Guided growth of nanowires leads to self-integrated circuits

Guided growth of nanowires leads
to self-integrated circuits
This is a SEM image of a logic circuit
based on 14 nanowires. Credit:
Weizmann Institute of Science
Researchers working with tiny
components in nanoelectronics face a
challenge similar to that of parents
of small children: teaching them to
manage on their own. The nano-
components are so small that
arranging them with external tools is
impossible. The only solution is to
create conditions in which they can
be "trusted" to assemble themselves.
Much effort has gone into facilitating
the self-assembly of semiconductors,
the basic building blocks of
electronics, but until recently,
success has been limited. Scientists
had developed methods for growing
semiconductor nanowires vertically
on a surface, but the resultant
structures were short and
disorganized. After growing, such
nanowires need to be "harvested"
and aligned horizontally; since such
placement is random, scientists need
to determine their location and only
then integrate them into electric
circuits.
A team led by Prof. Ernesto
Joselevich of the Weizmann
Institute's Materials and Interfaces
Department has managed to
overcome these limitations. For the
first time, the scientists have created
self-integrating nanowires whose
position, length and direction can be
fully controlled.
The achievement, reported today in
the Proceedings of the National
Academy of Sciences ( PNAS), USA,
was based on a method developed
by Joselevich two years ago for
growing nanowires horizontally in an
orderly manner. In the present study
—conducted by Joselevich with Dr.
Mark Schvartzman and David Tsivion
of his lab, and Olga Raslin and Dr.
Diana Mahalu of the Physics of
Condensed Matter Department—the
scientists went further, creating self-
integrated electronic circuits from the
nanowires.
First, the scientists prepared a
surface with tiny, atom-sized grooves
and then added to the middle of the
grooves catalyst particles that served
as nuclei for the growth of
nanowires. This setup defined the
position, length and direction of the
nanowires. They then succeeded in
creating a transistor from each
nanowire on the surface, producing
hundreds of such transistors
simultaneously. The nanowires were
also used to create a more complex
electronic component—a functioning
logic circuit called an Address
Decoder, an essential constituent of
computers. These ideas and findings
have earned Joselevich a prestigious
European Research Council Advanced
Grant.
"Our method makes it possible, for
the first time, to determine the
arrangement of the nanowires in
advance to suit the desired electronic
circuit," Joselevich explains. The
ability to efficiently produce circuits
from self-integrating semiconductors
opens the door to a variety of
technological applications, including
the development of improved LED
devices, lasers and solar cells.
Provided by Weizmann Institute of
Science

Researchers overcome technical hurdles in quest for inexpensive, durable electronics and solar cells

Researchers overcome technical
hurdles in quest for inexpensive,
durable electronics and solar cells

Light is emitted from excited argon
gas atoms flowing through the glass
tube of a plasma reactor. The plasma
is a reactive environment used to
produce silicon nanocrystals that can
be applied to inexpensive, next-
generation electronics. Credit:
University of Minnesota
Electronic touch pads that cost just a
few dollars and solar cells that cost
the same as roof shingles are one
step closer to reality today.
Researchers in the University of
Minnesota's College of Science and
Engineering and the National
Renewable Energy Laboratory in
Golden, Colo., have overcome
technical hurdles in the quest for
inexpensive, durable electronics and
solar cells made with non-toxic
chemicals. The research was
published in the most recent issue of
Nature Communications , an
international online research journal.
"Imagine a world where every child
in a developing country could learn
reading and math from a touch pad
that costs less than $10 or home
solar cells that finally cost less than
fossil fuels," said Uwe Kortshagen, a
University of Minnesota mechanical
engineering professor and one of the
co-authors of the paper.
The research team discovered a novel
technology to produce a specialized
type of ink from non-toxic
nanometer-sized crystals of silicon,
often called " electronic ink." This
"electronic ink" could produce
inexpensive electronic devices with
techniques that essentially print it
onto inexpensive sheets of plastic.
"This process for producing
electronics is almost like screen
printing a number on a softball
jersey," said Lance Wheeler, a
University of Minnesota mechanical
engineering Ph.D. student and lead
author of the research.
But it's not quite that easy. Wheeler,
Kortshagen and the rest of the
research team developed a method
to solve fundamental problems of
silicon electronic inks.
First, there is the ubiquitous need of
organic "soap-like" molecules, called
ligands , that are needed to produce
inks with a good shelf life, but these
molecules cause detrimental residues
in the films after printing. This leads
to films with electrical properties too
poor for electronic devices. Second,
nanoparticles are often deliberately
implanted with impurities, a process
called "doping," to enhance their
electrical properties.
In this new paper, researchers
explain a new method to use an
ionized gas, called nonthermal
plasma, to not only produce silicon
nanocrystals, but also to cover their
surfaces with a layer of chlorine
atoms. This surface layer of chlorine
induces an interaction with many
widely used solvents that allows
production of stable silicon inks with
excellent shelf life without the need
for organic ligand molecules. In
addition, the researchers discovered
that these solvents lead to doping of
films printed from their silicon inks,
which gave them an electrical
conductivity 1,000 times larger than
un-doped silicon nanoparticle films.
The researchers have a provisional
patent on their findings.
"What this research means is that we
are one step closer to producing
more pure and more stable electronic
ink with non- toxic chemicals ,"
Kortshagen said. "The bigger goal
here is to find a way that this
research can benefit everyone and
make a real difference."
More information: "Hypervalent
Surface Interactions for Colloidal
Stability and Doping of Silicon
Nanocrystals," Nature
Communications , http://
www.nature.com/
ncomms/2013/130729/ncomms3197/
full/ncomms3197.html
Provided by University of Minnesota

