Preparation and Characterization of Membranes Formed by Nonsolvent Induced Phase Separation: A Review

Effect of Viscosity and Air Gap within the Spinneret on the Morphology and Mechanical Properties of Hollow-Fiber Polymer Membranes for Separation Performance

Hollow-fiber membranes for nanofiltration were prepared from the blending of Poly (ethylene glycol) (PEG) with Poly (vinyl chloride) (PVC) with different PEG molecular weights (400 and 4000 g/mol) and PVC via a dry/wet spinning process. In the spinning process, the effects of air gap, wind-up speed, dope extrusion rate, and bore extrusion rate were examined. In addition, the different lengths of the center tube, which acted as the inner-side fiber diameter during the preparation of hollow-fiber membranes, were studied. This research was investigated in order to observe the morphological, dielectric, and dynamic mechanical thermal properties to identify a suitable preparation of a hollow-fiber membrane for feasible applications. The morphology of the PVC-580 blended PEG-400 5 weight percent hollow-fiber membrane was seen to have a dense skin on both the inner and outer fiber surface, along with a suitable dope viscosity. Moreover, it offered finger-like substructures that could provide a high applicable feed-stream permeability and selectivity. Finger-like substructures were present on the near inner fiber surface at the controlled center-tube length of 0.3 cm, more so than at the center tube of 1 cm. This was because the solvent and non-solvent in the lumen tube exchanged more quickly than they did in the coagulant bath. The effect of the wind-up speed during the spinning process was significantly influenced by an affordable hollow fiber that can be indicated by the drawing ratio (λ). It was found that the drawing ratio of 3.3 showed a thickness thinner than 2.6 and 2.0, respectively. In summary, a controlled wind-up speed, an acceptable dope viscosity, and-most importantly-an agglomerated time resulted in membrane preparation.

Biocatalytic PEI-PSS membranes through aqueous phase separation: influence of casting solution pH and operational temperature

Biocatalytic membranes combine the separation properties of membranes and the catalytic abilities of enzymes, holding great promise for industries where both purification and conversion are required. In this work, polyelectrolyte complex membranes incorporated with lysozyme were prepared using polyethyleneimine (PEI) and poly(sodium 4-styrenesulfonate) (PSS) through a one-step and mild pH shift aqueous phase separation (APS) approach. The effects of lysozyme addition and casting solution pH on the membrane properties were studied. All the membranes, both with and without added lysozyme, exhibited asymmetric structures with relatively dense top surfaces and porous cross-sections with finger-like macrovoids. The incorporation of lysozyme did not significantly influence the structure and permeability of the formed membranes. The PEI-PSS biocatalytic membranes exhibited temperature dependent enzymatic activity. The activity strongly increased with increased operational temperature, with the highest activity of 4.30 ± 0.15 U cm-2 at 45 °C. This indicates a responsive effect, where a higher temperature leads to some swelling of the polyelectrolyte complex membrane, making the enzyme more accessible to the used substrate. Moreover, the biocatalytic membranes demonstrate desirable enzymatic stability, maintaining 60% activity even after 60 days of storage. This study validates the potential of the water-based APS process as a straightforward approach for integrating enzymes into responsive biocatalytic membranes.

Interconnected Nanoporous Polysulfone by the Self-Assembly of Randomly Linked Copolymer Networks and Linear Multiblocks

Porous materials have attracted considerable attention due to their versatile applications, especially in water purification. Interconnected nanoporous structures are distinguished by their high degree of porosity and resistance to clogging, as well as their insensitivity to nanostructural orientation. Previous works on randomly linked copolymer systems have shown that they can effectively produce disordered cocontinuous nanostructures, which upon removal of one component yield interconnected nanoporous materials. However, the cocontinuous nanomaterials previously developed using polystyrene (PS) and poly(d,l-lactic acid) (PLA) strands, and the resulting interconnected nanoporous PS monoliths, were far too brittle to enable practical use as membranes. Here, we study the self-assembly of randomly linked copolymer networks prepared using blocks of the engineering polymer polysulfone (PSU). A wide cocontinuous regime (spanning 40 wt %) was found for randomly end-linked copolymer networks (RECNs) constructed from PSU and PLA strands, via a combination of mechanical testing, gravimetry, small-angle X-ray scattering, and scanning electron microscopy. The PSU/PLA cocontinuous nanomaterial with symmetric composition showed 2.4 times higher Young's modulus and ∼100 times greater toughness than the corresponding PS/PLA sample. The interconnected nanoporous PSU fabricated after etching of PLA even exhibited 1.6 times greater toughness than PS/PLA prior to PLA removal. To facilitate the production of thin films of cocontinuous nanomaterials, we applied solution-processable randomly linked linear PSU/PLA multiblock polymers onto ultrafiltration membranes. The interconnected nanoporous PSU thin film generated by etching PLA was found to effectively reject 50 nm diameter particles without significantly compromising permeability. This discovery presents a valuable addition to the existing techniques used to fabricate PSU membranes. In contrast to traditional methods, which are sensitive to processing conditions, produce a wide range of pore sizes, and offer limited adjustability of pore size, the current technique is anticipated to enable interconnected PSU membranes with more uniform and tailorable porosity.

Two-Dimensional Piezoelectric Nanofibrous Webs by Self-Polarized Assembly for High-Performance PM0.3 Filtration

Particulate matter (PM) pollution has posed a serious threat to public health, especially the global spread of infectious diseases. Most existing air filtration materials are still subjected to a compromise between removal efficiency and air permeability on account of their stacking bulk structures. Here, we proposed a self-polarized assembly technique to create two-dimensional piezoelectric nanofibrous webs (PNWs) directly from polymer solutions. The strategy involves droplets deforming into ultrathin liquid films by inertial flow, liquid films evolving into web-like architectures by instantaneous phase inversion, and enhanced dipole alignment by cluster electrostatics. The assembled continuous webs exhibit integrated structural superiorities of nanoscale diameters (∼20 nm) of the internal fibers and through pores (∼100 nm). Combined with the wind-driven electrostatic property derived from the enhanced piezoelectricity, the PNW filter shows high efficiency (99.48%) and low air resistance (34 Pa) against PM0.3 as well as high transparency (84%), superlight weight (0.7 g m-2), and long-term stable service life. This creation of such versatile nanomaterials may offer insight into the design and upgrading of high-performance filters.

Facile Lithium Densification Kinetics by Hyperporous/Hybrid Conductor for High-Energy-Density Lithium Metal Batteries

Lithium metal anode (LMA) emerges as a promising candidate for lithium (Li)-based battery chemistries with high-energy-density. However, inhomogeneous charge distribution from the unbalanced ion/electron transport causes dendritic Li deposition, leading to "dead Li" and parasitic reactions, particularly at high Li utilization ratios (low negative/positive ratios in full cells). Herein, an innovative LMA structural model deploying a hyperporous/hybrid conductive architecture is proposed on single-walled carbon nanotube film (HCA/C), fabricated through a nonsolvent induced phase separation process. This design integrates ionic polymers with conductive carbon, offering a substantial improvement over traditional metal current collectors by reducing the weight of LMA and enabling high-energy-density batteries. The HCA/C promotes uniform lithium deposition even under rapid charging (up to 5 mA cm-2) owing to its efficient mixed ion/electron conduction pathways. Thus, the HCA/C demonstrates stable cycling for 200 cycles with a low negative/positive ratio of 1.0 when paired with a LiNi0.8Co0.1Mn0.1O2 cathode (areal capacity of 5.0 mAh cm-2). Furthermore, a stacked pouch-type full cell using HCA/C realizes a high energy density of 344 Wh kg-1 cell/951 Wh L-1 cell based on the total mass of the cell, exceeding previously reported pouch-type full cells. This work paves the way for LMA development in high-energy-density Li metal batteries.

