Nanotech paint can show stress and strain

U.S. researchers say a nano-infused "strain paint" can reveal stress in materials and holds promise for detecting strain in aircraft, bridges and buildings. Scientists at Rice University say the material made with carbon nanotubes can reveal deformations in structures by its fluorescence that could be read by a handheld infrared spectrometer, allowing in-the-field stress detection. The strain paint could tell where a material is showing signs of deformation well before the effects become visible to the naked eye, and without touching the structure, they said. That's a big advantage over conventional strain gauges, they said, which must be physically connected to their read-out devices. Nanotube fluorescence shows large, predictable wavelength shifts when the tubes are deformed by tension or compression. The nano-particle paint would suffer the same strain as the surface it's painted on and give a clear picture of what's happening underneath, researchers said. "For an airplane, technicians typically apply conventional strain gauges at specific locations on the wing and subject it to force vibration testing to see how it behaves," engineering Professor Satish Nagarajaiah said in a Rice release Thursday. "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. 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." The study was published by the American Chemical Society journal Nano Letters.