Thermally Induced Phase Separation Research Articles

Porous Hybrid PVDF/BiFeO3 Smart Composite with Magnetic, Piezophotocatalytic, and Light-Emission Properties

The creation of multi-stimuli-sensitive composite polymer–inorganic materials is a practical scientific task. The combination of photoactive magneto-piezoelectric nanomaterials and ferroelectric polymers offers new properties that can help solve environmental and energy problems. Using the doctor blade casting method with the thermally induced phase separation (TIPS) technique, we synthesized a hybrid polymer–inorganic nanocomposite porous membrane based on polyvinylidene fluoride (PVDF) and bismuth ferrite (BiFeO3/BFO). We studied the samples using transmission and scanning electron microscopy (TEM/SEM), infrared Fourier spectroscopy (FTIR), total transmission and diffuse reflection, fluorescence microscopy, photoluminescence (PL), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), vibrating-sample magnetometer (VSM), and piezopotential measurements. Our results demonstrate that the addition of BFO increases the proportion of the polar phase from 76.2% to 93.8% due to surface ion–dipole interaction. We also found that the sample exhibits laser-induced fluorescence, with maxima at 475 and 665 nm depending on the presence of nanoparticles in the polymer matrix. Furthermore, our piezo-photocatalytic experiments showed that under the combined actions of ultrasonic treatment and UV–visible light irradiation, the reaction rate increased by factors of 68, 13, 4.2, and 1.6 compared to sonolysis, photolysis, piezocatalysis, and photocatalysis, respectively. This behavior is explained by the piezoelectric potential and the narrowing of the band gap of the composite due to the mechanical stress caused by ultrasound.

Structure and properties of 3D resorbable scaffolds based on poly(L-lactide) via salt-leaching combined with phase separation

In tissue engineering, polymer-based scaffolds play an important role via cell adhesion, proliferation, and tissue regeneration in three-dimensional (3D) structures, exhibiting great potential in a variety of tissues. For fabrication of scaffolds, the particulate-leaching method and thermally-induced phase separation (TIPS) are popular procedures. However, a complete interconnectivity of the porous structure has not been ensured. We have prepared PLLA-based 3D scaffolds with high porosity by the combination of TIPS with NaCl salt-leaching technique. Interconnectivity and cellular infiltration were improved by humidity treatment in the preparation of the scaffolds. By optimization of the parameters of scaffold pore morphologies and cellular penetration, potent 3D resorbable polymeric scaffolds using combinatory method was demonstrated.

Modified poly (4-methyl-1-pentene) membranes by surface segregation for blood oxygenation

Oxygenation membranes in extracorporeal membrane oxygenation (ECMO) with excellent gas permeability, good hemocompatibility and durable resistance to plasma leakage is the key to achieve long-term and efficient blood oxygenation. This study put forward surface segregation strategy in thermally induced phase separation (TIPS) of poly (4-methyl-1-pentene) (PMP) membranes to realize the in-situ surface modification. Heterostructured PMP membranes with hydrophilic hemocompatible surface and hydrophobic body were obtained by migration of hydrophilic segments of the amphiphilic block copolymer Pluronic F127 to the surface in their preparation process. The hydrophilic surface could effectively improve hemocompatibility of membranes through hydration layer effect and steric hindrance effect, also reduce platelet adhesion significantly, and prolong the coagulation time of the four coagulation items within the normal physiological range of human body. When adding 10 wt% F127, the membrane exhibited an optimum CO2 permeance of ∼11461 GPU and O2 permeance of ∼13335 GPU, respectively, and an optimized blood oxygenation performance in vitro with O2 flux of 122.9 ml min−1 m−2 and CO2 flux of 129.2 ml min−1 m−2, and the asymmetric structure ensures resistance to plasma leakage for more than two months, that showed great application potential. Besides, preparation of hollow fiber membranes based on surface segregation was also explored, aiming to realize the enhanced performance and large-scale preparation of PMP oxygenation membranes. The membranes prepared in this work exhibited an outstanding performance when applied in blood oxygenation, showing great application potentials.

