ants compressed
Source: Georgia Tech

Collections of ants have a outstanding capability to alter shapes and duties based on the demands of their surroundings. When floodwaters hit, they self-assemble and make rafts to stay alive. They will also use their bodies to construct bridges and span gaps. What are the properties of those ant aggregations that enable for this wide selection of talents? New research from the Georgia Institute of Technology says it’s because the bugs are actually liquid-like and solid-like concurrently. The research is presently published in Nature Materials.

The Georgia Tech group probed the mechanical properties of fire ant aggregations by placing thousands of ants into a rheometer, a machine used to test the solid-like and liquid-like response of materials similar to food, hand cream or melted plastic.

The ants were sheared at constant speeds from about 0.0001 rpm up to about a hundred rpm. The researchers discovered that the conduct of live ants was much like that of dead ants: when the aggregation is pressured to stream, live ants let go and play dead. In this case, the viscosity dramatically decreased as the pace increased.

“It’s not unlike ketchup,” stated Alberto Fernandez-Nieves, an associate professor in the School of Physics. “The harder you squeeze, the easier it flows. However with ants, this occurs far more dramatically than with ketchup.”

Ants seem to have an on/off switch in that they let go for sufficiently massive applied forces,” mentioned David Hu, an associate professor in the George W. Woodruff School of Mechanical Engineering. “Regardless of wanting to be together, they let go and behave like a fluid to stop getting injured or killed.”

This identical conduct can be seen by dropping a penny through an ant aggregation. Ants will stream around the coin as it sinks by the aggregation. This flow takes a comparatively very long time to occur. Nevertheless, when the aggregation is poked rapidly, it responds like a spring and returns to its original form.

“That is the hallmark of viscoelastic behavior,” stated Fernandez-Nieves. “The ants exhibit a springy-response when probed at brief instances, however behave fluid-like at longer occasions.”

The group quantified this by observing the ants’ response to tiny wiggles of the rheometer. They discovered that the ants are equally liquid-like and solid-like. They did the identical experiment with dead ants and noticed that they are also solid-like. This confirmed that live ants are liquid-like and solid-like due to their activity.

“Remarkably, the observed behavior is comparable to what’s seen in materials that aren’t alive, like polymer gels right on the point after they become a gel,” stated Fernandez-Nieves. “That is quite puzzling, and we at the moment are performing many extra experiments to attempt to understand where these similarities come up from and how much they can be pushed. Doing this can hopefully extend our current mind-set about materials, that just like the ants, are active and thus out-of-equilibrium. There’s far more fascinating work we plan on doing with ants.”

Hu has studied ant habits for almost 10 years. Fernandez-Nieves is a physicist who makes use of rheology to understand the mechanics of soft materials and unravel the microscopic origin of their overall properties and behaviors.

Michael Tennenbaum, a graduate research assistant who participated in the research, also compared the conduct of the ant aggregation to jello.

“Think about when you wished to make the most jello possible out of a packet of gelatin. It will be solid, but additionally very liquidy,” he stated. “That’s because there would be just barely enough gelatin to make it solid-like however not enough to make it fully solid. The jello will be both solid-like and liquid-like.”

Hu has additionally used the liquid-like nature of the ants to study self-healing materials.

“In case you slice a dinner roll with a knife, you’re going to end up with two pieces of bread,” said Hu. “However when you slice through a pile of ants, they’ll merely let the knife go through, then reform on the opposite side. They’re like liquid metal – identical to that scene in the Terminator film.”

Hu says it’s this flexibility that permits ants to enjoy the best of both worlds. They are in a position to turn into solids to make things and liquids to avoid breaking into “smithereens.”

Watch the complete penny video down below:

The research, “Mechanics of Ant Aggregations,” was published in Nature Materials on October 26, 2015.



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