Preparation Method and Application of Porous Poly(lactic acid) Membranes: A Review

Porous membrane technology has garnered significant attention in the fields of separation and biology due to its remarkable contributions to green chemistry and sustainable development. The porous membranes fabricated from polylactic acid (PLA) possess numerous advantages, including a low relative density, a high specific surface area, biodegradability, and excellent biocompatibility. As a result, they exhibit promising prospects for various applications, such as oil-water separation, tissue engineering, and drug release. This paper provides an overview of recent research advancements in the fabrication of PLA membranes using electrospinning, the breath-figure method, and the phase separation method. Firstly, the principles of each method are elucidated from the perspective of pore formation. The correlation between the relevant parameters and pore structure is discussed and summarized, subsequently followed by a comparative analysis of the advantages and limitations of each method. Subsequently, this article presents the diverse applications of porous PLA membranes in tissue engineering, oil-water separation, and other fields. The current challenges faced by these membranes, however, encompass inadequate mechanical strength, limited production efficiency, and the complexity of pore structure control. Suggestions for enhancement, as well as future prospects, are provided accordingly.

Versatile Landscape of Low-k Polyimide: Theories, Synthesis, Synergistic Properties, and Industrial Integration

The development of microelectronics and large-scale intelligence nowadays promotes the integration, miniaturization, and multifunctionality of electronic and devices but also leads to the increment of signal transmission delays, crosstalk, and energy consumption. The exploitation of materials with low permittivity (low-k) is crucial for realizing innovations in microelectronics. However, due to the high permittivity of conventional interlayer dielectric material (k ∼ 4.0), it is difficult to meet the demands of current microelectronic technology development (k < 3.0). Organic dielectric materials have attracted much attention because of their relatively low permittivity owing to their low material density and low single bond polarization. Polyimide (PI) exhibits better application potential based on its well permittivity tunability (k = 1.1-3.2), high thermal stability (>500 °C), and mechanical property (modulus of elasticity up to 3.0-4.0 GPa). In this review, based on the synergistic relationship of dielectric parameters of materials, the development of nearly 20 years on low-k PI is thoroughly summarized. Moreover, process strategies for modifying low-k PI at the molecular level, multiphase recombination, and interface engineering are discussed exhaustively. The industrial application, technological challenges, and future development of low-k PI are also analyzed, which will provide meaningful guidance for the design and practical application of multifunctional low-k materials.

Advances in Polyvinyl Alcohol-Based Membranes for Fuel Cells: A Comprehensive Review on Types, Synthesis, Modifications, and Performance Optimization

Fuel cell technology is at the forefront of sustainable energy solutions, and polyvinyl alcohol (PVA) membranes play an important role in improving performance. This article thoroughly investigates the various varieties of PVA membranes, their production processes, and the numerous modification tactics used to solve inherent problems. Various methods were investigated, including chemical changes, composite blending, and the introduction of nanocomposites. The factors impacting PVA membranes, such as proton conductivity, thermal stability, and selectivity, were investigated to provide comprehensive knowledge. By combining various research threads, this review aims to completely investigate the current state of PVA membranes in fuel cell applications, providing significant insights for both academic researchers and industry practitioners interested in efficient and sustainable energy conversion technologies. The transition from traditional materials such as Nafion to PVA membranes has been prompted by limitations associated with the former, such as complex synthesis procedures, reduced ionic conductivity at elevated temperatures, and prohibitively high costs, which have hampered their widespread adoption. As a result, modern research efforts are increasingly focused on the creation of alternative membranes that can compete with conventional technical efficacy and economic viability in the context of fuel cell technologies.

β-cyclodextrin modified GO ultrafiltration membranes with enhanced antifouling property for water purification

The study investigated the influence of additives on the fabrication of mixed matrix membranes comprising polyethersulfone (PES), with a specific focus on hydrophilicity, flux, morphology, and antifouling properties. Carboxymethyl modified β-cyclodextrin (CMβ-CD) was used to enhance the dispersion and hydrophilicity of graphene oxide (GO), leading to the formation of a hydrophilic and stable composite nanoparticle (CMCD@GO). The hydrophilicity (WCA <51.5°) and water flux (32.6 L.m-2.h-1) of the modified PES membranes (MCDGO-x) were improved by the incorporation of CMCD@GO nanoparticles, while that of PES membrane was 79.7° and 10.6 L.m-2.h-1. The rate of backscattered light intensity (ΔBS) of MCDGO-x suspensions remains stable, suggesting stable dispersion of CMCD@GO in organic solvents. Compared to the bare PES membrane, the MCDGO-x membrane exhibits a thinner active layer and a finger-like structure. The MCDGO-x membrane exhibited excellent naphthenic acids (NAs) rejection (> 93.2%) due to reduced roughness and higher hydrophilicity, while the GO-modified PES membrane (MGO-5) exhibited lower NAs rejection (87.2%). Furthermore, the MCDGO-5 membrane showed higher flux recovery ratio (FRR) of 79.3% compared to MGO-5 membrane (68.5%) after three cycles, indicating the antifouling performance of MCDGO-x for NAs was significantly improved. The combination of CMβ-CD and GO enhance the flux and antifouling properties of PES ultrafiltration membranes, suggesting significant potential for applications in the purification of oil sands process water and the treatment of oily wastewater.

Thin-Film Composite Membrane Compaction: Exploring the Interplay among Support Compressive Modulus, Structural Characteristics, and Overall Transport Efficiency

Water scarcity has driven the demand for water production from unconventional sources and the reuse of industrial wastewater. Pressure-driven membranes, notably thin-film composite (TFC) membranes, stand as energy-efficient alternatives to the water scarcity challenge and various wastewater treatments. While pressure drives solvent movement, it concurrently triggers membrane compaction and flux deterioration. This necessitates a profound comprehension of the intricate interplay among compressive modulus, structural properties, and transport efficacy amid the compaction process. In this study, we present an all-encompassing compaction model for TFC membranes, applying authentic structural and mechanical variables, achieved by coupling viscoelasticity with Monte Carlo flux calculations based on the resistance-in-series model. Through validation against experimental data for multiple commercial membranes, we evaluated the influence of diverse physical parameters. We find that support polymers with a higher compressive modulus (lower compliance), supports with higher densities of "finger-like" pores, and "sponge-like" pores with optimum void fractions will be preferred to mitigate compaction. More importantly, we uncover a trade-off correlation between steady-state permeability and the modulus for identical support polymers displaying varying porosities. This model holds the potential as a valuable guide in shaping the design and optimization for further TFC applications and extending its utility to biological scaffolds and hydrogels with thin-film coatings in tissue engineering.

