Over a period of time, the typical path of a single jet of polymer solution, in the electrospinning process follows the nearly straight electric field lines for a certain distance away from the tip, ...and then develops a series of electrically driven bending instabilities that cause the path of the jet to explore a cone shaped envelope as the jet elongates and dries into a nanofiber. The multitudes of open loops that are formed are rarely observed to come into contact with each other until the dry nanofiber is collected at the end of the process.
A new phenomenon is reported in this paper. Electrospinning a solution of polycaprolactone in acetone caused the dramatic appearance of a fluffy, columnar network of fibers that moved slowly in large loops and long curves. The name ‘garland’ was given to the columnar network.
Open loops of the single jet came into contact just after the onset of the bending instability and then merged into a cross-linked network that created and maintained the garland. Contacts between loops occurred when the plane of some of the leading loops of the jet rotated around a radius of the loop. Then a small following loop, expanding in a different plane, intersected a leading loop that was as many as several turns ahead. Mechanical forces overcame the repulsive forces from the charge carried by the jet, the open loops in flight made contact and merged at the contact point, to form closed loops.
The closed loops constrained the motion to form a fluffy network that stretched and became a long roughly cylindrical column a few millimeters in diameter. This garland, which was electrically charged, developed a path of large open loops that are characteristic of a large-scale electrically driven bending instability. Over a long period of time, the fluffy garland never traveled outside a conical envelope similar to, but larger than the conical envelope associated with the bending instability of a single jet.
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 nanofibers can be used as selective emitters for thermophotovoltaic applications.
SiO
2 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/SiO
2 core-shell heterostructures demonstrate that electrospinning has the potential to produce low-mass, high-surface-area flexible nanofibers for potential space-based applications.
Solutions of Bombyx mori gland silk can be electrospun with the addition of some polyethylene oxide (PEO). Green fluorescent protein (GFP) can also be incorporated and electrospun without apparent ...phase separation from the silk. The dimensions of the fibers with and without the GFP are qualitatively similar. The results indicate the possibility of making fibers with uniform non-linear optical properties.
Improvement of catalytic efficiency of immobilized enzymes via materials engineering was demonstrated through the preparation of bioactive nanofibers. Bioactive polystyrene (PS) nanofibers with a ...typical diameter of 120 nm were prepared and examined for catalytic efficiency for biotransformations. The nanofibers were produced by electrospinning functionalized PS, followed by the chemical attachment of a model enzyme, α‐chymotrypsin. The observed enzyme loading as determined by active site titration was up to 1.4% (wt/wt), corresponding to over 27.4% monolayer coverage of the external surface of nanofibers. The apparent hydrolytic activity of the nanofibrous enzyme in aqueous solutions was over 65% of that of the native enzyme, indicating a high catalytic efficiency as compared to other forms of immobilized enzymes. Furthermore, nanofibrous α‐chymotrypsin exhibited a much‐improved nonaqueous activity that was over 3 orders of magnitude higher than that of its native counterpart suspended in organic solvents including hexane and isooctane. It appeared that the covalent binding also improved the enzyme's stability against structural denaturation, such that the half‐life of the nanofibrous enzyme in methanol was 18‐fold longer than that of the native enzyme.
