Subject: Nanobasics--part 1--NANOFIBERS... - msg#00069

Hai all,
I subscribe in a group which tells basics on nanotechnology. Here is the
part-1.
Hope it helps some one.
Cheers
Ranjith
=========================================================
Hello all,
I would like to inform you that starting from this week, every week I will
be presenting you the basics of a particular topic or term or anything
related to Nanotech. This covers all the basics of that particular topic.
This week's topic is NANOFIBERS. Here is the list of the contents that are
covered under this topic:
Nanofibers
1. What exactly are Nanofibers?
2. What are the raw materials used to produce them and the production
procedure?
3. What known products are Nanofibers used in?
4. Applications advantages and disadvantages of Nanofibers
5. Future Prospects of Nanofibers.
===============================
Here we go in detail
=============================
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.

A. 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

*B*. 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:

A. "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
B. A disadvantage of nano fibers is they are fragile comparitively and thus
easily
broken away from the application. Short peices can remain air bourne for
years, and are a significant hazzard to nono machines and human lungs and
are extemely difficult to remove from air or other gases and vapors.
-------------
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

Search terms used:
Nanofibers filters medical applications advantages disadvantages
problems issues future
====================================================================
Hope you all welcome this weekly Post of mine.......................
Regards,
Chaitu

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