Facile fabrication of regenerated cellulose-based separators for high-performance lithium-ion batteries by regulating degrees of polymerization

Cellulose-based separators have great application prospects in the field of lithium-ion batteries (LIBs) due to their excellent wettability and thermal stability. However, most current cellulose-based separators come from high-cost nanocellulose and bacterial cellulose. Herein, regenerated cellulose (RC) separators were prepared from dissolving pulp with different degrees of polymerization (DPs) by using the NaOH/urea/thiourea dissolution system as well as a nonsolvent-induced phase separation method. The results showed that the DP of cellulose had a significant influence on the mechanical properties, pore structure, and electrochemical properties of the resultant RC separator. An appropriate increase in the DP could improve the mechanical strength, porosity, and ionic conductivity of the separator. The RC separator with a DP of 599 exhibited the best performance with a porosity of 56.1 %, an average pore size of 305 nm, an electrolyte uptake of 339 %, a tensile strength of 38.3 MPa, and an ionic conductivity of 1.88 mS·cm-1. The lithium-ion battery prepared with the optimal RC separator had a specific capacity of 156.55 mAh/g for 100 cycles at a current density of 0.5 C and a coulombic efficiency of more than 96 %, which was a clear advantage over the commercially available Celgard2400 and cellulose separators. This work makes contributions to the development of high-performance LIBs separators from cellulose.

Enhancing Sensitivity in Gas Detection: Porous Structures in Organic Field-Effect Transistor-Based Sensors

Gas detection is crucial for detecting environmentally harmful gases. Organic field-effect transistor (OFET)-based gas sensors have attracted attention due to their promising performance and potential for integration into flexible and wearable devices. This review examines the operating mechanisms of OFET-based gas sensors and explores methods for improving sensitivity, with a focus on porous structures. Researchers have achieved significant enhancements in sensor performance by controlling the thickness and free volume of the organic semiconductor layer. Additionally, innovative fabrication techniques like self-assembly and etching have been used to create porous structures, facilitating the diffusion of target gas molecules, and improving sensor response and recovery. These advancements in porous structure fabrication suggest a promising future for OFET-based gas sensors, offering increased sensitivity and selectivity across various applications.

Highly Macroporous Polyimide with Chemical Versatility Prepared from Poly(amic acid) Salt-Stabilized High Internal Phase Emulsion Template

Macroporous polymers have gained significant attention due to their unique mass transport and size-selective properties. In this study, we focused on Polyimide (PI), a high-performance polymer, as an ideal candidate for macroporous structures. Despite various attempts to create macroporous PI (Macro PI) using emulsion templates, challenges remained, including limited chemical diversity and poor control over pore size and porosity. To address these issues, we systematically investigated the role of poly(amic acid) salt (PAAS) polymers as macrosurfactants and matrices. By designing 12 different PAAS polymers with diverse chemical structures, we achieved stable high internal phase emulsions (HIPEs) with >80 vol % internal volume. The resulting Macro PIs exhibited exceptional porosity (>99 vol %) after thermal imidization. We explored the structure-property relationships of these Macro PIs, emphasizing the importance of controlling pore size distribution. Furthermore, our study demonstrated the utility of these Macro PIs as separators in Li-metal batteries, providing stable charging-discharging cycles. Our findings not only enhance the understanding of emulsion-based macroporous polymers but also pave the way for their applications in advanced energy storage systems and beyond.

Influence of citric acid concentrations on the porosity and performance of cellulose acetate-based porous membranes: A comprehensive study

This study investigates the influence of citric acid concentration on the fabrication of porous cellulose acetate (CA) membranes using the Non-Solvent Induced Phase Separation (NIPS) method. A notable aspect is the precise control over membrane properties, particularly pore size and porosity, achieved solely through the adjustment of citric acid concentration, serving as the additive. Higher concentrations of citric acid increase pore size by rendering polymer chains more pliable, whereas lower concentrations lead to smaller, denser pores due to improved dispersion in the CA matrix and altered water interactions during phase separation. A decrease in porosity and Gurley values with reducing citric acid concentrations (from 5 × 10-2 to 1 × 10-3 M ratios) indicates less plasticization of CA chains. However, at very low concentrations (1 × 10-4 and 1 × 10-5), porosity increases, despite the presence of smaller pores, and Gurley values approach those of pure CA in terms of gas permeability. Fourier Transform Infrared (FT-IR) spectroscopy confirms the presence of citric acid and its interaction with carbonyl groups, consistent with the pore size observations from Scanning Electron Microscopy (SEM). Spectral data deconvolution reveals weakened carbonyl bonds due to the reduced presence of citric acid, correlating with the smaller pores observed in SEM. Thermal Gravimetric Analysis (TGA) demonstrates that composite membranes are more thermally stable than pure CA, attributed to the citric acid-induced crosslinking within the polymer chains. Stability increases with decreasing citric acid concentration, with some anomalies at the lowest levels. In conclusion, this study highlights the capability of adjusting citric acid concentration to tailor membrane properties, offering valuable insights for the creation of porous materials across diverse industrial applications.

Stochastic kinetic theory applied to coarse-grained polymer model

A stochastic field theory approach is applied to a coarse-grained polymer model that will enable studies of polymer behavior under non-equilibrium conditions. This article is focused on the validation of the new model in comparison with explicit Langevin equation simulations under conditions with analytical solutions. The polymers are modeled as Hookean dumbbells in one dimension, without including hydrodynamic interactions and polymer-polymer interactions. Stochastic moment equations are derived from full field theory. The accuracy of the field theory and moment equations is quantified using autocorrelation functions. The full field theory is only accurate for a large number of polymers due to keeping track of rare occurrences of polymers with a large stretch. The moment equations do not have this error because they do not explicitly track these configurations. The accuracy of both methods depends on the spatial degree of discretization. The timescale of decorrelation over length scales bigger than the spatial discretization is accurate, while there is an error over the scale of single mesh points.

On the Disproportionate Contribution of Membrane Electron Donor Functionality in Membrane Biofouling

This study set out to uncover which interfacial properties have the greatest impact on membrane organic fouling, biofouling, and fouling resistance. A relatively simple manipulation of the basic equations used in determining Lifshitz-van der Waals (LW) and Lewis acid-base (AB) surface tensions for solid materials reveals that the high electron accepticity of water makes the electron donicity of membrane and biofouling materials the key component governing their interfacial free energy of adhesion (ΔG132), which defines the favorability (or unfavorability) of one material (1) adhering to another (2) when immersed in a liquid (3). Various biofoulant and membrane LW and AB surface tensions were systematically characterized. Static bacterial adhesion, alginic acid filtration, and wastewater filtration tests were conducted to determine the fouling propensities of three different polymeric membrane materials. Experimental results of microbial adhesion, alginate fouling, and biofouling tests all correlated well with membrane electron density, where higher electron density produced less organic fouling or biofouling. These combined theoretical and experimental results confirm the importance of surface electron donicity in determining the fouling propensity of polymeric membranes.

