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Gecko's Lessons Transfer Well: Dry Printing of Nanotube Patterns to
Any Surface Could Revolutionize Microelectronics
from Science Daily
--
 Watch
a gecko walk up a wall. It defies gravity as it sticks to the
surface no matter how smooth it appears to be. What's happening
isn't magic. The gecko stays put because of the electrical
attraction -- the
van der Waals force -- between millions of
microscopic hairs on its feet and the surface.
The principle applies to new research at Rice University
reported this week in the online version of the journal
ACS Nano.
But in this case, the hairs figuratively come off the gecko and
plant themselves on the wall.
Rice graduate student
Cary Pint has come up with a way to transfer
forests of strongly aligned, single-walled carbon nanotubes (SWNTs)
from one surface to another -- any surface -- in a matter of
minutes. The template used to grow the nanotubes, with its catalyst
particles still intact, can be used repeatedly to grow more
nanotubes, almost like inking a rubber stamp.
Pint is primary author of the research paper, which also details a
way to quickly and easily determine the range of diameters in a
batch of
nanotubes grown through chemical vapor deposition (CVD). Common
spectroscopic techniques are poor at seeing tubes bigger than two
nanometers in diameter -- or most of the nanotubes in the CVD "supergrowth"
process.
"This is important since all of the properties of the nanotubes --
electrical, thermal and mechanical -- change with diameter," he
said. "The best thing is that nearly every university has an FTIR
(Fourier transform infrared) spectrometer sitting around that can do
these measurements, and that should make the process of synthesis
and application development from carbon nanotubes much more
precise."
 Pint
and other students, and colleagues of
Robert Hauge, a Rice
distinguished faculty fellow in chemistry, are also investigating
ways to take printed films of SWNTs and make them all-conducting or
all-semiconducting -- a process Hauge refers to as "Fermi-level
engineering" for its ability to manipulate electron movement at the nanoscale.
Combined, the techniques represent a huge step toward a nearly
limitless number of practical applications that include sensors,
highly efficient solar panels and electronic components.
"A big frontier for the field of
nanoscience is in finding ways to
make what we can do on the nanoscale impact our everyday
activities," Hauge said. "For the use of carbon nanotubes in devices
that can change the way we do things, a straightforward and scalable
way of patterning aligned carbon nanotubes over any surface and in
any pattern is a major advance."
Pint said an afternoon of "experimenting with creative ideas" as a
first-year graduate student turned into a project that held his
interest through his time at Rice. "I realized early on it may be
useful to transfer carbon nanotubes to other surfaces," he said.
"I started playing around with water vapor to clean up the amorphous
carbons on the nanotubes. When I pulled out a sample, I noticed the
nanotubes actually stuck to the tweezers.
"I thought to myself, 'That's really interesting ...'"
Water turns out to be the key. After growing the nanotubes, Pint
etches them with a mix of hydrogen gas and water vapor, which
weakens the chemical bonds between the tubes and the metal catalyst.
When stamped, the nanotubes lie down and adhere, via van der Waals,
to the new surface, leaving all traces of the catalyst behind.
Pint, who hopes to defend his dissertation in August, developed a
steady enough hand to deposit nanotubes on a range of surfaces --
"anything I could lay my hands on" -- in patterns that could easily
be replicated and certainly enhanced by industrial processes. A
striking example of his work is a crisscross film of nanotubes made
by stamping one set of lines onto a surface and then reusing the
catalyst to grow more tubes and stamping them again over the first
pattern at a 90-degree angle. The process took no more than 15
minutes.
"I'll be honest -- that was a little bit of luck, combined with the
skill of having done this for a few years," he said of the miniature
work of art. "But if I were in industry, I would make a machine to
do this for me."
 Pint believes industries will take a hard look at the technique,
which he said could be scaled up easily, for embedding nanotube
circuitry into electronic devices.
His own goal is to develop the process to make a range of highly
efficient sensing devices. He's also investigating doping techniques
that will take the guesswork out of growing metallic (conducting) or
semiconducting SWNTs
Polish Priest Scans
Fingerprints
for Mass Attendance
from WARSAW (Reuters) -
 A
Polish priest has installed an electronic reader in his church for
schoolchildren to leave their fingerprints in order to monitor their
attendance at mass, the
Gazeta Wyborcza
daily said on Friday.
The pupils will mark their fingerprints every time they go to church
over three years and if they attend 200 masses they will be freed
from the obligation of having to pass an exam prior to their
confirmation, the paper said.
 The pupils in the southern town of
Gryfow Slaski told the daily they
liked the idea and also the priest, Grzegorz Sowa, who invented it.
