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article image25,000 invisibility cloaks created by scientists

By Abigail Prendergast     May 25, 2012 in Science
An array of invisibility cloaks have been created in order to slow down and even stop light. This technique, known as "trapping a rainbow" can be used in a variety of fields from medicine to camouflage.
A group of researchers at Towson University and the University of Maryland have created 25,000 "invisibility cloaks" capable of slowing down or even stopping light; this result is what's known as a "trapped rainbow" reports Planetsave.
But don't anticipate being able to purchase one at your local department store anytime soon. As the official press release states: "the cloaks are just 30 micrometres in diameter and are laid out together on a 25 millimetre gold sheet."
While not exactly the same type of magic invisibility cloak that would make someone disappear akin to a science fiction movie, these findings have a lot of potential in the field of observing and analyzing biological materials. Since it can slow down the speed of light, the trapped rainbow can "be utilized in tiny biosensors to identify... materials based on the amount of light they absorb and then subsequently emit, which is known as fluorescence spectroscopy. Slowed-down light has a stronger interaction with molecules than light traveling at normal speeds, so it enables a more detailed analysis."
"The benefit of a biochip array is that you have a large number of small sensors, meaning you can perform many tests at once. For example, you could test for multiple genetic conditions in a person's DNA in just one go," said Dr. Vera Smolyaninova, who was the lead author of the study. "In our array, light is stopped at the boundary of each of the cloaks, meaning we observe the trapped rainbow at the edge of each cloak. This means we could do 'spectroscopy on-a-chip' and examine fluorescence at thousands of points all in one go."
The research team's endeavor went along as follows, according to BBC News:
First, they utilized a commercially available micro-lens array, which is a grid of small lenses measuring a mere 50 millionths of a meter across.
Next, they covered the array with a thin film of gold, then proceeded to place it onto a gold-coated sheet of glass.
"Light shone in from the side, between the two, was guided around each tiny lens, creating a small cloaked region in the center of each one. The effect of having the array of the lenses was to effectively slow the light down"
In a similar effect to a prism, the light turned different hues and different colors as it was spread out across the surface. This technique of trapping a rainbow can be used in a whole variety of fields including blood analysis and biomedicine.
Professor Ortwin Hess initially predicted the trapped rainbow effect in a 2007 paper along with his colleagues. He referred to the scientific breakthrough as "encouraging and exciting."
"When coming up with that general concept of the trapped rainbow, it seemed to be a very fundamental effect and have wide application," Hess told BBC News. "So taking this forward to the experimental stage is a very nice thing to see."
The findings were published in the Institute of Physics and German Physical Society's New Journal of Physics.
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