Zwitterionic Tröger's Base Microfiltration Membrane Prepared via Vapor-Induced Phase Separation with Improved Demulsification and Antifouling Performance

The fouling of separation membranes has consistently been a primary factor contributing to the decline in membrane performance. Enhancing the surface hydrophilicity of the membrane proves to be an effective strategy in mitigating membrane fouling in water treatment processes. Zwitterionic polymers (containing an equimolar number of homogeneously distributed anionic and cationic groups on the polymer chains) have been used extensively as one of the best antifouling materials for surface modification. The conventional application of zwitterionic compounds as surface modifiers is intricate and inefficient, adding complexity and length to the membrane preparation process, particularly on an industrial scale. To overcome these limitations, zwitterionic polymer, directly used as a main material, is an effective method. In this work, a novel zwitterionic polymer (TB)-zwitterionic Tröger's base (ZTB)-was synthesized by quaternizing Tröger's base (TB) with 1,3-propane sultone. The obtained ZTB is blended with TB to fabricate microfiltration (MF) membranes via the vapor-induced phase separation (VIPS) process, offering a strategic solution for separating emulsified oily wastewater. Atomic force microscopy (AFM), scanning electron microscopy (SEM), water contact angle, and zeta potential measurements were employed to characterize the surface of ZTB/TB blended membranes, assessing surface morphology, charge, and hydrophilic/hydrophobic properties. The impact of varying ZTB levels on membrane surface morphology, hydrophilicity, water flux, and rejection were investigated. The results showed that an increase in ZTB content improved hydrophilicity and surface roughness, consequently enhancing water permeability. Due to the attraction of water vapor, the enrichment of zwitterionic segments was enriched, and a stable hydration layer was formed on the membrane surface. The hydration layer formed by zwitterions endowed the membrane with good antifouling properties. The proposed mechanism elucidates the membrane's proficiency in demulsification and the reduction in irreversible fouling through the synergistic regulation of surface charge and hydrophilicity, facilitated by electrostatic repulsion and the formation of a hydration layer. The ZTB/TB blended membranes demonstrated superior efficiency in oil-water separation, achieving a maximum flux of 1897.63 LMH bar-1 and an oil rejection rate as high as 99% in the oil-water emulsion separation process. This study reveals the migration behavior of the zwitterionic polymer in the membrane during the VIPS process. It enhances our comprehension of the antifouling mechanism of zwitterionic membranes and provides guidance for designing novel materials for antifouling membranes.

Investigating microstructure evolution in block copolymer membranes

Block copolymer self-assembly in conjunction with nonsolvent-induced phase separation (SNIPS) has been increasingly leveraged to fabricate integral-asymmetric membranes. The large number of formulation and processing parameters associated with SNIPS, however, has prevented the reliable construction of high performance membranes. In this study, we apply dynamical self-consistent field theory to model the SNIPS process and investigate the effect of various parameters on the membrane morphology: solvent selectivity, nonsolvent selectivity, initial film composition, and glass transition composition. We examine how solvent selectivity and concentration of polymers in the film impact the structure of micelles that connect to form the membrane matrix. In particular, we find that preserving the order in the surface layer and forming a connection between the supporting and surface layer are nontrivial and sensitive to each parameter studied. The effect of each parameter is discussed, and suggestions are made for successfully fabricating viable block copolymer membranes.

Porous Structure of Polymer Films Optimized by Rationally Tuning Phase Separation for Passive All-Day Radiative Cooling

Passive all-day radiative cooling (PARC) films with porous structures prepared via nonsolvent-induced phase separation (NIPS) have attracted considerable attention owing to their cost-effectiveness and wide applicability. The PARC performances of the films correlate with their porous structures. However, the porous structure formed using the NIPS process cannot be finely regulated. In this study, we prepared polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) films with porous structures optimized by rationally tuning the phase separation, which was achieved by adjusting the proportions of two good solvents with varying solubility parameters. The optimized PVDF-HFP film with a hierarchically porous structure exhibited a high solar reflectance of 97.7% and an infrared emissivity of 96.7%. The film with excellent durability achieved an average subambient cooling temperature of approximately 5.4 °C under a solar irradiance of 945 W·m-2 as well as a temperature of 11.2 °C at nighttime, thus demonstrating all-day radiative cooling. The results indicate that the proposed films present a promising platform for large-scale applications in green building cooling and achieving carbon neutrality.

Does pervasive interconnected network of cellulose nanocrystals in nanocomposite membranes address simultaneous mechanical strength/water permeability/salt rejection improvement?

In this research work, we investigated the effect of two cellulose nanocrystal (CNC)-related parameters, namely aspect ratio and loading content on the mechanical and desalination performance of a cellulose diacetate (CDA) model membrane system. Dispersion of high aspect ratio (HAR) CNCs in the CDA resulted in different types of nanoassembly, represented by evaluating the mechanical efficacy coefficient (CFE), viscoelastic responses and separation performance of the nanocomposite membranes. Accordingly, 0.15 and 0.25 wt% showed random isolated dispersion and tight polymer-nanorod network, while 0.50 and 0.75 wt% conformed to nanorods' pervasive interconnected network (PIN) through side-by-side aggregation and intensive bundle alignment, respectively. Specifically, the nanocomposite membrane containing 0.50 wt% HAR-CNCs simultaneously demonstrated improved mechanical strength along with mitigated water permeability/salt rejection tradeoff for brackish water desalination. This concurrent boosting was attributed to the effective mechanical reinforcement mechanism induced by the percolating network along with its partial aggregation-caused bi-continuous and electrostatically-controlled nano-pathways, orchestrating the separation tradeoff. It confirmed our hypothesis that a nanocomposite membrane with metamaterial characteristic could be obtained via manipulating the dispersion state of CNC rods in the CDA, triggering coincided optimization of mechanical strength and desalination performance.

Highly Stretchable Thermoplastic Polyurethane Separators for Li-Ion Batteries Based on Non-Solvent-Induced Phase Separation Method

The growing interest in wearable and portable devices has stimulated the need for flexible and stretchable lithium-ion batteries (LiBs). A crucial component in these batteries is the separator, which provides a pathway for Li-ion transfer and prevents electrode contact. In a flexible and stretchable LiB, the separator must exhibit stretchability and elasticity akin to its existing counterparts. Here, we developed a non-modified thermoplastic polyurethane (TPU) separator using the non-solvent induced phase separation (NIPS) technique. We compared their performance with commercially available polypropylene (PP) separators. Our results demonstrate that TPU separators exhibit superior elasticity based on repeated stretch/release tests with excellent thermal stability and electrolyte wettability. Furthermore, our findings confirm that TPU separators, even after being repeatedly stretched and released, can function effectively without severe damage in a fabricated coin cell LiB with high oxidative stability, as evidenced by linear sweep voltammetry, like commercially available separators.

Utilization of polyphenylene sulfide as an organic additive to enhance gas separation performance in polysulfone membranes

Many studies have shown that sulfur-containing compounds significantly affect the solubility of carbon dioxide (CO2) in adsorption processes. However, limited attention has been devoted to incorporating organic fillers containing sulfur atoms into gas separation membrane matrices. This study addressed the gap by developing a new membrane using a polysulfone (PSf) polymer matrix and polyphenylene sulfide (PPs) filler material. This membrane could be used to separate mixtures of H2/CH4 and CO2/CH4 gases. Our study investigated the impact of various PPs loadings (1%, 5%, and 10% w/w) relative to PSf on membrane properties and gas separation efficiency. Comprehensive characterization techniques, including Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM), were employed to understand how adding PPs and coating with polydimethylsiloxane (PDMS) changed the structure of our membranes. XRD and FTIR analysis revealed distinct morphological disparities and functional groups between pure PSf and PSf/PPs composite membranes. SEM results show an even distribution of PPs on the membrane surface. The impact of adding PPs on gas separation was significant. CO2 permeability increased by 376.19%, and H2 permeability improved by 191.25%. The membrane's gas selection ability significantly improved after coating the surface with PDMS. CO2/CH4 separation increased by 255.06% and H2/CH4 separation by 179.44%. We also considered the Findex to assess the overall performance of the membrane. The 5% and 10% PPs membranes were exceptional. Adding PPs to membrane technology may greatly enhance gas separation processes.

