Nanotube Paint Developed to Reveal Structural Strains

L-R: Rice Professors Bruce Weisman and Satish Nagarajaiah, research scientist Sergei Bachilo and graduate student Venkata Srivishnu Vemuru; and Paul Withey, an associate professor of physics at University of Houston. (Tommy LaVergne/Rice University)

Engineers, chemists, and physicists at Rice University and University of Houston in Texas have developed a paint with carbon nanotubes and fluorescent properties that can reveal structural strains in bridges and airplanes. The Rice/Houston team describes its work online in the journal Nano Letters (paid subscription required).

The new material developed by the team led by Rice chemistry professor Bruce Weisman and engineering professor Satish Nagarajaiah can be applied as a thin coating on aircraft parts, or fixed structures such as bridges and buildings. The coating, which the Rice/Houston researchers call strain paint, uses carbon nanotubes, some 50,000 times thinner than a human hair.

When infused with a fluorescent compound, the nanotubes would experience the same strain as the surface on which it is painted. When exposed to a laser beam, any strains, even small strains, will illuminate.

Nagarajaiah believes strain paint would make it possible to provide more real time alerts about structural strains in airplanes, rather than taking an aircraft offline for testing. “They can only do this on the ground and can only measure part of a wing in specific directions and locations where the strain gauges are wired,” says Nagarajaiah. “But with our non-contact technique, they could aim the laser at any point on the wing and get a strain map along any direction.”

Strain paint can offer other benefits, adds Nagarajaiah. “It can be a protective film that impedes corrosion or could enhance the strength of the underlying material.”

Weisman lists a few more factors that the researchers need to address before strain paint is ready for the market. “We’ll need to optimize details of its composition and preparation, and find the best way to apply it to the surfaces that will be monitored,” says Weisman. “There are also subtleties about how interactions among the nanotubes, the polymeric host and the substrate affect the reproducibility and long-term stability of the spectral shifts.”

A portable optical strain reader would also need to be devised, but Weisman feels some pieces for that equipment are already available. “There are already quite compact infrared spectrometers that could be battery-operated,” Weisman notes, “Miniature lasers and optics are also readily available.”

“I’m confident that if there were a market, the readout equipment could be miniaturized and packaged.” Weisman adds. “It’s not science fiction.”

The following video tells more about the strain paint project.

• Boron Added to Carbon Nanotubes Produce Super Oil Sponge
• Nanotech Paint Devised to Monitor for Structural Damage
• Toxicity to Human Cells of Nanotubes, Nanowires Investigated
• Carbon Nanotube Material Used on NASA Jupiter Mission

*     *     *