Vapor-induced Phase Separation Research Articles

Assessment of the DCMD performances of poly(vinylidene difluoride) vapor-induced phase separation membranes with adjusted wettability via formation process parameter manipulation

Poly(vinylidene difluoride) (PVDF) membranes for direct contact membrane distillation (DCMD) are commonly modified to decrease their wettability by water. Yet, the vapor-induced phase separation (VIPS) process may be a suitable alternative to avoid complex and expensive modifications. Superhydrophobic membranes with a water contact angle >152° were prepared in one single step by adjusting the polymer concentration, dissolution temperature, relative humidity, and exposure time to vapors to 10 wt%, 40 °C, 80 % and 10 min, respectively with N-Methyl-2-pyrrolidone (NMP) as the solvent. Compared to commercial polytetrafluorethylene (PTFE) membrane, the VIPS PVDF membrane showed higher water vapor flux (38 LMH vs 36 LMH), lower flux decline ratio (22 % vs 39 %) and superior salt rejection (99.99 % vs. 99.90 %) in a 3 h-DCMD process. In wetting tests, the VIPS membrane failed for a sodium dodecyl sulfate concentration of 0.2 mM while 0.1 mM was enough to trigger wetting of the commercial membrane. The energy barrier to heterogeneous crystallization was slightly larger for the VIPS membrane, and a higher rejection was measured during scaling tests (99.8 % vs. 94.2 % for PTFE membrane). Finally, the VIPS membrane outperformed the commercial membrane in a long-term test (100 h). These results evidence the suitability of VIPS PVDF membranes for DCMD.

Fast formation of strong symmetric poly (vinylidene fluoride) membranes via a modified VIPS method

BackgroundPolymer membranes for microfiltration and membrane distillation should be skinless and symmetric with a bi-continuous structure. To effectively eliminate the inherently formed skin layer and macrovoids in the membrane, proper modifications of preparation parameters are proposed. MethodsSkinless microporous poly(vinylidene fluoride) (PVDF) membranes with a uniform bi-continuous structure were fabricated through phase inversion processes that combine vapor-induced phase separation (40 °C and 70% relative humidity) and non-isothermal immersion precipitation (22 °C) with casting dopes consisting of triethyl phosphate (TEP), PVDF, and a small amount of glycerol, a nonsolvent. Significant findingsIntroduction of glycerol to the dope solution induces a rapid polymer crystallization upon exposure to water vapor. Experimental results demonstrate that a skinless microporous membrane can be obtained with a short vapor exposure time of 1.5 min. Additionally, the synthesized membrane possesses ideal filtration properties, including high hydrophobicity (contact angle = 113° for both surfaces), high porosity (83%), adequate strength (2.4 N/mm2), and suitable pore size (0.12 μm). This membrane also exhibits superb rejection capability (99%) and high permeation flux (450 LMH) for filtration of poly(methyl methacrylate) particles with an average size of 0.15 μm..

Preparation of an asymmetric membrane via vapor induced phase separation for membrane distillation

Lately, membrane with asymmetric properties of its two sides has shown promising potential in direct contact membrane distillation (DCMD) application, based on the fact that the hydrophilic side of the asymmetric membrane can effectively mitigate wetting and fouling, while the hydrophobic layer facilitate transportation of water vapor to realize separation. We here report an asymmetric membrane prepared via a facile method of vapor induced phase separation (VIPS). Namely, hydrophobic polymer of poly(styrene-block-butadiene-block-styrene) (SBS) and hydrophilic cellulose acetate (CA) were co-dissolved in tetrahydrofuran, and then cast in an ethanol vapor atmosphere to evaporate solvent. After solvent evaporation (within 10 min), the obtained membrane was observed with scanning electron microscope (SEM) to indicate even microstructure of porous network matrix with nodular morphology, and its top surface consisted of SBS only, while microspheres of CA were found to be evenly embedded in the SBS matrix at the bottom side layer. The membrane was further treated with NaOH aqueous solution for CA deacetylation, which was confirmed by attenuated total reflection Fourier transform infrared spectroscopy, SEM and water contact angle (WCA) analyses. The deacetylated CA exposes OH groups to decrease the WCA of the bottom surface greatly. As a result, an asymmetric membrane with large difference in WCA between the top surface and the bottom surface has been obtained. The asymmetric membrane was employed for DCMD to separate an oily saline emulsion containing n-hexadecane, surfactant of Tween 80, and NaCl. The stable flux and high salt rejection of the asymmetric membrane indicate excellent resistance to wetting and fouling, which is attributed to the hydration layer formed by the OH groups of the deacetylated CA at the bottom surface of the membrane. The facile strategy reported in this work implies possible large scale production of the asymmetric membrane that is suitable for membrane distillation application.

