Smaller than a flea, a single crab robot stands on the edge of a coin.

‘Smallest-ever’ robots are remote controlled using lasers

Image credit: Northwestern University

The “smallest-ever” remote-controlled walking robot, which comes in the form of a tiny, peekytoe crab, has been unveiled by researchers from Northwestern University, Illinois.

The tiny crabs may just be half a millimetre wide, but they are capable of bending, twisting, crawling, walking, turning and even jumping. The team also developed millimetre-sized robots resembling inchworms, crickets and beetles.

Although the research is exploratory at this point, the researchers believe their technology might bring the field closer to realizing micro-sized robots that can perform practical tasks inside tightly confined spaces.

“Robotics is an exciting field of research, and the development of microscale robots is a fun topic for academic exploration,” said John A Rogers, who led the experimental work.

 Smaller than a flea, a single crab robot stands on the edge of a coin.

Image credit: Northwestern University

“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 tumours — all in minimally invasive procedures.”

“Our technology enables a variety of controlled motion modalities and can walk with an average speed of half its body length per second,” added Yonggang Huang, who led the theoretical work. “This is very challenging to achieve at such small scales for terrestrial robots.”

Smaller than a flea, the crab is not powered by complex hardware, hydraulics or electricity. Instead, its power lies within the elastic resilience of its body.

To construct the robot, the researchers used a shape-memory alloy material that transforms to its “remembered” shape when heated. In this case, the researchers used a scanned laser beam to rapidly heat the robot at different targeted locations across its body. A thin coating of glass elastically returns that corresponding part of structure to its deformed shape upon cooling.

As the robot changes from one phase to another — deformed to remembered shape and back again — it creates locomotion. Not only does the laser remotely control the robot to activate it, the laser scanning direction also determines the robot’s walking direction. Scanning from left to right, for example, causes the robot to move from right to left.

“Because these structures are so tiny, the rate of cooling is very fast,” Rogers explained. “In fact, reducing the sizes of these robots allows them to run faster.”

To manufacture the crab, the team fabricated precursors to the walking crab structures in flat, planar geometries.

Then, they bonded these precursors onto a slightly stretched rubber substrate. When the stretched substrate is relaxed, a controlled buckling process occurs that causes the crab to “pop up” into precisely defined three-dimensional forms.

With this manufacturing method, the team believes they could develop robots of various shapes and sizes.

“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.”

On Monday, another team unveiled soft robots that are capable of navigating complex environments such as mazes, without any input from humans or computer software.

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