Now, imagine a so-called 'skin' for buildings and other structures that reveals the health of the underlying structure and materials beneath. University of Michigan researchers have developed just that, a coating that senses changes in structures such as aircraft, bridges and buildings.

This technology has tremendous potential in that it is a true distributed sensing technology, which was previously not available for monitoring damage to structures. Prior to this, in order detect and diagnose structural problems, a large number of discrete sensors would have been required. Those sensors would be placed throughout the building, which is both costly and difficult to install and maintain.

With the U-M technology, such monitoring can be accomplished by applying one skin to the surface of a structure. The skin is actually an easy to apply carbon nanotube composite material that is electrically stimulated. When applied to a structure, the skin provides a clear and accurate picture of cracks, strains, or corrosion beneath, said Jerome Lynch, assistant professor in the College of Engineering at U-M and lead author of a paper on the research. Their approach includes the use of electrical impedance tomography (EIT) to directly measure the distribution of the carbon nanotube composite's bulk conductivity. As a multifunctional material whose conductivity changes in response to external stimulus (e.g. strain, pH), EIT facilitates spatial mapping of the stimulus and a measure of its magnitude. The work was done in conjunction with U-M associate professor of engineering Nick Kotov, and Nadine Wong Shi Kam, a Michigan Society Fellow in Kotov's lab.