Data-Driven Prediction of Janus/Core-Shell Morphology in Polymer Particles: A Machine-Learning Approach.

The majority of research on Janus particles prepared by solvent evaporation-induced phase separation technique uses models based on interfacial tension or free energy to predict Janus/core-shell morphology. Data-driven predictions, in contrast, utilize multiple samples to identify patterns and outliers. Using machine-learning algorithms and explainable artificial intelligence (XAI) analysis, we developed a model based on a 200-instance data set to predict particle morphology. As model features, simplified molecular input line entry system syntax identifies explanatory variables, including cohesive energy density, molar volume, the Flory-Huggins interaction parameter of polymers, and the solvent solubility parameter. Our most accurate ensemble classifiers predict morphology with an accuracy of 90%. In addition, we employ innovative XAI tools to interpret system behavior, suggesting phase-separated morphology to be most affected by solvent solubility, polymer cohesive energy difference, and blend composition. While polymers with cohesive energy densities above a certain threshold favor the core-shell structure, systems with weak intermolecular interactions favor the Janus structure. The correlation between molar volume and morphology suggests that increasing the size of polymer repeating units favors Janus particles. Additionally, the Janus structure is preferred when the Flory-Huggins interaction parameter exceeds 0.4. XAI analysis introduces feature values that generate the thermodynamically low driving force of phase separation, resulting in kinetically stable morphologies as opposed to thermodynamically stable ones. The Shapley plots of this study also reveal novel methods for creating Janus or core-shell particles based on solvent evaporation-induced phase separation by selecting feature values that strongly favor a given morphology.

Photothermal hydrophobic coating with light-trapping and thermal isolated effects for efficient photothermal anti-icing/de-icing

Photothermal materials with self-heating properties are ideal for future anti-icing strategies due to their abilities of reducing the consumption of non-renewable energy and prevent environmental pollution. However, a series of issues including the difficult-to-obtain raw materials, complex preparation techniques and unavoidable heat loss limit the application of photothermal materials in the field of anti-icing. In this work, we provide a strategy for delayed icing and rapid de-icing using a photothermal hydrophobic surface and thermal isolated porous layer. The ubiquitous carbon micro-spheres produced by combustion is used as the photothermal material, which is also as the structural support for the rough surface, providing hydrophobic and efficient light-absorbing performance for the coating. The thermal isolated porous layer prepared by evaporation-induced phase separation can restrict heat transmission to the substrate at maximum, which ensures a prominent increase in the surface temperature of the coating. Under simulated sunlight irradiation, the surface temperature of the prepared coating reached about 95.4 °C for 600 s at room temperature, and the ice layer on the surface of the coating melted in only 55 s at −10 °C. In addition, the hydrophobicity of the coating gives the surface excellent self-cleaning properties, providing the necessary conditions for long term efficient photothermal performance. Thanks to easily available materials, convenient preparation techniques and high energy efficiency, this photothermal hydrophobic coating offers great potential for practical anti/de-icing applications.

