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Round hollow fiber membranes have been well established in applications such as gas separation, ultrafiltration and blood dialysis. Yet, it is well known that geometrical topologies can introduce secondary flow patterns counteracting mass transport limitations, stemming from diffusion resistances and fouling. We present a new systematic methodology to fabricate novel membrane architectures. We use the freedom of design by 3D-printing spinnerets, having multiple bore channels of any geometry. First, such spinnerets are stationary to fabricate straight bore channels inside a monolithic membrane. Second, in an even more complex design, a new mechanical system enables rotating the spinneret. Such rotating multibore spinnerets enable (A) the preparation of twisted channels inside a porous monolithic membrane as well as (B) a helical twist of the outside geometry. The spun material systems comprise classical polymer solutions as well as metal-polymer slurries resulting in solid porous metallic monolithic membrane after thermal post-processing. It is known that twisted spiral-type bore channel geometries are potentially superior to straight channels with respect to mass and heat polarization phenomena, however their fabrication was cumbersome in the past. Now, the described methodology enables membrane fabrication to tailor the membrane geometry to the needs of the membrane process. To showcase the delicate interplay between the geometry and radial and axial flow conditions, we report fluid mechanical simulations and flow magnetic resonance imaging measurements for a twisted tri-bore membrane during permeation. [ABSTRACT FROM AUTHOR]

Novel CoFe 2 O 4 nanotubes (CFNs) are successfully prepared by the electrospinning technique and subsequent annealing process. When evaluated as anode materials for lithium-ion batteries (LIBs), the CFNs exhibited good electrochemical performance with high specific capacity of 1228 mA h g − 1 , long cycling stability over 160 cycles, and good rate capability (214.7 mA h g −1 at 2 A g −1 ). The improved electrochemical performance can be attributed to the hollow and continuous one dimensional (1D) nanostructure. [ABSTRACT FROM AUTHOR]

A family of medicated Janus fibers that provides highly tunable biphasic drug release was fabricated using a side-by-side electrospinning process employing a Teflon-coated parallel spinneret. The coated spinneret facilitated the formation of a Janus Taylor cone and in turn high quality integrated Janus structures, which could not be reliably obtained without the Teflon coating. The fibers prepared had one side consisting of polyvinylpyrrolidone (PVP) K60 and ketoprofen, and the other of ethyl cellulose (EC) and ketoprofen. To modulate and tune drug release, PVP K10 was doped into the EC side in some cases. The fibers were linear and had flat morphologies with an indent in the center. They provide biphasic drug release, with the PVP K60 side dissolving very rapidly to deliver a loading dose of the active ingredient, and the EC side resulting in sustained release of the remaining ketoprofen. The addition of PVP K10 to the EC side was able to accelerate the second stage of release; variation in the dopant amount permitted the release rate and extent this phase to be precisely tuned. These results offer the potential to rationally design systems with highly controllable drug release profiles, which can complement natural biological rhythms and deliver maximum therapeutic effects. [ABSTRACT FROM AUTHOR]

This paper reports the investigation about the usage of an epoxy (EP)-coated spinneret for the preparation of medicated electrospun nanofibers. Cellulose acetate (CA) and acetaminophen (APAP) were used as the polymeric carrier and model drug, respectively. The electrospinning was undertaken using both EP-coated spinneret and traditional stainless steel capillary as spinnerets. According to the images from scanning electron microscopy, it is obvious that the nanofibers produced using the EP-coated spinneret had a finer diameter and a narrower size distribution (450±90 nm) than nanofibers fabricated using stainless steel equivalent (660±180 nm). In vitro dissolution tests revealed that the sustained-release profiles of nanofibers from the EP-coated spinneret were superior to those of their stainless steel equivalents, although APAP existed in a similar amorphous state in both nanofibers. Because the EP-coated material can exploit the electrical forces more effectively than its steel analogue, it can enhance the electrospinning technique for producing polymeric functional nanofibers. [ABSTRACT FROM AUTHOR]

The modified near-field electrospinning (NFES) and the conventional NFES have been compared to demonstrate the viability of direct-writing micro/nano structures from PVDF solution systems. The modified NFES shows good capability in writing various orderly micro/nano patterns, such as straight and continuous lines, parallel lines, arc lines, and beads-on-string structures, whereas the conventional NFES is difficult to give a continuous writing process. Besides, the modified NFES also allows a lower electric field due to the jet initiated in a mechanical way. By finely tuning the key parameters during the modified NFES process, such as the solution property, speed of the movable collector, and the distance between the spinneret and the collector, it is likely to construct complex patterns as required on rigid or flexible substrates for a myriad of applications. [ABSTRACT FROM AUTHOR]

A new flexible nanostructure of [CoFe2O4/PVP]@[YAG:7 %Tb3+/PVP] magnetic-luminescent bifunctional coaxial nanofibers is fabricated successfully by electrospinning technology using a homemade coaxial spinneret. The morphologies, structures, and magnetic and luminescent properties of the final products are investigated by modern determination techniques. The results show that the coaxial nanofibers simultaneously provide better magnetic and luminescent properties than CoFe2O4/YAG:7%Tb3+/PVP composite nanofibers owing to the isolation of the YAG:7%Tb3+ luminescent nanofibers from the CoFe2O4 magnetic nanofibers. Furthermore, the luminescent characteristics and saturation magnetizations of the coaxial nanofibers can be tuned by adjusting the contents of luminescent and magnetic compounds. The formation mechanism of coaxial nanofibers is also presented. More importantly, the design concept and construction technology are of universal significance for the fabrication of other bifunctional coaxial nanofibers. [ABSTRACT FROM AUTHOR]

CoMn2O4nanofibers with hollow structures are successfully prepared by the electrospinning technique. These hollow nanofibers are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TG) and Brunauer-Emmett-Teller (BET) analyzer. The temperature-dependent experiments are also carried out to monitor the evolution process of CoMn2O4hollow nanofibers (HNs), and a possible formation mechanism is introduced reasonably based on the investigations. When evaluated as an electrode material for lithium-ion batteries, the results of electrochemical test show that these unique CoMn2O4HNs exhibit admirable lithium storage performances with high specific capacity and excellent rate capability. The hollow and continuous one dimensional (1D) nanostructures of the CoMn2O4HNs make a prominent contribution to the excellent electrochemical performance. [ABSTRACT FROM AUTHOR]

Abstract: We have developed novel tri-bore thin-film composite (TFC) hollow fiber (HF) membranes for forward osmosis (FO) processes by employing a specially designed tri-bore blossom spinneret. The resultant hollow fibers exhibit evenly-distributed three inner bores with an either round or triangle outer geometry. The newly developed triangle tri-bore hollow fibers have impressive mechanical strength with enhanced permeation properties better than the round ones. Further efforts were given to investigate the effects of glycerol treatment and surfactant concentration during the interfacial polymerization. The new developed TFC tri-bore HF membranes exhibit high water fluxes of 50.5LMH and 11.8LMH with salt leakages as low as 3.5gMH and 2.5gMH, in pressure retarded osmosis (PRO) and FO modes, respectively, when using 2M NaCl as the draw solution and pure water as the feed. The potential of using the triangle TFC membrane for desalination is also investigated. It could reach a water flux of 5.8LMH using a 2M NaCl draw solution and a model seawater solution as the feed. In addition, much more fibers can be packed in a FO module if TFC tri-bore HF membranes have a triangle shape instead of a round one. Theoretical calculations suggest that water output of the module consisting of triangle membranes would double the one comprising round membranes at a 40% packing density. This may enlighten the advantages of triangle tri-bore configuration for FO applications. [Copyright &y& Elsevier]