This Robot Has No Wheels, No Legs, and No Business Moving at All
Picture a blob about the size of your palm, made of rubbery silicone, sitting on a table. It looks like a deflated stress ball. Nothing about it suggests mobility, no wheels, no legs, no gears, no joints. Just a soft, rounded lump of stretchy material.
And then it moves.
This is the ChemBot, built by iRobot in collaboration with researchers at the University of Chicago and unveiled at the IEEE/RSJ International Conference on Intelligent Robots and Systems in October 2009. It travels entirely under its own power, in a chosen direction. How does something with no recognizable means of propulsion get from point A to point B?
Inflating a Skin Doesn’t Sound Like a Plan for Getting Around
The ChemBot inflates and deflates sections of its own outer surface to move, which, on first hearing, sounds like a description of what a balloon does, not a robot. Blow up a balloon and it gets bigger, but it does not roll across the room. So if inflation is your locomotion strategy, what exactly are you pushing, and where is it going?
“Jamming Skin Enabled Locomotion”, Which Is a Fancy Way of Saying It Rolls by Changing Shape
The outer skin is made from silicone rubber divided into independent cellular compartments, each filled with air and loosely packed particles. In that state, the particles shift freely, the way sand does when poured. Draw air out of a compartment and the pressure drops, the skin tightens, and the particles are forced together, they can no longer move past each other. The section goes from pliable to rigid almost instantly. That transition is particle jamming, the same principle that makes vacuum-packed coffee feel rigid in the bag.
Beneath those compartments sits an incompressible fluid and a variable-volume actuator. When specific compartments stiffen while others stay soft, the internal fluid is displaced in one direction, the robot’s mass shifts, and the body rolls forward. Change the sequence of which compartments inflate and which deflate, and you change the direction of travel. Squeeze one end of a toothpaste tube and the contents move toward the other end, the ChemBot does something conceptually similar, except the “tube” is a three-dimensional blob that can steer itself.
iRobot, a University Lab, and a Military Puzzle About Doors
iRobot is the company that put robotic vacuums on the map with the Roomba, first sold in September 2002. The ChemBot project was a long way from living room floors. Research also drew in teams at Harvard University and MIT, funded by DARPA and the U.S. Army Research Office, $3.3 million awarded on June 17, 2008.
The military rationale is concrete. A rigid robot cannot compress itself to fit through a gap smaller than its own frame. The stated DARPA goal was a soft, mobile robot that could navigate openings smaller than its own structural dimensions. Some journalists speculated about surveillance applications, but DARPA’s own language centered on access to denied or hostile spaces.
What We Don’t Know Is Almost as Interesting as What We Do
When the ChemBot appeared in October 2009, researchers described it as the first working demonstration of a completely soft, mobile robot using jamming as an enabling technology. The physics hold up, the robot moves, and the principle works in practice. The debut left plenty of questions open: speed data, precise dimensions beyond “palm-sized,” and any timeline for deployment were all absent from the initial presentation.
The most compelling open question was also the most obvious: how small an opening can it actually squeeze through, and how quickly? A follow-on prototype from iRobot, MIT, and Harvard appeared in 2010, pushing the concept further. But the original ChemBot’s contribution was simpler and arguably more important, it showed that “soft” and “mobile” can exist in the same machine, with no rigid part required.