Preparation of Sodium-Activated Natural Bentonite Clay Incorporated Cellulose Acetate Nanofibres by Free Surface Electrospinning and Its Proposed Applications

Incorporating activated bentonite clay (BC) into electrospun nanofibres is an established strategy for modulating adsorption behaviour. In the present study, we have provided a comprehensive review of electrospun nanofibres from different types of polymers with synthesized montmorillonite clays (MMT). Loading activated natural bentonite clay (BC) into any type of polymer can improve the adsorption property of electrospun nanofibres, but BC must be well dispersed, suspended and loaded to achieve any benefit. Naturally occurring calcium BC was completely activated to sodium BC with a 4 wt.% sodium carbonate (Na2CO3)/BC ratio. High throughput composite nanofibrous fabrics were produced from cellulose acetate (CA)/BC spinning solutions using free surface electrospinning and the effect of BC loadings on viscosity, surface tension and electrical conductivity prior to spinning were studied. It has been found that the higher the BC loading rate and thus higher viscosity and surface tension, the higher the applied voltage and the lower the rotation speed of the wires electrode were required in order to get the highest productivity accompanied with electrospinning stability. Chemical and thermal analyses were conducted on as-spun fibres, and SEM and TEM revealed a nanofibrous morphology consisting of an inter-penetrating network of fibres and semi-spherical features resembling jellyfish with an internal core of BC. The problem with the existing adsorption process and the need for the change in the texture of the separation layer that controls the performance of the resultant membrane in terms of flux and selectivity were discussed and directed. We believe that this study may pave the way for further use of electrospun nanofibres loaded with clay in a wide variety of environmental and medical applications

Double-Walled Carbon Nanotubes Ink for High-Conductivity Flexible Electrodes

Carbon electronics is a growing field that spans printable electronics, energy storage devices, and bio-sensors. The commercialization of these carbon-based technologies requires a scalable production of high conductivity, acid-free carbon nanotube ink dispersions. Super acids have been used to achieve high concentration CNT inks however a scalable acid-free process to achieve similar concentrations has been missing for a long time. In this work, we demonstrate that water and sodium-cellulose are sufficient for achieving a scalable production of highly conductive CNT based ink, provided the solution is processed through a very high shear microfluidizer. Materials used in this process are acid-free and require no post-processing, such as centrifuging or heating. We have achieved conductivity and sheet resistance of 3.6±0.2x105 S.m-1 and 0.11 Ω.□-1mil-1 respectively, which are among the best-reported values for any un-doped carbon-based film. The thermal conductivity of the free-standing carbon films is 43±4 W m-1K-1. Using this method uniformly dispersed CNT inks, of viscosity >1Pa-s, are produced. Once printed on paper, these CNT films show pronounced resilience to mechanical deformation. This simple but scalable process provides a viable technology for using carbon-based conducting inks for printing large-scale devices.Lloyds Register Foundatio

A UV-cured nanofibrous membrane of vinylbenzylated gelatin-poly(ɛ-caprolactone) dimethacrylate co-network by scalable free surface electrospinning

Electrospun nanofibrous membranes of natural polymers, such as gelatin, are fundamental in the design of regenerative devices. Crosslinking of electrospun fibres from gelatin is required to prevent dissolution in water, to retain the original nanofibre morphology after immersion in water, and to improve the thermal and mechanical properties, although this is still challenging to accomplish in a controlled fashion. In this study, we have investigated the scalable manufacture and structural stability in aqueous environment of a UV-cured nanofibrous membrane fabricated by free surface electrospinning (FSES) of aqueous solutions containing vinylbenzylated gelatin and poly(ɛ-caprolactone) dimethacrylate (PCL-DMA). Vinylbenzylated gelatin was obtained via chemical functionalisation with photopolymerisable 4-vinylbenzyl chloride (4VBC) groups, so that the gelatin and PCL phase in electrospun fibres were integrated in a covalent UV-cured co-network at the molecular scale, rather than being simply physically mixed. Aqueous solutions of acetic acid (90 vol%) were employed at room temperature to dissolve gelatin-4VBC (G-4VBC) and PCL-DMA with two molar ratios between 4VBC and DMA functions, whilst viscosity, surface tension and electrical conductivity of resulting electrospinning solutions were characterised. Following successful FSES, electrospun nanofibrous samples were UV-cured using Irgacure I2959 as radical photo-initiator and 1-Heptanol as water-immiscible photo-initiator carrier, resulting in the formation of a water-insoluble, gelatin/PCL covalent co-network. Scanning electron microscopy (SEM), attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, differential scanning calorimetry (DSC), tensile test, as well as liquid contact angle and swelling measurements were carried out to explore the surface morphology, chemical composition, thermal and mechanical properties, wettability and water holding capacity of the nanofibrous membranes, respectively. UV-cured nanofibrous membranes did not dissolve in water and showed enhanced thermal and mechanical properties, with respect to as-spun samples, indicating the effectiveness of the photo-crosslinking reaction. In addition, UV-cured gelatin/PCL membranes displayed increased structural stability in water with respect to PCL-free samples and were highly tolerated by G292 osteosarcoma cells. These results therefore support the use of PCL-DMA as hydrophobic, biodegradable crosslinker and provide new insight on the scalable design of water-insoluble, mechanical-competent gelatin membranes for healthcare applications

