November 27, 2013
Amazing Viscoelasticity Observed In Structures Comprised Of Fire Ants
[ Watch the Video: Fire Ants Being Smashed by Petri Dish ]
redOrbit Staff & Wire Reports - Your Universe Online
Fire ants are capable of joining together to form a waterproof structure capable of bouncing back to its original shape when stretched or compressed, according to research presented Tuesday at the annual meeting of the American Physical Society's (APS) Division of Fluid Dynamics (DFD).
Researchers from the Georgia Institute of Technology explain that these ants can link their bodies together, forming waterproof rafts that behave much like an active material capable of changing state from a solid to a liquid. The ants can drip, spread and coagulate; and this transition helps them survive rainfall and crashing waves.
In a statement, the APS compares the structure’s behavior to Jell-O and toothpaste, stating that they are all “viscoelastic” materials capable of resisting flow under stress and reverting to their original shape like rubber bands. The fire ant rafts do not behave exactly like solids or liquids, but as a kind of hybrid of the two.
“The linkage structure they form, similar to a truss structure, is elastic and so is able to sustain external forces,” explained lead researcher Zhongyang Liu, an undergraduate student in the laboratory of Georgia Tech mechanical engineer and biologist David Hu. In short, the ants form these rafts by linking their legs and jaws to one-another, creating a structure that is constantly in flux.
“The ants repeatedly form, break, and reform their body-part connections,” the APS added. “Through these rearrangements, the researchers discovered, the raft is able to store energy (and thus acts as an elastic material) and dissipate energy (as a viscous material) to equivalent degrees – a situation that has not been seen in any other active materials, such as bacteria films or liquid crystals.”
Furthermore, Liu’s team found that rafts constructed out of deceased ants do not possess this quality. Rather, they behave more like solid viscoelastic materials. Liu called this the team’s “most important discovery.” He added that the swarm intelligence demonstrated by the ants to complete this task could be adapted to robotics research, and that the rafts they form could help spur new discoveries in the field of materials science.
Their presentation entitled “Ants cushion applied stress by active rearrangements” took place Tuesday afternoon at the conference, which is being held this year at the David L. Lawrence Convention Center in Pittsburgh, Pennsylvania.