Smartphone technology adapted into super-sensitive gravity detector

A cheap, small, mass-producible device could be used to enhance oil field yields and predict volcano eruptions

Researchers have found a way to adapt a system often found in smartphones to create a super-sensitive, portable detector capable of measuring minute changes in gravity.

Although gravimeters have been available commercially for decades, and are often used in the oil and gas industry to discover fossil fuel deposits, widespread uptake has been limited due to their expense and large size.

However, now researchers from the University of Glasgow have created a small, powerful gravimeter, called ‘Wee-g’, that uses the same cheap, mass-producible micro-electromechanical systems (MEMS) which are used in smartphones’ internal accelerometers.

Dr Giles Hammond of the University’s School of Physics and Astronomy and co-author of the paper, said that the applications for an affordable, portable gravimeter are very wide. “Areas of interest include geophysical prospecting; performing monitoring of well drainage and thus enhancing yield, monitoring magma build-up in volcanoes as a precursor to eruption,” said Hammond. “It could also be used for the creation of inertial navigation systems where GPS cannot be used or for long term monitoring of airframe health in aircraft or wind turbines.”

While the MEMS technology in phones uses relatively stiff and insensitive springs to maintain the orientation of the screen relative to the Earth, Wee-g employs a silicon spring ten times thinner than a human hair. This allows Wee-g’s 12mm-square sensor to detect very small changes in gravity.

The team used their device to measure the Earth tides from the basement of the University’s Kelvin building. Earth tides are a measurable effect of the sun and moon displacing the Earth’s crust, creating a very slight expansion and contraction of the planet around 40cm. The results aligned accurately with the variations in gravity mathematical prediction models.

Hammond told PE: “One of the factors which separates gravimeters from simple accelerometers is stability, allowing users to monitor variations in gravity over the course of several days to weeks. We have shown that a MEMS device is capable of demonstrating the long term stability necessary to measure the earth tides, changes in the local acceleration of gravity of roughly 200 parts per billion twice a day.”

Co-author Richard Middlemiss said: “Wee-g opens up the possibility of making gravity measurement a much more realistic proposition for all kinds of industries. We’re currently working to make the device smaller and more portable and via QuantIC we’re building industrial partnerships within several sectors to exploit the device commercially.”

The work is one of the first research outcomes from QuantIC, the UK’s centre of excellence for research, development and innovation in quantum enhanced imaging, which was established in 2015.