Ants bridge gap between nature and robotics

The structures form in seconds and are deconstructed just as fast (Dr Christopher Reid)
The structures form in seconds and are deconstructed just as fast (Dr Christopher Reid)

The extraordinary teamwork of army ants to build living and moving bridges to cross gaps could be used to build swarm robots to help in disaster relief, researchers say.

International researchers have found the bridges the ants build create shortcuts along the rainforest floor, and can move and change position to cover larger gaps if needed.

The insects, native to Central and South America, create the structures by linking their bodies. The study’s co-lead author Dr Christopher Reid, a postdoctoral researcher at the Insect Behaviour and Ecology Lab at the University of Sydney, says they undergo a "cost-benefit trade-off" about how long the bridge should be.

The study, published in Proceedings of the National Academy of Sciences today, shows how the bridges stop moving once they get so long the cost of adding more workers outweighs the benefit of shortening their path.

It says the fluid and organic structure of the bridges helps colonies of up to a million individuals travel at maximum speed and across unchartered and potentially difficult territory.

The bridges dismantle once the ants making the structure sense the traffic walking over them slows down below a critical threshold.

Structures can be built and deconstructed in seconds and, contrary to previous assumptions, are reactive to their environment rather than static.

"Indeed, after starting at intersections between twigs or lianas travelled by the ants, the bridges slowly move away from their starting point, creating shortcuts and progressively lengthening by addition of new workers, before stopping, suspended in mid-air," Dr Reid says.

"In many cases, the ants could have created better shortcuts, but instead they ceased moving their bridges before achieving the shortest route possible."

The research team, which included people from the Max Planck Institute for Ornithology in Germany, University of Konstanz, New Jersey Institute of Technology, Princeton University and George Washington University, found the ants benefitted from creating shortcuts but the cost is taking ants away from other important tasks.

The ants need to build bridges because of their nomadic nature, as they're constantly moving the colony through the rainforests.

And it seems nature could inspire a new wave of robotics, including self-assembling systems such as reconfigurable materials and autonomous robotic swarms, Dr Reid says.

"Such swarms could accomplish remarkable tasks, such as creating bridges to navigate complex terrain, plugs to repair structural breaches, or supports to stabilise a failing structure.

"These systems could also enable robots to operate in complex unpredictable settings, such as in natural disaster areas, where human presence is dangerous or problematic," he says.

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