Crime Alert! Molding Fingerprints

Reported January 2007

TORONTO (Ivanhoe Broadcast News) -- Increased airport security ... Better police forensics work ... Even improved bridge and building safety. These are all the tremendous possibilities stemming from a new material that's 20-times thinner than a strand of human hair.

Imagine a security system that relied on something unique to every single person -- his fingerprint. Now, scientists have developed a material that makes those prints nearly impossible to forge.

At the University of Toronto inside a science lab, Materials Chemist Andre Arsenault starts from scratch making new crystals. The raw materials are a lot like opal gemstones, which reflect light.

"Opal gemstone is very nice because you get all these multi-faceted color effects," Arsenault tells Ivanhoe.

But these crystals are microscopic. Inside a flask, they form millions of tiny silica circles. Chemists fill the spaces with a synthetic rubber and then dissolve the silica, leaving behind a thin, honeycomb-like structure called a photonic crystal. When you press on it, the holes get closer together, changing the wavelength of light that's reflected.

"As you start pressing, you're gonna gradually go through the rainbow toward the blue. So you're gonna go red, orange, yellow, green, blue, purple," Arsenault says.

With a traditional ink fingerprint, the only thing that can be seen is the ridges on the finger. Full-color prints provide so much more. "You can get information about the depth of the ridges on the people's fingers," Arsenault says. "You can get information about the shape of people's fingers, as well as even the mechanical properties of the skin."

He even made a rubber replica of his fingerprint, which might fool a traditional fingerprint scan. The new material picked up the fake.

Researchers say the photonic crystal material is inexpensive to make and could be used to improve sensors in a number of consumer products.

Click here to Go Inside This Science or contact:

Andre Arsenault
Ph.D. Student
Department of Chemistry
University of Toronto
Toronto, Canada
(416) 978-4735
(416) 978-1018
aarsenau@chem.utoronto.ca

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