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Full-Text Articles in Engineering
Osteogenic Differentiation Of Marrow Stromal Cells On Random And Aligned Electrospun Poly(L-Lactide) Nanofibers, Junya Ma, Xuezhong He, Esmaiel Jabbari
Osteogenic Differentiation Of Marrow Stromal Cells On Random And Aligned Electrospun Poly(L-Lactide) Nanofibers, Junya Ma, Xuezhong He, Esmaiel Jabbari
Esmaiel Jabbari
No abstract provided.
Effect Of A Low-Molecular-Weight Cross-Linkable Macromer On Electrospinning Of Poly(Lactide-Co-Glycolide) Fibers, Weijie Xu, Xuezhong He, Alireza Sarvestani, Esmaiel Jabbari
Effect Of A Low-Molecular-Weight Cross-Linkable Macromer On Electrospinning Of Poly(Lactide-Co-Glycolide) Fibers, Weijie Xu, Xuezhong He, Alireza Sarvestani, Esmaiel Jabbari
Esmaiel Jabbari
No abstract provided.
Electrospun Nanofibers For Potential Space-Based Applications, G. Zhang, W. Kataphinan, R. Teye-Mensah, P. Katta, L. Khatri, E. Evans, George Chase, R. Ramsier, Darrell Reneker
Electrospun Nanofibers For Potential Space-Based Applications, G. Zhang, W. Kataphinan, R. Teye-Mensah, P. Katta, L. Khatri, E. Evans, George Chase, R. Ramsier, Darrell Reneker
Darrell Hyson Reneker
SiO2 nanofibers have been produced by the electrospinning method by two different approaches: direct spinning of silica precursor-containing nanofibers and spinning of polymer nanofibers followed by sol–gel silica coating. After pyrolysis of the resulting materials, both methods yield silica nanofibers. We extend this work by coating the silica nanofibers with AlN films using a reactive magnetron sputtering technique. Substrate temperature, input gas composition and radio frequency (rf) power are the critical operating parameters for the formation of different crystal structures of the AlN shells. The AlN/SiO2 core-shell heterostructures demonstrate that electrospinning has the potential to produce low-mass, high-surface-area flexible nanofibers …
Development Of Carbon Nanofibers From Aligned Electrospun Polyacrylonitrile Nanofiber Bundles And Characterization Of Their Microstructural, Electrical, And Mechanical Properties, Zhengping Zhou, Chuilin Lai, Lifeng Zhang, Yong Qian, Haoqing Hou, Darrell Reneker, Hao Fong
Development Of Carbon Nanofibers From Aligned Electrospun Polyacrylonitrile Nanofiber Bundles And Characterization Of Their Microstructural, Electrical, And Mechanical Properties, Zhengping Zhou, Chuilin Lai, Lifeng Zhang, Yong Qian, Haoqing Hou, Darrell Reneker, Hao Fong
Darrell Hyson Reneker
Carbon nanofibers with diameters of 200–300 nm were developed through stabilization and carbonization of aligned electrospun polyacrylonitrile (PAN) nanofiber bundles. Prior to the oxidative stabilization in air, the electrospun PAN nanofiber bundle was tightly wrapped onto a glass rod, so that tension existed during the stabilization. We also investigated several carbonization procedures by varying final carbonization temperatures in the range from 1000 to 2200 °C. The study revealed that: (1) with increase of the final carbonization temperature, the carbon nanofibers became more graphitic and structurally ordered; (2) the carbon nanofiber bundles possessed anisotropic electrical conductivities, and the differences between the …
Liquid Drop Growth On A Fiber, A. Yarin, George Chase, W. Liu, S. Doiphode, Darrell Reneker
Liquid Drop Growth On A Fiber, A. Yarin, George Chase, W. Liu, S. Doiphode, Darrell Reneker
Darrell Hyson Reneker
