Electrospun preparation of polylactic acid nanoporous fiber membranes via thermal-nonsolvent induced phase separation

Influence of surface topography on PCL electrospun scaffolds for liver tissue engineering

Severe liver disease is one of the most common causes of death globally. Currently, whole organ transplantation is the only therapeutic method for end-stage liver disease treatment, however, the need for donor organs far outweighs demand. Recently liver tissue engineering is starting to show promise for alleviating part of this problem. Electrospinning is a well-known method to fabricate a nanofibre scaffold which mimics the natural extracellular matrix that can support cell growth. This study aims to investigate liver cell responses to topographical features on electrospun fibres. Scaffolds with large surface depression (2 μm) (LSD), small surface depression (0.37 μm) (SSD), and no surface depression (NSD) were fabricated by using a solvent-nonsolvent system. A liver cell line (HepG2) was seeded onto the scaffolds for up to 14 days. The SSD group exhibited higher levels of cell viability and DNA content compared to the other groups. Additionally, the scaffolds promoted gene expression of albumin, with all cases having similar levels, while the cell growth rate was altered. Furthermore, the scaffold with depressions showed 0.8 MPa higher ultimate tensile strength compared to the other groups. These results suggest that small depressions might be preferred by HepG2 cells over smooth and large depression fibres and highlight the potential for tailoring liver cell responses.

Critical review on microfibrous composites for applications in chemical engineering

Microfibrous composites (MCs) are novel materials with unique structures and excellent functional properties, showing great potential in industrial applications. The investigation of the physicochemical properties of MCs is significant for accommodating the rapid development of high-efficiency chemical engineering industries. In this review, the characteristics, synthesis and applications of different types of previously reported MCs are discussed according to the constituent fibres, including polymers, metals and nonmetals. Among the different types of MCs, polymer MCs have a facile synthesis process and adjustable fibre composition, making them suitable for many complex situations. The high thermal and electrical conductivity of metal MCs enables their application in strong exothermic, endothermic and electrochemical reactions. Nonmetallic MCs are usually stable and corrosion resistant when reducing and oxidizing environments. The disadvantages of MCs, such as complicated synthesis processes compared to those of particles or powders, high cost, insufficient thorough study, and unsatisfactory regeneration effects, are also summarized. As a result, a more systematic investigation of MCs remains necessary. Despite the advantages and great application potential of microfibrous composites, much effort remains necessary to advance them to the industrial level in the chemical engineering industry.

Recent development of pressure retarded osmosis membranes for water and energy sustainability: A critical review

With the goal of zero-liquid discharge and green energy harvest, extraction of abundant green energy from saline water via pressure retarded osmosis (PRO) technology is a promising but challenging issue for water treatment technologies to achieve water and energy sustainability. Development of high performance PRO membranes has received increased concerns yet still under controversy in practical applications. In this review, a comprehensive and up-to-date discussion of some key historical developments is first introduced covering the major advances of PRO engineering applications and novel membranes especially made in recent years. Then the critical performance indicators of PRO membranes including water flux and power density are briefly discussed. Subsequently, sufficient discussion on four performance limiting factors in PRO membrane and process is presented including concentration polarization, reverse solute diffusion, membrane fouling and mechanical stability. To fully address these issues, an updated insight is provided into recent major progresses on advanced fabrication and modification techniques of novel PRO membranes featuring enhanced performance with different configurations and materials, which are also reviewed in detail based on the viewpoint of design rationales. Afterwards, antifouling strategies and engineering applications are critically introduced. Finally, conclusions and future perspective of PRO membrane for practical operation are briefly discussed.

Advances in Functional Polymer Nanofibers: From Spinning Fabrication Techniques to Recent Biomedical Applications

Functional polymeric micro-/nanofibers have emerged as promising materials for the construction of structures potentially useful in biomedical fields. Among all kinds of technologies to produce polymer fibers, spinning methods have gained considerable attention. Herein, we provide a recent review on advances in the design of micro- and nanofibrous platforms via spinning techniques for biomedical applications. Specifically, we emphasize electrospinning, solution blow spinning, centrifugal spinning, and microfluidic spinning approaches. We first introduce the fundamentals of these spinning methods and then highlight the potential biomedical applications of such micro- and nanostructured fibers for drug delivery, tissue engineering, regenerative medicine, disease modeling, and sensing/biosensing. Finally, we outline the current challenges and future perspectives of spinning techniques for the practical applications of polymer fibers in the biomedical field.

