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1. What are Nanofibers?
“These tubes or fibers are often called graphite or carbon nanofibers
as well as nanotubes. The technology for manufacturing carbon
nanotubes is very different from common fiber production techniques
and the end uses are not those commonly associated with fibers. The
nanofibers of interest to the fiber industry are polymeric nanofibers
made from conventional and newly emerging polymers and with end uses
typical of standard textiles.”
“Polymeric Nanofibers - Fantasy or Future?”
http://www.hillsinc.net/Polymeric.shtml
“The nanofibers consist of graphite platelets perfectly arranged in
various orientations with respect to the fiber axis, giving rise to
assorted conformations. One of the most outstanding features of these
structures is the presence of large number of edges, which in turn
constitute sites readily available for chemical or physical
interaction, particularly adsorption.”
“SYNTHESIS, PROPERTIES AND APPLICATIONS OF GRAPHITE NANOFIBERS”
http://www.wtec.org/loyola/nano/US.Review/09_03.htm
--------------
2. What raw materials are used to produce it and what is the
production procedure?
The usual production of nanofibers involves the method
Electrospinning.
i. Electrospinning
“Electrospinning is a straightforward and cost effective method to
produce novel fibers whose diameters range from less than 3 nm to over
1 um The unique qualities of nanofibers (NF) make them an attractive
candidate for new hi-tech products applications.”
“The electrospinning process used by the present group easily
incorporates particles of materials such as pigments, carbon black
particles, and many others into the produced nanofibers.
“Flexible fibers are needed on a scale commensurate with micro- or
nanoelectrical mechanical and optical systems (MEMS and NEMS).”
“NANOFIBERS FOR APPLICATIONS IN MEMS, NANOTECHNOLOGY,
BIOTECHNOLOGY AND MEDICINE”
http://hitech.technion.ac.il/~eyal/NanoFibers.html
ii. Nanofibers Manufacturing Techniques:
a. “The manufacturing techniques most after associated with polymeric
nanofibers is electrospinning. In this technique a polymer is
dissolved in a solvent (polymer melts can also be used) and placed in
a glass pipet tube sealed at one end with a small opening in a necked
down portion at the other end.”
b. “Another technique to produce polymeric nanofibers has recently
been introduced by Nanofiber Technology Inc. of Aberdeen, NC. In this
scheme described in preferences 4 & 5, nanofibers are created by melt
blowing a fiber with a modular die.”
c. “A third technique that can be used to produce nanofibers is
spinning bicomponent fibers that split or dissolve. There are several
approaches to using this technology to make nanofibers. The most
researched approach is the production of islands-in-the-sea (INS)
fibers using a standard spin/draw process.”
d. “Another possible approach to the use of bicomponent fiber spinning
to manufacture nanofibers is to make splittable fibers in a melt
spinning process.”
“Polymeric Nanofibers - Fantasy or Future?”
http://www.hillsinc.net/Polymeric.shtml
---------------
3. What known products are they used in?
“Polymer nanofibers are used in a variety of fields, including
filtration, protective clothing, biomedical applications such as wound
dressing and drug delivery systems, design of solar sails, light sails
and mirrors for use in space, application of pesticides to plants, as
well as for structural elements in artificial organs and in reinforced
composites.”
“NANOFIBERS FOR APPLICATIONS IN MEMS, NANOTECHNOLOGY,
BIOTECHNOLOGY AND MEDICINE”
http://hitech.technion.ac.il/~eyal/NanoFibers.html
“Nanofibers—about 100 times smaller in diameter than typical textile
fibers—have a very high surface area-to-mass ratio, potentially
offering performance advantages in fields ranging from tissue
engineering to protective clothing to catalyst supports and membranes
for chemical processing.”
“Prototype High-Throughput Electrospinning Process and Applications of
Electrospun NanoFibers”
http://www.atp.nist.gov/awards/00005289.htm
“The nanobattery has enhanced energy densities (lithium capacity per
mass). The objective is to produce and evaluate chemical vapor
deposited carbon nanotube anodes for thin film lithium ion batteries.