Control of Particle Properties in Thermally-Induced Precipitation of Polyetherimide.

The feasibility of thermally-induced phase separation and crystallization for the production of semi-crystalline polyetherimide (PEI) microparticles from an amorphous feedstock has been reported recently. Here, we investigate process parameter dependencies for designing and control of particle properties. A stirred autoclave was used to extend the process controllability, as the applied process parameters, e.g., stirring speed and cooling rate, were adjusted. By increasing the stirring speed, the particle size distribution was shifted to larger values (correlation factor ρ = 0.77). Although, the enhanced droplet breakup, induced by the higher stirring speed, led to the formation of smaller particles (ρ = -0.68), broadening the particle size distribution. The cooling rate showed a significant influence on the melting temperature, reducing it with a correlation factor of ρ = -0.77, as confirmed by differential scanning calorimetry. Lower cooling rates led to larger crystalline structures and enhanced the degree of crystallinity. The polymer concentration mainly affected the resulting enthalpy of fusion, as an increased polymer fraction enhanced the latter (correlation factor ρ = 0.96). In addition, the circularity of the particles was positively correlated to the polymer fraction (ρ = 0.88). The structure assessed via X-ray diffraction, was not affected.

Polyamide 11 nanocomposite feedstocks for powder bed fusion via liquid-liquid phase separation and crystallization

Within this contribution, the incorporation of nanoparticles (SiO2, Al2O3, TiO2) into the matrix of precipitated polyamide particles during thermally induced phase separation (TIPS) is demonstrated. The obtained polymer composite powders are tailored for their application in powder bed fusion (PBF). The flexible process allows to tune and adapt the powder properties to meet specific challenges like narrow particle size distribution, spherical particles, high additive contents and good distribution of the additive within the powder.Thermogravimetric analysis and electron microscopy prove the incorporation of the nano-sized additive into the matrix of the polymer. The influence of the additive material during polymer precipitation on the particle size distribution and shape of the powders is discussed. Thermal properties of the composite powders were assessed by dynamic and isothermal DSC for subsequent Avrami analysis. The observed acceleration of the crystallization kinetics could be attributed to the nucleating effect of the additive.All powders showed an easy-flowing (flow index ffC > 4) behavior. This allowed the deposition of homogeneous powder layers during PBF experiments also at high temperatures. The processability of the composite powders in the PBF process was demonstrated by single layer experiments.

Combined effects of nanoparticle and stretch‐induced orientation on crystal structure and properties of UHMWPE/TiO2 composite microporous membranes

AbstractThe nanocomposite microporous membrane of ultra‐high molecular weight polyethylene (UHMWPE) and nano‐titanium dioxide (nano‐TiO2) system was prepared by combining the thermally induced phase separation (TIPS) technique with the extrusion‐casting process using liquid paraffin (LP) as the diluent. The effects of variations of TiO2 content and melt draw ratio on the properties of composite microporous membranes were studied and the optimal processing parameters were further investigated. ATR‐FTIR demonstrated that nanocomposite microporous membranes were successfully prepared. The crystallization behavior and morphological evolution of membranes were systematically investigated by WAXD, 2D‐SAXS, and SEM. It was found that the stretch‐induced orientation of UHMWPE was promoted and the shish‐kebab structure was formed for the reason of addition of TiO2. The mechanism of combined effects of nanoparticles and stretch‐induced orientation on the crystallization behavior of UHMWPE was further discussed and explained. Compared to pure UHMWPE film, the permeability of the optimum performance film was significantly improved, with porosity of 49% and pure water flux of about 193 L m−2 h−1. Mechanical studies showed that nanoparticles and DR have significant effects on tensile strength and elongation at break. In addition, the thermal stability of composite microporous membranes was found to be improved with the increase of TiO2 content and melt draw ratio. Thus, this investigation delivers inspiration for the expansion of excellent performance microporous membranes used for battery separators and filtration devices.