Researchers discover universal law for light absorption in 2D semiconductors

Researchers discover universal law
for light absorption in 2D
semiconductors

(From left) Eli Yablonovitch, Ali Javey
and Hui Fang discovered a simple law
of light absorption for 2D
semiconductors that should open
doors to exotic new optoelectronic
and photonic technologies. Credit:
Roy Kaltschmidt, Berkeley Lab
From solar cells to optoelectronic
sensors to lasers and imaging
devices, many of today's
semiconductor technologies hinge
upon the absorption of light.
Absorption is especially critical for
nano-sized structures at the interface
between two energy barriers called
quantum wells, in which the
movement of charge carriers is
confined to two-dimensions. Now,
for the first time, a simple law of
light absorption for 2D
semiconductors has been
demonstrated.
Working with ultrathin membranes of
the semiconductor indium arsenide ,
a team of researchers with the U.S.
Department of Energy (DOE)'s
Lawrence Berkeley National
Laboratory (Berkeley Lab) has
discovered a quantum unit of photon
absorption , which they have dubbed
"A Q ," that should be general to all
2D semiconductors , including
compound semiconductors of the III-
V family that are favored for solar
films and optoelectronic devices. This
discovery not only provides new
insight into the optical properties of
2D semiconductors and quantum
wells , it should also open doors to
exotic new optoelectronic and
photonic technologies .
"We used free-standing indium
arsenide membranes down to three
nanometers in thickness as a model
material system to accurately probe
the absorption properties of 2D
semiconductors as a function of
membrane thickness and electron
band structure," says Ali Javey, a
faculty scientist in Berkeley Lab's
Materials Sciences Division and a
professor of electrical engineering
and computer science at the
University of California (UC) Berkeley.
"We discovered that the magnitude
of step-wise absorptance in these
materials is independent of thickness
and band structure details."
In this FTIR microspectroscopy study,
light absorption spectra are obtained
from measured transmission and
reflection spectra in which the
incident light angle is perpendicular
to the membrane. Credit: Javey group
Javey is one of two corresponding
authors of a paper describing this
research in the Proceedings of the
National Academy of Sciences ( PNAS).
The paper is titled "Quantum of
optical absorption in two-dimensional
semiconductors." Eli Yablonovitch, an
electrical engineer who also holds
joint appointments with Berkeley Lab
and UC Berkeley, is the other
corresponding author.
Previous work has shown that
graphene, a two-dimensional sheet
of carbon, has a universal value of
light absorption . Javey, Yablonovitch
and their colleagues have now found
that a similar generalized law applies
to all 2D semiconductors. This
discovery was made possible by a
unique process that Javey and his
research group developed in which
thin films of indium arsenide are
transferred onto an optically
transparent substrate, in this case
calcium fluoride.
"This provided us with ultrathin
membranes of indium arsenide, only
a few unit cells in thickness, that
absorb light on a substrate that
absorbed no light," Javey says. "We
were then able to investigate the
optical absorption properties of
membranes that ranged in thickness
from three to 19 nanometers as a
function of band structure and
thickness."
Indium arsenide is a III–V
semiconductor with electron mobility
and velocity that make it an
outstanding candidate for future
high-speed, low-power opto-
electronic devices.
Using the Fourier transform infrared
spectroscopy (FTIR) capabilities of
Beamline 1.4.3 at Berkeley Lab's
Advanced Light Source, a DOE
national user facility, Javey,
Yablonovitch and their co-authors
measured the magnitude of light
absorptance in the transition from
one electronic band to the next at
room temperature. They observed a
discrete stepwise increase at each
transition from indium arsenide
membranes with an AQ value of
approximately 1.7-percent per step.
"This absorption law appears to be
universal for all 2D semiconductor
systems," says Yablonovitch. "Our
results add to the basic
understanding of electron–photon
interactions under strong quantum
confinement and provide a unique
insight toward the use of 2D
semiconductors for novel photonic
and optoelectronic applications."
More information: http://
www.pnas.org/
content/110/29/11688.short
Provided by Lawrence Berkeley
National Laboratory

Physicists Discover Theoretical Possibility of Large, Hollow Magnetic Cage Molecules

Physicists Discover Theoretical
Possibility of Large, Hollow
Magnetic Cage Molecules
July 31, 2013 — Virginia
Commonwealth University
researchers have discovered, in
theory, the possibility of creating
large, hollow magnetic cage
molecules that could one day be used
in medicine as a drug delivery system
to non-invasively treat tumors, and in
other emerging technologies.
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Approximately 25 years ago,
scientists first made the discovery of
C 60 fullerene -- better known as the
Buckminster Fullerene -- a molecule
composed of 60 carbon molecules
that formed a hollow cage. Due to its
unique hollow cage structure the
molecule offers serious technological
potential because it could hold other
atoms or small molecules inside, and
therefore, be used in applications
such as drug delivery.
That potential has since spurred
worldwide interest among scientists
who have been searching for similar
molecules. Although some hollow
cage structures have been found,
none of them is magnetic. Magnetic
properties of the structure are of
particular interest because a hollow
magnetic structure carrying an
embedded atom or molecule can be
guided by an external magnetic field
and may serve as an effective vehicle
for targeted drug delivery.
In a new study, published online on
July 22 in The Journal of Chemical
Physics, two VCU scientists employing
state-of-the-art theoretical methods
show that magnetic hollow cages
larger than the original C60 fullerene
that carry giant magnetic moments
are possible. A magnetic moment
refers to the measure of the
magnetic strength of a cluster.
"The potential benefit of this finding
is that it provides a route to the
synthesis of molecular magnets with
colossal magnetic moments," said co-
lead investigator Puru Jena, Ph.D.,
distinguished professor of physics in
the VCU College of Humanities and
Sciences. Jena collaborated with
Menghao Wu, Ph.D., co-author of
the paper and a postdoctoral scholar
in the VCU Department of Physics.
"These molecules can be used for
targeted non-invasive drug delivery.
When assembled, the molecules can
also form new high strength magnets
for device application," Jena said.
According to Jena, the pair of VCU
researchers demonstrated the
magnetic moment of the molecule by
focusing on hetero-atomic clusters
consisting of transition metal atoms
such as cobalt (Co) and manganese
(Mn) and carbon (C) atoms. In
particular, Co 12 C 6 , Mn 12 C6 , and
Mn 24 C 18 clusters consisting of 12
cobalt and six carbon atoms, 12
manganese and six carbon atoms,
and 24 manganese and 18 carbon
atoms, respectively, carry magnetic
moments as large as 14, 38 and 70
Bohr magnetons. In comparison, the
magnetic moment of an iron (Fe)
atom in crystalline iron is 2.2 Bohr
magnetons.
According to Jena, the team is still
early in its discovery process.
"There is a long way to go.
Experiments first have to be carried
out to prove the predictions of our
theory," said Jena.
"Ways must be found to synthesize
large quantities of these molecules
and study their magnetic properties
once they are assembled. Finally,
these molecules need to be
functionalized by embedding desired
atoms/molecules for practical
applications."

Planetary 'Runaway Greenhouse' More Easily Triggered, Research Shows

Planetary 'Runaway Greenhouse'
More Easily Triggered, Research
Shows
July 30, 2013 — It might be easier
than previously thought for a planet
to overheat into the scorchingly
uninhabitable "runaway greenhouse"
stage, according to new research by
astronomers at the University of
Washington and the University of
Victoria published July 28 in the
journal Nature Geoscience.
In the runaway greenhouse stage, a
planet absorbs more solar energy
than it can give off to retain
equilibrium. As a result, the world
overheats, boiling its oceans and
filling its atmosphere with steam,
which leaves the planet glowing-hot
and forever uninhabitable, as Venus
is now.
One estimate of the inner edge of a
star's "habitable zone" is where the
runaway greenhouse process begins.
The habitable zone is that ring of
space around a star that's just right
for water to remain in liquid form on
an orbiting rocky planet's surface,
thus giving life a chance.
Revisiting this classic planetary
science scenario with new computer
modeling, the astronomers found a
lower thermal radiation threshold for
the runaway greenhouse process,
meaning that stage may be easier to
initiate than had been previously
thought.
"The habitable zone becomes much
narrower, in the sense that you can
no longer get as close to the star as
we thought before going into a
runaway greenhouse," said Tyler
Robinson, a UW astronomy
postdoctoral researcher and second
author on the paper. The lead author
is Colin Goldblatt of the University of
Victoria.
Though further research is called for,
the findings could lead to a
recalibration of where the habitable
zone begins and ends, with some
planets having their candidacy as
possible habitable worlds revoked.
"These worlds on the very edge got
'pushed in,' from our perspective --
they are now beyond the runaway
greenhouse threshold," Robinson
said.
Subsequent research, the
astronomers say, is needed in part
because their computer modeling was
done in a "single-column, clear-sky
model," or a one-dimensional
measure averaged around a planetary
sphere that does not account for the
atmospheric effect of clouds.
The findings apply to planet Earth as
well. As the sun increases in
brightness over time, Earth, too, will
move into the runaway greenhouse
stage -- but not for a billion and a
half years or so. Still, it inspired the
astronomers to write, "As the solar
constant increases with time, Earth's
future is analogous to Venus's past."
Other co-authors are Kevin J. Zahnle
of the NASA Ames Research Center in
Moffett Field, Calif.; and David Crisp
of the Jet Propulsion Laboratory in
Pasadena, Calif.