Modification of a PES microfiltration membrane to enhance sterile filtration by inhibiting protein adsorption

Microfiltration membranes are increasingly used in sterilization processes in the pharmaceutical industry. However, in the pharmaceutical industry, product loss caused by the adsorption of high value-added proteins to membranes during the sterilization process is a critical problem. Hence, it is necessary to reduce protein adsorption and fouling through the hydrophilic modification of the entire membrane, not just the surface. We developed a method for fabricating a porous poly(ethersulfone) (PES) microfiltration membrane using vapor-induced phase separation (VIPS) and then conducting hydrophilic modification of the membrane. Two types of symmetric membranes with 0.2 μm pores were prepared using two different additives, one of which was an amphiphilic copolymer (Pluronic® PE6400) that is known to increase the hydrophilicity of PES membranes. Both membranes had high water permeability and suitable mechanical strength. However, protein filtration testing, including an adsorption study, revealed that the hydrophilicity imparted by Pluronic was not sufficient to effectively inhibit protein adhesion. In contrast, the modification via the atom transfer radical polymerization of a hydrophilic oligomer (poly(ethyleneglycol) methacrylate) significantly increased the hydrophilicity of the entire membrane while reducing the surface roughness. These properties reduced protein adsorption and membrane fouling, to the benefit of sterile filtration and protein filtration processes.

Fabrication of a porous polymer electrolyte from poly(vinylidene fluoride-hexafluoropropylene) via one-step reactive vapor-induced phase separation for lithium-ion battery

Fabrication of a porous polymer electrolyte from poly(vinylidene fluoride-hexafluoropropylene) via one-step reactive vapor-induced phase separation for lithium-ion battery

A facile fabrication of acid-proof membranes with superhydrophobic high adhesion in air

superhydrophobic surfaces with superhigh adhesion is significant in special engineering applications, but an elaborate superhydrophobic structure is difficult at artificial fabrication. In this study, a poly[2,2′-(4,4′-oxybis(1,4-phenylene)− 5,5′-bibenzimidazoles]-polydimethylsiloxane (OPBI-PDMS) membrane is prepared via a facile vapor-induced phase separation method, which exhibits high contact angle of 154.1°, high water adhesion and high acidic resistance for 200 h. The results indicate that the sponge-like hierarchical structure formed on the sticky surface of OPBI-PDMS membrane, which offers high hydrophobic property and high adhesion in air, based on the capillary action and pinning effect. Coupled with the high acid-proof performance, the OPBI-PDMS blending membrane is successfully applied in the controllable transferring of acid droplets.

Preserved subsurface morphology in NIPS and VIPS laser-induced graphene membranes affects electrically-dependent microbial decontamination

Laser-induced graphene (LIG) is a graphitic material that can be easily formed by CO2-laser irradiation on a variety of carbon-based substrates, including porous polymeric membranes. LIG-membrane formation involves lasing the top surface of a polymeric membrane, and converts essential polymer separation structures to porous LIG foam. However, in previous studies, separation properties could be partly recovered by forming LIG polymer composite layers or by coating the polymeric membrane substrate with trimethylaluminum (TMA) or graphene oxide (GO) to avoid melting or damaging the membrane pore structure and the subsurface polymeric structures during the lasing process. Herein, by optimizing the laser settings and fabrication conditions, we made LIG directly on uncoated porous PES membranes, while preserving the subsurface polymer. The effects of lasing on membrane properties were studied by comparing porous polymeric PES membranes fabricated using the non-solvent induced phase separation (NIPS) or the vapor-induced phase separation (VIPS) method. Membrane fabrication conditions such as the polymer concentration of the casting solution and the exposure time to the non-solvent were varied, and the NIPS method resulted in membranes with a finger-like polymer substructure morphology while the VIPS method resulted in membranes with an asymmetric cellular morphology. LIG-membranes prepared on NIPS membranes resulted in large permeability changes, while LIG on VIPS membranes gave only very minor changes. The antimicrobial activity of these LIG-membranes as porous electrodes was dependent on applied voltage and solution contact time and 4–6 log removal of bacteria at 10 V was achieved. Understanding LIG formation on porous polymeric membranes will minimize processing steps and might lead to electrically conductive membranes with controlled separation properties.

