'Big Hero 6': The Science Behind Baymax, Disney's Big, Soft Robot

In "Big Hero 6," the latest 3-D animated film from Disney, the titular hero is a robot — but not the hard, metal kind most people associate with the word. It's a soft robot, a sort of vaguely human-shaped bag of gas. Sound far-fetched? Turns out there's more than a little science at work here.

The whole idea of Baymax, the caretaker robot in the movie, in fact, occurred to co-director Don Hall during a visit to Carnegie Mellon University's Robotics Institute, where you can find everything from snake-bots to crocodile-bots to bot swarms — to the inflatable robotic arm that inspired Hall.

"It really became apparent when we saw the soft robotics that that would be our ticket to putting a robot on the screen we had never seen before," Hall explained in a CMU news release.

Powerful, metal-shelled robots may have a place in risky and industrial situations, but human environments call for a softer touch. In Disney's movie, robotics prodigy Tadashi Hamada makes the marshmallow-man-esque Baymax as a domestic helper, and his younger brother Hiro later adapts it to help defend the made-up city of San Fransokyo against — what else — an evil genius.

Soft robots versus metal monsters

"Their vision is very specific: You're going to be taken care of by a humanoid robot," said CMU robotics professor Chris Atkeson, whose lab Hall visited. "And you don't need a big honking metal monster to do that."

You want something with a better bedside manner — and one that isn't going to cause a bruise if it bumps into you. Atkeson's work focuses on "soft robots" that use unconventional materials and means of locomotion.

"Hard" robots may use gears and pistons to move their heavy limbs, but those created in Atkeson's lab can utilize things like air pressure or lightweight artificial muscles. Siddharth Sanan, now a postdoctoral fellow at Harvard's Wyss Institute, created the inflatable robotic limb that helped inspire Baymax's soft, gas-filled body.

Siddharth Sanan

A soft robotic arm created by Siddharth Sanan in CMU's soft robotics lab.

"The important thing is that there's some direction in which there is extreme compliance," he says, in describing what defines soft robotics. This extreme compliance means not only can a limb or body move smoothly and continuously along that axis, but it gives way when, for example, someone needs to get by or the robot inadvertently hits a table.

"There is totally a reason for using these in medical applications, because that's a place with lots of fragile objects, an environment you don't want to harm," said Sanan.

Flexible future

Baymax is still very much a creature of fiction: there are no full-scale humanoid soft robots yet, and some of the technology still needs to be worked out. Sanan couldn't see how a soft robot's limbs could be articulated, and Atkeson thought it should have smaller, more practical fingers rather than stubby sausages. But fudging a few technical details doesn't mean bouncy bots may not be in our future.

"When you're old, do you want to be taken care of by a giant spider?" asked Atkeson. "Technically a giant spider has a lot going for it. Four arms, four legs, it can do more, less chance of falling down. On the other hand, it's a giant spider. Old people today probably wouldn't go for the giant spider, but they would go for Baymax."

Soft, flexible robots are under investigation by roboticists around the world for use in rescue, care-taking, and other everyday tasks, and the merits of the field are becoming clearer as more intelligent machines inhabit our homes and lives. "Big Hero 6" may be a fantasy for kids today, but give it a few decades, and they might be buying a Baymax to help around the house.

As for future villains, they could do worse than an army of billions of self-assembling nanobots, the weapon wielded by Baymax and Hiro's masked antagonist — though we probably don't need to worry about those just yet.