Though ants have long been known to carry loads many times their own weight, a new study has cast light on the extent of this strength and the mechanics responsible for it. Research conducted by a team from The Ohio State University suggests an ant can lift 5,000 times its own body weight, with its neck bearing most of the load, providing a potential blueprint for the development of much stronger robots.
The research involved studying the composition and strength of the Allegheny mound ant, an insect commonly found in the east of the United States. To determine the strength of the ant, the team conducted an experiment specifically designed to measure how much pressure its neck could endure.
After first refrigerating the ants to anesthetize them, the team placed the insects inside a centrifuge, much like the one used in the "Rotor Ride" commonly seen at carnivals. This essentially is a round room that spins at an increasing speed until the centrifugal force presses those inside against the wall, at which point the floor drops away.
Following the same principle, the ants were pulled towards the wall of the centrifuge as the speed of the rotation was increased, though one thing was holding them back: the gluing of their heads to the floor.
By pitching the growing outward force against the strength of the ant's neck, the team were able to quantify the amount of pressure it could withstand relative to its own weight. They observed the neck joint and body begin to stretch at a force equal to 350 times the weight of the ant. It was only at a force of 3,400-5,000 times its weight that the body actually detached from the head.
The researchers also used Micro-CT machines to produce scans of the ants, highlighting a soft-tissue structure of the neck and the hard exoskeleton of its head and body. Contrasting and conjoining materials such as these commonly result in a concentration of stress, though the researchers say that the ants have a "graded and gradual transition" between the two, an attribute which enhances performance and could therefore be mimicked in a man-made design.
This opens up possibilities for the development of micro-sized robots, where systems made up of soft and hard components, like an ant's body, could offer increased strength and durability.
“Other insects have similar micro-scale structures, and we think that they might play some kind of mechanical role,” said Carlos Castro, Assistant Professor of Mechanical and Aerospace Engineering at The Ohio State University. “They might regulate the way that the soft tissue and hard exoskeleton come together, to minimize stress and optimize mechanical function. They might create friction, or brace one moving part against the other.”
The team also used electron microscopy images to observe the joint and the adjoining surfaces of the head, neck and chest at the joint. These revealed different textures on each surface and also what appeared to be bump or hair-like structures rooted in different locations, characteristics the team believes may also play into the incredible strength of the insect.
The researchers are looking at ways to adapt the attributes of the ant to larger-scale robotics, though it won't be without complications as the strength of the ant is largely tied to its small body weight. Increasing an ant to the same scale of a human for example, would increase its volume as a three-dimensional object, while the strength of its muscles would only increase by their two-dimensional surface area, effectively diminishing its favorable bulk-to-brawn ratio.
Though applications of robots based on this design would be limited on land, Castro says it could prove a useful model for developing robots for space, designed to tow cargo in microgravity.
The team's findings were recently published in the Journal of Biomechanics.
Source: The Ohio State University