Dialkyl Carbonates as Green Solvents for Polyvinylidene Difluoride Membrane Preparation

Membrane processes are employed in a wide variety of industrial applications such as separation of complex mixtures, hydrogen isolation, CO2 removal, wastewater treatment, etc. Their use allows energy savings on the production cost compared to other traditional separation technologies. Nevertheless, the preparation of membranes not always fulfills sustainability obligations, especially when considering the commonly employed solvents, i.e., N-methyl-2-pyrrolidone and N,N-dimethylformamide, to mention just a few. Dialkyl carbonates (DACs) are well-known green solvents and reagents that have been extensively investigated as safe alternatives to chlorine-based compounds and media such as alkyl halides, phosgene, and chlorinated solvents. Following our recent study on a scale-up procedure to non-commercially available or expensive DACs, herein we report for the first time the application of organic carbonates as green media for membrane preparation. Theoretical thermodynamic studies were first carried out to predict the solubilities in DACs of different polymers commonly employed for membranes preparation. As a result, the use of selected organic carbonates as media for polyvinylidene difluoride membrane preparation was investigated by nonsolvent-induced phase separation (NIPS) and a combination of vapor-induced phase separation (VIPS)-NIPS techniques. Membranes obtained with custom-made DACs displayed greater structural resistances and smaller pore sizes compared to the ones achieved using commercially available cyclic organic carbonates. Data collected showed that it was possible to achieve a wide variety of dense and porous membranes by using a single family of compounds, highlighting once again the great versatility of DACs as green solvents.

Nanosphere-structured hierarchically porous PVDF-HFP fabric for passive daytime radiative cooling via one-step water vapor-induced phase separation

Growing demand for efficient and economical cooling for indoor as well as outdoor applications, especially personal cooling in outdoor environments, is a major global challenge today. Currently, tailored optical structures with spectral selectivity are being used as cooling strategies. However, developing these photonic structures generally requires sophisticated multi-step manufacturing processes and use of multiple solvents which limits their acceptability for large-scale production and cost-effectiveness. Therefore, for the first time, herein we report the fabrication of nanosphere-structured hierarchically porous poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) fibrous fabric via a facile one-step electrospinning process based on water vapor-induced phase separation (WVIPS) technique using single solvent. The fabricated fabric with interconnected nanospheres structure and hierarchically porous fibers possessed large roughness and high specific surface area. Cooling performance of the fabricated PVDF-HFP fabrics was evaluated using skin simulators to mimic human body. The as-prepared PVDF-HFP fabric exhibits a superior average solar reflectance (∼93.7 %) and infrared emittance (∼91.9 %), yielding a temperature drop of ∼19.8 °C and ∼13.2 °C compared to the bare skin simulator and the one covered with cotton fabric, respectively, under solar intensity of ∼950 W m−2. Additionally, excellent hydrophobicity and adsorption make designed fabrics potentially suitable materials for not only radiative cooling but also for waterproof and filtration applications.

Polyethersulfone-TPU blend membrane coated with an environmentally friendly sabja seed mucilage-Cu2 + cross-linked layer with outstanding separation performance and superior antifouling