See-Through Solar Film:

See-Through Solar Film:
Researchers Double Efficiency of
Novel Solar Cell
July 29, 2013 — Nearly doubling the
efficiency of a breakthrough
photovoltaic cell they created last
year, UCLA researchers have
developed a two-layer, see-through
solar film that could be placed on
windows, sunroofs, smartphone
displays and other surfaces to harvest
energy from the sun.
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28
The new device is composed of two
thin polymer solar cells that collect
sunlight and convert it to power. It's
more efficient than previous devices,
the researchers say, because its two
cells absorb more light than single-
layer solar devices, because it uses
light from a wider portion of the
solar spectrum, and because it
incorporates a layer of novel
materials between the two cells to
reduce energy loss.
While a tandem-structure transparent
organic photovoltaic (TOPV) device
developed at UCLA in 2012 converts
about 4 percent of the energy it
receives from the sun into electric
power (its "conversion rate"), the
new tandem device -- which uses a
combination of transparent and semi-
transparent cells -- achieves a
conversion rate of 7.3 percent.
Researchers led by Yang Yang, the
Carol and Lawrence E. Tannas, Jr.,
Professor of Engineering at the UCLA
Henry Samueli School of Engineering
and Applied Science, said the new
cells could serve as a power-
generating layer on windows and
smartphone displays without
compromising users' ability to see
through the surface. The cells can be
produced so that they appear light
gray, green or brown, and so can
blend with the color and design
features of buildings and surfaces.
The research was published online
July 26 by Energy & Environmental
Science , a Royal Society of Chemistry
journal, and it will appear later in a
published edition of the journal.
"Using two solar cells with the new
interfacial materials in between
produces close to two times the
energy we originally observed," said
Yang, who is also director of the
Nano Renewable Energy Center at the
California NanoSystems Institute at
UCLA. "We anticipate this device will
offer new directions for solar cells,
including the creation of solar
windows on homes and office
buildings."
The tandem polymer solar cells are
made of a photoactive plastic. A
single-cell device absorbs only about
40 percent of the infrared light that
passes through. The tandem device --
which includes a cell composed of a
new infrared-sensitive polymer
developed by UCLA researchers --
absorbs up to 80 percent of infrared
light plus a small amount of visible
light.
Chun-Chao Chen, a graduate student
in the UCLA materials science and
engineering department who is the
paper's primary author, said using
transparent and semi-transparent
cells together increases the device's
efficiency, and that the materials
were processed at low temperatures,
making them relatively easy to
manufacture.
Other authors of the study were
Gang Li, a staff researcher in the
materials science and engineering
department at UCLA; Jing Gao, a
materials science and engineering
graduate student; and Letian Dou and
Wei-Hsuan Chang, graduate students
in the UCLA materials science and
engineering department and the
California NanoSystems Institute.
The research was funded by the Air
Force Office of Scientific Research,
the Office of Naval Research and EFL
Tech.

Tetrapod nanocrystals light the way to stronger polymers

Tetrapod nanocrystals light the
way to stronger polymers
Fluorescent tetrapod quantum dots
or tQDs (brown) serve as stress
probes that allow precise
measurement of polymer fiber
tensile strength with minimal impact
on mechanical properties. Inserts
show relaxed tQDs (upper) and
stressed tQDs (lower). Credit:
Alivisatos group
Fluorescent tetrapod nanocrystals
could light the way to the future
design of stronger polymer
nanocomposites. A team of
researchers with the U.S. Department
of Energy (DOE)'s Lawrence Berkeley
National Laboratory (Berkeley Lab)
has developed an advanced opto-
mechanical sensing technique based
on tetrapod quantum dots that
allows precise measurement of the
tensile strength of polymer fibers
with minimal impact on the fiber's
mechanical properties.
In a study led by Paul Alivisatos,
Berkeley Lab director and the Larry
and Diane Bock Professor of
Nanotechnology at the University of
California (UC) Berkeley, the research
team incorporated into polymer
fibers a population of tetrapod
quantum dots (tQDs) consisting of a
cadmium-selenide (CdSe) core and
four cadmium sulfide (CdS) arms. The
tQDs were incorporated into the
polymer fibers via electrospinning,
among today's leading techniques for
processing polymers, in which a large
electric field is applied to droplets of
polymer solution to create micro-
and nano-sized fibers. This is the
first known application of
electrospinning to tQDs.
"The electrospinning process allowed
us to put an enormous amount of
tQDs, up to 20-percent by weight,
into the fibers with minimal effects
on the polymer's bulk mechanical
properties," Alivisatos says. "The
tQDs are capable of fluorescently
monitoring not only simple uniaxial
stress, but stress relaxation and
behavior under cyclic varying loads.
Furthermore, the tQDs are elastic
and recoverable, and undergo no
permanent change in sensing ability
even upon many cycles of loading to
failure."
Alivisatos is the corresponding author
of a paper describing this research in
the journal Nano Letters titled
"Tetrapod Nanocrystals as
Fluorescent Stress Probes of
Electrospun Nanocomposites."
Coauthors were Shilpa Raja, Andrew
Olson, Kari Thorkelsson, Andrew
Luong, Lillian Hsueh, Guoqing Chang,
Bernd Gludovatz, Liwei Lin, Ting Xu
and Robert Ritchie.
Polymer nanocomposites are
polymers that contain fillers of
nanoparticles dispersed throughout
the polymer matrix. Exhibiting a wide
range of enhanced mechanical
properties, these materials have
great potential for a broad range of
biomedical and material applications.
However, rational design has been
hampered by a lack of detailed
understanding of how they respond
to stress at the micro- and
nanoscale.
"Understanding the interface between
the polymer and the nanofiller and
how stresses are transferred across
that barrier are critical in
reproducibly synthesizing
composites," Alivisatos says. "All of
the established techniques for
providing this information have
drawbacks, including altering the
molecular-level composition and
structure of the polymer and
potentially weakening mechanical
properties such as toughness. It has
therefore been of considerable
interest to develop optical
luminescent stress-sensing
nanoparticles and find a way to
embed them inside polymer fibers
with minimal impact on the
mechanical properties that are being
sensed."
From left, Andrew Olson, Shilpa Raja
and Andrew Luong are members of
Paul Alivisatos's research group who
used electrospinning to incorporate
tetrapod quantum dot stress probes
into polymer fibers. Credit: Roy
Kaltschmidt, Berkeley Lab
The Berkeley Lab researchers met
this challenge by combining
semiconductor tQDs of CdSe/CdS,
which were developed in an earlier
study by Alivisatos and his research
group, with electrospinning. The
CdSe/CdS tQDs are exceptionally
well-suited as nanoscale stress
sensors because an applied stress
will bend the arms of the tetrapods,
causing a shift in the color of their
fluorescence. The large electric field
used in electrospinning results in a
uniform dispersal of tQD aggregates
throughout the polymer matrix,
thereby minimizing the formation of
stress concentrations that would act
to degrade the mechanical properties
of the polymer. Electrospinning also
provided a much stronger bond
between the polymer fibers and the
tQDs than a previous diffusion-based
technique for using tQDs as stress
probes that was reported two years
ago by Alivisatos and his group. Much
higher concentrations of tQDs could
also be a achieved with
electrospinning rather than diffusion.
When stress was applied to the
polymer nanocomposites, elastic and
plastic regions of deformation were
easily observed as a shift in the
fluorescence of the tQDs even at low
particle concentrations. As particle
concentrations were increased, a
greater fluorescence shift per unit
strain was observed. The tQDs acted
as non-perturbing probes that tests
proved were not adversely affecting
the mechanical properties of the
polymer fibers in any significant way.
"We performed mechanical tests
using a traditional tensile testing
machine with all of our types of
polymer fibers," says Shilpa Raja, a
lead author of the Nano Letters
paper along with Andrew Olson, both
members of Alivisatos' research
group. "While the tQDs undoubtedly
change the composition of the fiber -
it is no longer pure polylactic acid
but instead a composite – we found
that the mechanical properties of the
composite and crystallinity of the
polymer phase show minimal
change."
The research team believes their tQD
probes should prove valuable for a
variety of biological, imaging and
materials engineering applications.
"A big advantage in the development
of new polymer nanocomposites
would be to use tQDs to monitor
stress build-ups prior to material
failure to see how the material was
failing before it actually broke apart,"
says co-lead author Olson. "The tQDs
could also help in the development
of new smart materials by providing
insight into why a composite either
never exhibited a desired
nanoparticle property or stopped
exhibiting it during deformation from
normal usage."
For biological applications, the tQD is
responsive to forces on the
nanoNewton scale, which is the
amount of force exerted by living
cells as they move around within the
body. A prime example of this is
metastasizing cancer cells that move
through the surrounding extracellular
matrix. Other cells that exert force
include the fibroblasts that help
repair wounds, and cardiomyocytes,
the muscle cells in the heart that
beat.
"All of these types of cells are known
to exert nanoNewton forces, but it is
very difficult to measure them," Raja
says. "We've done preliminary
studies in which we have shown that
cardiomyocytes on top of a layer of
tQDs can be induced to beat and the
tQD layer will show fluorescent shifts
in places where the cells are beating.
This could be extended to a more
biologically-relevant environment in
order to study the effects of
chemicals and drugs on the
metastasis of cancer cells."
Another exciting potential application
is the use of tQDs to make smart
polymer nanocomposites that can
sense when they have cracks or are
about to fracture and can strengthen
themselves in response.
"With our technique we are
combining two fields that are usually
separate and have never been
combined on the nanoscale, optical
sensing and polymer nanocomposite
mechanical tunability," Raja says. "As
the tetrapods are incredibly strong,
orders of magnitude stronger than
typical polymers, ultimately they can
make for stronger interfaces that can
self-report impending fracture."
Provided by Lawrence Berkeley
National Laboratory

