This little crab robot is the smallest remote-controlled crawling robot ever created

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Illustration of robot crab on a piece for scale. Credit: Northwestern University.

Don’t panic or anything, but there are thousands of mites living on the surface of your body, most of which actually live on your face. It’s just that they’re so small you can’t see them with the naked eye. The smaller ones are around 0.1mm, while the larger ones are around 6mm. And don’t worry, they are completely harmless.

I write this just to preface the extraordinary nature of the latest robot out of Northwestern University. After showcasing the world’s smallest man-made structure last year – essentially a microchip with wings smaller than a grain of sand – engineers at North West have once again outdone themselves by creating a crab-like walking robot that is only half a millimeter wide, almost the size of a dust mite.

The tiny crawling robot is remotely controlled by a laser, making it the smallest remote-controlled walking robot ever created. He can bend, twist, crawl, walk, turn and even jump. This proof-of-concept can pave the way for more practical micro- and nano-sized robots that perform a number of useful tasks, from administering drugs to monitoring the environment inside tightly confined spaces – and which may also include the human body.

“Robotics is an exciting field of research, and the development of micro-scale robots is a fun topic for academic exploration,” said Professor John A. Rogers, who led the experimental work. “You could imagine micro-robots as agents for repairing or assembling small structures or machinery in industry or as surgical assistants for clearing clogged arteries, stopping internal bleeding, or removing cancerous tumors – all in minimally invasive procedures.

The tiny insects and arthropods are very complex despite their size, having a nervous system that controls highly articulated limbs or wings. The researchers are not there yet with the miniaturization of the material, but their compromise remains very clever.

Rather than using all sorts of electronics, hydraulics and other complex hardware, the researchers built their robot crab using an assembly technique inspired by children’s pop-up books. The structure of the walking crab started from very simple planar and flat geometries, which were bound together by a rubber substrate. In its relaxed state, the different geometries curl up, causing the robot’s structure to “pop up” into a three-dimensional, crab-like shape.

The Crab is made from a shape-memory alloy, which does exactly what its name suggests – the springy alloy assumes its “memorized” shape when environmental conditions return to normal. For example, when the researchers pointed a laser beam at the robot, the elastic material deformed. But after cooling, the material returned to its basic state, reshaping the robot.

These alternating phases result in locomotion. Scanning the robot from left to right causes it to move from right to left.

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

But why design a robot crab in the first place?

“With these assembly techniques and material concepts, we can build walking robots with almost any size or 3D shape,” Rogers said. “But the students felt inspired and amused by the sideways crawling movements of the little crabs. It was a creative quirk.

The results are published in the journal Scientific robotics.

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