Whether in aircraft wings, bridges, or other critical structures, cracks can cause catastrophic accidents before they are large enough to be detected by the naked eye. Monitoring cracks and strains in advance is an urgent need for all types of projects. Recently, a carbon nanotube strain-sensing skin developed by Rice University in the United States can fluoresce when exposed to laser light, showing the deformation of the structure.
Developed by a team led by Bruce Weisman and Satish Nagarajaiah of Rice University, this intelligent skin is actually a very thin film that is almost invisible . It consists of a bottom layer of carbon nanotubes dispersed in a polymer and a top transparent protective layer composed of different types of polymers. This carbon nanotube is a rolled up graphene in its microstructure, that is, a single-atom-thick carbon sheet.
As with ordinary carbon nanotubes, when exposed to laser light, the carbon nanotubes in the skin emit fluorescence. The skin undergoes different mechanical strains, and carbon nanotubes emit fluorescence at different wavelengths. Therefore, by analyzing the wavelength of the near-infrared light emitted by the nanotube, the handheld reader device can determine the amount of strain applied to any area of the skin-and thus the amount of strain applied to the structure under the skin.
The research team has already tested the skin on aluminum rods. The test aluminum rod produced a stress concentration that was not visible to the naked eye at an opening, but once the sensing skin was applied, the position of the weak area of the structure could be clearly and intuitively displayed during laser irradiation.
In addition, this skin has very high resolution to strain. The spatial resolution of a typical standard strain sensor is a few millimeters, which reflects the average strain in a few millimeter area, but this intelligent skin can show the difference in strain at different locations only 1 millimeter apart. According to author Weisman, the accuracy of future strain resolution can be further reduced to the current 1/20.
Currently, the research team is working on developing and improving strain reading devices and promoting the commercialization of carbon nanotube smart skins.