Development of porous polyketone membrane via liquid–liquid thermally induced phase separation

In recent years, polyketone (PK) porous membranes have attracted significant attention in separation technology owing to its high tolerance to organic solvents. However, its excellent solvent resistance complicates PK membrane preparation procedure, requiring the use of toxic solvents in the conventional nonsolvent induced phase separation (NIPS) method. In this study, the thermally induced phase separation (TIPS) method was explored to prepare porous membranes with PK homopolymer and copolymer. By screening many diluents, we found potential diluents that could be applied to the TIPS method for PK membrane preparation. Two kinds diluent (PEG300 and DPrP) for CPK and one kind pure diluent (PEG200) for HPK were screened to induce L-L phase separation. In the membrane preparation by the liquid–liquid (L-L) phase separation system, the influence of the PK type, cooling conditions, and polymer concentration on the final membrane structure was investigated. Finally, the porous structure, water permeance, and mechanical properties of the membranes prepared using the NIPS and TIPS methods were compared. Prepared CPK and HPK membrane with 25 wt% concentration by TIPS method showed high water permeability (400 and 480 L m−2h−1bar−1) and tensile strength (4.6 and 4.9 MPa). This study will facilitate the development of high-performance PK membranes using the TIPS method, particularly in the selection of diluents.

C-shaped porous polypropylene fibers for rapid oil absorption and effective on-line oil spillage monitoring

Development of efficient absorbent materials for detection and treatment of offshore oil spillages remained a challenge. In this work, C-shaped polypropylene oil-absorbent fibers with sub-micron internal pores were prepared by combining spun-bonding technique and thermally induced phase separation (TIPS). The effect of drawing speed on the phase separation and the porous morphology of the shaped fiber non-woven fabric (NWF) was investigated. C-shaped NWF with porous morphology had large water contact angle, higher porosity, larger specific surface area, and increased oil absorption speed and capacity. An online oil spillage detection system was developed using porous C-shaped NWF and an oxygen sensing probe, showing shorter response time and higher signal-to-noise (STN) ratio. The response time for detecting the spillage of soybean oil and diluted crude oil (0.5 mL/0.8 L) in water were only 24 s and 10 s, respectively. The reliable oil detection low detection limit (RLDL) of the oxygen sensing probe was reduced 173 times (from 36.5 g/L to 0.21 g/L) when combined with C-shaped porous fiber NWF.

Fabrication of 3D Hierarchically Porous Chitosan Monoliths by Thermally Induced Phase Separation of Chemically Modified Chitin

Chitosan (CS), an amino-polysaccharide, has applications in various areas such as drug delivery, biotechnology, food technology, and numerous industrial applications. Monoliths have been developed continuously for several decades, and today, they hold an impressively strong position in highly efficient separation, ion exchange, catalysis, and chromatography. In our previous study, a hierarchical chitin (CT) monolith was fabricated using chemically modified CT through the thermally induced phase separation (TIPS) method. This report generated a template-free approach to prepare highly effective, stable, and reusable hierarchically porous CS monoliths by deacetylation of CT monoliths. The acquired CS monoliths exhibited a high surface area at 144.1 m2 g–1 owing to the presence of hierarchical macro- and mesopores. The monoliths demonstrated efficient removal of metal ions from an aqueous solution in a flow system (adsorption capacity at 92.1 mg g–1). To gain durability of CS monoliths in acidic and basic environments, epichlorohydrin (ECH) was used as a cross-linking agent. The cross-linked monoliths also exhibited excellent performance in the adsorption of Cu(II) ions from the solution (64.4 mg g–1) and good reusability in multiple adsorption–desorption cycles without losing significant performance (with 90.7 ± 6.1% adsorption efficiency and 88.5 ± 7.2% desorption efficiency). The fabricated CS monolith can be modified and applied to various fields such as protein separation, catalysis, and drug delivery.

