Light could detect material cracks

By Lana Groves, Asst. News Editor

With just the small pieces of a silver mirror, U researchers might be able to prevent a disaster by detecting whether aircraft parts such as tails and wings are deteriorating.

Scientists have known for years that silver mirrors have multiple light-emitting properties, but when U professors John Lupton and Mike Bartl began studying beetle scales in 2007, they found that an optical microscope could reveal typically invisible structures in the material.

Although electron microscopes usually reveal a better resolution, researchers found that by using the optical microscope, they could see the internal structure of the scale, such as different light particles or if a piece is starting to wear out.

“We can reveal hidden structures you can’t see with an electron microscope,” said Lupton, a physics professor.

With the new technique, researchers said they could inject pieces of silver mirror nanoparticles into materials such as those used in airplanes to detect “fatigue.”

Lupton said that if a material becomes fatigued or begins to wear out, the emitted light would change, which could be checked by an optical microscope.

Aircraft technicians who are concerned about parts deteriorating or cracking would be able to check for safety instead of taking apart pieces of the plane.

“The possibilities are endless,” said Nick Borys, a physics graduate student who worked on the study. “Even in trace analysis, you could detect very small materials or small amounts of an explosive using these metallic (nanoparticles).”

In the past, researchers have used a laser to make a material emit light by injecting it with a fluorescent dye, but the dye can be toxic to the material and eventually damage it. The optical microscope, although more expensive, works better to show these light-generating particles.

Lupton and Bartl published a study during the summer demonstrating their initial tests using an electron microscope on photonic beetles. The investigations showed a certain beetle has a model photonic crystal scale structure.

However, U researchers found the new technique for revealing the internal structure of materials has multiple applications and have begun collaborating with other professors on campus.

“We have a project from the university to look into the commercial properties of the research,” Lupton said. They plan to apply to patent the technique within the next year.

He said they’re also beginning to collaborate with a colleague from the U School of Medicine, Balamurali Ambati, about internal structures in the eye. They might be able to use the research to better understand the spread of common degenerative diseases that affects the eye.

Lupton said the study was a good collaboration effort between his research team and Bartl’s, and they received funding from an award given by the U’s Office of the Vice President for Research.

The study was published online Feb. 5 and will go in the March 2009 issue of Nano Letters, a nanoscience journal printed by the American Chemical Society.

[email protected]

University of Utah

In this image, a tiny portion of a scale from a ?photonic beetle? is viewed using a conventional fluorescence microscope. When blue or ultraviolet laser light is aimed at the scale, most of the light is absorbed, but some is re-emitted as fluorescence. Thus, the microscope sees only the surface contour of the scale. The brightest area in the upper right is the thickest part of the shell and emits the most light.