Turning metal black more than just a novelty

December 8, 2009

(PhysOrg.com) -- University of Rochester optics professor Chunlei Guo made headlines in the past couple of years when he changed the color of everyday metals by scouring their surfaces with precise, high-intensity laser bursts.

Suddenly it was possible to make sheets of golden tungsten, or black aluminum.

A recent discovery in Guo's lab has shown that, beyond the aesthetic opportunities in his find lie some very powerful potential uses, like diagnosing some diseases with unprecedented ease and precision.

Along with his research assistant, Anatoliy Vorobyev, Guo has discovered that the altered metals can detect electromagnetic radiation with frequencies in the range (also known as T-rays), which have been challenging, if not impossible, to detect prior to his discovery.

"When we turned metals black, we knew that they became highly absorptive in the visible because the altered metals appear pitch black to the eye. Here, we experimentally demonstrated that the enhanced absorption extends well into the far infrared and terahertz frequencies," Guo said.

With wavelengths shorter than microwaves, but longer than infrared rays, T-rays occupy a place in the that is capable of exciting rotational and vibrational states of , like pathogens. This quality could allow doctors and biomedical researchers to get previously impossible glimpses of diseases on the molecular level.

In addition, unlike X-rays, T-rays are non-ionizing, which means that people who are exposed to them don't risk the possible tissue damage that can result from X-rays.

University of California, Berkeley, bioengineering Professor Thomas Budinger says terahertz radiation is like much-higher-frequency radar, except that it theoretically can allow its users to see intricate details of tissue architecture, on the scale of one-thousandth of a millimeter and smaller, instead of large objects like airplanes and boats.

"Terahertz has the capability to interrogate tissues at the cellular level. If applied within microns of the subject of interest, this form of imaging has the theoretical capability to detect properties of molecular assemblages that could be attributes of disease states," Budinger said.

What made terahertz radiation so difficult to detect in the past was that typical materials do not readily absorb that frequency. However, after undergoing Guo's femtosecond structuring technique, metals become over 30 times more absorptive.

The key to creating the black metal in terahertz is a beam of ultra-brief, ultra-intense pulses called femtosecond laser pulses. The laser burst lasts less than a quadrillionth of a second. To get a grasp of that kind of speed, consider that a femtosecond is to a second what a second is to about 32 million years. During its brief burst, Guo's laser unleashes as much power as the entire grid of North America onto a spot the size of a needle point. That intense blast forces the surface of the metal to undergo some dramatic changes and makes them extremely efficient in absorbing terahertz radiation.

Source: University of Rochester (news : web)

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1 / 5 (1) Dec 08, 2009
coupling these metals to polymers should yield the next generation of radiovoltaic resonance panels for power sequestration
5 / 5 (3) Dec 08, 2009
terahertz radiation is like much-higher-frequency radar, except that it theoretically can allow its users to see intricate details of tissue architecture, on the scale of one-thousandth of a millimeter and smaller, instead of large objects like airplanes and boats.

Move over MRI, hello TSI (Terahertz Scanning Imager)? Would it be possible to focus enough Terahertz radiation on a narrow spot in the body, to heat it up sufficiently as to destroy a tumor, for instance? Hm, suddenly the image of a doctor passing a "tricorder" over a patient's body so as to obtain a detailed image of the patient's internal organs isn't such Star Trek science fiction any longer -- it's getting eerily close to reality....
5 / 5 (1) Dec 08, 2009
Terahertz radiation also damages DNA, according to another report. http://arxiv.org/abs/0910.5294
5 / 5 (1) Dec 09, 2009
( @dirk_bruere: The study only said that some specific frequencies seem to damage DNA, most others not.)

Tricoders, indeed. I always thought it'd be beyond my lifetime before we'd see such devices. Now it suddenly looks very reachable!

Imagine a handheld device that, with a single sweep, gets you a 3D scan in several frequencies with a preliminary report, and plugged to a laptop a full analysis of internal organs or the site of trauma. What a boon for paramedics! Or doctors in developing countries. A device like this could be cheap, too, in quantities.
not rated yet Dec 09, 2009
The greater question it ask the self, is the molecular and temporal, energetic, etc, specifics of ~why~ Terahertz waves are more efficacious for the given applications, in the first place. This will lead to far more significant discoveries than checking for 'terrywrists' at airports.

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