Nanotechnology Now







Heifer International

Wikipedia Affiliate Button


DHgate

Home > Press > Polymer opal films shed new kind of light on nature

Abstract:
New color-changing technology has potential packaging, military, aerospace applications

Polymer opal films shed new kind of light on nature

Washington, DC | Posted on July 23rd, 2007

Imagine cleaning out your refrigerator and being able to tell at a glance whether perishable food items have spoiled, because the packaging has changed its color, or being able to tell if your dollar bill is counterfeit simply by stretching it to see if it changes hue. These are just two of the promising commercial applications for a new type of flexible plastic film developed by scientists at the University of Southampton in the United Kingdom and the Deutsches Kunststoff-Institut (DKI) in Darmstadt, Germany. Combining the best of natural and manmade optical effects, their films essentially represent a new way for objects to precisely change their color. The researchers will publish their findings in the July 23 issue of Optics Express, an open-access journal of the Optical Society of America.

These "polymer opal films" belong to a class of materials known as photonic crystals. Such crystals are built of many tiny repeating units, and are usually associated with a large contrast in the components' optical properties, leading to a range of frequencies, called a "photonic bandgap," where no light can propagate in any direction. Instead, these new opal films have a small contrast in their optical properties. As with other artificial opal structures, they are also "self-assembling," in that the small constituent particles assemble themselves in a regular structure. But this self-assembly is not perfect, and though meant to be periodic, they have significant irregularities. In these materials, the interplay between the periodic order, the irregularities, and the scattering of small inclusions strongly affect the way the light travels through these films, just as in natural opal gem stones, a distant cousin of these materials. For example, light may be reflected in unexpected directions that depend on the light's wavelength.

Photonic crystals have been of interest for years for various practical applications, most notably in fiber optic telecommunications but also as a potential replacement for toxic and expensive dyes used for coloring objects, from clothes to buildings. Yet much of their commercial potential has yet to be realized because the colors in manmade films made from photonic crystals depend strongly on viewing angle. If you hold up a sheet of the opal film, Baumberg explains, "You'll only see milky white, unless you look at a light reflected in it, in which case certain colors from the light source will be preferentially reflected." In other words, change the angle, and the color changes.

These photonic crystals are apparent in the natural world as well but are more consistent in color at varying angles. Opals, butterfly wings, certain species of beetle, and peacock feathers all feature arrays of tiny holes, neatly arranged into patterns. Even though these natural structures aren't nearly as precisely ordered as the manmade versions, the colors produced are unusually strong, and depend less on the viewing angle.

Until now, scientists believed that the same effect was at work in both manmade and natural photonic crystals: the lattice structure caused the light to reflect off the surface in such a way as to produce a color that changes depending upon the angle of reflection. Baumberg, however, suspects that the natural structures selectively scatter rather than reflect the light, a result of complex interplay between the order and the irregulaty in these structures.

Given that hunch, Baumberg's team developed polymer opals to combine the precise structure of manmade photonic crystals with the robust color of natural structures. The polymer opal films are made of arrays of spheres stacked in three dimensions, rather than layers. They also contain tiny carbon nanoparticles wedged between the spheres, so light doesn't just reflect at the interfaces between the plastic spheres and the surrounding materials, it also scatters off the nanoparticles embedded between the spheres. This makes the film intensely colored, even though they are made from only transparent and black components, which are environmentally benign. Additionally, the material can be "tuned" to only scatter certain frequencies of light simply by making the spheres larger or smaller.

In collaboration with scientists at DKI in Darmstadt, Germany, Baumberg and his colleagues have developed a solution for another factor that traditionally has limited the commercial potential of photonic crystals: the ability to mass-produce them. His Darmstadt colleagues have developed a manufacturing process that can be successfully applied to photonic crystals and they now can produce very long rolls of polymer opal films.

The films are "quite stretchy," according to Baumberg, and when they stretch, they change color, since the act of stretching changes the distance between the spheres that make up the lattice structure. This, too, makes them ideal for a wide range of applications, including potential ones in food packaging, counterfeit identification and even defense.

