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JAPAN NANONET BULLETIN
-- 61st Issue -- January 5, 2006
Nanotechnology Researchers Network Center of Japan
Ministry of Education, Culture, Sports, Science and Technology (MEXT)
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IN THIS ISSUE
Nanonet Interview:
"Photonics polymers
-- Fundamental principles led to breakthrough --"
Yasuhiro KOIKE, Professor, Department of Applied Physics and
Physico-informatics, Faculty of Science and Technology, Keio
University
Young Researchers' Introduction:
"Single molecule measurements of bio-molecules"
Akihiko ISHIJIMA, Associate Professor, Department of Materials
Science and Engineering, Graduate School of Engineering, Nagoya
University
-- NANO CALENDAR --
For information on nanotechnology related symposiums and conferences
held in the world,
http://www.nanonet.go.jp/english/calendar/
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NANONET INTERVIEW
Photonics polymers
-- Fundamental principles led to breakthrough --
(Issued in Japanese: March 23, 2004)
Yasuhiro KOIKE, Professor, Department of Applied Physics and
Physico-informatics, Faculty of Science and Technology, Keio
University
"White is not a color. It appears white because of the light
scattering. The smaller the size of constituent particles of a
substance is, the less light scatters. So, milk could be transparent,"
says Prof. Koike. Light reflects and refracts with millimeter-sized
substances, and it scatters with micrometer-sized substances. However,
it does not scatter with nanometer-sized substances; therefore,
nanometer-sized substances are transparent. Prof. Koike has overcome
the difficulties in dealing with light by reviewing the fundamental
principles of light.
In the early 80's, plastics were thought to be unsuitable for optical
fibers due to the high scattering loss. Prof. Koike proposed using
plastic optical fibers for high-speed data transmission with rates in
excess of 1 Gbps. In order to realize the high-speed data transmission,
waveforms of light have to be constant through the whole length of the
fiber, so, he proposed the concept of graded-index (GI) fiber as a
fiber core structure, where a refractive index decreases with
increasing radial distance from the center of the fiber. The idea was
based on the fact that the light in the center of the fiber travels
slower than light in the outer part; therefore, both lights reach the
end of the fiber at the same time. However, the addition of impurities
into the polymers is needed to change the refractive index. At the
time, most of the researchers were focused on reducing the impurities
in order to decrease scattering loss and did not accept his idea.
"Scattering loss is caused not by the amount of impurities but the
particle size of impurities. If the particle size of the impurities is
reduced to about a nanometer, the particles do not scatter light, and
thus, the fiber remains transparent," says Prof. Koike. He tried to
prove his theory using polymethyl methacrylate (PMMA), which has the
highest transparency. However, the experimental value of excess light
scattering was 10 times higher than the theoretical value, and
therefore, his research did not go well.
Prof. Koike, who had given up once on plastic optical fiber research,
decided to start all over with defining "what is scattering". He
studied Einstein's fluctuation theory of light scattering and the
theory involving the structures of polymers and light scattering,
which Debye published in 1947. After fabricating PMMA without coarse
impurity particles, Prof. Koike researched and determined the cause of
excess light scattering in 1992. He verified that "stereoregularity of
PMMA", "molecular weight", "remaining low-molecular-weight impurities
such as additives and monomers" and "bridging by gel effects" were not
the true causes of excess light scattering. He theoretically and
experimentally determined that voids formed during polymerization
below the secondary phase transition temperature caused excess light
scattering. The voids can be eliminated by heat treatment at high
temperatures above the secondary phase transition temperature. He says,
"It was good that my research did not go well. If it went well, I
would not have gone over the basic question, i.e. what is light
scattering. The essentials of a true breakthrough cannot be found in
superficial research but in fundamental principles." It took him 10
years to finally develop Graded Index plastic optical fibers by
determining the nature of excess light scattering and fabricating PMMA
with high transparency. In 1996, he developed perfluorinated fibers
that reduce absorption loss by replacing hydrogen with fluorine in the
polymers. In 2000, high-speed data transmission plastic optical fibers,
which surpassed glass fibers, were commercialized.
Prof. Koike explored the field of "photonics polymer", clarified
interaction between polymers and lights, and developed various
materials, such as a zero-birefringence optical polymer, which
drastically reduces the manufacturing cost of liquid crystal display
(LCD), and a highly scattering optical transmission polymer, which
makes LCD backlights twice brighter than the conventional ones. His
aim is to develop a true broadband environment, not Fiber-to-the-Home,
but Fiber-to-the-Display, with photonics polymers. In the Fiber-to-the
-Display architecture, remote medical care can be realized because
clear pictures can be sent to the display in real time. He says, "If a
TV is connected to a hospital via optical fibers, it would be possible
to access the hospital remotely just by pressing a button on the side
of the TV whenever medical care is needed. If an elderly person gets
sick in the middle of the night, do you think they can turn a computer
on and type on the keyboard? Technology must be a useful tool to make
our lives easier; it becomes useless if it is complicated to use even
though it is advanced. The essence of technology is to make our lives
secure and comfortable."
(Interviewer: Rie Onuki, Cosmopia Inc.)
For more information,
http://www.nanonet.go.jp/english/mailmag/2005/061a.html
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YOUNG RESEARCHERS' INTRODUCTION
Single molecule measurements of bio-molecules
(Issued in Japanese: July 7, 2004)
Akihiko ISHIJIMA, Associate Professor, Department of Materials
Science and Engineering, Graduate School of Engineering, Nagoya
University
In the living body, bio-molecules, such as proteins, which undergo
self-assembly, are part of molecular machines. They have various
functions that are required for life, movement, signal processing, and
the reading of genetic code. Molecular machines are dozens of
nanometers in size and are made very skillfully, and it is thought
that the machines operate via different mechanisms from those of
artificial machines. Although a large amount of research has been done
to elucidate the functions of bio-molecules, they are still not fully
understood. In order to fully investigate bio-molecules, we must be
able to see them directly and to manipulate them.
We are trying to determine the mechanisms of different functions, such
as movement of a bio-molecule, using single molecule imaging and
single molecule nano-manipulation technology that were developed
recently. To measure the movement of a bio-molecule at the level of a
single molecule, a measurement system, which has a resolution of one
nanometer and a pico-newton order in aqueous solution, is required.
However, since the equipment cannot be purchased, we are developing
and using it to make actual measurements.
The bio-molecular motors that we are studying can be divided into two
groups: linear motors and rotary motors. A linear motor, such as
muscle contraction, moves on a rail protein, and almost all of the
movements in living cells are of the linear motor type. Rotary motors
can be found in bacteria, ATP synthesized enzymes, etc. and rotates
using a flow of ions. We have been studying the movement on the single
molecule level of these two kinds of motors. In particular, we have
determined the step size of displacement, the coupled chemical
reaction and load dependency for the movement of the linear motor
Chara myosin.
In addition, we have determined details about the motor rotation, ion
concentration dependency and the relationship between torque and
rotational frequency for the bacteria flagella rotary motor. Further,
by increasing the resolution of our apparatus, we plan to elucidate
the energy conversion mechanism of bio-molecules.
For more information,
http://www.nanonet.go.jp/english/mailmag/2005/061b.html
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