University of California, Berkeley

It doesn't take a genius to guess what would happen if something 900 times your own body weight landed on you -- you'd be crushed. If you're a human, that is. If you were a cockroach, on the other hand, you'd not only survive the pressure but also be able run at high speed.

That's according to a new study from the University of California, Berkeley. They set out to investigate how the Peroplaneta americana -- or the American cockroach -- is able to squeeze into tiny nooks and crannies so quickly. To do so, they built a palm-sized robot to replicate the behaviour and biology of a cockroach.


The team found that not only could it fit into holes one-tenth of an inch small, they could also run at incredibly high speeds -- even when they're flattened in half. "What's impressive about these cockroaches is that they can run as fast through a quarter-inch gap as a half-inch gap by reorienting their legs completely out to the side," said Kaushik Jayaram, who lead the study. "They're about half an inch tall when they run freely, but can squish their bodies to one-tenth of an inch -- the height of two stacked pennies."

The compressible robot with articulated mechanisms, or Cram, was able to splay its legs outwards when squashed and was protected by a plastic shield modelled on the tough wings that cover a cockroach's body. The robot was then filmed, using a high-speed camera, running between plates only a quarter inch apart. When the plates were narrowed, the robot was able to continue at high speed through a space only one-tenth of an inch small.

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Because they can't use their feet properly in such small spaces, the cockroaches use sensory spines on their tibia to push against the floor and propel themselves. "They have to use different body parts to move in these spaces, because their legs and feet are not oriented to work properly," Jayaram said. "But they are still capable of generating the large forces necessary for locomotion."

There were some limitations, however -- the cockroaches found it hard to move through crevices that were fitted with sandpaper as it hindered the friction-based propulsion of the sensory spines.

The team, who detailed their work in Proceedings of the National Academy of Sciences, hope that the robot could be used in search and rescue missions after earthquakes or other natural disasters. The team built the robot using a technique resembling origami, though a "more robust method" will be needed for real-life application. "In the event of an earthquake, first responders need to know if an area of rubble is stable and safe, but the challenge is that most robots can't get into the rubble," said Robert Full, who also worked on the project. "But if there are lots of cracks and vents and conduits, you can imagine just throwing a swarm of these robots in to locate survivors and safe entry points for first responders." "This is only a prototype, but it shows the feasibility of a new direction using what we think are the most effective models for soft robots, that is, animals with exoskeletons," he said. "Insects are the most successful animals on earth. Because they intrude nearly everywhere, we should look to them for inspiration as to how to make a robot that can do the same."