Novel multiscale simulations on the membrane formation via hybrid induced phase separation process based on dissipative particle dynamics

A novel simulation methodology, that was based on dissipative particle dynamics (DPD) combined with information from molecular dynamics (MD) and calculations of an extended Maxwell-Stefan (MS) equations, was established to obtain multiscale analysis on the dynamics of hybrid induced phase separation (HIPS), taking polyvinylidene fluoride-diphenyl carbonate/water–ethanol (PVDF-DPC/water–ethanol) system as an example. Firstly, MS equations were derived to describe the heat transfer across the interface between the casting solution and coagulation to get the temperature profiles of the casting solution. Secondly, MD simulations for the PVDF-DPC solution were conducted to acquire bond and angle distributions of the PVDF chains. And compared to the DPD particle distributions, a novel DPD force field to describe the real flexibility of PVDF chains and a coarse-graining mapping between the MD and DPD were developed. Thirdly, based on the quenching time calculated by the MS equations and the DPD time scale, DPD simulations were carried out to demonstrate the dynamics of phase separation and membrane formation for different parts of the polymer solution via HIPS and compared to that via thermally induced phase separation (TIPS). The simulation results indicated that the mass transfer had a decisive effect on the phase separation of polymer solution near the interface and resulted in a highly asymmetric structure with a denser polymer top layer and porous sublayer, and this effect was together decided by the quenching rate and polymer solidification. For the inner parts of the polymer solution, a mainly isotropic structure was formed due to heat transfer. Based on experimental verification and simulation results, it can be known that the multiscale simulation was much closer to reality and can provide deep insights into the membrane formation prepared via the HIPS process.

Preparation of Poly(4-methyl-1-pentene) Membranes by Low-Temperature Thermally Induced Phase Separation

As a widely used method for the preparation of membranes, thermally induced phase separation (TIPS) is usually performed at high temperatures (200–260 °C) and has the disadvantages of high energy consumption, usage of large amounts of solvents, and easy decomposition of polymers. To solve these problems, this article presents a low-temperature thermally induced phase separation (LT-TIPS) method for the preparation of porous poly(4-methyl-1-pentene) (PMP) membranes at 70 °C. The PMP/cyclohexane solution was cast on a glass plate and quenched in water for a few minutes, and then the solvent was recovered by vacuum evaporation and condensation. The effects of quenching medium, quenching temperature, time, wet membrane thickness, and polymer concentration on the membrane porosity and air permeability were studied. The results showed that the elevated quenching temperature and extended quenching time in water favor the increase of air permeability. The increase of wet membrane thickness and polymer concentration results in reduced air permeability. The method displays convenience in process control, low energy consumption, less solvent usage, easy recovery of solvent, and environmental friendliness, exhibiting great promises for the preparation of membranes.

Chemical cleaning and membrane aging of poly(vinylidene fluoride) (PVDF) membranes fabricated via non-solvent induced phase separation (NIPS) and thermally induced phase separation (TIPS)

Poly(vinylidene fluoride) (PVDF) is one of the most used membrane materials in the water industries, and the PVDF membrane can be fabricated majorly through non-solvent induced phase separation (NIPS) and thermally induced phase separation (TIPS). The differences in membrane aging of NIPS-PVDF and TIPS-PVDF remain unclear. In this study, the agings of commercially available NIPS-PVDF and TIPS-PVDF membranes were investigated in the pilot-scale MBRs experiment as well as in the batch soaking tests. The raw PVDF powders in different crystalline polymorphs were also subjected to aging tests to examine the relation between PVDF polymorphous structure and aging. The results showed that the NIPS-PVDF membrane experienced more severe aging in the pilot-scale MBR experiment in comparison with the TIPS-PVDF membrane. Acid aging dislodged and eliminated the additives in the membrane, but did not attack the PVDF. NIPS-PVDF membrane was the dominant β PVDF phase, which was more susceptible to dehydrochlorination in alkaline oxide aging. The thin top layer in the asymmetric structure of the NIPS-PVDF membrane resulted in its vulnerability against alkaline oxide aging. The α PVDF phase and the symmetric structure of the TIPS-PVDF membrane contributed to its greater stability in alkaline oxide aging. Overall, the results can provide a basis for selecting a chemical cleaning strategy for PVDF membranes, and for improving the anti-aging characteristics of the PVDF in the membrane fabrication.

