Combined Electrospinning-Electrospraying for High-Performance Bipolar Membranes with Incorporated MCM-41 as Water Dissociation Catalysts.

Electrospinning has been demonstrated as a very promising method to create bipolar membranes (BPMs), especially as it allows three-dimensional (3D) junctions of entangled anion exchange and cation exchange nanofibers. These newly developed BPMs are relevant to demanding applications, including acid and base production, fuel cells, flow batteries, ammonia removal, concentration of carbon dioxide, and hydrogen generation. However, these applications require the introduction of catalysts into the BPM to allow accelerated water dissociation, and this remains a challenge. Here, we demonstrate a versatile strategy to produce very efficient BPMs through a combined electrospinning-electrospraying approach. Moreover, this work applies the newly investigated water dissociation catalyst of nanostructured silica MCM-41. Several BPMs were produced by electrospraying MCM-41 nanoparticles into the layers directly adjacent to the main BPM 3D junction. BPMs with various loadings of MCM-41 nanoparticles and BPMs with different catalyst positions relative to the junction were investigated. The membranes were carefully characterized for their structure and performance. Interestingly, the water dissociation performance of BPMs showed a clear optimal MCM-41 loading where the performance outpaced that of a commercial BPM, recording a transmembrane voltage of approximately 1.11 V at 1000 A/m2. Such an excellent performance is very relevant to fuel cell and flow battery applications, but our results also shed light on the exact function of the catalyst in this mode of operation. Overall, we demonstrate clearly that introducing a novel BPM architecture through a novel hybrid electrospinning-electrospraying method allows the uptake of promising new catalysts (i.e., MCM-41) and the production of very relevant BPMs.

PCL-based 3D nanofibrous structure with well-designed morphology and enhanced specific surface area for tissue engineering application.

Tissue engineering opens a new horizon for biological tissue replacement applications. Scaffolds, appropriate cells, and signaling induction are the main three determinant parameters in any tissue engineering applications. Designing a suitable scaffold which can mimic the cellular inherent and natural habitation is of great importance for cellular growth and proliferation. Just like a natural extracellular matrix (ECM), scaffolds provide the cells with an environment for performing biological functions. Accordingly, vast surface area and three-dimensional nanofibrous structures are among the pivotal characteristics of functional scaffolds in tissue engineering, and enhancement of their properties is the main purpose of the present research. In our previous study, a patterned structure composed of continuous nanofibers and microparticles was introduced. In this work, a new modification is applied for adjustment of the surface area of an electrospun/electrosprayed scaffold. For this purpose, at predetermined stages during electrospinning/electrospraying, the nitrogen gas is flushed through the mesh holes of the collector in the opposite direction of the jet movement. This method has led to the formation of very thin nanofibrous layers at nitrogen flush intervals by providing a cooling effect of the sweeping nitrogen. As a consequence, a straticulated structure has been fabricated which possesses extremely high surface/volume ratio. The porosity, water absorption, and morphological analysis were conducted on the obtained scaffold. In vitro cytocompatibility assessments as well as histological analysis demonstrated that the fabricated scaffold provides a proper substrate for cellular attachment, proliferation and infiltration. These findings can be advantageous in three-dimensional tissue engineering such as bone tissue engineering applications. Furthermore, according to the advanced microstructure and vast surface area of the fabricated samples, they can be applied in many other applications, such as membrane, filtration, etc.

Superhydrophobic Polyurethane Membrane with a Biomimetically Hierarchical Structure for Self-Cleaning.

In this study, a stable and durable hexadecyltrimethoxysilane (HDTMS)/thermoplastic polyurethane (TPU) superhydrophobic film is successfully prepared by a simple and low-cost two-step method, namely, carrying out biomimetically hierarchical structures and low surface energy material modification concurrently. Meanwhile, effective parameters affecting the water contact angle (WCA) are studied and optimized. More importantly, under optimum parameters, the maximum WCA is 165°, the minimum slide angle (SA) is 3°, and the adhesion force is 13 µN, showing good self-cleaning performance. Besides, considerable mechanical stability to withstand 4000 tension or 5000 compression cycles, breathability, and moisture penetrability, as well as chemical resistance with sustained superhydrophobic properties in various harsh environments, are presented.

Bioinspired superwetting fibrous skin with hierarchical roughness for efficient oily water separation.

Developing superwetting membranes with interconnected pore and multi-scale roughness for efficient oily water separation is significant but challenging owing to the limitations of low water flux and membrane fouling. Herein, we report a scalable method to develop superwetting membranes with superhydrophilicity and underwater superoleophobicity for oily water separation. This novel approach, composed of electrospinning/electrospraying of polyacrylonitrile (PAN), was to fabricate rough sphere membrane substrate, followed by in-situ polymerization of dopamine/polyethyleneimine (DA/PEI) to positively charge the fiber skin and then subsequent immersed into the negatively charged Ludox solution to construct rough membrane surface via electrostatic attraction. Benefiting from the rough sphere surface of the fibrous skin layer, the resultant membrane displayed micro/nanostructured surfaces with intriguing in-air superhydrophilicity of 0° and underwater superoleophobicity of 166° as well as robust oil-proof pressure of 83.55 kPa. As a proof-of-concept, the resultant membrane achieved high water flux and oil rejection efficiency as well as fantastic durability and antifouling performance toward the separation of highly emulsified oily water. The integration of electrospinning/electrospraying with bioinspired method is also expected to fabricate superwetting sphere surface membrane with interconnected pores for other selective separation applications.

