Robotics

Smallest-ever remote-control walking robot uses shape-memory alloy

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These tiny crab robots can be remote controlled by using heat to deform shape-memory alloys
Northwestern University
These tiny crab robots can be remote controlled by using heat to deform shape-memory alloys
Northwestern University
At just half a millimeter wide, these crabs can move at a rate of half their body length per second
Northwestern University
The tiny critters are manufactured using a technique inspired by children's pop-up books
Northwestern University
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Researchers at Northwestern University in Illinois have demonstrated the world's smallest remote-controlled walking robot, at just half a millimeter wide. Such tiny machines can bend, twist, crawl, walk, turn and jump without hydraulics or electricity.

The robots are built using shape-memory alloy materials, which are then deformed into the desired shape. Heating these alloys up causes them to spring back to their original shape, and a thin coating of glass is able to elastically snap them back into their deformed shapes when the heat is removed.

The heat in this case was supplied by a scanning laser, which passed over the crabs to heat the alloy up. Because they're so tiny, the heat disperses extremely quickly, making them surprisingly responsive even at up to 10 cycles per second. The direction of the scanning laser determines the direction of movement – scan right, and the crabs walk right – simply due to the timing of the leg actuations. The team clocked them at an average speed of half their body length per second.

At just half a millimeter wide, these crabs can move at a rate of half their body length per second
Northwestern University

Then they tried some different geometries, including water-walking tripod structures that can be induced to turn by rotating the scanning laser, coiling structures capable of making small jumps, and others capable of twisting and other motions.

The manufacturing process is pretty fascinating – the team fabricated the robots as flat structures, this being their heated state. Then, they bonded the flat structures onto a stretched-out rubber substrate, but only at the foot points. Then the rubber was relaxed, shrinking the robots' footprint and causing them to pop up off the surface in a controlled buckling process that put them in their final, three-dimensional "cooled" positions, where the glass coating could be applied to hold them in shape until heated.

“Robotics is an exciting field of research, and the development of microscale robots is a fun topic for academic exploration,” said Materials Science and Engineering Professor John A. Rogers, who led the experimental work. “You might imagine micro-robots as agents to repair or assemble small structures or machines in industry or as surgical assistants to clear clogged arteries, to stop internal bleeding or to eliminate cancerous tumors — all in minimally invasive procedures.”

The tiny critters are manufactured using a technique inspired by children's pop-up books
Northwestern University

Of course, imagining them as such requires us to imagine how one might get targeted laser heating into the tiny spaces they're designed to operate in – a prospect that won't be simple within the body. So there's plenty of work to do yet.

Oh, and why crabs? “With these assembly techniques and materials concepts, we can build walking robots with almost any sizes or 3D shapes,” Rogers said. “But the students felt inspired and amused by the sideways crawling motions of tiny crabs. It was a creative whim.” Check out a video below.

The research is available in the journal Science Robotics.

Source: Northwestern University

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3 comments
Spud Murphy
Calling them robots is a bit of a stretch, they are just bits of stuff that respond to laser heating. Still cool to see them move...
vince
Smaller yet and some of those Hollywood movies won't be sci fi anymore.
SteveMc
Yup. Same thoughts as Spud, how is this a robot? Remember those 'fortune telling fish' you put on the palm of your hand and it curled up and flexed with the moisture being absorbed from your body? This is a more refined version of that fish. It's cool, very clever and possibly useful but hardly a robot as most of us perceive to be. However, I did look up 'Definition of a robot: A machine that resembles a living creature in being capable of moving independently (as by walking or rolling on wheels) and performing complex actions (such as grasping and moving objects)' is it a machine though?? 'Machine: a mechanically, electrically, or electronically operated device for performing a task'. OK, I'll give it to you :)