable enhancement in water flux, reaching an impressive value of 52.6 kg/m2h, (69.2 % increment compared to the pristine PVDF). Notably, the optimal Janus membrane demonstrated long-term stability and significant resistance toward oil fouling during the DCMD desalination of oily saline water while preserving its rejection and high vapor flux. The applied strategies may offer a fresh perspective on membrane design with efficient performance for MD by a facile method.

A versatile MOF liquids-based Janus fibrous membrane towards complex oil/water separation and heavy metal ions removal

As an emerging material, porous liquids (PLs) have attracted wide attention and are applied in oily wastewater for the effective elimination of heavy metal ions due to their permanent pore structure, mobility, and superhydrophilicity. However, it remains a challenge to further enhance the separation performance of PLs. Here, a novel metal–organic framework (MOF) porous liquid was synthesized and mixed with a polyacrylonitrile (PAN) solution to produce an asymmetrical Janus fibrous membrane by electrostatic spinning technique. Benefiting from the synergistic effect of the electric field and self-migrating properties of MOF PLs, the Janus membranes exhibited ultrahigh flux of 25310.26 L m-2h−1 bar−1, outstanding separation efficiency (reaching up to 99.99 %) in various oil–water emulsions and high antimicrobial activity (>99.9 %). More impressively, the obtained Janus membranes maintained long-term stability, with separation efficiencies consistently as high as 99.5 %. Meanwhile, the porous structure of MOF PLs with abundant active sites and affinity of polyethylene glycol (PEG) flexible chain for metal ions facilitates the adsorption of metal ions with a maximum equilibrium adsorption capacity of 205 mg/g, which is superior to other literature reported. These results demonstrated that the versatile MOF PLs-based Janus fibrous membranes had a promising application prospect in addressing the challenges associated with such wastewater treatment.

A facile two-step method to construct environmental-friendly Janus coconut wood membrane for oil/water separation

The Janus structure and the super hydrophilicity of cellulose inspired to develop of low-cost and environmentally friendly Janus membrane materials with opposite wetting behavior for unidirectional water/oil transport and selective water/oil separation. However, it remains a challenge to prepare pollution-free, fluoride-free, low-cost Janus membranes in a simple way. A facile two-step top-down approach is utilized to prepare the Janus coconut wood (JCW) membrane using natural coconut wood in the transverse direction as raw material. The lignin and hemicellulose were removed from the coconut wood to prepare super-hydrophilic coconut wood (SCW). The SCW was then sprayed with hydrophobic silica gel to form a super-hydrophobic surface on one side which the water contact angle reached 153.4°. It was observed that the Janus membrane maintained chemical stability in highly saline and varied pH conditions, as well as at a long friction distance. Meanwhile, Janus coconut wood membrane oil/water separation devices readily achieve on-demand unidirectional oil/water transportation due to their superior separation efficiency of over 98 % and separation flux of over 4125 L/m2·h. The Janus coconut wood membrane provides a practical and effective solution for separating the oil/water mixture.

Development of Janus membranes with asymmetric wettability for desalination of impaired seawater by direct contact membrane distillation

Membrane distillation (MD) is an emerging technology for direct seawater desalination. The widely employed hydrophobic membranes are susceptible to pore wetting/ fouling in the presence of organic contaminants in seawater. Here, we demonstrate a facile method of preparing Janus membranes with hydrophilic/hydrophobic faces having excellent anti-fouling and anti-wetting properties. The hydrophobic substrate is a PVDF-co-HFP membrane incorporating fluoroalkylsilane (FAS) grafted hydrophobic MIL-53(Al)- a form of metal organic framework (h-MIL-53(Al)), and the hydrophilic coating is prepared by the direct deposition of polydopamine (PDA) (top layer). The optimum membrane exhibited a stable flux of 11 L/m2h and permeate conductivity ∼10 µS/cm for up to 60 h of seawater desalination. The anti-wetting property of the Janus membrane was demonstrated from the stable performance when challenging the membrane with impaired seawater containing low surface tension compounds such as sodium dodecyl sulphate (SDS) and propylene glycol (PG), and oil (hexadecane). The prepared membrane exhibited wetting resistance of 45 h and 18 h when feed was seawater containing 0.3 mM SDS and 3 wt% PG, respectively. The membrane displayed excellent resistance to fouling for desalination from SDS-stabilized hexadecane (500 ppm)/seawater feeds for up to 50 h (5 cycles). The membrane fabricated in this study holds the potential for seawater desalination.

Scalable fabrication of a robust asymmetric superwetting Janus mesh by facile spray-coating for oil–water emulsions separation

Janus membrane with asymmetric wettability are emerging separation materials for the purification of emulsified oil–water mixtures, however, their poor mechanical durability and low-flux without external pressure severely limit their practical application. Herein, a robust superwetting Janus mesh demonstrating a high water contact angle (WCA) difference up to 157° was developed by simply spraying on the stainless steel mesh (SSM), via the superhydrophobic fluorocarbon resin/polyvinylidene fluoride/1H, 1H, 2H, 2H-perfluorodecyltrichlorosilane modified titanium dioxide@carboxylated CNTs (FEVE/PVDF/F-TiO2@CNTs) layer and a superhydrophilic layer consisting epoxy resin/ethylene imine polymer/sodium perfluorooctanoate modified bentonite (EP/PEI/F-Bentonite). By carefully adjusting the surface polar-nonpolar molecule repulsion based on the two oppositely bond energy side and incorporating nano/microstructures to form a stable interfacial oiling/hydration layer, the robust Janus mesh achieved interface demulsification and gravity separation of emulsified oil–water mixtures. The prepared Janus SSM exhibited excellent gravity-driven separation performance, achieving a flux up to 1508.6 L m−2h−1 for water-in-oil (W/O) emulsions, and 843.1 L m−2h−1 for oil-in-water (O/W) emulsions. Additionally, it exhibited high separation efficiency with water rejection above 99.9 % and oil rejection above 99.7 %. Moreover, the prepared Janus mesh with fine uniform nano/microstructures and functionalized groups demonstrated notable reusability and mechanochemical stability after 10 cycles of O/W and W/O emulsion filtration, 100 cycles of sandpaper abrasion, and strong acid/alkali immersion for 7 d. Overall, this study expected to facilitate the fabrication of a robust asymmetric superwetting Janus mesh with enhanced separation properties for highly efficient oily wastewater treatment.

