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JAPAN NANONET BULLETIN
-- 53rd Issue -- September 15, 2005
Nanotechnology Researchers Network Center of Japan
Ministry of Education, Culture, Sports, Science and Technology (MEXT)
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IN THIS ISSUE
Nanonet Interview:
"Nano-structured liquid crystals
-- Frontier of liquid crystal research --"
Hiroshi YOKOYAMA, Director, Nanotechnology Research Institute,
National Institute of Advanced Industrial Science and Technology
(AIST)
Young Researchers' Introduction:
"Fabrication of DNA sensors by using a self-assembled monolayer"
Fumio NAKAMURA, Senior Research Scientist, New Frontiers Research
Laboratories, Toray Industries, Inc.
-- 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
Nano-structured liquid crystals
-- Frontier of liquid crystal research --
(Issued in Japanese: January 20, 2004)
Hiroshi YOKOYAMA, Director, Nanotechnology Research Institute,
National Institute of Advanced Industrial Science and Technology
(AIST)
Liquid crystal displays are now an indispensable part of TVs, cellular
phones, digital cameras and so on. Since the early stage of its
development, Dr. Yokoyama has taken a lead in the fundamental research
involving the liquid crystal/substrate interface. Now, he has opened
the door to a whole new world of liquid crystal science and technology.
In liquid crystal devices, such as displays, liquid crystal molecules
are sandwiched between surface-treated glass plates in the proper
alignment. The orientation of the liquid crystal molecules directly
influences the performance of the devices. Demand for refinement and
higher working speeds of the devices has made the understanding of the
liquid crystal/substrate interface essential. Dr. Yokoyama says,
"I was doing fundamental research on the interface, and my interest
happened to match industrial needs." In the early 80's, he discovered
an "interface-induced phase transition", which is a different phase
transition from that of bulk liquid crystals, at the liquid crystal/
substrate interface. After that, he worked to characterize
thermodynamically the interface. Since the scaling rule can be applied
to liquid crystals, he was able to develop a method for measuring the
electro-optical response of the interface without any influence from
the bulk liquid crystals. This method has been used in the
manufacturing of liquid crystal devices to characterize the substrate/
liquid crystal interface prepared by orientation treatments such as
rubbing and deposition.
"There are three approaches to the characterization of liquid crystal/
substrate interfaces: the first is a macroscopic approach using
thermodynamics, the second is a molecular theory-approach using
statistical mechanics, and the third is a microscopic approach using
the properties of the individual molecules," says Dr. Yokoyama. After
implementing a thermodynamic approach, his interest gradually shifted
to the microscopic approach, and in the early 90's, he devised a new
method to determine the orientation of individual liquid crystal by
measuring the electrostatic potential on a surface and developed the
scanning Maxwell stress microscope by modifying an atomic force
microscope (AFM). The scanning Maxwell stress microscope was designed
to simultaneously investigate electrical properties, such as
potentials and charges, and surface shapes at the atomic/molecular
level, and it enabled Dr. Yokoyama to study the liquid crystal/
substrate interface on the nano-scale.
In 1999, the "Yokoyama Nano-Structured Liquid Crystal Project",
the Japan Science and Technology Agency (JST), was launched. Liquid
crystal molecules form nano-sized aggregates and these aggregates form
a higher-order structure due to long-range interactions. The goal of
the project has been to create liquid crystals with novel properties
by controlling the structure of the nano-sized aggregates, which is
the basic unit of its hierarchical structure. One of his group's
achievements is a "tristable memory liquid crystal device". Dr.
Yokoyama has elucidated the principles behind this type of device and
experimentally confirmed that it worked. In conventional orientated
liquid crystals, producing a memory device is not possible because the
liquid crystal molecules are stable only in one orientation. However,
liquid crystals with three metastable orientations can be prepared by
creating a pattern with six-fold rotational symmetry on the surface of
the substrates by AFM nano-rubbing. When an electric field is applied
parallel to one of the three metastable orientations, the orientation
is maintained without the electric field. This technology has opened
the way to design an ultra-low power-consumption display, where the
images never go away even when it is turned off.
"Nanotechnology is a fairly new field of technology, and it gives
researchers opportunities to explore the most state-of-the-art
scientific field. I hope young researchers will not be intimidated by
this unknown field. I want them to pursue not only currently known
research areas but also to create their own research areas in
nanotechnology. If others say your research is unsuitable for
nanotechnology, you should take it as a compliment and keep pursuing
it," says Dr. Yokoyama. He continued his research despite opinions
that the area of liquid crystals had been fully explored. He adds, "Doing
research is somewhat similar to archaeological excavation. Even if you
make a finding, it is not the end. There are more underneath the
finding."
(Interviewer: Asako Tsukasaki, Cosmopia Inc.)
For more information,
http://www.nanonet.go.jp/english/mailmag/2005/053a.html
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YOUNG RESEARCHERS' INTRODUCTION
Fabrication of DNA sensors by using a self-assembled monolayer
(Issued in Japanese: March 16, 2004)
Fumio NAKAMURA, Senior Research Scientist, New Frontiers Research
Laboratories, Toray Industries, Inc.
Recently, research and development efforts involving DNA sensors have
been focused on tailor-made therapeutic treatments or genetic
diagnostic analysis. However, sensitivity or reproducibility of
signal detection in current methods is not sufficient. To fabricate
highly sensitive and highly reproducible DNA sensors, DNA self-
assembled monolayers (SAM) were prepared on solid surfaces. Using
probe DNA, composed of single and double stranded portions of DNA, it
is possible to immobilize a probe DNA on a solid surface while
maintaining its activity.
We have developed three kinds of sensing systems:
1) using a DNA SAM,
2) using the SAM containing anthryl groups, and
3) using a "branched DNA" SAM containing multiple single stranded
probe portions in the probe DNA.
The combination of the SAM and surface plasmon resonance (SPR) allows
for the sensitive detection of target DNA without any fluorescence
labeling. Currently, we are using SPR microscopy in combination with
the different probes to detect efficiently and analyze DNA
hybridization in DNA arrays.
For more information,
http://www.nanonet.go.jp/english/mailmag/2005/053b.html
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Nanotechnology Researchers Network Center of Japan
Ministry of Education, Culture, Sports, Science and Technology (MEXT)
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