"This is comfortable. We don't have to stand in a line to get the
priest's signature (confirming our presence at the mass) in our
confirmation notebooks," said one pupil, who gave her name as
Karolina.
Poland is perhaps the most devoutly Roman Catholic country in Europe
today and churches are regularly packed on Sundays.
(Reporting by Kuba Jaworowski, editing by Paul Casciato)
The Future of
e-Books
 If
anything, all the chatter over the
Apple Tablet only amplifies the question that has been
haunting the publishing industry for a decade or more: What does the
future hold for e-books? Canada’s Quill & Quire reports on
some of the trends coming out of the industry—mostly models that
resemble the iTunes or the surge in the movie industry of
DVDs loaded with special features. Publishers such as
HarperCollins and Penguin are revamping their backlist
titles with features like web links and imbedded video and audio,
hoping to target consumers who already own print titles and lure
them to add a digital edition to get the enhanced features.
A spokesperson for Random House
of Canada says the company has “observed parallels between e-book
and music downloading habits,” and thinks that in the same way music
lovers purchase entire album collections when they discover a
favorite new artist, e-books will encourage users to nab an author’s
entire works with a single click.
Another industry insider predicts that
once e-books hit their zenith we’ll see an entirely new trend: She
envisions some consumers purchasing what she calls “disposable
reading”—titles you might buy at the airport before boarding a long
flight—in digital format, and serious works—titles you might want to
reread some day or pass along to your kids—in print editions. “In
some respects, the book will go back to being an objet,” she
hypothesizes, “[a] beautiful, expensive edition that people want to
pay for [and keep], almost the way [books were treated] in the 16th
and 17th centuries.”
Which, in the end, leaves us right back
where we started.
Source:
Quill &
Quire
Neanderthal Man and
Climate Change
from
Environmental News Network (ENN.COM) --
 The
last Neanderthals in Europe died out at least
37,000 years ago — and both climate change and interaction with
modern humans could be involved in their demise. The Neanderthal is
an extinct member of the Homo genus that is known from Pleistocene
specimens found in Europe and parts of western and central Asia.
Neanderthals are either classified as a subspecies of humans or as a
separate species. How and why they died out is a matter of debate.
Professor
João Zilhão
professor of Paleolithic Archaeology at the
University of Bristol, UK, proposed 20
years ago that, south of the Cantabro-Pyrenean
mountain chain, Neanderthals survived for
several millennia after being replaced or
assimilated by anatomically modern humans
everywhere else in Europe.
Although the reality
of this
Ebro Frontier pattern has gained wide
acceptance, two important aspects of the model
have remained the object of unresolved
controversy: the exact duration of the frontier;
and the causes underlying the eventual
disappearance of those Neanderthal populations
(ecology and climate, or competition with modern
human immigrants).
Professor Zilhão
and colleagues now report new dating evidence
for an archaeological culture unquestionably
associated with modern humans. This constrains
the age of the last Neanderthals of southern and
western Iberia to no younger than some 37,000
years ago.
 Climate
change poses the single gravest
threat to the survival of our species. This may
have been one of the causes of the demise of the
Neanderthal. Some evidence had suggested that
they had survived in what is now called Spain or
Iberia longer than other lands.
The evidence from
the Zilhao study puts at five millennia the
duration of the Iberian Neanderthal, and
counters speculations that Neanderthal
populations could have remained in the Gibraltar
area until 28,000 years ago.
Neanderthals had
many adaptations to a cold climate: short,
robust builds, and rather large noses which are
common species traits selected by evolution in
cold climates. Their cranial capacity was larger
than modern humans, indicating that their brains
may have been larger.
Professor Zilhão in
his study (Dating the
Emergence of Anatomical Modernity in Westernmost
Eurasia) states: “I believe the ” Ebro
frontier’ pattern was generated by both climatic
and demographic factors, as it coincides with a
period of globally milder climate during which
oak and pine woodlands expanded significantly
along the west façade of Iberia.
“Population
decrease and a breakup of interaction networks
probably occurred as a result of the expansion
of such tree covered landscapes, favoring the
creation and persistence of population refugia.
Then, as environments opened up again for large
herbivore herds and their hunters as a result of
the return to colder conditions, interaction and
movement across the previous boundary must have
ensued, and the last of the Neanderthals
underwent the same processes of assimilation or
replacement that underpin their demise elsewhere
in Europe five millennia earlier.”
Whatever happened
to the last Neanderthals may never be clearly
known. Climate change with its changes in
ecosystems would have had an impact.
For further information:
http://www.bristol.ac.uk/news/2010/6801.html
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