Checking older bridges for cracks and faults is usually something that civil engineers need to do visually. A new device, however, can make use of electrical current to locate cracks, gaps, and corroded spots before they’re visible with the eye. From ScienceDaily:
Now, civil engineers have a new device — called a sensing skin — to help find damage deep inside bridges that may be missed. “So, this skin is applied to the surface of the bridge, and essentially can self-sense whether corrosion is occurring, cracking is occurring on that bridge,” says Dr. Lynch. The skin is a thin material, lined with electrical wires. An electric current is sent through the wires. If there is any corrosion or cracking inside the bridge, it will break the electrical current.
A computer then creates a visual map of the change, which alerts inspectors exactly where damage is located. “So, essentially, if the bridge cracks the skin will crack. If the bridge is corroding, the skin will also observe that corrosion.”