Tough polycyclooctene nanoporous membranes from etchable block copolymers

Porous materials with pore dimensions of the nanometer length scale are useful as nanoporous membranes. ABA triblock copolymers are convenient precursors to such nanoporous materials if the end blocks are easily degradable (e.g., polylactide or PLA), leaving nanoporous polymeric membranes (NPMs) if in thin film form. The membrane properties are dependent on midblock monomer structure, triblock copolymer composition, overall molar mass, and polymer processing conditions. Polycyclooctene (PCOE) NPMs were prepared using this method, with tunable pore sizes on the order of tens of nanometers. Solvent casting was shown to eliminate film defects and allowed achievement of superior mechanical properties over melt processing techniques, and PCOE NPMs were found to be very tough, a major advance over previously reported NPMs. Oxygen plasma etching was used to remove the surface skin layer to obtain membranes with higher surface porosity, membrane hydrophilicity, and flux of both air and water. This is a straightforward method to reliably produce highly tough NPMs with high levels of porosity and hydrophilic surface properties.

Elastic microphase separation produces robust bicontinuous materials

Bicontinuous microstructures are essential to the function of diverse natural and synthetic systems. Their synthesis has been based on two approaches: arrested phase separation or self-assembly of block copolymers. The former is attractive for its chemical simplicity and the latter, for its thermodynamic robustness. Here we introduce elastic microphase separation (EMPS) as an alternative approach to make bicontinuous microstructures. Conceptually, EMPS balances the molecular-scale forces that drive demixing with large-scale elasticity to encode a thermodynamic length scale. This process features a continuous phase transition, reversible without hysteresis. Practically, EMPS is triggered by simply supersaturating an elastomeric matrix with a liquid, resulting in uniform bicontinuous materials with a well-defined microscopic length scale tuned by the matrix stiffness. The versatility of EMPS is further demonstrated by fabricating bicontinuous materials with superior mechanical properties and controlled anisotropy and microstructural gradients. Overall, EMPS presents a robust alternative for the bulk fabrication of homogeneous bicontinuous materials.

Microstructural Characterization of PCL-HA Bone Scaffolds Based on Nonsolvent-Induced Phase Separation

Composite materials containing pores play a crucial role in the field of bone tissue engineering. The nonsolvent-induced phase separation (NIPS) technique, commonly used for manufacturing membranes, has proven to be an effective method for fabricating composite scaffolds with tunable porosity. To explore this potential, we produced 10% (w/v) poly(caprolactone) (PCL)-nanohydroxyapatite (HA) composite porous film scaffolds with varying HA contents (0/10/15/20 wt %) and two thicknesses (corresponding to 1 and 2 mL of solution resulting in 800-900 and 1600-1800 μm thickness, respectively) using the NIPS method. We conducted a comprehensive analysis of how the internal microstructure and surface characteristics of these scaffolds varied based on their composition and thickness. In particular, for each scaffold, we analyzed overall porosity, pore size distribution, pore shape, and degree of anisotropy as well as mechanical behaviors. Micro-CT and SEM analyses revealed that PCL-HA scaffolds with various HA contents possessed micro (<100 μm) scale porosity due to the NIPS method. Greater thicknesses typically resulted in larger average pore sizes and greater overall porosity. However, unlike in thinner scaffolds, greater/higher HA content did not exhibit a direct correlation with a greater pore size for thicker scaffolds. In thinner scaffolds, adding HA above an effective threshold content of 15 wt % and beyond did lead to a greater pore size. The higher pore anisotropy was in line with the higher HA content for both groups. SEM images demonstrated that both groups showed highly uniformly distributed internal microporous morphology regardless of HA content and thickness. The results suggest that NIPS-based scaffolds hold promise for bone tissue engineering but that the optimal HA content and thickness should be carefully considered based on desired porosity and application.

Coarsening dynamics of ternary polymer solutions with mobility and viscosity contrasts

Using phase-field simulations, we investigate the bulk coarsening dynamics of ternary polymer solutions undergoing a glass transition for two models of phase separation: diffusion only and with hydrodynamics. The glass transition is incorporated in both models by imposing mobility and viscosity contrasts between the polymer-rich and polymer-poor phases of the evolving microstructure. For microstructures composed of polymer-poor clusters in a polymer-rich matrix, the mobility and viscosity contrasts significantly hinder coarsening, effectively leading to structural arrest. For microstructures composed of polymer-rich clusters in a polymer-poor matrix, the mobility and viscosity contrasts do not impede domain growth; rather, they change the transient concentration of the polymer-rich phase, altering the shape of the discrete domains. This effect introduces several complexities to the coarsening process, including percolation inversion of the polymer-rich and polymer-poor phases-a phenomenon normally attributed to viscoelastic phase separation.

Printed sustainable elastomeric conductor for soft electronics

The widespread adoption of renewable and sustainable elastomers in stretchable electronics has been impeded by challenges in their fabrication and lacklustre performance. Here, we realize a printed sustainable stretchable conductor with superior electrical performance by synthesizing sustainable and recyclable vegetable oil polyurethane (VegPU) elastomeric binder and developing a solution sintering method for their composites with Ag flakes. The binder impedes the propagation of cracks through its porous network, while the solution sintering reaction reduces the resistance increment upon stretching, resulting in high stretchability (350%), superior conductivity (12833 S cm-1), and low hysteresis (0.333) after 100% cyclic stretching. The sustainable conductor was used to print durable and stretchable impedance sensors for non-obstructive detection of fruit maturity in food sensing technology. The combination of sustainable materials and strategies for realizing high-performance stretchable conductors provides a roadmap for the development of sustainable stretchable electronics.

A Magnesium Carbonate Hydroxide Nanofiber/Poly(Vinylidene Fluoride) Composite Membrane for High-Rate and High-Safety Lithium-Ion Batteries

Simultaneously high-rate and high-safety lithium-ion batteries (LIBs) have long been the research focus in both academia and industry. In this study, a multifunctional composite membrane fabricated by incorporating poly(vinylidene fluoride) (PVDF) with magnesium carbonate hydroxide (MCH) nanofibers was reported for the first time. Compared to commercial polypropylene (PP) membranes and neat PVDF membranes, the composite membrane exhibits various excellent properties, including higher porosity (85.9%) and electrolyte wettability (539.8%), better ionic conductivity (1.4 mS·cm-1), and lower interfacial resistance (93.3 Ω). It can remain dimensionally stable up to 180 °C, preventing LIBs from fast internal short-circuiting at the beginning of a thermal runaway situation. When a coin cell assembled with this composite membrane was tested at a high temperature (100 °C), it showed superior charge-discharge performance across 100 cycles. Furthermore, this composite membrane demonstrated greatly improved flame retardancy compared with PP and PVDF membranes. We anticipate that this multifunctional membrane will be a promising separator candidate for next-generation LIBs and other energy storage devices, in order to meet rate and safety requirements.

Artificial intelligence and structural design of inorganic hollow fiber membranes: Materials chemistry

A key challenge is to produce the uniform morphology and regular pore design of inorganic hollow fiber membranes (HFMs) due to involvement of multiple parameters including, fabrication process and materials chemistry. Inorganic HFMs required technical innovations via novel structural design and artificial intelligence (AI) to produce the uniform structure and regular pore design. Therefore, this review aims at critical analysis on the most recent and relevant approaches to tackle the issues related to tune the morphology and pore design of inorganic HFMs. Structural design and evaluation of routes towards the dope suspension, spinning, and sintering of inorganic HFMs are critically analysed. AI, driving forces and challenges involved for harnessing of materials are revealed in this review. AI programs used for the prediction of pore design and performance of HFMs have also been explained in this review. Overall, this review will provide the understanding to build the equilibrium in spinning and sintering processes to control the design of micro-channels, and structural properties of inorganic HFMs. This review has great significance to control the new design of membranes via AI programs. This review also explain the inorganic membrane efficiency as algal-bioreactor.