In contrast to carbon black, directed structured nanotubes and
nanofibers offer a superior intercalation media for Li ion batteries.”
“Nanotubes Offer Superior Media”
http://www.buscom.com/letters/bevtpromo/bevt/bevt.html
-----------------
4. Filtration Applications
a. Advantages:
“Adding small amounts of nanofibers can improve performance of fibrous
filter media.
Since the basic properties of filter media are improved it can be
applied to other applications also like gas-liquid and liquid-liquid
filtration.”
“Performance of Melblown fiber media with ‘NANOFIBERS’”
http://www.ecgf.uakron.edu/~chem/fclty/chase/1_Page_Summary_Anil%20Mar%2002.pdf
“Aerosol barrier properties were excellent in the particle size range
of interest with filtration efficiencies of 98% or better for all
liners containing nanofibers. In comparison, filtration efficiencies
were typically 13-30% in liners without nanofibers.”
“The very thin layer of nanofibers on the surface of the filter media
efficiently captures the particles while providing very little
resistance to airflow”
“Nanofibers for Chemical Protective Clothing Systems”
http://www.dtic.mil/dust/cgr/01army.htm
b. Disadvantage:
“The problem with nanotubes is that they are not easily obtainable,
their structure cannot be controlled, and results cannot be repeated.”
“FABRICATION AND PROPERTIES OF RAPID THERMALLY PROCESSED CARBON
NANOFIBERS”
http://216.239.37.100/search?q=cache:z5oiwfQQtzQC:www.ee.upenn.edu/~sunfest/pastProjects/Papers01/SantiagoSerrano.pdf+nanofibers+filter+problems&hl=en&ie=UTF-8
-------------
5. Medical Applications:
a. Bones:
“Researchers report in the journal Science they have designed a
nanoscale molecular scaffolding that resembles the basic structure of
bone.”
“Stupp said the nanofibers, approximately eight nanometers small, come
in the form of a gel that could be injected into a broken bone to help
the fracture-mending crystallization process.”
“Stupp said the nanofibers have implications far beyond bone repair.
They also could be tweaked to carry signals to cells, essentially
bearing instructions that tell cells how to differentiate to become
various kinds of tissues, such as nerves, skin or cartilage.”
“Nanofibers Could Help Bones Heal”
http://www.applesforhealth.com/HealthyFeatures/nanobone3.html
“Scientists design molecules that mimic nanostructure of bone”
http://www.bizspacebiotechnology.com/Q0104/nanostructure.htm
b. Orthopedic Dentistry:
“The current studies suggest carbon nanofiber surface characteristics
can be used to selectively enhance ostoeblast adhesion and minimize
competitive cell line adhesion. An orthopedic/dental implant material
with these properties has the potential to minimize the bone/implant
interface problems that can lead to implant failure and that are so
prevalent in the orthopedic/dental field today.”
“Carbon Nanofibers as Future Biomimetic Component of Orthopedic/Dental
Implant Designs”
http://www.aiche.org/conferences/techprogram/paperdetail.asp?PaperID=1716&DSN=annual01
--------------
6. Advantages:
“Key to reducing the hazards of ESD in a cleanroom barcode scanner is
the selection of minimally conductive materials for the housing. In
the case of Codestar Electronics, Inc., the engineers selected resins
from Hyperion Catalysis International that contain Graphite Fibril
nanofibers. The physical and electrical properties that these
microscopic fibers impart to PC, PBT and other resins offer critical
advantages over conventional carbon fibers.”
“Cleanroom Scanner Uses Nanofiber-Based Plastics”
http://www.manufacturingcenter.com/med/archives/0199/199ctch.asp
“Enzymes offer many uses in areas such as biosensing, drug delivery
and synthesis, and chemical processing due to their high selectivity,
efficiency, and mild reaction conditions. However, several
disadvantages of enzymes including poor stability, high cost, and slow
reaction rates, have limited the use of enzymes for large-scale
operations.”