Research helps make advance in "programmable matter" using nanocrystals

Research helps make advance in
"programmable matter" using
nanocrystals
These transmission electron
microscope images show the two
different patterns the nanocrystals
could be made to pack in.
When University of Pennsylvania
nanoscientists created beautiful, tiled
patterns with flat nanocrystals, they
were left with a mystery: why did
some sets of crystals arrange
themselves in an alternating,
herringbone style, even though it
wasn't the simplest pattern? To find
out, they turned to experts in
computer simulation at the University
of Michigan and the Massachusetts
Institute of Technology.
The result gives nanotechnology
researchers a new tool for controlling
how objects one-millionth the size of
a grain of sand arrange themselves
into useful materials, it gives a
means to discover the rules for
"programming" them into desired
configurations.
The study was led by Christopher
Murray, a professor with
appointments in the Department of
Chemistry in the School of Arts and
Sciences and the Department of
Materials Science and Engineering in
the School of Engineering and
Applied Sciences. Also on the Penn
team were Cherie Kagan, a
chemistry, MSE and electrical and
systems engineering professor, and
postdoctoral researchers Xingchen Ye,
Jun Chen and Guozhong Xing.
They collaborated with Sharon
Glotzer, a professor of chemical
engineering at Michigan, and Ju Li, a
professor of nuclear science and
engineering at MIT.
Their research was featured on the
cover of the journal Nature
Chemistry .
"The excitement in this is not in the
herringbone pattern," Murray said,
"It's about the coupling of
experiment and modeling and how
that approach lets us take on a very
hard problem."
Previous work in Murray's group has
been focused on creating
nanocrystals and arranging them into
larger crystal superstructures .
Ultimately, researchers want to
modify patches on nanoparticles in
different ways to coax them into
more complex patterns. The goal is
developing "programming matter,"
that is, a method for designing novel
materials based on the properties
needed for a particular job.
"By engineering interactions at the
nanoscale," Glotzer said, "we can
begin to assemble target structures
of great complexity and functionality
on the macroscale."
Glotzer introduced the concept of
nanoparticle "patchiness" in 2004.
Her group uses computer simulations
to understand and design the
patches.
Recently, Murray's team made
patterns with flat nanocrystals made
of heavy metals, known to chemists
as lanthanides, and fluorine atoms.
Lanthanides have valuable properties
for solar energy and medical imaging,
such as the ability to convert
between high- and low-energy light.
They started by breaking down
chemicals containing atoms of a
lanthanide metal and fluorine in a
solution, and the lanthanide and
fluorine naturally began to form
crystals. Also in the mix were chains
of carbon and hydrogen that stuck to
the sides of the crystals, stopping
their growth at sizes around 100
nanometers, or 100 millionths of a
millimeter, at the largest dimensions.
By using lanthanides with different
atomic radii, they could control the
top and bottom faces of the
hexagonal crystals to be anywhere
from much longer than the other
four sides to non-existent, resulting
in a diamond shape.
To form tiled patterns, the team
purified the nanocrystals and mixed
them with a solvent. They spread this
mixture in a thin layer over a thick
fluid, which supported the crystals
while allowing them to move. As the
solvent evaporated, the crystals had
less space available, and they began
to pack together.
The diamond shapes and the very
long hexagons lined up as expected,
the diamonds forming an argyle-style
grid and the hexagons matching up
their longest edges like a
foreshortened honeycomb. The
hexagons whose sides were all nearly
the same length should have formed
a similar squashed honeycomb
pattern, but, instead, they lined up in
an alternating herringbone style.
"Whenever we see something that
isn't taking the simplest pattern
possible, we have to ask why,"
Murray said.
They posed the question to Glotzer's
team.
"They've been world leaders in
understanding how these shapes
could work on nanometer scales, and
there aren't many groups that can
make the crystals we make," Murray
said. "It seemed natural to bring
these strengths together."
Glotzer and her group built a
computer model that could recreate
the self-assembly of the same range
of shapes that Murray had produced.
The simulations showed that if the
equilateral hexagons interacted with
one another only through their
shapes, most of the crystals formed
the foreshortened honeycomb
pattern, not the herringbone.
"That's when we said, 'Okay, there
must be something else going on. It's
not just a packing problem,'" Glotzer
said. Her team, which included
graduate student Andres Millan and
research scientist Michael Engel, then
began playing with interactions
between the edges of the particles.
They found that that if the edges that
formed the points were stickier than
the other two sides, the hexagons
would naturally arrange in the
herringbone pattern.
The teams suspected that the source
of the stickiness was those carbon
and hydrogen chains. Perhaps they
attached to the point edges more
easily, the team members thought.
Since experiment doesn't yet offer a
way to measure the number of
hydrocarbon chains on the sides of
such tiny particles, Murray asked
MIT's Ju Li to calculate how the
chains would attach to the edges at a
quantum mechanical level.
Li's group confirmed that, because of
the way that the different facets cut
across the lattice of the metal and
fluorine atoms, more hydrocarbon
chains could stick to the four edges
that led to points than the remaining
two sides. As a result, the particles
become patchy.
"Our study shows a way forward
making very subtle changes in
building block architecture and
getting a very profound change in the
larger self-assembled pattern,"
Glotzer said. "The goal is to have
knobs that you can change just a
little and get a big change in
structure, and this is one of the first
papers that shows a way forward for
how to do that."
More information: http://
www.nature.com/nchem/journal/v5/
n6/full/nchem.1651.html
Provided by University of
Pennsylvania

