Issue Date: July 2, 2012
Nanotube-Based Paint Measures Structural Strain
A coating made by mixing carbon nanotubes with commercial varnish could help engineers spot structural problems in buildings, bridges, and aircraft before cracks and damage start to show (Nano Lett., DOI: 10.1021/nl301008m). After applying the mixture to a structure, researchers can use a handheld infrared spectrometer to measure the strain on the structure. R. Bruce Weisman of Rice University and his colleagues stumbled upon the method after finding that when they stretched or compressed individual nanotubes, they changed the wavelengths of light that the tubes absorbed. The magnitude of this shift increased with the amount of strain put on the nanotube (Nano Lett., DOI: 10.1021/nl072861c). To exploit the phenomenon, Weisman’s team made a coating with urethane varnish and single-walled carbon nanotubes at a concentration of 0.02% by weight. To test the coating, the scientists painted it onto a piece of Plexiglas. Even with small strains from a bending jig, such as deflecting the Plexiglas from lying flat by just 0.04%, the researchers observed spectral shifts in the coating’s absorption spectra. The team could measure strain on an area as small as 100 µm across, equal to the size of the spectrometer’s beam.
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