For decades, researchers have been devising new ways to explore the deep ocean.
And now, a team of roboticists have taken inspiration from the weird and wonderful creatures they found there
to build a new type of soft explorer.
This pliable bot gently flies untethered through the deep.
Its soft structure is designed to tackle the greatest engineering challenge
facing those who want to explore the depths – pressure.
Most deep-sea machines cope using super strong rigid materials or pressure compensation systems,
but these approaches can be bulky and heavy, and if they fail it can be catastrophic.
The researchers argue that a soft robot could be a promising alternative.
Flexible materials could shift and squish rather than break under the pressure, with a lower risk of massive failure.
Almost everything on this robot is soft. Even the motor powering the gentle flapping is a soft disc
which contracts in response to electrical impulses, sort of like an artificial muscle.
But even soft robots require controls and power onboard to operate remotely,
and without bulky protection, the electronics themselves don't always cope that well under pressure.
To solve this problem, researchers turned to evolution. In particular, the Mariana snailfish.
This soft and ghostly creature is the deepest living fish ever discovered.
CT scans revealed it has an intriguing skeletal structure.
Unlike most fish, the snailfish's skull is open and somewhat distributed throughout its head.
It's thought that this structure helps the fish cope with pressure, and that got the robot designers thinking.
They hypothesised that distributing the vulnerable electronics could also decrease the stress on each part.
The team modelled the impacts of separating the battery and part of the control architecture,
and it seemed that this could indeed reduce the stress on the interfaces between the components.
The next step was to build and test it.
The robot performed well in a pressurised chamber in the lab, first swimming in a circle and then free swimming.
To get a sense of how much pressure the chamber is under, look at the green foam cylinder.
At atmospheric pressures, it is 6 centimetres across,
but at pressures mimicking the deep ocean it's crushed to less than 1.5 centimetres.
The lab experiments were promising, but the real test would come when they took it out into the wild.
First, a lake, where it took its first swims in open water, performing well down to about 70 metres.
Next, they used a conventional remote-operated vehicle to take the bot more than 3 kilometres down in the South China Sea, and it kept on swimming.
But to really put it through its paces, they needed to travel to the deepest place on the planet – the Mariana Trench.
The robot was mounted on a deep-sea lander and dropped to a depth of almost 11 kilometres.
The pressure down here is the equivalent of a human holding 50 jumbo jets on their back.
Although it wasn't allowed to swim freely here, the little bot flapped away for 45 minutes, functioning perfectly despite the crushing pressures.
Now, as it stands, the robot is slow, simple and not especially manoeuvrable.
But the researchers see it as a proof of principle.
They say that you could add other distributed electronics, like sensors which could make the robot smarter,
and new designs could make it more powerful or versatile.
Time will tell. But who knows, maybe the future of hardened deep-sea exploration will be, well, soft.