Engineers Develop Smallest-Ever Remote-Controlled Walking Robot

A team of engineers at Northwestern University have developed the smallest-ever remote-controlled walking robot, which is in the form of a tiny crab. 

The tiny crab robots are only a half-millimeter wide, making them smaller than a flea. They can bend, twist, walk, crawl, turn, and jump. Besides the tiny crab, the researchers also developed millimeter-sized robots that resemble crickets, beetles, and inchworms. 

Achieving Micro-Sized Robots

According to the team, these new types of robots could bring us closer to achieving micro-sized robots that can operate in tightly confined spaces.

The research was published in the journal Science Robotics.

John A. Rogers led the experimental work. He is the Louis Simpson and Kimberly Querrey Professor of Materials Science and Engineering, Biomedical Engineering and Neurological Surgery at Northwestern’s McCormick School of Engineering and Feinberg School of Medicine. He is also the director of the Querrey Simpson Institute for Bioelectronics (QSIB). 

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

Yonggang Huang led the theoretical work. He is the Jan and Marcia Achenback Professor of Mechanical Engineering and Civil and Environmental Engineering at McCormick and a key member of QSIB.

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

Constructing the Tiny Crab

The crab does not have to rely on complex hardware, hydraulics, or electricity like many other robots. It draws its power from the elastic resilience of its body. The researchers constructed the robot by using a shape-memory alloy material that transforms to a “remembered” shape when heated. In order to rapidly heat the robot, the team used a scanned laser beam and targeted different locations across the robot’s body. Once it cools, a thin coating of glass elastically returns the corresponding part of the structure to its deformed shape. 

By changing from one phase to another, the robot can create locomotion. By aiming the laser in different directions, the team can control where the robot walks. To move left to right, the team just has to scan 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 achieve such a tiny state for the robot, the team first fabricated precursors to the walking crab structures in flat, planar geometries. They then bonded the precursors onto a slightly stretched rubber substrate. By relaxing the substrate, a controlled buckling process happens and causes the crab to “pop up” into defined three-dimenisional forms. 

“With these assembly techniques and materials 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 motions of tiny crabs. It was a creative whim.”