A quantitative model is described and verified to predict the growth of oil droplets by coalescence on a single nanofiber. The model considers a stream of fluid carrying many tiny droplets of a different fluid. The mechanisms by which the tiny droplets are captured by a drop growing on a fiber are considered. Different capture mechanisms are examined, including interception, Brownian motion of droplets, and vapor deposition by diffusion. It is shown that droplet interception and Brownian diffusion contribute to drop growth on nanofibers for airborne oil droplets in the size range from 100 to 1000 nm. Merging of growing …
Selective Emitters For Thermophotovoltaics: Erbia-Modified Electrospun Titania Nanofibers, V. Tomer, R. Teye-Mensah, J. Tokash, N. Stojilovic, W. Kataphinan, Edward Evans, George Chase, R. Ramsier, D. Smith, Darrell Reneker
Selective Emitters For Thermophotovoltaics: Erbia-Modified Electrospun Titania Nanofibers, V. Tomer, R. Teye-Mensah, J. Tokash, N. Stojilovic, W. Kataphinan, Edward Evans, George Chase, R. Ramsier, D. Smith, Darrell Reneker
Darrell Hyson Reneker
Titania nanofibers were synthesized by electrospinning and characterized with scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The nanofibers were annealed to 773 K to achieve the anatase titania crystal structure, and to 1173 K to obtain the rutile phase. In order to create erbia-containing titania nanofibers, erbium (III) oxide particles were added to the pre-cursor solution before electrospinning. After pyrolysis the titania nanofibers supported and encapsulated the erbia particles. Temperature-dependent near-infrared emission spectra demonstrate that the erbia-containing nanofibers emit selectively in the range 6000–7000 cm−1. Because of their large surface to volume ratios and narrow-band optical emission, these …
Structure And Morphology Of Electrospun Silk Nanofibers, Shahrzad Zarkoob, R. Eby, Darrell Reneker, Steven Hudson, Dale Ertley, Wade Adams
Structure And Morphology Of Electrospun Silk Nanofibers, Shahrzad Zarkoob, R. Eby, Darrell Reneker, Steven Hudson, Dale Ertley, Wade Adams
Darrell Hyson Reneker
Nanoscale fibers of natural silks of Bombyx mori and Nephila clavipes were produced from solutions in hexafluoro-2-propanol. The electrospun fibers were observed by optical, scanning electron, and transmission electron microscopy. These nanofibers showed optical retardation, appeared to have a circular cross-section, and were thermally stable under nitrogen to 280 °C (N. clavipes) and to 245 °C (B. mori). The diameter of the fibers ranged from approximately 6.5–200 nm making them orders of magnitudes smaller than the natural silks spun by most silkworms and spiders. The smallest fiber diameters correspond to 200 molecules in the cross section of the N. clavipes …
Nanofibers And Spheres By Polymerization Of Cyanoacrylate Monomer, Sphurti Doiphode, Darrell Reneker, George Chase
Nanofibers And Spheres By Polymerization Of Cyanoacrylate Monomer, Sphurti Doiphode, Darrell Reneker, George Chase
Darrell Hyson Reneker
A unique method for creating polymer nanofibers and spheres on a variety of substrates is described. Cyanoacrylate monomer vapor was collected on a solid surface and polymerized to form nanofibers. Tiny spots of initiator on the surface of a substrate and small monomer droplets in a monomer vapor appear to be required for the growth of the polycyanoacrylate nanofibers. The polycyanoacrylate nanofibers create a network and increase the specific surface area significantly.
Carbon Nanotubes On Carbon Nanofibers: A Novel Structure Based On Electrospun Polymer Nanofibers, H. Hou, Darrell Reneker
Carbon Nanotubes On Carbon Nanofibers: A Novel Structure Based On Electrospun Polymer Nanofibers, H. Hou, Darrell Reneker
Darrell Hyson Reneker
No abstract provided.
