Rice University develops intelligent skins to monitor structural damage

Whether in aircraft wings, bridges or other critical structures, cracks can be catastrophic before they are large enough to be perceived by the naked eye. Monitoring cracks and strains in advance is an urgent need for various types of projects. Recently, the carbon nanotube strain sensing skin developed by Rice University in the United States can fluoresce when laser irradiation, showing the deformation of the structure.

Developed by a team led by Bruce Weisman and Satish Nagarajaiah of Rice University, this smart 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. The carbon nanotubes are microscopically rolled up graphene, that is, a single atom thick carbon atom sheet.

Like ordinary carbon nanotubes, carbon nanotubes in the skin fluoresce when exposed to laser light. The skin is subjected to different mechanical strains, and the carbon nanotubes emit fluorescence at different wavelengths. Thus, by analyzing the wavelength of the near-infrared light emitted by the nanotube, the handheld reading device can determine the amount of strain applied to any area of ​​the skin - thereby determining the amount of strain applied to the substructure of the skin. .

The research team has tested the skin on an aluminum rod. The test aluminum rod produced an invisible stress concentration at an opening, but once the sensing skin was applied, the position of the weak area of ​​the structure was visually displayed when the laser was irradiated.

In addition, the resolution of this skin corresponding variable is also very high. A typical standard strain sensor has a spatial resolution of a few millimeters, reflecting the average strain in a few millimeters, but this smart skin can show strain differences at different locations of only 1 mm apart. The researchers said that the accuracy of future strain resolution can be further reduced to the current 1/20. Currently, the research team is working to develop and improve strain reading devices and to promote the commercialization of carbon nanotube smart skins.