Influence of PLLA/PCL/HA Scaffold Fiber Orientation on Mechanical Properties and Osteoblast Behavior.

Scaffolds based on aligned and non-aligned poly (L-lactic acid) (PLLA)/polycaprolactone (PCL) fibers obtained by electrospinning, associated to electrosprayed hydroxyapatite (HA) for tissue engineering applications were developed and their performance was compared in terms of their morphology and biological and mechanical behaviors. The morphological results assessed by scanning electron microscopy showed a mesh of PLLA/PCL fibers (random and perfectly aligned) associated with aggregates of nanophased HA. Fourier transform infrared spectrometry confirmed the homogeneity in the blends and the presence of nanoHA in the scaffold. As a result of fiber alignment a 15-fold increase in Young's Modulus and an 8-fold increase in tensile strength were observed when compared to non-aligned fibers. In PLLA/PCL/HA scaffolds, the introduction of nanoHA caused a remarkable improvement of the mechanical strength of this material acting as a reinforcement, enhancing the response of these constructs to tensile stress. In vitro testing was evaluated using osteoblast (MC3T3-E1) cells. The results showed that both fibrous scaffolds were able to support osteoblast cell adhesion and proliferation and that fiber alignment induced increased cellular metabolic activity. In addition, the adhesion and proliferation of Staphylococcus aureus were evaluated and a lower number of colony forming units (CFUs) was obtained in the scaffolds with aligned fibers.

Flexible/Rechargeable Zn-Air Batteries Based on Multifunctional Heteronanomat Architecture.

The increasing demand for advanced rechargeable batteries spurs development of new power sources beyond currently most widespread lithium-ion batteries. Here, we demonstrate a new class of flexible/rechargeable zinc (Zn)-air batteries based on multifunctional heteronanomat architecture as a scalable/versatile strategy to address this issue. In contrast to conventional electrodes that are mostly prepared by slurry-casting techniques, heteronanomat (denoted as "HM") framework-supported electrodes are fabricated through one-pot concurrent electrospraying (for electrode powders/single-walled carbon nanotubes (SWCNTs)) and electrospinning (for polyetherimide (PEI) nanofibers) process. Zn powders (in anodes) and rambutan-shaped cobalt oxide (Co3O4)/multiwalled carbon nanotube (MWCNT) composite powders (in cathodes) are used as electrode active materials for proof of concept. The Zn (or Co3O4/MWCNT) powders are densely packed and spatially bound by the all-fibrous HM frameworks that consist of PEI nanofibers (for structural stability)/SWCNTs (for electrical conduction) networks, leading to the formation of three-dimensional bicontinuous ion/electron transport channels in the electrodes. The HM electrodes are assembled with cross-linked polyvinyl alcohol/polyvinyl acrylic acid gel polymer electrolytes (acting as zincate ion crossover-suppressing, permselective separator membranes). Benefiting from its unique structure and chemical functionalities, the HM-structured Zn-air cell significantly improves mechanical flexibility and electrochemical rechargeability, which are difficult to achieve with conventional Zn-air battery technologies.

Hybrid scaffolds of Mg alloy mesh reinforced polymer/extracellular matrix composite for critical-sized calvarial defect reconstruction.

The challenge of developing scaffolds to reconstruct critical-sized calvarial defects without the addition of high levels of exogenous growth factor remains relevant. Both osteogenic regenerative efficacy and suitable mechanical properties for the temporary scaffold system are of importance. In this study, a Mg alloy mesh reinforced polymer/demineralized bone matrix (DBM) hybrid scaffold was designed where the hybrid scaffold was fabricated by a concurrent electrospinning/electrospraying of poly(lactic-co-glycolic acid) (PLGA) polymer and DBM suspended in hyaluronic acid (HA). The Mg alloy mesh significantly increased the flexural strength and modulus of PLGA/DBM hybrid scaffold. In vitro results demonstrated that the Mg alloy mesh reinforced PLGA/DBM hybrid scaffold (Mg-PLGA@HA&DBM) exhibited a stronger ability to promote the proliferation of bone marrow stem cells (BMSCs) and induce BMSC osteogenic differentiation compared with control scaffolding materials lacking critical components. In vivo osteogenesis studies were performed in a rat critical-sized calvarial defect model and incorporated a variety of histological stains and immunohistochemical staining of osteocalcin. At 12 weeks, the rat model data showed that the degree of bone repair for the Mg-PLGA@HA&DBM scaffold was significantly greater than for those scaffolds lacking one or more of the principal components. Although complete defect filling was not achieved, the improved mechanical properties, promotion of BMSC proliferation and induction of BMSC osteogenic differentiation, and improved promotion of bone repair in the rat critical-sized calvarial defect model make Mg alloy mesh reinforced PLGA/DBM hybrid scaffold an attractive option for the repair of critical-sized bone defects where the addition of exogenous isolated growth factors is not employed.

Advancements and Challenges in Multidomain Multicargo Delivery Vehicles.

Reparative and regenerative processes are well-orchestrated temporal and spatial events that are governed by multiple cells, molecules, signaling pathways, and interactions thereof. Yet again, currently available implantable devices fail largely to recapitulate nature's complexity and sophistication in this regard. Herein, success stories and challenges in the field of layer-by-layer, composite, self-assembly, and core-shell technologies are discussed for the development of multidomain/multicargo delivery vehicles.