Nanofiber Devices Research Articles

Electrospun Polymeric Nanofibers for Malaria Control: Advances in Slow‐Release Mosquito Repellent Technology

AbstractThe textile industry comprises technologies that transform synthetic or natural fibers into yarn, cloth, and felt for manufacturing clothing, upholstery, and household linens. The major public health threat in tropical and subtropical countries is mosquito‐borne malaria. Nowadays, the demand for insect repellent‐based textiles is continuously rising, as they are used for protection against diseases transmitted by mosquitoes. The present work reviews studies on the fabrication of insect repellent containing electrospun polymeric nanofibers as principal tools for protecting people against mosquito bites. Electrospinning technology is a remarkably facile technique for fabricating polymeric nanofiber devices. The technique is outlined and elucidated. The performance of insect repellent‐based polymeric nanofibers against mosquitoes is carefully reported and comprehensively reviewed in‐depth. Furthermore, the progress made on the mathematical modeling of the release rate of repellents through polymeric nanofiber devices is reviewed. The reviewed studies demonstrate that repellents can be released slowly from electrospun nanofibers, increasing the product's protection period against insects. The reviewed works suggest that electrospinning technology has led to an effective and facile methodology for fabricating functional nanofiber textiles with insect repellent. The reviewed studies showed that product‐based repellents can be effective not only against malaria but also against other mosquito‐borne diseases.

Economic optimization of antibody capture through Protein A affinity nanofiber chromatography

In this study we compare a nanofiber device and a resin column, both with the same Protein A ligand, for the capture of four different monoclonal antibodies and a trivalent crystallizable fragments (Fc) of antibody. We show that the dynamic binding capacity of the nanofiber device varies slightly with residence time, with the transfer kinetics slower for the IgG1, than for the IgG4 antibody. Surface plasmon resonance shows that the trivalent Fc binds to multiple Protein A ligand sites due to its three repeating Fc units, whereas multiple IgG antibodies bind to a single Protein A ligand. The nanofiber device gives comparable eluate purity to the resin column but at lower antibody concentrations due to its larger housing volume and lower binding capacity. It can be used for up to 200 cycles without performance loss and gives consistent eluate quality when scaled from 0.4 mL to 3.75 mL. We show that the use of a single nanofiber device to process one 2000 L clarified harvest through multiple cycles can reduce the Cost of Goods fivefold compared with a resin column. Costs are potentially lower for up to thirteen 2000 L harvests if device reuse can be validated. Nanofiber devices are thus an attractive option for manufacture of pre-clinical or clinical trial material where the number of batches is limited.

Enhancement in the Detection Ability of Metal Oxide Sensors Using Defect-Rich Polycrystalline Nanofiber Devices.

The development of SnO2 and TiO2 polycrystalline nanofiber devices (PNFDs) has been widely researched as a method of protecting humans from household air pollution. PNFDs have three significant advantages. The nanofibers before the annealing process are polymer‐rich materials, which can be used as particulate material (PM) filters. The multiporous nanofibers fabricated by the annealing process have numerous defects that can serve as generation‐recombination centers for electron–hole pairs, enabling the PNFDs to serve as multiple‐wavelength light (from 365 to 940 nm) detectors. Lastly, the numerous surface/interface defects can drastically enhance the toxic gas detection ability. The toxic gas detection range of PNFDs for CO(g) and NO(g) is from 400 to 50 ppm and 400 to 50 ppb, respectively. Quick response times and recovery properties are key parameters for commercial applications. The recovery time of NO(g) detection can be improved from 1 ks to 40 s and the PNFD operating temperature lowered to 50 °C. These results indicate that SnO2 and TiO2 PNFDs have good potential for commercialization and use as toxic gas and photon sensors in daily lives.

Development of drug assessment in central and peripheral neuronal networks using oriented nanofiber devices．

Development of drug assessment in central and peripheral neuronal networks using oriented nanofiber devices．

Thermal Stability of Epitaxial Graphene Electrodes for Conductive Polymer Nanofiber Devices

We used large area, monolayer graphene epitaxially grown on SiC (0001) as contact electrodes for polymer nanofiber devices. Our fabrication process, which avoids polymer resist residues on the graphene surface, results in graphene-polyaniline nanofiber devices with Ohmic contacts and electrical conductivity comparable to that of Au-nanofiber devices. We further checked the thermal stability of the graphene contacts to polyaniline devices by annealing up to T = 800 °C, the temperature at which polyaniline nanofibers are carbonized but the graphene electrode remains intact. The thermal stability and Ohmic contact of polymer nanofibers are demonstrated here, which together with the chemical stability and atomic flatness of graphene, make epitaxial graphene on SiC an attractive contact material for future all-carbon electronic devices.

