Imagine a tsunami hits, your neighborhood is flooded and you must link arms and legs with your neighbors to stay connected and afloat. It would be difficult, right? Not for fire ants. They easily form jumbled, tight groups of a thousand or so when the rains come and flood their anthills. Researchers at Georgia Institute of Technology have been cracking away at these "ant rafts" to understand how the ants connect so quickly and efficiently in the face of natural danger.
The ants come together and form a structure comprised of legs and air pockets. The air pockets, formed by the ants pushing away at their neighbors, help keep the raft afloat. No ant is left behind.
"They're literally building a new type of material with special properties, because of the way they connect up," says David Hu, one of the researchers trying to understand the mechanism behind the phenomenon.
The difficulty of unraveling this balled up mystery lies in accessibility. Paul Foster, the lead author of this study published in The Journal of Experimental Biology on June 15, says that peering into the mess of ants is not sufficient to see into the many layers of connections. Foster and his team froze the ants with liquid nitrogen and put them through a micro-scale computed tomography (CT) scan to understand the masterful 3D structure.
The results were both revealing and inspiring. The ants laboriously orient themselves perpendicular to each other to maximize space and accommodate different sized ants. This arrangement also allows the structure to expand and contract when necessary.
After many scans, the scientists discovered that the ants connect to their neighbors via small sticky pads on their legs. One ant shares an average of 14 connections with its neighbors. 99% of ants connect with their neighbors, so no ant takes advantage of the others.
This structure sounds incredibly complicated, yet the fire ants react immediately and form the structure in a matter of seconds. Foster, Hu, and their team discovered this by scooping up about a hundred ants, putting them in a cup, and stirring them around. Despite the lack of water, the ants formed a structure somewhere between a raft-shape and a ball, much faster than expected.
Returning to the (hopefully) hypothetical tsunami situation, imagine that we could arrange ourselves into secure, buoyant patterns. Alternatively, imagine that robots could be designed to spontaneously form structures such as rafts or bridges in the face of natural disasters. Researchers at Harvard believe the fire ant rafts pose some clever ideas for self-structuring materials that could, one day, provide protection and save lives.