Corona Discharge From Electrospinning Jet Of Poly (Ethylene Oxide) Solution, Sureeporn Tripatanasuwan, Darrell Reneker
Corona Discharge From Electrospinning Jet Of Poly (Ethylene Oxide) Solution, Sureeporn Tripatanasuwan, Darrell Reneker
Darrell Hyson Reneker
Corona discharges from electrospinning jets were observed and photographed at the tip of the Taylor cone, and in a cylindrical region around the jet, a few millimeters below the tip. The corona discharge was also faintly visible to a dark adapted eye. At the position at which the cylindrical corona discharge became apparent, typical conditions were a jet diameter of 30 μm, an applied potential of 12 kV, and a calculated radial electric field of 400 kV/cm, The calculated electric field required to create a corona in air around a metal wire of the same diameter, calculated from Peek's empirical …
Buckling Of Jets In Electrospinning, Tao Han, Darrell Reneker, Alexander Yarin
Buckling Of Jets In Electrospinning, Tao Han, Darrell Reneker, Alexander Yarin
Darrell Hyson Reneker
Various buckling instabilities of electrospinning jets were observed and compared with the buckling instabilities of uncharged fluid jets. Buckling instability arises due to jet compression at impingement on a collector surface and occurs independently of the electrical bending instability. The velocity, diameter, density and viscosity of the electrospinning jets are the key factors that determine the buckling frequency. The electrically charged jets impinging onto grounded, horizontal or inclined (wedge-like) electrodes moving laterally at a constant velocity are studied experimentally. Straight and bending (electrospinning) jets emerge at short and sufficiently long inter-electrode distances, respectively. The experiments show that both straight segment …
Effect Of Evaporation And Solidification Of The Charged Jet In Electrospinning Of Poly (Ethylene Oxide) Aqueous Solution, Sureeporn Tripatanasuwan, Zhenxin Zhong, Darrell Reneker
Effect Of Evaporation And Solidification Of The Charged Jet In Electrospinning Of Poly (Ethylene Oxide) Aqueous Solution, Sureeporn Tripatanasuwan, Zhenxin Zhong, Darrell Reneker
Darrell Hyson Reneker
The electrospinning process uses electrical force to produce nanofibers. A charged droplet acquires a conical shape known as the Taylor cone and then becomes unstable. A charged jet emerges from the vertex and develops a spiral path due to the electrically driven bending instability, which makes it possible, in a small space, for the jet to elongate by a large amount and produce nanofibers. Evaporation and the associated solidification were identified as important factors that affect the diameter of electrospun nanofibers. In this study, the evaporation rate and solidification of the charged jet were controlled by varying the relative humidity …
Viscoelastic Electrospun Jets: Initial Stresses And Elongational Rheometry, Tao Han, Alexander Yarin, Darrell Reneker
Viscoelastic Electrospun Jets: Initial Stresses And Elongational Rheometry, Tao Han, Alexander Yarin, Darrell Reneker
Darrell Hyson Reneker
A novel method of characterization of viscoelastic longitudinal stresses in electrospun jets of semi-dilute and concentrated polymer solutions and melts is introduced. The measured longitudinal stresses at the beginning of the thin jet region in the jets of a 6 wt% aqueous solution of polyethylene oxide (Mw = 400 kDa) were of the order of 100 kPa, which is two orders of magnitude larger than in any other free viscoelastic jets issued from nozzles and orifices. This is attributed to elongation-driven stretching of polymeric liquids in the transition zone, between the preceding modified Taylor cone zone and the beginning of …
Hydrogel Microstructures Combined With Electrospun Fibers And Photopatterning For Shape And Modulus Control, Kyle Anderson, David Lu, Michael Mcconney, Tao Han, Darrell Reneker, Vladimir Tsukruk
Hydrogel Microstructures Combined With Electrospun Fibers And Photopatterning For Shape And Modulus Control, Kyle Anderson, David Lu, Michael Mcconney, Tao Han, Darrell Reneker, Vladimir Tsukruk
Darrell Hyson Reneker
In order to improve the sensitivity of hair cell sensors for fluid flow detection, poly-ethylene oxide acrylic macromonomer is used as a crosslinkable photo-patterned material capable of being swollen into a hydrogel of different shapes and sizes. We demonstrated that simple arrays of various hydrogel structures can be synthesized by photopatterning with photomasks. The mechanical properties of the hydrogel materials were measured to be in the range of 5–100 Pa under varying crosslinking conditions. Additional support for these high-aspect ratio hydrogel structures was provided with electrospun polycaprolactone microfibers that were deposited onto the microfabricated hairs. These fibers served as scaffolding …
Pendulum-Like Motion Of Straight Electrified Jets, Tao Han, Darrell Reneker, Alexander Yarin
