. Nano Technology News .




.
NANO TECH
Entropy can lead to order, paving the route to nanostructures
by Staff Writers
Ann Arbor MI (SPX) Jul 30, 2012

File image.

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.

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.

"We studied 145 different shapes, and that gave us more data than anyone has ever had on these types of potential crystal-formers," Glotzer SAID. "With so much information, we could begin to see just how many structures are possible from particle shape alone, and look for trends."

Using computer code written by chemical engineering research investigator Michael Engel, applied physics graduate student Pablo Damasceno ran thousands of virtual experiments, exploring how each shape behaved under different levels of crowding. The program could handle any polyhedral shape, such as dice with any number of sides.

Left to their own devices, drifting particles find the arrangements with the highest entropy. That arrangement matches the idea that entropy is a disorder if the particles have enough space: they disperse, pointed in random directions. But crowded tightly, the particles began forming crystal structures like atoms do-even though they couldn't make bonds. These ordered crystals had to be the high-entropy arrangements, too.

Glotzer explains that this isn't really disorder creating order-entropy needs its image updated. Instead, she describes it as a measure of possibilities. If you could turn off gravity and empty a bag full of dice into a jar, the floating dice would point every which way.

However, if you keep adding dice, eventually space becomes so limited that the dice have more options to align face-to-face. The same thing happens to the nanoparticles, which are so small that they feel entropy's influence more strongly than gravity's.

"It's all about options. In this case, ordered arrangements produce the most possibilities, the most options. It's counterintuitive, to be sure," Glotzer said.

The simulation results showed that nearly 70 percent of the shapes tested produced crystal-like structures under entropy alone. But the shocker was how complicated some of these structures were, with up to 52 particles involved in the pattern that repeated throughout the crystal.

"That's an extraordinarily complex crystal structure even for atoms to form, let alone particles that can't chemically bond," Glotzer said.

The particle shapes produced three crystal types: regular crystals like salt, liquid crystals as found in some flat-screen TVs and plastic crystals in which particles can spin in place. By analyzing the shape of the particle and how groups of them behave before they crystallize, Damasceno said that it is possible to predict which type of crystal the particles would make.

"The geometry of the particles themselves holds the secret for their assembly behavior," he said.

Why the other 30 percent never formed crystal structures, remaining as disordered glasses, is a mystery.

"These may still want to form crystals but got stuck. What's neat is that for any particle that gets stuck, we had other, awfully similar shapes forming crystals," Glotzer said.

In addition to finding out more about how to coax nanoparticles into structures, her team will also try to discover why some shapes resist order.

This research was supported by the U.S. departments of Defense and Energy, the Deutsche Forschungsgemeinschaft and the National Science Foundation. The paper is titled "Predictive Self-Assembly of Polyhedra into Complex Structures." Glotzer is the Stuart W. Churchill Collegiate Professor of Chemical Engineering and a professor of chemical engineering, materials science and engineering, macromolecular science and engineering, and physics in College of Literature, Science, and the Arts.

Related Links
University of Michigan
Nano Technology News From SpaceMart.com
Computer Chip Architecture, Technology and Manufacture




.
.
Get Our Free Newsletters Via Email
...
Buy Advertising Editorial Enquiries




.

. Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle



NANO TECH
Silver nanoparticle synthesis using strawberry tree leaf
Madrid, Spain (SPX) Jul 17, 2012
A team of researchers from Greece and Spain have managed to synthesize silver nanoparticles, which are of great interest thanks to their application in biotechnology, by using strawberry tree leaf extract. The new technology is ecological, simple, cheap and very fast. Strawberry tree leaf (Arbutus unedo) and silver nitrate (AgNO3). With just these two ingredients scientists can now produce ... read more


NANO TECH
Hackers could haunt global air traffic control: researcher

Clemson researchers transform machine to make runways safer

Singapore Airlines first quarter net profit up 73%

EU should scrap airline emissions tax: IATA

NANO TECH
China's manned spacecraft in final preparations for mid-June launch

Looking Forward to Shenzhou 10

Argentina, China ink space cooperation deal

Looking Forward to Shenzhou 10

NANO TECH
Cybersecurity law at risk of watering down

Control-Alt-Hack game lets players try their hand at computer security

Finnish firm says new cyber attack may have targeted Iran

Computer hackers and defenders mix in Las Vegas

NANO TECH
Hunter-gatherers, Westerners use same amount of energy, contrary to theory

BSU starts second phase of largest geothermal system in U.S.

Roadmap for a Sustainable Energy System in the Dominican Republic

Apollo Energy Assists Businesses Cutting Commercial Energy Costs

NANO TECH
China appoints officers to South China Sea garrison

Chevron damages bill in Ecuador rises to $19 bn

South China Sea: a decades-long source of tension

Pipeline grid to bypass Hormuz vulnerable

NANO TECH
Boeing F-15E Radar Modernization Program Begins Second Low Rate Initial Production Phase

Northrop Grumman Awarded contract for Continuing BACN Mission Support

Northrop Grumman Delivers First B-1 Radar Modification Kit

12 die in Brunei helicopter crash

NANO TECH
A new era in modern analytical chemistry with Nano-FTIR

Entropy can lead to order, paving the route to nanostructures

Researchers Create Highly Conductive and Elastic Conductors Using Silver Nanowires

Silver nanoparticle synthesis using strawberry tree leaf

NANO TECH
NRL Brings Inertia of Space to Robotics Research

Clemson researcher: humanizing computer aids affects trust, dependence

Autonomous robot maps ship hulls for mines

Can robots improve patient care in the ICU?


Memory Foam Mattress Review

Newsletters :: SpaceDaily Express :: SpaceWar Express :: TerraDaily Express :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News

.

The content herein, unless otherwise known to be public domain, are Copyright 1995-2012 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement