Ordinary flour isn’t the most electrifying substance, but spilling a box of the stuff yields a jolt of voltage that has scientists excited about their prospects for sensing catastrophic events like earthquakes and industrial accidents.
Scientists have known for years that materials including rock, crystals and adhesives like ordinary office tape can produce an electrical signal as they fracture or crack under a load. It’s also known that before a granular material can flow, the space it takes up has to enlarge — think of a traffic jam in which another lane opens up and cars begin to move again. The voltage measured in the flour may be a signal of this ‘dilation,’ which indicates flow is about to happen.
“We’ve known about dilation and that there’s an electrical signal when things fail, but nobody has put these two together before,” says chemical engineer Joseph McCarthy of the University of Pittsburgh, who wasn’t involved in the work. “This is a really, really interesting observation.”