In the wake of an earthquake, you need information about the structural integrity of buildings in the quake zone in order to determine if it’s safe to enter them. For this reason, buildings in earthquake-prone regions often have sensors attached to measure strain on the structure. There’s one problem though: what if the quake damages the sensor itself? The building might have severe structural damage, or it might not–with the sensor down, you just can’t be sure.
To help counter this known unknown, researchers at North Carolina State University have developed a structural sensor that’s able to heal itself when damaged. The sensor is made up of a pair of glass optical fibers embedded in a reservoir of liquid resin. This resin, though, has special properties–it is “ultraviolet-curable” resin, which means that when it comes into contact with UV light, it hardens. If the filament connecting the two glass fibers should snap during an earthquake, a beam of UV light will carve a new connection out of the reservoir of liquid resin. It is, in essence, “a sensor that automatically repairs itself,” in the words of Kara Peters, one of the researchers. “As far as I’m aware,” she tells Technology Review, “this is the first time” a self-healing sensor has been made.
The NCSU team, which received funding form the National Science Foundation for their research, tested the sensor’s abilities before and after failure, and found that it still worked well. Sometimes, though, as they note in their paper published recently in Smart Materials and Structures, the repaired filament didn’t always go exactly where it was supposed to, failing to bridge the gap between the two optical fibers. “In order to produce reliable self-repairing sensors,” they write, “the alignment and bending problems will need to be addressed.”
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