Paper: Otto L. J. Pursiainen, Jeremy J. Baumberg, Holger Winkler, Benjamin Viel, Peter Spahn, Tilmann Ruhl, "Nanoparticle-tuned Structural Color from Polymer Opals," Optics Express, Vol. 15, Issue 15, full text available http://www.opticsexpress.org/abstract.cfm?id=139950.

For more pictures see: http://www.nano.soton.ac.uk/opal.html

####

About Optical Society of America
Uniting more than 70,000 professionals from 134 countries, the Optical Society of America (OSA) brings together the global optics community through its programs and initiatives. Since 1916 OSA has worked to advance the common interests of the field, providing educational resources to the scientists, engineers and business leaders who work in the field by promoting the science of light and the advanced technologies made possible by optics and photonics. OSA publications, events, technical groups and programs foster optics knowledge and scientific collaboration among all those with an interest in optics and photonics. For more information, visit http://www.osa.org .

About Optics Express
Optics Express, the leading optics journal, reports on new developments in all fields of optical science and technology every two weeks. The journal provides rapid publication of original, peer-reviewed papers. It is published by the Optical Society of America and edited by Martijn de Sterke of the University of Sydney. Optics Express is an open-access journal and is available at no cost to readers online at http://www.OpticsExpress.org .

For more information, please click here

Contacts:
Colleen Morrison

202-416-1437

Copyright © Optical Society of America

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

Law enforcement/Anti-Counterfeiting/Security/Loss prevention

Better sensors for medical imaging, contraband detection: Magnetic-field detector is 1,000 times more efficient than its predecessors April 6th, 2015

Optics, nanotechnology combined to create low-cost sensor for gases April 3rd, 2015

UT Dallas engineers twist nanofibers to create structures tougher than bulletproof vests March 27th, 2015

Pens filled with high-tech inks for do-it-yourself sensors March 3rd, 2015

Discoveries

Quantum model reveals surface structure of water: National Physical Laboratory, IBM and Edinburgh University have used a new quantum model to reveal the molecular structure of water's liquid surface April 20th, 2015

Happily ever after: Scientists arrange protein-nanoparticle marriage: New biotech method could lead to development of HIV vaccine, targeted cancer treatment April 20th, 2015

Nondestructive 3-D Imaging of Biological Cells with Sound April 20th, 2015

Advances in molecular electronics: Lights on -- molecule on: Researchers from Dresden and Konstanz succeed in light-controlled molecule switching April 20th, 2015

Announcements

Introduction of the LVEM25 Low Voltage Electron Microscope April 21st, 2015

Nondestructive 3-D Imaging of Biological Cells with Sound April 20th, 2015

Advances in molecular electronics: Lights on -- molecule on: Researchers from Dresden and Konstanz succeed in light-controlled molecule switching April 20th, 2015

Yale-NUS, NUS and UT Austin researchers establish theoretical framework for graphene physics: Making strides towards using graphene to create new electronic devices April 20th, 2015

Military

Engineer improves rechargeable batteries with MoS2 nano 'sandwich' April 18th, 2015

Cobalt film a clean-fuel find: Rice University discovery is efficient, robust at drawing hydrogen and oxygen from water April 15th, 2015

MIT sensor detects spoiled meat: Tiny device could be incorporated into 'smart packaging' to improve food safety April 15th, 2015

Novel nanoparticles could save soldiers' lives after explosions April 15th, 2015

Food/Agriculture/Supplements

Ethylene Nanosorbent, a Novel Product to Decrease Agricultural Waste April 20th, 2015

New Biological Nano-Fertilizers Presented in Iran as Appropriate Replacements for Chemical Fertilizers April 18th, 2015

Iranian Foodstuff, Agricultural Industries Welcome Nanotechnology Packaging Bags April 18th, 2015

Nanocomposites Play Effective Role in Production of Smart Fibers April 18th, 2015

Photonics/Optics/Lasers

Yale-NUS, NUS and UT Austin researchers establish theoretical framework for graphene physics: Making strides towards using graphene to create new electronic devices April 20th, 2015

Protein Building Blocks for Nanosystems: Scientists develop method for producing bio-based materials with new properties April 17th, 2015

Light in a spin: Researchers demonstrate angular accelerating light April 15th, 2015

Scientists create invisible objects without metamaterial cloaking April 14th, 2015

NanoNews-Digest
The latest news from around the world, FREE




  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More










ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project