Enhanced Aerosol Particle Filtration Efficiency of Nonwoven Porous Cellulose Triacetate Nanofiber Mats

Aerosol particle filtration in most penetrating particle size (MPPS) region is of great challenge for conventional nonwoven filter mats. The present work, therefore, redesigns conventional filter mats by introducing porous structure. A combination of thermally induced phase separation and breath figure mechanism was employed to synthesize porous cellulose triacetate fibers, in conjunction with the volatile solvent methylene chloride. The ambient humidity, the concentration of the polyvinylpyrrolidone (PVP) secondary polymer, and the ethanol cosolvent were all adjusted to modify the Taylor cone formation, jet stability, and fiber porosity. After fiber formation, the PVP was removed to obtain a superhydrophobic material. To distinguish the effect of pores, the performance of porous and nonporous nanofibers having similar sizes was conducted. Tests were performed using various dust particle sizes, and the results show that the collection efficiency of the porous fibers, resulting from particle diffusion, inertial impaction, and interception, was improved. Interestingly, the efficiency of the porous fibers in the MPPS region was exceptionally enhanced (up to 95%), demonstrating that the presence of dynamic pores greatly contributes to particle capture.

Zeolitic Imidazole Framework/Graphene Oxide Hybrid Functionalized Poly(lactic acid) Electrospun Membranes: A Promising Environmentally Friendly Water Treatment Material

Poly(lactic acid) (PLA) electrospun membranes immobilized with Zeolitic imidazole framework/graphene oxide hybrid (ZIF-8@GO) are fabricated via electrospinning. At first, ZIF-8@GO is synthesized by the in situ growth method. The UV-visible light (UV-vis) result demonstrates that ZIF-8@GO has a narrower band gap than ZIF-8. The performance of the obtained composite membrane is investigated by scanning electron microscope, Fourier transform IR spectroscopy, tensile test, water contact angle, and methylene blue (MB) removal test. The results demonstrate that the degradable PLA/ZIF-8@GO electrospun membrane shows enhanced tensile strength than neat PLA. The composite membrane also shows great MB removal ability by adsorption and photocatalytic degradation. The MB removal efficiency could reach over 90% at very low ZIF-8@GO concentration (0.06 mg/mL).

A review on organic–inorganic hybrid nanocomposite membranes: a versatile tool to overcome the barriers of forward osmosis

Forward osmosis (FO) processes have recently attracted increasing attention and show great potential as a low-energy separation technology for water regeneration and seawater desalination. However, a number of challenges, such as internal concentration polarization, membrane fouling, and the trade-off effect, limit the scaleup and industrial practicality of FO. Hence, a versatile method is needed to address these problems and fabricate ideal FO membranes. Among the many methods, incorporating polymeric FO membranes with inorganic nanomaterials is widely used and effective and is reviewed in this paper. The properties of FO membranes can be improved and meet the demands of various applications with the incorporation of nanomaterials. This review presents the actualities and advantages of organic–inorganic hybrid nanocomposite FO membranes. Nanomaterials applied in the FO field, such as carbon nanotubes, graphene oxide, halloysite nanotubes, silica and Ag nanoparticles, are classified and compared in this review. The effects of modification methods on the performance of nanocomposite FO membranes, including blending, in situ interfacial polymerization, surface grafting and layer-by-layer assembly, are also reviewed. The outlook section discusses the prospects of organic–inorganic hybrid nanocomposite FO membranes and advanced nanotechnologies available for FO processes. This discussion may provide new opportunities for developing novel FO membranes with high performance.

Nanocomposite forward osmosis (FO) membranes have attracted increasing attentions recently and showed great comprehensive performance. Various modification methods have been employed to incorporate inorganic nanomaterials to FO membranes.

Electrospun porous PLLA and poly(LLA-co-CL) fibers by phase separation

Porous poly(LLA-co-CL) fibers were electrospun and the porosity of the fibers could be controlled by using good/poor binary solvents.

Tailored fabrication of TiO2@carbon nanofibers composites via foaming agent migration

Based on the merits and demerits of conventional methods for fabricating TiO₂@carbon nanofibers (TiO₂@CNFs) composites, the composites were prepared via a foaming-assisted electrospinning strategy and subsequent thermal treatment.