Patches coated with nanoparticles from candle soot found to generate ultrasonic waves that can be used to monitor the structural integrity of buildings.

Many industrial buildings, including nuclear power plants and chemical plants, rely on ultrasound instruments that continually monitor the structural integrity of their systems without damaging or altering their features. One new technique draws on laser technology and candle soot to generate effective ultrasonic waves for nondestructive testing and eval
Source: NDT