Morphology formation during the nonisothermal thermally‐induced phase separation (TIPS) process

AbstractIn high‐viscosity polymer solutions and blends, temperature variations during the quench process of the thermally‐induced phase separation (TIPS) influence the dynamics and thermodynamics of phase separation. Hence, this study aims to investigate the impact of temperature variations on the morphology formation during the TIPS process. First, the influence of temporal temperature variations on phase separation is investigated by coupling a transient heat conduction model and the Cahn–Hilliard equation, and the results are compared with the isothermal phase separation process. Next, the morphology formation during phase separation is inspected by applying quench from two opposite sides of the sample to the same and different temperatures through coupling the Fourier heat transfer equation and the Cahn–Hilliard equation. The influence of the enthalpy of demixing on the morphology formation and the competition between the heat and mass transfer is also evaluated. It is confirmed that temporal variations of temperature alone have a significant impact on the morphology formation during the TIPS process. In addition, quenching the system to the same and different temperatures both leads to anisotropic morphology formation, which is affected by the quench rate, quench temperature, solution viscosity, and enthalpy of demixing. Upon applying different quench temperatures from opposite sides, two different types of morphologies and droplet sizes were formed as a result of the difference in the cooling rates between the two sides. Employing the enthalpy of demixing during phase separation induced a shallow quench effect on the deep quench side due to the fact that the heat moved toward the lowest temperature in the system, which led to the formation of a distinctive structure.

Preparation of nano-porous poly(ether ether ketone) hollow fiber membrane and its performance for desalination in vacuum membrane distillation

Nano-porous poly(ether ether ketone) (PEEK) hollow fiber membranes were successfully fabricated from PEEK/polyetherimide (PEI) blends via thermally-induced phase separation (TIPS) followed by chemical extraction of PEI method. The gas permeation rates, morphologies and mechanical properties of membranes were systematically investigated under different spinning conditions. The content of PEEK in blends substantially determined the gas permeation rates following the order: PEEK30/PEI70 (~9000 GPU) > PEEK40/PEI60 (~5100 GPU) > PEEK50/PEI50 (~1700 GPU) > PEEK60/PEI40 (~300 GPU) > PEEK70/PEI30 (below 1.0 GPU). Faster winding rates and bigger N2 bore fluid flow rates would result in bigger pores, higher porosity and larger gas permeation rates, while would cause lower mechanical strength. Furthermore, the silane-grafted hydrophobic PEEK hollow fiber membranes were successfully prepared via one-step reduction followed by silane modification. The performance of virgin and modified membranes was evaluated by treating saline feed containing 3.5 wt% sodium chloride in vacuum membrane distillation (VMD) process. Compared with virgin PEEK membrane, the modified membranes exhibited a more stable flux and higher salt rejection over 99.9 % for 33 h, indicating the significant improvement in the anti-wetting property caused by silane modification. The application attempt expands the research direction of PEEK membranes and promotes its further application potential in VMD process.

Preparation and characterization of fiber braided tube reinforced polyethylene hollow fiber membranes via thermally induced phase separation

In wastewater treatment applications, mechanical strength of the membranes often cannot meet practical requirements due to the disturbance of aeration flow or the damage of high-pressure cleaning. In this work, fiber braided tube reinforced polyethylene (BR PE) hollow fiber membranes with desirable filtration performance and high tensile strength were successfully prepared via fiber braided tube reinforcement (BR) and thermally induced phase separation (TIPS) methods. Especially, the effect of heat treatment temperature on structure and properties of the membranes was discussed. The results exhibited that tensile strength and interfacial bonding state between the surface separation layer and the fiber braided tube reinforcement were improved with the increase of heat treatment temperature. While the heat treatment temperature was 130 °C, BR PE hollow fiber membranes exhibited favorable interfacial bonding state, and tensile strength was up to 204.4 MPa, which was significantly higher than that of previously reported PE membranes. Moreover, the increase of heat treatment temperature could decrease the membrane pore size and improve filtration performance. Comprehensive consideration, the optimal heat treatment temperature of BR PE hollow fiber membranes was 110 °C. This work can provide scientific and practical basis for large-scale development of BR hollow fiber membranes with good comprehensive performance.

