Tiny sensor could make it easier to collect ocean data

Scientists could use live fish to monitor the temperature and saltiness of the oceans thanks to a tiny new sensor.

Researchers at Southampton University have shrunk previously bulky equipment to create a highly accurate and cheap device that can be attached to a fish and collected when the creature is caught.

The sensors, which could also be attached to boats or buoys, would provide a way for oceanographers and climate scientists to take wide-scale readings of water temperature, salinity and oxygen content over time.

Because the oceans are so large and deep, it’s very difficult to collect enough data to build up a detailed picture of them at any one point in time, Southampton’s Prof Hywel Morgan told The Engineer.

‘The way it’s currently done is with very expensive remotely operated vehicles, submarines, gliders and sensors you throw off ships and then retrieve,’ he said.

‘The step change in technology would come about if we could produce miniaturised sensors that are cheap enough to be deployable en masse to gather information and then are either recovered or somehow transmit information back.’

Morgan, along with PhD student Xi Huang and Dr Matt Mowlem of National Oceanography Centre Southampton (NOCS), has developed a prototype sensor that is smaller, more accurate and cheaper to produce than existing equipment.

It can collect a range of high-precision physical, chemical and biological data needed to monitor climate change meaningfully. For example, it can measure temperature to within one 1,000th of a degree Celsius.

The device is about the size of a pen lid and combines a small battery with a solid-state sensor and a 3mm2 application-specific integrated circuit (ASIC) microchip that can take measurements every minute.

Transmitting data through water is difficult so the sensor is designed to store its data for physical collection. Fishermen could be offered money to return any tags they find on fish they catch — a model already used for sensors that track shoal movement.

Alternatively, if a version of the sensor were attached to a float that could sink and rise from the sea, it could then transmit its information when it surfaced.

‘The breakthrough we’ve achieved is to be able to measure temperature, salinity and oxygen to high accuracy on the same platform with the same electronics. That’s never been done before,’ said Morgan.

This was achieved using micro-lithography to produce the glass sensor head at Southampton’s nano-fabrication centre. The team also developed an undisclosed method of preventing organisms from growing on the device.

Other applications for the sensors include monitoring drinking water in reservoirs and boreholes for events such as chemical spillage or an increase in algae growth.

The sensor is being trialled as part of a charity expedition by a four-man team rowing from Australia to Mauritius. Further trials are needed to prove the device is stable and accurate over longer periods of time.