This study investigated the effect of rotational and translational target movement on electrospun nanofibers. Polyethylene oxide (PEO) stock solution was used to create non-aligned nanofibers via electrospinning. The fibers were then metalized with palladium using sputtering to form shells. The shells were analyzed using scanning electron microscopy and were found to form successfully. Rotational and translational movement of the target during electrospinning was found to produce more uniform fibers.

1. Translational and Rotational Target Effect on
Electrospun Nanofibers
José A. Cruz-Arzón1
, Edwin J. Alvarado2
Department of Biology, University of Puerto Rico at Cayey, PR1
Department of Mathematics-Physics, University of Puerto Rico at Cayey, PR1
A B S T R A C T
Using PEO stock solution, non-aligned nanofibers can be formed. The electrospinning technique makes
the formation of these fibers more bearable by using electrical conductivity. Independently if the fibers are aligned or
not, the metallization by Sputtering can be helpful because it adds less oxidation to the fibers, allowing them to be
seen under the electronic microscope. The shells formed by this process of Sputtering are what researchers are
looking for, because they have the ability of performing a specific function such as gas sensing. The electronic
microscope also helps in the characterization and analysis of the Nanofibers and more important the shells. If one
wants to study the shells in details, the calcination process can be a way of evaporating the fibers to characterize only
the shells previously metalized. This abstract seems incomplete to me because I do not see the objective of the
researchor the hypothesis, the methodology, the results, the conclusions, and the future directionnecessary in any
abstract of primary research.
Introduction
Nanofibers are fibers that one of their dimensions has
a diameter of 100nm or less. These Nanofibers are used
because of their high surface-to-volume ratio thatallows
certain substances and particles to attach to its surface in order
to perform a specific function. Their physicochemical
properties and high porosity allow the fibers to have a high
chemical reactivity with the particles attached to it, and any
other substance or chemical. These fibers have to first be
prepared using a solution-based method in order to produce a
fiber. PEO Nanofibers are a good example; they are made
based on a solution of 95% water and ethanol and 5% weight/
weight of the solute PEO. The solution has to be spun in
order to create a fiber. In this case, electrospinning is used to
produce the PEO nanofibers (Deitzel et al. 2001).
The electrospinning technique was reinforced on
1930 as a simple and versatile method for making fibers of
polymer solutions with the specified diameter (Katta et al.
2004). Other types of spinning involve melt spinning, solution
spinning, and gel state spinning. The electrospinning
technique uses a power supply to provide electricity so the
solution, placed inside a syringe, runs using electrical charges.
A negatively charged electrode would be attached to the
syringe, and a positively charged electrode to a collector which
has a substrate that is going to catch the fibers when they
deposit. The size of a syringe’s tip is going to create a slow
acceleration at the beginning, and then when it comes out
from the tip, a fast acceleration creates a fiber deposited on the
substrate. In this case, the substrate used is Silicon, because it
can be used to study conductivity and oxidation of the fibers.