Poly(3,4-ethylenedioxythiophene)-Based Nanofiber Mats as an Organic Bioelectronic Platform for Programming Multiple Capture/Release Cycles of Circulating Tumor Cells.

In this investigation, we employed a novel one-step electrospinning process to fabricate poly(ethylene oxide) (PEO)/poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) core/shell nanofiber structures with improved water resistance and good electrochemical properties and characterized them using scanning electron microscopy, transmission electron microscopy, and time-of-flight secondary ion mass spectrometry imaging. We then integrated a biotinylated poly-(l-lysine-graft-ethylene glycol) (PLL-g-PEG-biotin) coating with three-dimensional (3D) PEDOT-based nanofiber devices for dynamic control over the capture/release performance of rare circulating tumor cells (CTCs) on-chip. The detailed capture/release behavior of the circulating tumor cells was studied using an organic bioelectronic platform comprising PEO/PEDOT:PSS nanofiber mats with 3 wt % (3-glycidyloxypropyl)trimethoxysilane as an additive. We have demonstrated that these nanofiber mats deposited on five-patterned indium tin oxide finger electrodes are excellent candidates for use as functional bioelectronic interfaces for the isolation, detection, sequential collection, and enrichment of rare CTCs through electrical activation of each single electrode. This combination behaved as an ideal model system displaying a high cell-capture yield for antibody-positive cells while resisting the adhesion of antibody-negative cells. Taking advantage of the electrochemical doping/dedoping characteristics of PEDOT:PSS materials, the captured rare cells could be electrically triggered release through the desorption phenomena of PLL-g-PEG-biotin on device surface. More than 90% of the targeted cancer cells were captured on the 3D PEDOT-based nanofiber microfluidic device; over 87% of captured cancer cells were subsequently released for collection; approximately 80% of spiked cancer cells could be collected in a 96-well plate. Therefore, this 3D PEDOT-based nanofiber approach appears to be an economical route for the large-scale preparation of systems for enhancing the downstream characterization of rare CTCs.

Synergistic tungsten oxide/organic framework hybrid nanofibers for electrochromic device application

We report the first successful applications of tungsten oxide/conducting polymer hybrid nanofiber assemblies in electrochromic devices. Poly(3,4-ethylenedioxythiophene)/tungsten oxide (PEDOT/WO3) and polypyrrole/tungsten oxide (PPy/WO3) composites were prepared by an in situ chemical oxidative polymerization of monomers in different ionic liquids; 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4), 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide (BMIMTFSI) and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl) imide (BMPTFSI). Electrospinning process was used to form hybrid nanofibers from chemically synthesized nanostructures. The electrospun hybrid samples were compared from both morphological and electrochemical perspectives. Importantly, deposition of nanofibers from chemically synthesized hybrids can be achieved homogenously, on nanoscale dimensions. The morphologies of these assemblies were evaluated by SEM, whereas their electroactivity was characterized by cyclic voltammetry. Electrochromic devices made from hybrid nanofiber electrodes exhibited highest chromatic contrast of 37.66% for PEDOT/WO3/BMIMPF6, 40.42% for PPy/WO3/BMIMBF4 and show a strong electrochromic color change from transparent to light brown. Furthermore, the nanofiber devices exhibit outstanding stability when color switching proceeds, which may ensure a versatile platform for color displays, rear-view mirrors and smart windows.

Perspectives on nanofiber dressings for the localized delivery of botanical remedies in wound healing

Based on their antiseptic and anti-inflammatory properties, plant-derived remedies and herbal products have been used since ancient times for wound and burn cure as well as for treating chronic skin diseases like dermatitis and eczema. Biocompatible and biodegradable polymer nanofiber devices are currently fabricated using sophisticated engineering techniques. Such nanofiber structures have proven efficacious for the localized delivery of therapeutic agents for the treatment of wounds due to their unique physical-chemical properties such as large surface-area-to-volume ratio, high porosity, improved cell adherence, cellular proliferation and migration, as well as controlled in vivo biodegradation rates. The remit of this communication is to highlight the methodology used for the fabrication of nanofiber mats and dressings for the localised delivery of herbal products and plant-derived ingredients for wound healing.