Researchers discover novel material for cooling of electronic devices

Researchers discover novel
material for cooling of electronic
devices
This is a schematic of thermal
management in electronics: Local
temperature increases occur as a
result of current flow in active
regions of devices and can lead to
degradation of device performance.
Materials with high thermal
conductivities are used in heat
spreading and sinking to conduct
heat from the hot regions. Credit: US
Naval Research Laboratory
A team of theoretical physicists at
the U.S. Naval Research Laboratory
(NRL) and Boston College has
identified cubic boron arsenide as a
material with an extraordinarily high
thermal conductivity and the
potential to transfer heat more
effectively from electronic devices
than diamond, the best-known
thermal conductor to date.
As microelectronic devices become
smaller, faster and more powerful,
thermal management is becoming a
critical challenge. This work provides
new insight into the nature of
thermal transport at a quantitative
level and predicts a new material,
with ultra-high thermal conductivity,
of potential interest for passive
cooling applications.
Calculating the thermal conductivity
of cubic III-V boron compounds
using a predictive first principles
approach, the team has found boron
arsenide (BAs) to have a remarkable
room temperature thermal
conductivity, greater than 2,000 Watts
per meter per degree Kelvin (>2000
Wm-1 K -1 ). This is comparable to
those in diamond and graphite, which
are the highest bulk values known.
Unlike metals, where the electrons
carry the heat, diamond and boron
arsenide are electrical insulators. For
the latter type of materials heat is
carried by vibrational waves
(phonons) of the constituent atoms,
and intrinsic resistance to heat flow
results from these waves scattering
from one another. Diamond is of
interest for cooling applications but it
is scarce and its synthetic fabrication
suffers from slow growth rates, high
costs and low quality. However, little
progress has been made to date in
identifying new high thermally
conductive materials .
Historically, fully microscopic,
parameter-free computational
materials techniques have been more
advanced for electronic properties
than for thermal transport.
"In the last few years with
contributions from the NRL team, 'ab
initio' quantitative techniques have
been developed for thermal
transport," said Dr. Thomas L.
Reinecke, physicist, Electronics
Science and Technology Division.
"These techniques open the way to a
fuller understanding of the key
physical features in thermal transport
and to the ability to predict
accurately the thermal conductivity of
new materials."
These surprising findings for boron
arsenide result from an unusual
interplay of certain of its vibrational
properties that lie outside of the
guidelines commonly used to
estimate the thermal conductivity of
electrical insulators. These features
cause scatterings between vibrational
waves to be far less likely than is
typical in a certain range of
frequencies, which in turn allows
large amounts heat to be conducted
in this frequency range. "If these
exciting results are verified by
experiment, it will open new
opportunities for passive cooling
applications with boron arsenide, and
it would demonstrate the important
role that such theoretical work can
play in providing guidance to identify
new high thermal conductivity
materials," Reinecke says.
Thermal conductivity calculations
from this group are in good
agreement with available
experimental results for a wide range
of materials. The team consisted of
Drs. Lucas Lindsay and Tom Reinecke
at NRL and Dr. David Broido at
Boston College.
This research, supported in part by
the Office of Naval Research (ONR)
and the Defense Advanced Research
Projects Agency (DAPRA), gives
important new insight into the
physics of thermal transport in
materials, and it illustrates the power
of modern computational techniques
in making quantitative predictions for
materials whose properties have yet
to be measured.
Provided by Naval Research
Laboratory

First fuel cell bus in india

Isro, Tata Motors develop India's
first fuel cell bus
PTI | Jul 28, 2013, 08.20PM IST
BANGALORE: For the first time in the
country, a Hydrogen-powered
automobile bus has been developed
by Tata Motors Limited (TML) and
Isro after several years of research.
The hydrogen fuel-fitted bus was
demonstrated at Liquid Propulsion
Systems Centre, an Isro facility in
Mahendragiri in Tamil Nadu.

It's a CNG-type bus. Hydrogen in
bottles at high pressure is stored at
the top of the bus and there would
be zero pollution.
The hydrogen cells were a spin-off of
the cryogenic technology that Isro
had been developing for the last few
years, the Bangalore-headquartered
Isro officials said.
"That's not exactly the cryogenic
technology...(It's) liquid hydrogen
handling and that's where Isro has
some expertise," they said.
Isro has a very rich technology in
producing, storing and handling
gaseous and liquid hydrogen in the
last three decades. Its expertise is
also in safety. An Isro team had
generated technical specifications for
all the elements and general
specifications for the bus.
According to honorary adviser of Isro
V Gnana Gandhi, who led the
technical team in this project, Isro
and TML entered into an MoU in 2006
to design and develop an automobile
bus using hydrogen as a fuel through
fuel cell route.

Gandhi, a Padmashree awardee and
retired scientist from Isro, and Dr M
Raja, DGM of TML made the
announcement the two organisations
have developed fuel cell bus for the
first time in India, which will run on
Hydrogen.
"This is a leap for automobile
industry for future transportation. In
this vehicle there will be zero
pollution since the product of cold
combustion is water. This is a result
of great team work of Tata Motors
and Isro specialists with contributions
from DSIR (Department of Scientific
and Industrial Research) and PESO
(Petroleum and Explosive Safety
Organisation)," Gandhi told PTI here

Molecular Monkey Arranges X-Chromosome Activation

July 26, 2013 — X chromosomes are very special genetic material. They differ in number between men and women. To achieve equality between sexes, one out of two X chromosomes in women is silenced. In flies, the opposite happens: in male flies, the only available X chromosome is highly activated, to compensate for the absence of the second X-chromosome. Researchers from the Max Planck Institute of Immunobiology and Epigenetics (MPI-IE) in Freiburg have now shown how the RNA molecules and proteins involved in the activation find and stick to each other. Similar to a monkey that grabs a liana with hands and feet, one of the proteins holds on to the RNA. Then it moulds the molecular liana with its hands and thus generates a dynamic RNA -- protein meeting place.