2. Yet, there are two methods in which the fibers can be formed
by electrospinning, the aligned electrospinning method and
the non-aligned electrospinning. Basically, they both work the
same way, but the aligned electrospinning posses a moving
collector which has rotational and translational movement so
it can create more organized and aligned fibers for future
characterization. The objective was to determine the effect of
that aligned electrospinning on the fibers. The non-aligned
electrospinning just has a static collector. So the hypothesis
states that having rotational and x-translational target will
produce uniform fibers.
Certain other processes are involved in making a
good fiber for their usage. In case that the fibers cannot be
seen under an electronic microscope because of their high
oxidation thanks to electron bombing of the microscope, the
fibers have to go through a metallization process. A metal,
palladium, is deposited on the fiber inside a Vacuum Chamber
to avoid oxidation. Also, this metal forms a shell which can be
used for further studies in the field.
Nanofibers in this case are used as templates for the
formation of palladium shells which can be used for studies on
the sensing of certain gases such as Hydrogen.
Electrospinning also provides a variety of possibilities for the
formation of fibers. Collagen fibers are also synthesized using
electrospinning, but the collagen fiber is the material used for
Biomedical Applications, like the regeneration of the
hydroxyapatite in bones (Mathews et al. 2002). DNA
nanofibers can also be created using electrospinning, to study
their sequences in details.
Materials and Methods
The original solution planned to be used in this
experiment was PVA and Zn (Ac) 2 solution.However, due to
a possible contamination through humidity, the solution was
changed to a PEO stock solution (Deitzel et al. 2001). Before
beginning to use any other equipment, the use of gloves is
compulsory to avoid further contamination of the fibers or any
other samples. The electrospinning chamber used was the
non-aligned electrospinning chamber, because the aligned
fibers were already synthesized. A Vacuum Chamber was used
to metalize the fibers with palladium for the future creation of
shells. The Scanning Electron Microscope was used to
characterize the aligned and non-aligned fibers and analyze
the formation of shells on the fibers. Last of all, an oven was
used to calcinate the fibers and leave only the shells for
research of their capability as hydrogen sensors.
Electrospinning
Approximately 1.5ml of the PEO stock solution was
placed inside a syringe. The syringe was then placed inside the
electrospinning chamber with the negative electrode attached
to it, and the positive electrode attached to the substrate on
the target. The power supply was turned on at 20.0 KV at a
rate of 0.5 ml/hr. It took two hours for the solution to deposit
itself on the substrate creating the Nanofibers.
Sputtering or Metallization
The sample including the Silicon substrate and the
fibers, were placed inside the Vacuum Chamber to start the
metallization process by sputtering. The chamber was set to a
Base Pressure of 1.6 x 10-5
torr, a Deposition Pressure of
13mtorr and a power of 25 W. A magnet and a power source
together formed an electromagnetic field, which hadfree
electrons in constant motion within it. The electrons began to
collide with highenergy ions of argon, which was chemically
inert, creating plasma surrounding the target which contained
the metal, palladium. The collisions of electrons and ions
made the material of palladiumeject and start depositingitself
all over the inner surface of the chamber. Since the substrate,
containedsilicon and PEO fibers, facing the target, more
palladiumwasdeposited on the fiber sample. This process
occurred in a span of 2 minutes. After the deposition process
finished, it was important to remember to create a vacuum,
and fill the chamber with nitrogen to balance the pressure
from the outside, just before opening the chamber.

3. Characterization of the fibers
The characterization of the fibers wasdone under an
electronic microscope. The fibers were analyzed using a
magnification of 600×, 900×, 1,500×, 2,000×, 8,000×, 12,000×,
and 22,000×.
Calcination
The fibers were calcinatedfor 2 hours at 325 ºC,
causing the fibers to evaporateand isolating the palladium
shells. After the calcinations, the shells were analyzed again
under the microscope.
Fig.2 Palladium shells after calcination (SEM micrograph at 2,000×)
Results
The electrospinning process was done successfully,
and with the PEO fibers no contamination occurred. The
non-aligned fibers were done using the established parameters
(20.0V and 0.50 mL/h). Using the pressures established in the
Sputtering process, the palladium material was deposited on
the fibers inside the Vacuum Chamber. Using the electronic
microscope, the objective was accomplished.Rotational and
translational movement of the collector produced uniform and
more organized fibers. With the calcinations step completed,
the fibers used as a template were evaporated, leaving the
palladium shells for future characterization. These shells
were seen under a microscope. concluding that shells
were formed by the calcinations process letting further
research on the shells (This last part is not clear. Yet,
since you are concluding it should appear in thediscussion
section.).
Discussion
Non-aligned PEO fibers were produced to be
used as a template for further sensing of gases such as
hydrogen. One of the characteristics of palladium is that
it has a great affinity for gases, especially hydrogen, so the
palladium shells formed by the metallization of PEO fibers
can be a great material for gas sensing. As a conclusion, the
aligned PEO fibers could work better for the formation of
shells than the non-aligned fibers, because they are more
organized and uniform, allowing the deposition of palladium
to be more successful. Further research of the characteristics of
the aligned and non-aligned fibers could open doors for
improvements to the electrospinning technique for better fiber
production, and therefore forthe better formation of shells that
may be used for different kinds of functions that include not
only gas sensing, but also certain biomedical applications.
References
Katta P, Alessandro M, Ramsier R D, Chase GG. 2004.
Continuous electrospinning of aligned polymer
nanofibers onto a wire drum collector. Nano Lett
[Internet]. 4(11):2215-8.
Matthews JA, Wnek GE, Simpson DG, Bowlin GL. 2002.
Electrospinning of Collagen Nanofibers.
Biomacromolecules [Internet]. 3(2):232–8
Deitzel JM, Kleinmeyer JD, Hirvonen JK, Beck Tan NC.
2001. Controlled Deposition and Collection of
Electro-spun Poly (ethylene oxide) Fibers. ARL
[Internet]. 2415: 9-27