Future robots to mimic ant's weight-lifting ability

How much weight do you think that ubiquitous little creature can lift? Scientists were astounded to find that ants can lift up to 5,000 times their body weight.

The real secret to the ant's extraordinary strength may lie in its tiny neck joint, say researchers who report that the neck joint of a common American field ant can withstand pressures up to 5,000 times her weight.

"Ants are impressive mechanical systems - astounding, really," said Carlos Castro, assistant professor of mechanical and aerospace engineering at Ohio State University (OSU).

"Before we started, we made a somewhat conservative estimate that they might withstand 1,000 times their weight, and it turned out to be much more," Castro added.

The engineers are studying whether similar joints might enable future robots to mimic the ant's weight-lifting ability on earth and in space.

Previous researchers have long observed ants in the field and guessed that they could hoist a hundred times their body weight or more, judging by the payload of leaves or prey that they carried.

Castro and his colleagues took a different approach. They took the ants apart.

"As you would in any engineering system, if you want to understand how something works, you take it apart," he said.

The engineers examined the 'Allegheny mound' ant as if it were a device that they wanted to reverse-engineer: they tested its moving parts and the materials it is made of.

They imaged ants with electron microscopy and X-rayed them with micro-computed tomography machines.

They then glued them face-down in a specially designed centrifuge to measure the force necessary to deform the neck and eventually rupture the head from the body.

The centrifuge spun up to hundreds of rotations per second, each increase in speed exerting more outward force on the ant.

At forces corresponding to 350 times the ants' body weight, the neck joint began to stretch and the body lengthened.

The ants' necks ruptured at forces of 3,400-5,000 times their average body weight.

"Now that we understand the limits of what this particular ant can withstand, we want to understand how it moves or how does it hold its head," added Castro.

One day, this research could lead to micro-sized robots that combine soft and hard parts, as the ant's body does, added the findings published in Journal of Biomechanics.