The protein MLE grabs the RNA strand like a monkey grabs a liana. One site serves as a simple anchor (feet), while the other is able to mould the strand. This consumes energy (banana). The moulded RNA allows other proteins to bind and thus to activate the X chromosome in male flies. (Credit: MPI of Immunobiology and Epigenetics Ibrahim Ilik, Tugce Aktas)

Just a few years ago, they were assumed to be genetic trash: DNA sequences that are not translated into proteins. But this has rapidly changed during the last years. Nowadays, it is widely known among scientists that much of the DNA is transcribed into RNA that, in turn, can act as gene regulator and structural element. Also in the regulation of sex chromosomes, RNA plays a central role. In both female humans and male flies one X chromosome is covered by a protein-RNA complex. In humans, this leads to chromosome silencing, while in flies it results in a double activation of the chromosome. Misregulation is lethal. Although known for many years, the interaction between the central proteins and the distinct role of the RNA strand was unclear.
Asifa Akhtar of the MPI-IE and her team now unravelled the function of the RNA and the interaction of the proteins. The protein MLE that is known to be a central player in X chromosome activation binds to the RNA in a very special manner. Like a monkey that grabs a liana with hands and feet, the protein grabs the RNA in two different ways. While one site is a simple anchor (the feet), the other (the hands) changes the form of the RNA. "The protein MLE moulds the RNA strand. This allows MLE to bind the RNA in a dynamic manner," says Asifa Akhtar, head of the study. Like one monkey helping the other to catch the liana MLE could thus help other proteins to grab the RNA strand. Thus, the whole X chromosome can be covered by the RNA-protein complex.
During his PhD work, first author Ibrahim Ilik investigated why MLE was found at the same places on the X chromosome but did not directly interact with other proteins. "The biochemical and the biological results seemed to point in different directions in the beginning," says Ilik. "But when we realised that the proteins bind highly specifically to certain regions of the very long RNA, this was a very exciting moment."
The researchers also found that individual mutations in the RNA hardly harm the protein-RNA binding. Only multiple mutations lead to a non-functional RNA and thus to lethality of male flies. "The system is very robust for evolutionary influences. This shows how important it is for the survival of the animals. In this, RNA could provide the necessary plasticity," says Akhtar. The scientists now want to explore the evolutionary conservation of the RNA-protein system and its equivalent in mammals.
Scientists at the Max Planck Institute of Immunobiology and Epigenetics (MPI-IE) in Freiburg investigate the development of the immune system over the course of evolution and during lifetime. They analyse genes and molecules that are important for immune cells maturation and activation. Researchers in the field of epigenetics investigate the inheritance of traits that are not caused by changes in the DNA sequence. Epigenetic research is expected to lead to a better understanding of many complex diseases, such as cancer and metabolic disorders.

The far future: tech trends of 2025

The far future: tech trends of 2025

Buckle down for the ride.
Just when you thought speech-
enabled tablets were cool. In the
future, your car won't just find a
parking spot, it will know where you
like to park. The dollar will be
replaced by not just an encrypted
currency like bitcoin, but by a
currency of knowledge and social
connection. And your home will
become a digital, customizable
expression of your tastes.
1. The currency of you
Tech pundits have predicted the age
of encrypted currency for years. And
it makes sense: you'll purchase a
piece of encrypted data like a bitcoin,
storing them in a protected digital
vault. Bitcoins could eventually
replace the digital (or paper) currency
we all use.
'Robots will protect us, cultivate
our raw food, and take care of
our health -- and look after our
parents.'
- Dmitry Grishin from Grishin
Robotics
Yet, according to security expert Tal
Klein at Bromium, the far-future
trend will shift even further.
Someday, your currency might be
tied to your own identity.
"You will be worth what you know
and can contribute," he told
FoxNews.com. "That will be
measured on an open exchange that
will remind you of your real-time
worth. It will be like a mash-up of
NASDAQ, bitcoin and LinkedIn."
2. Robots everywhere!
Robots are already popping up
everywhere -- the iRobot vacuum
cleaner, a swimming pool bot that
doesn't need any oxygen to go
underwater, or that Audi A8 that
brakes for you.
Dmitry Grishin from Grishin Robotics
says robots in the future will be even
more common than phones and
tablets today: there will be small
home bots for cooking, laundry, and
decorating. But, they'll be like the
vacuum bots, not androids you see
in movies. (Think: small and mobile
enough to move around the whole
house.)
"There will be robots in agriculture,
defense and medicine," Grishin said.
"These robots will protect us,
cultivate our raw food, and take care
of our health -- and look after our
parents."
3. Cars with an "intent engine"
The term "intent engine" is a little
hard to understand. After all, we
have nothing quite like it today. Yet,
the car of the future will know your
intentions and predict what you like.
Nick Pudar, a vice president at
OnStar, says the future car will keep
track of your day, recording where
you go and bookmarking interesting
sights. For example, you might pass
a restaurant and log (probably by
voice) that you'd like to dine there
someday. A few months later, the car
might remind you of your intent. It
might even direct you to the parking
spot you usually like, say, by a shady
oak tree.
"[The future car could offer]
geolocation bookmarking for later
serendipitous retrieval," he told
FoxNews.com. "It could track not just
where I've been but also where I
want to go."
4. Direct brain interfaces
We might not all have bald heads
and power cords stuck to our ears,
but we could be wirelessly connected
to computers at some point in the
future -- much like the Borg on "Star
Trek." (Hopefully, we won't be as
scary or bent on world conquest.)
Tom Furness, a University of
Washington engineering professor
and co-inventor of the Visualant
ChromaID, a chemical scanner, told
FoxNews.com that a direct brain
interface will mean "typing" a
document with our minds, thinking of
a command and making it happen
("turn on sprinkler system"), and
even imagining something and then
printing it on a 3D printer.
Robots will be everywhere, of course
-- and we'll have them do our
bidding without saying a word.
"Computers will communicate with
humans in the form of interactive
robots that can serve as counselors,
playmates and teachers," he said.
5. The customizable home
The connected home of today already
senses when you get home from
work and can turn on the lights or
raise the temperature to a desired
level. In the future, much like how
your car can predict what you want,
your home will be more automated
to meet your needs.
Jeremy Warren, the vice president of
innovation at Vivint , a home
automation and security company,
says home customization will change
in subtle but important ways. One
example of this: a new form of paint
might emit a soft glow and change
during the day to match your mood
or the weather conditions outside.
He says new research will show how
lighting affects us, and the home will
respond in kind.
Display technology and security
features will also evolve. We might
not have a fixed camera on a wall or
on a desk; the entire home might be
able to show information. "There will
be a paradigm shift to a display in
the home that's more flexible and
does what you want -- say, a kitchen
countertop that makes a recipe
appear as soon as you look at it.

Image of Sun-Approaching Comet ISON

Image of Sun-Approaching Comet
ISON
July 25, 2013 — The sun-approaching
Comet ISON floats against a
seemingly infinite backdrop of
numerous galaxies and a handful of
foreground stars.
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The icy visitor, with its long gossamer
tail, appears to be swimming like a
tadpole through a deep pond of
celestial wonders.
In reality, the comet is much, much
closer. The nearest star to the Sun is
over 60,000 times farther away, and
the nearest large galaxy to the Milky
Way is over thirty billion times more
distant.
These vast dimensions are lost in this
deep space Hubble exposure that
visually combines our view of the
universe from the very nearby to the
extraordinarily far away.
In this composite image, background
stars and galaxies were separately
photographed in red and yellow-
green light. Because the comet
moved between exposures relative to
the background objects, its
appearance was blurred. The blurred
comet photo was replaced with a
single, black-and-white exposure.