In this study, membranes were prepared by blending polyethersulfone (PES) with thermoplastic polyurethane (TPU) in order to enhance the mechanical properties of PES membranes. The membranes were fabricated using the vapor-induced phase separation coupled with non-solvent induced phase separation (VIPS-NIPS method) for the purpose of preventing the formation of macro-voids and enhancing the mechanical stability. After the formation of the PES-TPU membranes, a layer of Sabja seed mucilage (SSM), as an eco-friendly low-cost polysaccharide, was fabricated on the membranes surface, and then chelated via Cu2+ ions, in order to enhance the rejection performance of the prepared membranes. The PES-TPU coated with Sabja seed mucilage-Cu2+ (PES-TPU@SSM/Cu) exhibited not only high permeance of 7.97 L/m2.h.bar, but also extraordinary dye and pharmaceutical residue rejection performance of 98.4% methylene blue, 99.5% crystal violet, 98.2% ceftriaxone and 97.6% amoxicillin, arising from the formation of the cross-linked dense SSM/Cu layer. Moreover, all the antifouling parameters of the fabricated membrane were boosted by SSM/Cu coating on the membrane surface and the long-term durability of the membrane was also investigated after 10 days, exhibiting no significant changes in the membrane performance. Furthermore, mechanical properties were remarkably meliorated by TPU addition.

Substrate-independent, robust and functional PVDF-g-IL coating based on tunable surface free energy

Substrate-independent and robust coatings with desired functions are highly demanded in many fields. The fabrication and fundamental theory of them, however, remain challenging for decades. Herein, we aim to elaborate it from a new perspective, in which the challenge has been attributed to the different or even conflicting requirements on surface free energy (SFE) at substrate/coating (bottom) and coating/air (top) interfaces. In this work, a novel strategy has been developed to tailor SFE continuously and reversibly based on counterion exchange. Polyvinylidene fluoride grafted with ionic liquids (PVDF-g-IL) coating with hierarchical surface roughness was fabricated via solution casting and vapor induced phase separation. In the as-prepared specimen, the surface free energy was calculated based on Neumann method. The resultant high SFE (from the counterion of [Cl−] and hierarchical roughness) contributes to the superior bondability of coating/substrate, corresponding to the excellent universality and robustness of PVDF-g-IL coating assessed via T-peeling test. After that, controlled counterion exchange between [Cl−] and [PFO−] (pentadecafluorooctanate anion) has been employed to tailor SFE at top interface. The consequent high/low magnitudes of SFE enable the super-hydrophilic/super-hydrophobic properties at solid/liquid interface while the tunable SFE dominates serial adsorption at multiple-phase interface.

3 stage filtration system utilizing 3 distinct membranes derived from one single dope solution and finely-tuned phase inversion processes

Wastewater treatment by membrane processes requires at least 3 different membranes with performances falling in the microfiltration, ultrafiltration and nanofiltration ranges. Often, the composition of these membranes varies, and their preparation processes may involve several steps and lengthy or costly post-treatment procedures, for instance to endow the membrane with fouling-resistance property. Here, we intended to explore potential routes to simplify the treatment process. We solely used one single casting solution with the purpose of preparing 3 membranes without any post-treatment, that were then implemented in a 3-stage filtration process. This solution contains polyvinylidene fluoride (PVDF), a copolymer of styrene and polyethylene glycol methyl ether methacrylate (PS-r-PEGMA), and a solvent. 3 phase inversion processes: vapor-induced phase separation (VIPS), liquid-induced phase separation (LIPS) and evaporation-induced phase separation (EIPS) were executed to reach the desired membrane properties. Careful examination of the membrane structure, physical properties and permeability prove that the membranes prepared by VIPS (pore size: 0.4–0.8 µm), LIPS (pore size: 0.008–0.09 µm) and a combination of EIPS and LIPS (pore size: 3–6 nm) were suitable for the rejection of large biofoulants such as microalgae, large and small proteins, respectively, despite the presence of the antifouling copolymer that affected the membrane structure. Next, the 3 membranes were used to treat synthetic wastewater containing a mixture of microalgae, bovine serum albumin (BSA) and lysozyme. The first filtration stage permitted to reject almost entirely the Microalgae (99.3–99.5% rejection), the second filtration stage then removed larger proteins (cumulated “Microalgae/protein” rejection of about 93%) while the last stage rejected a large quantity of the smaller protein. The copolymer was also shown to reduce fouling by a 5-fold factor. Hence, this work demonstrates that a complete set of pressure-driven antifouling membranes for full wastewater treatment may be prepared from one single formulation and by phase inversion only.

