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‘Robo-crab’ smaller than a flea is world’s smallest remote-controlled robot

They could be used as surgical assistants to clear clogged arteries, stop internal bleeding or to eliminate cancerous tumors.

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By Stephen Beech via SWNS

A robotic crab tinier than a flea has become the smallest-ever remote-controlled robot.

Just a half-millimeter wide, it can walk, bend, twist, turn and even jump.

A magnified view of the tiny crab robot, standing on the edge of a coin. (Northwestern University via SWNS)

The remarkable, record-breaking micro machine was developed by engineers at Northwestern University in Illinois, and comes in the form of a tiny peekytoe crab.

The same team also developed millimeter-sized robots resembling inchworms, crickets and beetles.

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

The same team produced a winged microchip last year that was the smallest-ever human-made flying structure.

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

“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.”

Professor Yonggang Huang, who led the theoretical work, said: "Our technology enables a variety of controlled motion modalities and can walk with an average speed of half its body length per second.

“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, Prof Rogers explained that its power lies within the elastic resilience of its body.

To build the mini machine, 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.

Prof Rogers said that as the robot changes from one phase to another - deformed to remembered shape and back again - it creates locomotion.

He explained that 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.

Robo-crab on a coin (Northwestern University via SWNS)

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

To manufacture such a tiny machine, Prof Rogers and Prof Huang turned to a technique they introduced eight years ago - a pop-up assembly method inspired by a child’s pop-up book.

The team began by fabricating precursors to the walking crab structures in flat, planar geometries. Then, they bonded the 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.

The manufacturing method would allow the team to develop robots of various shapes and sizes, but the crab was down to the students.

Prof Rogers added: “With these assembly techniques and materials concepts, we can build walking robots with almost any sizes or 3D shapes.

“But the students felt inspired and amused by the sideways crawling motions of tiny crabs. It was a creative whim.”

The findings were published in the journal Science Robotics.

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