Nanofiber devices for the targeted-delivery of therapeutically active plant and herbal ingredients

Herbal and plant based remedies have been used since times immemorial for treating illnesses or maladies of variant aetiology, whereas during the past two centuries, the pharmaceutical chemists have discovered many important modern drugs from natural botanicals and microbes. Generally, herbal and plant-derived products containing multiple compounds are administered orally for therapeutic purposes. Currently, targeted drug-delivery systems are being developed and investigated for the treatment of cardio-respiratory disorders, pain relief, wound healing, and life threatening diseases like cancers. A number of novel nanofiber membranes and devices are available for sustained release and to deliver steady supply of natural bioactive ingredients, herbal-based extracts, and a few have been approved by US-FDA and other drug regulatory agencies. The purpose of this mini review is to provide an update on the role of nanofiber devices used for the targeted-delivery of therapeutically active ingredients of plant and herbal origin as well as to underscore the potential for the delivery of cost-effective herbal ingredients and natural plant-based extracts for their biomedical applications in wound healing, inflammation-related diseases and cancer treatment. Biomed Rev 2015; 26: 37-42. Key words: targeted-delivery, natural botanicals, plant-derived ingredients, nanofibrous medical devices, biodegradable and biocompatible polymers

Stacking fault induced tunnel barrier in platelet graphite nanofiber

A correlation study using image inspection and electrical characterization of platelet graphite nanofiber devices is conducted. Close transmission electron microscopy and diffraction pattern inspection reveal layers with inflection angles appearing in otherwise perfectly stacked graphene platelets, separating nanofibers into two domains. Electrical measurement gives a stability diagram consisting of alternating small-large Coulomb blockade diamonds, suggesting that there are two charging islands coupled together through a tunnel junction. Based on these two findings, we propose that a stacking fault can behave as a tunnel barrier for conducting electrons and is responsible for the observed double-island single electron transistor characteristics.

Fabrication and characterization of on-chip optical nonlinear chalcogenide nanofiber devices

Chalcogenide (As(2)S(3)) nanofibers as narrow as 200 nm in diameter are drawn by the fiber pulling method, are successfully embedded in SU8 polymer, and form on-chip waveguides and high-Q microknot resonators (Q = 3.9 × 10(4)) with smooth cleaved end faces. Resonance tuning of resonators is realized by localized laser irradiation. Strong supercontinuum generation with a bandwidth of 500 nm is achieved in a 7-cm-long on-chip chalcogenide waveguide. Our result provides a method for the development of compact, high-optical-quality, and robust photonic devices.

Submicron organic nanofiber devices with different anode-cathode materials: A simple approach

The authors present a simple general method for simultaneously producing tens of submicron electrode gaps with different cathode and anode materials on top of nanofibers, nanowires, and nanotubes, with an optional gap size variation. Using this method, an ensemble of para-hexaphenylene (p6P) nanofiber devices of different length was fabricated with Sm and Au electrodes. The measured I-V characteristics are in agreement with a nonlinear hopping transport model, where domain barriers dominate the transport with an estimated domain size of 23±5 nm.

Theoretical investigation of nanowaveguide‐based optical coupler using mode expansion transfer matrix

AbstractWe report a mode expansion transfer matrix method to describe the nanowaveguide‐based strongly coupling waveguide directional couplers, including slab nanowaveguide coupler, silicon‐on‐insulator (SOI) nanowires coupler, and silica nanofibers coupler. We propose a general mode expansion description of coupler without the assumption of weakly guiding. For the slab nanowaveguide case, all the coefficients inside those matrices could be identified theoretically using mode expansion method. The analytical results of coupler show excellent agreement with the simulation results obtained by the finite‐difference time‐domain method. For the nanofiber coupler, with the mode profiles obtained numerically using finite element method, similar matrix equation could be used for the guideline of nanofiber coupler design, which is the key issue of coupler‐based nanofiber devices and SOI nanowires devices. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1123–1129, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25093

The fabrication of photosensitive self-assembly Au nanoparticles embedded in silica nanofibers by electrospinning

