August 1, 2012

Nanotechnology not just science fiction

Construction Corner | Korky Koroluk

The advances in nanotechnology continue to grow, with new use piled upon new use until it's easy to think they are something out of science fiction.

After all, researchers are manipulating carbon nanotubes, each about 50,000 times thinner than a human hair, something we ordinary folk can scarcely imagine. And, the way the tubes behave under stress can tell us a lot about problems that may arise in the future of a building, a bridge, even an airplane. That sure sounds like science fiction, but it isn’t.

A few months ago, I wrote about work being done at the University of Strathclyde, in Scotland, where researchers have developed a paint containing carbon nanotubes that can spot microscopic faults in structures. But, the system relies on the ability of the paint to carry an electrical current, which means a power source of some sort and a data logger to record the development of these minuscule faults.

That suggests a possible use where visual inspection is difficult.

Now scientists at Rice University in Houston, Texas, have come up with what they call “strain paint,” which is a high-tech version of the strain gauges that have been in common use for decades.

They’re capable of spotting cracks long before they can be spotted during a visual inspection.

The strain paint, which looks like clear varnish, has one important similarity to the paint developed at Strathclyde: Both use carbon nanotubes. But, the paint being developed at Rice uses them because they display fluorescence at the infrared end of the spectrum.

That fluorescence shows large and predicable wavelength shifts when the nanotubes are deformed by tension or compression. The paint — and therefore each nanotube — would suffer the same strain as the surface it’s painted on and give a clear picture of what’s happening underneath.

The fluorescence also means the paint can be “read” using a handheld infrared spectrometer.

For greater distances — along an airplane wing, for example, or up a wind turbine mast — a laser could be used to “read” the paint and produce a strain map.

Conventional strain gauges can’t provide a complete map because they are typically installed only at a few key points on a structure. The strain paint can measure strain at any location that has been “painted.”

One of the researchers involved in the project, Satish Nagarahaiah, said the strain paint could also be customized with properties for specific applications. For example, he suggests that it could be used as a protective film to prevent corrosion of the underlying material.

Another researcher, Bruce Weisman, said there is still work to be done before there can be any attempt to market the strain paint. Details of its composition have to be ironed out, and the best way to apply it has yet to be found, but these are simply engineering problems, he said, and don’t seem insurmountable.

Developing the handheld strain reader should be relatively straightforward, he said.

“There are already quite compact infrared spectrometers that could be battery-operated,” he said.

“Miniature lasers and optics are also readily available. So it wouldn’t require the invention of new technologies, just combining components that already exist. So, the readout equipment could be miniaturized and packaged. It’s not science fiction.”

And because it’s not science fiction, we can expect to hear a lot more about nanomaterials that are of use to the construction industry. They have the potential to do things we couldn’t have dreamed of even a decade ago. And that potential extends to things we still haven’t dreamed of.

That’s why public and private research organizations are spending more than $4.5 billion a year worldwide, looking for ways to tap that promise as sustainability in construction becomes more and more important.

Korky Koroluk is a regular freelance contributor to the Journal of Commerce. Send comments or questions to editor@journalofcommerce.com.

Print | Comment