Water-Assisted Programmable Assembly of Flexible and Self-Standing Janus Membranes.

Janus membranes with asymmetric wettability have been considered cutting-edge for energy/environmental-sustainable applications like water/fog harvester, breathable skin, and smart sensor; however, technical challenges in fabrication and accurate regulation of asymmetric wettability limit their development. Herein, by using water-assisted hydrogen-bonded (H-bonded) assembly of small molecules at water/oil interface, a facile strategy is proposed for one-step fabrication of membranes with well-regulable asymmetric wettability. Asymmetric orderly patterns, beneficial for mass transport based on abundant high-permeability sites and large surface area, are constructed on opposite membrane surfaces. Upon tuning water-assisted H-bonding via H-sites/configuration design and temperature/pH modulation, double-hydrophobic, double-hydrophilic, and hydrophobic-hydrophilic membranes are facilely fabricated. The Janus membranes show smart vapor-responsive curling and unidirectional water transport with promising flux of 1158±25Lm-2 h-1 under natural gravity and 31500±670L·(m-2 h-1 bar-1 ) at negative pressure. This bottom-up approach offers a feasible-to-scalable avenue to precise-manipulation of Janus membranes for advanced applications, providing an effective pathway for developing tailor-made self-assembled nanomaterials.

Fabrication and characterization of hydrophobic/hydrophilic dual-layer polyphenyl sulfone Janus membrane for application in direct contact membrane distillation

In this study, single-layer (SL) and dual-layer (DL) polyphenyl sulfone (PPSU) flat sheet nanocomposite Janus membranes were fabricated via a combination of VIPS and NIPS techniques for direct contact membrane distillation (DCMD) for the first time. Hydrophobic silica nanoparticles (SiNP-B) were incorporated into the SL membranes and the top layer of the DL membranes, while hydrophilic silica nanoparticles (SiNP-L) were added into the down layer of the DL membranes. The effect of the SiNP-B concentration (1–5 wt%) and the top layer thickness (50 and 100 μm) on the morphology, mean pore size (MPS), thickness, porosity, surface roughness, water contact angle (WCA), liquid entry pressure, mechanical strength, and thermal conductivity were investigated. All of the membranes showed a finger-like structure surrounded by a sponge-like structure. The membranes were examined in the DCMD of a 35,000 ppm saline solution at different feed temperatures (50–70 °C) and flow rates (250–1000 mL/min). The DL membranes possessed higher fluxes than the SL membranes through increasing MPS and WCA. The DL membrane with a SiNP-B concentration of 2 wt% and a hydrophobic thickness of 50 μm (DL- 2,50) achieved the highest flux (42.68 ± 0.35 kg/m2h) and salt rejection (94.90 %) during 5 h. This membrane has an MPS of 0.22 ± 0.03 μm, a thickness of 201 ± 4 μm, and a porosity of 76 ± 2 %. It could be concluded the proper pore size distribution is the most important factor in achieving a successful DCMD operation.

Directional transport of drug droplets based on structural and wettability gradients on antibacterial Janus wound plaster with hemostatic, antiextravasation, and prehealing properties

The failure of wound healing is majorly attributed to uncontrolled bleeding and bacterial infections. However, developing a wound plaster that can stop bleeding, resist blood extravasation, and realize directional transportation of drugs to promote wound healing remains a significant challenge. Herein, a superhydrophilic/hydrophobic polyvinyl alcohol/chitosan/silver@Thermoplastic polyurethane (PVA/CS/Ag@TPU) Janus membrane with structural and wettability gradients is developed. In this newly developed membrane, water is absorbed from blood via the superhydrophilic layer, which is attached to the wound, and the charge interactions between platelets and the introduced chitosan (CS) promote blood clotting. The capillary pressure resistance (∆p > 0) of the superhydrophilic layer toward the hydrophobic layer prevents blood permeation, thereby reducing blood loss. The favorable ∆p (< 0) of the membrane based on its structural and wettability gradients can realize the directional transportation of drugs that promote wound healing from the hydrophobic to the superhydrophilic layer. The incorporation of CS and silver endows the Janus membrane with intrinsic antibacterial properties (99.9%). The formation of the hydrated layer on the hydrophilic layer imparts a resisting effect, further endowing the membrane with antiadhesion and antibacterial properties. Experiments involving mice with full-thickness skin wounds revealed that the wound-healing rate increased from 87.65% to ~ 100% when the Janus membrane was loaded with the prehealing drug. Moreover, the dressing accelerated wound healing, regenerated epidermal and granulation tissues, promoted collagen formation, and reduced scar size. Thus, this gradient design strategy opens an avenue for the development of next-generation wound dressings.Graphical abstract