Use of Nucleating Agent NA11 in the Preparation of Polyvinylidene Fluoride Dual-Layer Hollow Fiber Membranes.

Polyvinylidene fluoride (PVDF) dual-layer hollow fiber membranes were simultaneously fabricated by thermally induced phase separation (TIPS) and non-solvent induced phase separation (NIPS) methods using a triple orifice spinneret (TOS) for water treatment application. The support layer was prepared from a TIPS dope solution, which was composed of PVDF, gamma-butyrolactone (GBL), and N-methyl-2-pyrrolidone (NMP). The coating layer was prepared from a NIPS dope solution, which was composed of PVDF, N,N-dimethylacetamide (DMAc), and polyvinylpyrrolidone (PVP). In order to improve the mechanical strength of the dual-layer hollow fiber, a nucleating agent, sodium 2,2'-methylene bis-(4,6-di-tert-butylphenyl) phosphate (NA11), was added to the TIPS dope solution. The performance of the membrane was evaluated by surface and cross-sectional morphology, water flux, mechanical strength, and thermal property. Our results demonstrate that NA11 improved the mechanical strength of the PVDF dual-layer hollow fiber membranes by up to 42%. In addition, the thickness of the coating layer affected the porosity of the membrane and mechanical performance to have high durability in enduring harsh processing conditions.

Nature-inspired construction of poly (vinylidene fluoride) membranes through the coordination coating of tannic acid with copper ions for oil-in-water emulsions separation

Construction of the separation membranes with underwater super-oleophobic property proposes a promising pathway in the field of oily wastewater treatment, but it is still plagued with the bottlenecks of the time-consuming preparation and the unsatisfied stability of resultant membranes. Herein, the alkali induced hydroxylation and the nature-inspired construction through the coordination coating of copper ions with tannic acid (Cu2+/TA) were performed on the poly (vinylidene fluoride) (PVDF) membrane substrate prepared by the thermally induced phase separation (TIPS). The introduced hydroxyl groups resulted from the membrane hydroxylation is beneficial for the subsequent construction of the Cu2+/TA coordination coating layer. The excellent hydrophilicity and the specifically hierarchical roughness of the immobilized coating layer endow the modified membranes with the hydrophilic/underwater super-oleophobic property. The optimized membrane correspondingly showed the improved flux of around 2000 L m−2•h−1 accompanied with the oil rejection of above 97.0% in treating two simulated oil-in-water emulsions (toluene and n-hexane). Besides, the flux recovery ratio increased from 72.4% of the pristine membrane to 93.3% of the modified membrane after the BSA fouling and regeneration test, which is also indicative of the improved antifouling behavior as a result of the hydrophilic coordination coating. The membrane stability was further demonstrated by the results of the sandpaper abrasion-resisting test and the long-term (up to 6 months) air-exposure treatment. This work might provide a straightforward strategy for designing advanced membrane for the large-scale applications of oil/water separation.

Gelatin-grafted tubular asymmetric scaffolds promote ureteral regeneration via activation of the integrin/Erk signaling pathway.

