The 0.5 mm crab, the world’s smallest remote-controlled robot

The 0.5 mm crab, the world's smallest remote-controlled robot

Smaller than a microchip, the small crab robot designed by a team of researchers at Northwestern University still has amazing capabilities for its size. Able to walk, turn and even jump, this is a new step towards robotic miniaturization.

It is, according to its designers, the smallest remote-controlled walking robot ever created. Scientists have chosen to design it as a small crab, only half a millimeter wide.

Tiny robotic crabs, only 0.5 millimeters long, can walk and even jump. Photo: Northwestern University

Despite its size, it is capable of true accomplishments, as it can be made to bend, crawl, walk, turn, and even jump. Their progress on this topic was published on May 25, 2022, in the journal Science Robotics.

The robot has a purely research purpose, but according to its designers, it is an open door for multiple uses due to its very small size, which could allow it to perform actions in confined spaces.

“Robotics is an interesting field of research, and the development of microscopic robots is a fun subject for academic exploration. You could imagine microbots acting as agents to repair or assemble small structures or machines in the industry or as surgical assistants to clean clogged arteries, stop internal bleeding, or remove cancerous tumors – all in minimally invasive procedures. ” , says John A. Rogers, who led the experimental activity, in a university press release.

The crab in question is capable of moving at an average speed of half its length per second. It is a significant achievement, although, given the scale, it is only a quarter of a millimeter per second.

The researchers did not use complex electronic or hydraulic structures to design the robot. The principle of operation that allows it to work is very simple in theory: it is based entirely on the principles of elasticity and resilience in the very structure of the robot’s body.

In fact, its structure was designed in a shape memory alloy. This alloy has a “stored” shape, to which it invariably returns whenever heated.

When it cools, a thin layer of glass restores the previously heated part to a deformed state by elasticity.

A design method inspired by a pop-up book

In the case of one of the crab’s legs, for example, this means that it has two positions, which can be alternated by its successive heating and cooling. This is what it takes to gain the ability to walk.

To do this, scientists use laser beams that allow them to heat the targeted areas of the robot’s body very quickly. Depending on the movements of the laser, it is possible to control the direction of the crab robot, according to Science Robotics.

We can imagine that this takes time, but in reality, “because these structures are very small, the cooling rate is very fast,” explains John Rogers. In fact, reducing the size of these robots allows them to run faster.

The crab robot is so small that it fits on the edge of a coin.  Northwestern University
The crab robot is so small that it takes place on the edge of a coin. Photo: Northwestern University

The assembly method used to create such a small structure is inspired by children’s pop-up books (which contain 3D shapes between pages), which researchers have been studying for a long time.

The crab was designed entirely flat, using geometric shapes. This flat structure was then glued to a lightly stretched rubber substrate.

When the rubber is released, the crab takes on its three-dimensional shape. This method allows the realization of all kinds of shapes, and the researchers actually created crickets, beetles and caterpillars.

The reason why they chose a small crab for the presented prototype is very simple:

“With these assembly techniques and material concepts, we can build walking robots with almost any size or 3D shape, but the students were inspired and amused by the side movements of the little crabs. It was a creative whim, “says Rogers.

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