Electrorheological effect and dielectric properties of Poly(ionic liquid) microspheres with different length of alkyl chain spacer between ion pair and backbone

Imidazolium-based poly(ionic liquid) analogues having different lengths of alkyl chain spacer between ion pair and backbone, named as P[ECnVim][PF6] (n = 2, 3, 6), were synthesized. Then, P[ECnVim][PF6] were transformed into microspheres by an evaporation-induced phase separation method. The influence of the length of alkyl chain spacer on the electro-responsive electrorheological effect and dielectric property of P[ECnVim][PF6] microsphere suspensions were studied. It showed that as the length of alkyl chain spacer increased, the electrorheological effect increased but the working temperature range of electrorheological effect became narrow. By combining dielectric spectra analysis and activation energy measurement, it was clarified that the influence of the length of alkyl chain spacer on electrorheological effect was mainly associated with the change of ionic conductivity and interfacial polarization, which was further related to the change of elastic potential energy of ion motion in P[ECnVim][PF6] with different lengths of alkyl chain spacer between ion pair and backbone. However, the working temperature range of electrorheological effect depended on the change of glass transition temperature with the length of alkyl chain spacer. The result provides the structure-property relationship insight for the design of poly(ionic liquid)-based electro-responsive electrorheological materials.

Recent Advances on the Fabrication of Antifouling Phase-Inversion Membranes by Physical Blending Modification Method.

Membrane technology is an essential tool for water treatment and biomedical applications. Despite their extensive use in these fields, polymeric-based membranes still face several challenges, including instability, low mechanical strength, and propensity to fouling. The latter point has attracted the attention of numerous teams worldwide developing antifouling materials for membranes and interfaces. A convenient method to prepare antifouling membranes is via physical blending (or simply blending), which is a one-step method that consists of mixing the main matrix polymer and the antifouling material prior to casting and film formation by a phase inversion process. This review focuses on the recent development (past 10 years) of antifouling membranes via this method and uses different phase-inversion processes including liquid-induced phase separation, vapor induced phase separation, and thermally induced phase separation. Antifouling materials used in these recent studies including polymers, metals, ceramics, and carbon-based and porous nanomaterials are also surveyed. Furthermore, the assessment of antifouling properties and performances are extensively summarized. Finally, we conclude this review with a list of technical and scientific challenges that still need to be overcome to improve the functional properties and widen the range of applications of antifouling membranes prepared by blending modification.

A Green Stable Antifouling PEGylated PVDF Membrane Prepared by Vapor-Induced Phase Separation.

While green solvents are being implemented in the fabrication of polyvinylidene fluoride (PVDF) membranes, most are not compatible with the vapor-induced phase separation (VIPS) process for which relatively low dissolution temperatures are required. Additionally, preparing antifouling green membranes in one step by blending the polymer with an antifouling material before inducing phase separation remains extremely challenging due to the solubility issues. Here, the green solvent triethyl phosphate (TEP) was used to solubilize both PVDF and a copolymer (synthesized from styrene monomer and poly(ethylene glycol) methyl ether methacrylate). VIPS was then used, yielding symmetric bi-continuous microfiltration membranes. For a 2 wt% copolymer content in the casting solution, the corresponding membrane P2 showed a homogeneous and dense surface distribution of the copolymer, resulting in a high hydration capacity (>900 mg/cm3) and effective resistance to biofouling during the adsorption tests using bovine serum albumin, Escherichia coli or whole blood, with a measured fouling reduction of 80%, 89% and 90%, respectively. Cyclic filtration tests using bacteria highlighted the competitive antifouling properties of the membranes with a flux recovery ratio after two water/bacterial solution cycles higher than 70%, a reversible flux decline ratio of about 62% and an irreversible flux decline ratio of 28%. Finally, these green antifouling membranes were shown to be stable despite several weeks of immersion in water.

Fluoropolymer Membranes for Membrane Distillation and Membrane Crystallization.

