The Smallest ever walking robot

Northwestern University researchers have created the world’s tiniest remote-controlled walking robot, which takes the form of a tiny, charming peekytoe crab.

The tiny crabs, which are only a half-millimeter across, can bend, twist, crawl, walk, turn, and even jump. In addition, the researchers created millimeter-sized robots that resemble inchworms, crickets, and beetles. Although the research is still in its early stages, the researchers hope their technique will move the field closer to developing micro-sized robots capable of doing practical jobs inside small places.

“Robotics is an interesting field of research, and the development of microscale robots is a delightful topic for academic exploration,” stated experiment leader John A. Rogers. “Imagine micro-robots as agents in the industry to repair or assemble small structures or machinery, or as surgical helpers to clear blocked arteries, halt internal bleeding, or eradicate malignant tumors – all in minimally invasive operations.”

“Our technology offers a range of controlled motion modalities and can walk at half its body length per second on average,” Yonggang Huang, who lead the theoretical study, noted. “Achieving this at such tiny sizes for terrestrial robots is extremely difficult.”

The crab, which is the size of a flea, is powered by simple hardware, hydraulics, and electricity. Instead, its strength is generated from its body’s elastic flexibility. The robot was built with a shape-memory alloy material that changes to its “remembered” shape when heated. In this situation, the researchers used a scanning laser beam to fast heat the robot at numerous particular locations across its body. When cooled, a thin coating of glass returns the structure’s bent part to its original shape.

The robot moves as it transitions from one phase to the next, from distorted to memorized shape and back again. The laser not only remotely controls the robot to activate it, but also sets the robot’s walking orientation. For example, scanning from left to right leads the robot to move from right to left.

“The pace of cooling is quite quick because these structures are so small,” Rogers stated. “In reality, shrinking these robots allows them to run faster.”

To create such a tiny creature, Rogers and Huang used a technique they developed eight years ago: a pop-up construction process inspired by a child’s pop-up book.

First, the team created flat, planar precursors to the walking crab constructs. The precursors were then attached to a somewhat stretched rubber substrate. When the stretched substrate is relaxed, the crab “pops up” into precisely specified three-dimensional structures due to a controlled buckling process.

The Northwestern team could create robots of all forms and sizes using this manufacturing approach. So, what’s the point of a peekytoe crab? That is thanks to Rogers and Huang’s students.