(July 26, 2012) Researchers trying to herd tiny particles into useful ordered formations
have found an unlikely ally: entropy, a tendency generally described as
"disorder."
Computer
simulations by University of Michigan scientists and engineers show that the
property can nudge particles to form organized structures. By analyzing the
shapes of the particles beforehand, they can even predict what kinds of
structures will form.
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The findings, published in this
week's edition of Science, help lay the ground rules for making designer
materials with wild capabilities such as shape-shifting skins to camouflage a
vehicle or optimize its aerodynamics.
Physicist and chemical
engineering professor Sharon Glotzer proposes that such materials could be
designed by working backward from the desired properties to generate a
blueprint. That design can then be realized with nanoparticles—particles a
thousand times smaller than the width of a human hair that can combine in ways
that would be impossible through ordinary chemistry alone.
One of the major challenges is
persuading the nanoparticles to create the intended structures, but recent
studies by Glotzer's group and others showed that some simple particle shapes
do so spontaneously as the particles are crowded together. The team wondered if
other particle shapes could do the same.