Introduction: The repair of a diseased ureter is an urgent clinical issue that needs to be solved. A tissue-engineered scaffold for ureteral replacement is currently insufficient due to its incompetent bioactivity, especially in long-segment abnormalities. The primary reason is the failure of urothelialization on scaffolds. Methods: In this work, we investigated the ability of gelatin-grafted tubular scaffold in ureteral repairment and its related biological mechanism. We designed various porous asymmetric poly (L-lactic acid) (PLLA)/poly (L-lactide-co-e-caprolactone) (PLCL) tubes with a thermally induced phase separation (TIPS) method via a change in the ratio of solvents (named PP). To regulate the phenotype of urothelial cells and ureteral reconstruction, gelatin was grafted onto the tubular scaffold using ammonolysis and glutaraldehyde crosslinking (named PP-gel). The in vitro and in vivo experiments were performed to test the biological function and the mechanism of the scaffolds. Results and Discussion: The hydrophilicity of the scaffold significantly increased after gelatin grafting, which promoted the adhesion and proliferation of urothelial cells. Through subcutaneous implantation in rats, PP-gel scaffolds demonstrated good biocompatibility. The in vivo replacement showed that PP-gel could improve urothelium regeneration and maintain renal function after the ureter was replaced with an ∼4cm-long PP-gel tube using New Zealand rabbits as the experimental animals. The related biologic mechanism of ureteral reconstruction was detected in detail. The gelatin-grafted scaffold upgraded the integrin α6/β4 on the urothelial cell membrane, which phosphorylates the focal adhesion kinase (FAK) and enhances urothelialization via the MAPK/Erk signaling pathway. Conclusion: All these results confirmed that the PP46-gel scaffold is a promising candidate for the constitution of an engineered ureter and to repair long-segment ureteral defects.

Various manufacturing methods and ideal properties of scaffolds for tissue engineering applications

The precision in the design and manufacturing of scaffolds with ideal properties such as biocompatibility, biodegradability, mechanical and surface characteristics is very crucial for applications in tissue engineering. Furthermore, these techniques should be able to translate manufactured scaffolds from bench to potential applications. Numerous fabrication technologies have been employed to design ideal three-dimensional scaffolds with controlled nano-to-micro-structures to achieve the final biological response. This review highlights the ideal parameters (biological, mechanical and biodegradability) of scaffolds for different biomedical and tissue engineering applications. It discusses in detail about the various designing methods developed and used for the fabrication of scaffolds, namely solvent casting/particle leaching, freeze drying, thermal induced phase separation (TIPS), gas foaming (GF), powder foaming, sol-gel, electrospinning, stereolithography (SLA), fused deposition modelling (FDM), selective laser sintering (SLS), binder jetting technique, inkjet printing, laser-assisted bioprinting, direct cell writing and metal based additive manufacturing with a focus on their benefits, limitations and applicability in tissue engineering. • We have disserted the different manufacturing methods for the scaffolds. • We have presented the various properties of ideal scaffolds for Tissue engineering. • This review highlights the merits and demerits of various scaffolds designing methods.

Rational design of hierarchical yolk-double shell Fe@NCNs/MnO2 via thermal-induced phase separation toward wideband microwave absorption

Rational design of yolk-shell architectures with synergistic effect are vital for improving microwave attenuation ability, but still face challenges. In this work, we employ the thermal-induced phase separation engineering and redox strategy to fabricate hierarchical yolk-double shell Fe@NCNs/MnO2, in which magnetic Fe units are individually confined in N-doped carbon nanocubes (NCNs) cavity and hierarchical MnO2 nanosheets are intimately anchored on NCNs surface. It is found that the phase separation process between Prussian blue and poly-dopamine is significantly determined by the thermal-induced inward contraction owing to their different thermal stabilities and independent crystal structures. As results, the hierarchical composites exhibit matched impedance and wideband microwave absorption owing to the internal cavity architectures, multiple hetero-interfaces, dielectric-magnetic synergistic effect and hierarchical conformations. The minimum reflection loss reaches −46.7 dB with 3.3 mm thickness, and more importantly, the effective bandwidth (<-10 dB) achieves as strong as 10.8 GHz at 3.1 mm. This work opens up a novel and meaningful thinking for the construction of yolk-double shell architectures and the synthesized hierarchical composites can be used as promising candidates in addressing electromagnetic pollution.