Thermodynamics and kinetic analysis of membrane: Challenges and perspectives

The ultimate structure of the membrane is determined using two important effects: (i) thermodynamic effect and (ii) kinetic effect. Controlling the mechanism of kinetic and thermodynamic processes in phase separation is essential for enhancing membrane performance. However, the relationship between system parameters and the ultimate membrane morphology is still largely empirical. This review focuses on the fundamental ideas behind thermally induced phase separation (TIPS) and nonsolvent-induced phase separation (NIPS) methods, including both kinetic and thermodynamic elements. The thermodynamic approach to understanding phase separation and the effect of different interaction parameters on membrane morphology has been discussed in detail. Furthermore, this review explores the capabilities and limitations of different macroscopic transport models used for the last four decades to explore the phase inversion process. The application of molecular simulations and phase field to understand phase separation has also been briefly examined. Finally, it discusses the thermodynamic approach to understanding phase separation and the consequence of different interaction parameters on membrane morphology, as well as possible directions for artificial intelligence to fill the gaps in the literature. This review aims to provide comprehensive knowledge and motivation for future modeling work for membrane fabrication via new techniques such as nonsolvent-TIPS, complex-TIPS, non-solvent assisted TIPS, combined NIPS-TIPS method, and mixed solvent phase separation.

Additive Manufacturing of High-Temperature Thermoplastic Polysulfone with Tailored Microstructure via Precipitation Printing

Current additive manufacturing processes for polymers, including material extrusion, vat photopolymerization, material jetting, and powder bed fusion, have limitations in manufacturing high-temperature thermoplastics including narrow material selection, compromised mechanical properties, and potential degradation of materials during processing. Polysulfone (PSU) is a high-temperature thermoplastic with outstanding chemical resistance, flame retardancy, and toughness. However, besides injection molding, additive manufacturing of PSU has only been achieved through extrusion or solvent-cast three-dimensional (3D) printing without obtaining high mechanical properties. In this work, precipitation printing is applied to fabricate high-temperature thermoplastics such as PSU for the first time, where tailoring of the microstructure and mechanical properties is enabled through control of solvents and printing parameters. The printed PSU can either be dense and strong with 2.47 GPa Young's modulus and 70.6 MPa tensile strength or porous and highly anisotropic. After drying at a maximum temperature of 190 °C, both the printed dense and porous PSU samples have a glass-transition temperature of about 200 °C, which allows them to be used in high-temperature environments. Thus, precipitation printing provides an alternative approach to manufacture high-temperature thermoplastics like PSU with scalability and tailorable properties.

Optimization, Kinetics, and Isotherm Studies of Methyl Thioninium Chloride Removal from Simulated Solutions Using Chitosan Derivatives

Methylene blue (MB) dye or methyl thioninium chloride is one of the hazardous cationic dyes that are discharged into the textile effluent causing a highly negative environmental impact. The present work targets the investigation of the adsorption performance of some chitosan-modified products toward the MB dye from simulated solutions. The claimed chitosan derivatives were prepared, characterized, and applied for the removal of lead and copper cations from an aqueous medium in a previous work. These include: N,O-carboxymethyl chitosan (N,O-CM/Cs), chitosan grafted with glutaraldehyde (Cs/GA), chitosan cross-linked with GA/epichlorohydrin (Cs/GA/ECH), and chitosan cross-linked with glutaraldehyde/methylene bis(acrylamide) (Cs/GA/MBA). The modified chitosan derivatives in this study displayed outstanding mechanical qualities, exceptional reusability, and a significant amount of adsorption capacity. The ability of prepared Cs derivatives to eradicate MB was as follows: N,O-CM/Cs (95.1 mg/g) < Cs/GA (120.1 mg/g) < Cs/GA/ECH (220.1 mg/g) < Cs/GA/MBA (270.0 mg/g). The swelling performance of the prepared sorbents was verified under different experimental conditions, and the data revealed that the maximum swelling was attained at pH = 9, temperature 55 °C, and after 24 h. The produced Cs derivatives showed exceptional reusability by maintaining higher adsorption effectiveness throughout five cycles. The MB dye was adsorbed onto the modified derivatives according to pseudo-second-order kinetics and the Langmuir model. Moreover, the adsorption process was monitored via atomic force microscopy to verify the differences between the dye-free and dye-loaded adsorbents.

Controlled Structuring of Hyaluronan Films by Phase Separation and Inversion

This work explores application of phase separation phenomena for structuring of films made from hyaluronan. A time-sequenced dispensing of different solution mixtures was applied under rotation of hyaluronan-covered substrates to generate surface textures. This method is applicable in direct surface modification or cover layer deposition. Changes in the surface topography were characterized by atomic force microscopy, optical microscopy, and contact and non-contact profilometry. The mechanical properties of the surface-modified self-supporting films were compared using a universal testing machine. Experimental results show that diverse hyaluronan-based surface reliefs and self-supporting films with improved mechanical properties can be prepared using a newly designed multi-step phase separation process without the need for sacrificial removable templates or additives.

Modified polysulfone membrane facilitates rapid separation of plasma from whole blood for an effective anti-SARS-CoV-2-IgM diagnosis

During the outbreak of coronavirus, RT-PCR was the premier gold standard method for severe acute respiratory syndrome coronavirus 2 (SARSCoV-2) diagnosis. However, the sophisticated procedure of RT-PCR persuades researchers to develop sustainable point-of-need immunoassay methods for tracing unwitting carriers of SARSCoV-2. Herein, by fabricating a modified polysulfone (MPSF) membrane, we developed an integrated radial flow immunoassay (IRFIA) platform as a point-of-care system, capable of multiplying the immunoassays at a short run time. The target molecule is the SARSCoV-2 IgM in separated plasma. Although the lateral flow immunoassay kits for the rapid identification of Covid-19 have already been commercially developed but, the proposed method is superior to the conventional lateral flow immunoassay. In the newly designed membrane system, we have combined the five membranes of prevalent lateral flow immunoassay (LFIA) strips in one polymeric membrane. The MPSF membrane is capable of separating plasma from whole blood sample, which will reduce the interference of red colour of hemoglobin with generated signal and enhance the immunoassay precision. The efficiency of plasma separation, reached the mean value of 97.34 v/v% in 5 s. Furthermore, the gel electrophoresis results of the separated plasma contrasted with centrifuged plasma sample, demonstrated more efficient separation by the membrane. Using the MPSF membrane, signal generation time reduced from about 20 min in conventional rapid test strip for Covid-19 to about 7 min in IRFIA platform. The sensitivity and specificity of the membrane platform were determined to be 89% and 90%, respectively and a Kappa coefficient of 0.79 showed reliable agreement between the RT-PCR and the membrane system.