Pendulum-Like Motion Of Straight Electrified Jets, Tao Han, Darrell Reneker, Alexander Yarin
Darrell Hyson Reneker
A novel phenomenon, a pendulum-like motion of the usually straight electrified jet was observed experimentally and theoretically modeled. Pendulum-like motion arises due to repulsive Coulomb force between the straight electrified jet and the charges accumulated on the collector. This electrical force repels the similarly charged landing jet segment in the collector plane. The motion is transferred to the whole jet via elastic stress sustained by the jet. The initially straight segment of the jet is arched. The pendulum-like motion has frequencies of the order of 10–102 Hz. The pendulum-like jets were collected onto grounded horizontal electrodes moving laterally at a …
Mechanical Properties Of Nanofibers Revealed By Interaction With Streams Of Air, Yinan Lin, Daniel Clark, Xiang Yu, Zhenxin Zhong, Kaiyi Liu, Darrell Reneker
Mechanical Properties Of Nanofibers Revealed By Interaction With Streams Of Air, Yinan Lin, Daniel Clark, Xiang Yu, Zhenxin Zhong, Kaiyi Liu, Darrell Reneker
Darrell Hyson Reneker
Electrospun nanofibers were captured directly between two steel rods that functioned as the “grips” of the tensile testing apparatus. Tension was applied to the selected nanofiber by displacing one of the grips at controlled rates or in steps. The stress was revealed by the deflection of a nanofiber, caused by the drag force from a broad stream of air, which flowed perpendicular to the fiber at a known velocity. The deflected position and shape of the nanofiber was observed with a light arrangement optimized to produce bright glints that were photographed with a camcorder. Image analysis of the catenary shapes …
Graphitic Carbon Nanofibers Developed From Bundles Of Aligned Electrospun Polyacrylonitrile Nanofibers Containing Phosphoric Acid, Zhengping Zhou, Kunming Liu, Chuilin Lai, Lifeng Zhang, Juanhua Li, Haoqing Hou, Darrell Reneker, Hao Fong
Graphitic Carbon Nanofibers Developed From Bundles Of Aligned Electrospun Polyacrylonitrile Nanofibers Containing Phosphoric Acid, Zhengping Zhou, Kunming Liu, Chuilin Lai, Lifeng Zhang, Juanhua Li, Haoqing Hou, Darrell Reneker, Hao Fong
Darrell Hyson Reneker
Graphitic carbon nanofibers (GCNFs) with diameters of approximately 300 nm were developed using bundles of aligned electrospun polyacrylonitrile (PAN) nanofibers containing phosphoric acid (PA) as the innovative precursors through thermal treatments of stabilization, carbonization, and graphitization. The morphological, structural, and mechanical properties of GCNFs were systematically characterized and/or evaluated. The GCNFs made from the electrospun PAN precursor nanofibers containing 1.5 wt.% of PA exhibited mechanical strength that was 62.3% higher than that of the GCNFs made from the precursor nanofibers without PA. The molecules of PA in the electrospun PAN precursor nanofibers initiated the cyclization and induced the aromatization during …
Recycled Expanded Polystyrene Nanofibers Applied In Filter Media, C. Shin, George Chase, Darrell Reneker
Recycled Expanded Polystyrene Nanofibers Applied In Filter Media, C. Shin, George Chase, Darrell Reneker
Darrell Hyson Reneker
In this work polystyrene (PS) nanofibers are electrospun from recycled expanded polystyrene (EPS). These fibers are mixed with micro glass fibers to modify the glass fiber filter media. The filter media are tested in the separation of water droplets from an emulsion of water droplets in oil. Water-in-oil emulsion separations are important to the petrochemical industries for product quality, safety, ecologic and economic reasons. The experimental results in this work show that polystyrene nanofibers with diameters of around 600 nm were produced by the electrospinning method. The addition of the nanofibers to conventional micron sized fibrous filter media improves the …
Effects Of Parameters On Nanofiber Diameter Determined From Electrospinning Model, C. Thompson, George Chase, A. Yarin, Darrell Reneker
Effects Of Parameters On Nanofiber Diameter Determined From Electrospinning Model, C. Thompson, George Chase, A. Yarin, Darrell Reneker
Darrell Hyson Reneker
In this paper the effects of 13 material and operating parameters on electrospun fiber diameters are determined by varying the parameter values in an electrospinning theoretical model. The complexity of the electrospinning process makes empirical determination of the effects of parameters very difficult. The results show that the five parameters (volumetric charge density, distance from nozzle to collector, initial jet/orifice radius, relaxation time, and viscosity) have the most significant effect on the jet radius. The other parameters (initial polymer concentration, solution density, electric potential, perturbation frequency, and solvent vapor pressure) have moderate effects on the jet radius. Parameters relative humidity, …