Evolution On the Inside Track: How Viruses in Gut Bacteria Change Over Time

Evolution On the Inside Track: How
Viruses in Gut Bacteria Change
Over Time
July 26, 2013 — Humans are far more
than merely the sum total of all the
cells that form the organs and
tissues. The digestive tract is also
home to a vast colony of bacteria of
all varieties, as well as the myriad
viruses that prey upon them.
Because the types of bacteria carried
inside the body vary from person to
person, so does this viral population,
known as the virome.
By closely following and analyzing the
virome of one individual over two-
and-a-half years, researchers from
the Perelman School of Medicine at
the University of Pennsylvania, led by
professor of Microbiology Frederic D.
Bushman, Ph.D., have uncovered
some important new insights on how
a viral population can change and
evolve -- and why the virome of one
person can vary so greatly from that
of another. The evolution and variety
of the virome can affect susceptibility
and resistance to disease among
individuals, along with variable
effectiveness of drugs.
Their work was published in the
Proceedings of the National Academy
of Sciences .
Most of the virome consists of
bacteriophages, viruses that infect
bacteria rather than directly attacking
their human hosts. However, the
changes that bacteriophages wreak
upon bacteria can also ultimately
affect humans.
"Bacterial viruses are predators on
bacteria, so they mold their
populations," says Bushman.
"Bacterial viruses also transport
genes for toxins, virulence factors
that modify the phenotype of their
bacterial host." In this way, an
innocent, benign bacterium living
inside the body can be transformed
by an invading virus into a dangerous
threat.
At 16 time points over 884 days,
Bushman and his team collected
stool samples from a healthy male
subject and extracted viral particles
using several methods. They then
isolated and analyzed DNA contigs
(contiguous sequences) using ultra-
deep genome sequencing .
"We assembled raw sequence data to
yield complete and partial genomes
and analyzed how they changed over
two and a half years," Bushman
explains. The result was the longest,
most extensive picture of the
workings of the human virome yet
obtained.
The researchers found that while
approximately 80 percent of the viral
types identified remained mostly
unchanged over the course of the
study, certain viral species changed
so substantially over time that, as
Bushman notes, "You could say we
observed speciation events."
This was particularly true in the
Microviridae group, which are
bacteriophages with single-stranded
circular DNA genomes. Several
genetic mechanisms drove the
changes, including substitution of
base chemicals; diversity-generating
retroelements, in which reverse
transcriptase enzymes introduce
mutations into the genome; and
CRISPRs (Clustered Regularly
Interspaced Short Palindromic
Repeats), in which pieces of the DNA
sequences of bacteriophages are
incorporated as spacers in the
genomes of bacteria.
Such rapid evolution of the virome
was perhaps the most surprising
finding for the research team.
Bushman notes that "different people
have quite different bacteria in their
guts, so the viral predators on those
bacteria are also different. However,
another reason people are so
different from each other in terms of
their virome, emphasized in this
paper, is that some of the viruses,
once inside a person, are changing
really fast. So some of the viral
community diversifies and becomes
unique within each individual."
Since humans acquire the bacterial
population -- and its accompanying
virome -- after birth from food and
other environmental factors, it's
logical that the microbial population
living within each of us would differ
from person to person. But this
work, say the researchers,
demonstrates that another major
explanatory factor is the constant
evolution of the virome within the
body. That fact has important
implications for the ways in which
susceptibility and resistance to
disease can differ among individuals,
as well as the effectiveness of
various drugs and other treatments.
The research was supported by
Human Microbiome Roadmap
Demonstration Project
(UH2DK083981) the Penn Genome
Frontiers Institute, and the University
of Pennsylvania Center for AIDS
Research (CFAR; P30 Al 045008).
Samuel Minot, Alexandra Bryson,
Christel Chehoud, Gary D. Wu, James
D. Lewis, all from Penn, are co-
authors.

Gadget genius

Gadget genius
Patterns of two giant surfactant
samples in thin-film state. Source:
Proceedings of the National Academy
of Sciences.
University of Akron researchers have
developed new materials that
function on a nanoscale, which could
lead to the creation of lighter
laptops, slimmer televisions and
crisper smartphone visual displays.
Known as "giant surfactants" – or
surface films and liquid solutions –
the researchers, led by Stephen Z. D.
Cheng, dean of UA's College of
Polymer Science and Polymer
Engineering, used a technique known
as nanopatterning to combine
functioning molecular nanoparticles
with polymers to build these novel
materials.
The giant surfactants developed at UA
are large, similar to macromolecules,
yet they function like molecular
surfactants on a nanoscale , Cheng
says. The outcome? Nanostructures
that guide the size of electronic
products.
Nanopatterning, or self-assembling
molecular materials, is the genius
behind the small, light and fast world
of modern-day gadgetry, and now it
has advanced one giant step thanks
to the UA researchers who say these
new materials, when integrated into
electronics, will enable the
development of ultra-lightweight,
compact and efficient devices
because of their unique structures.
During their self-assembly, molecules
form an organized lithographic
pattern on semiconductor crystals ,
for use as integrated circuits. Cheng
explains that these self-assembling
materials differ from common block
copolymers (a portion of a
macromolecule , comprising
manyunits, that has at least one
feature which is not present in the
adjacent portions) because they
organize themselves in a controllable
manner at the molecular level.
"The IT industry wants microchips
that are as small as possible so that
they can manufacture smaller and
faster devices," says Cheng, who also
serves as the R.C. Musson and
Trustees Professor of Polymer
Science at UA.
He points out that the current
technique can produce the spacing of
22 nanometers only, and cannot go
down to the 10 nanometers or less
necessary to create tiny, yet mighty,
devices. The giant surfactants,
however, can dictate smaller-scale
electronic components.
"This is exactly what we are pursuing
—self-assembling materials that
organize at smaller sizes, say, less
than 20 or even 10 nanometers,"
says Cheng, equating 20 nanometers
to 1 /4,000th the diameter of a
human hair.
An international team of experts,
including George Newkome, UA vice
president for research, dean of the
Graduate School, and professor of
Polymer Science at UA; Er-Qiang
Chen of Peking University in China;
Rong-Ming Ho of National Tsinghua
University in Taiwan; An-Chang Shi of
McMaster University in Canada; and
several doctoral and postdoctoral
researchers from Cheng's group,
have shown how well-ordered
nanostructures in various states, such
as in thin films and in solution, offer
extensive applications in
nanotechnology.
The team's study is highlighted in a
pending patent application through
the University of Akron Research
Foundation and in a recent journal
article "Giant surfactants provide a
versatile platform for sub-10-nm
nanostructure engineering" published
in Proceedings of the National
Academy of Sciences of the United
States of America.
"These results are not only of pure
scientific interest to the narrow group
of scientists, but also important to a
broad range of industry people," says
Cheng, noting that his team is testing
real-world applications in
nanopatterning technologies and
hope to see commercialization in the
future.
More information: PNAS (110,
10078-10083, 2013) http://
www.pnas.org/content/
early/2013/05/22/1302606110.abstract