Fast Fabrication of Porous Amphiphilic Polyamides via Nonconventional Evaporation Induced Phase Separation

In the present work, we report a facile approach for the fast fabrication of porous films and coatings of long-chain polyamides through a nonconventional evaporation induced phase separation. Because of its amphiphilic nature, polyamide 12 can be dissolved in the mixture of a high-polarity solvent and a low-polarity solvent, while it could not be dissolved in either solvent solely. The sequential and fast evaporation of the solvents leads to the formation of porous structures within 1 min. Moreover, we have investigated the dependence of the pore structures on composition of the solutions, and have demonstrated that our approach can be applied to other long-chain polycondensates, too. Our findings can provide insight on the fabrication of porous materials by using amphiphilic polymers.

The Effect of Non-Solvent Nature on the Rheological Properties of Cellulose Solution in Diluted Ionic Liquid and Performance of Nanofiltration Membranes

The weak point of ionic liquids is their high viscosity, limiting the maximum polymer concentration in the forming solutions. A low-viscous co-solvent can reduce viscosity, but cellulose has none. This study demonstrates that dimethyl sulfoxide (DMSO), being non-solvent for cellulose, can act as a nominal co-solvent to improve its processing into a nanofiltration membrane by phase inversion. A study of the rheology of cellulose solutions in diluted ionic liquids ([EMIM]Ac, [EMIM]Cl, and [BMIM]Ac) containing up to 75% DMSO showed the possibility of decreasing the viscosity by up to 50 times while keeping the same cellulose concentration. Surprisingly, typical cellulose non-solvents (water, methanol, ethanol, and isopropanol) behave similarly, reducing the viscosity at low doses but causing structuring of the cellulose solution and its phase separation at high concentrations. According to laser interferometry, the nature of these non-solvents affects the mass transfer direction relative to the forming membrane and the substance interdiffusion rate, which increases by four-fold when passing from isopropanol to methanol or water. Examination of the nanofiltration characteristics of the obtained membranes showed that the dilution of ionic liquid enhances the rejection without changing the permeability, while the transition to alcohols increases the permeability while maintaining the rejection.

Non-Equilibrium Block Copolymer Self-Assembly Based Porous Membrane Formation Processes Employing Multicomponent Systems

Porous polymer-derived membranes are useful for applications ranging from filtration and separation technologies to energy storage and conversion. Combining block copolymer (BCP) self-assembly with the industrially scalable, non-equilibrium phase inversion technique (SNIPS) yields membranes comprising periodically ordered top surface structures supported by asymmetric, hierarchical substructures that together overcome performance tradeoffs typically faced by materials derived from equilibrium approaches. This review first reports on recent advances in understanding the top surface structural evolution of a model SNIPS-derived system during standard membrane formation. Subsequently, the application of SNIPS to multicomponent systems is described, enabling pore size modulation, chemical modification, and transformation to non-polymeric materials classes without compromising the structural features that define SNIPS membranes. Perspectives on future directions of both single-component and multicomponent membrane materials are provided. This points to a rich and fertile ground for the study of fundamental as well as applied problems using non-equilibrium-derived asymmetric porous materials with tunable chemistry, composition, and structure.

Printability of Poly(lactic acid) Ink by Embedded 3D Printing via Immersion Precipitation

Immersion precipitation three-dimensional printing (ip3DP) and freeform polymer precipitation (FPP) are unique and versatile methods of 3D printing to fabricate 3D structures based on nonsolvent-induced phase separation via direct ink writing (DIW). Immersion precipitation involves complex dynamics among solvents, nonsolvents, and dissolved polymers, and the printability of 3D models in these methods requires further understanding. To this end, we characterized these two methods of 3D printing using polylactide (PLA) dissolved in dichloromethane (7.5-30% w/w) as model inks. We analyzed the rheological properties of the solutions and the effect of printing parameters on solvent-nonsolvent diffusion to achieve printability. The PLA inks exhibited shear-thinning properties, and their viscosities varied over three orders of magnitude (10^-1∼10² Pa·s). A processing map was presented to understand the ideal ranges of the concentration of PLA in inks and the nozzle diameter to ensure printability, and the fabrication of complex 3D structures was fabricated with adequate applied pressure and nozzle speed. The processing map also highlighted the advantages of embedded 3D printing over solvent-cast 3D printing based on solvent evaporation. Lastly, we demonstrated that the porosity of the interface and inner structure of the printed objects was readily tailored by the concentration of the PLA and the porogen added to the ink. The methods presented here offer new perspectives to fabricate micro-to-centimeter objects of thermoplastics with nanometer-scale inner pores and provide guidelines for successful embedded 3D printing based on immersion precipitation.

Closed-loop recyclable membranes enabled by covalent adaptable networks for water purification

In the state-of-the-art membrane industry, membranes have linear life cycles and are commonly disposed of by landfill or incineration, sacrificing their sustainability. To date, little or no thought is given in the design phase to the end-of-life management of membranes. For the first time, we have innovated high-performance sustainable membranes, which can be closed-loop recycled after long-term usage for water purification. By synergizing membrane technology and dynamic covalent chemistry, covalent adaptable networks (CANs) with thermally reversible Diels-Alder (DA) adducts were synthesized and employed to fabricate integrally skinned asymmetric membranes via the nonsolvent-induced phase separation technique. Due to the stable and reversible features of CAN, the closed-loop recyclable membranes exhibit excellent mechanical properties and thermal and chemical stabilities as well as separation performance, which are comparable to or even higher than the state-of-the-art nonrecyclable membranes. Moreover, the used membranes can be closed-loop recycled with consistent properties and separation performance by depolymerization to remove contaminants, followed by refabrication into new membranes through the dissociation and reformation of DA adducts. This study may fill in the gaps in closed-loop recycling of membranes and inspire the advancement of sustainable membranes for a green membrane industry.

Fluid Flow Templating of Polymeric Soft Matter with Diverse Morphologies

It is challenging to find a conventional nanofabrication technique that can consistently produce soft polymeric matter of high surface area and nanoscale morphology in a way that is scalable, versatile, and easily tunable. Here, the capabilities of a universal method for fabricating diverse nano- and micro-scale morphologies based on polymer precipitation templated by the fluid streamlines in multiphasic flow are explored. It is shown that while the procedure is operationally simple, various combinations of its intertwined mechanisms can controllably and reproducibly lead to the formation of an extraordinary wide range of colloidal morphologies. By systematically investigating the process conditions, 12 distinct classes of polymer micro- and nano-structures including particles, rods, ribbons, nanosheets, and soft dendritic colloids (dendricolloids) are identified. The outcomes are interpreted by delineating the physical processes into three stages: hydrodynamic shear, capillary and mechanical breakup, and polymer precipitation rate. The insights into the underlying fundamental mechanisms provide guidance toward developing a versatile and scalable nanofabrication platform. It is verified that the liquid shear-based technique is versatile and works well with many chemically diverse polymers and biopolymers, showing potential as a universal tool for simple and scalable nanofabrication of many morphologically distinct soft matter classes.