Double-Walled Carbon Nanotubes Ink for High-Conductivity Flexible Electrodes

Carbon electronics is a growing field that spans printable electronics, energy storage devices, and biosensors. The commercialization of these carbon-based technologies requires a scalable production of high-conductivity, acid-free carbon nanotube ink dispersions. Superacids have been used to achieve high-concentration CNT inks; however, a scalable acid-free process to achieve similar concentrations has been missing for a long time. In this work, we demonstrate that water and sodium cellulose are sufficient for achieving a scalable production of highly conductive CNT-based ink, provided the solution is processed through a very high-shear microfluidizer. Materials used in this process are acid-free and require no postprocessing, such as centrifuging or heating. We have achieved conductivity and sheet resistance of (3.6 ± 0.2) × 105 S m-1 and 0.11 ω -1 mil-1, respectively, which are among the best reported values for any undoped carbon-based film. The thermal conductivity of the free-standing carbon films is 43 ± 4 W m-1 K-1. By use of this method, uniformly dispersed CNT inks of viscosity >1 Pa·s are produced. Once printed on paper, these CNT films show pronounced resilience to mechanical deformation. This simple but scalable process provides a viable technology for using carbon-based conducting inks for printing large-scale devices

Dry‐jet wet electrospinning of native cellulose microfibers with macroporous structures from ionic liquids

In this study, we have provided a review of electrospun cellulose micro/nanofibers from ionic liquids (ILs) and cosolvents from which we identify a lack of previous studies focusing on the structural morphology of the dry‐jet wet electrospun native cellulose fibers from ILs. We have therefore aimed to investigate factors influencing the structural morphology of cellulose/IL electrospun fibers and investigate the coagulation parameters on this morphology. The electrospinning of 10% w/v cellulose/([C2MIM][OAc]/MIM) (1/1, v/v) solution was shown to produce macroporous fibers with average diameters of 2.8 ± 1.4 μm with pore sizes from 100 to 200 nm. We have found that coagulation bath type and immersion time affect the morphological structure of the electrospun fibers. The fiber spinnability, formation, and morphological structure are mainly dependent on the method used to collect and coagulate/solidify the fibers. The physical properties of the dissolved cellulose were measured and these are discussed in terms of the solution spinnability. The structural morphology of the electrospun cellulose fibers was characterized by scanning electron microscopy, and finally the extraction of IL from the fiber body was confirmed by nuclear magnetic resonance. The electrospun cellulose fibers morphology shows the formation of both micron and nanometer sized fibers with different morphological “macroporous” structures

Fabrication of High Specific Electrical Conductivity and High Ampacity Carbon Nanotube/Copper Composite Wires

Carbon nanotubes and copper composites have long been predicted as new conductors that may benefit from the high conductivity of copper and the lightweight and very high ampacity of carbon nanotubes. One of the key challenges has been to integrate Cu with CNTs and form a free-standing composite wire. We have achieved this by first making a CNTs filament using high concentration (20 g L-1) CNTs dispersion, an acid-free wet spinning process and then by replacing the polymer with copper using heat based polymer decomposition and periodic pulse reverse electroplating. It has been demonstrated that indeed the specific conductivity and the current-carrying capability (or ampacity) are increased manifold. MWCNTs/Cu composite wires developed in this paper have electrical conductivity σ ~ 5.5 ×105 S cm-1. These MWCNTs/Cu wires are 2/3rd the weight of bulk Cu wires. Their specific electrical conductivity is σρ~ 9.38 ×104 S cm2 g-1 which is 45 % higher than International Annealed Copper Standard (IACS) Cu. These composite wires have an ampacity of A~ 20 ×105 A cm-2 and 4×105 A cm-2 for 1.5 mm and 17 mm gauge length wires respectively, which is 4 to 6 times higher than pure Cu depending on the wire lengths. MWCNTs volume percentage in the MWCNTs/Cu wire is about 40%.Lloyds Register Foundatio

Fabrication of High Specific Electrical Conductivity and High Ampacity Carbon Nanotube/Copper Composite Wires

A challenge is to integrate Cu with carbon nanotubes (CNTs) and form a free-standing composite wire. This is achieved by first making a CNT filament using high concentration (20 g L−1) CNT dispersion, an acid-free wet spinning process and then by replacing the polymer with copper using heat based polymer decomposition and periodic pulse reverse electroplating. It is demonstrated that indeed the specific conductivity and the current-carrying capability (or ampacity) are increased manifold. The multiwalled CNT (MWCNT)/Cu composite wires developed in this paper have electrical conductivity σ ≈ 5.5 × 10 5 S cm−1. These MWCNT/Cu wires are 2/3rd the weight of bulk Cu wires. Their specific electrical conductivity is σρ ≈ 9.38 ×10 4 S cm2g−1 which is 45% higher than International Annealed Copper Standard Cu. These composite wires have an ampacity of A ≈ 20 × 105 and 4 × 105 A cm−2 for 1.5 and 17 mm gauge length wires, respectively, which is four to six times higher than pure Cu depending on the wire lengths. MWCNTs volume percentage in the MWCNT/Cu wire is about 40%