Contact lenses bestow telescopic vision

Contact lenses bestow telescopic
vision
By Mark Ward
Technology correspondent, BBC News
2 July 2013 Last updated at 12:56
The lens has a telescopic element
that focuses light on to the retina
Researchers have created contact
lenses which, when paired with
special spectacles, bestow
telescopic vision on their wearers.
The contact-lens-and-spectacles
combination magnifies scene details
by 2.8 times.
Polarising filters in the spectacles
allow wearers to switch between
normal and telescopic vision.
The telescopic sight system has been
developed to help people suffering
age-related blindness.
Age-related macular degeneration is
one of the most common forms of
blindness and damages the part of
the eye, the macula, that handles
fine detail. As this area degenerates,
sufferers lose the ability to recognise
faces and perform tasks, such as
driving and reading, that rely on
picking up details.
Precise control
The contact lens created by the
researchers
has a central region that lets light
through for normal vision. The
telescopic element sits in a ring
around this central region. Tiny
aluminium mirrors scored with a
specific pattern act as a magnifier as
they bounce the light around four
times within the ring before directing
it towards the retina.
In ordinary use, the magnified image
is not seen as it is blocked by
polarising filters set in a companion
pair of spectacles. Wearers can
switch it on by changing the filters
on the spectacles so the only light
falling on their retina comes from
the magnified stream.
For their filtering system, the
researchers, led by Joseph Ford at
UC San Diego and Eric Tremblay at
Switzerland's EPFL, adapted a pair of
glasses that Samsung produces for
some of its 3D TV sets. In normal
use, these spectacles create a 3D
effect by alternately blocking the
right or left lens.
The prototype contact lens produced
by the team is 8mm in diameter,
1mm thick at its centre and 1.17mm
thick in its magnifying ring.
"The most difficult part of the project
was making the lens breathable," Dr
Tremblay told the BBC. "If you want
to wear the lens for more than 30
minutes you need to make it
breathable."
The contact lenses might find a role
on the battlefield to help soldiers
Gases have to be able to penetrate
the lens to keep the parts of the eye
covered by the contact, especially the
cornea, supplied with oxygen, he
said.
The team has solved this problem by
producing lenses riddled with tiny
channels that let oxygen flow
through.
However, said Dr Tremblay, this
made manufacturing the lenses much
more difficult.
"The fabrication tolerances are quite
challenging because everything has to
be so precise," he said.
Despite this, gas-permeable versions
of the telescopic lens are being
prepared that will be used in clinical
trials in November, he said.
Eventually it should be possible for
those with age-related sight problems
to wear the telescopic lenses all day.
The lenses are an improvement on
other ways these sight problems have
been tackled which has included
surgery to implant a telescopic lens
or wearing bulky spectacles that have
telescopic lenses forming part of the
main lens.
Clara Eaglen, eye health campaigns
manager at the RNIB said the
research looked "interesting" and
praised its focus on macular
degeneration.
"It is encouraging that innovative
products such as these telescopic
contact lenses are being developed,
especially as they aim to make the
most of a person's existing vision,"
she said. ""Anything that helps to
maximise functioning vision is very
important as this helps people with
sight loss to regain some
independence and get out and about
again, helping to reduce isolation."
The lenses may one day find their
way into other areas as the research
was being funded by Darpa, the
research arm of the US military.
"They are not so concerned about
macular degeneration," he said.
"They are concerned with super
vision which is a much harder
problem.
"That's because the standard is much
higher if you are trying to improve
vision rather than helping someone
whose eyesight has deteriorated," he
said.

Long-Distance Quantum Cryptography

Long-Distance Quantum
Cryptography
A hybrid system could secure
transmissions over hundreds
of kilometers
By Martin
LaMonica  /  August 2013
Photo: Michael Bodmann/
Getty Images
Using the quirky laws of
quantum physics to encrypt
data, in theory, assures perfect
security. But today's quantum
cryptography can secure point-
to-point connections only
about 100 kilometers apart,
greatly limiting its appeal.
Battelle Memorial Institute , an
R&D laboratory based in
Columbus, Ohio, is now
building a "quasi-quantum"
network that will break through
that limit. It combines
quantum and classical
encryption to make a network
stretching hundreds of
kilometers with security that's
a step toward the quantum
ideal.
"In a few years, our networks
aren't going to be very secure,"
says Don Hayford, senior
research leader in Battelle's
national security global
business. Cryptography relies
on issuing a secret key to
unlock the contents of an
encrypted message. One of the
long-standing worries is that
sufficiently powerful
computers, or eventually
quantum computers , could
decipher the keys. "We looked
at this and said, 'Somebody
needs to step up and do it,' "
Hayford says.
By the end of next year,
Battelle plans to have a ring-
shaped network connecting
four of its locations around
Columbus—some of which
transmit sensitive defense
contract information—that will
be protected using quantum
key distribution, or QKD. If
that smaller network is
successful, Battelle then plans
to connect to its offices in the
Washington, D.C., area—a
distance of more than 600 km
—and potentially offer QKD
security services to customers
in government or finance over
that network.
Quantum cryptography uses
physics, specifically the
quantum properties of light
particles, to secure
communications. It starts with
a laser that generates photons
and transmits them through a
fiber-optic cable. The
polarization of photons—
whether they're oscillating
horizontally or vertically, for
example—can be detected by a
receiver and read as bits,
which are used to generate the
same "one-time pad"
encryption key at both ends of
the fiber. (A one-time pad is
an encryption key that consists
of a long set of random
numbers, and so the message
it hides also appears to be a
random set of numbers.)
Messages can then be sent
securely between the sender
and receiver by any means—
even carrier pigeon—so long as
they are encrypted using the
key. If someone tries to
intercept the key by measuring
the state of the photons or by
reproducing them, the system
will be able to detect the
intrusion and the keys will be
thrown out.
Over long distances, though,
light signals fade, and keys
can't be distributed securely.
Ideally, "quantum repeaters"
would store and retransmit
photons, but such devices are
still years away, say experts.
Battelle's approach is
essentially to daisy-chain a
series of QKD nodes and use
classical encryption to bridge
the gaps. Locations less than
100 km away will be connected
by fiber-optic links and the
data secured by a QKD system
from Geneva-based ID
Quantique. For two more-
distant nodes (call them A and
C) to communicate, there must
be a "trusted node" between
them (call it B). Nodes A and B
can share a key by quantum
means. Nodes B and C can
also share a separate key by
quantum means. So for A and
C to communicate securely, A's
key must be sent to C under
the encryption that B and C
share. You might think the
quantum-to-classical stopover
in the trusted node might be a
weak point, but even inside
that node, keys are protected
using one-time pad encryption,
says Grégoire Ribordy, the CEO
and cofounder of ID
Quantique . The trusted node
will also be located at a secure
site and have other measures
to prevent tampering.
These nodes, which are still
under development, will be
designed to integrate with
corporate security systems,
distributing keys for virtual
private networks or database
security within a building. "The
idea is to set up a network
which would be dedicated to
cryptography-key
management," says Ribordy. ID
Quantique's gear will do the
quantum key exchange, while
Battelle will build the trusted
nodes.
Researchers also hope to treat
satellites in space as trusted
nodes and to send photons
through the air, rather than
over optical-fiber links. In the
nearer term, though, Battelle's
land-based QKD network may
be the most viable approach to
introducing quantum
encryption into today's
networks. Yet it still faces
significant challenges. For
starters, the cost of point-to-
point QKD is about 25 to 50
percent more than for classical
encryption, says Ribordy, and
connecting locations hundreds
of kilometers apart would
require multiple systems. That
means Battelle will need to
find a customer with an
application that warrants the
added expense. Verizon
Communications, which offers
network security services,
tested QKD from 2005 to 2006,
but it determined there wasn't
a viable business case because
of distance limitations and the
limited market for the
technology.
Also, QKD hardware can't
easily plug into the existing
telecom hardware, says
Duncan Earl, chief technology
officer of GridCom
Technologies , which plans to
use QKD for electricity grid
control networks. Established
networks have routers and
switches that would ruin the
key distribution's delicate
physics.
On a technical level, though,
the work really only requires
good engineering, not scientific
breakthroughs, says Hayford.
And the hybrid approach can
accommodate future advances
in quantum cryptography, such
as quantum repeaters. Given
the growing concerns over
cybersecurity, it's better to test
the worth of quantum
encryption sooner rather than
later, he says.