Gravity-measuring smartphone tech might save you from a volcano

The prototype mini gravimeter, known as the Wee-g(Credit: University of Glasgow)

Although you may not use a gravimeter to detect tiny changes in gravity (or for anything else), they are commonly used in fields such as oil exploration and environmental surveying. They could have more applications, were it not for the fact that they tend to be relatively large and expensive. Scientists at the University of Glasgow have set about addressing that limitation, by creating a compact gravimeter that incorporates smartphone technology.

Called the Wee-g, the prototype device utilizes the same micro-electromechanical systems (MEMS) that are manufactured for use in phones' accelerometers.

Whereas phone systems include "relatively stiff and insensitive" springs for maintaining orientation, however, the Wee-g incorporates a silicon spring which is 10 times thinner than a human hair. Combined with a 12-mm-square sensor, that added sensitivity allows the gravimeter to pick up even the most minute changes in the Earth's gravitational field.

To test the device, the researchers placed it in a basement room in the university, then used it to measure "Earth tides" – these are slight expansions and contractions of the Earth's crust, as caused by the gravitational pull of the Sun and Moon. Readings taken over a seven-day period from the Wee-g were consistent with mathematical models, which in turn have been shown to be an accurate measure of the tides.

"There are a lot of potential industrial applications for gravimeters, but their cost and bulkiness have made them impractical in many situations," says researcher Richard Middlemiss. "Wee-g opens up the possibility of making gravity measurement a much more realistic proposition for all kinds of industries: gravity surveys for geophysical exploration could be carried out with drones instead of planes; and networks of MEMS gravimeters could be places around volcanoes to monitor the intrusion of magma that occurs before an eruption – acting as an early warning system."

The scientists are now working on making the device even smaller, and are pursuing commercialization with industry partners.

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