Nanoclusters Battle Second Law
Author(s): Laura Sanders
Source: Science News, Vol. 175, No. 10 (May 9, 2009), p. 13
Published by: Society for Science & the Public
Stable URL: http://www.jstor.org/stable/27652724 .
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Numberof transistors
that would
4
billion
light-sensitive
monomer
the new
made
approach possible. The scientists added
two ingredients: an initiator that reacts
with blue light and an inhibitor that
reactswith UV light.
When the scientists
project the blue light through the lens
onto themonomer, the liquid absorbs
the lightand releases radicals hungry to
bond. And bond theydo, creating a solid
polymerwherever the blue lighthits.
The UV light then acts as the eraser,
the team reports.Around the pinpoint of
blue light,the scientists created a dough
produces
up other
radicals,
radicals,
these
but
preventing
report
a similar
approach:
An
activating
laser beam gets polymerization going,
and a de-activating beam keeps the
contained.
polymerization
Sculpting with lightmay allow these
researchers to craft tiny gears for tiny
machines or finelydetailed screens for
controllingwhere lighthits amaterial.
In a thirdpaper, Rajesh Menon ofMIT
snatch
polymeriza
tion. So a fine line is created by sweeping
theperipherywith UV light.
John Fourkas of the University of
and his colleagues describe a technique
that also uses two differentwavelengths
of light.But the researchers blocked light
instead of erasing it.
The team placed light-sensitive film
over thematerial to be patterned. Upon
exposure toUV light,the film becomes
transparent, allowing the scientists to
"cut" awindow wherever desired. Light of
anotherwavelength can be shone through
Nobody's above the law.But tinyclusters
of colliding atoms may duck below the
second law of thermodynamics. In simu
lations, researchers in Japan found that
in rare cases,
tiny clusters
of atoms
rico
chet offeach other faster than their
^^^^^.
Lu
approaching speeds. The results,^^^Hb
LU
S..
-jc
enI
the ball's energy is siphoned as heat.
In thenanoworld, though,normal rules
do not always apply the results suggest.
Researchers Hisao Hayakawa ofKyoto
University andHiroto Kuninaka ofChuo
University inTokyo developedacomputer
program tomodel head-on collisions of
?squishycollections of several hun
dred
ReviewE,
intheMarchPhysical
^^^^^^^H
seemtoviolatethesecondlaw's
^^^^^^^^H
requirementthat anywork j^^^^^Br
withhigherentropy.
system
^^^^^^^K
In collisionsbig enoughto
^^^^^^^M
see,likethosebetweena tennis^^^^^^^^p
ball and a gym floor, the speed
L.,
of an
object's
approach
is
always faster than its speed
after impact.Aball dropped
against the floor bounces a
little slower and comes up
shorter
because
on
each
a small
bounce
amount
of
_:_
tBMP^
Nanoclusters
called
moved
away
at a slower
rate
than
i their approach.
\ But about 5 percent of the time,
the colliding nanoclusters sped
_
some
times gained speed
after colliding insim
ulations, seeming to
defy the second law
of thermodynamics.
up
after
bumping,
iting what
ers call
exhib
the research
a super
show
thinner
rebound.
In
these rebounds, theoutgoing
energy exceeded the incom
ingenergy,meaning that the
system overall lost entropy,
rings are
pos
the stencil to etch thematerial beneath.
The
tionize
aren't
studies
to revolu
likely
the semiconductor
industry,
says
Robert Allen, also of IBM. But "what they
have done with very longwavelengths of
light is spectacular."?
violation
of the second
itwas
also
observation.
law.
Forme,
comments
counterintuitive,"
J?rnDunkel, a theoretical physicist at the
University ofOxford inEngland.
This superbounce comes from the
random fluctuations ofmotions of the
atoms
that make
up
the researchers
exact
each
nanocluster,
on
say. Depending
some fluctuations
motions,
the
can
give the collision an extra boost, like an
extra springy trampoline.
"Nanoscale
nanoclusters.
[ At speeds around 5 meters per
r second,most of the clusters in the
1
simulationstucktogetherliketwo
candied apples in the sun.Others
just bumped into each other and
squanders a littlebit of energy in ^jJ^KF
the formofwaste heat, leaving a
?fl|H|^^
Q..
iI-:
atoms
studies
sible with a two-laser approach (right).
Othermethods yield bulkier rings (left).
"Ifs an interesting
Insimulations,collisionscan increasevelocity,reduceentropy
By Laura Sanders
New
an apparent
law
battle second
Nanoclusters
today
Maryland inCollege Park and colleagues
nut ofUV light,stimulating the chemical
inhibitor in themonomer. This process
also
fiton a
stamp
postage
physics
events,"
unexpected
involves such
Hayakawa
says.
But this extra boost works only in tiny
the researchers
systems. When
increased
the size of each nanocluster in the sim
ulation
to over
1,000
atoms,
the
super
bounce disappeared entirely."In order to
see a violation
a very
small
of the second
number,"
Dunkel
law, you need
says.
These clusters evade the second law
on a statistical technicality:The average
speed of all the outgoing nanoclusters is
less than the approaching speed. Even
though individual nanoclusters appear to
violate the second law occasionally, the
average behavior of all the nanoclusters
falls in linewith the law's constraints.@
www.sciencenews.org
May 9, 2009
I SCIENCE
NEWS
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