“By improving the compatibility of the nanofibers with the reaction
media, the efficiency of the enzyme was enhanced by over 5,000 times.”
“Bioactive Nanofibers for Biotransformations”
http://216.239.33.100/search?q=cache:XlNKgwuzdt0C:www.ispe.org/educ/02annmtg-30.htm+nanofibers+disadvantages&hl=en&ie=UTF-8
------------
7. Disadvantages:
“Because of high costs and other factors such as health and safety
issues, there are currently few efficient and economic processes for
making high quality nanofibers at a commercial scale.”
“Prototype High-Throughput Electrospinning Process and Applications of
Electrospun NanoFibers”
http://www.atp.nist.gov/awards/00005289.htm
-------------
8. Future Applications:
a. Optical Systems:
“Flexible fibers are needed on a scale commensurate with micro- or
nanoelectrical mechanical and optical systems (MEMS and NEMS). NFs can
be used in MEMS as driving belts or as a reinforcing net (for novel,
extremely thin composites to be used in MEMS). They also can produce
especially effective filters and liquid absorbing fabrics.”
“NANOFIBERS FOR APPLICATIONS IN MEMS, NANOTECHNOLOGY,
BIOTECHNOLOGY AND MEDICINE”
http://hitech.technion.ac.il/~eyal/NanoFibers.html
b. Military Usage:
“Interest in nanofibers in textiles has piqued in the military, due to
the promise of increased protection from the low density, high
porosity, high surface area of these fibers. Research at the U.S. Army
Research Laboratory (ARL), the University of Akron, and the U.S. Army
Soldier Systems Center - Natick (Natick) is aimed at incorporating
electrospun nanofibers into textiles in a number of ways.”
“Military and Academia Develop New Fabrics for Better Protection”
http://216.239.33.100/search?q=cache:jrWqxJIDeN0C:www.natick.army.mil/warrior/98/oct/spinning.htm+nanofibers+filter+media&hl=en&ie=UTF-8
c. Hydrogen Storage:
“Graphite nano-structures can be used to store hydrogen in e.g.
applications where hydrogen is used in fuel cells. The material
consists of graphite platelets arranged in a conformation that results
in slit-shaped pores. The space between the layers are large enough
for molecular hydrogen but too small for other gas molecules such as
oxygen and nitrogen. “
SAAB Microtech
http://www.saabmicrotech.se/node2693.asp
d. Space Construction:
“Nanofibers may offer the potential for creating some astoundingly
large and strong space structures; they may make the prospect of
rotating orbital colonies feasible.”
“The Use of Nanofibers in Space Construction”
http://www.distant-star.com/issue13/jan_2001_nanofibers.htm
e. Pollution Control:
“Carbon nanofibers have other areas of application as well. New
regulations on pollution control, especially for motor vehicles,
require innovative approaches to removing pollutants to meet minimum
levels.”
"’Carbon nanofibers might be the material to remove nitrogen compounds
from exhaust gases," says Baker. "Their light weight also makes them
valuable in combustion units to remove trace contaminants and in fuel
cells.’"
“Carbon Nanofibers in More Shapes Than Macaroni”
http://www.engr.psu.edu/news/News/1995%20Press%20Releases/April/carbon.html
f. Electronics:
“ORNL researchers have grown vertically aligned carbon nanofibers in a
controllable way and shown that electronic devices can be built from
these nanofiber materials.”
“They have also found out how to grow a needle-like carbon nanofiber
that could be used as a biological probe to measure electrochemical
changes in living cells or as a site-specific vehicle to deliver
molecules to an individual cell.”
“ORNL researchers have shown that carbon nanofibers can be used as
field emitters of electrons that can be focused for electron beam
lithography to create circuit patterns 10 to 100 nanometers across.”
“A single carbon nanofiber could be used as an atomic force microscope
(AFM) probe to replace the conventional AFM cantilever.”
“Improving Superconductors and Semiconductors”
http://www.ornl.gov/ORNLReview/v35_3_02/improving.shtml
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