In this study, we demonstrated a simple, efficient, and low-cost method to fabricate large-area self-assembly Au nanoparticles (AuNPs) encapsulated within silica nanofibers (Au/SiO 2). The method is based on electrospinning and thermal decomposition of hybrid nanofibers prepared from the solution of tetraethylorthosilicate (TEOS), polyvinylpyrrolidone (PVP) and AuNPs. This study employed the electrospinning technique for the first time as a successful method for preparing a self-organized AuNP peapod chain in a silica nanofiber matrix, under mild conditions. It has the advantage of easily controlling the diameters of the silica nanofibers as well as the concentration of the AuNPs in the spinning solution. The Au/SiO 2 hybrid nanofibers fabricated by this method exhibited an obvious photoelectric response under the illumination wavelength around the Au/SiO 2 nanofibers surface plasmon resonance (SPR) absorption band, whereas no photoelectric response was observed for the pure silica fibers. The excellent characteristics of photoelectric response suggest that the electrospinning technique has a great potential for large-scale fabrication of functional nanofiber devices. The ability of coupling light responses into the nanosystems dependent on metallic nanoparticle SPR opens up new prospects for the construction of nanoscale waveguiding devices, sensors and optoelectronics.

The Effect of Atmosphere and ZnO Morphology on the Performance of Hybrid Poly(3-hexylthiophene)/ZnO Nanofiber Photovoltaic Devices

We present detailed investigations of the fabrication and characterization of photovoltaic devices consisting of poly(3-hexylthiophene) (P3HT) intercalated into a mesoporous structure of ZnO nanofibers. ZnO nanofibers were grown via a low-temperature hydrothermal route from a solution of zinc nitrate precursor. P3HT was spin-coated on top of the structure, and intercalation into the voids between the nanofibers was induced with annealing. A silver electrode was used as the top contact. Spin-coating, storage, and testing of the device were performed in air. We discuss the effects of atmosphere and ZnO nanofiber morphology on device performance. Optimized nanofiber devices exhibited a 4-fold increase in the short circuit current (2.17 mA/cm2) as compared to that of a planar ZnO−P3HT bilayer device (0.52 mA/cm2) as a result of the increased donor−acceptor interfacial area. The efficiency of the nanofiber based device under 1 sun-simulated solar illumination was 0.53% and was found to increase at higher incident light intensities, reaching a value of 0.61% at 2.5 suns. Additionally, we found that for these devices fabrication in and exposure to air is required to obtain good diode characteristics. We also show that the morphology of the ZnO nanostructures in the nanocomposite directly impacts device performance. Treatment of the ZnO surface using surfactants increased the open circuit voltage at the expense of the short circuit current; however, there was little effect on overall device efficiency. Because of the inverted geometry of this device that allowed for the use of a silver top contact, the device was not susceptible to oxidative degradation when stored in the dark.

Size effect in polymer nanofibers under tension

This article studies the size effect on the elastic behavior of solid and hollow polymer nanofibers (e.g., electrospun nanofibers) subjected to uniaxial tension. A one-dimensional nonlinear elastic tension model is proposed that takes into account the coupling effect of fiber elastic deformation and surface tension. The fiber axial force-displacement and stress-strain relations are obtained in explicit forms. It is shown that, at nanoscale, fiber radius has appreciable effect on the elastic response of polymer nanofibers. With consideration of the fiber radial effect, it is shown that the actual contribution of surface energy of the solid polymer fibers to the axial tensile force is πr0γ rather than 2πr0γ (where r0 is the fiber radius after deformation and γ is the surface tension), as commonly used in literature. Compared to solid polymer fibers, the tensile behavior of hollow polymer nanofibers appears more complex with greater axial stiffening effect depending upon the combination effect of the fiber exterior and interior radii and the material properties. The results presented in this study can be utilized for data reduction of the nanoscale tension tests of polymer nanofibers and the analysis and design of nanofiber devices.

Electrochemical fabrication and electronic behavior of polypyrrole nano-fiber array devices

Electrochemically active Polypyrrole (PPy) nano-fiber array device was fabricated via electrochemical deposition method using aluminum anodic oxide (AAO) membrane as template. After alkaline treatment electrochemically active PPy nano-fiber lost electrochemical activity, and became electrochemically inactive PPy. The electronic properties of PPy nano-fiber array devices were measured by means of a simple method. It was found that for an indium–tin oxide/electrochemically inactive PPy nano-fiber device, the conductivity of nano-fiber increased with the increase of voltage applied on the two terminals of nano-fiber. The electrochemical inactive PPy nano-fiber might be used as a nano-fiber switching diode. Both Au/electrochemically active PPy and Au/electrochemically inactive PPy nano-fiber devices demonstrate rectifying behavior, and might have been used for further application as nano-rectifiers.