Did you know fire ants can form masses with their own bodies to float in water? Some would consider this a fun fact. Others would be understandably horrified. But students at the engineering school of the Georgia Institute of Technology found inspiration. They have been studying this biological marvel, interested in how their discoveries could be applied to their field.
More on Fire Ants
Fire ants are plentiful in Georgia, and they are also an invasive species in tropical environments around the world. Their origins in the Amazon Rainforest account for this success, as the Vox video explains. Like most ants, they dig their colonies underground. However, living in tunnels connected to holes at ground level comes is tricky when rain constantly pours on the ground. So these crafty insects developed an incredible skill: they can lock legs until they form a mass so tight that water can’t penetrate it. They arrange themselves in such a way that the colony can essentially ride themselves to land without a drowning death.
This fascinated Dr. David Hu, associate professor at the George W. Woodruff School of Mechanical Engineering. He’s an engineer with a strong interest in biology, as his biography on GT’s About page indicates. Hu believes that before robots can do anything we see in science fiction, “we will need a fundamental physical understanding of how related tasks are accomplished in their biological counterparts.” And seeing that fire ants and human engineers both build towers and rafts, maybe he even feels some kinship.
And so, Dr. Hu and his students put the ants through intense experiments. Vox starts their video by describing a colony surviving after being placed in a bucket that slowly filled with water. Dr. Hu also mentioned feeding them iodine (“which is radioactive”), “flash-freezing them with liquid nitrogen,” tying them together with elastic bands, and even “coat[ing] them in gold.” He giggled, then added, “But that’s just standard.”
Conclusions So Far
The engineers explored the perspective that fire ants could be considered a “material.” This isn’t a prelude to mad science experiments for making furniture and buildings out of them. It’s just to see how they work. And their studies are working. The team created mathematical equations describing ant behavior.
Incredibly, according to the team, fire ant chains are “a viscoelastic material.” This means they have properties of both a solid and a liquid. Their links break “when the stress is more than 2-3 times the weight of an ant.” At that point, connections between individuals loosen, like the hydrogen bonds in water. This means when poured into water they can not only float, but spread out “like a dye.” They can also “flow” from one container to another.” This viscoelastic label sounds bizarre, but Dr. Hu’s an expert on the mechanics of fluids and solids. It’s safe to assume he knows what he’s talking about.
The team is already thinking of how this knowledge can be used in engineering projects. They have observed that when they form these balls and towers, no single ant is directing the movement. This swarm behavior could be used when designing and programming robots so individuals can work in large groups. It’s incredible that even sci-fi technology can have their origin in evolutionary practices developed by some of nature’s oldest and hardiest survivors.
Want an unpleasant reminder of how gross insects can be? Here’s an article about the bedbug infestation from hell.