Deep-sea robots set to make waves

The Straits Times AsiaOne 31 Mar 15;

The stingray glides gently through the water, propelled by flexible wings. But much as it looks like the real thing, this prototype is actually a $1,000 robot developed to collect data on the surroundings, including water temperature, salinity and dissolved oxygen.

Our waters could soon be monitored by such stingrays, and other fleets of robots that roam the sky and sea, to study climate change better or help prevent the deadly algae blooms which have been plaguing local fish farmers.

The idea is to provide constant surveillance of the seas at low cost, using little energy.

The stingrays, for instance, could be equipped with sensors and deployed in large numbers to help detect harmful algae blooms and measure their chemistry. Getting such data would help scientists to better understand the deadly blooms and find ways to mitigate their effects.

"That is better because instead of having information once a month for a couple of hours, you can have a constant data stream over a period of time," says Dr Pablo Valdivia y Alvarado, the lead researcher behind the stingray.

The stingray's ability to move in a wave-like motion also causes less disturbance in the water.

"We hope to understand the environment as it is, so the less disturbance we inflict while measuring the water, the better," he explains.

Data about the oceans is usually gathered by satellites, buoys and research ships, but such methods can be expensive. So countries around the world are experimenting with drones, which can work around the clock - and cheaply - to provide information on marine life.

The Singapore-MIT Alliance for Research and Technology (Smart), which is developing the robots, recently came up with one inspired by the octopus and its jet propulsion swimming technique.

Made from a strong polycarbonate skeleton covered by a thin elastic membrane, the 27cm-long robot fills with water and shoots it out to propel itself.

It can travel at up to 2.7 metres per second (10kmh) with minimum energy and turbulence.

Professor Michael Triantafyllou, a principal investigator at Smart's Centre for Environmental Sensing and Modeling, led the research.

When studying plankton blooms, he notes, it is important that marine robots can move quickly in water.

"The plankton can move swiftly with the currents at sea. That's why we want to invent robots that can move faster so they can follow the algae blooms."

The speed and movement of the stingray and octopus could be incorporated into existing underwater vehicles and kayaks in two years, he believes.

"We know now the laws of physics to go about doing it."

He estimates that it will be five more years before these vehicles can go out into the ocean.

Understanding the science behind algae blooms has become particularly important.

While some of them produce toxins that can kill, others discolour water, foul beaches, or cause drinking water and fish to taste bad.
Yet others clog the gills of fish or smother corals and vegetation.

Such blooms, which are difficult to predict and can explode at any time, have wiped out fish stocks in Singapore several times in recent years. This includes a particularly serious hit last month, which wiped out more than 500 tonnes of fish in farms off Changi and Lim Chu Kang.

Singapore's Tropical Marine Science Institute has used Smart's robots to collect data on harmful algae blooms, and is working with the Agri-Food and Veterinary Authority of Singapore on another study to understand plankton blooms.

The octopus robot is so fast it can also be used to follow dolphins for quick observation, or even inspect thermal vents safely in the mid-ocean ridges, says Prof Triantafyllou.

A research engineer at the environmental centre, Mr Vignesh Subramaniam, says: "Currently, no autonomous underwater vehicle (AUV) can achieve this ultra-fast performance except for torpedoes which require a lot of fuel... Future AUVs and other marine vehicles can adopt this mechanism to help them evade threats or track something fast and stealthily underwater without the need for much energy."