Man does not cease to be inspired by nature. A new example of this is… cockroaches. Deeply hated by most humans, these insects possess a mobile exoskeleton, allowing them to move through tiny spaces and withstand forces of nearly 900 times their body weight without injury. A marvel that could be the key to building robots to search and rescue victims from the rubble.
To the dismay of pest control professionals and their clients alike, cockroaches’ ability to adapt to survive seems limitless.
They resist insecticides, develop their taste buds to avoid glucose traps, or flee in unforeseen and random directions to avoid being overtaken by predators. To this list of abilities must be added the results obtained in a study carried out at the University of California at Berkeley (USA), which analyzes the extraordinary capacity of cockroaches to compress and resist the pressure on their bodies.
Cockroaches’ jointed exoskeletons allow for rapid locomotion while retaining the ability of a soft body shape-shifting ability to explore confined environments. In the experiments carried out, the researchers put these physical characteristics of cockroaches to the test, with surprising results.
By making them pass through horizontal crevices, with a height of less than a quarter of the height of the body of the standing insect, they quickly crossed them in 300-800 milliseconds, compressing its body by 40-60%.
The recording of the experiment reveals that the passage through the slit is a complex and discontinuous maneuver. After traversing the horizontal cracks and entering a confined vertical space, the cockroaches crawled at speeds close to 60 cm⋅s-1 (20 times their body length per second), despite body compression and postural changes.
Running speed and stride length and period were reduced only at the lowest slit height (4 mm), while body glide or “drag” and zigzag displacement were increased.
To analyze the performance limits of running in confined spaces, the researchers altered the friction on the ceiling and floor of the crevice. An increase in ceiling friction slowed the insect by decreasing stride length and increasing the gliding or “crawling” of the insect. Instead, an increase in ground friction contributed to speed and stride length, peaking at intermediate levels of friction.
These data support a model of locomotion that the researchers described as “crawling with legs, with body friction.”
Furthermore, to define the body compression limits of cockroaches in confined spaces, they performed cyclic dynamic compression tests on live animals. The insects’ exoskeleton allowed them to withstand forces of 300 times their body weight through the smallest of cracks, and up to nearly 900 times their body weight without injury.
It is not surprising, then, that the flexible and resistant exoskeletons of cockroaches and their way of moving in confined spaces can serve as inspiration for designing search and rescue robots capable of penetrating the debris generated by tornadoes, earthquakes or explosions.
Source: Kaushik Jayaram, Robert J. Full: Cockroaches Crawl Crevices, Crawl Quickly in Confined Spaces, and Inspire a Soft, Legged Robot, University of California, Berkeley, 2015