The future is soft. Soft robots, that is. And from a crawling caterpillar called Trevor and a wing-flapping dragonfly called Julie, Iain Anderson has his sight set on Mars – and beyond.
Ask most of us to describe a robot, and we talk about a machine with android features and a hard body. Or perhaps a factory robot, a machine that works on an assembly line building cars.
But ask Iain Anderson and Markus Henke, from the Biomimetics Lab at the University of Auckland, and they enthuse about robots made from silicon, rubber and carbon; soft, flexible robots that don’t rely on printed circuit boards or conventional electronics to control their movements.
So far the pair has created prototypes built by hand, which last just long enough to prove that the concept works - but they’re ambitious.
The key is an artificial muscle
Markus has been developing a small menagerie of robots, all of which rely on an earlier discovery made in the Biomimetics Lab, by Ben O'Brien.
As a PhD student, Ben invented the dielectric elastomer switch that can be used to turn electric charge on and off with stretch, which is part of the soft robots the lab is now developing. Ben discovered that if you put the switches together with dielectric elastomer artificial muscles that change shape when you add electric charge, you can get some interesting devices.
Ben also worked alongside fellow PhD student Todd Gisby, to develop dielectric elastomer stretchy sensors. At the end of their PhDs, Ben and Todd, along with Iain, founded StretchSense Ltd, a multi-million dollar New Zealand company, which develops smart dielectric elastomer stretch sensors that can be used to measure human movements.
Iain Anderson says that dielectric materials themselves don’t conduct electricity, but you can print a stretchable electrode on that does conduct electricity.
“Now you can do stuff with it,” says Iain. “You can put a little chargie signal on there, and you can use that to sense how much the sheet has been stretched by. This is what StretchSense is doing.”
Alternatively, if you then add lots of electrical charge rather than a little, the dielectric elastomer becomes a muscle-like device that can change its shape. It can also be used to generate power, and act as a switch.
“And then you can build these really interesting devices, using the muscles with the switches.”
Trevor the caterpillar
Markus has been using this multi-functionality in his robots.
First off the rank was Trevor the caterpillar. Trevor has a stiff skeleton made from segments of Perspex. An artificial muscle is glued onto the six segments, with three of these also containing switches.
“As soon as we feed some electricity to Trevor – which he eats through his feet – he starts moving his muscles and crawls along a track,” says Markus. It doesn’t sound much, but it’s a ground-breaking achievement.
The interesting thing, Markus adds, is that Trevor is only fed DC voltage, and “produces its oscillating movement just by using its artificial muscles and neurons.”
While Trevor’s ‘behaviour’ reflects biology – for instance, the way our central nervous system generates continuous movement in our gut without us being aware of it – Iain hastens to add “we’re not talking about nerves or neurons. We‘re just talking about stretchy bits of electrodes that turn charge on and off when they’re stretched. But put together you’ve got an autonomous system … that crawls or flaps.”
Julie the dragonfly and on into space
Julie the dragonfly had her genesis in some jibes from colleagues, who commented that Trevor was a very slow walker.
So, Markus set out to make something a little faster and more impressive. He had always thought that wings would be an interesting use for the artificial muscle.
“[When Julie] actually flapped its wings, we all got pretty excited,” he says.
It’s going to be a while before Julie the dragonfly actually takes off and flies, but this doesn’t faze Iain and Markus. They are now wrestling with making entirely soft robots, without a rigid skeleton to provide an attachment for muscles.
They’re also learning how to inject silicon and rubber through the nozzle of a 3D printer and how to accurately print thin sheets of artificial muscle. Once this is mastered, they can mass produce robots rather than building them one at a time.
In the future, the pair thinks their soft robotics could act as an interface between humans and hard robots.
‘We also think it could find some interesting uses which are literally off the planet,” says Iain.
“These extremely soft robotic devices could be scrunched up into small volumes. They won’t cost a lot of money to put into space because they’re ultra-lightweight. They could work, perhaps, as part of planetary rovers. That’s where I see a niche application for the sorts of robots we’re building.”