Using Excimer Laser for Manufacturing Stimuli Responsive Membranes

A 248 nm KrF excimer laser can be used to manufacture temperature and pH-responsive polymer-based membranes for controlled transport applications. This is done by a two-step approach. In the first step, well-defined/shaped and orderly pores are created on commercially available polymer films by ablation by using an excimer laser. The same laser is used subsequently for energetic grafting and polymerization of a responsive hydrogel polymer inside the pores fabricated during the first step. Thus, these smart membranes allow controllable solute transport. In this paper, determination of appropriate laser parameters and grafting solution characteristics are illustrated to obtain the desired membrane performance. Fabrication of membranes with 600 nm to 25 μm pore sizes by using the laser through different metal mesh templates is discussed first. Laser fluence and the number of pulses need to be optimized to obtain the desired pore size. Mesh size and film thickness primarily control the pore sizes. Typically, pore size increases with increasing fluence and the number of pulses. Larger pores can be created by using higher fluence at a given laser energy. The vertical cross-section of the pores turns out to be inherently tapered due to the ablative action of the laser beam. The pores created by laser ablation can be grafted with PNIPAM hydrogel by using the same laser to perform a bottom-up grafting-from type pulsed laser polymerization (PLP) in order to achieve the desired transport function controlled by temperature. For this purpose, a set of laser frequencies and pulse numbers need to be determined to obtain the desired hydrogel grafting density and the extent of cross-linking, which ultimately provide controlled transport by smart gating. In other words, on-demand switchable solute release rates can be achieved by controlling the cross-linking level of the microporous PNIPAM network. The PLP process is extremely fast (few seconds) and provides higher water permeability above the lower critical solution temperature (LCST) of the hydrogel. Experiments have shown high mechanical integrity for these pore-filled membranes, which can sustain pressures up to 0.31 MPa. The monomer (NIPAM) and cross-linker (mBAAm) concentrations in the grafting solution need to be optimized in order to control the network growth inside the support membrane pores. The cross-linker concentration typically has a stronger effect on the temperature responsiveness. The pulsed laser polymerization process described can be extended to different unsaturated monomers, which can be polymerized by the free radical process. For example, poly(acrylic acid) can be the grafted to provide pH responsiveness to membranes. As for the effects of thickness, a decreasing trend is observed in the permeability coefficient with increasing thickness. Furthermore, the film thickness has little or no effect on PLP kinetics. The experimental results have shown that membranes manufactured by excimer laser are excellent choices for applications where flow uniformity is the prime requirement, as they possess uniform pore sizes and distribution.

In Situ Incorporation of TiO2@Graphene Oxide (GO) Nanosheets in Polyacrylonitrile (PAN)-Based Membranes Matrix for Ultrafast Protein Separation

Organic polymeric ultrafiltration (UF) membranes have been widely used in protein separation due to their advantages of high flux and simple manufacturing process. However, due to the hydrophobic nature of the polymer, pure polymeric UF membranes need to be modified or hybrid to increase their flux and anti-fouling performance. In this work, tetrabutyl titanate (TBT) and graphene oxide (GO) were simultaneously added to the polyacrylonitrile (PAN) casting solution to prepare a TiO₂@GO/PAN hybrid ultrafiltration membrane using a non-solvent induced phase separation (NIPS). During the phase separation process, TBT underwent a sol-gel reaction to generate hydrophilic TiO₂ nanoparticles in situ. Some of the generated TiO₂ nanoparticles reacted with the GO through a chelation interaction to form TiO₂@GO nanocomposites. The resulting TiO₂@GO nanocomposites had higher hydrophilicity than the GO. They could selectively segregate towards the membrane surface and pore walls through the solvent and non-solvent exchange during the NIPS, significantly improving the membrane's hydrophilicity. The remaining TiO₂ nanoparticles were segregated from the membrane matrix to increase the membrane's porosity. Furthermore, the interaction between the GO and TiO₂ also restricted the excessive segregation of the TiO₂ nanoparticles and reduced their losing. The resulting TiO₂@GO/PAN membrane had a water flux of 1487.6 L·m^-2·h^-1 and a bovine serum albumin (BSA) rejection rate of 99.5%, which were much higher than those of the currently available UF membranes. It also exhibited excellent anti-protein fouling performance. Therefore, the prepared TiO₂@GO/PAN membrane has important practical applications in the field of protein separation.

Next-generation ultrafiltration membranes: A review of material design, properties, recent progress, and challenges

Membrane technology utilizing ultrafiltration (UF) processes has emerged as the most widely used and cost-effective simple process in many industrial applications. The industries like textiles and petroleum refining are promptly required membrane based UF processes to alleviate the potential environmental threat caused by the generation of various wastewater. At the same time, major limitations such as material selection as well as fouling behavior challenge the overall performance of UF membranes, particularly in wastewater treatment. Therefore, a complete discussion on material design with structural property relation and separation performance of UF membranes is always exciting. This state-of-the-art review has exclusively focused on the development of UF membranes, the material design, properties, progress in separation processes, and critical challenges. So far, most of the review articles have examined the UF membrane processes through a selected track of paving typical materials and their limited applications. In contrast, in this review, we have exclusively aimed at comprehensive research from material selection and fabrication methods to all the possible applications of UF membranes, giving more attention and theoretical understanding to the complete development of high-performance UF systems. We have discussed the methodical engineering behind the development of UF membranes regardless of their materials and fabrication mechanisms. Identifying the utility of UF membrane systems in various applications, as well as their mode of separation processes, has been well discussed. Overall, the current review conveys the knowledge of the present-day significance of UF membranes together with their future prospective opportunities whilst overcoming known difficulties in many potential applications.

Highly stretchable porous regenerated silk fibroin film for enhanced wound healing

Silk fibroin (SF) has received interest in tissue engineering owing to its biocompatibility, biodegradability, and favorable mechanical properties. However, the complex preparation, brittleness, and lack of pores in the structure of the silk fibroin film limit its application. Herein, we show that facile dissolution of SF in aqueous phosphoric acid followed by regeneration in aqueous ammonium sulfate ((NH₄)₂SO₄) could afford highly stretchable films with nano-pores formed in the nonsolvent-induced phase separation process. The named phase separation, which determines the morphology and mechanical properties of the regeneration silk fibroin (RSF) films, is highly dependent on the (NH₄)₂SO₄ concentration as well as the initial concentration of the SF solution. Therefore, the RSF films exhibit a tunable pore size ranging from 230 to 510 nm and excellent stretchability with tensile strain up to 143 ± 16%. Most interestingly, the RSF films were shown to support the proliferation of human skin fibroblasts in vitro as well as speed up full-thickness skin wound healing in a rat model. This work establishes an easy and feasible method to access porous RSF membranes that can be used for wound dressing in clinical settings.

Polyimide-Based Solid-State Gel Polymer Electrolyte for Lithium-Oxygen Batteries with a Long-Cycling Life

Metal-air batteries have attracted wide interest owing to their ultrahigh theoretical energy densities, particularly for lithium-oxygen batteries. One of the challenges inhibiting the practical application of lithium-oxygen batteries is the unavoidable liquid electrolyte evaporation accompanying oxygen fluxion in the semi-open system, which leads to safety issues and poor cyclic performance. To address these issues, we propose a solid-state polyimide based gel polymer electrolyte (PI@GPE), immobilizing and reserving a liquid electrolyte in the gelled polymer substrate. The liquid electrolyte uptake of PI@GPE is measured to be 842%, 6 times higher than that of the commercial glass fiber separator, contributing to a high ionic conductivity of 0.44 mS cm^-1. Additionally, PI@GPE possesses an enhanced lithium transference number of 0.596 as well as superior interfacial compatibility with lithium metals. Under 0.1 mA cm^-2 and 0.25 mA h cm^-2, PI@GPE-based lithium-oxygen batteries demonstrate distinguished long-cycling stability of 366 cycles, 4 times more than that with a glass fiber separator and liquid electrolyte. Our work provides a unique solid-state gel polymer electrolyte to mitigate liquid electrolyte leakage, exhibiting promising potential application in highly safe lithium-oxygen batteries with a long-cycling life.