Fluoropolymer membranes are applied in membrane operations such as membrane distillation and membrane crystallization where hydrophobic porous membranes act as a physical barrier separating two phases. Due to their hydrophobic nature, only gaseous molecules are allowed to pass through the membrane and are collected on the permeate side, while the aqueous solution cannot penetrate. However, these two processes suffer problems such as membrane wetting, fouling or scaling. Membrane wetting is a common and undesired phenomenon, which is caused by the loss of hydrophobicity of the porous membrane employed. This greatly affects the mass transfer efficiency and separation efficiency. Simultaneously, membrane fouling occurs, along with membrane wetting and scaling, which greatly reduces the lifespan of the membranes. Therefore, strategies to improve the hydrophobicity of membranes have been widely investigated by researchers. In this direction, hydrophobic fluoropolymer membrane materials are employed more and more for membrane distillation and membrane crystallization thanks to their high chemical and thermal resistance. This paper summarizes different preparation methods of these fluoropolymer membrane, such as non-solvent-induced phase separation (NIPS), thermally-induced phase separation (TIPS), vapor-induced phase separation (VIPS), etc. Hydrophobic modification methods, including surface coating, surface grafting and blending, etc., are also introduced. Moreover, the research advances on the application of less toxic solvents for preparing these membranes are herein reviewed. This review aims to provide guidance to researchers for their future membrane development in membrane distillation and membrane crystallization, using fluoropolymer materials.

Double stimuli-responsive isoporous block copolymer membranes upon phase separation strategies

Isoporous membranes from block copolymer commonly involves in the self-assembly and non-solvent induced phase separation (SNIPS), which could improve the selectivity and water permeance. However, such strategy face challenges: (1) to prepare poly (acrylic acid) PAA based block copolymer isoporous membrane with SNIPS method is difficult since PAA is extremely hydrophilic; (2) large consumption of block copolymer and non-solvent (water) might limit its application. Herein, isoporous membranes from Polystyrene-block-poly (acrylic acid) (PS-b-PAA) were well prepared with amine terminated poly(N-isopropylacrylamide) (pNIPAM-NH2) through the SNIPS and the airflow accelerated evaporation induced phase separation methods (acEIPS). Such membranes bear not only regularity in morphological structure, but also high water permeance (1500 L h−1 m−2 bar−1 for the SNIPS, and 3000 L h−1 m−2 bar−1 for the acEIPS). With the participation of pNIPAM-NH2 the consumption of the block copolymer is limited to 7.8 wt % for the SNIPS method, and even to 5.3 wt % for the acEIPS method without non-solvent precipitation process. Besides, the membrane exhibits pH and thermal responsiveness.

Flexible multisensory sensor based on hierarchically porous ionic liquids/thermoplastic polyurethane composites

With the rapid development of wearable electronics and electronic skins, the demand for portable and flexible sensors that can perceive surrounding information, including mechanical forces, temperature, and humidity, is dramatically increasing. Herein, we develop a lightweight and flexible multisensory sensor based on the hierarchically porous ionic liquids (ILs)/thermoplastic polyurethane (TPU) composite by the combination of vapor-induced phase separation technique and ultrasound-assisted anchoring technique. The as-prepared porous TPU@ILs sensor possesses both the strain- and temperature- sensing capabilities. As a strain sensor, it exhibits excellent sensing performance in various aspects, such as ultra-low detection limit (0.5%), ultra-wide sensing range (0.5–600%), fast response/recovery time (100 ms/80 ms), and outstanding durability, attributed to the hierarchically porous microstructure of TPU@ILs composites. Due to the rigid conductivity-temperature dependence of ILs, the designed porous TPU@ILs sensor also possesses outstanding temperature sensing capability, which has both the high temperature resolution (0.05 °C) and ultrawide temperature sensing range (−30–80 °C). This work provides an effective but simple strategy to fabricate high-performance multisensory sensors, which have great potentials in electronic skins and wearable electronics.